BUSCADOR RECOLECTA

14 pages, 6 figures, 4 tables.-- This is an open access article under the terms of the Creative Commons Attribution License, Harvest mortality typically truncates the harvested species' size structure, thereby reducing phenotypic complexity, which can lead to reduced population productivity, increased population variability, and selection on an array of life history traits that can further alter these demographic processes. Marine protected areas (MPAs) are a potential tool to protectolder, larger individuals and therefore mitigate such ecological and evolutionary effects of harvest, depending on the degree of connectivity among areas. Such MPA protection relies on a shift in size-dependent mortality, the measurement of which can therefore serve as an early indicator of whether MPAs might achieve the desired longer-term ecological and evolutionary responses. We directly measured MPA effects on size-selective mortality and associated size structure using mark–recapture data on European lobster (Homarus gammarus) collected at three MPA–control area pairs in southern Norway during one decade (n = 5,943). Mark–recapture modeling, accounting for variation in recapture probabilities, revealed (1) that annual mean survival was higher inside MPAs (0.592) vs. control areas (0.298) and (2) that significant negative relationships between survival and body size occurred at the control areas but not the MPAs, where the effect of body size was predominantly positive. Additionally, we found (3) that mean and maximum body size increased over time inside MPAs but not in control areas. Overall, our results suggest that MPAs can rebuild phenotypic complexity (i.e., size structure) and provide protection from harvest selection, Tagging of lobsters and fieldwork was supported by the Institute of Marine Research through long term funding for MPA monitoring in Skagerrak. Manuscript preparation was funded by the Research Council of Norway (RCN), project 201917 (PROMAR) and 294926 (CODSIZE), and by MINECO (Spanish Government) through a Juan de la Cierva Grant (ref. FJCI-2014-22482) to A. Fernandez-Chacon. Collaboration between authors from University of Agder and UC Berkeley was made possible through a grant from Peder Sather Center for Advanced Study at UC Berkeley. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 793627 (BEMAR), Peer reviewed

13 pages, 8 figures, 1 table.-- This is an open access article under the terms of the Creative Commons Attribution License, Acoustic telemetry has become a popular means of obtaining individual behavioural data from a wide array of species in marine and freshwater systems. Fate information is crucial to understand important aspects of population dynamics such as mortality, predation or dispersal rates.
Here we present a method to infer individual fate from acoustic telemetry arrays of receivers with overlapping detection ranges. Our method depends exclusively on information on animal movements and the characteristics and configuration of the telemetry equipment. By answering a limited number of simple questions, our method identifies six different fates: tagging mortality, natural mortality, fishing
mortality, predation, dispersal and survival.
Applying the method to a cod telemetry dataset, we were able to determine the fate of 97% of the individuals. We validate the results using several external sources of information, such as recaptures from fishers and control fish with known fate.
The method is readily applicable to a wide array of species with minimal adjustments, expanding the range of hypotheses that can be tested using telemetry data, H2020 Marie Skłodowska-Curie Actions, Grant/Award Number: 793627; Norges Forskningsråd, Grant/Award Number: 201917, 294926., Peer reviewed

11 pages, 6 figures, 1 table.-- Under a Creative Commons license, The effectiveness of Marine Protected Areas (MPAs) depends on the mobility of the populations that are the target of protection, with sedentary species likely to spend more time under protection even within small MPAs. However, little is understood about how individual variation in mobility may influence the risk of crossing an MPA border, as well as the fitness costs associated with being exposed to spillover fisheries. Here we investigated the repeatability of spatial behaviour, its role in determining the probability of being at risk (i.e. exposed to the fishery) and the fitness consequences for the individuals. We acoustically tracked the movements and fate of 282 individuals of three fish species during 8 years in a southern Norwegian fjord. We found that for individuals with a home range centroid inside the MPA, the probability of being at risk outside the MPA increased rapidly with reduced distance from the home range centroid to MPA borders, particularly for individuals having larger and more dispersed home ranges. We also detected that the seasonal expansions of the home range are associated with increased time at risk. Last, we show that individuals spending more time at risk were also more likely to be harvested by the fishery operating outside the MPA. Our study provides clear links between individual fish behaviour, fisheries-induced selection, and the effectiveness of protected areas. These links highlight the importance of intraspecific trait variation for understanding the spatial dynamics of populations and emphasize the need to consider individual behaviour when designing and implementing MPAs, This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 793627 (BEMAR), from the programme IF_ERC from the Spanish National Research Council (granted to DVR) and from the Marine Science programme within the Research Council of Norway, grant no. 294926 (CODSIZE). JC received funding from the BiodivERsA program (METRODIVER project), Peer reviewed

