Catch Trends Research Articles

Estimating Fishing Exploitation Rates to Simulate Global Catches and Biomass Changes of Pelagic and Demersal Fish

AbstractRobust projections of future trends in global fish biomass, production and catches are needed for informed fisheries policy in a changing climate. Trust in future projections, however, relies on establishing that models can accurately simulate past relationships between exploitation rates and ecosystem states. In addition, historical simulations are important to describe how the oceans have changed due to fishing. Here we use fisheries catch, catch‐only assessment models and effort data to estimate regional fishing exploitation levels, defined as the fishing mortality relative to fishing mortality at maximum sustainable yield (F/FMSY). These estimates are given for large pelagic, forage and demersal fish types across all large marine ecosystems and the high seas between 1961 and 2004; and with a ‘ramp‐up’ between 1841 and 1960. We find that global exploitation rates for large pelagic and demersal fish consistently exceed those for forage fish and peak in the late 1980s. We use the rates to globally simulate historical fishing patterns in a mechanistic fish community model. The modeled catch aligns with the reconstructed catch, both for total catch and catch distribution by functional type. Simulations show a clear deviation from an unfished model state, with a 25% reduction in biomass in large pelagic and demersal fish in shelf regions in recent years and a 50% increase in forage fish, primarily due to reduced predation. The simulations can set a baseline for assessing the effect of climate change relative to fishing. The results highlight the influential role of fishing as a primary driver of global fish community dynamics.

Marine recreational fishery trends in total catch, catch per unit effort, and release rates in Delaware during 1981–2021

AbstractThe impact of recreational fisheries on marine ecosystems is often overshadowed by commercial fisheries, although recreational fishing harvest can be substantial, especially for species that are either overfished or experiencing overfishing. Delaware is a small coastal state with ~1,000,000 residents and nearly 272,000 resident and non‐resident anglers. We used publicly available data for Delaware's recreational fisheries during 1981–2021 to determine the nine most caught fish species and to evaluate trends in total numbers caught, harvested, released, and catch per unit effort (CPUE). The top nine most frequently captured fish by recreational anglers were Summer Flounder (Paralichthys dentatus), Atlantic Croaker (Micropogonias undulatus), Bluefish (Pomatomus saltatrix), Black Sea Bass (Centropristis striata), Weakfish (Cynoscion regalis), White Perch (Morone americana), Tautog (Tautoga onitis), Striped Bass (Morone saxatilis), and Spot (Leiostomus xanthurus). The proportion of fish released increased through time for all nine species, suggesting that the recreational fishery in Delaware is transitioning from a harvest‐oriented to a catch‐and‐release‐oriented fishery. Observations of higher release rates in recreational fisheries of Delaware are consistent with the findings elsewhere in the world for freshwater and marine systems.

Large pelagic fish exploitation by longliners in the Atlantic Ocean and Mediterranean Sea: A contribution to spatial planning and sustainable fisheries

Understanding longline fisheries dynamics is crucial for sustainable resource management. This study aims to provide a panorama of the fishing effort of the principal nations that have exploited tuna and associated species in the Atlantic Ocean for the past decade, integrating vessel data from Global Fishing Watch (GFW) and catch data from the International Commission for the Conservation of Atlantic Tunas (ICAAT), with specific information on the production of these different fleets and resources. Twelve nations represented 94.6 % of all Apparent fishing hours (AFH) of the total effort in the Atlantic Ocean and 99.9 % of all catches in the last years. Our study revealed that regions proximate to the continental shelf break and oceanic islands exhibit notably higher fishing effort than other areas within the Atlantic Ocean. We also highlight a declining trend in fishing efforts in the last ten years, likely due to regulation and overfishing. The blue shark (Prionace glauca) was the most caught species in biomass, representing 38.1 %; bigeye tuna (Thunnus obesus) represented 20.5 %; swordfish (Xiphias gladius) 15.1 %; albacore tuna (Thunnus alalunga) 11.3 %, and yellowfin tuna (Thunnus albacares) 6.1 %. The alarming trends in pelagic shark catch emphasise the need for immediate conservation actions. Management strategies should target critical nations, addressing their significant contributions to shark catch. The lack of information on several species and periods highlights the need for comprehensive research and management initiatives.

