Fishing Intensity Research Articles

Fine spatio-temporal prediction of fishing time using big data

Overfishing, bycatch, and other anthropogenic threats may lead to the destruction of fragile habitats and substantial losses of marine life. Marine fishery resources can be protected by adjusting fishing intensity and establishing marine reserves. Currently, China adopts the closed fishing season management approach to protect traditional fishing grounds, where fine spatio-temporal prediction is essential to efficiently supervise the wide scope. Fishing vessel behaviors reflect fishers’ experience as well as the information provided by fish detection radar, while the fishery resource distribution is relevant to the marine environment. In this study, we identified fishing vessel behaviors (gillnets, trawls, purse seines, and abnormal behaviors) and qualitatively assessed and predicted fishing time of different fishing vessel behaviors to search for high intensity fishing operation areas by constructing a time-space prediction model. The model was based on big data of fishing vessel automatic identification systems and3 the marine environment, and was verified in the East China Sea. The prediction results generally corresponded with the distribution of traditional fishery resources in the East China Sea and the fishing efforts provided by the Global Fishing Watch. This model can provide an accurate and effective refined fishing vessel operation time prediction, and benefits fishing management and fishery resources protection.

Harnessing multimodal data fusion to advance accurate identification of fish feeding intensity

Accurately identifying the fish feeding intensity plays a vital role in aquaculture. While traditional methods are limited by single modality (e.g., water quality, vision, audio), they often lack comprehensive representation, leading to low identification accuracy. In contrast, the multimodal fusion methods leverage the fusion of features from different modalities to obtain richer target features, thereby significantly enhancing the performance of fish feeding intensity assessment (FFIA). In this work a multimodal dataset called MRS-FFIA was introduced. The MRS-FFIA dataset consists of 7611 labelled audio, video and acoustic dataset, and divided the dataset into four different feeding intensity (strong, medium, weak, and none). To address the limitations of single modality methods, a Multimodal Fusion of Fish Feeding Intensity fusion (MFFFI) model was proposed. The MFFFI model is first extracting deep features from three modal data audio (Mel), video (RGB), Acoustic (SI). Then, image stitching techniques are employed to fuse these extracted features. Finally, the fused features are passed through a classifier to obtain the results. The test results show that the accuracy of the fused multimodal information is 99.26%, which improves the accuracy by 12.80%, 13.77%, and 2.86%, respectively, compared to the best results for single-modality (audio, video and acoustic dataset). This result demonstrates that the method proposed in this paper is better at classifying the feeding intensity of fish and can achieve higher accuracy. In addition, compared with the mainstream single-modality approach, the model improves 1.5%–10.8% in accuracy, and the lightweight effect is more obvious. Based on the multimodal fusion method, the feeding decision can be optimised effectively, which provides technical support for the development of intelligent feeding systems.

Effect of Additional Dried Tubifex sp. in Commercial Feed Against Color Intensity of Guppy (Poecilia reticulata)

Guppy fish (Poecilia reticulata) is a type of ornamental fish that is in great demand, because of its small size and beautiful color. The color of ornamental fish will generally fade, due to a lack of carotenoids in their feed. The purpose of this study was to determine the effect of giving Tubifex sp. in commercial feed to increase the color intensity of guppy fish and the best dose of Tubifex sp. The test fish used were male guppy fish strain HB Red. This study used a completely randomized design (CRD) method with five treatments and three replications, that is commercial feed with the addition of Tubifex sp. with doses of 0% (P1), 2% (P2), 4% (P3), 6% (P4), and 8% (P5). Parameters observed were color intensity (chroma value), survival, and water quality. Addition of Tubifex sp. in commercial feed gave the effect with the highest yield on P5 at a dose of 8%, with an increase in color intensity (chroma value) of 4,21±0,25d. At P1 it gave an increase of 1,19±0,02a, P2 was 1,34±0,04a, P3 was 1,81±0,21b, and P4 was 2,88±0,18c. So, the best treatment is P5 (8%). Survival showed the results were not significantly different, that is 100%. Water quality is included in the tolerance limit of fish with the results of temperature 26,6 – 27,4°C, pH 7,4 – 7,9, and DO 6,2 – 7,7 mg/L.

Baseline Inventory of Benthic Macrofauna in German Marine Protected Areas (2020-2022) before Closure for Bottom-Contact Fishing.