This article reviews a suite of studies conducted in a network of coastal Marine Protected Areas (MPAs) in Skagerrak, Southeast Norway. In 2006, Norway’s first lobster reserves were implemented, with the aim of protecting European lobster (Homarus gammarus) through a ban on fixed gear. A before–after control-impact paired series (BACIPS) monitoring program was initiated to evaluate effects of protection on depleted lobster populations. Experimental trapping and capture-recapture techniques were combined to track demography of populations, also including movement of individuals within and beyond MPAs and adjacent control areas. Further, population genetics and parentage studies were applied, allowing for estimation of gene flow, and novel work on sexual selection in lobsters. Additional studies have evaluated MPA effects on coastal cod (Gadus morhua), and on commercially harvested labrids (Ctenolabrus rupestris and Symphodus melops) and anadromous brown trout (Salmo trutta). Together, these studies reported effects of protection pertaining to increased population density, survival, body size and phenotypic diversity, changes in emigration and interaction with surrounding fisheries, and alteration of selection pressure on morphological- and behavioral traits. Designation of MPAs in close collaboration with fishers and managers, long-term monitoring, inclusion of citizen science and evolving research protocols—also including fisheries data—have revealed novel effects of protection and harvesting on marine populations, thus providing substantial contributions to conservation science. Moreover, knowledge of MPA effects on coastal species has impacted harvest regulations showing the utility of MPAs as empirically documented management tools in Norway., Preparation of the manuscript was supported by the University of Agder through a priority research grant awarded to the Centre of Coastal Research (CCR). EO received funding from the Marine Science Program within the Research Council of Norway, grant no. 294926 (CODSIZE). DV-R received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 793627 (BEMAR) and from the programme IF_ERC from the Spanish National Research Council., Peer reviewed

Individual acoustic tracking is a valuable tool to understand the behavioral ecology of aquatic species and to inform conservation actions. In this study, we examined the spatial behavior of single individuals of four common coastal fish species (striped red mullet, Mullus surmuletus;corkwing wrasse, Symphodus melops;pollack Pollachius pollachius;and white seabream, Diplodus sargus) in the National Park “Illas Atlánticas de Galicia” (NW Spain). The use of space of these species varied between 237,975 m2 and 48,725 m2, and the number of days that each fish was detected in the study area ranged between 35 and 110 days with weighted residence index ranged between 0.02 and 0.43. Pollackleft the array after 235 days, and was recaptured 342 days after tagging ~10 km south from the study area. The movement of the studied species followed contrasting diel patterns. While white seabream and striped red mullet moved over larger areas during the day, pollackranged over larger areas during the night. This single individual study (‘Solo datasets’) represents a useful baseline for future research projects by providing preliminary knowledge of these poorly known species in the study area., This project was supported by the project TAC (project ID 194834) funded by the programme Pleamar 2018 (BDC code CF18-01; Fundación Biodiversidad, co-financed by FEMP funds with the collaboration of the Ministerio para la Transición Ecológica y el Reto Demográfico) and by the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 793627 (BEMAR). K. Leeb was supported by a ‘Junta para la Ampliación de Estudios Intro ICU’ fellowship from the CSIC, at the IIM-CSIC, and the European Union’s Erasmus+ programme.

Knowledge of the spatial behaviour of aquatic living resources is essential to assess their vulnerability to environmental and anthropogenic stressors and inform efficient management strategies. Elasmobranchs are particularly vulnerable to exploitation. Within this group of fish, the implementation of species-specific conservation actions has been challenging due to insufficient information on their biology and ecology.
In this study, acoustic telemetry was used to investigate the seasonal variation, diel patterns, and biological and sea temperature effects on the spatial behaviour of the endangered undulate skate, Raja undulata, within a marine protected area in north-west Spain.
Movement and behaviour were mainly driven by diel and seasonal patterns. The presence of the tagged skates in the study area peaked during summer. Space use was highest in late spring and activity was lowest during summer. Skates used more space and were more active during night-time as compared to daytime, when they stayed in sandy bottoms. Sea temperature had a negligible positive effect on activity.
Our work represents an important contribution to the understanding of the ecology of this endangered, yet commercially important skate in Europe, and provides important insights for the implementation of spatial and temporal restrictions aimed at reducing mortality and bycatch of this species, This study was funded by the TAC project with the collaboration of the Fundación Biodiversidad, from the Ministerio para la Transición Ecológica y el Reto Demográfico (Spanish Government), through the Pleamar programe, cofounded by the FEMP. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 793627 (BEMAR)., Peer reviewed

