Global fish production and climate change

Leveraging detection uncertainty to estimate Renibacterium salmoninarum infection status among multiple tissues and assays

Effective disease surveillance relies on accurate pathogen testing and robust prevalence estimates. Diagnostic specificity (DSp), the probability that an uninfected animal tests negative, is high when false positives are low. Diagnostic sensitivity (DSe) is the probability an infected animal tests positive; higher DSe means fewer false negatives. However, sensitivity and false negatives are harder to estimate without a "gold standard", an assay that can detect between 90 - 100% of true positive infections. Occupancy estimation of infection prevalence offers one solution by allowing for imperfect detection of the pathogen. Testing potentially infected tissues multiple times allows for the use of a Bayesian multistate occupancy model to estimate the probability of pathogen infection in tissues [Formula: see text] and detection probabilities [Formula: see text] for different assays. Using [Formula: see text] and [Formula: see text] from the posterior distribution, the conditional probability of detecting the pathogen can be modeled, allowing for the calculation of DSe. Renibacterium salmoninarum is a bacterial pathogen causing bacterial kidney disease among salmonid species and was the model pathogen we used to train our model. The current testing standard for salmonids combines initial screening for antibodies using direct fluorescent antibody test (DFAT) with polymerase chain reaction (PCR) confirmation to detect R. salmoninarum. However, detection of R. salmoninarum still varies between species, tissues, and assays. Here, a multi-state occupancy model was used to estimate detection probability among individual and dual kidney/liver infections with DFAT and qPCR in fish with an unknown infection status. Both assays produced false negatives, but qPCR had fewer than DFAT and a higher DSe. Infection state was often misclassified, but multiple surveys per individual or combining tissues for testing improved DSe for both assays.

Exposure of larval pinto abalone to ocean acidification and warming negatively impacts survival, settlement, and size

Pinto abalone (Haliotis kamtschatkana), the only abalone species native to Washington, declined by 97% in the state from 1992 to 2017. Their decline is a loss for indigenous tribes, recreational divers, and the health of subtidal rocky reefs and kelp beds. Current restoration actions are facing threats of ocean acidification and warming in the northeast Pacific. This research aims to deepen our understanding of the tolerance and physiological flexibility of early life history stages of pinto abalone and inform hatchery practices under future climate change scenarios. We conducted an experiment to test how seawater pH and temperature stress impact abalone larvae. We exposed abalone post-fertilization to elevated temperature and reduced seawater pH for ten days spanning their larval development period: (1) 7.95pH/14°C (ambient), (2) 7.60pH/14°C, (3) 7.95pH/18°C, and (4) 7.60pH/18°C. Abalone in the ambient treatment had the best survival, those in the 7.60pH/18°C treatment had the worst survival, and those in the two single-stressor treatments had survival in between. Among the surviving larvae, pH was the dominant stressor influencing settlement success, with higher settlement rates under ambient pH treatments at both temperatures. pH also had a stronger effect than temperature on shell length. The information gleaned from this study is essential for optimizing future restoration aquaculture for pinto abalone and determining their ideal habitat and potential geographic range.

What can go wrong for future Senegalese sole recruitment? Temperature and food availability as important drivers of early-life-history traits

Water temperature and prey availability are key factors influencing the successful recruitment of early life stages in fish. Understanding how these variables modulate larval growth and survival is essential for modelling larval dynamics. In this study we reared S. senegalensis larvae under controlled laboratory conditions to assess the effects of temperature and feeding frequency on larval development. Three temperatures (17, 20, and 23 °C) and three feeding frequencies (Ff 2.5 fed 2.5 times per week, Ff 4 four times per week, and Ff 6 six times per week) were tested from 12 to 32 days post-hatch (dph) in both individual and group housing systems. Survival, growth, and metamorphosis progress were monitored, and the expression of six genes related to nutrition (tryp1a and apoA4Aa2), cellular stress (hsp90aa and hsp70), endocrine regulation (tgb), and muscle development (myf4) were monitored on S3 and S4 metamorphic larvae. The feeding frequency appeared as the primary driver influencing all investigated traits, while temperature played a less pronounced effect. These data demonstrate the critical role of energy provision in regulating growth, development, and survival, which interacts with temperature, particularly under conditions where metabolic and energy demands cannot be fully fulfilled. Additionally, the Senegalese sole larvae exhibited compensatory genomic adaptive responses to efficiently mobilize nutrients from the gut and adjust the thyroid axis and cellular responses to support metamorphosis transformation and metabolism when food availability was limited or when temperature approached physiological thresholds.

Integrating temperature-dependent production of environmental DNA into its relationship with organism abundance

Despite a consensus on the correlative relationship between environmental DNA (eDNA) concentration and organism abundance, precise and reliable abundance estimation using eDNA analysis is in its infancy. Previous studies suggested that water temperature could drive both eDNA degradation and production, but it remains unclarified how the eDNA-abundance relationship is influenced by water temperatures. To address the knowledge gap, numerical simulations considering temperature-dependent eDNA production and degradation were conducted by re-analyzing a previous dataset estimating fish eDNA production and decay rates at different water temperatures, followed by generating population-level eDNA concentrations depending on a given temperature, the number of individuals, and their mass distribution. Results showed that water temperatures had a positive, but relatively small, effect on the strength (R2 value) of the eDNA-abundance relationship, regardless of eDNA production scenarios. In contrast, the sensitivity (regression slope) of the relationship was enhanced by warmer temperatures when temperature-dependent eDNA production was considered, but it decreased unless it was considered. Although further efforts should be required to integrate organism physiology into eDNA production, the present study implied the importance of linking the production mechanism of eDNA particles to organism physiology, offering a groundwork for theorizing the eDNA-abundance relationship depending on environmental conditions, including temperatures, for making eDNA signals more quantitative and reliable.

Meta-Analysis of QTL Mapping and GWAS Reveal Candidate Genes for Heat Tolerance in Small Yellow Croaker, Larimichthys polyactis

High temperatures present considerable challenges to global fish growth and production, yet the genetic basis of heat tolerance remains underexplored. This study combines quantitative trait locus (QTL) mapping and genome-wide association studies (GWAS) to examine the genetics of heat tolerance in Larimichthys polyactis. As a result, a genetic linkage map was constructed with 3237 bin markers spanning 24 linkage groups and totaling 1900.84 centimorgans, using genotyping-by-sequencing of a full-sib family comprising 120 progeny and their two parents. Based on this genetic linkage map, QTL mapping identified four QTLs associated with heat tolerance, which encompassed 18 single nucleotide polymorphisms and harbored 648 genes within the QTL intervals. The GWAS further disclosed 76 candidate genes related to heat tolerance, 56 of which overlapped with the QTL results. Enrichment analysis indicated that these genes are involved in immune response, development, lipid metabolism, and endocrine regulation. qPCR validation of 14 prioritized genes, which were simultaneously enriched in Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways, confirmed significant upregulation of smpd5, polr3d, rab11fip2, and gfpt1, along with downregulation of gpat4 and grk5 after 6 h of heat stress. These findings demonstrate their responsiveness to elevated high temperatures. This meta-analysis of QTL mapping and GWAS has successfully identified functional genes related to heat tolerance, enhancing understanding of the genetic architecture underlying this critical trait in L. polyactis. It also provides a molecular breeding tool to improve genetic traits associated with heat tolerance in cultured L. polyactis.

Case report: Carp edema virus infection in overwintering fish

Carp Edema Virus (CEV) has emerged as a viral threat to the sustainability of European pond fisheries, with water temperature and stress playing a crucial role in disease outbreaks. Here, we report on a natural CEV infection in overwintering common carp (Cyprinus carpio; n = 1,160) broodstock that began to manifest clinically at an unusually low water temperature. In the initial outbreak phase, young broodstock fish exhibited abnormal activity and shoaling at the pond edge. While the water temperature under a discontinuous thin ice layer was 2°C, no deaths were observed. The first fish examined, using standard molecular methods for virological diagnosis, tested negative for CEV. Despite showing clinical signs suggestive of CEV infection, there was no gross pathology except for an increased amount of gill mucus, suggesting that CEV molecular detection may be dependent on infection progression. A shift from a period of cold stress to warming pond water temperatures may have influenced the subsequent progression of the disease. Ongoing clinical signs affected a large part of the population, which remained lethargic and gathered close to the banks. Subsequent virological testing performed ca. 3 weeks after the outbreak and first observation of clinically diseased fish detected the CEV genogroup I agent. CEV-driven die-offs occurred gradually as water temperatures increased to 8°C, with mortalities continuing for ca. 1 month. Interestingly, Přerov scaly carp and Hungarian mirror carp M2 strains differed significantly in mortality rates, at 30 and 60%, respectively. We tested a novel virus detection method, based on loop-mediated isothermal amplification (LAMP) of primers targeting the CEV genogroup I p4A gene, for applicability in the field. Samples from moribund fish, cadavers, and pond water all tested positive, with samples positive using LAMP subsequently confirmed by qPCR. To summarize, our data suggest it may be challenging to detect CEV DNA in both the first carp showing signs and surviving carp; scaly and scaleless carp show differential susceptibility to CEV infection; very low water temperatures of 2-4°C permit CEV infection in common carp; the LAMP method is applicable for rapid on-site CEV detection in clinical and environmental samples.

