Addressing age measurement errors in fish growth estimation from length-stratified samples

Fish growth models are crucial for fisheries stock assessments and are commonly estimated using fish length-at-age data. This data is widely collected using length-stratified age sampling (LSAS), a cost-effective two-phase response-selective sampling method. The data may contain age measurement errors (MEs). We propose a methodology that accounts for both LSAS and age MEs to accurately estimate fish growth. The proposed methods use empirical proportion likelihood methodology for LSAS and the structural errors in variables methodology for age MEs. We provide a measure of uncertainty for parameter estimates and standardized residuals for model validation. To model the age distribution, we employ a continuation ratio-logit model that is consistent with the random nature of the true age distribution. We also apply a discretization approach for age and length distributions, which significantly improves computational efficiency and is consistent with the discrete age and length data typically encountered in practice. Our simulation study shows that neglecting age MEs can lead to significant bias in growth estimation, even with small but non-negligible age MEs. However, our new approach performs well regardless of the magnitude of age MEs and accurately estimates SEs of parameter estimators. Real data analysis demonstrates the effectiveness of the proposed model validation device. Computer codes to implement the methodology are provided.

A simulation-based option to assess data-limited fisheries off West African waters

Most sophisticated stock assessment models often need a large amount of data to assess fish stocks, yet this data is often lacking for most fisheries worldwide, resulting in the increasing demand for data-limited stock assessment methods. To estimate fish stock status, one class of these data-limited methods uses simply catch time series data and, in other instances, life history information or fishery characteristics. These catch-only methods (COMs) built differently are known to make assumptions about changes in fishing effort and may perform differently under various fishing scenarios. As a case study, this paper used European anchovy (Engraulis encrasicolus) caught in the northwest African waters, though very economically and ecologically important, but still unassessed. Our study investigated the performance of five COMs under different fishing scenarios using as a reference the life-history information of the European anchovy captured in this region of the Atlantic. Hence, the present study developed a simulation approach to evaluate the performance of the five COMs in inferring the stock biomass status (B/BMSY) with consideration of different fishing scenarios under prior information true to anchovy. All five COMs mostly underestimated B/BMSY throughout the simulation period, especially under constant fishing mortality, and in the last five years of the simulation during all fishing scenarios. Overall, these COMs were generally poor classifiers of stock status, however, the state-space COM (SSCOM) generally performed better than the other COMs as it showed possibilities of recovering an overfished stock. When these methods were explored using actual anchovy catch data collected in the northwest African waters, SSCOM yielded results that were deferred from the other COMs. This study being the first to assess this species' stock in this area using a suite of COMs, presents more insights into the species stock status, and what needs to be considered before scientifically putting in place management measures of the stock in the area.

Marine heatwaves are not a dominant driver of change in demersal fishes

Marine heatwaves have been linked to negative ecological effects in recent decades1,2. If marine heatwaves regularly induce community reorganization and biomass collapses in fishes, the consequences could be catastrophic for ecosystems, fisheries and human communities3,4. However, the extent to which marine heatwaves have negative impacts on fish biomass or community composition, or even whether their effects can be distinguished from natural and sampling variability, remains unclear. We investigated the effects of 248 sea-bottom heatwaves from 1993 to 2019 on marine fishes by analysing 82,322 hauls (samples) from long-term scientific surveys of continental shelf ecosystems in North America and Europe spanning the subtropics to the Arctic. Here we show that the effects of marine heatwaves on fish biomass were often minimal and could not be distinguished from natural and sampling variability. Furthermore, marine heatwaves were not consistently associated with tropicalization (gain of warm-affiliated species) or deborealization (loss of cold-affiliated species) in these ecosystems. Although steep declines in biomass occasionally occurred after marine heatwaves, these were the exception, not the rule. Against the highly variable backdrop of ocean ecosystems, marine heatwaves have not driven biomass change or community turnover in fish communities that support many of the world's largest and most productive fisheries.

Manta and devil ray species occurrence and distribution in Venezuela, assessed through fishery landings and citizen science data

Manta and devil rays (collectively mobulids) belong to the monogeneric Mobulidae, which currently comprises 10 species, including a putative third manta ray species (Mobula cf. birostris). These large planktivorous rays are distributed throughout the tropical and subtropical oceans of the world. To date, six mobulid species are reported for the western Atlantic Ocean and the Caribbean Sea, three of which had previously been reported in Venezuela (Mobula birostris, Mobula tarapacana and Mobula hypostoma). A preliminary assessment of fishery landings and citizen science data was conducted to further the scientific knowledge of mobulid species in Venezuela. Fisheries landing data were collected at Margarita Island between 2006 and 2007, and again in 2014. Data mining of internet search engines and social media platforms spanning the past two decades was also conducted. A total of 117 individuals of five mobulid species were recorded: Mobula sp. (n = 27), M. birostris (n = 36), M. tarapacana (n = 3), Mobula mobular (n = 26), Mobula thurstoni (n = 14) and M. cf. birostris (n = 11). The latter three species are the first confirmation of these species in Venezuela. The authors found no records of the previously reported M. hypostoma during this study. Although the occurrence of M. hypostoma in Venezuela remains possible because of the broad regional range of this species, its current presence in Venezuela is invalidated given the repeated misidentifications which have occurred in previous publications. The results of this study increase the number of reported mobulid ray species in Venezuela to five (excluding M. hypostoma). The overall data from juvenile manta rays and pregnant M. mobular and M. thurstoni recorded in this study, combined with the occurrence of all but one species of mobulid ray found in the western Atlantic Ocean, suggest Venezuela provides important habitat for this threatened family of rays.

The effects of environmental enrichment on hatchery-performance, smolt migration and capture rates in landlocked Atlantic salmon

Enrichment of rearing environment with natural elements has been suggested to improve the welfare and post-release survival of cultured fish. We studied the combined effects of shelter structures, periodical water flow and water level changes on pre- and post-release performance of critically endangered landlocked Atlantic salmon (Salmo salar m. sebago). Relative to standard (plain) rearing tanks, provision of enrichment improved fish condition factor and survival during the first year of rearing when most mortality was attributable to parasitic and bacterial infections. The consequent higher density in enriched tanks probably induced greater growth variation and more dorsal fin damages than found in fish of standard tanks. Possibly this was partly due to the applied changes in water level. Experimentally determined smolt migration tendency at age 3 did not differ, on average, between the rearing groups, but enriched-reared fish showed clearly less variation in total movement activity than standard-reared fish. Experimental angling in earthen ponds did not suggest divergent vulnerability between the differentially reared fish at age 3, but decreased condition during the preceding growth season increased vulnerability to fishing. Based on long-term post-stocking tag returns in large-lake fisheries, fish length at release but not rearing method affected the capture rates of fish released at age 2. When released at age 3 the fish grown in enriched environment had a higher risk to be captured with stationary gears and earlier by hook and line gears compared to standard-reared conspecifics. Earlier time of maximal smolt migration activity was associated with an increased risk of being captured. We suggest that environmental enrichment may modulate growth- and behavior-related qualities that indirectly increased the vulnerability to fishing in natural conditions but not in experimental setting. The favorable effects of enrichment on early survival encourages adopting enriched rearing practices in supportive breeding of landlocked salmon.