4 pages, 2 figures, 1 table, [EN] The ballan wrasse, Labrus bergylta Ascanius, 1767, is the largest wrasse inhabiting European waters and has two different body colour morphotypes: plain and spotted. A large spotted specimen was caught by a spear-fisher in the Galician Atlantic coast (North West Spain). The total length was 66 cm and the total weight was 5,065 g in fresh, but 65 cm and 4,920 g after being frost and thawed, when the specimen was analysed. It represents a new maximum length and weight for the species. Age determination based on sectioned otoliths was 24 years, which is the maximum age for a spotted morphotypes of the species, [FR] La vieille commune, Labrus bergylta Ascanius, 1767, est la plus grande vieille vivant dans les eaux européennes et possède deux morphotypes de couleur de corps différents: uni et tacheté. Un gros spécimen tacheté a été capturé par un chasseur sous-marin sur la côte atlantique de la Galice (au nord-ouest de l’Espagne). La longueur totale était de 66 cm et le poids total était de 5065 g en poids frais, mais 65 cm et 4920 g après congélation et décongélation, lorsque l’échantillon a été analysé. Ce spécimen représente un nouveau record de longueur et de poids maximum pour l’espèce. L’âge déterminé par des otolithes sectionnés était de 24 ans, ce qui représente l’âge maximum pour un individu tacheté de l’espèce, This project received funding from the european Union’s Horizon 2020 research and innovation programme under the Marie sklodowska-Curie grant agreement no. 793627 (BeMaR) and from the programme iF_eRC from the spanish national Research Council, Peer reviewed

8 pages, 4 figures, 1 table.-- This article is licensed under a Creative Commons Attribution 4.0 International License, Despite our critical dependence on aquatic wildlife, we lack a complete understanding of the drivers of population stability and structure for most fish species. Social network analysis has been increasingly used to investigate animal societies as it explicitly links individual decision-making to population-level processes and demography. While the study of social structure is of great ecological interest, it is also potentially important for species of economic value or of conservation concern. To date however, there has been little focus on how social processes are likely to influence the conservation of fish populations. Here we identify applications for how a social network approach can help address broad fish conservation themes such as population structure, biological invasions or fisheries management. We discuss the burgeoning opportunities offered and challenges still faced by current technologies to integrate social network approaches within fish conservation, This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 793627 (BEMAR) and from the programme IF_ERC from the Spanish National Research Council. Funding for D. Jacoby was provided by Research England and the Bertarelli Foundation and contributed to the Bertarelli Programme in Marine Science, Peer reviewed

18 pages, 3 tables, 7 figures, Environmental variables are known to regulate the reproductive output of marine intertidal organisms, but typically these variables are studied as averages and interpreted at a macroscale level. Along 200 km of coast in NW Iberia, great variability in the reproductive activity of the stalked barnacle Pollicipes pollicipes was found among 7 different locations. We found the highest number of broods reported to date in this species and suggest a more realistic method of predicting reproductive success that takes into account sea surface temperature (SST). At these same locations, we studied 13 yr of SST, thermal upwelling index (UI), ground skin temperature and chlorophyll a (chl a) satellite data, using spectral analyses to partition their temporal variability over ecologically relevant time scales. SST played the most relevant role as an environmental driver, explaining 48% of the variability in the proportion of breeding individuals (BI), but the SST-BI goodness-of-fit decreased sharply northwards. Variance-partitioning analyses indicated that cycles between 20 and 100 d in SST and UI were more important southwards, which is consistent with a latitudinal gradient in upwelling intensity and frequency along this coast. Thus, we found better biophysical coupling towards the south, where shorter fluctuation time scales in SST match the gonadal development period (around 1 mo). This pattern may explain the spatial variability in the strength of association between key environmental variables and the reproductive cycle of coastal species along their distribution range, This research was funded by the BiodivERsA3 2015-2016, EU HORIZON 2020 ERA-NET COFUND and the Spanish Spanish Ministerio de Economía y Competitividad under project PERCEBES (PCIN-2016-063) and the Autonomous government Xunta de Galicia-FEDER (project ED431C-2017-46). During data processing and manuscript elaboration, S.R. was funded by a PhD fellowship from the Xunta de Galicia (ED481A-2020/199) and N.W. by NASA grant 80NSSC20K0074. C.M. was supported by a contract through project PCIN-2016-063. G.M. was supported by post-doctoral contracts from projects MARISCO (CTM2014-51935-R, Spanish Ministerio de Economía y Competitividad) and PERCEBES (PCIN-2016-063). A.A. was supported by a FPU fellowship (FPU2016-04258, Spanish Ministry of Science, Innovation and Universities). J.S., P.S., B.B. and R.O. were funded by the European Maritime and Fisheries Fund (EMFF) Operational Programme for Spain (2014-2020), and the Consellería do Mar. D.V.-R. was funded by the Marie Sklodowska-Curie grant agreement No. 793627 (BEMAR, EU Horizon 2020 research and innovation programme), Peer reviewed