The response of benthic habitats and organisms to bottom-contact fishing intensity is investigated in marine protected areas (MPAs) of the German EEZ in the North and Baltic Seas. We examined the current state of macrofauna biodiversity in 2020-2022. Comparative analysis for macrofauna (in- and epifauna) inhabiting nine Natura 2000 MPAs constitutes a baseline to assess the effects of bottom-contact fishing exclusion in the future. Aspects of spatial and temporal variability are briefly summarized and discussed. We provide a species list for each region, including 481 taxa, of which 79 were found in both regions, 183 only in the North Sea, and 219 only in the Baltic Sea. The Baltic Sea dataset surprisingly included higher numbers of taxa and revealed more Red List species. The share of major taxonomic groups (polychaetes, bivalves and amphipods) in species richness showed peculiar commonalities between the two regions. In the North Sea, multivariate analysis of community structure revealed significantly higher within-similarity and stronger separation between the considered MPAs compared to the Baltic MPAs. Salinity, temperature and sediment fractions of sand were responsible for over 60% of the variation in the North Sea macrofauna occurrence data. Salinity, mud fraction and bottom-contact fishing were the most important drivers in the Baltic Sea and, together with other considered environmental drivers, were responsible for 53% of the variation. This study identifies aspects of macrofauna occurrence that may be used to assess (causes of) future changes.

Feeding intensity identification method for pond fish school using dual-label and MobileViT-SENet

Accurately identifying the fish feeding intensity is crucial for timely understanding the feeding demand, dynamically adjusting the feeding strategy, and reducing costs. For the variability and uncontrollability of the pond aquaculture environment, the densities of feeding fish schools aggregating to the feeding point exhibit significant variations. Consequently, different densities of fish schools present inconsistent characteristics in the image, even under the same feeding intensity, making the precise identification of feeding intensity difficult. To tackle this issue, a method for identifying the feeding intensity of pond fish schools based on dual-label and MobileViT-SENet (DL-MobileViT-SENet) was proposed. The fish school images were marked with labels indicating density and feeding intensity to establish the dual-label dataset. Subsequently, a proposed MobileViT-SENet network is trained using the dataset to obtain the dual-label pre-training weight incorporating both fish density and feeding intensity features. Two models are trained to identify density and feeding intensity based on the obtained weight. Finally, a dynamic feeding strategy for fish that integrates biomass, density, and feeding intensity is presented. The proposed method combines the density and feeding intensity labels to enhance the accuracy of identifying the feeding intensity of pond fish schools across various densities, and lays the groundwork for designing a dynamic feeding strategy. It was tested on authentic pond fish school images and yielded an accuracy of 97.95%. This value is superior to these comparison methods, demonstrating that this method can accurately identify the feeding intensity of pond fish and provide support for formulating a dynamic feeding strategy.

Projecting contributions of marine protected areas to rebuild fish stocks under climate change

No-take marine protected areas (No-take MPAs) are considered as a major tool for conserving marine biodiversity and ecosystem services. No-take MPAs can also contribute to climate adaptation for exploited fish stocks. Meanwhile, many fish stocks in the world are overfished and management institutions are developing plans to rebuild them. Understanding the potential effects of no-take MPAs on fish stocks under climate change can help develop strategies for climate-resilient stock rebuilding. Here, using a linked climate-fish-fishing model, we undertake simulation experiments to examine the effects of no-take MPAs on biomass and potential catches of 231 exploited fish and invertebrate species in eight marine ecoregions in the Northeast Atlantic under climate change. The simulations include different levels of fishing, no-take MPAs coverage, atmospheric global warming levels, and account for the expected displacement of fishing to the area around the no-take MPAs. Average individual stock biomass is projected to decrease by 5–15% per degree Celsius atmospheric warming. Having 30% of the distribution of over-exploited fish stocks under no-take MPAs together with conservation-focused fisheries management of these stocks are projected to offset the negative impacts on their biomass under 2.6–2.9 °C global warming. Meanwhile, potential catches increase when a portion of the over-exploited fish stocks is protected from fishing as higher biomass in the no-take MPAs spills-over to the surrounding areas. Our findings highlight that no-take MPAs, combined with reducing fishing intensity, can help rebuild over-exploited fish biomass and benefit their dependent fisheries in the Northeast Atlantic under projected climate change in the 21st century.