Twenty-year trends in antimicrobial resistance from aquaculture and fisheries in Asia

Antimicrobial resistance (AMR) is a growing threat to human and animal health. However, in aquatic animals-the fastest growing food animal sector globally-AMR trends are seldom documented, particularly in Asia, which contributes two-thirds of global food fish production. Here, we present a systematic review and meta-analysis of 749 point prevalence surveys reporting antibiotic-resistant bacteria from aquatic food animals in Asia, extracted from 343 articles published in 2000-2019. We find concerning levels of resistance to medically important antimicrobials in foodborne pathogens. In aquaculture, the percentage of antimicrobial compounds per survey with resistance exceeding 50% (P50) plateaued at 33% [95% confidence interval (CI) 28 to 37%] between 2000 and 2018. In fisheries, P50 decreased from 52% [95% CI 39 to 65%] to 22% [95% CI 14 to 30%]. We map AMR at 10-kilometer resolution, finding resistance hotspots along Asia's major river systems and coastal waters of China and India. Regions benefitting most from future surveillance efforts are eastern China and India. Scaling up surveillance to strengthen epidemiological evidence on AMR and inform aquaculture and fisheries interventions is needed to mitigate the impact of AMR globally.

Evaluating artisanal fishing of globally threatened sharks and rays in the Bay of Bengal, Bangladesh

Sharks and rays are at risk of extinction globally. This reflects low resilience to increasing fishing pressure, exacerbated by habitat loss, climate change, increasing value in a trade and inadequate information leading to limited conservation actions. Artisanal fisheries in the Bay of Bengal of Bangladesh contribute to the high levels of global fishing pressure on elasmobranchs. However, it is one of the most data-poor regions of the world, and the diversity, occurrence and conservation needs of elasmobranchs in this region have not been adequately assessed. This study evaluated elasmobranch diversity, species composition, catch and trade within the artisanal fisheries to address this critical knowledge gap. Findings show that elasmobranch diversity in Bangladesh has previously been underestimated. In this study, over 160000 individual elasmobranchs were recorded through landing site monitoring, comprising 88 species (30 sharks and 58 rays) within 20 families and 35 genera. Of these, 54 are globally threatened according to the IUCN Red List of Threatened Species, with ten species listed as Critically Endangered and 22 species listed as Endangered. Almost 98% juvenile catch (69-99% for different species) for large species sand a decline in numbers of large individuals were documented, indicating unsustainable fisheries. Several previously common species were rarely landed, indicating potential population declines. The catch pattern showed seasonality and, in some cases, gear specificity. Overall, Bangladesh was found to be a significant contributor to shark and ray catches and trade in the Bay of Bengal region. Effective monitoring was not observed at the landing sites or processing centres, despite 29 species of elasmobranchs being protected by law, many of which were frequently landed. On this basis, a series of recommendations were provided for improving the conservation status of the elasmobranchs in this region. These include the need for improved taxonomic research, enhanced monitoring of elasmobranch stocks, and the highest protection level for threatened taxa. Alongside political will, enhancing national capacity to manage and rebuild elasmobranch stocks, coordinated regional management measures are essential.

Telling the same story: Fishers and landing data reveal changes in fisheries on the Southeastern Brazilian Coast

An understanding of the effects of fishing on marine ecosystems relies on information about the conserved state of these environments. Non-conventional approaches such as the use of historical data and local ecological knowledge can provide information and help adjust our references of changes in the environment. Also, the combination of different types of data can indicate a fisheries trend that would be undetectable when evaluated separately. Here we investigated changes in fisher's perceptions regarding overexploited and new target species in artisanal fisheries in a secular fishing village of the subtropical, southeastern Brazilian coast. We identified temporal changes in landings and in the mean trophic level (MTL) of high trophic level species (≥ 3.5 and >4) over 16 years. Fishers' knowledge revealed shifts in perception associated with years of fishing practice. More experienced fishers recognized a greater number of overexploited and new target species than fishers in the beginning of their careers. Landing data has revealed declining trends of 72% for five mesopredators species. Due to the overfishing of mesopredators, there was a shift in target species, towards fish that were previously discarded. Temporal changes in landings and in the MTL metric are concordant with previous reports on the overexploitation of species caught by local fishers. Our work reveals that multiple sources of information can be combined to establish historical baselines and improve the detection of change in marine ecosystems.

Spatiotemporal patterns of variability in the abundance and distribution of winter-spawned pelagic juvenile rockfish in the California Current

Rockfish are an important component of West Coast fisheries and California Current food webs, and recruitment (cohort strength) for rockfish populations has long been characterized as highly variable for most studied populations. Research efforts and fisheries surveys have long sought to provide greater insights on both the environmental drivers, and the fisheries and ecosystem consequences, of this variability. Here, variability in the temporal and spatial abundance and distribution patterns of young-of-the-year (YOY) rockfishes are described based on midwater trawl surveys conducted throughout the coastal waters of California Current between 2001 and 2019. Results confirm that the abundance of winter-spawning rockfish taxa in particular is highly variable over space and time. Although there is considerable spatial coherence in these relative abundance patterns, there are many years in which abundance patterns are very heterogeneous over the scale of the California Current. Results also confirm that the high abundance levels of YOY rockfish observed during the 2014-2016 large marine heatwave were largely coastwide events. Species association patterns of pelagic YOY for over 20 rockfish taxa in space and time are also described. The overall results will help inform future fisheries-independent surveys, and will improve future indices of recruitment strength used to inform stock assessment models and marine ecosystem status reports.

Coastal sharks and rays in a marine protected area in southern Brazil

In southern Brazil, we investigated shark and ray capture records in an integral protection marine protection area (MPA) that allows fishing in that area. We found 10 shark and nine ray species, of which 88.5% and 66.2%, respectively, are endangered. Female adults and neonates of both sexes are abundant in the area, with records of stranding of large specimens, postcapture abortions and ovigerous capsules with fresh embryos on the beach. We suggest the application of continuous fisheries monitoring and an increase in guidelines on the capture of endangered species.

Strengths and weaknesses in the long-term sustainability of two sympatric seabreams (Argyrops spinifer and Rhabdosargus haffara, Sparidae)

Argyrops spinifer and Rhabdosargus haffara are two sympatric seabream species making important contributions to fisheries landings in the western Arabian/Persian Gulf. We identified the strengths and weaknesses in the long-term sustainability of A. spinifer and R. haffara stocks by integrating multiple sources of data, including fisheries catch and effort statistics, life history traits, scientific trawl surveys and historical length frequency distribution. Four strengths were identified in A. spinifer: wide distribution of juveniles, positive association to the network of de facto fishing exclusion areas created by hundreds of oil-gas facilities, early maturation and the existence of large and old individuals. A. spinifer suffers from two potential weaknesses: slow growth rate and higher exploitation pressure on the small-sized individuals. R. haffara, on the other hand, has a strength of having a short life span and a fast growth rate, characteristics that make it robust to unfavourable conditions. R. haffara suffers from two weaknesses: the lack of association to the oil and gas facilities, and the preference for nearshore shallow waters with stronger negative anthropogenic impacts. Identified strengths and weaknesses of these two sparids provided a preliminary assessment about their long-term sustainability, as well as a roadmap about how to develop different management strategies to meet specific objectives.

Defining mangrove-fisheries: A typology from the Perancak Estuary, Bali, Indonesia

This study develops a definition of what mangrove-fisheries can encompass, incorporating a broad range of their possible characteristics. A detailed case study was conducted to develop a typology of mangrove-fishing in the Perancak Estuary, Bali, Indonesia, using interview surveys to investigate the fishing activities associated with mangroves. This case study demonstrated the complexity that a mangrove-fishery can entail, where fishing is connected to the mangrove forest by fishers of multiple sectors, functions, locations and temporal scales. Through a comparison with other mangrove-fishing communities in Bali, it also highlighted that mangrove-fisheries are variable even when in close proximity. With particular reference to this case study, a framework was developed as a flexible tool for identifying the multiple dimensions of a mangrove-fishery in a local context. Following this framework should encourage researchers and managers to look outside of the groups of fishers traditionally expected to benefit from mangrove fishing. This will enable the development of a broader definition of mangrove-fisheries in a site specific way. Identifying the full scope of fishers that contribute to or benefit from a mangrove-fishery is the first step towards building management measures that reflect the interests of groups of fishers that may otherwise remain under-represented. This is in line with international efforts for sustainability, especially in promoting small-scale fishers’ access to sustainable resources under the UN Sustainable Development Goals.