Local- and Regional-Scale Climate Variability Drives Complex Patterns of Growth Synchrony and Asynchrony in Deep-Sea Snappers Across the Indo-Pacific

Climatic variation can play a critical role in driving synchronous and asynchronous patterns in the expression of life history characteristics across vast spatiotemporal scales. The synchronisation of traits, such as an individual's growth rate, under environmental stress may indicate a loss of phenotypic diversity and thus increased population vulnerability to stochastic deleterious events. In contrast, synchronous growth under favourable ecological conditions and asynchrony during unfavourable conditions may help population resilience and buffer against the negative implications of future environmental variability. Despite the significant implications of growth synchrony and asynchrony to population productivity and persistence, little is known about its causes and consequences either within or among fish populations. This is especially true for long-lived deep-sea species that inhabit environments characterised by large-scale interannual and decadal changes, which could propagate growth synchrony across vast distances. We developed otolith growth chronologies for three deep-sea fishes (Etelis spp.) over 65° of longitude and 20° of latitude across the Indo-Pacific region. Using reconstructed time series of interannual growth from six distinct Exclusive Economic Zones (EEZs), we assessed the level of spatial synchrony at the individual-, population- and species-scale. Across five decades of data, complex patterns of synchronous and asynchronous growth were apparent for adult populations within and among EEZs of the Pacific Ocean, mediated by shifts in oceanographic phenomena such as the Pacific Decadal Oscillation. Overall, our results indicate that the degree of synchrony in biological traits at depth depends on life history stage, spatiotemporal scales of environmental variability and the influence of ecological factors such as competition and dispersal. By determining the magnitude and timing of spatially synchronous growth at depth and its links to environmental variability, we can better understand fluctuations in deep-sea productivity and its vulnerability to future environmental stressors, which are key considerations for sustainability.

Dynamic Trends in Aquatic Product Supply and Consumption in China: Implications for Sustainable Diets and Environmental Impact Reduction

Aquatic foods play a pivotal role in transforming food systems. As the world's leading producer, consumer, and trader of aquatic products, China's potential for sustainable supply and consumption is critical to understand. The aim of this study was to depict the dynamic trends of aquatic products and the consequences of sustainable diets and environmental impacts. A panel dataset about Chinese aquatic products covering the period from 1952 to 2023 was drawn for analysis. Diet sustainability was assessed with the deviation from the Dietary Guidelines for Chinese Residents (2022) and EAT-Lancet recommendations. The environmental impacts of aquatic products' supply and consumption were assessed using carbon footprints and water footprints. The findings reveal that aquatic products' supply increased from 4.65 million tons to 71.16 million tons from 1978 to 2023, and annual aquatic food consumption per capita increased from 3.50 kg in 1978 to 15.20 kg. While overall supply meets consumption needs, structural imbalances persist at the provincial level. Over time, the influence of marine fishery products has declined from 1.06 million tons (63.63%) in 1952 to 35.85 million tons (50.38%) in 2023, whereas offshore aquaculture shows promising potential for meeting future supply demands (23.96 million tons in 2023, accounting for 66.82% of marine fishery production). To align with healthy dietary goals and environmentally sustainable food systems, provincial aquatic food demand across China was adjusted. The carbon footprints and water footprints of both current and adjusted consumption patterns were also assessed. The results indicate that adjusting consumption based on the Dietary Guidelines for Chinese Residents (2022) and EAT-Lancet recommendations could reduce environmental impacts to different degrees. The findings could offer valuable references and insights into developing sustainable strategies in aquatic product management and advancing food system transformation.

The role of acoustic telemetry in assessing fish connectivity within marine seascapes: A global review

The study of aquatic animal movements is a rapidly growing field of research, with tracking methodology ever developing and refining. Acoustic telemetry is arguably the most popular method used to study the movements of fish. Despite this method being able to elucidate many aspects of movement behavior, including residency, home range, and migration, among others, one aspect that remains challenging is the study and definition of connectivity, particularly within marine seascapes. As such, this review assesses published literature on acoustic telemetry studies, which have specifically assessed some aspect of fish connectivity, and discusses these in terms of study distribution and overall trends, the diversity of taxa and life stage assessed, the role that large-scale acoustic telemetry networks plays in assessing connectivity of marine fishes, how connectivity studies have been used in an applied context, and proposes definitions linked to specific types of connectivity, which will assist future researchers when conceptualizing studies. Further, methods that can be used in conjunction with acoustic telemetry to complement the data are discussed. Given that marine resources and habitats are intricately connected, this review highlights the critical role that acoustic telemetry can play in assessing this link. It is envisaged that our developed framework of connectivity definitions will assist future studies and stakeholders in assessing ecosystem functioning and ultimately contribute to improved conservation and management of marine fish populations and ecosystems.

Water quality-fisheries tradeoffs in a changing climate underscore the need for adaptive ecosystem-based management

Changes driven by both unanticipated human activities and management actions are creating wicked management landscapes in freshwater and marine ecosystems that require new approaches to support decision-making. By linking a predictive model of nutrient- and temperature-driven bottom hypoxia with observed commercial fishery harvest data from Lake Erie (United States-Canada) over the past century (1928-2022) and climate projections (2030-2099), we show how simple, yet robust models and routine monitoring data can be used to identify tradeoffs associated with nutrient management and guide decision-making in even the largest of aquatic ecosystems now and in the future. Our approach enabled us to assess planned nutrient load reduction targets designed to mitigate nutrient-driven hypoxia and show why they appear overly restrictive based on current fishery needs, indicating tradeoffs between water quality and fisheries management goals. At the same time, our temperature results show that projected climate change impacts on hypoxic extent will require more stringent nutrient regulations in the future. Beyond providing a rare example of bottom hypoxia driving changes in fishery harvests at an ecosystem scale, our study illustrates the need for adaptive ecosystem-based management, which can be informed by simple predictive models that can be readily applied over long time periods, account for tradeoffs across multiple management sectors (e.g., water quality, fisheries), and address ecosystem nonstationarity (e.g., climate change impacts on management targets). Such approaches will be critical for maintaining valued ecosystem services in the many aquatic systems worldwide that are vulnerable to multiple drivers of environmental change.

Mitogenomic Architecture of Atlantic Emperor Lethrinus atlanticus (Actinopterygii: Spariformes): Insights into the Lineage Diversification in Atlantic Ocean

The evolutionary history of emperors, particularly in the Atlantic and Indo-West Pacific Oceans, remains largely unmapped. This study explores the maternal lineage evolution of Lethrinids by examining the complete mitogenome of Lethrinus atlanticus, which is endemic to the Eastern Atlantic Ocean. Utilizing advanced next-generation sequencing, we found that the mitogenome spans 16,789 base pairs and encompasses 37 genes, including 13 protein-coding genes (PCGs), two ribosomal RNAs, 22 transfer RNAs, and an AT-rich control region (CR). Our analysis indicates a preference for AT base pairs in the L. atlanticus mitogenome (53.10%). Most PCGs begin with the ATG codon, except for COI, which starts with GTG. Relative synonymous codon usage reveals high frequencies for alanine, leucine, proline, serine, and threonine. The ratio of nonsynonymous to synonymous substitutions suggests strong negative selection across all PCGs in Lethrinus species. Most transfer RNAs exhibit typical cloverleaf structures, with the exception of tRNA-serine (GCT), which lacks a dihydrouracil stem. Comparative analysis of conserved sequence blocks across the CRs of three Lethrinus species shows notable differences in length and nucleotide composition. Phylogenetic analysis using concatenated PCGs clearly distinguishes all Lethrinus species, including L. atlanticus, and sheds light on the evolutionary relationships among Spariformes species. The estimated divergence time of approximately 20.67 million years between L. atlanticus and its Indo-West Pacific relatives provides insights into their historical separation and colonization during the late Oligocene. The distribution of Lethrinids may be influenced by ocean currents and ecological factors, potentially leading to their speciation across the Eastern Atlantic and Indo-West Pacific. This study enhances our understanding of the genetic diversity and phylogenetic relationships within Lethrinus species. Further exploration of other emperor fish mitogenomes and comprehensive genomic data could provide vital insights into their genetic makeup, evolutionary history, and environmental adaptability in marine ecosystems globally.

