Fisheries Data Research Articles

Combining fishery data through integrated species distribution models

Abstract Species Distribution Models are pivotal for fisheries management. There has been an increasing number of fishery data sources available, making data integration an attractive way to improve model predictions. A wide range of methods have been applied to integrate different datasets in different disciplines. We focus on the use of Integrated Species Distribution Models (ISDMs) due to their capacity to formally accommodate different types of data and scale proportional gear efficiencies. ISDMs use joint modelling to integrate information from different data sources to improve parameter estimation by fitting shared environmental, temporal and spatial effects. We illustrate this method first using a simulated example, and then apply it to a case study that combines data coming from a fishery-independent trawl survey and a fishery-dependent trammel net observations on Solea solea. We explore the sensitivity of model outputs to several weightings for the commercial data and also compare integrated model results with ensemble modelling to combine population trends in the case study. We obtain similar results but discuss that ensemble modelling requires both response variables and link functions to be the same across models. We conclude by discussing the flexibility and requirements of ISDMs to formally combine different fishery datasets.

Bringing in the experts: application of industry knowledge to advance catch rate standardization for northern shortfin squid (Illex illecebrosus)

Sources of fisheries information outside of fishery-independent surveys (e.g. fishery-dependent data) are especially valuable for species that support productive fisheries and lack reliable biological information, such as the northern shortfin squid (Illex illecebrosus). Fishery-dependent data streams are available for most species, however collaboration with industry members is critical to ensure that these fishery-dependent data are collected, applied, and interpreted correctly. Despite the need for collaboration and the frequency that fishery data are used in scientific research, there is limited literature on the structure of interactions and knowledge sharing that inform the analysis and application of fishery data. Between 2019 and 2022, a group of researchers collaborated with members of the northern shortfin squid fishing industry to bring together research data sets and knowledge from harvesters and processors to better describe the fishery dynamics, distribution, life history, and oceanographic drivers of the species. The collaboration focused on developing custom standardized fishery catch per unit effort (CPUE) indices to provide indicators of population trends that accounted for the impacts of technical and economic aspects of harvesting, processing and marketing on fishing effort, selectivity and landings of northern shortfin squid. We describe the methods used to inform and interpret the CPUE analyses, focusing on novel structure of interactions we had with industry members, and suggest best practices for integrating industry knowledge into CPUE standardization. The information shared and research products produced through this science-industry research collaboration advanced understanding of northern shortfin squid population and fishery dynamics, and contributed directly to the 2022 stock assessment and management process. Given the complex and stochastic nature of the northern shortfin squid population and fishery, we found it critical to maintain open communication and trust with processors and harvesters, who have unique insight into the factors that may be driving changes in catch, landings, and productivity of the valuable resource species.

The road to incorporating Scottish pelagic industry data in science for stock assessments

Fisheries data collection through industry-science partnerships have significant potential to support stock assessments and sustainable management, but few studies have described the steps taken en route to a successful partnership. This paper describes the development of the Scottish Pelagic Industry-Science Data Collection Programme; why and how it started, and what it has taken to develop a routine and consistent voluntary sampling regime of sufficient quality to become the main source of biological data on pelagic fish catches in Scotland. Using our experience, we emphasise the importance of establishing procedures that ensure the quality of methods and results, of working with institutions responsible for provision of national data, and of actively engaging with the International Council for the Exploration of the Sea (ICES) workshops and working groups on data quality, stock assessment and stakeholder engagement. The development of the programme has been, and remains to be, a mutual learning process which is reflected upon from our different institutional perspectives. The experience gained during this work has built knowledge useful for practitioners in other situations. Specifically, we identify five transferable design principles that we believe have been essential to success so far. Finally, we look at the steps ahead in our efforts toward continuous improvements.

Survey Evaluation of Florida’s Freshwater Fisheries Long-Term Monitoring Program

Natural resource monitoring programs benefit from routine evaluation. Here, Florida’s statewide Freshwater Fisheries Long-Term Monitoring (LTM) program is used to show how stakeholder surveys can be integral to this process. In 2022, an online questionnaire was sent to internal stakeholders, i.e., state agency personnel who collect, enter, or use freshwater fisheries data for fisheries and habitat management purposes. The survey’s primary objective was to evaluate the program at its 15-year mark; secondary objectives were to compare results with a similar survey conducted at the 4-year mark, compare results among respondents based on experience and functional role, and develop recommendations for strategic initiatives to further improve the program. The survey consisted of 43 questions across six sections of program evaluation: demographics; field sampling; data entry, summary, and reporting; management decision support; programmatic views; and additional input. Respondents generally had positive views of the LTM program, but the survey revealed differences among respondents with different functional roles (e.g., fisheries researchers and managers viewed the decisional value, priority, and sample sizes of LTM data more favorably than habitat managers) while highlighting high-priority future initiatives (e.g., database development). Our results demonstrate the utility of stakeholder surveys as an important step in evaluating monitoring programs.

