Emergence of a new predator in the North Sea: evaluation of potential trophic impacts focused on hake, saithe, and Norway pout

During the last 15 years, northern European hake (Merluccius merluccius) has increased in abundance, and its spatial distribution has expanded in the North Sea region in correlation with temperature. In a context of global warming, this spatial shift could impact local trophic interactions: direct impacts may affect forage fish through modified predator–prey interactions, and indirect impacts may materialize through competition with other resident predators. For instance, North Sea saithe (Pollachius virens) spatial overlap with hake has increased while saithe spawning-stock biomass has decreased recently notwithstanding a sustainable exploitation. In this context, we investigated the range of potential impacts resulting from most recent hake emergence in the North Sea, with a particular focus on saithe. We carried out a multispecies assessment of North Sea saithe, using the Stochastic MultiSpecies (SMS) model. In addition to top-down processes already implemented in SMS, we built in the model bottom-up processes, relating Norway pout (Trisopterus esmarkii) abundance and saithe weight-at-age. We simulated the effects, on all North Sea species being considered but focusing on Norway pout and saithe, of combining different hake abundance trends scenarios with the inclusion of bottom-up processes in SMS. North Sea saithe FMSY was then evaluated in a multispecies context and contrasted with single-species value. The different scenarios tested revealed a negative impact of hake emergence on saithe biomass, resulting from an increase of predation pressure on Norway pout. These results confirm the competition assumption between saithe and hake in the North Sea and might partially explain the most recent decrease of saithe biomass. This study also highlighted that taking into account bottom-up processes in the stock assessment had a limited effect on the estimation of saithe FMSY which was consistent with single-species value

Mixed-fisheries management plans in Europe: Can we formulate a simple bioeconomic advice on a complex reality?

The recognition of the complex biological and economic interactions occurring in mixed-demersal fisheries have long underpinned the development of fleets- and fisheries-based models and data collection in European fisheries. More recently, mixed-fisheries management plans are being designed and implemented in the frame of the EU Common Fishery Policy. The central element of these plans is the option to depart from the single-stock MSY-based scientific advice for setting Total Allowable Catches, provided that there is scientific evidence of “choke species” effects that can lead to an early closure of an entire fishery. Single-stocks’ Fmsy upper and lower ranges have been defined, that would maintain high yields and low risks while providing some flexibility to cope with inter-annual fluctuations of the various stocks. These complex developments raise multiple questions, but providing simple answers and robust scientific advice to these is not straightforward. In 2018, important milestones are being reached, which see the culmination and the mutualisation of parallel scientific initiatives, developed in different national and pan-european bodies such as ICES and STECF. An operational process is developed, bringing together ecological and bioeconomic models in a flexible framework. Outcomes are summarised in a combined scientific advice accounting for the risks of choke effects, analysing alternative catch options and suggesting TACs that would be meaningful trade-offs between economic and ecological constraints. This presentation will highlight the main features and outcomes of this complex process, reflecting also on the challenges and opportunities of accounting for mixed-fisheries aspects instead of single-stock approach

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

Fishery-Based indicators of Management Impact: Assessing Relevance and Robustness Using A Bio-Economic Simulation Model

Indicators are widely used in fisheries management decision process as measures for monitoring ecosystem status or management performance. In the current context, the shift to an ecosystem-based approach to fisheries management requires to complete usual population or community indicators with indicators reflecting state and dynamics of fishing activity as well as economic viability. However, it is difficult for decision makers to select relevant indicators among the numerous existing ones. In addition, the complexity of the mechanisms involved makes the unequivocal interpretation of indicator variations seldom possible using only statistical models. We propose to resort to the ISIS-Fish fishery dynamics model to select robust and relevant fishery indicators. ISIS-Fish population submodel was set up to reproduce major processes of anchovy population dynamics in space and time and surplus production models were used for the other target species of the fishery. To take fishermen behavior into account while modeling fleet dynamics, we considered a discrete choice model using economical interest in the different possible métiers, fishers habits and management constraints within a random utility modeling framework. Applying sensitivity analysis methods, simulation designs were built crossing a variety of management scenarios and uncertainty hypotheses. Consequently, a list of resulting candidate metrics referring both to population and fishing activities were computed and statistically analyzed. Metrics that were the most sensitive to management and the most robust to uncertainties were considered to be relevant and selected for assessing management impact on the fishery

Working Group for the Bay of Biscay and the Iberian Waters Ecoregion (ICES WGBIE) (2-9 May 2109)