A rapid increase in tropical species of grouper (Perciformes: Serranidae) in the temperate waters, the Goto Islands, Japan.

Global warming has resulted in rapid poleward shifts in the geographical distributions of many tropical fish species. This study conducted daily market surveys from 2008 to 2013 to investigate catch trends of seven commercially important grouper species in the temperate Goto Islands, Japan. Our results revealed that the catch numbers of tropical grouper species increased rapidly by an average of 5.9-fold (12.3-fold at maximum) within six years, whereas the temperate and subtropical species did not exhibit substantial changes. Based on the findings of several previous studies, the rapid increase in the number of tropical groupers in temperate waters was most likely caused by the successful settlement of larvae transported from tropical waters. Large-scale ocean currents may facilitate larval transport from tropical waters because the Goto Islands face the Tsushima Warm Current, which branches from the Kuroshio Current. Meanwhile, the transition processes of size distribution in tropical groupers suggest a possible hypothesis that adults migrating from tropical waters first settle in temperate waters and then enhance their populations by reproduction. Further studies are required to determine how tropical grouper species settle and how their populations increase in temperate waters.

A multidecadal study of the Malabar upwelling system influencing Indian Mackerel landings along the coasts of Karnataka and Kerala, south-east Arabian Sea

Indian Mackerel (Rastrelliger kanagurta) is an essential small pelagic fishery resource, contributing to nearly 30 % of India's total marine fish landing. However, this species' life cycle and stock status are poorly understood and data deficient. Ocean mesoscale events are also known to influence their landing, besides the environmental factors like- salinity, chlorophyll, and sea surface temperature, affecting these small pelagic fishes' availability, migration, feeding, and reproductive activity. The Malabar upwelling region (southwest coast of India) is a significant upwelling system where upwelling occurs during the monsoon months. The nutrient-rich water increases the productivity of surface water, leading to plankton abundance. This productivity sustains a fishery for several commercially important fishes, mainly small pelagics such as sardines, mackerels, and anchovies, supporting India's most significant coastal pelagic fishery. For understanding the relationship between the target fish and the oceanographic events, in the present study, Pearson's correlation has been estimated between Indian Mackerel landing, rainfall, Sea water temperature at 0, 10, 20, 30, 45, and 50 m depths, mixed layer depth (MLD), their anomalies and occurrences of potential fishing zone (PFZ) lines along the Malabar upwelling region and corresponding coasts of Karnataka and Kerala. Mackerel landing time series showed a significant autocorrelation in four-quarter lag, correlation with rainfall anomaly in one-quarter lag, with PFZ line and MLD in three-quarter lag, and with SWT@50 (Seawater temperature@50 m depth) and SST anomaly in two-quarter lag both in Karnataka and Kerala. Upwelling events, as indicated by the presence of PFZ lines, were found to significantly impact the landings of Indian mackerel along the Karnataka and Kerala coasts. Polynomial equations were used to model the relationship between mackerel landings and these environmental factors, effectively capturing the influence of these parameters on mackerel catch trends.

The Use of the GWPCA-MGWR Model for Studying Spatial Relationships between Environmental Variables and Longline Catches of Yellowfin Tunas