Spatial awareness: Good practices and pragmatic recommendations for developing spatially structured stock assessments

Spatial population structure is a fundamental aspect of marine populations, yet it is rarely incorporated in stock assessment models. The unit stock assumption, a common feature of many assessments, is an axiom of the single-species modeling convention, which developed in the mid-20th century when the spatial resolution of fishery data was coarse and uncertain, computing power limited, and the impact of biocomplexity on sustainable harvest levels not well understood. Despite rapid advances along all of these research fronts in the 21st century, spatial assessments remain rarely utilized as the basis of management decision-making. A potential hindrance to broader utilization of spatial stock assessments is the lack of guidance on how to choose an appropriate spatial modeling framework for a given application. Thus, we review the types of spatial assessment models available, summarize options to parameterize population structure, offer guidance to promote the development of candidate spatial assessment models for application in management procedures, and provide a pragmatic guide for choosing a spatial assessment model given observed spatial structure, data limitations, and management concerns. A spatial assessment should match the assessment unit(s) to interdisciplinary stock identification of unit populations, adequately represent the spatial structure within an assessment unit, simultaneously model multiple interacting population units, when appropriate, and provide outputs for managers that can be used to prevent local depletion of spawning populations. As data permits, higher resolution intra-population spatial structure can be addressed to increase homogeneity within the modeled unit, while connectivity among population units may also be explicitly incorporated. Small sample sizes can limit spatial assessment applications, but incorporating novel data sources and parameterizing models efficiently (e.g., sharing parameters among spatial units, implementing habitat preference functions to improve movement dynamics, and including spatial autocorrelation) can resolve some practical constraints. Management strategy evaluation should be more widely utilized to identify minimally complex management procedures that provide robust advice, while imprecision of spatial models should be weighed against the inherent bias of spatially aggregated assessments.

Dynamics of the age composition of the red king crab males in the Barents Sea

The aim of the work was to develop an algorithm for analysis and to elucidate the trends in the dynamics of the age composition of red king crab males in different areas of the Barents Sea.Materials were the data of research surveys and fisheries monitoring obtained in 2001–2022, as well as published results of long-term observations on juveniles and tagging.As results, an original algorithm which makes it possible to determine the age composition of the catches of red king crab males is suggested. The mean carapace widths of individuals of age 4+ — 11+ are 78, 99, 121, 142, 164, 185, 207, 228 mm respectively. The combination of the Hiat linear growth model with assumption of the normal distribution of size frequencies in the age class made it possible to give an adequate description of the dynamics of the age composition of king crab males in the Barents Sea. In each area to the west and east of 36 ° E. the number of noticeable generations exceeds that obtained from the size composition data. Noticeable generations appear with different annual frequency, and one can find different generations in different areas in the same years. It is suggested that 3 spatially isolated local populations inhabit in the (1) Varanger-Fjord, (2) in the area between the Motovsky and the Teribersky bays, (3) off the coastal area to the east of 36°E. If the generation of the age 5+ consider as recruitment, it seems that noticeable recruitment in the Varanger Fjord is formed in the closed bays of its southwestern part. The recruitment in the second region, is also formed in closed bays. In the third local population, recruitment is currently formed in the open areas of the shelf, while the coastal areas are gradually turning into eviction zone of the large males.Practical value. The obtained results can improve the efficiency of management of the red king crab stock in the Barents Sea and adjacent waters.

