Notes and comments on the ex-post evaluation of the fisheries agreement EU-Morocco

This report presents a summary of the content of the ex-post evaluation of the fishing agreement between the EU and Morocco

Towards abundance estimates for jack mackerel in the South Pacific based on acoustic data collected by the commercial vessels

Pelagic trawlers make intensive use of echosounders and therefore could potentially be used as acoustic data collection platforms. This project investigated the possibility of collecting acoustic data and its potential utility to estimate fish stock biomass. The scope of the project was to develop and - when possible - test the tools that would be necessary for large scale data collection from commercial vessels, and investigate the suitability of acoustic data to derive abundance indices

Using acoustic data from pelagic fishing vessels to monitor fish stocks

Pelagic trawlers make intensive use of echosounders and therefore could potentially be used as acoustic data collection platforms. The present project has investigated the possibility of collecting acoustic data during normal fishing trips and the potential of this data to estimate fish stock biomass. Within this project, two real-scale data collection trials were realised, one in spring 2012 during the blue whiting fishing season, and one in summer 2012 during the North Sea herring and sprat fishing season

Hydrography and Jack Mackerel stock in the South Pacific

The study on Hydrography and Jack Mackerel stock (Trachurus murphyi) in the South Pacific is currently one year underway. The main achievement consisted of collecting detailed datasets on Chilean, Peruvian and European fisheries activities and information on the hydrographical / biochemical and environmental conditions present in the South Pacific. The hydrographical and environmental datasets are based on the analyses of available acoustic information collected on-board survey and fishing vessels and satellite imagery data. Jack Mackerel habitat models are being developed based on these datasets. These models will be used to produce maps of the potential habitat of Jack Mackerel, on the basis of which different stock structure hypotheses will be tested. The models developed so far are able to accurately represent the distribution of Jack Mackerel as observed by fishing and surveying activities, although some additional investigations are needed to improve the statistical fits. Good fits with hydrographical conditions have been found. The models are not yet ready to be used for testing stock structure hypotheses, but this should be the case in the near future. During the first year of the project, an extensive literature review on Jack Mackerel has also been conducted, and a synthesis has been written, giving an overview on the species biology, ecology and stock structure. The literature suggests that a meta-population structure can be seen as a potential stock structure hypothesis. The literature review also contributed to identify environmental variables that should be crucial to define the suitable habitat of Jack Mackerel. Previously published results indicate, among others, temperature and dissolved oxygen ranges in which Jack Mackerel is able to survive. Finally, a framework to derive reference points for Jack Mackerel, assuming the single stock structure as used within the SPRFMO assessment, has been developed and made available to the SPRFMO Science Committee for review. Analyses of the assessment results within this framework indicate that the fishing mortality corresponding to maximum sustainable yield might be at around 0.15 per year with a corresponding spawning stock biomass of around 10 million tonnes. Different harvest control rules have been evaluated and show little risk to overexploitation in the medium and long term, although these result heavily rely on strong incoming year classes. The tools to evaluate sustainable management options for the Jack Mackerel population, when a stock structure other than a single one is assumed, are currently under development. The design of scenarios to be tested depend on the results of the habitat modelling exercises. Therefore, preliminary results will only become available early 2014

Hydrography and Jack mackerel stock in the South Pacific - Final report

This study aims (i) to identify the most likely population structure hypotheses of Jack mackerel, (ii) to identify management objectives for Jack mackerel, and (iii) to evaluate sustainable management strategies to achieve these objectives. These three elements were considered through literature review, statistical and population dynamics modelling. Two different conclusions were drawn: a conclusion towards most likely population structure and a conclusion towards most likely stock structure

Age-structure-dependent recruitment: a meta-analysis applied to Northeast Atlantic fish stocks

Exploitation alters the age structure of fish stocks. Several stock-specific studies have suggested that changes in the age structure might have consequences for subsequent recruitment, but the evidence is not universal. To investigate how common such effects are among 39 Northeast Atlantic fish stocks, relationships were tested between age structure (spawner mean age, age diversity, and proportion of recruit spawners) and recruitment (number of recruits, sensitivity to environment, and recruitment variability). Significant correlations in the expected direction were observed for a few stocks, but not for the majority; significant correlations in the opposite direction were also found. Meta-analyses combining the stock-level tests revealed that none of the effects were significant overall. However, effects were significant for some species (cod, haddock, and plaice) and indices. The low variability in the age structure might explain the absence of significant effects for individual stocks. Other reasons could be the absence of a biological basis (reproductive characteristics not dependent on age) or the stronger influence of environmental variability than of age structure on recruitment

Is age structure a relevant criterion for the health of fish stocks?

The age and size structure of exploited fish stocks is one of the criteria for Good Environmental Status of commercial fish. However, two underlying assumptions to this criterion remain to be tested: first, that a well-balanced age structure is indeed indicative of a “healthier” stock, and second, that managers can exert a control on the age structure, independently from the regulation of stock abundance. This study investigates these questions using simulations from a population model in which recruitment is based on egg production, which is more sensitive to age structure variations than the traditionally used spawning stock biomass (SSB) and that was parameterized to represent the population dynamics of North Sea cod, plaice, and herring. Our results show that (i) the age structure is highly dependent on the selection pattern, as well as on the level of fishing mortality; (ii) the selection pattern determines the ability of fish stocks to withstand, and recover from, external perturbation; and (iii) the selection pattern determines the output of the fishery providing the management option to balance stable but relatively low yields vs strongly fluctuating high yields. Therefore, we propose to make the selection pattern, for which clear management targets can be set, a policy goal instead of the age structure that is currently in plac