Fishing for food: Values and benefits associated with coastal infrastructure

While there is substantial literature about the socio-cultural characteristics and values associated with recreational and commercial fisheries in the U.S., studies directed at those who ‘fish for food’—those who depend on consuming their catch to various degrees—are relatively sparse. Using qualitative data collected through 80 semi-structured interviews with fishers in the summer and fall of 2018 in Carteret County, North Carolina, this study aims to better understand the group of recreational fishers who consume their catch by describing social and cultural dimensions and values associated with fishing for food, examining the role of infrastructure in facilitating access to benefits associated with this activity, and considering how knowledge of existing licensing regulations surrounding subsistence license waivers affect this fishing community. Interviews conducted at free public fishing structures in the region revealed that fishers derive a variety of values and benefits from fishing at these sites, including access to recreation, nutrition, a social community, and mental health benefits, which were found to be negatively impacted by Hurricane Florence in September 2018. We also found an informal economy of sharing catch on- and off-site that extends the reach and benefits facilitated by public infrastructure to people beyond those using it directly. Overall, we call for conceptualizations of ‘fishing for food’ that include aspects that go beyond traditional definitions of ‘subsistence’ or ‘recreational’ fishing such as food security, access, and less obvious social and cultural motivations behind the activity. These findings are a compelling rationalization for the creation and maintenance of formal and informal fishing places locally and, by extension, in other coastal areas, given the array of benefits provided by access to these types of locations.

Can vertical separation of species in trawls be utilized to reduce bycatch in shrimp fisheries?

Several shrimp trawl fisheries use a Nordmöre sorting grid to avoid bycatch of fish. However, small fish can pass through the grid. Therefore, the retention of juvenile fish often remains an issue during shrimp trawling. We investigated the vertical distribution of deepwater shrimp (Pandalus borealis) and dominant bycatch species at the point where the Nordmöre grid section is installed. This was achieved using a separator frame which split the net vertically into three compartments of equal entry size. Our results showed that shrimp predominately follow the lower part of the trawl belly, whereas species such as redfish (Sebastes spp.), cod (Gadus morhua), polar cod (Boreogadus saida) and American plaice (Hippoglossoides platessoides) preferred the mid-section in the aft of the trawl. Haddock (Melanogrammus aeglefinus) primarily entered through the upper section of the trawl belly. Using these results, we predict that a vertical separation device installed forward of a 19 mm Nordmöre grid combined with a 35 mm codend would result in a significant reduction in bycatch with only minor loss of shrimp.

Trophic structure of a nektobenthic community exploited by a multispecific bottom trawling fishery in Northeastern Brazil

We used complementary stable isotope (SIA) and stomach content (SCA) analyses to investigate feeding relationships among species of the nektobenthic communities and the potential ecological effects of the bottom trawling of a coastal ecosystem in northeastern Brazil. Carbon (δ13C) and nitrogen (δ15N) compositions were determined for five basal sources and 28 consumers, from zooplankton to shrimp and fish species. Fishes and basal sources showed a broad range of δ15N (fishes: 6.49-14.94‰; sources: 2.58-6.79‰) and δ13C values (fishes: -23.86 to -13.71‰; sources: -24.32 to -13.53‰), while shrimps and crabs exhibited similar nitrogen and carbon ratios. Six trophic consumer groups were determined among zooplankton, crustaceans and fishes by SIA, with trophic pathways associated mostly with benthic sources. SCA results indicated a preference for benthic invertebrates, mainly worms, crabs and shrimps, as prey for the fish fauna, highlighting their importance in the food web. In overall, differences between SCA and the SIA approaches were observed, except for groups composed mainly for shrimps and some species of high δ15N values, mostly piscivorous and zoobenthivores. Given the absence of regulation for bottom trawling activities in the area, the cumulative effects of trawling on population parameters, species composition, potentially decreasing the abundance of benthic preys (e.g., shrimps, worms and crabs) may lead to changes in the trophic structure potentially affect the food web and the sustainability of the fishery.

The burden of HIV, syphilis and schistosome infection and associated factors among adults in the fishing communities in northwestern Tanzania

OBJECTIVES

To quantify the burden of HIV, syphilis and schistosome infection and associated risk factors among adults living in seven fishing communities of Lake Victoria in northwest Tanzania.

METHODS

Cross-sectional study conducted between 2015 and 2016 in the selected communities. In each community, we randomly selected a sample of adults from the general population and from three putative risk groups including the following: (i) fishermen, (ii) fish processors and traders, and (iii) women working in the recreational facilities. Participants were interviewed to obtain information about potential risk factors, and venous blood was collected for detection of HIV, syphilis and schistosome infections. We used logistic regression models to quantify the associations between potential risk factors and HIV, and also between schistosome infection and HIV.

RESULTS

We enrolled 1128 people from selected fishing communities. The overall prevalence of HIV, syphilis and schistosome infection was 14.2%, 15.6% and 83.1%, respectively. Female recreational facility workers had the highest prevalence of HIV (30.4%) and syphilis (24%). The odds of being HIV infected were generally higher in all age categories. Transactional sex was commonly reported and especially receiving gifts for sex was found to be strongly associated with HIV (adjusted OR = 2.50; 95% CI: 1.44-4.34, P = 0.008). Confirmed serological syphilis was associated with increased odds of having HIV infection. HIV was not associated with schistosome infection in a combined dataset and when we examined this separately for men and women alone.

CONCLUSIONS

We observed a high burden of HIV, syphilis and schistosome infections in the fishing communities. Targeted efforts to treat and control infections have the potential to improve health among their residents.

Assessment of fishery resources using environmental DNA: Small yellow croaker (Larimichthys polyactis) in East China Sea

Species distribution monitoring and biomass assessment are crucial for fishery management and resource conservation. However, traditional methods such as motor trawling are costly and less effective than the novel environmental DNA (eDNA) approach. This study employs eDNA approach to investigate horizontal and vertical distributions of small yellow croaker (Larimichthys polyactis), an economically important species, in the East China Sea. The analysis of 171 eDNA samples collected from 44 stations using the species-specific primers and Taqman probe suggests a presence of small yellow croaker at 28 sampling layers in 44 stations. Significant differences in croaker eDNA concentrations were revealed among sampling stations and layers, consistent with previous findings through motor-trawl capture offshore and nearshore ichthyoplakton surveys, indicating small yellow croaker exhibits strong regional distribution and layer preference. In addition, we found a high eDNA concentration of small yellow croaker in the surface waters beyond the motor-trawl prohibition line, which confirms spawning grounds have been expanded from nearshore to offshore areas. Such expansion of spawning grounds could be a response by small yellow croaker to stressors such as overfishing, climate change, and nearshore environment contamination. To identify environmental variables potentially associated with small yellow croaker presence and absence, we conducted a correlation analysis between eDNA concentration and environmental variables, and the results provide a guideline for further investigation of fishery resources in the future. In conclusion, this study demonstrates the power of the eDNA approach in monitoring small yellow croaker at extensive geographic scales. The developed protocols and the findings are expected to assist in long-term monitoring and protection programs and benefit sustainable fishery in small yellow croaker.