Extreme Temperatures Reduce Copepod Performance and Change the Relative Abundance of Internal Microbiota

Copepods are one of the most abundant invertebrate groups in the seas and oceans and are a significant food source for marine animals. Copepods are also particularly sensitive to elevated temperatures. However, it is relatively unknown how the internal microbiome influences copepod susceptibility to warming. We addressed this fundamental knowledge gap by assessing key life history traits (survival, development, and reproduction) and changes in the internal microbiome in the tropical calanoid copepod Acartia sp. in response to warming (26°C, 30°C, and 34°C). Copepod microbiomes were analyzed using high throughput DNA sequencing of V1-V9 of 16S rRNA hypervariable regions. Copepod performance was better at 30°C than at 26°C, as indicated by faster development, a higher growth rate, and fecundity. However, these parameters strongly decreased at 34°C. We recorded 1,262,987 amplicon sequence reads, corresponding to 392 total operational taxonomic units (OTUs) at 97% similarity. Warming did not affect OTU numbers and the biodiversity indices, but it substantially changed the relative abundance of three major phyla: Proteobacteria, Actinobacteria, and Bacteroidota. The thermophilic and opportunistic Proteobacteria and Bacteroidota increased under extreme temperatures (34°C) while Actinobacteria abundance was strongly reduced. Changes in the relative abundance of these bacteria might be related to reduced copepod growth, survival, and reproduction under extreme temperatures. Profiling the functional role of all internal bacterial groups in response to the temperature change will fundamentally advance our mechanistic understanding of the performance of tropical copepods and, more generally, marine invertebrates to a warming climate.

Robust fisheries management strategies under deep uncertainty

Fisheries worldwide face uncertain futures as climate change manifests in environmental effects of hitherto unseen strengths. Developing climate-ready management strategies traditionally requires a good mechanistic understanding of stock response to climate change in order to build projection models for testing different exploitation levels. Unfortunately, model-based projections of fish stocks are severely limited by large uncertainties in the recruitment process, as the required stock-recruitment relationship is usually not well represented by data. An alternative is to shift focus to improving the decision-making process, as postulated by the decision-making under deep uncertainty (DMDU) framework. Robust Decision Making (RDM), a key DMDU concept, aims at identifying management decisions that are robust to a vast range of uncertain scenarios. Here we employ RDM to investigate the capability of North Sea cod to support a sustainable and economically viable fishery under future climate change. We projected the stock under 40,000 combinations of exploitation levels, emission scenarios and stock-recruitment parameterizations and found that model uncertainties and exploitation have similar importance for model outcomes. Our study revealed that no management strategy exists that is fully robust to the uncertainty in relation to model parameterization and future climate change. We instead propose a risk assessment that accounts for the trade-offs between stock conservation and profitability under deep uncertainty.

Exploring spatio-temporal changes in coastal recreational fisheries and potential links to extreme weather events

Extreme weather events across coastal environments are expected to increase in frequency under predicted climate change scenarios. These events can impact coastal recreational fisheries and their supporting ecosystems by influencing the productivity of fish stocks or altering behaviours and decision-making among fishers. Using off-site telephone/diary survey data on estuarine and oceanic recreational fishing activity in eastern Australia, we analyse interannual and geographic variability in bream (Acanthopagrus spp) and snapper (Chrysophrys auratus) catch, total effort and total catch per unit effort (CPUE) through a period (2013/2014, 2017/2018 and 2019/2020) that encompassed severe drought, bushfires and flooding. Interacting spatial and temporal differences were detected for bream and may reflect spatial variation in the intensity and extent of some of the extreme weather events. The catch of snapper did not change temporally, providing little evidence that this species' catch may be influenced by the extreme weather events. Independent bioregional and temporal effects on effort were detected, while CPUE only showed significant bioregional differences. Although adverse conditions created by the extreme weather events may have dissuaded fisher participation and impacted effort, we propose that the observed temporal patterns in effort reflect the early influence of socio-economic changes brought on by the COVID-19 pandemic on coastal recreational fishing, over and above the impacts of extreme weather events. This study demonstrates how interrelated ecological, social and economic factors can shape coastal recreational fisheries and facilitates development of management strategies to address future threats to the sector.

Modeling tropical tuna shifts: An inflated power logit regression approach

We introduce a new class of zero-or-one inflated power logit (IPL) regression models, which serve as a versatile tool for analyzing bounded continuous data with observations at a boundary. These models are applied to explore the effects of climate changes on the distribution of tropical tuna within the North Atlantic Ocean. Our findings suggest that our modeling approach is adequate and capable of handling the outliers in the data. It exhibited superior performance compared to rival models in both diagnostic analysis and regarding the inference robustness. We offer a user-friendly method for fitting IPL regression models in practical applications.

Coordinated dynamics of aquaculture ponds and water eutrophication owing to policy: A case of Jiangsu province, China

Aquaculture ponds (APs) are rapidly expanding globally and are considered crucial for guaranteeing the supply of food, population growth, and economic development. However, the rapid expansion of aquaculture not only brought benefits but also a series of eco-environmental issues, such as water eutrophication. To achieve sustainable development, it is essential to gain a profound understanding of the spatiotemporal evolution of APs, the drivers behind their dynamics, and their relationship with the aquatic environment. Jiangsu Province (JS) in China, a historically significant aquaculture region, encompasses two prominent river basins: the Huai River Basin (HRB) and the Yangtze River Basin (YRB). In light of the construction of an ecological civilization, JS serves as a demonstration and pioneering area for basin protection and development. Therefore, this study focuses on JS, aiming to elucidate the spatiotemporal dynamics of APs, the corresponding relationship with basin management policies, and the impact on water eutrophication. The results revealed that: (1) in 2022, APs in JS were unevenly distributed, with a total area of 3278.78 km2, of which 79 % was located in the HRB. (2) During 2016-2022, APs exhibited an initial growth trend before 2019, followed by a decrease. (3) Due to policy interventions, AP changes within different basins showed opposite trends, and the corresponding water eutrophic state aligned with AP dynamics. The findings of this study can serve as a typical case to provide scientific evidence for the formulation and implementation of policies to improve the water environment in eutrophic basins.

A traits-based approach to assess aquaculture's contributions to food, climate change, and biodiversity goals

Aquaculture has the potential to support a sustainable and equitable food system in line with the United Nations Sustainable Development Goals (SDG) on food security, climate change, and biodiversity (FCB). Biological diversity amongst aquaculture organisms can drive diverse contributions to such goals. Existing studies have assessed the performance of a limited number of taxa in the general context of improving aquaculture production, but few explicitly consider the biological attributes of farmed aquatic taxa at the FCB nexus. Through a systematic literature review, we identify key traits associated with FCB and evaluate the potential of aquaculture to contribute to FCB goals using a fuzzy logic model. The majority of identified traits are associated with food security, and two-thirds of traits linked with food security are also associated with climate change or biodiversity, revealing potential co-benefits of optimizing a single trait. Correlations between FCB indices further suggest that challenges and opportunities in aquaculture are intertwined across FCB goals, but low mean FCB scores suggest that the focus of aquaculture research and development on food production is insufficient to address food security, much less climate or biodiversity issues. As expected, production-maximizing traits (absolute fecundity, the von Bertalanffy growth function coefficient K, macronutrient density, maximum size, and trophic level as a proxy for feed efficiency) highly influence a species' FCB potential, but so do species preferences for environmental conditions (tolerance to phosphates, nitrates, and pH levels, as well as latitudinal and geographic ranges). Many highly farmed species that are typically associated with food security, especially finfish, score poorly for food, climate, and biodiversity potential. Algae and mollusc species tend to perform well across FCB indices, revealing the importance of non-fish species in achieving FCB goals and potential synergies in integrated multi-trophic aquaculture systems. Overall, this study provides decision-makers with a biologically informed assessment of desirable aquaculture traits and species while illuminating possible strategies to increase support for FCB goals. Our findings can be used as a foundation for studying the socio-economic opportunities and barriers for aquaculture transitions to develop equitable pathways toward FCB-positive aquaculture across nuanced regional contexts.