The ICES Working Group for the Bay of Biscay and the Iberian Waters Ecoregion (WGBIE) assesses the status of 23 stocks distributed from ICES Divisions 3.a–4.a though to Subarea 9, mostly distributed in Subareas 7, 8 and 9. The group was tasked with conducting assessments of stock status for 23 stocks using analytical, forecast methods or trends indicators to provide catch forecasts and a first draft of the ICES advice for 2019. For two of the Nephrops stocks updates were provided on catch data with the advice release delayed until October after the completion of the surveys used for the assessment. Analytical assessments using age-structured models were conducted for the northern stock of white anglerfish, the northern and southern stocks of megrim, four-spot megrim and sole in the Bay of Biscay. The two hake stocks and one southern stock of anglerfish were assessed using models that allow the use of length-structured data (no age data). A surplus-production model, without age or length structure, was used to assess the second southern stock of anglerfish and an age-length structure model was used for the European seabass in the Bay of Biscay. The state of stocks for which no analytical assessment could be performed was inferred from examination of catch, commercial LPUE or CPUE data and from survey information, where available. The northern stock of hake was benchmarked this year to incorporate discards into the model that were previously omitted. New reference points with the accepted benchmark assessment were proposed by the group and new proxy biomass reference points where proposed for black anglerfish in Division’s 7b-k, 8abd. A recurrent issue significantly constrained the group’s ability to fully address the terms of reference this year. Despite an ICES data call with a deadline of six weeks before the meeting, data for most stocks were submitted to ICES only two days before the start of the meeting and in one case 2 days after the meeting commenced. This delayed the process of having the data quality checked and the assessment completed before the start of the working group. This is an important matter of concerns for the working group members. The structure of the report is set out with section 1 presenting a summary of each stock, discussing general issues and conclusions. Section 2 provides descriptions of the relevant fishing fleets and surveys used in the assessment of the stocks. Sections 3–18 contains the single stock assessments

Report on the STECF Expert Working Group 17-12 Fisheries Dependent Information: ‘New-FDI’

The STECF expert working group (EWG) on Fisheries Dependant Information (FDI) took place in JRC, Ispra from 23 to 27 October 2017 to review the data transmitted by Member States under a new data call (‘New-FDI’). The new data call specification was designed with three broad aims in mind i) Compatibility between the New-FDI data and the data held in the Fleet Economic database. ii) Ability to encompass all EU registered vessels including those from the Mediterranean, Black Sea and external waters fleets. iii) Ability to assess effects of management measures. The main purpose of the EWG was to judge if the call specification was appropriate to accomplish the above aims and to consider any difficulties encountered by member states in fulfilling the data call. Two terms of reference also allowed trial analyses to be conducted of a type relevant to the third broad aim. The EWG addressed all Terms of Reference during the meeting and drew conclusions on the modifications required for the New-FDI data call going forwards. Prior to the EWG it had been agreed by STECF Bureau that the report of the meeting would not be presented to STECF for approval as an STECF report but published separately (as a JRC technical report). This report therefore presents the data, methods observations and findings of an EWG of the STECF but the findings presented in this report do not necessarily constitute the opinion of the STECF or reflect the views of the European Commission and in no way anticipate the Commission’s future policy in this area.JRC.D.2-Water and Marine Resource

STECF Fisheries Dependent Information – FDI (STECF-19-11)

Commission Decision of 25 February 2016 setting up a Scientific, Technical and Economic Committee for Fisheries, C(2016) 1084, OJ C 74, 26.2.2016, p. 4–10. The Commission may consult the group on any matter relating to marine and fisheries biology, fishing gear technology, fisheries economics, fisheries governance, ecosystem effects of fisheries, aquaculture or similar disciplines. The STECF reviewed the report of the EWG on Fisheries-dependent Information during its winter 2019 plenary meeting

STECF Fisheries Dependent Information – FDI (STECF-19-11)

Commission Decision of 25 February 2016 setting up a Scientific, Technical and Economic Committee for Fisheries, C(2016) 1084, OJ C 74, 26.2.2016, p. 4–10. The Commission may consult the group on any matter relating to marine and fisheries biology, fishing gear technology, fisheries economics, fisheries governance, ecosystem effects of fisheries, aquaculture or similar disciplines. The STECF reviewed the report of the EWG on Fisheries-dependent Information during its winter 2019 plenary meeting