Seabird mortality associated to trawlers in the Patagonian Shelf: discard management as measure to mitigate the number of contacts with fishing gear

FAVERO, M.; GANDINI, P.; BLANCO, G.; FRERE, E.; QUINTANA, F.; RABUFFETTI, F.; SCHIAVINI, A.; YORIO, P.; GARCÍA, G.; COPELLO, S.; SECO PON, J.P.

Ciudad del Cabo, Sud Africa

Conferencia; International Albatross and Petrel Conference; 2008

This study investigate the level of seabird mortality caused by the domestic trawl fleet (“freshies”) fishing in central Patagonia (37-48°S), analyzing the effect of environmental and operational variability on the level of interactions. With a total of 135 vessels the fleet is one of the largest in Argentina. Specifically tasked seabird observers were placed onboard trawlers during summer and winter seasons of the years 2006 and 2007. Type and number of seabird interactions (i.e. contacts with fishing gear) were recorded during shooting and hauling operations, covering 72 days of observation and ca. 500 operations. Black-browed albatrosses, White-chinned Petrels, Southern Giant Petrels and Southern Royal Albatrosses were the most important species interacting with trawlers. Confirmed mortalities of Black-browed and Southern Royal albatrosses were the result of collisions and entanglement with the warp cable while birds were scavenging. The estimated mortality rate was 0.020 birds per setting/hauling, and 0.163 birds per day. The intensity of interactions was largely explained by the distribution of the fishing effort. GLM analysis indicated that seasonality (parameter likelihood > 0.988) and the incidence of discards (parameter likelihood > 0.996) were the strongest factors explaining the occurrence of interactions by most of the species. Conservative estimations of total mortality in the trawl fleet under investigation exceed 3,000 albatrosses. The implementation of a strategic discard management might reduce significantly the number of seabird mortalities from collisions with warp cables, or improve the effectiveness of other mitigation methods that can be used in parallel. Urgent implementation of mitigation measures is needed in this fleet to decrease the large albatross mortality along the Patagonian Shelf.