Ecological Insights, and Fin Fish Diversity in Carps Spawning Grounds: Case Studies from the Surma River and Tanguar Haor, Bangladesh

This study aims to provide a thorough ecological understanding of fin fish diversity within carp spawning grounds in the Surma River and Tanguar haor. Over two spawning seasons, this research investigates ecological factors impacting fin fish diversity and abundance in carp spawning grounds of the Surma River and Tanguar haor, emphasizing water quality, habitat features, spawn availability, and environmental influences. Fish spawn samples were collected with eight "Savar nets" at chosen sites and reared in a fiberglass tank at the mini hatchery for species identification. The representative spawn samples were examined under a microscope for preliminary species identification before rearing. The study found that both the Surma River and Tanguar haor offer ideal conditions for carp spawning due to factors such as water quality, natural food availability, habitat suitability, and favorable climatic conditions. The study identified 39 fish species under the 10 fish groups from both locations, with a higher percentage of carp species (31.42%) in the Surma River in 2021 compared to 2022 (22.50%). In Tanguar haor, the percentage of carp species was 7.55% and 6.50% in 2021 and 2022, respectively. The Surma River's ecological indices (2021-2022) indicated decreased diversity, likely due to environmental degradation, while Tanguar haor showed lower diversity possibly attributable to multiple environmental stressors. The dominant carp species, Labeo calbasu, Labeo bata, and Labeo gonius, were identified in both the Surma River and Tanguar haor. The spawning distribution varied among different locations, with some sites showing a presence of carp species, such as Hajipur (T1) in the Surma River and Alam Duar (T2) in Tanguar haor. The findings highlight the importance of hydrological and environmental parameters in shaping carp spawning habitat distribution and abundance, contributing to aquatic biodiversity conservation and resource management.

Ecosystem-level responses to multiple stressors using a time-dynamic food-web model: The case of a re-oligotrophicated coastal embayment (Saronikos Gulf, E Mediterranean)

Multiple stressors may combine in unexpected ways to alter the structure of ecological systems, however, our current ability to evaluate their ecological impact is limited due to the lack of information concerning historic trophic interactions and ecosystem dynamics. Saronikos Gulf is a heavily exploited embayment in the E Mediterranean that has undergone significant ecological alterations during the last 20 years including a shift from long-standing eutrophic to oligotrophic conditions in the mid-2000's. Here we used a historical Ecopath food-web model of Saronikos Gulf (1998-2000) and fitted the time-dynamic module Ecosim to biomass and catch time series for the period 2001-2020. We then projected the model forward in time from 2021 to 2050 under 8 scenarios to simulate ecosystem responses to the individual and combined effect of sea surface temperature increase, primary productivity shifts and fishing effort release. Incorporating trophic interactions, climate warming, fishing and primary production improved model fit, depicting that both fishing and the environment have historically influenced ecosystem dynamics. Retrospective simulations of the model captured historical biomass and catch trends of commercially important stocks and reproduced successfully the marked recovery of marine resources 10 years after re-oligotrophication. In future scenarios increasing temperature had a detrimental impact on most functional groups, increasing and decreasing productivity had a positive and negative effect on all respectively, while fishing reductions principally benefited top predators. Combined stressors produced synergistic or antagonistic effects depending on the direction and magnitude of change of each stressor in isolation while their overall impact seemed to be strongly mediated via food-web interactions. Such holistic approaches advance of our mechanistic understanding of ecosystems enabling us to develop more effective management strategies in the face of a rapidly changing marine environment.

Transient demographic dynamics of recovering fish populations shaped by past climate variability, harvest, and management

Large-scale commercial harvesting and climate-induced fluctuations in ocean properties shape the dynamics of marine populations as interdependent drivers at varied timescales. Persistent selective removals of larger, older members of a population can distort its demographic structure, eroding resilience to fluctuations in habitat conditions and thus amplifying volatility in transient dynamics. Many historically depleted marine fish stocks have begun showing signs of recovery in recent decades following the implementation of stricter management measures. But these interventions coincide with accelerated changes in the oceans triggered by increasingly warmer, more variable climates. Applying multilevel models to annual estimates of demographic metrics of 38 stocks comprising 11 species across seven northeast Atlantic ecoregions, this study explores how time-varying local and regional climates contributed to the transient dynamics of recovering populations exposed to variable fishing pressures moderated by management actions. Analyses reveal that progressive reductions in fishing pressure and shifting climate conditions discontinuously shaped rebuilding patterns of the stocks through restorations of maternal demographic structure (reversing age truncation) and reproductive capacity. As the survival rate and demographic structure of reproductive fish improved, transient growth became less sensitive to variability in recruitment and juvenile survival and more to that in adult survival. As the biomass of reproductive fish rose, recruitment success also became increasingly regulated by density-dependent processes involving higher numbers of older fish. When reductions in fishing pressure were insufficient or delayed, however, stocks became further depleted, with more eroded demographic structures. Although warmer local climates in spawning seasons promoted recruitment success in some ecoregions, changing climates in recent decades began adversely affecting reproductive performances overall, amplifying sensitivities to recruitment variability. These shared patterns underscore the value of demographic transients in developing robust strategies for managing marine resources. Such strategies could form the foundation for effective applications of adaptive measures resilient to future environmental change.

Areas of spatial overlap between common bottlenose dolphin, recreational boating, and small-scale fishery: management insights from modelling exercises

Background

Sustainable management requires spatial mapping of both species distribution and human activities to identify potential risk of conflict. The common bottlenose dolphin (Tursiops truncatus) is a priority species of the European Union Habitat Directive, thus, to promote its conservation, the understanding of habitat use and distribution, as well as the identification and spatial trend of the human activities which may directly affect populations traits, is pivotal.

Methods

A MaxEnt modeling approach was applied to predict the seasonal (from April to September) habitat use of a small population of bottlenose dolphins in the north-western Sardinia (Mediterranean Sea) in relation to environmental variables and the likelihoods of boat and fishing net presence. Then, the overlapping areas between dolphin, fishing net and boat presence were identified to provide insights for the marine spatial management of this area.

Results

Three of the main factors influencing the seasonal distribution of bottlenose dolphins in the area are directly (boating and fishing) or indirectly (ocean warming) related to human activities. Furthermore, almost half of the most suitable area for dolphins overlapped with areas used by fishing and boating. Finally, relying on fishing distribution models, we also shed light on the potential impact of fishing on the Posidonia oceanica beds, a protected habitat, which received higher fishing efforts than other habitat types.

Discussion

Modelling the spatial patterns of anthropogenic activities was fundamental to understand the ecological impacts both on cetacean habitat use and protected habitats. A greater research effort is suggested to detect potential changes in dolphin habitat suitability, also in relation to ocean warming, to assess dolphin bycatch and the status of target fish species, and to evaluate sensitive habitats conditions, such as the Posidonia oceanica meadow.

Adrenal response to ACTH challenge alters thyroid and immune function and varies with body reserves in molting adult female northern elephant seals

Intrinsic stressors associated with life-history stages may alter the responsiveness of the hypothalamic-pituitary-adrenal axis and responses to extrinsic stressors. We administered adrenocorticotropic hormone (ACTH) to 24 free-ranging adult female northern elephant seals (NESs) at two life-history stages: early and late in their molting period and measured a suite of endocrine, immune, and metabolite responses. Our objective was to evaluate the impact of extended, high-energy fasting on adrenal responsiveness. Animals were blood sampled every 30 min for 120 min post-ACTH injection, then blood was sampled 24 h later. In response to ACTH injection, cortisol levels increased 8- to 10-fold and remained highly elevated compared with baseline at 24 h. Aldosterone levels increased 6- to 9-fold before returning to baseline at 24 h. The magnitude of cortisol and aldosterone release were strongly associated, and both were greater after extended fasting. We observed an inverse relationship between fat mass and the magnitude of cortisol and aldosterone responses, suggesting that body reserves influenced adrenal responsiveness. Sustained elevation in cortisol was associated with alterations in thyroid hormones; both tT3 and tT4 concentrations were suppressed at 24 h, while rT3 increased. Immune cytokine IL-1β was also suppressed after 24 h of cortisol elevation, and numerous acute and sustained impacts on substrate metabolism were evident. Our data suggest that female NESs are more sensitive to stress after the molt fast and that acute stress events can have important impacts on metabolism and immune function. These findings highlight the importance of considering life-history context when assessing the impacts of anthropogenic stressors on wildlife.

Temporally-displaced Mississippi River spring flood pulse shows muted aquatic ecosystem response in estuarine waters: A climate change warning for coastal foodwebs

Mississippi River water levels typically rise in the early spring after snow melt in the extensive watershed. However, in 2016, warm air temperatures coupled with high precipitation led to a historically early river flood pulse, resulting in the opening of a flood release valve (Bonnet Carré Spillway) in early January to protect the city of New Orleans, Louisiana. The goal of this research was to determine the ecosystem response of this wintertime nutrient flood pulse on the receiving estuarine system and compare it to historical opening responses, which are generally several months later. Nutrients, TSS, and Chl a were measured along a 30 km transect in the Lake Pontchartrain estuary, before, during, and after the river diversion event. In the past, NO_x concentrations were quickly reduced to below detection in the estuary in <4 weeks post-event accompanied by a moderate phytoplankton bloom. However, due to seasonal limitations (cold water temperatures and light limitation) during the 2016 event, NO_x remained elevated for >2 months post-closure and Chl a values were low, indicating limited assimilation of nutrients into phytoplankton biomass. Consequently, much of the bioavailable nitrogen was denitrified by sediments and dispersed to the coastal ocean over time, limiting the transfer of nutrients into the food web by means of a spring phytoplankton bloom. An increasing warming trend in temperate and polar river watersheds is leading to earlier spring flood pulses, altering the timing of coastal nutrient transport, decoupled from conditions supporting primary production, which could significantly affect coastal food webs.