6 pages, 1 table, 6 figures, Discard reduction is a cornerstone of the European Common Fisheries Policy. The discard ban policy, which aims to reduce fisheries discards, is particularly challenging for small-scale fisheries. Demonstrating high survival rates of discarded individuals may provide flexibility to the application of the discard ban through the so-called survival exemption. Here we used acoustic telemetry and mark-recapture data to estimate discard survival of coastal elasmobranch species at multiple temporal scales. We focused on four species targeted by the small-scale fishery in Galicia (NW Spain), one of the most important fishing regions in Europe: Scyliorhinus canicula, Raja undulata, Raja clavata and Raja brachyura. The overall survival rate was 90% on the short term and 85.7% on the long term, but it varied among species. Survival rates of R. clavata and S. canicula on the short term were 70% and 100%, respectively, and 66.7% and 92.9% on the long term, respectively. All the individuals of R. brachyura and R. undulata survived on the long term. Our results are critical to support the application of survival exemption in small scale fisheries, This study was funded by the DESTAC project with the collaboration of the Fundación Biodiversidad, from the Ministerio para la Transición Ecológica y el Reto Demográfico (Spanish Government), through the pleamar programme (2019), cofounded by the Fondo Europeo Marítimo y de Pesca (FEMP). This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 793627 (BEMAR) and from the programme IF_ERC from the Spanish National Research Council (CSIC) granted to David Villegas-Ríos, Peer reviewed

24 pages, 6 figures.-- This is an open access article under the terms of the Creative Commons Attribution License, The ocean is a key component of the Earth's dynamics, providing a great variety of ecosystem services to humans. Yet, human activities are globally changing its structure and major components, including marine biodiversity. In this context, the United Nations has proclaimed a Decade of Ocean Science for Sustainable Development to tackle the scientific challenges necessary for a sustainable use of the ocean by means of the Sustainable Development Goal 14 (SDG14). Here, we review how Acoustic animal Tracking, a widely distributed methodology of tracking marine biodiversity with electronic devices, can provide a roadmap for implementing the major Actions to achieve the SDG14. We show that acoustic tracking can be used to reduce and monitor the effects of marine pollution including noise, light, and plastic pollution. Acoustic tracking can be effectively used to monitor the responses of marine biodiversity to human-made infrastructures and habitat restoration, as well as to determine the effects of hypoxia, ocean warming, and acidification. Acoustic tracking has been historically used to inform fisheries management, the design of marine protected areas, and the detection of essential habitats, rendering this technique particularly attractive to achieve the sustainable fishing and spatial protection target goals of the SDG14. Finally, acoustic tracking can contribute to end illegal, unreported, and unregulated fishing by providing tools to monitor marine biodiversity against poachers and promote the development of Small Islands Developing States and developing countries. To fully benefit from acoustic tracking supporting the SDG14 Targets, trans-boundary collaborative efforts through tracking networks are required to promote ocean information sharing and ocean literacy. We therefore propose acoustic tracking and tracking networks as relevant contributors to tackle the scientific challenges that are necessary for a sustainable use of the ocean promoted by the United Nations, Agencia Estatal Investigación, España, Grant/Award Number: PID2019-104940GA-I00; Consejo Superior de Investigaciones Científicas, Grant/Award Number: PIE202030E002; Fundação para a Ciência e a Tecnologia, Grant/Award Number: DL57/2016/CP1361/CT0036, BECORV PTDC/BIABMA/30278 and UID/Multi/04326/2020; European Regional Development Fund: Interreg, MarGen II Project, Grant/Award Number: 175806; H2020 Marie Sklodowska-Curie Actions, Grant/Award Number: 793627 and 891404; Juan de la Cierva, Ministerio Ciencia e Innovación, España, Grant/Award Number: IJC2019-038852-I; Norwegian Research Council, Grant/Award Number: LOST; European Cooperation in Science and Technology, Grant/Award Number: CA18102 COST, Peer reviewed

[Methods] There are three types of data:

- Detection data: 1-3 files per fish

- Fish information data: includes all the relevant information for each individual, e.g. when it was tagged, transmitter type, etc...