Physical distancing and risk of COVID-19 in small-scale fisheries: a remote sensing assessment in coastal Ghana

The novel coronavirus is predicted to have dire implications on global food systems including fisheries value chains due to restrictions imposed on human movements in many countries. In Ghana, food production, both agriculture and fisheries, is exempted from restrictions as an essential service. The enforcement of COVID-19 prevention protocols, particularly social distancing, has been widely reported in Ghana's agricultural markets whereas casual observations and media reports on fish landing sites suggest no such enforcements are in place. This study aimed to provide sound scientific evidence as a basis for informed policy direction and intervention for the artisanal fishing sector in these challenging times. We employed an unmanned aerial vehicle in assessing the risk of artisanal fishers to the pandemic using physical distancing as a proxy. From analysis of cumulative distribution function (G-function) of the nearest-neighbour distances, this study underscored crowding at all surveyed fish landing beaches, and identified potential "hotspots" for disease transmission. Aerial measurements taken at times of peak landing beach activity indicated that the highest proportion of people, representing 56%, 48%, 39% and 78% in Elmina, Winneba, Apam and Mumford respectively, were located at distances of less than one metre from their nearest neighbour. Risk of crowding was independent of the population at the landing beaches, suggesting that all categories of fish landing sites along the coast would require equal urgency and measured attention towards preventing and mitigating the spread of the disease.

Social media posts reveal the geographic range of the Critically Endangered clown wedgefish, Rhynchobatus cooki

The shark-like rays of the family Rhinidae (wedgefishes) are globally threatened with extinction. The poorly known clown wedgefish, Rhynchobatus cooki has historically been recorded only from fish markets in Singapore and Jakarta, Indonesia. Its natural geographic range has until now gone undocumented. Social media posts revealed the first wild records of this Critically Endangered species; six records were located between 2015 and 2020 from small-scale fisheries in Lingga and Singkep Islands, Indonesia. These results demonstrate the utility of social media searches to identify biogeographic records of cryptic and data-poor species.

Predicting commercial fishing vessel disasters through a novel application of the theory of man-made disasters

INTRODUCTION

Vessel disasters (e.g., sinkings, capsizings) are a leading contributor to fatalities in the U.S. commercial fishing industry. Primary prevention strategies are needed to reduce the occurrence of vessel disasters, which can only be done by developing an understanding of their causes and risk factors. If less serious vessel casualties (e.g., loss of propulsion, fire, flooding) are predictors of future disasters, then reducing vessel casualties should in turn reduce vessel disasters and the accompanying loss of life.

METHOD

This case-control study examined the association between vessel casualties and disasters using fishing vessels in Alaska during 2010-2015.

RESULTS

The findings show that vessels that experienced casualties within a preceding 10-year period were at increased odds of disaster. Other significant predictors included safety decal status and hull material. Practical Applications: The results of this analysis emphasize the importance of implementing vessel-specific preventive maintenance plans. At an industry level, specific prevention policies should be developed focusing on high-risk fleets to identify and correct a wide range of safety deficits before they have catastrophic and fatal consequences.

PeskAAS: A near-real-time, open-source monitoring and analytics system for small-scale fisheries

Small-scale fisheries are responsible for landing half of the world’s fish catch, yet there are very sparse data on these fishing activities and associated fisheries production in time and space. Fisheries-dependent data underpin scientific guidance of management and conservation of fisheries systems, but it is inherently difficult to generate robust and comprehensive data for small-scale fisheries, particularly given their dispersed and diverse nature. In tackling this challenge, we use open source software components including the Shiny R package to build PeskAAS; an adaptable and scalable digital application that enables the collation, classification, analysis and visualisation of small-scale fisheries catch and effort data. We piloted and refined this system in Timor-Leste; a small island developing nation. The features that make PeskAAS fit for purpose are that it is: (i) fully open-source and free to use (ii) component-based, flexible and able to integrate vessel tracking data with catch records; (iii) able to perform spatial and temporal filtering of fishing productivity by fishing method and habitat; (iv) integrated with species-specific length-weight parameters from FishBase; (v) controlled through a click-button dashboard, that was co-designed with fisheries scientists and government managers, that enables easy to read data summaries and interpretation of context-specific fisheries data. With limited training and code adaptation, the PeskAAS workflow has been used as a framework on which to build and adapt systematic, standardised data collection for small-scale fisheries in other contexts. Automated analytics of these data can provide fishers, managers and researchers with insights into a fisher’s experience of fishing efforts, fisheries status, catch rates, economic efficiency and geographic preferences and limits that can potentially guide management and livelihood investments.

Ecological status of a freshwater tectonic lake of the indo-burmese province: Implications for livelihood development

Tectonic lakes are among the most geologically fascinating and environmentally versatile hydrobiological systems found on the earth's surface. We conducted a study on the limnology of Tasek Lake, a tectonic lake located in the Indo-Burma Province of the South Asian region. Physico-chemical parameters of the lake's water along with its plankton were considered for the study. Their relationship was analysed by understanding their seasonal variations and through linear regression models. The water quality index (WQI), plankton diversity indices and canonical correspondence analysis (CCA) were computed. The ichthyofaunal diversity was also studied to get an insight into the lake's fishery potential. A preliminary assessment on the economic feasibility of converting Tasek Lake into a fishery was also completed. Results indicate moderate eutrophication in the lake and the plankton population is observed to be rich and abundant. The WQI value confirms the water to be of "very poor" quality. The CCA was done to analyze the relationships of physico-chemical parameters with months and seasons, and the relation between seasons and plankton assemblages. Results corroborate the results of WQI. Identified fish population suggest ample fishery potential of the lake. The economic assessment reveals that in order to maintain the ecological sustainability of the lake, it should be transformed into a recreational fishery, following a catch-and-release model. The study calls for urgent restoration of the lake so that not only its pristine ecology is survived but also its fishery potential is sustainably harnessed and local livelihood is improved.

A review of the fisheries, life history and stock structure of tropical tuna (skipjack Katsuwonus pelamis, yellowfin Thunnus albacares and bigeye Thunnus obesus) in the Indian Ocean

Skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tuna are the target species of tropical tuna fisheries in the Indian Ocean, with high commercial value in the international market. High fishing pressure over the past three decades has raised concerns about their sustainability. Understanding life history strategies and stock structure is essential to determine species resilience and how they might respond to exploitation. Here we provide a comprehensive review of available knowledge on the biology, ecology, and stock structure of tropical tuna species in the Indian Ocean. We describe the characteristics of Indian Ocean tropical tuna fisheries and synthesize skipjack, yellowfin, and bigeye tuna key life history attributes such as biogeography, trophic ecology, growth, and reproductive biology. In addition, we evaluate the available literature about their stock structure using different approaches such as analysis of fisheries data, genetic markers, otolith microchemistry and tagging, among others. Based on this review, we conclude that there is a clear lack of ocean basin-scale studies on skipjack, yellowfin and bigeye tuna life history, and that regional stock structure studies indicate that the panmictic population assumption of these stocks should be investigated further. Finally, we identify specific knowledge gaps that should be addressed with priority to ensure a sustainable and effective management of these species.

Comparative demography of commercially important species of coral grouper, Plectropomus leopardus and P. laevis, from Australia's great barrier reef and Coral Sea marine parks

Understanding the spatial and environmental variation in demographic processes of fisheries target species, such as coral grouper (Genus: Plectropomus), is important for establishing effective management and conservation strategies. Herein we compare the demography of Plectropomus leopardus and P. laevis between Australia's Great Barrier Reef Marine Park (GBRMP), which has been subject to sustained and extensive fishing pressure, and the oceanic atolls of Australia's Coral Sea Marine Park (CSMP), where there is very limited fishing for reef fishes. Coral grouper length-at-age data from contemporary and historical otolith collections across 9.4 degrees of latitude showed little difference in lifetime growth between GBRMP and CSMP regions. Plectropomus laevis populations in GBRMP reefs had significantly higher rates of total mortality than populations in the CSMP. Mean maximum lengths and mean maximum ages of P. laevis were also smaller in the GBRMP than in the CSMP, even when considering populations sampled within GBRMP no-take marine reserves (NTMRs). Plectropomus leopardus, individuals were on average smaller on fished reefs than NTMRs in the GBRMP, but all other aspects of demography were broadly similar between regions despite the negligible levels of fishing pressure in the CSMP. Similarities between regions in growth profiles and length-at-age comparisons of P. laevis and P. leopardus suggest that the environmental differences between the CSMP and the GBRMP may not have significant impacts on lifetime growth. Our results show that fishing may have influenced the demography of coral grouper on the GBR, particularly for the slower growing and longer lived species, P. laevis.