Our evolved understanding of the human health risks of mercury

Mercury (Hg) is a chemical of health concern worldwide that is now being acted upon through the Minamata Convention. Operationalizing the Convention and tracking its effectiveness requires empathy of the diversity and variation of mercury exposure and risk in populations worldwide. As part of the health plenary for the 15th International Conference on Mercury as a Global Pollutant (ICMGP), this review paper details how scientific understandings have evolved over time, from tragic poisoning events in the mid-twentieth century to important epidemiological studies in the late-twentieth century in the Seychelles and Faroe Islands, the Arctic and Amazon. Entering the twenty-first century, studies on diverse source-exposure scenarios (e.g., ASGM, amalgams, contaminated sites, cosmetics, electronic waste) from across global regions have expanded understandings and exemplified the need to consider socio-environmental variables and local contexts when conducting health studies. We conclude with perspectives on next steps for mercury health research in the post-Minamata Convention era.

Integration of transcriptome and proteome analyses reveals the regulation mechanisms of Larimichthys polyactis liver exposed to heat stress

Small yellow croaker (Larimichthys polyactis) is one of the most economically important marine fishery species. L. polyactis aquaculture has experienced stress response and the frequent occurrence of diseases, bringing huge losses to the aquaculture industry. Little is known about the regulation mechanism of heat stress response in L. polyactis. In this study, to provide an overview of the heat-tolerance mechanism of L. polyactis, the transcriptome and proteome of the liver of L. polyactis on the 6 h after high temperature (32 °C) treatment were analyzed using Illumina HiSeq 4000 platform and isobaric tag for relative and absolute quantitation (iTRAQ). A total of 3700 upregulated and 1628 downregulated genes (differentially expressed genes, DEGs) were identified after heat stress in L. polyactis. Also, 198 differentially expressed proteins (DEPs), including 117 upregulated and 81 downregulated proteins, were identified. Integrative analysis revealed that 72 genes were significantly differentially expressed at transcriptome and protein levels. Functional analysis showed that arginine biosynthesis, tyrosine metabolism, pentose phosphate pathway, starch and sucrose metabolism, and protein processing in the endoplasmic reticulum were the main pathways responding to heat stress. Among the pathways, protein processing in the endoplasmic reticulum was enriched by most DEGs/DEPs, which suggests that this pathway may play a more important role in the heat stress response. Further insights into the pathway revealed that transcripts and proteins, especially HSPs and PDIs, were differentially expressed in response to heat stress. These findings contribute to existing data describing the fish response to heat stress and provide information about protein levels, which are of great significance to a deeper understanding of the heat stress responding regulation mechanism in L. polyactis and other fish species.

Evaluating Dermal Bone as a Novel Source of Endocrine Information in Ninespine and Threespine Stickleback Fish

Monitoring the physiology of small aquatic and marine teleost fish presents challenges. Blood samples, often the first choice for endocrinologists, can be difficult or even impossible to obtain and alternative matrices currently used for hormone analyses do not occur in fishes (e.g., hair, feathers etc.) or are not easily collected from small aquatic organisms (e.g., urine and feces). Some teleosts, however, have enlarged bony dermal elements that possibly accumulate and store steroid hormones in physiological relevant concentrations. Both threespine stickleback (Gasterosteus aculeatus) and ninespine stickleback (Pungitius pungitius) have a series of external, lateral bony plates, dorsal spines, and a pair of pelvic spines attached to the pelvic girdle. We investigated if cortisol, the primary circulating glucocorticoid in teleosts, could be extracted from stickleback dermal bone and quantified using a commercially available enzyme immunoassay (EIA). We successfully validated a cortisol EIA for dermal bone extracts, determined that cortisol was detectable in both species, and found that dermal bone cortisol levels significantly correlated with cortisol levels in whole body homogenate. Ninespine stickleback had significantly higher dermal bone cortisol concentrations than threespine stickleback and female threespine stickleback tended to have over twice the mean dermal bone cortisol concentration than males. Because both stickleback species are widely used for ecotoxicological studies, using dermal bone as a source of endocrine information, while leaving the body for contaminant, genomic, histological, and stable isotope analyses, could be a powerful and parsimonious tool. Further investigation and physiological validations are necessary to fully understand the utility of this new sample matrix.

Estimating energetic intake for marine mammal bioenergetic models

Bioenergetics is the study of how animals achieve energetic balance. Energetic balance results from the energetic expenditure of an individual and the energy they extract from their environment. Ingested energy depends on several extrinsic (e.g prey species, nutritional value and composition, prey density and availability) and intrinsic factors (e.g. foraging effort, success at catching prey, digestive processes and associated energy losses, and digestive capacity). While the focus in bioenergetic modelling is often on the energetic costs an animal incurs, the robust estimation of an individual's energy intake is equally critical for producing meaningful predictions. Here, we review the components and processes that affect energy intake from ingested gross energy to biologically useful net energy (NE). The current state of knowledge of each parameter is reviewed, shedding light on research gaps to advance this field. The review highlighted that the foraging behaviour of many marine mammals is relatively well studied via biologging tags, with estimates of success rate typically assumed for most species. However, actual prey capture success rates are often only assumed, although we note studies that provide approaches for its estimation using current techniques. A comprehensive collation of the nutritional content of marine mammal prey species revealed a robust foundation from which prey quality (comprising prey species, size and energy density) can be assessed, though data remain unavailable for many prey species. Empirical information on various energy losses following ingestion of prey was unbalanced among marine mammal species, with considerably more literature available for pinnipeds. An increased understanding and accurate estimate of each of the components that comprise a species NE intake are an integral part of bioenergetics. Such models provide a key tool to investigate the effects of disturbance on marine mammals at an individual and population level and to support effective conservation and management.

Dietary nano-selenium alleviates heat stress-induced intestinal damage through affecting intestinal antioxidant capacity and microbiota in rainbow trout (Oncorhynchus mykiss)

Heat stress-induced intestinal damage is a key event in fish pathology. Nano-selenium (nano-Se) shows remarkably high biological activity and low toxicity, making it an ideal and ecological Se formulation; however, to date, the protective effects of nano-Se against heat stress-induced intestinal injury and pertinent molecular mechanisms remain unknown. Herein, rainbow trout (Oncorhynchus mykiss) were fed either a basal diet or basal diet + 5 mg/kg nano-Se. Samples were collected before (18 °C for 9 days; CG18 and Se18 groups) and after (24 °C for 8 h; CG24 and Se24 groups) heat stress treatment. On heat stress exposure, intestinal villus height, muscularis thickness, and goblet cell number decreased, and expression of tight junction proteins (ZO-1, occludin, and claudin-8d) was downregulated; dietary supplementation with nano-Se alleviated these effects. Furthermore, in the presence of nano-Se, catalase activity was elevated, and expression of diverse heat shock proteins (Hsp70b, Hsp90α, and Hsp30), selenoproteins (Gpx1a, Gpx1b1, and Trx), and anti-inflammatory cytokine (TGF-β) was upregulated. In contrast, nano-Se supplementation significantly alleviated the increase of the expression of pro-inflammatory cytokines (IL-1β and TNF-α) and the malondialdehyde content. We also observed that heat stress markedly increased the relative abundance of Actinobacteria, Firmicutes, Methylobacterium, Akkermansia, and Deinococcus and decreased that of Proteobacteria; nano-Se supplementation restored these changes, making their distribution similar to that in the control group. Overall, our findings suggest that nano-Se plays a protective role against heat stress-induced intestinal damage in rainbow trout by promoting the recovery of antioxidant enzyme activity, enhancing protein repair, alleviating inflammatory responses, and restoring intestinal microbiota composition.