Population Analysis of Bali Sardinella (Sardinella lemuru, Bleeker 1853) Landed in PPI Kedonganan using Length-Weight Data and Digital Analysis (ImageJ)

Sardinella lemuru, one of the important pelagic fish in Bali Strait waters, has been reported to be in the overfishing condition. Various studies have been conducted to understand its population condition. Length-weight data has been also widely used to understand the population dynamic of S. lemuru, although data collection generally using manual direct measurement methods, which has the disadvantages if used on the enormous number of samples. Therefore, this research aims to understand the significance of S. lemuru length measurement using digital image analysis (ImageJ) compared with the manual measurement. Moreover, this research also aims to understand the population condition of S. lemuru landed in PPI Kedonganan analyzed using its length-weight data. The result indicated no significance difference between length measurement using manual methods and digital image methods, thus conclude that digital image data can be used to measure the fish length and represent the accurate measurement. Population condition analysis showed that S. lemuru population is in isometric condition (b=3); with indication of declining in the length growth pattern compared with previous research (L∞= 20.75 cm with K= 1.1); the mortality estimation showed that fishing mortality (F=1.27) was lower than natural mortality (M=2.22), with the survival rate higher on smaller size fish. This research result can be used as an addition to the S. lemuru fisheries data and can also be used as reference methods to help conduct sampling and data collection more efficiently.

No free lunch: estimating the biomass and ex-vessel value of target catch lost to depredation by odontocetes in the Hawai‘i longline tuna fishery

Depredation by marine predators causes economic losses and impacts depredating species and fish stocks. To understand these impacts, it is important to accurately estimate catch losses from depredation. Pelagic longline fisheries are susceptible to depredation, and depredation is difficult to quantify, because gear is suspended in the water column away from the vessel for extended periods. In the present study, we used fisheries data and a novel modeling approach to estimate catch removal by odontocetes in the Hawai‘i deep-set longline fishery. We estimated annual biomass and economic value lost to depredation of three of the most commonly landed species as approximately 100 t and 1 million USD, respectively, during 2012–2018. The median cost on sets when depredation occurred was $600 USD, with the worst 10% of sets experiencing losses exceeding $2300 USD. We also identified broad-scale spatiotemporal patterns and hotspots of depredation across the range of the fishery. Our findings quantify the ecological and economic implications of this interaction, and our methods can be applied in similar fisheries elsewhere to assess the impacts of depredation.

Fishing methods and fishing season of the tropical lobster fisheries of Southern Java, Indonesia

Abstract. Setyanto A, Sumarno, Wiadnya DGR, Prayogo C, Kusuma Z, West RJ, Tsamenyi M. 2023. Fishing methods and fishing season of the tropical lobster fisheries of southern Java, Indonesia. Biodiversitas 24: 778-783. Tropical lobster fisheries represent a relatively small-scale but valuable export industry in Indonesia, but in many ways may fall within the category of Illegal, Unreported and Unregulated (IUU) fisheries. The absence of useful fisheries information means the management strategies and plans to manage the fisheries is severely limited. This research aimed to provide information about the fishing gear, methods, and fishing season of the fisheries, as a precursor to the development of fisheries management strategies. The study was conducted at Watukarung, Pacitan (East Java) and Baron, Gunungkidul (Yogyakarta). Fisheries data on lobster catch, fishing methods and fishing effort were collected through direct observation and interviews with fishers, fishery officers and port managers. Catch data were analyzed using ordinations technique to determine the fishing season. Lobsters were captured in various fishing gears throughout the year, but fishers targeting lobsters primarily used specialized lobster nets deployed by small boats and “krendet” (traps) deployed from clifftops as well as from small boat. The main fishing season for lobsters was from November to February each year. Future research needs to investigate fishing capacity and population parameters before any comprehensive fisheries management can be undertaken.

Diversity and characteristics of commercial Red Sea fish species based on fish market survey: informing management to reduce the risk of overfishing.

In small-scale fisheries (SSFs), where the sampling of many small boats and landing sites sometimes is not practical, fish market surveys represent an alternative way to obtain key fisheries data. This study analyses the diversity and characteristics of commercial Red Sea fish species landed in the Egyptian coast, including family, species-specific abundance, biomass, size and price by surveying the largest local fish market on the Egyptian Red Sea coast, over the course of a year (July 2021-June 2022) to also reflect any seasonality of these variables. Based on 53 survey visits, a total of 131,795 fish individuals, belonging to 111 species, and 22 families, were identified, recorded and measured. The analysis focused on the 60 most abundant species (104,420 individuals, 15 families). The surveys revealed that the most abundant families were Serranidae, Lethrinidae and Scaridae. Carangidae also was one of the most important families in terms of biomass. The most abundant species were Lethrinus mahsena, Sargocentron spiniferum and Lethrinus nebulosus. About 60% of revenue comes from the four families Serranidae, Lethrinidae, Scaridae and Lutjanidae. In terms of prices, the most expensive categories were species belonging to Serranidae, Lethrinidae and Lutjanidae families, such as Plectropomus pessuliferus marisrubri, Argyrops spinifer, L. nebulosus and Variola louti. The overall mean prices were higher in spring and summer months likely due to tourism flows. The mean size of many species, including the most valuable and abundant ones, is below the length of maturity. These results provide important benchmarks for monitoring future changes and shed important insights for fisheries management. Co-organised Dutch auctions would provide reliable data when combined with a strict monitoring effort to avoid any sale of the catch outside these official auctions. Other monitoring tools and methods are also recommended in the discussion.