Russian fishing in the Atlantic and Southeastern Pacific Oceans in 2000–2020

The aim: to analyze the development of domestic fisheries in the Atlantic and Southeastern Pacific Oceans in 2000–2020, to assess the state of stocks and catch of the most important types of aquatic biological resources.Methods: conducting trawl-a coustic, ichthyological and hydrological accounting studies in 2000–2020. Analysis of domestic and foreign literature.Novelty: the article presents an up-to-date analysis of the development of Russian fishing, the intensity of fishing and the state of exploited stocks of commercial fish species.Results: Information is provided on the status and dynamics of stocks and catch of commercial aquatic organisms in various areas of the Atlantic and southeastern Pacific Ocean. During the period under review, the highest biomass of stocks and catch are observed in pelagic fish species in the North-East Atlantic. The state of stocks and catch of bottom fish species in the far North Atlantic regions are at an average or low level. In general, in the first two decades of the XXI century, favorable conditions for conducting domestic fishing were noted. For the Central-Eastern Atlantic area (EEZ of Morocco and Mauritania), information is provided on the status of the main commercial fish stocks. Particular attention was paid to the possibility of resuming the domestic tuna and mackerel fishery in the south-e astern Pacific Ocean.Practical significance: the results of the analysis can be used to make management decisions on the development and regulation of fishing.

On the critical abundance of the taimyr population of wild reindeer

The critical population for the existence of the Taimyr population of wild reindeer has been established. The processing of the initial information about the population size was performed using the apparatus of mathematical biology. The main practical task is to identify the lower limits of abundance and the critical load for the population, after which the collapse of this commercial population will occur. Also, regression equations were calculated for the total livestock of the population, the reproductive core (mature females) and juveniles (calves of the year) at different time intervals of the economic use of the resources of this population - Soviet and post-Soviet. For the Soviet period of using the resources of the population in 1969-1990 the parameters of the equation look like: y = 21.867x + 316.77 thousand (R2 = 0.886, Ᾱ = 6, rxy= - 0.41, p<0.05). For adult females, the trend equation for this segment of the reproductive cycles: y = 5.157x + 73.879 thousand, (R2 = 0.836). The total number of the population did not decrease: the average realized reproduction in this segment of the biological cycles is 61 calves per 100 mature females. In the post-Soviet period 1990–2021 equation of the linear trend of the Taimyr population: y = - 36.96х + 624.51 thousand (R2 = 0.75, Ᾱ = 5.18, rxy = 0.46, р<0.05). Evaluation by the straight-line trend equation of the juvenile group (calves of the year) gives a negative calculated value of the linear regression equation within y = - 21.4x + 175.51 thousand. (R2 = 0.944, Ᾱ = 2.9, rxy = 0.98, p<0.01). Such facts unequivocally signal the excess of the optimal intensity of fishing, because there is a gradual decrease in recruitment. The estimated critical number of the Taimyr population is 88.77 thousand wild deer, the critical limit of the fishery with a similar number is the removal of 71.9 thousand individuals. From here, hypothetically, only 16.87 thousand heads remain from the Taimyr population, which will lead to the collapse of this biological population.The critical population for the existence of the Taimyr population of wild reindeer has been established. The processing of the initial information about the population size was performed using the apparatus of mathematical biology. The main practical task is to identify the lower limits of abundance and the critical load for the population, after which the collapse of this commercial population will occur. Also, regression equations were calculated for the total livestock of the population, the reproductive core (mature females) and juveniles (calves of the year) at different time intervals of the economic use of the resources of this population - Soviet and post-Soviet. For the Soviet period of using the resources of the population in 1969-1990 the parameters of the equation look like: y = 21.867x + 316.77 thousand (R2 = 0.886, Ᾱ = 6, rxy= - 0.41, p<0.05). For adult females, the trend equation for this segment of the reproductive cycles: y = 5.157x + 73.879 thousand, (R2 = 0.836). The total number of the population did not decrease: the average realized reproduction in this segment of the biological cycles is 61 calves per 100 mature females. In the post-Soviet period 1990–2021 equation of the linear trend of the Taimyr population: y = - 36.96х + 624.51 thousand (R2 = 0.75, Ᾱ = 5.18, rxy = 0.46, р<0.05). Evaluation by the straight-line trend equation of the juvenile group (calves of the year) gives a negative calculated value of the linear regression equation within y = - 21.4x + 175.51 thousand. (R2 = 0.944, Ᾱ = 2.9, rxy = 0.98, p<0.01). Such facts unequivocally signal the excess of the optimal intensity of fishing, because there is a gradual decrease in recruitment. The estimated critical number of the Taimyr population is 88.77 thousand wild deer, the critical limit of the fishery with a similar number is the removal of 71.9 thousand individuals. From here, hypothetically, only 16.87 thousand heads remain from the Taimyr population, which will lead to the collapse of this biological population.