Responses of coastal fishery resources to rapid environmental changes

Coastal systems experience strong impacts of ongoing environmental change, affecting fish communities and subsequently fishery yields. In the Baltic Sea, the combined effects of climate-induced changes and eutrophication-related pressures constitute major threats to its living resources. Although much work has been devoted to uncovering environmental impacts on the commercially most valuable fish stocks, only little is known about community-wide responses of fished species and how environmental change may affect their yield. In this study, the authors use a joint species distribution modelling framework to disentangle environmental impacts on species-specific fishery yields of 16 fished species along the coast of Finland over four decades. The authors show that environmental covariates substantially contributed to variations in fishery yields and are likely to have strong impacts on fished resources also in the future. Salinity and near-bottom oxygen concentration emerged as the strongest environmental drivers of yields at the community level, whereas temperature was particularly important for cod (Gadus morhua) and sprat (Sprattus sprattus) yields. The authors found shore density to be an important predictor for fisheries resources especially for freshwater fish. The results of this study suggest that the changes in environmental conditions during the past four decades had a positive effect on the yields of freshwater and warm-affinity species, whereas yields of marine cold-affinity species have been mainly negatively affected by contracting favourable habitats, becoming warmer and less saline.

Foresighting future climate change impacts on fisheries and aquaculture in vietnam

The Vietnamese fisheries sector, including both marine fisheries and aquaculture, has made spectacular progress in recent years, becoming one of the top seafood producing and exporting countries in the world. Looking forward, development goals of this sector must address challenges associated with climate change, including changing distribution of commercially important marine species such as tuna and disruptions to land-based aquaculture production systems. This study investigates the prospective climate change impacts on Vietnam's fisheries sector, focusing on four key commodities including capture fisheries (tuna), freshwater aquaculture (pangasius catfish and tilapia), and brackish water aquaculture (shrimp). The extent of impact varies, but climate change represents a potentially significant threat to sustainable production in each production system. Producers, policy makers, and other stakeholders need to plan for and adapt to climate change to ensure the sustainable development of Vietnam's fisheries sector.

Perceptions and attitudes towards climate change in fishing communities of the Sudd Wetlands, South Sudan

The Sudd in South Sudan, formed by the White Nile's Baḥr al-Jabal section, is one of the largest and most important wetlands in the world. Communities in the region almost exclusively depend on fisheries for food and livelihoods. Although threatened by over-exploitation and habitat changes, fish populations are also affected by climate change. Using semi-structured questionnaires, we assessed fisherfolk's opinions of how recent variation in climate affected their livelihoods and the environment. Fisherfolk perceived that climate had changed in the past decade and were negatively impacted by this. Interviewees reported average higher temperatures, a greater frequency of floods and droughts, unpredictable timing of seasons, and erratic rainfall. Destruction of fishing villages/camps, loss and damage of fishing equipment, shifts in the fishing calendar, reduction of fish trade, and fish catch declines as well as psycho-social problems were given as the major consequences of climate change. Causes of climate change and variability were perceived to be linked to uncontrolled harvest of forest resources, anger of God and ancestors, and natural variability in climate. Most respondents expressed a desire to adopt more responsible behavior such as planting trees and establishing community nurseries, being educated on climate change risks, and sustainable fisheries management. Our results show that fisherfolk in the Sudd are troubled by climate change impacts on their livelihoods and on fish populations. In South Sudan, climate change has been reported from hydroclimatological data but concrete impacts on people remain largely unknown and of little concern because of recent wars and the poor economy. Our study provides an example of how fisherfolks' local ecological knowledge (LEK) can be used as an early warning system of the negative impacts on livelihoods and fish populations and support adaptation to the changing climate.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10113-022-01928-w.

Heat Stress Weakens the Skin Barrier Function in Sturgeon by Decreasing Mucus Secretion and Disrupting the Mucosal Microbiota

Heat stress induced by global warming has damaged the well-being of aquatic animals. The skin tissue plays a crucial role as a defense barrier to protect organism, however, little is known about the effect of heat stress on fish skin, particularly in cold-water fish species. Here, we investigated the effects of mild heat stress (24°C, MS) and high heat stress (28°C, HS) on Siberian sturgeon skin using RNA-seq, histological observation, and microbial diversity analysis. In RNA-seq, 8,819 differentially expressed genes (DEGs) in MS vs. C group and 12,814 DEGs in HS vs. C group were acquired, of which the MS vs. C and HS vs. C groups shared 3,903 DEGs, but only 1,652 DEGs were successfully annotated. The shared DEGs were significantly enriched in pathways associating with mucins synthesis. Histological observation showed that the heat stresses significantly reduced the number of skin mucous cells and induced the damages of epidermis. The microbial diversity analysis elicited that heat stress markedly disrupted the diversity and abundance of skin microbiota by increasing of potential pathogens (Vibrionimonas, Mesorhizobium, and Phyllobacterium) and decreasing of probiotics (Bradyrhizobium and Methylovirgula). In conclusion, this study reveals that heat stress causes adverse effects on sturgeon skin, reflecting in decreasing the mucus secretion and disordering the mucosal microbiota, which may contribute to develop the preventive strategy for heat stress caused by global warming.

Effects of exposure to elevated temperature and different food levels on the escape response and metabolism of early life stages of white seabream, Diplodus sargus

Recent literature suggests that anthropogenic stressors can disrupt ecologically relevant behaviours in fish, such as the ability to escape from predators. Disruption of these behaviours at critical life history transitions, such as the transition from the pelagic environment to the juvenile/adult habitat, may have even greater repercussions. The literature suggests that an increase in temperature can affect fish escape response, as well as metabolism; however, few studies have focused on the acute sensitivity responses and the potential for acclimation through developmental plasticity. Here, we aimed at evaluating the acute and long-term effects of exposure to warming conditions on the escape response and routine metabolic rate (RMR) of early life stages of the white seabream, Diplodus sargus. Additionally, as food availability may modulate the response to warming, we further tested the effects of long-term exposure to high temperature and food shortage, as individual and interacting drivers, on escape response and RMR. Temperature treatments were adjusted to ambient temperature (19°C) and a high temperature (22°C). Feeding treatments were established as high ration and low ration (50% of high ration). Escape response and RMR were measured after the high temperature was reached (acute exposure) and after 4 weeks (prolonged exposure). Acute warming had a significant effect on escape response and generated an upward trend in RMR. In the long term, however, there seems to be an acclimation of the escape response and RMR. Food shortage, interacting with high temperature, led to an increase in latency response and a significant reduction in RMR. The current study provides relevant experimental data on fishes' behavioural and physiological responses to the combined effects of multiple stressors. This knowledge can be incorporated in recruitment models, thereby contributing to fine-tuning of models required for fisheries management and species conservation.

Non-Lethal Sampling Supports Integrative Movement Research in Freshwater Fish

Freshwater ecosystems and fishes are enormous resources for human uses and biodiversity worldwide. However, anthropogenic climate change and factors such as dams and environmental contaminants threaten these freshwater systems. One way that researchers can address conservation issues in freshwater fishes is via integrative non-lethal movement research. We review different methods for studying movement, such as with acoustic telemetry. Methods for connecting movement and physiology are then reviewed, by using non-lethal tissue biopsies to assay environmental contaminants, isotope composition, protein metabolism, and gene expression. Methods for connecting movement and genetics are reviewed as well, such as by using population genetics or quantitative genetics and genome-wide association studies. We present further considerations for collecting molecular data, the ethical foundations of non-lethal sampling, integrative approaches to research, and management decisions. Ultimately, we argue that non-lethal sampling is effective for conducting integrative, movement-oriented research in freshwater fishes. This research has the potential for addressing critical issues in freshwater systems in the future.

Tracking the impacts of climate change on human health via indicators: lessons from the Lancet Countdown

BACKGROUND

In the past decades, climate change has been impacting human lives and health via extreme weather and climate events and alterations in labour capacity, food security, and the prevalence and geographical distribution of infectious diseases across the globe. Climate change and health indicators (CCHIs) are workable tools designed to capture the complex set of interdependent interactions through which climate change is affecting human health. Since 2015, a novel sub-set of CCHIs, focusing on climate change impacts, exposures, and vulnerability indicators (CCIEVIs) has been developed, refined, and integrated by Working Group 1 of the "Lancet Countdown: Tracking Progress on Health and Climate Change", an international collaboration across disciplines that include climate, geography, epidemiology, occupation health, and economics.

DISCUSSION

This research in practice article is a reflective narrative documenting how we have developed CCIEVIs as a discrete set of quantifiable indicators that are updated annually to provide the most recent picture of climate change's impacts on human health. In our experience, the main challenge was to define globally relevant indicators that also have local relevance and as such can support decision making across multiple spatial scales. We found a hazard, exposure, and vulnerability framework to be effective in this regard. We here describe how we used such a framework to define CCIEVIs based on both data availability and the indicators' relevance to climate change and human health. We also report on how CCIEVIs have been improved and added to, detailing the underlying data and methods, and in doing so provide the defining quality criteria for Lancet Countdown CCIEVIs.