The yellowfin tuna represents a significant fishery resource in the Pacific Ocean. Its resource endowment status and spatial variation mechanisms are intricately influenced by marine environments, particularly under varying climate events. Consequently, investigating the spatial variation patterns of dominant environmental factors under diverse climate conditions, and understanding the response of yellowfin tuna catch volume based on the spatial heterogeneity among these environmental factors, presents a formidable challenge. This paper utilizes comprehensive 5°×5° yellowfin tuna longline fishing data and environmental data, including seawater temperature and salinity, published by the Western and Central Pacific Fisheries Commission (WCPFC) and the Inter-American Tropical Tuna Commission (IATTC) for the period 2000–2021 in the Pacific Ocean. In conjunction with the Niño index, a multiscale geographically weighted regression model based on geographically weighted principal component analysis (GWPCA-MGWR) and spatial association between zones (SABZ) is employed for this study. The results indicate the following: (1) The spatial distribution of dominant environmental factors affecting the catch of Pacific yellowfin tuna is primarily divided into two types: seawater temperature dominates in the western Pacific Ocean, while salinity dominates in the eastern Pacific Ocean. When El Niño occurs, the area with seawater temperature as the dominant environmental factor in the western Pacific Ocean further extends eastward, and the water layers where the dominant environmental factors are located develop to deeper depths; when La Niña occurs, there is a clear westward expansion in the area with seawater salinity as the dominant factor in the eastern Pacific Ocean. This change in the spatial distribution pattern of dominant factors is closely related to the movement of the position of the warm pool and cold tongue under ENSO events. (2) The areas with a higher catch of Pacific yellowfin tuna are spatially associated with the dominant environmental factor of mid-deep seawater temperature (105–155 m temperature) to a greater extent than other factors, the highest correlation exceeds 70%, and remain relatively stable under different ENSO events. The formation of this spatial association pattern is related to the vertical movement of yellowfin tuna as affected by subsurface seawater temperature. (3) The GWPCA-MGWR model can fully capture the differences in environmental variability among subregions in the Pacific Ocean under different climatic backgrounds, intuitively reflect the changing areas and influencing boundaries from a macro perspective, and has a relatively accurate prediction on the trend of yellowfin tuna catch in the Pacific Ocean.

Estuarine residency and habitat preferences of Atlantic Tripletail in the northwestern Gulf of Mexico

AbstractObjectiveThe Atlantic Tripletail Lobotes surinamensis is a globally distributed subtropical and tropical fish species that inhabits estuaries throughout the northern Gulf of Mexico (GOM), particularly during warm months. Little is known about distribution and residency patterns within estuaries, as the species is rarely caught in the recreational fishery, and virtually no commercial fishery exists for the species in the GOM.MethodsWe used data from a long‐term fishery‐independent gill‐net survey to model estuarine distribution throughout Texas and to relate environmental variables to the Atlantic Tripletail catch.ResultAlthough there were no observable temporal trends in catch over the time series (1990–2022), the most recent 6 years included record catch in six of the 10 major Texas estuaries, possibly indicating a recent pulse in abundance. Catch throughout the time series was spatially aggregated in a small number of “hot spots” observed coastwide. Latitude was the best predictor of catch, although wind fetch and wind aspect (wind direction in relation to shoreline direction) were important predictors, and catch was highest near GOM inlets. The Texas Parks and Wildlife Department gill‐net sampling program caught a range of Atlantic Tripletail between 171 and 880 mm total length, indicating a potential gear bias against juveniles.ConclusionDespite this gear bias, these data shed light on the factors that drive Atlantic Tripletail estuarine distribution and abundance in the northwestern GOM. Wind‐driven passive movements in the estuary, combined with active selection of polyhaline habitats near GOM inlets, might be primary drivers of Atlantic Tripletail catch, thus supporting findings from previous studies.

Adapting to climate change in a spiny lobster (Jasus edwardsii) fishery: A harvest strategy response

The complex lifecycle of spiny lobsters makes the species particularly vulnerable to the impacts of climate change. In south-eastern Australia, a regime shift in productivity was experienced during the late 1990s with evidence indicating that increased water temperatures had impacted on female size-of-maturity. Within the Southern Zone fishery of South Australia, this translated into low levels of egg production and sub-optimal fishery performance. In 2018, the harvest strategy for the fishery was reviewed with the primary focus of achieving a target percentage of unexploited egg production (%UEP) within an agreed timeframe. The proposed harvest strategy was based on a tabular harvest control rule, where catch per unit effort (CPUE) from the preceding season, as an indicator of lobster abundance, specified the following year’s total allowable commercial catch (TACC). To account for climate change impacts, the harvest strategy was assessed using a projection model where recruitment was sampled from post-regime shift years, thereby adopting a conservative approach to stock rebuilding. Results were assessed against projected trends in catch, CPUE and %UEP. In 2020, this harvest control rule was formally adopted and is now used in annual TACC setting. Observed values for key indicators have been closely aligned with projected estimates, with %UEP estimates approaching the target reference point. Specifically, %UEP has improved from 10% to 15% with the target projected to be achieved by the late 2020 s. Projections are sensitive to recruitment however, with a 21% lower recruitment scenario failing to reach target levels, thereby reinforcing the need to account for climate change impacts in harvest strategy testing.

