Capelin distribution in winter 2004-2017: spatiotemporal correlation between density estimates from different sampling methods

The winter distribution of Barents Sea capelin is highly dynamic in space and time, as this is the time of year when mature individuals separate from the immatures and start their spawning migration to the Norwegian and Russian coasts. Due to the difficulty of sampling the entire distribution at this time of year, the stock assessment of capelin is based on data from the ecosystem survey in autumn when capelin has a more favourable distribution for acoustic abundance estimation. A stock projection model is then used to predict how much of the stock will be left and available for the fishery the coming winter. It has long been discussed if a winter survey could be used to improve accuracy of the stock prediction by estimating the maturing part of the stock just before the fishery starts. Estimations based on experimental winter surveys for capelin have so far not been able to achieve this goal. To improve on future attempts, more information on capelin distribution in winter is needed. Here we explore data on capelin distribution collected during the winter survey of the Barents Sea in 2004-2017, a survey primarily collecting data on cod and haddock. Using data from acoustics, demersal trawls, and cod stomachs, we study changes in capelin distribution patterns and correlations between densities from the different data sources during the January-March survey period, with the overarching aim of evaluating the reliability of data sources for capelin investigations. All sampling methods except acoustics showed that capelin shifted toward the south from January-March, and the correlations between capelin densities from different sampling methods varied substantially, reflecting this migration. We found support for the hypothesis that capelin may migrate in the acoustic dead zones, in particularly in the bottom zone, as they move closer to the coast. The discrepancy between sampling methods and variability in the data increased later in the period when capelin shifted south. We recommend further analysis on the vertical distribution of capelin to examine the possibility of combining demersal trawl and acoustic data for abundance estimation of maturing capelin.publishedVersio

Abundance indices for norwegian coastal cod north of 62°N

In connection with the benchmark processes within ICES on Norwegian Coastal Cod north of 62°N during autumn 2020-spring 2021, new abundance index series based on bottom trawl stations and acoustics at the autumn coastal survey were made. The acoustic index covers the period 1995-2019 while the trawl index covers the period 2003-2019. This report describes the methods used and briefly presents the results.publishedVersio

Survey report from the CODFUN 2016114 Barents Sea survey 5.-11. oktober 2016

The survey is part of the project “The cod – capelin interaction in the Barents Sea: spatial dynamics in predator prey overlap and functional response (CODFUN)” funded by the Norwegian Research Council (NRC project number 243676/E40). The CODFUN project was motivated by the need to update and improve the current formulation of the functional response of cod used in the capelin assessment model. The functional response is the relationship between the feeding rate of individual predators and density of prey. Functional response, together with density of predators and prey is used to calculate natural mortality. In all natural environments, there is spatial heterogeneity in densities of prey and predators and their overlap. This heterogeneity becomes a very important determinant of natural mortality due to predation. The aim of the CODFUN project is to quantify and explain spatial heterogeneity in the capelin-cod interaction at different spatial scales in the Barents Sea. The aim of the survey was to study spatial variation at the scale of individual cod and capelin schools. We aimed at quantifying attack rates of cod on capelin using acoustics, and to estimate proportion of successful attacks using stomach samples from trawl catches and handline. Furthermore, we aimed to relate variation in attack rates to variation in capelin densities and light conditionspublishedVersio

Predator–prey overlap in three dimensions: cod benefit from capelin coming near the seafloor

Spatial overlap between predator and prey is a prerequisite for predation, but the degree of overlap is not necessarily proportional to prey consumption. This is because many of the behavioural processes that precede ingestion are non-linear and depend on local prey densities. In aquatic environments, predators and prey distribute not only across a surface, but also vertically in the water column, adding another dimension to the interaction. Integrating and simplifying behavioural processes across space and time can lead to systematic biases in our inference about interaction strength. To recognise situations when this may occur, we must first understand processes underlying variation in prey consumption by individuals. Here we analysed the diet of a major predator in the Barents Sea, the Atlantic cod Gadus morhua, aiming to understand drivers of variation in cod's feeding on its main prey capelin Mallotus villosus. Cod and capelin only partly share habitats, as cod mainly reside near the seafloor and capelin inhabit the free water masses. We used data on stomach contents from ~2000 cod individuals and their surrounding environment collected over 12 years, testing hypotheses on biological and physical drivers of variation in cod's consumption of capelin, using generalized additive models. Specifically, effects of capelin abundance, capelin depth distribution, bottom depth and cod abundance on capelin consumption were evaluated at a resolution scale of 2 km. We found no indication of food competition as cod abundance had no effect on capelin consumption. Capelin abundance had small effects on consumption, while capelin depth distribution was important. Cod fed more intensively on capelin when capelin came close to the seafloor, especially at shallow banks and bank edges. Spatial overlap as an indicator for interaction strength needs to be evaluated in three dimensions instead of the conventional two when species are partly separated in the water column.publishedVersio

Fish investigations in the Barents Sea winter 2020

This report presents the main results from the surveys in January-March 2020. The surveys were performed with the Norwegian research vessels “Helmer Hanssen” and “Johan Hjort” and the Russian research vessel “Vilnyus”. Annual survey reports since 1981 are listed in Appendix 1, and names of scientific participants are given in Appendix 3.publishedVersio

Advice on fishing opportunities for Northeast Arctic cod in 2023 in ICES subareas 1 and 2

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Report of the Joint Russian-Norwegian Working Group on Arctic Fisheries (JRN-AFWG) 2022

On 30 th March 2022 all Russian participation in ICES was temporally suspended. Although the announcement of the suspension stressed the role of ICES as a “multilateral science organization”, this suspension applied not only to research activities, but also to the ICES work providing fisheries advice for the sustainable management of fish stocks and ecosystems. As a result of the suspension, the ICES AFWG provided advice only for saithe, coastal cod north, coastal cod south, and golden redfish ( Sebastes norvegicus ). Northeast Arctic (NEA) cod, haddock and beaked redfish ( Sebastes mentella ) assessments have been conducted outside of ICES in a newly constituted Joint Russian-Norwegian Working Group on Arctic Fisheries (JRN-AFWG). Although this work has been conducted independently of ICES, the methodologies agreed at ICES benchmarks and agreed HCRs (Harvest Control Rules) have been followed in providing this advice.publishedVersio

Advice on fishing opportunities for beaked redfish in 2023 and 2024 in ICES subareas 1 and 2

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Advice on fishing opportunities for Northeast Arctic haddock in 2023 in ICES subareas 1 and 2

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Fish investigations in the Barents Sea Winter 2022

Annual catch quotas and other regulations of the Barents Sea fisheries are set through negotiations between Norway and Russia. Assessment of the state of the stocks and quota advice are based on survey results and international landings statistics. The results from the demersal fish winter surveys in the Barents Sea are an important source of information for the annual stock assessment.Fish investigations in the Barents Sea Winter 2022publishedVersio