CONCLUSIONS

Our experience shows that CCIEVIs can effectively contribute to a world-wide monitoring system that aims to track, communicate, and harness evidence on climate-induced health impacts towards effective intervention strategies. An ongoing challenge is how to improve CCIEVIs so that the description of the linkages between climate change and human health can become more and more comprehensive.

Acute critical thermal maximum does not predict chronic incremental thermal maximum in Atlantic salmon (Salmo salar)

Atlantic salmon is an important aquaculture species farmed in ocean net-pens and therefore subjected to changing environmental conditions, including rising temperatures. This creates a need for research on the thermal tolerance of this species for the future of sustainable aquaculture. We investigated the thermal tolerance of individually tagged Atlantic salmon post-smolts subjected sequentially to two common high-temperature challenges: critical thermal maximum (CTmax) followed by incremental thermal maximum (ITmax). Our goals were (1) to determine whether CTmax can predict ITmax for individual fish, and (2) to examine connections between various body size (mass, length, condition factor), cardiac (absolute and relative ventricle mass) and blood (hematocrit) metrics and thermal tolerance. We found no relationship between CTmax and ITmax. This is of concern because CTmax, which is a quick and easy test, is often used to predict upper lethal limits in fish despite not using real-world rates of temperature increase and not using death as the experimental endpoint (unlike ITmax). Also, some metrics which correlated in one direction with CTmax had the opposite correlation with ITmax. For instance, smaller fish or fish with smaller ventricles had a higher CTmax but a lower ITmax than larger fish or fish with larger ventricles. Taken together, these results highlight the need to take care when using acute thermal tolerance tests to predict real-world responses to rising temperatures.

Using Food Webs and Metabolic Theory to Monitor, Model, and Manage Atlantic Salmon—A Keystone Species Under Threat

Populations of Atlantic salmon are crashing across most of its natural range: understanding the underlying causes and predicting these collapses in time to intervene effectively are urgent ecological and socioeconomic priorities. Current management techniques rely on phenomenological analyses of demographic population time-series and thus lack a mechanistic understanding of how and why populations may be declining. New multidisciplinary approaches are thus needed to capitalize on the long-term, large-scale population data that are currently scattered across various repositories in multiple countries, as well as marshaling additional data to understand the constraints on the life cycle and how salmon operate within the wider food web. Here, we explore how we might combine data and theory to develop the mechanistic models that we need to predict and manage responses to future change. Although we focus on Atlantic salmon—given the huge data resources that already exist for this species—the general principles developed here could be applied and extended to many other species and ecosystems.

Protein-Sourced Feedstuffs for Aquatic Animals in Nutrition Research and Aquaculture

Aquatic animals have particularly high requirements for dietary amino acids (AAs) for health, survival, growth, development, and reproduction. These nutrients are usually provided from ingested proteins and may also be derived from supplemental crystalline AA. AAs are the building blocks of protein (a major component of tissue growth) and, therefore, are the determinants of the growth performance and feed efficiency of farmed fish. Because protein is generally the most expensive ingredient in aqua feeds, much attention has been directed to ensure that dietary protein feedstuff is of high quality and cost-effective for feeding fish, crustaceans, and other aquatic animals worldwide. Due to the rapid development of aquaculture worldwide and a limited source of fishmeal (the traditionally sole or primary source of AAs for aquatic animals), alternative protein sources must be identified to feed aquatic animals. Plant-sourced feedstuffs for aquatic animals include soybean meal, extruded soybean meal, fermented soybean meal, soybean protein concentrates, soybean protein isolates, leaf meal, hydrolyzed plant protein, wheat, wheat hydrolyzed protein, canola meal, cottonseed meal, peanut meal, sunflower meal, peas, rice, dried brewers grains, and dried distillers grains. Animal-sourced feedstuffs include fishmeal, fish paste, bone meal, meat and bone meal, poultry by-product meal, chicken by-product meal, chicken visceral digest, spray-dried poultry plasma, spray-dried egg product, hydrolyzed feather meal, intestine-mucosa product, peptones, blood meal (bovine or poultry), whey powder with high protein content, cheese powder, and insect meal. Microbial sources of protein feedstuffs include yeast protein and single-cell microbial protein (e.g., algae); they have more balanced AA profiles than most plant proteins for animal feeding. Animal-sourced ingredients can be used as a single source of dietary protein or in complementary combinations with plant and microbial sources of proteins. All protein feedstuffs must adequately provide functional AAs for aquatic animals.

Disentangling tropicalization and deborealization in marine ecosystems under climate change

As climate change accelerates, species are shifting poleward and subtropical and tropical species are colonizing temperate environments.^1-3 A popular approach for characterizing such responses is the community temperature index (CTI), which tracks the mean thermal affinity of a community. Studies in marine,⁴ freshwater,⁵ and terrestrial⁶ ecosystems have documented increasing CTI under global warming. However, most studies have only linked increasing CTI to increases in warm-affinity species. Here, using long-term monitoring of marine fishes across the Northern Hemisphere, we decomposed CTI changes into four underlying processes-tropicalization (increasing warm-affinity), deborealization (decreasing cold-affinity), borealization (increasing cold-affinity), and detropicalization (decreasing warm-affinity)-for which we examined spatial variability and drivers. CTI closely tracked changes in sea surface temperature, increasing in 72% of locations. However, 31% of these increases were primarily due to decreases in cold-affinity species, i.e., deborealization. Thus, increases in warm-affinity species were prevalent, but not ubiquitous. Tropicalization was stronger in areas that were initially warmer, experienced greater warming, or were deeper, while deborealization was stronger in areas that were closer to human population centers or that had higher community thermal diversity. When CTI (and temperature) increased, species that decreased were more likely to be living closer to their upper thermal limits or to be commercially fished. Additionally, warm-affinity species that increased had smaller body sizes than those that decreased. Our results show that CTI changes arise from a variety of underlying community responses that are linked to environmental conditions, human impacts, community structure, and species characteristics.

Developing an Ensembled Machine Learning Prediction Model for Marine Fish and Aquaculture Production

The fishing industry is identified as a strategic sector to raise domestic protein production and supply in Malaysia. Global changes in climatic variables have impacted and continue to impact marine fish and aquaculture production, where machine learning (ML) methods are yet to be extensively used to study aquatic systems in Malaysia. ML-based algorithms could be paired with feature importance, i.e., (features that have the most predictive power) to achieve better prediction accuracy and can provide new insights on fish production. This research aims to develop an ML-based prediction of marine fish and aquaculture production. Based on the feature importance scores, we select the group of climatic variables for three different ML models: linear, gradient boosting, and random forest regression. The past 20 years (2000–2019) of climatic variables and fish production data were used to train and test the ML models. Finally, an ensemble approach named voting regression combines those three ML models. Performance matrices are generated and the results showed that the ensembled ML model obtains R2 values of 0.75, 0.81, and 0.55 for marine water, freshwater, and brackish water, respectively, which outperforms the single ML model in predicting all three types of fish production (in tons) in Malaysia.

Mixed-stock analysis using Rapture genotyping to evaluate stock-specific exploitation of a walleye population despite weak genetic structure

Mixed-stock analyses using genetic markers have informed fisheries management in cases where strong genetic differentiation occurs among local spawning populations, yet many fisheries are supported by multiple, weakly differentiated stocks. Freshwater fisheries exemplify this problem, with many populations supported by multiple stocks of young evolutionary age and isolated across small spatial scales. Consequently, attempts to conduct genetic mixed-stock analyses of inland fisheries have often been unsuccessful. Advances in genomic sequencing offer the ability to discriminate among populations with weak population structure, providing the necessary resolution to conduct mixed-stock assignment among previously indistinguishable stocks. We used genomic data to conduct a mixed-stock analysis of eastern Lake Erie's commercial and recreational walleye (Sander vitreus) fisheries and estimate the relative harvest of weakly differentiated stocks (pairwise F ST < 0.01). Using RAD-capture (Rapture), we sequenced and genotyped individuals from western and eastern basin local spawning stocks at 12,081 loci with 95% reassignment accuracy, which was not possible in the past using microsatellite markers. A baseline assessment of 395 walleye from 11 spawning stocks identified three reporting groups and refined previous assessments of gene flow among walleye stocks. Genetic assignment of 1,075 walleye harvested in eastern Lake Erie's recreational and commercial fisheries indicated that western basin stocks constituted the majority of harvest during the peak walleye fishing season (July-September), whereas eastern basin individuals comprised much of the early season harvest (May-June). Clear spatial structure in harvest composition existed; catches in more easterly sites contained more individuals of eastern basin origin than did more westerly sites. Our study provides important stock contribution estimates for Lake Erie fishery management and demonstrates the utility of genomic data to facilitate mixed-stock analysis in exploited fish populations having weak population structure or limited existing genetic resources.