Mixed Eimeria and Cryptosporidium infection and its effects on pathology and clinical outcomes in juvenile Asian seabass (Lates calcarifer) cultured in Thailand.

Coccidiosis is an important disease in juvenile fish because of severe intestinal injury during infection. We first reported the mixed infection of intestinal coccidia and its association with health status and pathological findings in juvenile Asian seabass (Lates calcarifer) cultured in Thailand. Two groups of Asian seabass, 60-day fish and 90-day fish, were sampled to investigate prevalence and coccidian infection intensity using morphological characterization and PCR. Phylogenetic analysis of 18S rRNA gene amplified from the intestines revealed Eimeria sp. and Cryptosporidium sp. infection. The prevalence of Eimeria sp. and Cryptosporidium sp. in sampled fish was 100%. Clinical outcomes assessed, using health assessment index (HAI) scoring and semi-quantitative grading of intestinal lesions and inflammation, demonstrated that all fish developed variety of pathology and clinical illness; however, infection intensity in 60-day fish was significantly higher (p < .05) than 90-day fish. The HAI score of 60-day fish was poorer than 90-day fish, which correlated to a high infection intensity (r = .397), analysed by Pearson correlation coefficient. Overproduction of intestinal oxidants contributing to mucosal injury was examined by nitrotyrosine expression. The high production of reactive nitrogen species indicated severe inflammatory response, and intestinal injuries occurred mainly in the 60-day fish.

From dynamics to sustainability: Modeling the shrimp (Penaeus chinensis) fishery in Shandong, China

Since 1984, the stocking of shrimp juveniles has been implemented in the Bohai Sea, China as a strategy to manage the depleted marine fishery. Subsequently, major harvest restriction policies including “Dual Control” (1987), “Summer Fishing Moratorium” (1995), and “Fishermen Transfer and Fishing Fleet Scraping” (2003) were gradually implemented to reduce fishing intensity. However, the relative effectiveness of these three policy changes and management improvements, such as varying stocking quantity, adjusting the duration of the summer fishing ban, and reducing fishing intensity rate have rarely been assessed before their implementation. To address this gap, we developed a System Dynamic model that incorporated multiple scenarios related to these strategies in the shrimp fishery. Using Penaeus chinensis shrimp in the coastal province of Shandong, China, as a test case, we simulated the harvest metrics and stock size for each scenario. Our model predictions revealed that among the three strategies, extending the duration of the summer fishing ban is the most likely to improve the harvest metrics, while reducing fishing intensity significantly increases shrimp abundance. Based on the research findings, we recommend an optimal combination of the three strategies: releasing approximately 700 million individual juveniles per year, decreasing the fishing intensity rate to 0.65, and increasing the duration of the summer fishing ban to 123 days, from 1 May to 31 August. The research outcomes contribute to evidence-based decision-making and sustainable management practices in the Bohai Sea shrimp fishery and beyond.

Occurrence of new Philometra sp. in mangrove red snapper Lutjanus argentimaculatus from the Karachi coast, Pakistan.

A recent examination of Philometra nematodes from mangrove red snapper Lutjanus argentimaculatus (Forsskal, 1775) from the Karachi coast, Kemari was done in the years 2021-2022. The present study reported three new species of genus Philometra (Costa, 1845) (Nematoda: Philometridae) Philometra kolachii, Philometra lutjani and Philometra kemarii. A total of 140 fish samples were examined, and 76 were infected. The intensity of infected fish was 54.28%. In Pakistan, literature on Philometrid nematodes is limited, therefore, this research would be helpful for the documentation and enhancement of nematods in Pakistan.