- Receiver array information: includes the location of the receivers

[Usage Notes] Metadata of the dataset:

Villegas Ríos, David et al. (2021), Inferring individual fate from aquatic acoustic telemetry data, Dryad, Dataset, https://doi.org/10.5061/dryad.2bvq83bn0



Detections data (all files starting with 9002 or 9004):

Date and time: date and time of detection
Receiver: name of the receiver
Transmitter: ID of the transmitter
Transmitter name: empty
Transmitter serial: serial number of the transmitter
Sensor value: depth measure
Sensor units: units of the depth measure (meters)
Station name: name of the station where the receiver is places
Latitude: latitude of the station
Longitude: longitude of the station

fishinformation.csv: all the columns are self-explained except the following:

MinDelaySec: minimum delay of the transmitter, in seconds.
MaxDelaySec: maximum delay of the transmitter, in seconds.
Release_lat_geo: release latitude, in geographic coordinates.
Release_lon_geo: release longitude, in geographic coordinates.

array_information.csv: all the columns are self-explained except the following:

deploymentdatetime_timestamp: date of deployment of any particular receiver.
recoverydatetime_timestamp: date of recovery of any particular receiver.
lat_geo: latitude of the receiver location, in geographic coordinates.
lon_geo: longitude of the receiver location, in geographic coordinates.
lat_utm: latitude of the receiver location, in UTM.
lon_utm: longitude of the receiver location, in UTM, Acoustic telemetry has become a popular means of obtaining individual behavioural data from a wide array of species in marine and freshwater systems. Fate information is crucial to understand important aspects of population dynamics such as mortality, predation or dispersal rates. Here we present a method to infer individual fate from acoustic telemetry arrays of receivers with overlapping detection ranges. Our method depends exclusively on information on animal movements and the characteristics and configuration of the telemetry equipment. By answering a limited number of simple questions, our method identifies six different fates: tagging mortality, natural mortality, fishing mortality, predation, dispersal and survival. Applying the method to a cod telemetry dataset, we were able to determine fate for 97% of the individuals. We validate the results using several external sources of information, such as recaptures from fishers and control fish with known fate. The method is readily applicable to a wide array of species with minimal adjustments, expanding the range of hypotheses that can be tested using telemetry data., H2020 Marie Skłodowska-Curie Actions, Award: 793627., Peer reviewed

Marine protected areas (MPAs), and specially no-take areas (NTAs), play an important role in protecting target populations from fisheries. When developing spatial conservation and management tools, the design has mainly focused on population-level measures of fish home ranges, spawning and feeding areas, and migration routes. Intraspecific differences in fish behaviour, however, are often not accounted for, even though they could influence the level of realized protection. In this study, we investigated the intraspecific variation in spatial behaviour of a harvested fish, Diplodus sargus, and how it impacts the degree of protection granted by a NTA in the south of Portugal. We identified four behavioural types according to their spatial behaviour: residents, commuters, seasonal visitors, and single users. Time at risk (i.e. outside the NTA) greatly varied among the four groups, but also over the year for the seasonal and the single users. Our study shows how acoustic telemetry can assist spatial conservation and fisheries management and provides novel insight regarding the role of individual variation in behaviour to understand protection granted by MPAs to harvested species. It also suggests that incorporating such information into all stages of MPA design and implementation can result in increased resilience of the protected populations., This study received funding from POSEUR through the MARSW project (POSEUR-03-2215-FC-000046). The beneficiary of the MARSW project was the Liga para a Proteção da Natureza (LPN), and cofounders were the Municipalities of Aljezur, Vila do Bispo, and Odemira, and the Fundo Ambiental. This study also received funding from the Portuguese FCT—Foundation for Science and Technology to CCMAR through the strategic projects UIDB/04326/2020, UIDP/04326/2020 and LA/P/0101/2020. B.H.C. was supported by national funds through FCT—Foundation for Science and Technology, I.P. (Portugal), in agreement with the University of Algarve, in the scope of Norma Transitória with the research contract DL57/2016/CP1361/CT0038. D.V.R. has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 793627 (BEMAR) and from the programme IF_ERC from the Spanish National Research Council. C.B.A. and M.P. were supported by an Erasmus+ EU fund (VLUHR)., Peer reviewed

