Fishing for MSY: using “pretty good yield” ranges without impairing recruitment

Pretty good yield (PGY) is a sustainable fish yield corresponding to obtaining no less than a specified large percentage of the maximum sustainable yield (MSY). We investigated 19 European fish stocks to test the hypothesis that the 95% PGY yield range is inherently precautionary with respect to impairing recruitment. An FMSY range was calculated for each stock as the range of fishing mortalities (F) that lead to an average catch of at least 95% of MSY in long-term simulations. Further, a precautionary reference point for each stock (FP.05) was defined as the F resulting in a 5% probability of the spawning-stock biomass falling below an agreed biomass limit below which recruitment is impaired (Blim) in long-term simulations. For the majority of the stocks analysed, the upper bound of the FMSY range exceeded the estimated FP.05. However, larger fish species had higher precautionary limits to fishing mortality, and species with larger asymptotic length were less likely to have FMSY ranges impairing recruitment. Our study shows that fishing at FMSY generally is precautionary with respect to impairing recruitment for highly exploited teleost species in northern European waters, whereas the upper part of the range providing 95% of MSY is not necessarily precautionary for small- and medium-sized teleosts.</jats:p

Effects of a fishery closure and prey abundance on seabird diet and breeding success: Implications for strategic fisheries management and seabird conservation

Industrial forage fish fisheries may reduce prey availability affecting diet and breeding success of marine predators. However, evidence for fisheries effects on predator demography remains rare, hindering evaluation of their impact on populations. Using 25 years of data on the commercial lesser sandeel fishery in the north-western North Sea, we evaluated the effectiveness of the closure in safeguarding breeding success of four seabird species - black-legged kittiwake, common guillemot, Atlantic puffin and razorbill. We also tested for effects of a scientific fishery in the closed area on breeding success. We quantified how changes in the diet of chicks for the four seabird species were influenced by the abundance of sandeels and the alternative prey species, European sprat, and the potential prey behavioural disturbance effects of sandeel fishing on the prey. Finally, we examined how changes in chick diet and prey abundance have shaped long-term variation in seabird breeding success. The period of fishery operation was associated with a decline in kittiwake breeding success in colonies with foraging ranges overlapping the closed area, from 52 % of young fledged pre-fishery to 23 % during fishery operation. Breeding success increased by approximately 10 % in the period following fishery closure to 2018. We document wide uncertainty around this increase in breeding success, partly driven by variation in the responses of individual colonies. For guillemot, razorbill and puffin we found no evidence for negative effects of the fishery on breeding success, nor for positive effects arising from its closure. We found no evidence for an impact on breeding success of the scientific fishery. The proportion of sandeel in chick diet was positively associated with breeding success in the four species, albeit with only weak evidence for puffin. Fishing effort was associated with a decreased proportion of sandeel in puffin diet, a lower proportion of the sandeel component of the diet consisting of 0-group in kittiwake, razorbill and puffin, and with decreased kittiwake breeding success. Our findings provide quantitative evidence for how forage fish fisheries may impact seabird demography, highlighting the species-specific nature of responses, and the difficulties in teasing apart drivers amongst ongoing environmental change. Time-area fisheries closures show promise as a tool for positively affecting productivity in some seabird species. However, we identify important caveats around its effectiveness for strategic seabird conservation and aspirations of net gain

