What happens to discards?
Following the introduction of the obligation to land fishing discards, the Ifremer DREAM project (Devenir des Rejets de l’Air au fond de la Mer) was developed to better understand the process of reintegration of this biomass into the ecosystem. These discharges, at the surface, constitute a significant part of the food resource for 52% of seabird species such as gannets and larids (i.e. gulls). They even have a direct impact on the feeding ecology, reproduction and population dynamics of these species. However, despite numerous studies on the relationship between fishing discards and seabirds, little is known about the proportion taken by avian predation.
Following the introduction of the obligation to land fishing discards, the Ifremer DREAM project (Devenir des Rejets de l’Air au fond de la Mer) was set up to better understand the process of reintegration of this biomass into the ecosystem. These discharges, at the surface, constitute a significant part of the food resource for 52% of seabird species such as gannets and larids (i.e. gulls). They even have a direct impact on the feeding ecology, reproduction and population dynamics of these species. However, despite numerous studies on the relationship between fishing discards and seabirds, little is known about the proportion taken by avian predation.
The objective of the “birds” section conducted by PELAGIS is to quantify the quantity of fish consumed by birds during discharges, and to deduce the remaining quantity that returns directly to the environment.
Firstly, the phenomenon will be studied using a spatial approach based on existing data collected during MEGASCOPE oceanographic campaigns carried out mainly in the Bay of Biscay and the Channel (PELGAS, EVHOE, IBTS and CGFS). In a second phase, a more quantitative consumption approach will be carried out. More detailed information gathered during discard events on the composition of the flock of tracking birds (species, number of individuals, age classes, etc.) and on the composition of the discards (composition, biomass, buoyancy) will be integrated via modelling. This model will also make it possible to integrate data from professional trawlers in order to better reflect reality.
In the long term, we hope to obtain elements of ecosystem responses such as the dependence of birds on discards, as well as an understanding of the phenomenon to help manage the resource, particularly by discarding at sea.
