Performance of a northwestern Mediterranean bottom trawl fleet: How the integration of landings and VMS data can contribute to the implementation of ecosystem-based fisheries management

The European Union has established a framework to achieve or maintain good environmental status in the marine environment by 2020. The Marine Strategy Framework Directive requires the application of the ecosystem approach to the management of human activities, covering all sectors having an impact on the marine environment. However, fisheries in the Mediterranean are far from a systematic implementation of an ecosystem-based fisheries management (EBFM). Aiming to address this issue, this study explores the potential of the relationship between daily yield by vessel (landings and income by species) and vessel position (known via vessel monitoring system) as a tool for fleet management. This approach is possible due to the current dynamics of Mediterranean fleets, with vessels returning daily to the harbour where landings are registered as weight and income by vessel. Moreover, vessels of >15 m total length have been compulsory monitored by VMS since 2005. A bottom trawl fleet that operates in the northwestern Mediterranean was chosen to develop this approach. Different groups of trawlers were identified, which could be linked to the strategies displayed by the fishermen that were mainly driven by the target species dynamics. Accurate knowledge of the fishing targets driving the fleet dynamics and of the fishing strategies at the vessel level (i.e. fishing ground habitat where the fishing pressure is exerted and corresponding landings) are shown to be a feasible tool for fleet management.     

A spatio-temporal ecosystem model to simulate fishing management plans: A case of study in the Gulf of Gabes (Tunisia)

The Gulf of Gabes located in southern Tunisia is one of the most productive ecosystems in the Mediterranean Sea. Despite its ecological importance, it is subject to high fishing pressure affecting the different components of the ecosystem. Given the multispecies, multigear nature of the fishery, there is a need to manage trade-offs between environmental and economic objectives. In this study, an Ecospace model was developed based on the previously constructed Ecopath model of the Gulf of Gabes and calibrated for the period 1995–2008 to investigate the response of the ecosystem to a set of alternative spatial management scenarios. These scenarios were derived from the current fishery regulation owing the important interest expressed by local fishery managers to assess new management measures. The results showed for each management scenario how bottom trawling and coastal fishing impact the different trophic groups and the complexity of interaction between these two fishing activities. Furthermore, spatially explicit simulations were performed to identify regions where the management measures are effective. Results suggested that for some trophic groups, these regions are well-defined which would be interesting to propose more accurate spatial measures. Finally, several indicators were calculated to evaluate the proposed management plans and provide managers with a straightforward set of decision rules to describe the potential trade-offs and fulfill both fisheries and conservation management objectives in the context of an ecosystem approach. The decision rules were based on observed trends to reduce uncertainty relative to the model complexity and provide consistent advice to decision-makers.     

Composition, structural characteristics and temporal patterns of fish assemblages in non-tidal Mediterranean lagoons: A case study

The importance of transitional water ecosystems as nursery habitats and feeding grounds for fish species is well-known. Detailed studies of colonization patterns of fish guilds in response to biotic and abiotic drivers are however unevenly distributed among ecosystem types. We address here the temporal variability of fish assemblages in small non-tidal lagoons in the Mediterranean basin. The study was carried out at the Acquatina lagoon (Lecce, Italy) where four stations, situated in two habitat types along a confinement gradient, were sampled twice per month for one year with fyke nets. Forty-five taxa ranging across 20 families were collected, with the most abundant species, Atherina boyeri, accounting for more than 95% of total abundance. Pooling all species together (excluding sand smelt), the structural features of the assemblage, relative abundance of families, and abundance of individual species all showed significant temporal patterns. Mean abundance peaked in Summer and Autumn and fell in Winter, whereas taxonomic richness and diversity were highest in Summer and lowest in Spring. Within the fish assemblage, multivariate ordination showed temporal segregation of species belonging to the same family or genus and expected to be functionally similar, suggesting that they avoid competition for space and resources by timing inward migration and peak occurrence differently. Of the environmental driving forces, which also showed temporal patterns of variation, salinity was the main factor affecting the distribution of individuals and species. The catch of young individuals of several marine species confirmed the role of this small lagoon as a nursery and feeding area, and emphasized the need for further studies.     

Evaluation of a bycatch reduction technology by fishermen: A case study from Sicily

Bycatch reduction technologies (BRTs) have been developed to limit the incidental capture of non-target marine species in fishing gear, especially those species of special concern. However, in the absence of enforcement, the proven effectiveness of a BRT alone does not guarantee its adoption by fishermen. Human factors also play a fundamental role. This case study was directed at evaluating the willingness of Sicilian longline fishermen to use relatively large circle hooks (size 16/0) as a BRT for the loggerhead sea turtle Caretta caretta. Fishermen were involved in testing circle hooks with their fishing vessels and their own commercial fishing gear, and their opinions before and after trials at sea were recorded. The present study showed the importance of creating a positive human context for testing a BRT. Findings provided additional confirmation about the usefulness of relatively large circle hooks to reduce the bycatch of loggerhead sea turtles on drifting longlines. Interviews before and after trials at sea indicated that socio-economic and emotional factors are essential for successful uptake of BRTs. Crews of large fishing vessels stated that they would be willing to use circle hooks in months with a high probability of turtle captures (June-September) if an economic incentive was provided and there was also public acknowledgement of their efforts. The fishermen's cooperatives association involved in the project is currently evaluating the creation of a product label identifying the harbors where fishing was performed using circle hooks.