Assessment of cetacean–fishery interactions in the marine food web of the Gulf of Taranto (Northern Ionian Sea, Central Mediterranean Sea)

The exploitation of fishery resources actsas a driving force on cetaceans both directly, bydetermining their fishing mortality or injury as bycatchspecies, and indirectly, through the lowering theavailability of their prey. This competitive overlapbetween fishing and cetaceans often results in inadequatesolutions so that in some cases there have beencases of intentional cetacean culling to maximizefishing production. A modelling approach applied to investigate the ecological roles of cetaceans in thefood web could prove more effective to integrateecological and fishing aspects and to provide suggestionsfor management. The comparative analysiscarried out in the Gulf of Taranto (Northern IonianSea, Central Mediterranean Sea) showed that fishingexploitation provides impacts on the investigated foodweb greater than those due to cetacean predation.Trawling was estimated to be the most negativelyimpacting fishing gear considering the mortality ratesand consumption flows. On the other hand, the stripeddolphin was the main impact on the food web due to itshighest consumption flows. Analysis showed a negativeand non-selective impact on the exploited speciesdue to the fishing gears, while the odontocetes provedto select their prey species and provide a positiveimpact in the assemblage. In particular, while thefishing gears are primarily size selective, targetingmostly large and economically valuable fish, the odontocetes seem to follow a co-evolution processwith their prey, developing a specialization in theirresources, providing control of the meso-consumersand ensuring a trophic stability in the ecosystem.