15 pages, 6 figures, 1 table.-- This is an open access article under the terms of the Creative Commons Attribution License, Shark populations have suffered dramatic declines across the world as a result of overfishing.
Marine protected areas (MPAs) can help restore overfished populations; however, their effectiveness largely relies on understanding the ecology of the targeted species.
This study investigated the spatial ecology of the intensely harvested but understudied small spotted catshark (Scyliorhinus canicula) through acoustic telemetry in the Cíes Islands, a small MPA in the north-west of the Iberian Peninsula.
There were significant effects of diel, seasonal cycles, biotic (sex and total length) and abiotic (bottom sea temperature) variables on the spatial behaviour of S. canicula. The mean residency index was low (0.27) and movement patterns suggested a strong connection with inshore waters. While the probability of presence in the study area was mainly driven by sex (i.e. greater for females), a drastic increase in activity was observed at night (compared with daytime hours). The activity space decreased with larger body sizes. Warmer waters were related to higher activity levels and larger activity spaces.
This study provides essential knowledge of the spatial behaviour of S. canicula, with significant implications for the conservation and management of this species. The results indicate that small MPAs may fail to protect the whole range of movements of S. canicula, but suggest a larger protection potential for females.
To be effective for S. canicula conservation, MPAs should be appropriately sized and designed for the ranging behaviour of the target species in order to provide total protection. Temporal restrictions on fishing at night mirroring the peak activity pattern of S. canicula could be implemented to limit the probability of its capture, K. Papadopoulo was supported by the European Union's Erasmus+ programme. This study was funded by the projects DESTAC and IGENTAC with the collaboration of the Fundación Biodiversidad, from the Ministerio para la Transición Ecológica y el Reto Demográfico (Spanish Government), through the Pleamar programme, cofounded by the FEMP. The acoustic telemetry array was supported by the ATLAZUL project (0755_ATLAZUL_6_E) co-funded by the European Regional Development Fund (ERDF) through the Interreg V-A Spain-Portugal Program (POCTEP) 2014-2020. DVR has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 793627 (BEMAR) and from the programme IF_ERC from the Spanish National Research Council, Peer reviewed

4 files, 1. Understanding the responses of aquatic animals to temperature variability is essential to predict impacts of future climate change and to inform conservation and management. Most ectotherms such as fish are expected to adjust their behaviour to avoid extreme temperatures and minimize acute changes in body temperature. In coastal Skagerrak, Norway, sea surface temperature (SST) ranges seasonally from 0 to over 20 °C, representing a challenge to the fish community which includes both cold-, cool- and warm-water affinity species.

2. By acoustically tracking 111 individuals of Atlantic cod (Gadus morhua), pollack (Pollachius pollachius) and ballan wrasse (Labrus bergylta) in 2015 - 2018, we examined how coexisting species within a fish community adjusted their behaviour (i.e. vertical distribution in the water column and habitat selection) to cope with the thermal variation.

3. Mixed-effect models showed that thermal preference was a main driver of behaviour and habitat use of the fish community in a southern Norwegian fjord. Cod used colder waters, compared with pollack and ballan wrasse. Increases in SST during summer were associated with the use of deeper, colder waters by cod, especially by larger individuals, and conversely with the occupancy of shallower areas by pollack and ballan wrasse. During winter, when SST dropped and the thermal stratification reversed, pollack and ballan wrasse moved to deeper, relatively warmer areas, while cod selected shallower, colder habitats. Though habitat selection was affected by temperature, species-specific habitat selection was observed even when temperature was similar throughout habitats.

4. This study shows how cohabiting fish species respond to thermal heterogeneity, suggesting that i) temperature regulates the access to the different depths and habitats and ii) behavioural plasticity may be an important factor for coping with temperature variability and potentially for adaptation to climate change, The Research Council of Norway, Award: 294926; European Union’s Horizon 2020, Award: 793627; Regionale forskningsfond Oslofjordfondet, Award: 272090, Peer reviewed