MIRROR · Through the looking-glass: investigating the effectiveness of fish condition in mirroring trawling disturbance

Through the looking-glass: investigating the effectiveness of fish condition in mirroring trawling disturbance

The study of fishing disturbances at relevant spatial and temporal scales to inform and build realistic management strategies represents one of the main challenges to the next generation of fisheries scientists, stakeholders and policy makers. The evaluation of trawling impact on the productivity of demersal fish species is a crucial knowledge to maintain the yield from wild-capture fisheries and to cope with the global increasing demand of sea proteins. The idnirect effects of trawling disturbance (TD) are still understudied. It remains still largely unknown how the alteration of benthic dynamics due to chronic TD can trigger unpredictable cascade effects involving most ecological components impairing the system to cope with the natural environmental variability. MIRROR aimed at investigating the TD effects on the diet and condition of a target species (Mullus barbatus – red mullet) in the Central Mediterranean Sea. MIRROR explored the effects that changes in fish condition can have on life-history traits (e.g. growth and reproductive potential). Understanding the link between TD, condition and LH traits represents a steppingstone for the inclusion of condition as an indicator for the management of exploited species. The red mullet, Mullus barbatus, was chosen as model species being one of the most commercially important benthivorous species in the Mediterranean Sea (95% of landing composition, 6.73 €/kg mean EU countries values). The red mullet is a good indicator species with respect to habitat quality, a defined income breeder whose number of eggs depend on food intake and whose energy reserves are not mobilized from other tissues during reproduction. These reproduction and energy storage strategies allow examination of the secondary effects of TD on diet, condition and LH traits (growth and reproductive potential). The indirect monitoring of benthic prey communities though the proxy of body condition of selected fish species may represent the only feasible way to integrate the benthic system into the ecosystem-based fisheries management. The monitoring of entire marine communities at spatial scales relevant to a fishery is too costly and time consuming, thus justifying the need for new indicators and the importance of MIRROR’s contribution towards an ecosystem approach, in the Mediterranean Sea where evident knowledge gaps on the ecosystem effects of TD remain. MIRROR has encompassed 3 main objectives: 1) Investigate diet and condition changes along TD gradients, by comparing areas with different trawling histories and environmental conditions to provide an indication at what trawling intensity fish condition is maximised and an indirect measure of benthic prey status; 2) Investigate the consequences of condition changes on selected LH traits such as growth, onset of maturity, reproductive potential and survival (link established by only few studies); 3) Investigate the effect of TD on the condition of red mullet through space and identify trawling intensity threshold (vulnerability maps) with ramifications on population parameters that are the focus of fisheries management.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз