Climate change impacts on fisheries

Bacterial Community Composition and Its Relationship with Environmental Factors in the Artificial Reef Area for Marine Ranching in Changhai County

In this study, samples were collected from different types of artificial fish reefs and prevention and control areas in the sea areas of the northern part of Da Changshan Island and the northeastern part of Xiao Changshan Island in the North Yellow Sea. The purpose is to compare the differences in the bacterial communities among different regions, determine the impacts of environmental factors on the bacterial communities, and evaluate the ecological effects of artificial fish reefs on the marine bacterial communities. We obtained a total of 2,128,186 effective sequences and 4321 bacterial operational taxonomic units (OTUs), which were classified into 14 phyla and 76 genera. Proteobacteria were the most abundant phylum across the 32 samples, followed by Bacteroidetes. We found that all samples from the deep-sea control area exhibited the highest bacterial richness. In addition, all samples from the shallow-water concrete reef exhibited high community richness. The distribution of bacterial communities showed differences among different regions. In two specific sea areas, the bacteria in the sediment samples exhibited particularly remarkable characteristics of high diversity. Importantly, environmental factors significantly influence bacterial communities. In seawater samples, salinity (Sal) and dissolved oxygen (DO) were the primary factors affecting bacterial communities. Furthermore, grain size (GS) emerged as the most critical physicochemical factor influencing bacterial communities in sediment. This study compared the characteristics of bacterial communities in different types of artificial reefs and control areas in two marine ranches and revealed the main environmental factors affecting the bacterial communities. This is of great significance for protecting biodiversity and evaluating the ecological effects of artificial reef placement.

Post-Fishing Ban Period: The Fish Diversity and Community Structure in the Poyang Lake Basin, Jiangxi Province, China

Between 2022 and 2023, four systematic fish surveys were carried out in the Poyang Lake basin (PLB), capturing 49,192 fish (7017 kg) and identifying 120 species from 10 orders, 21 families, and 70 genera. Cypriniformes were the most dominant, accounting for 79 species. The spring and autumn surveys collected 25,734 and 23,458 individuals, respectively, with corresponding biomasses of 3978 kg and 3038 kg. Dominant species (IRI > 1000) in the study area included Hemiculter leucisculus, Megalobrama skolkovii, Hypophthalmichthys molitrix, and Aristichthys nobilis. Additionally, critically endangered species such as Ochetobius elongatus, Myxocyprinus asiaticus, and Acipenser sinensis as well as exotic species like Cirrhinus mrigala and euryhaline species like Cynoglossus gracilis and Hyporhamphus intermedius were observed. Hierarchical clustering grouped the survey stations into three distinct areas (PYS, XBMS, and XBUS), with the ANOSIM analysis showing highly significant differences (R = 0.893, p < 0.01). Redundancy analysis (RDA) indicated that in spring, total phosphorus (TP) and temperature were the main factors influencing variability (80.50%), while in autumn, temperature, oil, and pH were the key factors (75.20%). This study emphasizes the predictable changes in fish community composition caused by environmental gradients and highlights the need for ongoing monitoring to effectively manage and protect the ecosystem, particularly in the post-fishing ban period.

Genetic Mechanism Analysis Related to Cold Tolerance of Red Swamp Crayfish, Procambarus clarkii

In China, the red swamp crayfish (Procambarus clarkii), a notorious invasive species, has become an important economic freshwater species. In order to compare the genetic diversity and population structure of crayfish from northern and southern China, we collected 60 crayfish individuals from 4 crayfish populations in northern China and 2 populations in southern China for sequencing using the 2b-RAD technique. Additionally, the whole genome sequence information obtained by 2b-RAD of 90 individuals from 2 populations in northern China and 7 populations in southern China were downloaded from NCBI. After quality control, a total of 25,371 SNPs were detected from approximately 54.22 billion raw reads. Based on these SNPs, high genetic diversity was observed in the 15 crayfish populations in China. The pairwise FST values indicated that there was a large genetic differentiation of crayfish populations in northern and southern China. Despite common genetic backgrounds, due to geographical barriers, genetic divergence has been observed in northern and southern China crayfishes. The principal component analysis in combination with Admixture and Neighbor-Joining tree analysis showed that the crayfish fell into two clusters corresponding to geographical regions. The integrated analysis of whole genome and transcriptome data showed that two genes (CETN4 and CPEB2) might play important roles during crayfish resistance to a cold environment. This study reveals the genetic differentiation of crayfish populations in northern and southern China and provides clues to the genetic mechanism related to cold adaptation.

Elephant seals as ecosystem sentinels for the northeast Pacific Ocean twilight zone

The open ocean twilight zone holds most of the global fish biomass but is poorly understood owing to difficulties of measuring subsurface ecosystem processes at scale. We demonstrate that a wide-ranging carnivore-the northern elephant seal-can serve as an ecosystem sentinel for the twilight zone. We link ocean basin-scale foraging success with oceanographic indices to estimate twilight zone fish abundance five decades into the past, and into the future. We discovered that a small variation in maternal foraging success amplified into larger changes in offspring body mass and enormous variation in first-year survival and recruitment. Worsening oceanographic conditions could shift predator population trajectories from current growth to sharp declines. As ocean integrators, wide-ranging predators could reveal impacts of future anthropogenic change on open ocean ecosystems.

Studying Chinook salmon in northern river ecosystems through ecological methods and Indigenous, Teslin Tlingit knowledge

In this study, we examined Pacific salmon decline and ecosystem function through Western science and Indigenous, Teslin Tlingit knowledge. We tested relationships of riparian tree growth and nitrogen composition at the limit of Pacific salmon distribution on the Teslin Tlingit Council (TTC) Traditional Territory in Southern Yukon, studied ecosystem roles of salmon and population declines in the area, and the interactions of these processes. Within sites, tree growth was positively related to salmon escapement at all salmon-bearing sites and not at the negative (salmon-free) control site. Mean δ15N was significantly higher at salmon-bearing sites compared to the negative control, showing similar patterns to comparable studies. Between sites, mean site tree growth did not show a clear response to salmon. Interviews conducted with Teslin Tlingit knowledge holders revealed measures of a healthy salmon run and large population declines that have negatively impacted local ecosystems (particularly bears, key to delivering salmon nutrients to terrestrial ecosystems) and human wellbeing on the Traditional Territory. Although this study was limited by available sites and data, we demonstrate that the health of salmon and riparian forests on the Traditional Territory are deeply linked, and the importance of considering multiple ways of knowing to improve ecological research.

What's going to be on the menu with global environmental changes?

Ongoing anthropogenic change is altering the planet at an unprecedented rate, threatening biodiversity, and ecosystem functioning. Species are responding to abiotic pressures at both individual and population levels, with changes affecting trophic interactions through consumptive pathways. Collectively, these impacts alter the goods and services that natural ecosystems will provide to society, as well as the persistence of all species. Here, we describe the physiological and behavioral responses of species to global changes on individual and population levels that result in detectable changes in diet across terrestrial and marine ecosystems. We illustrate shifts in the dynamics of food webs with implications for animal communities. Additionally, we highlight the myriad of tools available for researchers to investigate the dynamics of consumption patterns and trophic interactions, arguing that diet data are a crucial component of ecological studies on global change. We suggest that a holistic approach integrating the complexities of diet choice and trophic interactions with environmental drivers may be more robust at resolving trends in biodiversity, predicting food web responses, and potentially identifying early warning signs of diversity loss. Ultimately, despite the growing body of long-term ecological datasets, there remains a dearth of diet ecology studies across temporal scales, a shortcoming that must be resolved to elucidate vulnerabilities to changing biophysical conditions.