Including close-kin mark-recapture data in statistical catch-at-age stock assessments and management strategies

Close-kin mark-recapture (CKMR) data can be used on their own to provide estimates of fish spawning stock biomass, adult mortality rate and fecundity-at-age. However, CKMR data can also be integrated directly into a stock assessment. We present a simplified example of integrating CKMR data within the Stock Synthesis assessment framework, and use simulation to evaluate management strategies based on the harvest control rule used to set catch limits for fish stocks off southeast Australia. The simulations are tailored to jackass morwong, Nemadactylus macropterus, a moderately-long lived (up to 46 years) fish species that is believed to have exhibited a regime-shift reduction in recruitment. We identify the sample sizes needed for a CKMR-based management strategy to achieve similar performance to an (optimistically parameterized) catch-per-unit-effort (CPUE)-based approach for this species. A CKMR-based management strategy can perform at least as well as a CPUE-based approach and CKMR data provide information to better estimate parameters such as adult natural mortality. Moreover, CKMR-based management strategies are not subject to the risk associated with CPUE-based approaches related to trends in catchability. The performances of CKMR-based assessment methods and management strategies are likely case-specific, but this paper shows the viability of including CKMR data in next generation stock assessments and harvest control rules.

Untangling multi-species fisheries data with species distribution models

Long-term trends in fisheries catch are useful to monitor effects of fishing on wild populations. However, fisheries catch data are often aggregated in multi-species complexes, complicating assessments of individual species. Non-target species are often grouped together in this way, but this becomes problematic when increasingly common shifts toward targeting incidental species demand closer management focus at the species level. Species distribution models (SDMs) offer an under-utilised tool to allocate aggregated catch data among species for individual assessments. Here, we present a case study of two shovel-nosed lobsters (Thenus spp.), previously caught incidentally and recorded together in logbook records, to illustrate the design and use of catch allocation SDMs to untangle multi-species data for stock assessments of individual species. We demonstrate how catch allocation SDMs reveal previously masked species-specific catch trends from aggregated data and can identify shifts in fishing behaviour, e.g., changes in target species. Finally, we review key assumptions and limitations of this approach that may arise when applied across a broad geographic or taxonomic scope. Our aim is to provide a template to assist researchers and managers seeking to assess stocks of individual species using aggregated multi-species data.

New directions for Indigenous and local knowledge research and application in fisheries science: Lessons from a systematic review

AbstractSocial‐ecological systems like fisheries provide food, livelihoods and recreation. However, lack of data and its integration into governance hinders their conservation and management. Stakeholders possess site‐specific knowledge crucial for confronting these challenges. There is increasing recognition that Indigenous and local knowledge (ILK) is valuable, but structural differences between ILK and quantitative archetypes have stalled the assimilation of ILK into fisheries management, despite acknowledged bias and uncertainty in scientific methods. Conducting a systematic review of fisheries‐associated ILK research (n = 397 articles), we examined how ILK is accessed, applied, distributed across space and species, and has evolved. We show that ILK has generated qualitative, semi‐quantitative and quantitative information for diverse taxa across 98 countries. Fisheries‐associated ILK research mostly targets small‐scale and artisanal fishers (70% of studies) and typically uses semi‐structured interviews (60%). We revealed large variability in sample size (n = 4–7638), predicted by the approach employed and the data generated (i.e. qualitative studies target smaller groups). Using thematic categorisation, we show that scientists are still exploring techniques, or ‘validating’ ILK through comparisons with quantitative scientific data (20%), and recording qualitative information of what fishers understand (40%). A few researchers are applying quantitative social science methods to derive trends in abundance, catch and effort. Such approaches facilitate recognition of local insight in fisheries management but fall short of accepting ILK as a valid complementary way of knowing about fisheries systems. This synthesis reveals that development and increased opportunities are needed to bridge ILK and quantitative scientific data.