New record of Philometra species from the marine edible fish Terapon jarbua collected from the Sindh, Arabian Sea, Pakistan.

Diseases in fish due to helminth parasites, especially Philometra species, are the primary worry in aquaculture. Philometra are responsible for health problem in fishes they directly affect fish growth and population parameters. A comprehensive survey was conducted involving the examination of the marine fish species Terapon jarbua, gathered from the coastal waters of Sindh, Pakistan In this research different Philometra species from marine fish Terapon jarbua during 2021 and 2022. Philometra nematodes, belonging to the family Philometridae, are common parasitic organisms inhabiting both marine and freshwater environments. Their prevalence, particularly when existing in high numbers within host organisms, can lead to severe and potentially lethal consequences. Employing light microscopy techniques, diverse species of Philometra were identified, including Philometra teraponi, P. jarbuai, P. arabiai, P. karachii, and P. awarii, localized primarily within the ovaries of the host fish. A total of 140 fish samples were examined and 76 were infected. The intensity of infected fish was 54.28%. The identification process encompassed meticulous analysis of crucial parameters, such as body size, esophagus length, positioning of the nerve ring, dimensions of the ventriculus, and ligament size. Intriguingly, the parasites were found in varying contexts; while some were free within the ovaries, others were embedded within tissues, inducing severe muscular dystrophy. This research presents novel findings of Philometra nematodes in the marine waters of Pakistan, extending their host and geographical distribution records. Future studies are needed to better evaluate and describe the dynamics and the epidemiology of Philometra infection in wild and cultured fish species.

Recognizing topological attributes and spatiotemporal patterns in spotted seals (Phoca largha) trophic networks based on eDNA metabarcoding

Spotted seals, a protected species, face multifaceted threats to their habitat, which in turn impact the closely associated trophic networks. These threats will lead to irreversible structural variations within the ecosystem. Therefore, investigating the topological variability of trophic networks in spotted seals is important. Applying environmental DNA methods, field sample collection was conducted in 2021 during both the sea fishing moratorium period and the fishing period to decode fish diversity. Assessing the current status of fish resources by using the multivariate statistics approach. Applying dietary information establishes the spotted seals’ trophic network. Selecting 12 network indexes to analyze the spatiotemporal patterns of network topological attributes. As a result, about 51 families, and 76 genera species were identified. During the sea fishing moratorium and the fishing period, there are 12 and 18 different food resources available for spotted seals, respectively. The diversity index revealed that the FP had greater species richness and diversity than the SP. Comparatively, the Fishing period exhibited higher species richness and biodiversity, likely influenced by habitat heterogeneity and anthropogenic activities. Additionally, the topological features of networks reflected the high clustering coefficients (CC=0.35) and the proportion of omnivorous species (O≈60%), indicating that the network structure in this region tends to form higher trophic-level clustering patterns, which facilitate the formation of weaker interactions between clusters, enhancing the robustness of the network. The higher connectivity complexity index during the fishing period (SC=12.3) supported that the spotted seal’s trophic network was relatively more stable in this period. Thus, during the fishing period, it is crucial to pay more attention to the intensity of human fishing on mid-to-high trophic-level omnivorous fish resources to ensure the sustainability of these potential food resources for spotted seals. This comprehensive study achieved three key objectives: (a) utilizing eDNA to characterize fish diversity during distinct periods, (b) establishing trophic networks of spotted seals, and (c) discerning topological attributes and spatiotemporal patterns within the ecological network. Overall, this study can provide technical and data support for integrated ecological network management and propose suggestions for protecting and recovering spotted seals.

Potential impacts of ocean warming on energy flow and fisheries production in an overexploited ecosystem: Implication for effective fisheries management

