Combining multiple data sets to unravel the spatiotemporal dynamics of a data-limited fish stock

Publisher's version (útgefin grein)The biological status of many commercially exploited fishes remains unknown, mostly due to a lack of data necessary for their assessment. Investigating the spatiotemporal dynamics of such species can lead to new insights into population processes and foster a path towards improved spatial management decisions. Here, we focused on striped red mullet (Mullus surmuletus), a widespread yet data-limited species of high commercial importance. Aiming to quantify range dynamics in this data-poor scenario, we combined fishery-dependent and -independent data sets through a series of Bayesian mixed-effects models designed to capture monthly and seasonal occurrence patterns near the species’ northern range limit across 20 years. Combining multiple data sets allowed us to cover the entire distribution of the northern population of M. surmuletus, exploring dynamics at different spatiotemporal scales and identifying key environmental drivers (i.e., sea surface temperature, salinity) that shape occurrence patterns. Our results demonstrate that even when process and (or) observation uncertainty is high, or when data are sparse, if we combine multiple data sets within a hierarchical modelling framework, accurate and useful spatial predictions can still be made.CP’s postdoc was funded by Ifremer and France Filière Peche. The authors thank Bruno Ernande for suggestions and comments that improved the work during the analysis. The authors also thank two anonymous reviewers for their comments, which helped to improve the manuscript.Peer Reviewe

Combined fishing and climate forcing in the southern Benguela upwelling ecosystem: an end-to-end modelling approach reveals dampened effects

The effects of climate and fishing on marine ecosystems have usually been studied separately, but their interactions make ecosystem dynamics difficult to understand and predict. Of particular interest to management, the potential synergism or antagonism between fishing pressure and climate forcing is analysed in this paper, using an end-to-end ecosystem model of the southern Benguela ecosystem, built from coupling hydrodynamic, biogeochemical and multispecies fish models (ROMS-N 2 P 2 Z 2 D 2 -OSMOSE). Scenarios of different intensities of upwelling-favourable wind stress combined with scenarios of fishing top-predator fish were tested. Analyses of isolated drivers show that the bottom-up effect of the climate forcing propagates up the food chain whereas the top-down effect of fishing cascades down to zooplankton in unfavourable environmental conditions but dampens before it reaches phytoplankton. When considering both climate and fishing drivers together, it appears that top-down control dominates the link between top-predator fish and forage fish, whereas interactions between the lower trophic levels are dominated by bottom-up control. The forage fish functional group appears to be a central component of this ecosystem, being the meeting point of two opposite trophic controls. The set of combined scenarios shows that fishing pressure and upwelling-favourable wind stress have mostly dampened effects on fish populations, compared to predictions from the separate effects of the stressors. Dampened effects result in biomass accumulation at the top predator fish level but a depletion of biomass at the forage fish level. This should draw our attention to the evolution of this functional group, which appears as both structurally important in the trophic functioning of the ecosystem, and very sensitive to climate and fishing pressures. In particular, diagnoses considering fishing pressure only might be more optimistic than those that consider combined effects of fishing and environmental variability

Editorial: Managing for the future: challenges and approaches for disentangling the relative roles of environmental change and fishing in marine ecosystems

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Trophic level-based indicators to track fishing impacts across marine ecosystems

Trophic level (TL)-based indicators have been widely used to examine fishing impacts in aquatic ecosystems and the induced biodiversity changes. However, much debate has ensued regarding discrepancies and challenges arising from the use of landings data from commercial fisheries to calculate TL indicators. Subsequent studies have started to examine survey-based and model-based indicators. In this paper, we undertake an extensive evaluation of a variety of TL indicators across 9 well-studied marine ecosystems by making use of model- as well as survey and catch-based TL indicators. Using detailed regional information and data on fishing history, fishing intensity, and environmental conditions, we evaluate how well TL indicators are capturing fishing effects at the community level of marine ecosystems. Our results highlight that the differences observed between TL indicator values and trends is dependent on the data source and the TL cut-off point used in the calculations and is not attributable to an intrinsic problem with TL based indicators. All 3 data sources provide useful information about the structural changes in the ecosystem as a result of fishing, but our results indicate that only model-based indicators represent fishing impacts at the whole ecosystem level.JRC.H.1-Water Resource