Death Assemblages Record Significant Range Contraction in a Molluscan Species of Concern from the Eastern Gulf Of Mexico

Marine habitats are in decline due to increasing anthropogenic pressures, but baseline data on species distributions needed to manage and conserve populations are lacking. Incorporating death assemblages into species assessments can create a more accurate understanding of pre-anthropogenic communities than survey records alone. In this study, we conducted a live-dead analysis on mollusks from a new 2008-2018 dredge survey in the eastern Gulf of Mexico. We selected the predatory banded tulip snail, Cinctura hunteria, as a test case for assessment because this species is one of several designated by the Florida Fish and Wildlife as a species of concern. Using spatial count data for shells in our samples, we estimated density values for each taxonomic grade over the sampled area using IDW spatial interpolation. These maps reveal large areas of occupation across the west Florida shelf for two taxonomic grades of dead shells but loss of offshore occurrence for live records. One explanation for the lack of occurrences in offshore habitats is that, unlike dead shell records, there is no time averaging accumulation of live shells. Time averaging increases detectability of species in habitats where they are rare. However, independent fisheries data from live-only animal surveys not only mirror our live-dead results but suggest that habitat loss in our live-dead comparisons was rapid and occurred in the late 1980s or early 1990s. Thus, live-dead comparisons reveal both natural baselines as well as anthropogenic changes in distribution without being significantly distorted by time-averaging biases. Including live-dead data can greatly improve species assessments when long-term survey records are unavailable and provide a key tool in combatting biodiversity loss across marine ecosystems.

Geographic variation in external morphology of North Pacific and Southern Hemisphere blue whales (Balaenoptera musculus)

Geographic variations in size and proportions of blue whales (Balaenoptera musculus) were investigated using length data acquired from whaling records and aerial photogrammetric surveys. Results showed that blue whales found in the eastern Pacific off Central and North America are significantly shorter (by approximately 2m) than blue whales found at higher latitudes in the North Pacific. Results support the occurrence of a morphologically distinct eastern North Pacific (ENP) blue whale population which migrates in spring/summer from warm waters off Central America and Mexico to temperate feeding grounds along the west coast of North America. Southern Hemisphere blue whales sampled with vertical aerial photogrammetry off northern Peru and the Galapagos Islands were similar in size to the ENP blue whales. However, the population affinity of these southern blue whales remains uncertain. No length data were available for blue whales formerly captured off southern Japan and Korea. Nonetheless, a history of diminishing fishery catches and a lack of any recent sightings suggests that these whales were members of a geographic population that is now severely depleted or extinct. Based on comparisons of total length, length of rostrum and length of tail region, ENP blue whales were found to be morphologically similar to the ‘pygmy’ blue whale (B.m. brevicauda) described from the Kerguelen Island region of the southern Indian Ocean. ‘Antarctic’ blue whales (B.m. intermedia) from the Southern Ocean were found to be statistically significantly larger than their conspecifics at high latitudes in the North Pacific. These results support the hypotheses that blue whales that migrate from warm seas to cold feeding grounds in high latitudes are larger than those whose distributions are limited to low and mid-latitudes. Differences in morphology may reflect selective pressure on populations to adapt physiologically to energy demands associated with different migration, environmental and ecological regimes. As some of the results come from populations located far apart in different oceans, questions remain concerning the continuity of populations within and among ocean basins. Consequently, research using fishery data and approaches such as photogrammetry, telemetry, acoustics and molecular genetic analysis should be continued to better understand the worldwide blue whale population structure.

