Marie-Joëlle Rochet’s research while affiliated with French Research Institute for Exploitation of the Sea and other places

The EU Landing Obligation (LO) is designed to reduce bycatch (i.e. unwanted catch) through more selective fishing practices, such as avoidance behaviours which consist in allocating fishing effort to other species, fishing grounds or seasons. Incentives for fishers to change their behaviours depend on their economic performances as well as their ability to avoid bycatch. Changes in economic performances under the LO are evaluated based on cost and revenue equations. The nested grid method is then used to explore the spatial and temporal distribution of landings and discards, and to suggest alternative effort allocation to avoid bycatch. This article is focussed specifically on the French otter trawl fishery in the eastern English Channel and southern North Sea. Results suggest that under the LO the choke species problem will curtail fishing activities earlier in the year, leading to significant economic losses. In the absence of significant quota top-ups (at least 75%), a change in fishing practices consisting in reducing overall bycatch by 30% is insufficient to reduce losses. With a particular attention to choke species, more economically efficient avoidance strategies can be found thanks to the nested grid method.

Under the Landing Obligation (LO) fishers will need to reduce or land fish that were previously discarded. In this chapter we look at how they might be able to do that by summarising a number of studies conducted in various European regions. We start by describing a series of “challenge” trials where fishers tried to reduce their discards by whatever (legal) means they thought best. In some cases, they were able to reduce unwanted catches, in others they were less successful. We also interviewed fishers not involved in the trials to ask them what they thought they could do. We explore their approaches which generally fell into three categories: more selective gear; tactical and strategic changes; and management changes. Scientific data (surveys, landings, and observers data) can also be valuable to help fishers to decide where and when to fish to best avoid unwanted catches and maximise opportunities to catch their quotas. We provide some examples of this type of approach, and also how these can be adapted for use as interactive online apps that fishers can use in planning or whilst at sea.

The Landing Obligation is legislation meant to gradually reduce discards in European fisheries from 2015. Identifying spatial patterns of landings and discards is an important element in mitigating the effects of this legislation on fishing activity. On-board observer data have already been used to address this issue based on models involving statistical assumptions in relation to the non-random spatial distribution of data, which may cause errors in the parameters of interest. An alternative non-model-based mapping method using nested grids is applied to explore the spatial distribution of landings and discards for two French fishing métiers in the Celtic Sea and western English Channel from 2011 to 2016. The grid fineness and the estimate precision are found to depend mainly on the density and variability of on-board observer data. Moreover, an extensive coverage of fishing activity in space and time, and of all fishing vessels, is required to produce meaningful maps.

Modern approaches to Ecosystem-Based Management and sustainable use of marine resources must account for the myriad of pressures (interspecies, human and environmental) affecting marine ecosystems. The network of feeding interactions between co-existing species and populations (food webs) are an important aspect of all marine ecosystems and biodiversity. Here we describe and discuss a process to evaluate the selection of operational food-web indicators for use in evaluating marine ecosystem status. This process brought together experts in food-web ecology, marine ecology, and resource management, to identify available indicators that can be used to inform marine management. Standard evaluation criteria (availability and quality of data, conceptual basis, communicability, relevancy to management) were implemented to identify practical food-web indicators ready for operational use and indicators that hold promise for future use in policy and management. The major attributes of the final suite of operational food-web indicators were structure and functioning. Indicators that represent resilience of the marine ecosystem were less developed. Over 60 potential food-web indicators were evaluated and the final selection of operational food-web indicators includes: the primary production required to sustain a fishery, the productivity of seabirds (or charismatic megafauna), zooplankton indicators, primary productivity, integrated trophic indicators, and the biomass of trophic guilds. More efforts should be made to develop thresholds-based reference points for achieving Good Environmental Status. There is also a need for international collaborations to develop indicators that will facilitate management in marine ecosystems used by multiple countries.

Stock structure of whiting (Merlangius merlangus) in the North East Atlantic is unclear. This study uses mixed effects models to analyse growth variability as a way to investigate stock identification. Growth trajectories for 634 individuals and length-at-age data for 78,686 individuals were analysed for spatial coherence and temporal synchrony in the parameters of the von Bertalanffy growth model. Growth was found to differ among most ICES divisions, and temporal fluctuations were poorly synchronized between areas. This study illustrates how growth analyses can contribute to stock identification, in addition to other data.

Functional groups are sets of species that play a similar role in a food web. We defined functional groups of fish species based on their morphological characteristics, while using expert knowledge for invertebrates. We measured 9 morphological traits of 72 fish species, and carried out multivariate analyses to assign fish species to functional groups. The analysis identified 9 trait-based fish functional groups to which were added 3 expert-based invertebrate functional groups. The habitat (position in the water column) and potential diet of each group were identified from the literature. Using the MEDITS bottom trawl survey data collected at 10 to 800 m depth, we calculated relative change in the 12 fish and invertebrate functional group biomasses for 12 Mediterranean areas over the period 1994 to 2012. Multiple regression trees identified 4 regions with similar changes: (1) the Adriatic and the Ionian Sea; (2) the Tyrrhenian Sea and the Strait of Sicily; (3) the Balearic Islands and other enclosed areas such as the Gulf of Lions and Aegean Sea; and (4) the Ligurian Sea and Sardinia. The biomass of all functional groups increased or remained stable in the first 2 regions, while around half the functional group biomasses decreased in the other 2 regions. These regional differences in functional group biomass changes were mainly associated with regional variations in the time trends of bottom water temperature (37%), bottom water dissolved oxygen (23%) and mean catch levels (9%). This study contributes to the EU Marine Strategy Framework Directive by pro posing food web indicators based on morphologically and habitat defined functional groups.