Recent Declining Trends in Pelagic Fish Catches in the Indian Ocean off Sri Lanka: Is Gill Oxygen Limitation Theory (GOLT) a Possible Explanation?

Recent trends in the pelagic fish landings of multi-day fishing fleets operated from Sri Lanka indicated significant declines in many fish species. Therefore, the present preliminary analysis investigates the perceptions of fishers on recent declining trends of pelagic fish landings from offshore areas of the Indian Ocean and further investigates whether the most common pelagic species landed in Sri Lanka conform to the gill oxygen limitation theory (GOLT) and to speculate GOLT as a possible explanation to such trends. According to the perceptions of 457 skippers of fishing vessels interviewed, such declines were possibly attributed to shifting of the areas of occurrence of pelagic fish species, making them less vulnerable to multi-day fishing vessels. As climate change and deoxygenation are major stressors affecting fish stocks, there is a challenging need for disentangling the impacts of these stressors from the effects of overfishing. The 18 most common pelagic fish species harvested from the Indian Ocean confirmed to the predictions from the GOLT, suggesting that shifting of these stocks could be due to deoxygenation which may have been triggered by increased sea surface and sub-surface temperatures. Therefore, fishery-independent surveys are needed to investigate the shifting of areas of occurrence of pelagic fishes in the Indian Ocean to understand their areas of occurrence the further investigate the relevance of GOLT for defining regional fisheries management plans.

Diving into archival data: The hidden decline of the giant grouper (Epinephelus lanceolatus) in Queensland, Australia

AbstractThe giant grouper (Epinephelus lanceolatus) is the largest reef fish in the Indo‐Pacific (~2.5 m TL, >400 kg), and it is highly susceptible to overfishing. Despite regional protections and documented population declines, the species is listed by IUCN as Data Deficient due to minimal long‐term population data and a paucity of life history information. This study used historical fishing records derived from newspaper articles, fishing magazines, grey literature and naturalists' descriptions to collate life history information and reconstruct giant grouper population trends from 1854 to 1958 in Queensland, Australia. Historical recreational catch trends of four biologically distinct grouper size classes demonstrated that over 92 years, fishing disproportionately affected two size classes: immature (fish below reproductive size) and mature individuals. Changes in the probability of capturing a grouper within a recreational fishery were examined as a proxy of relative abundance. The probability of catching a giant grouper within a popular recreational fishery significantly declined from 81% in 1860 to 2% in 1958. Further analysis based on a non‐probabilistic method of giant grouper sighting records showed fluctuations in the giant grouper population trajectory, from a steady decline during the early 20th century to an increase during WWII (1939–1945) followed by a reduction in the last half of the 20th century. This study highlights the importance of archival sources to uncover population trends of rare species by combining quantitative assessments and biological inferences to determine the timing and occurrence of population declines and recoveries and inform how vulnerable fish species respond to the cumulative effects of fishing over time.

The dynamics of arabesque greenling fishery off south Kuril Islands

The purpose of this work was to characterize the biological and commercial indicators of arabesque greenling in the Kunashir Strait during 1998–2022.The basic material for the article was the data collected during the net fishery of arabesque greenling by the fleet of small-tonnage vessels of the Japanese fishing cooperative in the city of Rausu in the eastern (Russian) zone of the Kunashir Strait.Results: It is shown that the stock resources of arabesque greenling in the waters of the southern Kuril Islands have been declining during for a long period of time. Despite a short-term growth of catch per effort in 2018–2021, in 2022 there was again a decrease of fishery indicators. The negative trend of catch per effort is directly associated with the features of dynamics of arabesque greenling resources distributed in Kunashir Strait and in the Sea of Okhotsk waters of Hokkaido.Practical significance: The new information makes it possible to determine the current trends in total biomass changing for commercial fish and to clarify the fishery capabilities of the area in the nearest future.