Methodological guidelines for the calculation of a Water-Energy-Food nexus index for seafood products

Indicators from life cycle assessment methodologies (i.e., footprints) have emerged as useful tools for identifying and communicating the environmental impacts of a system thanks to they are accessible and intuitive and easy to understand to non-expert public. However, the focus on a single environmental problem is one of their main drawbacks. From this idea arises the concept of Water-Energy-Food (WEF) nexus, with the aim of raising awareness of the connections between the universal rights to water supply, energy security and food provision. Regarding the latter, the fisheries sector stands out as a fundamental pillar in the fight against malnutrition. In this sense, the European project "blue growth" aims to ensure that the development of the marine sector is not linked to the degradation of its ecosystems. However, although producers and authorities are willing to communicate the sustainability of products, there is still no standard methodology for reporting it. With the purpose of remedying this current situation, this paper aims to provide technical guidance to calculate a single WEF nexus index for ecolabelling seafood products in the European framework (Atlantic area). Therefore, through this, it is expected to create a useful communication channel between producers and consumers through an easy-to-read ecolabel. Nonetheless, certain aspects, such as the footprints selected or the calculation procedures selected have to be reconsidered to refine the methodology proposed, apart from broadening the approach to other food sectors with the aim that the proposed eco-certification can be present in major supply and retail chains.

Understanding the temporal dynamics of estimated environmental niche hypervolumes for marine fishes

Understanding how species respond to the environment is essential in ecology, evolution, and conservation. Abiotic factors can influence species responses and the multi-dimensional space of abiotic factors that allows a species to grow represents the environmental niche. While niches are often assumed to be constant and robust, they are most likely changing over time and estimation can be influenced by population biology, sampling intensity, and computation methodology. Here, we used a 12-year time series of survey data to fit annual ecological niche models (ENMs) for 10 marine fish species by using two regression and two machine learning algorithms to evaluate the variation and differentiation of environmental niches. Fitted ENMs were used to develop multi-dimensional annual and pooled hypervolumes that were evaluated over time and across ENM algorithms, species, and years by computing volume, distance, and dissimilarity metrics for each annual estimated niche. We then investigated potential drivers of estimated hypervolume dynamics including species abundance, species occurrence, sampling effort, salinity, red tides severity, and algorithm. Overall, our results revealed that estimated niches varied over time and across ENM, species, and algorithms. Niche estimation was influenced over time by multiple factors suggesting high complexity on niche dynamics interpretation. Species with high occurrence tended to have a closer representation of the pooled niche and years with higher abundance tended to produce niche expansion. ENM algorithm, sampling effort, seawater salinity, and red tides explained the deviations from the pooled niche. Greater sampling effort led to more comprehensive and complete estimates of species niches. High red tides severity triggered niche contraction. Our results emphasize the predictable effects of population, sampling, and environment on species niche estimation and interpretation, and that each should be considered when performing and interpreting ecological niche analyses. Our niche analysis approach may contribute to effectively quantifying and assessing niche dynamics.

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.

Evaluation of Pollution Status and Detection of the Reason for the Death of Fish in Chamo Lake, Ethiopia

Chamo Lake is the third largest rift valley lake and one of the major economic sources for the communities in the Southern region, Ethiopia. The lake's quality is deteriorating due to the untreated wastewater, and sediment inflow resulting in the death of fish was observed during the dry season. The research aims to determine the water quality status using water quality indices, in addition to identifying the reason for the death of fish in the dry season in Chamo Lake. The water samples were drawn from 5 sampling points by composite sampling method during the dry and wet seasons of the year, and we analyzed 22 water quality parameters. Ammonia (14–23.6 mg/l), phosphates (0.30–1.10 mg/l), BOD (25.32–60 mg/l), COD (40–160 mg/l), and chlorophyll (19.64–31.87 μg/L) concentrations were above the permissible limits, and DO (5.20–6.70 mg/l) was below the acceptable limit in the lake as per EPA standards concerning temperature. The values of both the water quality indices of CCMEWQI (13.90–18.40) and NSFWQI (38.59–49.63) indicated that the water quality was “poor” and “bad,” respectively. The death of fish might be due to high concentrations of ammonia and nutrients in the dry season.