The influences of ocean warming on marine lives have accelerated over the 21st century, greatly altering the structure and function of marine food webs and causing distributional shifts, species invasions, and changes in productivity. It is imperative to clarify the overall ecosystem responses to ocean warming and develop fisheries management strategies adaptive to the ecosystem changes. In this study, the potential impacts of ocean warming on trophic structure, energy flows, and fisheries production of an overexploited ecosystem were examined, and the effectiveness of fisheries management in mitigating warming impacts were also evaluated. We constructed a mass-balance food web model in Haizhou Bay and simulated three climate scenarios (RCPs 2.6, 4.5, and 8.5) along with different levels of fishing pressure, in order to examine the ecosystem responses to the combined changes in fishing and climate changes. Results showed that the total biomass of commercial species and fisheries catches would decline with rising temperature, especially under the RCP8.5 scenario. Ocean warming could induce lower trophic transfer efficiency and decrease energy recycling capacity within the food web, leading to large losses in total biomass and total production. Reducing fishing intensity could help mitigate the negative effects of ocean warming on fisheries productivity, but was insufficient to maintain ecological properties. Moreover, the effectiveness of such alternative measures would be diminished with increased greenhouse gas emissions, especially under the climate scenario of RCP8.5. The findings of this study highlight the need to slow the rise of sea temperature and implement climate-adaptive fisheries management in the future.

Tuning social interactions' strength drives collective response to light intensity in schooling fish.

Schooling fish heavily rely on visual cues to interact with neighbors and avoid obstacles. The availability of sensory information is influenced by environmental conditions and changes in the physical environment that can alter the sensory environment of the fish, which in turn affects individual and group movements. In this study, we combine experiments and data-driven modeling to investigate the impact of varying levels of light intensity on social interactions and collective behavior in rummy-nose tetra fish. The trajectories of single fish and groups of fish swimming in a tank under different lighting conditions were analyzed to quantify their movements and spatial distribution. Interaction functions between two individuals and the fish interaction with the tank wall were reconstructed and modeled for each light condition. Our results demonstrate that light intensity strongly modulates social interactions between fish and their reactions to obstacles, which then impact collective motion patterns that emerge at the group level.

Bottom fishing beyond trawling. Spatio-temporal trends of mobile and static bottom fisheries on benthic habitats

The effective implementation of the Marine Strategy Framework Directive (MSFD) and formulation of spatial management policies rely heavily on a good understanding of the extent, distribution and intensity of human pressures and their overlap with benthic habitats. However, little research has quantified the pressure and impact on the seabed of bottom contact gears other than trawling. This study analyzes the spatio-temporal trends of fishing pressure of bottom-contact gear, including mobile and static gears, and asseses its relative importance within each benthic habitat. To achieve this, a set of pressure indicators was calculated using vessel monitoring system information from the Bay of Biscay for 2009–2020. Nested General Linear Models were conducted to assess the temporal fluctuation of fishing activities. While trawlers exhibited wider and higher levels of fishing intensity over sedimentary habitats, set gillnet and set longliners were distributed among more sensitive habitats, such as biogenic reef habitats. Additionally, there was a significant decrease in fishing effort in recent years along Offshore circalittoral habitats, particularly with respect bottom trawling, in contrast to increasing fishing intensity in deeper areas. These results emphasize that from a conservation perspective and MSFD implementation, there is a need to quantitatively analyze the fishing footprint of all fishing gears, including static gears in the regional assessments, and the necessity to progress in adapting impact indicators to these fishing activities. The findings are discussed based on the potential impacts of policies such as the MSFD and can assist managers in developing spatial protection measures.

Spatial-temporal variation of marine fishing activities responding to policy and social events in China

The spatial-temporal variation of the impact of political and social factors such as (Fishing Moratorium, Marine Protected Areas, New Year, and COVID-19) on fishing activities offshore was evaluated based on fishing efforts data by AIS from 2013 to 2020 for China. It is found that the maximum fishing intensity occurs within 20–30 km of the coastline, the area within 40 km of the coastline covers 51% of fishing activities, and within 100 km of the coastline accounts for 92% of fishing activities. From 2013 to 2016, fishing hotspots showed a highly aggregated spread in the Bohai Sea and the East China Sea. Since 2017, China's hot fishing areas have gradually fragmented and southern moved. During the fishing moratorium, the fishing efforts decreased by 51% compared to the pre-moratorium, and after the moratorium, the fishing efforts increased by 81% compared to the pre-moratorium on average. We investigated fishing activities in and around 249 MPAs in China and found that 71% of MPAs are free of fishing, and average fishing intensity across MPAs is 35% lower than not protected areas. Regarding the social events, it is concluded that during the New Year holiday, the fishing efforts and fishing area were reduced by 79% and 73%, respectively, compared to the regular fishing period. The COVID-19 epidemic prompted a decrease in fishing efforts in 2020 for the first time since 2013, with the average fishing efforts in 2020 being 14% and 6% lower than in 2019 and 2017 to 2019, respectively.