The 2016 meeting of WGECO was held at the ICES HQ in Copenhagen, Denmark from 6–13 April 2015. The meeting was attended by 17 delegates from 13 countries, and was chaired by Anna Rindorf (Denmark). The work conducted was centred on six Terms of Reference and two advisory requests concerning indicators of Good Environmental Status (GES) of the benthic community, the potential effect of a landing obligation on the benthic ecosystem, the degree to which fisheries are balanced and possible effects of rebuilding predatory stocks, indicators of distribution change, the definition of sensitive species, and the integration of indicators into GES at the descriptor or ecosystem component level. WGECO continued the work to develop and assess indicators of Good Environmental Status of the benthic community. The concept of risk (= Exposure*Effect) was used to assess the risk of impact based on fishing pressure and habitat (or benthic) sensitivity. Examples for each of these two aspects, i.e. Exposure (represented by the overlap between the pressure and habitat maps) and Effect (determined by some measure of habitat sensitivity in relation to the pressure) were presented. In order to fit the framework of the forthcoming workshop on benthic indicators (WKFBI), “good practices” and “lessons learned” relevant to the WKFBI ToRs were identified. Canadian and North Sea case studies were used as examples where two approaches were assessed for determining sensitivity a posteriori and other approaches reviewed. WGECO continued evaluating the effect of a landing obligation on scavengers of the benthic ecosystem. Distribution data were compiled for discarded biomass from the Discardless project, epibenthic scavenger abundances and swept-area estimates from the BENTHIS project and the probability of occurrence of hagfish from FishBase. The analysis did not show a demonstrable link between discarded biomass and either scavengers as a proportion of the benthic community or individual “scavenger” species abundance. The analysis was conducted at ICES Rectangle scale, and it was concluded that it may be more successful at a finer scale of resolution than at the level of the ICES rectangle and with the inclusion of carrion produced by fisheries in the trawl path. These suggestions will be addressed in next year’s work. Six predator fish species that have sustained rebuilding of biomass over periods of at least eight years were identified in the work using the data available to evaluate the ecological consequences of restoring stocks to MSY levels and the degree to which fisheries are “balanced”. Of 20 dependent prey species only one, shrimp, exhibited a decline that could be attributed to its predator, Iceland cod. WGECO concluded that there is little empirical evidence that rebuilding of piscivorous fish stocks has led to declines in dependent prey species. WGECO has advanced methodology to empirically estimate the degree of balance of fisheries in relation to available biomass. Based on this methodology, the fisheries in Iceland and the Bay of Biscay are more balanced than those in the North Sea and New England. Key aspects of species distribution in relation to pressure and climatic drivers were identified and metrics for each aspect identified. These metrics cannot replace a detailed investigation of the spatial distribution but can be used to scan a large number of species distribution for trends and indications of relationships with pressure and climate metrics. Metrics of distribution in the context of the Marine Strategy Framework Directive (MSFD) were discussed. A complex modelling approach to defining suites of ‘sensitive’ fish species was developed to derive more accurate parameter estimates where these data were absent, and a second ‘sensitivity’ metric was designed that explicitly used the relationships between the four life-history parameters. Because of the large amount of missing data that needed to be modelled to support both ‘sensitivity’ metrics, the potential of simply using each species’ maximum recorded length an alternative metric to define ‘sensitivity’ was explored. Such data are available for all species, thereby eliminating the need for the complex estimation modelling. However, it is likely that 15% to 20% of the species deemed to be ‘sensitive’ by the two metrics, would be classified as ‘resilient’ on the basis of maximum recorded length alone. WGECO reviewed the report of the Workshop on providing a method to aggregate species within species groups for the assessment of GES for MSFD D1 (WKD1Agg). This group listed advantages and drawbacks of integration at different levels, and listed some available integration methods. Choice of approach ultimately pertains to policy decision rather than science. Proposed integration approaches are also appropriate to other MSFD descriptors such as D3, D4 and D6.

Fishery discards subsidise the food supply of a large community of scavenging seabirds, thus substantially influencing seabird ecology. Seabird preference for certain types of discards determines the number and composition of discards available for non-avian marine scavengers. To quantify both portions of discards temporally as well as spatially, we have used a modelling framework that integrates the spatial and temporal variation in seabird distribution, seabird attraction to fishing vessels, and discard distribution. The framework was applied to a case study in the Bay of Biscay, where a wide variation in discard consumption was observed across seabird foraging guilds, discard types, periods, and locations. Seabirds removed about one-quarter of the Bay of Biscay discards. The remaining sinking discards have limited potential to subsidize scavenging benthic communities on a large scale, but they may contribute substantially to scavenger diets on a local scale. Changes in food subsidies caused by discard mitigation measures, such as the “landing obligation” in the European Common Fisheries Policy, are likely to have ecosystem effects on both scavenging seabirds and non-avian marine scavengers.