Workshop on the production of swept-area estimates for all hauls in DATRAS for biodiver-sity assessments (WKSAE-DATRAS)

The workshop on the production of swept-area estimates for all hauls in DATRAS for biodiver-sity assessments (WKSAE-DATRAS) considered three groups of surveys for which data are sub-mitted to the Database of Trawl Surveys (DATRAS): various Beam Trawl Surveys, the Northeast Atlantic International Bottom Trawl Survey (Northeast Atlantic IBTS), and the North Sea Inter-national Bottom Trawl Survey (North Sea IBTS). All countries contributing to the above-mentioned surveys were represented by at least one par-ticipant during the workshop, apart from the Netherlands and Norway. The main objectives of the workshop were to establish tow-by-tow swept-area estimates for time-series as far back in time as possible, compare different approaches for the estimates of missing observations, and harmonize the resulting dataseries for biodiversity assessments. For all of the surveys considered, problems with data quality were detected. This included the Beam Trawl Surveys but was most pronounced for the North Sea IBTS. Outliers and potential erroneous data were listed for reporting back to the respective national institutes. In particular, missing observations or algorithms affected wing spread-based swept-area, which is needed in several applications. This workshop compared the Marine Scotland Science-MSS/OSPAR approach, which includes a data quality check for the information needed for the calculation of swept-area, and the DATRAS approach, which depends solely on correctly reported data from the national institutes. Larger data gaps were identified, in particular for several years of the North Sea IBTS. For those surveys, it is proposed that the best possible way forward at this moment is to use estimates based on the MSS/OSPAR approach. However, if dubious records (i.e. extreme outliers) were identified by the MSS/OSPAR and no other information was available, values (e.g. speed over ground or the depth at which a change from short to long sweeps should have happened) were taken from the manual. However, expe-rience has shown that the survey manuals are not followed in all instances, and so persistent country-specific and survey-specific deviations may occur. The national institutes are encouraged to check, correct, and fill in missing survey data through re-submissions to DATRAS. It is recommended that DATRAS data quality control on data sub-mission is extended for the information needed for the calculation of swept-area (e.g. distance, depth, door spread, and wing spread) and that this is done in close cooperation between the ICES Data Centre and the respective ICES survey working groups, WGBEAM (Working Group on Beam Trawl Surveys) and IBTSWG (International Bottom Trawl Survey Working Group).info:eu-repo/semantics/publishedVersio

Working group on ecosystem assessment of Western European shelf seas (WGEAWESS)

The ICES Working Group on Ecosystem Assessment of Western European Shelf Seas (WGEA-WESS) aims to provide high quality science in support to holistic, adaptive, evidence-based man-agement in the Celtic seas, Bay of Biscay and Iberian coast regions. The group works towards developing integrated ecosystem assessments for both the (i) Celtic Seas and (ii) Bay of Biscay and Iberian Coast which are summarized in the Ecosystem Overviews (EOs) advice products that were recently updated. Integrated Trend Analysis (ITA) were performed for multiple sub-ecoregions and used to develop an understanding of ecosystem responses to pressures at varying spatial scales. Ecosystem models (primarily Ecopath with Ecosim; EwE) were developed and identified for fisheries and spatial management advice. The updated Celtic Seas EO represents a large step forward for EOs, with the inclusion of novel sections on climate change, foodweb and productivity, the first application of the new guidelines for building the conceptual diagram, inclusion of socio-economic indicators, and progress made toward complying with the Transparent Assessment Framework (TAF). We highlight ongoing issues relevant to the development and communication of EO conceptual diagrams. A common methodology using dynamic factor analysis (DFA) was used to perform ITA in a comparable way for seven subregions. This was supported by the design and compilation of the first standardized cross-regional dataset. A comparison of the main trends evidenced among subregions over the period 1993–2020 was conducted and will be published soon. A list of available and developing EWE models for the region was also generated. Here, we re-port on the advances in temporal and spatial ecosystem modelling, such as their capacity to model the impacts of sector activities (e.g. renewables and fisheries) and quantify foodweb indi-cators. We also reflect on model quality assessment with the key run of the Irish sea EwE model. The group highlighted the hurdles and gaps in current models in support of EBM, such as the choice of a relevant functional, spatial, and temporal scales and the impacts of model structure on our capacity to draw comparisons from models of different regions. The group aims to ad-dress these issues in coming years and identify routes for ecosystem model derived information into ICES advice.info:eu-repo/semantics/publishedVersio