Stakeholders’ perception on consumption, fishing, and conservation of Red grouper, Epinephelus morio, off the northern coast of the Yucatan Peninsula, Mexico

The fishery of Red grouper, Epinephelus morio, is one of the most commercially important in Yucatan, Mexico. However, catch trends declined from more than 14,000 t in 1970 to less than 6500 t in 2019. Consequently, the fishery authority (CONAPESCA) declared this fishery overexploited. Stakeholders may play a fundamental role regulating catch trends of Red grouper adopting responsible fishing and consumption. This work aimed to evaluate perceptions of stakeholders (fishers and fish consumers) on consumption, fishing status, and conservation of Red grouper in Yucatan using interviews and web-based questionnaires. Results revealed stakeholders regularly consume Red grouper, with fishing and consumption influenced by economic, social, and cultural factors. Stakeholders were aware of the fishery management in place, such as a seasonal, fishing ban and the minimum catch size, established by the federal government for Red grouper. Differences emerged regarding perception on fishery management between fishers and fish consumers. All stakeholders showed a willingness to follow regulations and responsible consumption during the ban, and proposed alternatives for protection through enhancing fishery regulatory measures, updating the ban and establishing spatial restrictions, such as zones for fishery protection (no-take zones). Understanding stakeholder perceptions is utmost because identifying this knowledge could provide a clearer scenario and more focused fishery management approaches for managers to promote the recovery of the Red grouper fishery. We recommend implementing a precautionary management scheme based on a combination of a management strategic evaluation and a renovated fishery strategy, along with other community-based approaches, for the Red grouper fishery in Yucatan

Catch of Otolithes ruber (Bloch & Schneider, 1801) under Varying Fishing Practices of Municipal Fisherfolks in San Miguel Bay, Philippines

Tiger-toothed croaker or Otolithes ruber (Bloch & Schneider 1801) is native to San Miguel Bay in Bicol, one of the most productive fishing grounds in the Philippines. Locally known as “abo”, it is one of the major fish catch in the bay and its processing is a seasonal livelihood among coastal villages that commands high market price. With the present state of area, this study aimed to provide information on O. ruber catch trend under the different fishing practices among municipal fisherfolks. On-board surveys and observations (fishing trips) were conducted from the selected barangays of the seven municipalities around the Bay, which were attended by fisherfolk who have been into fishing activity for a long time. The morphometric characteristics of the fish in terms of size (lengths and weights), sex type, and sexual maturity were assessed. Fisherfolks prefer to perform fishing activities applying fishing methods such as “timbog” (“tupak”), “patalang” and “hugos”, if the water is turbid while others believed in the phases of the moon wherein better catch is experienced when the moon is on its first or last quarters. Fishing trips demonstrated that fisherfolks used bottom-set gillnets and commonly explored the middle to the mouth of the Bay off the municipalities of Mercedes and Siruma. From the 162.69 kg total catch during the 22 fishing trips, 31.49% or 51.22 kg of which were O. ruber caught largely from Mercedes, Calabanga and Cabusao areas. Mercedes employed the “patalang” method while the other two employed “timbog” method. Out of 434 O. ruber samples, 222 females and 212 males, having 1:1 ratio, were identified with TL of 19.14 + 0.11 cm and body weight of 70.76 + 1.46 g. Moreover, macroscopic analyses of gonads revealed that maturity stages of females ranged from mature to ripe or spawning while most males are already mature and gravid with some developing virgin.