Evaluating the efficacy of fisheries management strategies in China for achieving multiple objectives under climate change

It is increasingly recognized that effective fisheries management needs to take into account not only the target species, but also the broader scope of biological, environmental, socio-economic and institutional factors pertaining to human utilization of fishery resources. This recognition has stimulated a global call for the Ecosystem-Based Fisheries Management (EBFM), with an increasing appreciation of its merits in the face of climate change. In this study, we applied the concept of EBFM to China's fisheries and tested the performance of various fisheries management strategies, including status quo management and alternative strategies with different objective priorities, under contrasting climate warming scenarios. We used the Ecopath with Ecosim (EwE) as an operating model, with an explicit consideration of trophic interactions, and specifically quantified the trade-offs across multiple metrics (i.e., sustainable fishery production, economic profitability, seafood security, and ecosystem health). No single strategy was superior across all the four dimensions. Importantly, the existing approach to fisheries management underperformed in most metrics, with the current fishing intensity exceeding the level that would maximize multispecies yields (fMSY) and total profits (fMEY). In contrast, an alternative harvest control rule (HCR) strategy, designed to respond to variations in biomass, provided inherent resilience of the ecosystem under climate warming, resulting in increased commercial fish biomass, improved profit and seafood supply, as well as enhanced ecosystem structure and function across various time-climate scenarios. From a tactic perspective, the multiple species management strategies of “fMSY” and “fMEY” can be better suited for the highly mixed fishery context in China. These alternatives also consistently demonstrated superior performance compared to the existing fisheries management strategy. Our work reveals potential trade-offs among diverse ecosystem services and provides a framework using EwE model for quantifying possible performance of management strategies under climate change, leading to more informed and transparent decision-making.

Phytoplankton control by stocking of filter-feeding fish in a subtropical plateau reservoir, southwest China

Stocking of filter-feeding fish (mainly Hypophthalmichthys molitrix and Aristichthys nobilis) is a common method used in lakes and reservoirs in (sub)tropical China to control phytoplankton, but the results are ambiguous and lack long-term data to support. We analysed a decade (2010-2020) of monitoring data from a subtropical plateau reservoir, southwest China, to which filter-feeding fish were stocked annually. We found that the total phytoplankton biomass, cyanobacteria biomass and average individual mass of phytoplankton decreased significantly during the study period despite absence of nutrient concentration reduction. However, the grazing pressure of zooplankton on phytoplankton also decreased markedly as judged from changes in the ratio of zooplankton biomass to phytoplankton biomass and Daphnia proportion of total zooplankton biomass. This is likely a response to increasing predation on zooplankton by the stocked fish. Our results also indicated that water temperature, total phosphorus and water level promoted phytoplankton growth. Our results revealed that filter-feeding fish contributed to the decline in the biomass of phytoplankton but that it also had a strong negative effect on the grazing pressure of zooplankton on phytoplankton, even in this deep reservoir where zooplankton may have a better chance of survival through vertical migration. The particular strong effect on zooplankton is most likely due to imbalance of stocking and harvesting of fish. In the management of eutrophic reservoirs, the reduction of external nutrient loading should have highest priority. In highland (low temperature) deep-water eutrophic reservoirs, stocking of filter-feeding fish may help to control filamentous phytoplankton provided that the fish stocking is properly managed. The optimal stocking intensity of filter-feeding fish that can help control phytoplankton in such reservoirs without excessive impact on large-bodied zooplankton is a topic for further elucidation, however.

Greenland halibut stock state and fishery magement in the Barents Sea

The subject of this article is an assessment of reference points and the state of the black halibut stock in the Barents Sea. Despite the abundance of information accumulated over the years of fishing and research, the uncertainty of the dynamics of the stock remains quite high. The article describes and analyzes all currently known sources of information about the state of the stock –data from surveys, fishing statistics and the age structure of catches. Several types of models are being built – production models and age-structured model. The MSY value at the level of 28–32 thousand tons were obtained as a result of applying three different approaches to stock modeling: production models, combining cohort and production models and constructing a yield-recruit curve based on cohort models data. Despite the much greater uncertainty in the estimates of biomass, the current fishing intensity can be considered close to optimal based on the estimates obtained.