Ecosystem Impacts of the Landing Obligation for Unwanted Catch in Thermaikos Gulf (Greece)

ABSTRACT Discards by marine commercial fisheries have been an issue of major concern to the scientific community in recent years. We modeled the ecological and trophic consequences of a mandatory landing obligation (LO) regulated by the reformed Common Fisheries Policy [Regulation (EU) 1380/2013] on the Thermaikos Gulf ecosystem (northwestern Aegean Sea, Greece, northeastern Mediterranean Sea). We used an ECOPATH with ECOSIM model that was calibrated for 2000–2016 to simulate ecosystem effects through 2025. A reference scenario (Sc0) for current fisheries and discarding practices in the gulf was used to compare with simulated discarding scenarios. Two scenarios simulated enforcement of the LO after the calibration period, including one that considered all functional groups with available commercial fisheries catches and one with species subject to minimum conservation reference size. Two other scenarios tested different discarding management practices, during which discards were reduced to zero. All scenarios demonstrated smaller impacts on commercial marine species and larger impacts on species that rely on discards as their main food source. Our findings highlighted the importance of scientific surveys for data collection to support modeling and explore discard handling policies. Studies of gear selectivity and commercial fisheries documentation and regulation may facilitate a better implementation of the LO to reduce discard mortality.