Detrital food web contributes to aquatic ecosystem productivity and rapid salmon growth in a managed floodplain

Similar to many large river valleys globally, the Sacramento River Valley has been extensively drained and leveed, hydrologically divorcing river channels from most floodplains. Today, the former floodplain is extensively managed for agriculture. Lack of access to inundated floodplains is recognized as a significant contributing factor in the decline of native Chinook Salmon (Oncorhynchus tshawytscha). We observed differences in salmon growth rate, invertebrate density, and carbon source in food webs from three aquatic habitat types-leveed river channels, perennial drainage canals in the floodplain, and agricultural floodplain wetlands. Over 23 days (17 February to 11 March, 2016) food web structure and juvenile Chinook Salmon growth rates were studied within the three aquatic habitat types. Zooplankton densities on the floodplain wetland were 53x more abundant, on average, than in the river. Juvenile Chinook Salmon raised on the floodplain wetland grew at 0.92 mm/day, 5x faster than fish raised in the adjacent river habitat (0.18 mm/day). Two aquatic-ecosystem modeling methods were used to partition the sources of carbon (detrital or photosynthetic) within the different habitats. Both modeling approaches found that carbon in the floodplain wetland food web was sourced primarily from detrital sources through heterotrophic pathways, while carbon in the river was primarily photosynthetic and sourced from in situ autotrophic production. Hydrologic conditions typifying the ephemerally inundated floodplain-shallower depths, warmer water, longer water residence times and predominantly detrital carbon sources compared to deeper, colder, swifter water and a predominantly algal-based carbon source in the adjacent river channel-appear to facilitate the dramatically higher rates of food web production observed in the floodplain. These results suggest that hydrologic patterns associated with seasonal flooding facilitate river food webs to access floodplain carbon sources that contribute to highly productive heterotrophic energy pathways important to the production of fisheries resources.

The interplay between fishery yield and top predator culling in a multispecies fishery context

In food webs, fishery can play the role of top predator, competing thus with other top predators for valuable food resources. In this view, it has been claimed in fisheries management that culling of top predators can be a means to improve fishery yield. To investigate this hypothesis, we use theoretical population models to assess in a multispecies context how fishery yield from target species harvest responds to top predator cull. Defying crisp summary, the four analysed food web models show that this response may be either positive or negative or both, indicating that in terms of multispecies fishery management the harvest yield may not accrue as a consequence of predator removal. In addition, this multitude of behaviours points also to the fact that the response of fishery yield to top predator cull may be difficult to assess.

Shark discards in selective and mixed-species pelagic longline fisheries

The conservation status of several pelagic shark species is considered vulnerable with declining populations, yet data on shark fishing mortality remain limited for large ocean regions. Pelagic sharks are increasingly retained by mixed-species fisheries, or are discarded and not reported by selective fisheries for tunas (Thunnus spp.) or swordfish (Xiphias gladius). We estimated the fishing mortality of sharks (landings plus discard mortalities) in a South African-flagged pelagic longline fishery with diverse targeting and discard behaviour. A hierarchical cluster analysis was used to stratify the fleet according to the relative proportions of tunas, swordfish, blue sharks (Prionace glauca) and shortfin mako sharks (Isurus oxyrinchus) landed by individual vessels between 2013 and 2015. A spatial analysis of logbook data indicated that subfleets operated in distinct fishing areas, with overlap. Approximately 5% of all commercial longlines set during 2015 were sampled by a fisheries-independent observer, and the species, discard ratios and physical condition at discard of 6 019 captured sharks were recorded. Blue sharks and shortfin makos dominated observed shark catches, which were comprised of nine species and two species groups. Some 47% of observed sharks were retained and 20% were discarded in good physical condition. Only 4% of shortfin makos were discarded, compared to 68% of blue sharks. Blue shark discard mortality rates were twice as high as published at-vessel mortality rates, suggesting that onboard handling, among other factors, contributed to discard mortalities. Extrapolation to total fishing effort indicated a near 10-fold increase in blue shark and shortfin mako fishing mortality compared to an earlier study (1998–2005). Escalating shortfin mako fishing mortality was attributed to increased targeting to supply higher market demand. Discarding of blue sharks by selective fishing for tunas and swordfish had a greater impact on their fishing mortality than retention by shark-directed fleets. Higher levels of observer sampling are required to increase confidence in discard ratio estimates.

Recent declines in salmon body size impact ecosystems and fisheries

Declines in animal body sizes are widely reported and likely impact ecological interactions and ecosystem services. For harvested species subject to multiple stressors, limited understanding of the causes and consequences of size declines impedes prediction, prevention, and mitigation. We highlight widespread declines in Pacific salmon size based on 60 years of measurements from 12.5 million fish across Alaska, the last largely pristine North American salmon-producing region. Declines in salmon size, primarily resulting from shifting age structure, are associated with climate and competition at sea. Compared to salmon maturing before 1990, the reduced size of adult salmon after 2010 has potentially resulted in substantial losses to ecosystems and people; for Chinook salmon we estimated average per-fish reductions in egg production (-16%), nutrient transport (-28%), fisheries value (-21%), and meals for rural people (-26%). Downsizing of organisms is a global concern, and current trends may pose substantial risks for nature and people.

From plentiful to critically endangered: Demographic evidence of the artisanal fisheries impact on the smalltail shark (Carcharhinus porosus) from Northern Brazil

The smalltail shark, Carcharhinus porosus, was the most abundant elasmobranch species in fisheries off Brazil’s northern coast (BNC) in the 1980s, but its population has been declining since the 1990s. For this reason, a demographic analysis is necessary to determine the extent of this decline and the fishing effect on the BNC’s population. Therefore, we performed a stochastic demographic analysis of the population in the BNC, and considered its global center of abundance. Smalltail shark specimens (n = 937) were collected with gillnets in Maranhão state, eastern BNC, in the 1980s with sizes ranging between 29.6 and 120.0 cm total length. Most of the individuals (90.6%) caught were juveniles (< 6 years-old), and the mortality and exploitation rates showed that the species was overexploited (92.3% above the fishing mortality corresponding to the population equilibrium threshold). The smalltail shark’s biological characteristics, such as slow growth and low fecundity, demonstrate that it is one of the least resilient species among similar sized coastal sharks in the region. All these factors yielded an annual decrease of 28% in the intrinsic population growth rate, resulting in a population decline of more than 90% in only 10 years, and much higher for the current period. This set of features comprising fishing recruitment occurring upon juveniles, overfishing, and intrinsically low resilience make the population unable to sustain fishing pressure and severely hamper biological recruitment, thus causing this drastic population decline. Furthermore, several local extinctions for this species in the northeastern and southeastern regions of Brazil highlight its concerning conservation scenario. Therefore, since similar fisheries characteristics occur throughout its distribution range, C. porosus fits the criteria E of the IUCN Red List for a critically endangered species and urgent conservation measures are needed to prevent its extinction in the near future.