Mobilizing the fishing industry to address data gaps created by shifting species distribution

Globally, climate change is inducing range shifts and expansions for numerous species. For commercially exploited species, such as those in directed fisheries, this can cause numerous issues with management and jurisdictions as the species shift and expand into areas at levels previously unseen. The black sea bass (Centropristis striata) fishery has rapidly expanded in the northern Atlantic. Over the past decade commercial landings have more than doubled in the New England and Mid-Atlantic regions. This increase is related to a northward shift in the species’ center of biomass and range expansion. There is a crucial need for increased data in this species’ northern range. Oftentimes, large-scale fisheries data collection is limited by available resources and the difficulty of collecting data at-sea. Citizen science, such as fishing industry-based Research Fleets, represent a cost-effective option to help overcome these limitations and allow for the rapid collection of large amounts of data. The Commercial Fisheries Research Foundation and Rhode Island Department of Environmental Management established the Black Sea Bass Research Fleet in 2016. The Research Fleet is composed of fishers representing a variety of gear types who collect fishery-dependent data on black sea bass at-sea on a custom tablet application. In five years, 20 captains participated in the Research Fleet and collected length, visually-identified sex, and disposition data on 40,939 individual black sea bass throughout southern New England and into the Mid-Atlantic Bight. Catch, effort, and basic environmental data from 2,288 sampling sessions have been collected alongside this biological data. We apply the collaborative Research Fleet approach to a finfish for the first time and evaluate its performance over the first five years of sampling through participant engagement, magnitude of data collection, and interest in collected data. Further, we introduce the next steps being undertaken to incorporate the collected data into the management framework. This project illustrates that a science-industry research collaboration such as the Black Sea Bass Research Fleet can consistently collect large amounts of fishery-dependent data on black sea bass, and highlights a mutual interest among fishers, scientists, and managers to expand the collection of reliable data on this important species.

Size Structures, Length-Weight Relationships and Condition Factors of Synodontis obesus (Boulenger, 1898: Siluriformes, Mochokidae) in the Lower Cross River, Nigeria

Size Structures, Length-Weight Relationships and Condition Factors of Synodontis obesus ((Boulenger, 1898: Siluiformes, Mochokidae) were carried out with standard methods in the Lower Cross River, Nigeria to assess the population dynamics of the rarely studied but commercially important species. A total of 241 specimens (124: wet season and 117: dry season) were collected at Ayadehe Head Bridge fishing port in Itu Local Government Area, Akwa Ibom State, Nigeria from August 2020 to January 2021. The overall abundance showed high size variability within months and between seasons. The total biomass of the specimens collected was heavier in the wet season (12020.33g =12.02Kg) than in the dry season (10709.3g =10.7Kg) with an overall biomass of (22729.63g =22.7Kg). The overall size structures were: 15.0 – 28.30 cm, mean: 21.52.44 cm TL; 12.0 – 20.5 cm, mean: 15.881.6 cm SL and 13.20 – 21.50 cm, mean: 16.881.64 cm FL. The total weight of the species varied from 42.30 – 166.0g with overall mean value of 94.31603g. The length and body weight of fish samples caught for both wet and dry season were significantly different (p<0.05).The length composition of the species exhibits unimodal, bimodal and trimodal growth patterns. The species had heterogeneous groups or cohorts (1+, 2+ and 3+) with variation in body weight. The length-at-first maturity of S. obesus was 20.85 cm mid length. Growth coefficient (b) varied between (2.497) for the wet season and (2.617) for the dry season respectively with the mean growth coefficient (b=2.532) in the LWR (W= aLb). The species exhibited negative allometric growth pattern with an increase in length resulting to increase in weight of the fish. The condition factor (K) decreased with increased in the size of fish and ranged from 2.17-2.57 (Mean: 2.35) in both wet and dry seasons. The average condition factor (K) (2.35±0.15) was 1.0 for both seasons revealing that the species was in good physiological state of well-being. The condition factor (K) of S. obesus by size category showed K-values for recruitssexually mature fishaged fish. Thus fish size is an exponential index of condition factor. The results of this study constitute valuable fisheries data that would enhance the availability, conservation, valorization, exploitation and sustainability of S. obesus in the Lower Cross River, Nigeria.

Comparative assessment of the U.S. State of Florida’s Marine Life regulations for its commercial marine aquarium fish fishery

Governments in select locales around the world have recently either restricted or closed commercial marine aquarium fisheries, impacting the livelihoods of fishers, traders, and others who depend on them. This paper offers an objective assessment of Florida's commercial marine aquarium fish fishery and its regulatory landscape to inform and guide stakeholders about management strategies for the fishery moving forward, and to highlight successful regulations in place in Florida that merit consideration for adoption in other source locales around the world. The study discovered that the State has a strong regulatory structure for the commercial fishery operated by the Florida Fish and Wildlife Conservation Commission; practicing co-management with fishers, and utilizing license and permitting requirements, conventional fisheries management measures and technical actions to regulate fishing mortality, and rights-based management approaches. Additionally, both fisheries-independent and dependent surveys have been conducted in recent years to assess the fishery. Consequently, the vast majority of fish species collected commercially for the trade indicate stable or increasing catch trends in Florida waters over 10 + years. Moving forward, the fishery can benefit from an assessment of the economic impacts of the regulatory framework on its fishers, a statewide fisheries management plan specific for the fishery, the further development of a comprehensive program for fisheries data collection and analysis to address data gaps, an assessment of resources at hand and those needed to implement these recommendations, and the elevation of marine aquarium fisheries for support at the national level to support state-level management.

Spatiotemporal distribution of Lophius litulon in the southern Yellow Sea and East China Sea

In order to investigate the temporal-spatial distribution of yellow goosefish in the open waters of the southern Yellow Sea (SYS) and East China Sea (ECS), according to the fishery data by bottom-trawl surveys and environmental data including sea bottom temperature (SBT), sea bottom salinity (SBS), bottom concentration of dissolved oxygen (BDO) and depth during 2018-2019, we established habitat suitability index (HSI) models by arithmetic mean (AMM) and geometric mean (GMM) methods, and compared the model outputs by cross validations. Especially, the weight of each environmental factor was evaluated by boosted regression tree (BRT). Results showed that the area with the highest habitat quality varied among seasons. The yellow goosefish mainly inhabited in the adjacent area of the Yangtze River Estuary and coastal waters of Jiangsu Province with depth ranged from 22 to 49 m in spring. The optimal inhabitation was located in the SYS, with the bottom temperature ranged from 8.9-10.9 ℃ in summer and autumn. Particularly, the optimal inhabitation extended from the SYS to the ECS with bottom temperature ranged from 9.2-12.7 ℃ in winter. Results of BRT models showed that depth was the most important environmental factor in spring and bottom temperature was the crucial one in the other three seasons. Results of cross validation showed that the weighted AMM-based HSI model performed better for yellow goosefish in spring, autumn and winter. The distribution of yellow goosefish was closely related to its biological traits and environmental factors in the SYS and ECS, China.

The Environmental Niche of the Tuna Purse Seine Fleet in the Western and Central Pacific Ocean Based on Different Fisheries Data

Understanding the spatial pattern of human fishing activity is very important for fisheries resource monitoring and spatial management. The environmental preferences of tropical tuna purse seine fleet in the Western and Central Pacific Ocean (WCPO) were constructed and compared at different spatial scales based on the fishing effort (FE) data from the available automatic identification system (AIS) and commercial fishery data compiled from the Western and Central Pacific Fisheries Commission (WCPFC), using maximum entropy (MaxEnt) methods. The MaxEnt models were fitted with FE and commercial fishery data and remote sensing environmental data. Our results showed that the area under the curve (AUC) value each month based on the commercial fishery data (1°) and FE at 0.25° and 0.5° spatial scales was greater than 0.8. The AUC values each month based on the FE data at a 1° scale ranged from 0.775 to 0.829. The AUC values based on commercial fishing data at the 1° scale were comparable to the model results based on FE data at the 0.5° scale and inferior to the model results based on FE data at the 0.25° scales. Overall, the sea surface temperature (SST), temperature at 100 metres (T100), oxygen concentration at 100 metres (O100) and total primary production (PP) had the greatest influence on the distribution of the purse seine tuna fleet. The oxygen concentration at 200 metres (O200), distance to shore (DSH), dissolved oxygen (Dox), EKE, mixed layer depth (Mld), sea surface salinity (SSS), salinity at 100 metres (S100) and salinity at 200 metres (S200) had moderate influences, and other environmental variables had little influence. The suitable habitat areas varied in response to environmental conditions. The purse seine tuna fleet was mostly present at locations where the SST, T100, O100, O200 and PP were 28–30 °C, 27–29 °C, 150–200 mmol/m3 and 5–10 mg/m−3, respectively. The MaxEnt models enable the integration of AIS data and high-resolution environmental data from satellite remote sensing to describe the spatiotemporal distribution of the tuna purse seine fishery and the influence of environmental variables on the distribution, and can provide forecasts for fishing ground distributions based on future remote sensing environmental data.