Predicting effect of changes in ‘fishable’ areas on fish and fisheries

This report aims to investigate the available tools for predicting the impact of various spatial management options on fisheries distribution, yield, profitability, and selectivity. Such spatial plans may affect the remaining ‘fishable’ areas by displacing and concentrating the fishing pressure, and so may alter stock abundances, distributions, size- and species catch composition and fuel expenditure and cost. The report provides early insights into how spatial plans that exclude certain fishing activities may affect these outcomes. Spatially explicit approaches are used, along with scenarios of underlying stock productivities and distributions, to assess the performance of spatial management measures. Scenario-based testing is conducted to examine the interrelated effects of management options and stock productivity. A major aspect of the work involved gathering and organizing information on specific zones from several sources such as Natura2000, CDDA, SPA, SAC, and UK-defined areas. We found that most of these zones did not have any previous management plans in place that would outline fishing restrictions. Therefore, we developed a method of assigning limitations to certain fishing techniques based on the perceived vulnerability of specific areas to these practices. This approach has allowed for an examination of how these restrictions potentially affect fish and fisheries.Initially, we used a static approach in anticipating the potential fishing effort displacement to measure the impact of fishing in the Northeast Atlantic area. Our research shows that while such spatial management measures may reduce fishing opportunities, it may be possible to offset in the short term some of these spatial opportunity losses by fishing in nearby locations (Figure 1). On the Med side, an analysis of fishing effort displacement from restricted areas in the Adriatic Sea is exemplified in a before/after situation, showing that the effort is not reduced but redistributed and can further redistribute far from the restricted areas.If in the short term, spatial management may increase operating costs by displacing the effort, this may eventually be recovered in the long term if the stock is recovering from previous overfishing. To determine whether conservation measures (such as Marine Protected Areas) that limit specific fishing techniques and areas could help mitigate the negative effects of fishing, a more advanced approach to fisheries management is required. This involves using a dynamic approach deploying spatial bioeconomic models that consider changes in environmental drivers and spatial restrictions, allowing it to assess potential changes in fishing effort facing, for example, new regulatory or ecological conditions. While bioeconomic models require more data and assumptions to forecast "alternative futures", they offer a more comprehensive approach to fisheries management, which is particularly useful as testing MPAs effects in real life is a challenge. A suite of bioeconomic models has been deployed to provide preliminary findings about the effect of spatial restrictions on fish, fisheries, benthos and bycatch:•International fisheries active in the North Sea were modeled using DISPLACE, testing the implementation of spatial restrictions to specific fishing techniques. Based on the simulations, the benthos status improved in areas where bottom fishing was excluded from previously fished areas and decreased in newly fished areas. However, the gain by EU closure areas was limited and no change in fish size selectivity detected as these areas are not really significant for bottom fishing and have not been initially designated to modify selectivity.•In the eastern Ionian Sea, different spatial restrictions for fishing techniques were evaluated using the DISPLACE model. While there may have been advantages to the fishing restrictions, there has been an increase in both unwanted catch and fishing effort, and no significant improvements were observed in the harvesting of adult fish. The alternative scenarios tested were insufficient to make fishing fleets more selective. Additionally, certain fishing fleets were economically adversely affected.•East Adriatic trawlers may benefit from being forced closer to shore after the closure of their traditional fishing grounds while the Italian trawling fleet experiences higher steaming costs, likely due to the closure of nursery grounds and FRAs and redistribution to other areas. ECOSPACE predicted that the mean trophic level of fish caught in deeper waters, closed to bottom trawlers but still accessible to pelagic fisheries, will increase. ECOSPACE indicated a marked rise in biodiversity in the central Adriatic area under the closures scenario. The reported outcome for ECOSPACE should be considered preliminary as it may have been influenced by the assumptions used to build and parameterize the model.•ECOSPACE predicted a significant rise in biomass for the southern North Sea in response to area closures. Fish biomass could increase by up to 15%. However, this increase may not be sufficient to compensate for the decline in biomass outside the MPA from more pressure on specific fish species. This, in turn, caused a decrease in overall catches. Within the MPAs, all fishing fleets experienced losses of up to 50%, while outside the MPAs, there was an increase of up to 13% in catches. Nonetheless, the gains outside the MPAs did not compensate for the losses incurred due to the closures.•ECOSPACE investigation on how spatial fisheries management affects the food web and fisheries in the eastern Ionian Sea was used to evaluate the spatial distribution of fishing effort for two scenarios - one with existing closed areas and another with possible future closed areas. Preliminary findings indicate that if all fishing activities are restricted from MPAs (as in the second scenario), there is an increase in fishing effort throughout the study area, rather than just around the MPAs.•Using an agent-based model of the southern North Sea and the German fisheries, spatial restrictions were shown to possibly result in reduction in fishing effort, concentration of fishing effort in the remaining open areas, longer steaming times, and lower profits. The spatial scenarios heavily affect the German shrimp fishery due to large overlaps with coastal shrimp fishing grounds, while flatfish and Nephrops fisheries are less affected. Scenarios reduced the fishing effort of all métiers suggesting that switching métiers and relocating fishing effort could not negate the impact of spatial fishing closures.•In the North Sea, the OSMOSE model was used to test scenarios of effort redistribution and effort reduction. The results indicated a slight increase in the biomass of demersal species, but a significant decrease in the biomass of pelagic species. Both scenarios showed an increase in the relative biomass of protected, endangered, and threatened (PET) species when effort was reduced. Additionally, changes in the food web led to an increase in the catch of commercial species above minimum conservation size.•A spatial BEMTOOL is being implemented applied to the Adriatic and western Ionian Seas active and passive demersal gears fleet segments. The effort data for the main ports in the study area was explored to identify the fishing grounds that are more frequently visited by fishers and to gain insights into their fishing strategies.In summary, prohibition of certain fishing techniques in all currently designated MPAs has minimal impact on the fisheries economy of most fleet-segments examined and fish populations in the short term. This is primarily because these areas are preserved due to their significance as hotspots of EU marine biodiversity, rather than selected for a high abundance of commercial fish. Some segments, however, may require &gt;15% extra effort to break even. In an upcoming study, SEAwise partners will investigate conservation areas the selectivity of fish size

Workshop on the production of swept-area estimates for all hauls in DATRAS for biodiversity assessments (WKSAE-DATRAS). ICES Scientific Reports, 3:74.

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)

Workshop on the production of abundance estimates for sensitive species (WKABSENS). ICES Scientific Reports, 3:96.

The Workshop on the production of annual estimates of abundance of sensitive species (WKABSENS) met to define sensitive species, collate ICES assessments of abundance where these are available, and estimate indices of their abundance per swept-area where not, for the OSPAR area. The analyses identified 140 potentially sensitive species or species complexes, among which 10 are diadromous and three are coastal, 20 have uncertain species ID and nine were identified as sensitive in only one of the sources examined. Among the sensitive species and species complexes, there was sufficient data to provide abundance indices for 50 species, of which 16 had existing stock assessments whereas the workshop derived abundance estimates for the remaining 34 species from survey data. Three statistical modelling approaches (binomial, General Additive Models (GAMs) and VAST) and were explored and the final abundance indices were calculated using GAMs. The species were divided into stocks before estimating abundance indices where these could be identified from the spatial distribution of the species in the survey. The group considered that a similar analysis using data from additional surveys, commercial indices or data from bycatch observers can potentially provide improved abundance estimates for species with variable or low catchability, such as deep-water and pelagic species