Population dynamics of threadfin porgy Evynnis cardinalis, an endangered species on the IUCN red list in the Beibu Gulf, South China Sea

Threadfin porgy Evynnis cardinalis is both a dominant fish species and an important fishing target in bottom trawl fisheries in the Beibu Gulf, South China Sea. It was listed as endangered (EN) in a recent International Union for Conservation of Nature (IUCN) red list. Despite its economic importance and endangered status, limited research on its biological characteristics and spatial-temporal distribution has been undertaken this last decade, creating uncertainty in current conservation and management. We analyse this species' spatial distribution characteristics using data from four seasonal bottom trawl surveys in 2014-2015, and report average catch per unit effort to vary seasonally, from 49.1 to 594.5 ind h^-1 . Growth, mortality and sexual maturity are reported for four time periods based on data from bottom trawl fishery surveys over 1961-1962, 1998-1999, 2006, and 2014-2015. Length frequency distributions changed from bimodal to unimodal, and the female-to-male ratio increased. Mean body length and length at first maturity decreased, whereas the growth coefficient increased, indicating miniaturization, early sexual maturity and accelerated growth, respectively. We report sparid catch to have first exceeded maximum sustainable yield in 2001, and to have remained overfished from 2010 to 2015. Since the 1980s, low-trophic-level fishes such as E. cardinalis have replaced high-trophic-level fishes such as Crimson snapper Lutjanus erythropterus to become dominant species. As catches have increased substantially, these species have been faced with overfishing, driving the ecosystem into an unstable state.

Improving prediction of rare species' distribution from community data

Species distribution models (SDMs) have been increasingly used to predict the geographic distribution of a wide range of organisms; however, relatively fewer research efforts have concentrated on rare species despite their critical roles in biological conservation. The present study tested whether community data may improve modelling rare species by sharing information among common and rare ones. We chose six SDMs that treat community data in different ways, including two traditional single-species models (random forest and artificial neural network) and four joint species distribution models that incorporate species associations implicitly (multivariate random forest and multi-response artificial neural network) or explicitly (hierarchical modelling of species communities and generalized joint attribute model). In addition, we evaluated two approaches of data arrangement, species filtering and conditional prediction, to enhance the selected models. The model predictions were tested using cross validation based on empirical data collected from marine fisheries surveys, and the effects of community data were evaluated by comparing models for six selected rare species. The results demonstrated that the community data improved the predictions of rare species' distributions to certain extent but might also be unhelpful in some cases. The rare species could be appropriately predicted in terms of occurrence, whereas their abundance tended to be underestimated by most models. Species filtering and conditional predictions substantially benefited the predictive performances of multiple- and single-species models, respectively. We conclude that both the modelling algorithms and community data need to be carefully selected in order to deliver improvement in modelling rare species. The study highlights the opportunity and challenges to improve prediction of rare species' distribution by making the most of community data.

Shark movement patterns in the Mexican Pacific: A conservation and management perspective

Marine animal tracking has become one of the major tools used to understand the behavior and ecology of a multitude of species in the ocean, thus there is an increasing body of knowledge about this subject worldwide, particularly for sharks. Nevertheless, little was known of the movement patterns of shark in the Mexican Pacific (MXP) and Gulf of California (GOC), except for the pioneering work carried out in the 1980s on the movements of scalloped hammerhead sharks in El Bajo Espiritu Santo and other islands in the region, as well as ongoing studies on white shark movements, migratory patterns and behavior off Isla Guadalupe. Here we present an overview of previous studies on the movements of sharks, as well as a comprehensive description of new studies currently being carried out by our research group at Pelagios Kakunjá on several species of sharks in the MXP. We show how information gleaned from these studies can be put to use to guide sustainable exploitation policies and promote effective conservation practices.

LeMaRns: A Length-based Multi-species analysis by numerical simulation in R

Fish stocks interact through predation and competition for resources, yet stocks are typically managed independently on a stock-by-stock basis. The need to take account of multi-species interactions is widely acknowledged. However, examples of the application of multi-species models to support management decisions are limited as they are often seen as too complex and lacking transparency. Thus there is a need for simple and transparent methods to address stock interactions in a way that supports managers. Here we introduce LeMaRns, a new R-package of a general length-structured fish community model, LeMans, that characterises fishing using fleets that can have different gears and species catch preferences. We describe the model, package implementation, and give three examples of use: determination of multi-species reference points; modelling of mixed-fishery interactions; and examination of the response of community indicators to dynamical changes in fleet effort within a mixed-fishery. LeMaRns offers a diverse array of options for parameterisation. This, along with the speed, comprehensive documentation, and open source nature of the package makes LeMans newly accessible, transparent, and easy to use, which we hope will lead to increased uptake by the fisheries management community.

Mass mortality in a Marine Educational Area on a remote South Pacific Atoll

In 2018, on the isolated Anaa atoll (South Pacific), a Marine Educational Area (MEA) was established by the local community to protect fisheries resources on the reef barrier next to their village. Whilst the remote location of the small MEA has provided some protection from anthropogenic pressures due to distance and low population, we showed that from 26 to 27 November 2018, high temperatures along with a hypoxic event and a low tide led to the mass mortality of several Anaa's marine species. The mass mortality in the MEA (area: 27,000 m²) included >14,000 juvenile fish, 1300 adult fish, 5100 juvenile crustaceans, and 260 juvenile octopus. This finding is particularly concerning because despite the creation of a MEA to protect marine resources, impacts from the warming waters associated with climate change limited the local efforts in Anaa atoll. This small, focused study demonstrates that local intervention may not be enough to mitigate the large-scale impacts of global climate change. It notes that local intervention can directly improve the fisheries resource but must be placed within a context of national and global interventions on climate change.

A Next-Generation Approach to Calculate Source-Sink Dynamics in Marine Metapopulations

In marine systems, adult populations confined to isolated habitat patches can be connected by larval dispersal. Source-sink theory provides effective tools to quantify the effect of specific habitat patches on the dynamics of connected populations. In this paper, we construct the next-generation matrix for a marine metapopulation and demonstrate how it can be used to calculate the source-sink dynamics of habitat patches. We investigate the effect of environmental variables on the source-sink dynamics and demonstrate how the next-generation matrix can provide useful biological insight into transient as well as asymptotic dynamics of the model.

Detecting illegal cyanide fishing: Establishing the evidence base for a reliable, post-collection test

Ornamental fish have been legally harvested since the 1930's but in the 60's, cyanide fishing was first documented. Target fish exposed to the chemical are temporarily paralysed making them easier to catch, but with high post-capture mortality and significant ecological impacts, its use is banned in most exporting countries. To differentiate illegally caught fish from those sustainably collected, efforts to develop a post-collection detection test began nearly 30 years ago. However, even the most promising approach has been questioned by other researchers as unrepeatable under different experimental conditions. In this paper we summarise the evidence-base for establishing a cyanide detection test for live fish by evaluating current approaches. We describe the key knowledge gaps which continue to limit our progress in implementing a screening programme and highlight some alternative solutions which may provide greater short to medium term opportunities to prevent the illegal practise before fish enter the supply chain.

Assessment of fishing-related plastic debris along the beaches in Kerala Coast, India

An assessment of quantity, composition and seasonal variation of fishing-related plastic debris was conducted in six beaches along the Kerala coast of India during 2017-2018. Plastic items were the most dominant type of waste constituting 73.8% by number and 59.9% by weight. In the total debris recorded, 5540 pieces (36%) weighing 198.4 kg (39.8%) were fishing related trash. On an average 14.4 ± 12 fishing related items/100 m², corresponding to mean weight of 0.55 ± 0.7 kg/100 m² was recorded from these beaches. Results indicated that the fishing-related plastic items were concentrated four times more in the beaches with higher fishing intensity, as compared to the other beaches. Also, the concentration of fishing-related plastic was recorded higher in the post-monsoon season compared to the lowest during monsoon, which was significant with p-value < 0.05. The results emphasize the role of fishing activities in the generation of marine litter.

Uptake and accumulation of cadmium, manganese and zinc by fisheries species: Trophic differences in sensitivity to environmental metal accumulation

Fishery targeted species living in estuaries face multiple anthropogenic pressures including habitat contamination. However, trace metal concentrations in aquatic organisms can be highly variable, making it difficult to interpret accumulation responses. Understanding sources for metal accumulation in these organisms and their biokinetics is important for management of local fisheries and ensuring safety and quality of consumed seafood, particularly in urbanised areas. In this study, we exposed Australian sand clams, school prawns and sand whiting to a combination of cadmium (Cd), manganese (Mn) and zinc (Zn) radioisotopes 1) dissolved in seawater, 2) adsorbed to suspended sediment particles and 3) in radiolabelled food. Sand clams were sensitive to Cd, Mn and Zn uptake and accumulation from all sources because of their filter feeding physiology. Mean Cd and Zn assimilation efficiencies (AE) were higher in clams fed benthic diatoms (51, 43, 63% for Cd, Mn and Zn, respectively) than clams fed an algal flagellate species (22, 32, 33% for Cd, Mn and Zn, respectively). Metal uptake by prawns from seawater was low, whereas assimilation from diet was high (67, 59, 64% mean AEs from Cd, Mn and Zn, respectively). Sand whiting did not accumulate metals from seawater, even after concentrations were increased. Assimilation from diet (labelled prawns) was also low for sand whiting, particularly for Cd and Zn (11, 26, 14% mean AEs from Cd, Mn and Zn, respectively). These results may help explain the persistence of sand whiting in contaminated estuaries. Suspended sediment exposures showed that prawns and fish are less likely than clams to be negatively affected by disturbance events such as floods, which can bring metals into estuaries. The findings of this study have implications for fisheries management, both for protection and remediation of important habitats, and to ensure safe standards for seafood consumption by humans.

Genome-wide SNP analyses reveal population structure of Portunus pelagicus along Vietnam coastline

The blue swimming crab (Portunus pelagicus Linnaeus, 1758) is one of the commercially exploited crab fishery resources in Vietnam. This is the first study to provide a broad survey of genetic diversity, population structure and migration patterns of P. pelagicus along the Vietnamese coastline. The crab samples were collected from northern, central and southern Vietnam. Here, we used a panel of single nucleotide polymorphisms (SNPs) generated from restriction site-associated DNA sequencing (RADseq). After removing 32 outlier loci, 306 putatively neutral SNPs from 96 individuals were used to assess fine-scale population structure of blue swimming crab. The mean observed heterozygosity (Ho) and expected heterozygosity (He) per locus was 0.196 and 0.223, respectively. Pairwise Fst and hierarchical AMOVA supported significant differentiation of central and northern from southern populations (P<0.01). Population structure analyses revealed that P. pelagicus in the south is a separate fisheries unit from the north and center. Contemporary migration patterns supported high migration between northern and central populations and restricted genetic exchange within the southern population. In contrast, historic gene flow provides strong evidence for single panmictic population. The results are useful for understanding current status of P. pelagicus in the wild under an environment changing due to natural and anthropogenic stresses, with implications for fisheries management.

Policy-driven changes in enclosure fisheries of large lakes in the Yangtze Plain: Evidence from satellite imagery

Enclosure fisheries have accommodated the widespread expansion of aquaculture in many lakes throughout the Yangtze Plain (YP), China, for over four decades. Such practices have increased food provision but have also triggered various detrimental environmental consequences. To restore ecosystem functions, the Chinese government recently implemented specific regulations to remove enclosure fences from lakes throughout the YP. However, little information is available on the spatial and temporal distributions of the enclosure fences, particularly in relation to the enforcement of recent policy changes. Using synthetic aperture radar (SAR) satellite images taken between 2002 and 2018, we conducted the first comprehensive assessment of the interannual changes in enclosure fences in 17 large lakes throughout the YP. Consistent decreases in fence density were found in most lakes after 2015; 15 lakes had >50% of their fences removed, while 9 lakes had >90% removed. The timing and implementation of the development and destruction of enclosure fisheries were related to government policy; before 2015, regional dynamics in enclosure fisheries were attributed to provincial policies, whereas the nearly ubiquitous fence demolition after 2015 was likely a response to national policy. This study represents remotely sensed evidence that demonstrates the importance of both local and national environmental policies and their effectiveness in mitigating ongoing human impacts on vulnerable and valuable natural resources. These findings provide valuable baseline information for future lake environmental monitoring and restoration in the YP region, and the methods used here could be applied to other lacustrine and coastal regions experiencing similar aquaculture activities.

The Primary Care of Immigrant Workers and Their Associated Characteristics within A Taiwanese Fishing Community

In Taiwan, immigrant workers play an important role in fisheries but they are easily ignored by society. The health problems and associated characteristics of immigrant workers in fisheries remain unclear. Descriptive and retrospective analyses were performed. Outpatient data were collected from a primary care clinic for six fishing villages in North Eastern Taiwan between 1 August 2016 and 31 July 2017. The data of immigrant workers was recorded and compared with that of natives. A total of 241 immigrant workers and 1342 natives were enrolled. Compared with the natives, the immigrant workers had a significantly younger age, male predominance, and fewer mean visits per year. The immigrant worker’s visits tended to be more highly focused during the third quarter of the year. Immigrant workers paid more registration fees and self-payment, but they paid less on diagnosis fees, oral medication, laboratory exams and had reduced total costs. The top five diagnoses for immigrant workers were respiratory diseases (38.3%), trauma (15.2%), musculoskeletal diseases (11.2%), skin-related diseases (9.5%), and digestive diseases (9.1%). Immigrant workers were positively correlated with infectious/parasitic diseases, and negatively correlated with medical consults and endocrine/metabolic diseases. Immigrant workers were also positively associated with registration fees and self-payment, but negatively correlated with diagnosis fees and total costs (all p < 0.05). The distribution of skin diseases and trauma were affected by age and sex as opposed to ethnic group. Immigrant status’ health issues should be given more attention.

Trace element fingerprinting of blue mussel (Mytilus edulis) shells and soft tissues successfully reveals harvesting locations

Globally, aquaculture products are expected to account for >60% of total seafood produce by 2030. In the European Union, the seafood sector is of considerable economic importance to member states with household spending on seafood produce totalling €54.8 billion in 2016. Within the EU, shellfish aquaculture supports livelihoods and employment in many rural communities throughout the region. Harmful algal blooms pose considerable risk to consumer safety and in turn, stability of the shellfish market. If contaminated produce was to make it to the market the health risk to the public could be considerable, but the damage to the sector through loss of trust in producers would also be significant. Mytilus edulis account for a considerable portion of the aquaculture sector in the Northeast Atlantic. At present, no scientific tool is available to industry regulators, to allow them to trace mussel produce to its source, uphold food safety standards and ensure consumer confidence. The present study uses chemical analysis of shells and soft tissues to classify individual M. edulis to their site of harvest. The use of random forest classification of trace element composition has revealed location specific elemental signatures for all examined sites. This led to the correct classification of 100% of individuals sampled to their respective harvesting locations, including two sites located just 6 km apart within the same bay. The protocol demonstrated here provides the basis for a scientifically driven traceability framework for shellfish produce.

Lifejackets and Lobstermen: Giving Safety Equipment a Competitive Advantage

Background: Falls overboard are the most frequent cause of death in the Northeast lobster fishing industry. National Institute for Occupational Safety and Health (NIOSH) surveillance indicates every victim of a fall overboard who has been found was not wearing a lifejacket. Preliminary research conducted in Maine and Massachusetts indicates lifejacket use is relatively uncommon among lobstermen due to barriers such as comfort, practicality, and social norms.Methods: This study highlights an initiative to: (1) trial various lifejacket designs with lobstermen; (2) identify the most popular designs; and (3) identify other features that could encourage use of lifejackets. In 2017, nine designs were trialed with lobstermen in Maine and Massachusetts during the winter and summer fishing seasons. Participants were recruited dockside, and lifejackets were randomly assigned. Participants completed surveys at 1 week and 4 weeks to assess positive and negative design features and to understand the importance of survival technology that can be used in conjunction with lifejackets.Results: 181 lobstermen in Maine and Massachusetts agreed to participate. Recruitment rates were 90.5%, while the survey completion rate was 88.4%. Survey results identified no clear preference for a specific lifejacket design; however, the ability to choose from many options appeared to be an important factor.Conclusion: Previous studies have indicated that lifejacket preferences are fisheries specific. In the Northeast lobster fishery, however, individual preferences varied. Our research demonstrates that a range of devices covering different buoyancies, wear type, and retrieval systems should be made more available to lobstermen.