Evaluating changes in marine communities that provide ecosystem services through comparative assessments of community indicators

Fisheries provide critical provisioning services, especially given increasing human population. Understanding where marine communities are declining provides an indication of ecosystems of concern and highlights potential conflicts between seafood provisioning from wild fisheries and other ecosystem services. Here we use the nonparametric statistic, Kendall[U+05F3]s tau, to assess trends in biomass of exploited marine species across a range of ecosystems. The proportion of 'Non-Declining Exploited Species' (NDES) is compared among ecosystems and to three community-level indicators that provide a gauge of the ability of a marine ecosystem to function both in provisioning and as a regulating service: survey-based mean trophic level, proportion of predatory fish, and mean life span. In some ecosystems, NDES corresponds to states and temporal trajectories of the community indicators, indicating deteriorating conditions in both the exploited community and in the overall community. However differences illustrate the necessity of using multiple ecological indicators to reflect the state of the ecosystem. For each ecosystem, we discuss patterns in NDES with respect to the community-level indicators and present results in the context of ecosystem-specific drivers. We conclude that using NDES requires context-specific supporting information in order to provide guidance within a management framework.We would like to thank the IndiSeas Working Group, endorsed by IOC-UNESCO (www.ioc-unesco.org) and the European Network of Excellence Euroceans (www.eur-oceans.eu). KMK was supported by Conservation International and the Sea Around Us project, a collaboration between The University of British Columbia and The Pew Charitable Trusts. MC was partially supported by the EC Marie Curie CIG grant to BIOWEB and the Spanish Research Program Ramon y Cajal. LJS was supported through the South African Research Chair Initiative, funded through the South African Department of Science and Technology (DST) and administered by the South African National Research Foundation (NRF). YJS and MTT were supported by the French project EMIBIOS (FRB, contract no. APP-SCEN-2010-II). LJS and YS were also funded by the European collaborative project MEECE – Marine Ecosystem Evolution in a Changing Environment – (FP7, Contract no. 212085). CPL was supported by Defra project MF1228 (From Physics to Fisheries) and DEVOTES (DEVelopment of innovative Tools for understanding marine biodiversity and assessing good Environmental Status) funded by EU FP7 (grant Agreement no. 308392), www.devotes-project.eu. GIvdM was partially supported by the Norwegian Nature Index programme and the Institute of Marine Research, Norway. HO was funded was funded by the Estonian Ministry of Education and Research (grant SF0180005s10). MAT was funded by a predoctoral FPI fellowship from the Spanish Institute of Oceanography (IEO). MJJJ was supported by the EC Marie Curie IOF Grant, PIOF-GA-2013-628116. We acknowledge all those who conducted surveys to collect the data used in this study.Peer reviewe

Improving the interpretation of fishing effort and pressures in mixed fisheries using spatial overlap metrics

Managing mixed fisheries requires understanding fishers’ behaviour to allow predicting future fisheries distribution and impact on marine ecosystems. A new approach was developed to compare fine scale fishing effort distribution of Eastern English Channel (EEC) bottom trawlers, to the monthly- and spatially-resolved abundance distributions of commercial species. First, the added-value of using species-specific spatial overlap metric to quantify effective fishing effort and improve the relationship between fishing effort and fishing mortality was assessed. Second, based on the Ideal Free Distribution (IFD) theory, the species-specific weights given by fishers to different species were estimated by maximizing the overlap between target species assemblage and effort distributions in October. At a seasonal scale our results emphasized the importance of cuttlefish and red mullet for the global distribution of EEC bottom trawlers. In October, cuttlefish and red mullet were clearly more determining fishers’ location choice than historically harvested species, and also than the overall expected revenue. This is likely due to external constraints such as low cod quota, causing IFD assumptions violated. This study evidenced the importance of getting good insights into spatio-temporal distributions of stocks and fleets to understand fishers’ behaviour and improve mixed fisheries management advic