Shifts in the size and distribution of marine trophy fishing world records

Abstract The extensive nature of recreational angling makes it difficult to explore trends in global catches. However, trophy fishing world records may provide an insight into recreational fishing pressure on the largest species and size classes. Trophy fishing is promoted and recorded by the International Game Fish Association (IGFA), who manage an 80‐year database on the largest individuals of a species caught – called all‐tackle records (ATRs) – with information on the size and location of each record catch. We analyse these data to explore temporal trends in the size of record‐setting fishes, determine how past and present ATR catches are distributed globally, and examine trends in records for International Union for Conservation of Nature (IUCN) threatened species. The number of ATRs, and the number of species awarded an ATR, have increased significantly over the past 80 years. New records are for increasingly smaller maximum‐sized species of fish, with the average sized record shifting from 167.7 kg in the 1950s to 8.1 kg in the 2010s. ATRs for species listed as threatened (Vulnerable or higher) on the IUCN Red List have also declined by approximately 66% over the past two decades. Records were unevenly distributed around the world but have spread globally over time. Historically, ATRs were concentrated around the coastline of the USA but in recent decades more were reported in areas such as Japan and New Zealand. These data either reflect a shift away from mainly targeting large taxa to targeting a wider variety of smaller species, or that there are now limited larger specimens and so fewer ATRs are being set. Additionally, the scarcity of new records for threatened species appears to support IUCN assessments of their poor stock status. The spread of ATRs suggests a growing pressure on the largest size classes in regions with previously little trophy fishing pressure. We encourage the greater use of catch‐and‐release initiatives and mandatory data collection for all near records to better quantify trophy fishing pressure and ensure sustainable practices.

Freedivers harvest thousands of sea turtles a year in the Solomon Islands

Abstract Sea turtles are harvested in many small‐scale fisheries (SSFs), but few nations have quantified the impacts that SSFs are having on their sea turtle stocks. This study provides the first assessment on the catch composition, national harvest rates, and long‐term trends in sea turtle catches in the Solomon Islands SSFs. Between October 2016 and May 2018, 10 community monitors located in eight of the nine provinces of the Solomon Islands were trained and employed to work alongside fishers in their respective communities to document, photograph, and georeference the reefs where sea turtles were harvested. Local ecological knowledge (LEK) surveys were then conducted with 32 experienced fishers to infer whether the harvest rates of sea turtles had changed in recent decades. Community monitors recorded information on 1,132 sea turtles that were harvested on 529 fishing trips: 1,119 sea turtles were identified to species level, with harvests consisting of 73.3% (n = 818) green sea turtles (Chelonia mydas), 25.7% hawksbill sea turtles (n = 291) (Eretmochelys imbricata), and 0.9% (n = 10) olive ridley sea turtles (Lepidochelys olivacea). The great majority (92.6%) of sea turtles were captured by night‐time and daytime freedivers who use masks, snorkels, fins, hooks, spears, and underwater flashlights to target a wide range of fauna that inhabit coral reefs. A methodology that accounts for spatial heterogeneity in sea turtle catch rates was used to estimate that the SSFs of the Solomon Islands harvested 11,184 sea turtles per year, with a 95% confidence interval of 5,862–23,717 sea turtles. Experienced freedivers reported a 4.9‐fold decline in sea turtle harvest rates over the past 30 years, indicating that the sea turtle stocks of the Solomon Islands are being overfished. The results and recommendations from this study were integrated into the Solomon Islands National Plan of Action for Marine Turtles 2023–2027.

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

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

Evolution of catches and specific composition of elasmobranchs in Mauritanian artisanal, coastal and offshore fisheries

Elasmobranchs are among the most vulnerable marine fish and the most impacted by fishing. In Mauritania, although many management and prohibition measures have been introduced, this taxonomic group continues to be caught and landed. To follow trends of catches and catch species composition by the different fishing fleets in Mauritania we used the data from the fisheries monitoring system set up by the Mauritanian Institute of Oceanographic Research and Fisheries (IMROP) collected since 2006 in the National Park of Banc d′Arguin (PNBA). These data are supplemented by the monitoring data on the artisanal, coastal, and deep-sea fisheries, and the data from the scientific demersal trawling campaigns in the Mauritanian Exclusive Economic Zone (EEZ) that IMROP has been conducting since 1982. The results show that elasmobranch catches are highest in the artisanal and coastal fisheries, particularly in the PNBA, where several conservation measures for these species have been put in place. These results suggest that there is a need to strengthen the implementation of the shark management plan by a strict application of the prohibition of gear targeting these species.