Exploring determinants for the implementation of mixed TURF-aquaculture systems

Territorial use rights in fisheries (TURFs) have been highlighted as a means to deter the race for fish. Nevertheless, in many situations TURFs are not able to meet all their goals, jeopardizing their continuity. Here we explore one of several innovations on TURFs, mixed TURF-aquaculture systems, which can help overcome the challenges of maintaining sustainable socio-ecological systems. We analyzed the history of mixed TURF and small-scale aquaculture systems in Chile, particularly 8 recent learning platforms in the Coquimbo region. Additionally, we assessed the impact of 6 variables, from multiple spheres, on the implementation of mixed TURF-aquaculture systems. Despite low values in several variables, 75% of the learning platforms managed to implement aquaculture systems and 38% have been successful in developing monitoring efforts. Social capital was key in the implementation of the mixed systems. By investing in social capital policy makers can contribute to the successful implementation of mixed TURF-aquaculture systems, thus promoting a livelihood diversification strategy for fishing communities that encompasses the economic benefits of aquaculture with the socio-ecological benefits of TURFs. However, their development and enabling conditions must be monitored to embrace their synergies.

Preferences and perceptions of the recreational spearfishery of the Great Barrier Reef

Recreational fishing practices can have significant impacts on marine ecosystems but their catch dynamics are often difficult to quantify, particularly for spearfishing. On coral reefs, the impacts of recreational spearfishing are often considered to be negligible compared to other practices, but the highly selective method adopted by spearfishers can result in locally distinct ecological consequences. Here we investigated the spatial patterns and catch composition of recreational spearfishers on the Great Barrier Reef using an online survey (n = 141 participants) targeted at spearfishers active along the coastline of Queensland. Observations from within the Queensland spearfishing community were also used to explore perceived changes in catches of three functionally distinct spearing targets. Preferred reef regions (coastal, inshore, offshore) differed among spearfishers from Bundaberg (south) to Cooktown (north). The piscivorous coral trout, Plectropomus leopardus, was suggested to be the preferred target comprising 34% (±1.5 SE) of spearfishers' reported catch composition. Spearfishers also noted a variety of changes in their catch composition over time, particularly regarding parrotfishes (decreased landings) and tuskfishes (increased landings). How this relates to the relative abundance and population biology of these taxa on the Great Barrier Reef requires attention. Spearfishers can provide important information regarding the status of their fishery through direct observations, which can inform legislation when acknowledged.

Comparing adaptation ability towards climate change impacts between the youth and the older fishermen

In recent years, a considerable amount of studies published locally which focused on the influence of age on climate change ability. Accordingly, this has driven the present study to achieve its main objective which is to compare the adaptation ability between youth and older fishermen. The current research is quantitative in nature; hence, a survey was conducted on a total of 259 youth and older fishermen residing in different states of Malaysia, namely Pulau Pinang, Terengganu, Johor, and Kedah. The present study managed to conclude a unique and important result which stated that youth and older fishermen within the context of Malaysia have an equally strong adaptation ability. In regard to this matter, a number of recommendations were presented at the end of this paper with the hope that it can act as a basis for future scholars to conduct more climate change related studies.

Japans commercial whaling is a threat to public health

Japans' decision to withdraw from the International Whaling Commission and reinstate commercial hunting on minke, sei and Bryde's whales has recently been discussed in several journals. Here we discuss mercury exposure to the public eating baleen whales, toothed whales and tuna in relation to the European Food Safety Authority (EFSA) tolerable weekly intake (TWI).

Historical changes (1905-present) in catch size and composition reflect altering fisheries practices on a small Caribbean island

Effective assessments of the status of Caribbean fish communities require historical baselines to adequately understand how much fish communities have changed through time. To identify such changes and their causes, we compiled a historical overview using data collected at the beginning (1905–1908), middle (1958–1965) and end (1984–2016) of the 20^th century, of the artisanal fishing practices and their effects on fish populations around Curaçao, a small island in the southern Caribbean. We documented historical trends in total catch, species composition, and catch sizes per fisher per month for different types of fisheries and related these to technological and environmental changes affecting the island’s fisheries and fish communities. We found that since 1905, fishers targeted species increasingly farther from shore after species occurring closer to shore had become rare. This resulted in surprisingly similar catches in terms of weight, but not composition. Large predatory reef fishes living close to shore (e.g., large Epinephelid species) had virtually disappeared from catches around the mid-20^th century, questioning the use of data from this period as baseline data for modern day fish assessments. Secondly, we compared fish landings to in-situ counts from 1969 to estimate the relative contributions of habitat destruction and overfishing to the changes in fish abundance around Curaçao. The decline in coral dominated reef communities corresponded to a concurrent decrease in the abundance and diversity of smaller reef fish species not targeted by fishers, suggesting habitat loss, in addition to fishing, caused the observed declines in reef fish abundance around Curaçao.

Bycatch and discarding patterns of dogfish and sharks taken in English and Welsh commercial fisheries

At-sea observer programmes can provide spatio-temporal data on the sizes and quantities of fish being either discarded or retained, including for species and size categories that may not be sampled effectively during scientific surveys. Such data were analysed for English and Welsh fisheries operating on the continental shelf of the North Sea ecoregion (ICES Divisions 4a-c and 7d) and Celtic Seas ecoregion (ICES Divisions 6a, 7a-c, e-k) for the period (2002-2016). These data were collated for four main gear types: beamtrawl, nephrops and otter trawls, and nets (including gillnets, tangle nets and trammel nets). Beamtrawlers caught proportionally more smaller individuals than otter trawlers, whilst nets were the most size-selective gear for larger sharks. Size-related discarding was observed, with smaller spurdog Squalus acanthias and starry smooth-hound Mustelus asterias (< 60 cm total length, L_T ) usually being discarded. Such size-based selection was not evident for lesser-spotted dogfish Scyliorhinus canicula, which was generally landed as bait. Temporal changes in the discard-retention patterns were evident for S. acanthias and porbeagle Lamna nasus, with increased regulatory discarding as management measures became restrictive. A corresponding increase in the proportion of the non-quota M. asterias retained was also observed over the study period. Knowledge of the size-based discard-retention patterns by métier can also help inform on where future studies on discard survival could usefully be undertaken.

Global ecosystem overfishing: Clear delineation within real limits to production

The well-documented value of marine fisheries is threatened by overfishing. Management typically focuses on target populations but lacks effective tools to document or restrain overexploitation of marine ecosystems. Here, we present three indices and accompanying thresholds to detect and delineate ecosystem overfishing (EOF): the Fogarty, Friedland, and Ryther indices. These are based on widely available and readily interpreted catch and satellite data that link fisheries landings to primary production using known limits of trophic transfer efficiency. We propose theoretically and empirically based thresholds for each of those indices; with these criteria, several ecosystems are fished sustainably, but nearly 40 to 50% of tropical and temperate ecosystems exceed even extreme thresholds. Applying these criteria to global fisheries data results in strong evidence for two specific instances of EOF, increases in both pressure on tropical fish and a climate-mediated polar shift. Here, we show that these two patterns represent evidence for global EOF.