Welfare impact of climate change on capture fisheries in Vietnam

Fisheries are forecasted to shrink in the tropics due to climate change. In Vietnam, fisheries are a pro-poor economic sector and essential nutrition source; however, welfares of producers and consumers in the climate change context are not well understood. While most studies focus on the gains or losses of total products and revenues, this paper pays additional attention to the changes in surpluses of market players in the long run. A combination of the production function, demand and supply functions, and partial equilibrium analysis is employed to measure the production and welfare impacts based on time series data from 1976 to 2018 and a Vietnam household living standards survey in 2018. The results show that relative to the present, catch yield is likely to reduce 35%-45% by mid-century and 45%-80% by the end of the century. Consumers may lose their surplus of 7-9 billion USD (PPP, 2018) by 2035 and 10-18 billion USD by 2065 due to supply reduction, while producers may gain additional profit of 3.5-4.5 billion USD by 2035 and 5-9 billion USD by 2065 owing to a price increase. The research findings suggest that Vietnam could impose measures to limit capture effort, as set out in the Law of Fisheries 2017, without harming fisher welfare. The expansion of aquaculture could reduce the gap between supply and demand of wild fish to mitigate consumer welfare loss; however, this impact is still ambiguous.

Meridionalization as a Possible Resource for Fisheries: The Case Study of Caranx rhonchus Geoffroy Saint-Hilaire, 1817, in Southern Italian Waters

Climate change affects the shift range distribution of species, especially among mobile species, and this phenomenon can alter ecosystems and impacts human activities. Fishing is an anthropic activity that undergoes the effect not only of the introduction and increase of non-native species but also of native thermophilic ones. Some of these species can become a commercially exploitable resource. However, this information is often obscured by the negative effects these species can cause to the environment. We investigated how the thermophilic species Caranx rhonchus, neglected in Italy, could become a relevant resource. We studied the nutritional profile and the presence of heavy metal contamination and compared these traits with those of a similar common Mediterranean species, namely Trachurus trachurus. The proximate composition was determined following the AOAC procedure, while the fatty acid profile was determined by GC/MS, and the mineral component was obtained by mass spectrometer (ICP-MS). Caranx rhonchus is a nutritionally good species, although it is little consumed and exploited. Increasing the market supply with new commercially exploitable emerging species would benefit local communities and the environment. Therefore, it is necessary to investigate how a shift of the range caused by climate change can provide benefits within the human dimension.

Identification of Genes Related to Cold Tolerance and Novel Genetic Markers for Molecular Breeding in Taiwan Tilapia (Oreochromis spp.) via Transcriptome Analysis

Taiwan tilapia is one of the primary species used in aquaculture practices in Taiwan. However, as a tropical fish, it is sensitive to cold temperatures that can lead to high mortality rates during winter months. Genetic and broodstock management strategies using marker-assisted selection and breeding are the best tools currently available to improve seed varieties for tilapia species. The purpose of this study was to develop molecular markers for cold stress-related genes using digital gene expression analysis of next-generation transcriptome sequencing in Taiwan tilapia (Oreochromis spp.). We constructed and sequenced cDNA libraries from the brain, gill, liver, and muscle tissues of cold-tolerance (CT) and cold-sensitivity (CS) strains. Approximately 35,214,833,100 nucleotides of raw sequencing reads were generated, and these were assembled into 128,147 unigenes possessing a total length of 185,382,926 bp and an average length of 1446 bp. A total of 25,844 unigenes were annotated using five protein databases and Venny analysis, and 38,377 simple sequence repeats (SSRs) and 65,527 single nucleotide polymorphisms (SNPs) were identified. Furthermore, from the 38-cold tolerance-related genes that were identified using differential gene expression analysis in the four tissues, 13 microsatellites and 37 single nucleotide polymorphism markers were identified. The results of the genotype analysis revealed that the selected markers could be used for population genetics. In addition to the diversity assessment, one of the SNP markers was determined to be significantly related to cold-tolerance traits and could be used as a molecular marker to assist in the selection and verification of cold-tolerant populations. The specific genetic markers explored in this study can be used for the identification of genetic polymorphisms and cold tolerance traits in Taiwan tilapia, and they can also be used to further explore the physiological and biochemical molecular regulation pathways of fish that are involved in their tolerance to environmental temperature stress.