Inferring ecosystem networks as information flows

The detection of causal interactions is of great importance when inferring complex ecosystem functional and structural networks for basic and applied research. Convergent cross mapping (CCM) based on nonlinear state-space reconstruction made substantial progress about network inference by measuring how well historical values of one variable can reliably estimate states of other variables. Here we investigate the ability of a developed optimal information flow (OIF) ecosystem model to infer bidirectional causality and compare that to CCM. Results from synthetic datasets generated by a simple predator-prey model, data of a real-world sardine-anchovy-temperature system and of a multispecies fish ecosystem highlight that the proposed OIF performs better than CCM to predict population and community patterns. Specifically, OIF provides a larger gradient of inferred interactions, higher point-value accuracy and smaller fluctuations of interactions and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document}α-diversity including their characteristic time delays. We propose an optimal threshold on inferred interactions that maximize accuracy in predicting fluctuations of effective \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document}α-diversity, defined as the count of model-inferred interacting species. Overall OIF outperforms all other models in assessing predictive causality (also in terms of computational complexity) due to the explicit consideration of synchronization, divergence and diversity of events that define model sensitivity, uncertainty and complexity. Thus, OIF offers a broad ecological information by extracting predictive causal networks of complex ecosystems from time-series data in the space-time continuum. The accurate inference of species interactions at any biological scale of organization is highly valuable because it allows to predict biodiversity changes, for instance as a function of climate and other anthropogenic stressors. This has practical implications for defining optimal ecosystem management and design, such as fish stock prioritization and delineation of marine protected areas based on derived collective multispecies assembly. OIF can be applied to any complex system and used for model evaluation and design where causality should be considered as non-linear predictability of diverse events of populations or communities.

Climate Change Effects on Aquaculture Production: Sustainability Implications, Mitigation, and Adaptations

Aquaculture continues to significantly expand its production, making it the fastest-growing food production sector globally. However, the sustainability of the sector is at stake due to the predicted effects of climate change that are not only a future but also a present reality. In this paper, we review the potential effects of climate change on aquaculture production and its implications on the sector's sustainability. Various elements of a changing climate, such as rising temperatures, sea-level rise, diseases and harmful algal blooms, changes in rainfall patterns, the uncertainty of external inputs supplies, changes in sea surface salinity, and severe climatic events have been discussed. Furthermore, several adaptation options have been presented as well as some gaps in existing knowledge that require further investigations. Overall, climate change effects and implications on aquaculture production sustainability are expected to be both negative and positive although, the negative effects outweigh the positive ones. Adapting to the predicted changes in the short-term while taking mitigation measures in the long-term could be the only way toward sustaining the sector's production. However, successful adaptation will depend on the adaptive capacity of the producers in different regions of the world.

The quiet crossing of ocean tipping points

Anthropogenic climate change profoundly alters the ocean's environmental conditions, which, in turn, impact marine ecosystems. Some of these changes are happening fast and may be difficult to reverse. The identification and monitoring of such changes, which also includes tipping points, is an ongoing and emerging research effort. Prevention of negative impacts requires mitigation efforts based on feasible research-based pathways. Climate-induced tipping points are traditionally associated with singular catastrophic events (relative to natural variations) of dramatic negative impact. High-probability high-impact ocean tipping points due to warming, ocean acidification, and deoxygenation may be more fragmented both regionally and in time but add up to global dimensions. These tipping points in combination with gradual changes need to be addressed as seriously as singular catastrophic events in order to prevent the cumulative and often compounding negative societal and Earth system impacts.

Thermal stress-induced oxidative damages in the liver and associated death in fish, Labeo rohita

Fish mortality generally occurs during extreme summer temperatures in India which are apprehended to be more frequent in near future and may reduce the fish population, particularly in closed aquatic systems. This present study is conducted with the objectives to find out heat shock and associated oxidative stress responses that occurred in selected fish Labeo rohita due to extremely high water temperature (treated, 37-38 °C against control, 28-30 °C) exposure for 2 weeks. Calculated mortality was 30% during the experimental period. The results revealed the biomolecules associated with both the anti-oxidative response (reduced glutathione in serum, liver, muscle; catalase activity in liver, muscle; superoxide dismutase gene expression in the liver) and the heat shock response (hsp70 gene expression in the liver) were elevated under thermal stress. Pro-inflammatory responses (expression of complement protein 3, glyceraldehyde 3-phosphate dehydrogenase in the liver) and oxidative damages (lipid peroxidation in all studied tissue and DNA fragmentation in the liver) were more under thermal stress. Extreme thermal stress induced by partial lethal temperature exposure in this study led to the activation of both the heat shock response and the anti-oxidative response. However, these responses were not elicited to the level so that they can protect from oxidative damages and inflammation in the liver of all the studied fish that caused partial mortality in fish. Thermal stress-induced hepatotoxicity caused fish death which was documented for the first time in freshwater fish.

Phytoplankton taxonomic and functional diversity patterns across a coastal tidal front

Oceanic physics at fine scale; e.g. eddies, fronts, filaments; are notoriously difficult to sample. However, an increasing number of theoretical approaches hypothesize that these processes affect phytoplankton diversity which have cascading effects on regional ecosystems. In 2015, we targeted the Iroise Sea (France) and evidenced the setting up of the Ushant tidal front from the beginning of spring to late summer. Seawater samples were taken during three sampling cruises and DNA-barcoding allowed us to investigate patterns of eukaryotic phytoplankton diversity across this front. First focusing on patterns of taxonomic richness, we evidenced that the front harbored a hotspot of eukaryotic phytoplankton diversity sustained throughout summer. We then detail the ecological processes leading to the formation of this hotspot by studying shifts in community composition across the Iroise Sea. Physical mixing mingled the communities surrounding the front, allowing the formation of a local ecotone, but it was cycles of disturbances and nutrient inputs over the front that allowed a decrease in competitive exclusion, which maintained a higher diversity of rare phytoplankton taxa. These processes did not select a specific ecological strategy as inferred by a trait approach coupled to our taxonomic approach. Instead the front favored higher richness within widespread strategies, resulting in functional redundancy. We detail how fine-scale ocean physics affect phytoplankton diversity and suppose that this interplay is a major control on regional ecosystems.

Combined Effects of Elevated Temperature and Crude Oil Pollution on Oxidative Stress and Apoptosis in Sea Cucumber (Apostichopus japonicus, Selenka)

Currently, global climate change and oil pollution are two main environmental concerns for sea cucumber (Apostichopus japonicus) aquaculture. However, no study has been conducted on the combined effects of elevated temperature and oil pollution on sea cucumber. Therefore, in the present study, we treated sea cucumber with elevated temperature (26 °C) alone, water-accommodated fractions (WAF) of Oman crude oil at an optimal temperature of 16 °C, and Oman crude oil WAF at an elevated temperature of 26 °C for 24 h. Results showed that reactive oxygen species (ROS) level and total antioxidant capacity in WAF at 26 °C treatment were higher than that in WAF at 16 °C treatment, as evidenced by 6.03- and 1.31-fold-higher values, respectively. Oxidative damage assessments manifested that WAF at 26 °C treatment caused much severer oxidative damage of the biomacromolecules (including DNA, proteins, and lipids) than 26 °C or WAF at 16 °C treatments did. Moreover, compared to 26 °C or WAF at 16 °C treatments, WAF at 26 °C treatment induced a significant increase in cellular apoptosis by detecting the caspase-3 activity. Our results revealed that co-exposure to elevated temperature and crude oil could simulate higher ROS levels and subsequently cause much severer oxidative damage and cellular apoptosis than crude oil alone on sea cucumber.

Resilience to Climate Change in Industrial Shrimping in Bangladesh: Assessing the Comparative Role of the Stakeholders

Over the last few decades, the global shrimp aquaculture industry has grown considerably and experienced important transformations in coastal regions in the Global South. However, despite being a major contributor to GDP and export earnings of the country, the shrimp industry in Bangladesh is not yet fully developed. This important sector is often plagued by numerous environmental challenges including frequent climate disasters. To address local climate perturbations, the shrimping industry undertakes a wide range of individual, communal, and institutional level resilience activities. Drawing on primary data collected through ethnography and qualitative interviews in three shrimping communities, this paper examines the nature, effects, and efficacy of resilience strategies adopted by various stakeholders in the shrimp industry in coastal Bangladesh. This research demonstrates that there is a clearly visible resilience gradient in the shrimp aquaculture industry in Bangladesh: individual shrimp farmers and households play a pivotal role in resilience enhancement, while other stakeholders including community, state, and civil society organizations have moderate-to-little involvement in aiding resilience in the sector. The study offers a series of recommendations for resilience to climate change.