An ensemble modelling approach for spatiotemporally explicit estimation of fish distributions using data assimilation

This article presents a novel method for estimating large scale spatiotemporal distribution patterns of fish populations modelled at the individual level. A single realization of an individual-based model calibrated on historic data has weak predictive capacity, given the underlying uncertainties faced when modelling a relatively small cluster of individuals operating in a high dimensional spatial plane. By incorporating real-time data sources to update these models, we can improve their predictive capacity. When correcting estimates from a large population of individuals, we don’t have access to information about individual histories, such as information derived from tagging data. We propose mapping individuals to derived density matrices, which can be corrected using conventional data sources which describe a mass of individuals e.g. catch data. An ensemble of derived states are used as forecast inputs to an assimilation procedure, that calculates an analysis state matrix of the same form. An individuals’ position and biomass values are updated based on the analysis values. To assess the effect of corrections, we setup a simulation experiment to explore the impact the number of measurement points has on the updated spatiotemporal distribution. The measurement points were sampled from derived states of a twin model that resembles the original model. The output of the twin model serves as the true distribution. With an increasing number of measurement points the centre of mass of the modelled distribution converges on the true distribution and the two distributions increase in overlap. Additionally, the absolute error between model and true values decreases. This estimation method, applied to individual-based models and coupled with real-time fisheries data, can improve spatially explicit estimates of fish distributions.

Application of the machine learning method to estimate the biomass of pacific cod in the North Kuril zone

The biomass of pacific cod (Gadus macrocephalus) in the North Kuril fishing zone is estimated using a multifactorial approach, with evaluation of uncertainty. For this purpose, the density of fish over entire zone is restored using the data on density obtained in 2022 compared with the data of previous surveys and fishery data obtained in 2021 and earlier, converted to the same scale, with application of the machine learning method, as the random forest in the multiple imputation by chained equations procedure (MICE). The coefficient of the restored data determination with out-of-bag (test set) data was > 0.8 with the data of scientific survey in 2021 and > 0.5 with the data of Danish seine observations. The cod density variance in MICE data was in 82 % lower than in the data of the scientific survey; therefore the biomass estimation with MICE data has lower uncertainty than that one calculated just from the mean density in survey. The study showed insignificant difference of the cod biomass in 2021 and 2022. Spatial segregation is revealed for fishing gears used for the pacific cod fishery. There is proposed to extend the list of fishing gears and to expand the study area for reducing possible bias in the biomass estimation due to large area of extrapolation.

ОЦЕНКА СОСТОЯНИЯ ЗАПАСОВ МОРСКИХ ВИДОВ РЫБ ЧЕРНОГО МОРЯ (ВОДЫ РОССИИ) В 2021 Г

Based on the available biological and fisheries data, stock status review for 18 units of the fish species inhabiting the Black Sea and the both Azov and Black Seas is presented. A modified version of the traditional approach to the harvest control rules for the aquatic bioresources of the Azov and Black Sea Fishery Basin is described for the case when they are assessed by the mathematical methods to estimate the current stock biomass and fishing mortality. For 11 stock units, analytical modeling including cohort, production and trend models has been applied. Based on the estimates of biomass and fishing mortality concerning biological reference points, in 2021, the status of six stock units of the marine fish species inhabiting the basin and exploited by the Russian fisheries was identified as increasing or stable (“Black Sea” stock units of the European sprat and European anchovy, “Crimean” stock unit of turbot, “Crimean and Caucasian” stock unit of red mullet, and “Black and Azov Seas” stock units of garfish and rays). Five fishery stock units (“Crimean and Caucasian” of mullets, picarel and Mediterranean horse mackerel, “Black and Azov Seas” of sand smelts, and “Caucasian” of turbot) have shown a decreasing trend in terms of abundance, and for the rest of the investigated fish stock units (“Mediterranean migrant” bluefish, Atlantic bonito and Atlantic mackerel, “Black Sea” whiting, so-iuy mullet and the other marine fish species, “Black and Azov Seas” spiny dogfish), the status has not been determined due to the absence of systematic biological and fishery data.