Future intensification of extreme Aleutian low events and their climate impacts

Extreme Aleutian Low (AL) events have been associated with major ecosystem reorganisations and unusual weather patterns in the Pacific region, with serious socio-economic consequences. Yet, their future evolution and impacts on atmosphere-ocean interactions remain uncertain. Here, a large ensemble of historical and future runs from the Community Earth System Model is used to investigate the evolution of AL extremes. The frequency and persistence of AL extremes are quantified and their connection with climatic variables is examined. AL extremes become more frequent and persistent under the RCP8.5 scenario, associated with changes in precipitation and air temperature patterns over North America. Future changes in AL extremes also increase the variability of the sea surface temperature and net heat fluxes in the Kuroshio Extension, the most significant heat and energy flux region of the basin. The increased frequency and persistence of future AL extremes may potentially cause substantial changes in fisheries and ecosystems of the entire Pacific region as a knock-on effect.

Climate change/variability and hydrological modelling studies in Zimbabwe: a review of progress and knowledge gaps

This paper reviews developments in climate science and hydrological modelling studies in Zimbabwe over the past 29 years in an effort to expose knowledge gaps within this research domain. We initially give a global and regional overview and then follow a systematic thematic approach in reviewing specifically online published, peer-reviewed journal articles on climate change/variability and hydrological modelling in Zimbabwe. The state and progress towards advanced integrated climate and hydrological modelling research are assessed, tracking benchmarks in the research methodologies (tools and techniques) used therein including geographic information systems and remote sensing. We present descriptive summaries of key findings, highlighting the main study themes (categories) and general conclusions arising from these studies while examining their implications for future climate and hydrological modelling research in Zimbabwe. Challenges associated with climate and hydrological modelling research in Zimbabwe are also briefly discussed and the main knowledge gaps in terms of research scope and methodologies employed in the reviewed studies also exposed. We conclude by presenting plausible potential areas of focus in updating and advancing scientific knowledge to better understand the climate-land use-hydrology nexus in Zimbabwe. While this paper is primarily relevant for researchers, the general findings are also important for policy-makers since it exposes potential areas for policy intervention or agenda setting in as far as climate and hydrology science research is concerned so as to effectively address pertinent questions in this domain in Zimbabwe.

Ecosystem-based fisheries management and the precautionary approach in the Indian Ocean regional fisheries management organisations

The Indian Ocean hosts a wide range of living resources including fish stocks. Marine resources contribute significantly to economies and livelihoods, and seafood is a major source of protein in Indian Ocean nations. Fisheries resources in the Indian Ocean have started showing symptoms of depletion. Several regional fisheries management organisations (RFMOs) have been established for sustainable management of the fisheries resources in the Indian Ocean region. These RFMOs were created at different times with various particular mandates, and in some cases prior to the emergence of contemporary scientific concepts and legal approaches to marine environmental governance. In this article, eight such RFMOs are studied to determine the implementation of ecosystem-based fisheries management (EBFM) and the precautionary approach (PA), which are now widely accepted norms of fisheries management and international law. This article argues that there is a mismatch between the legal and governance frameworks, and the fisheries science and management.

Observing the Global Ocean with Biogeochemical-Argo

Biogeochemical-Argo (BGC-Argo) is a network of profiling floats carrying sensors that enable observation of as many as six essential biogeochemical and bio-optical variables: oxygen, nitrate, pH, chlorophyll a, suspended particles, and downwelling irradiance. This sensor network represents today's most promising strategy for collecting temporally and vertically resolved observations of biogeochemical properties throughout the ocean. All data are freely available within 24 hours of transmission. These data fill large gaps in ocean-observing systems and support three ambitions: gaining a better understanding of biogeochemical processes (e.g., the biological carbon pump and air-sea CO₂ exchanges) and evaluating ongoing changes resulting from increasing anthropogenic pressure (e.g., acidification and deoxygenation); managing the ocean (e.g., improving the global carbon budget and developing sustainable fisheries); and carrying out exploration for potential discoveries. The BGC-Argo network has already delivered extensive high-quality global data sets that have resulted in unique scientific outcomes from regional to global scales. With the proposed expansion of BGC-Argo in the near future, this network has the potential to become a pivotal observation system that links satellite and ship-based observations in a transformative manner.