Seabird mortality associated to ice trawlers in the Patagonian Shelf: effect of discards in the occurrence of interactions with fishing gear

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

ANIMAL CONSERVATION

WILEY-BLACKWELL PUBLISHING, INC

Año: 2011 vol. 14 p. 131 - 139

1367-9430

This study investigated the level of seabird mortality caused by the domestic trawlfleet (freshies) for hake (among other less important targets) operating in watersoff central Patagonia (37–481S), analyzing the effect of environmental andoperational variability on the level of seabird interactions. With a total of 135vessels, the fleet is one of the largest in Argentina. Specifically tasked seabirdobservers were placed onboard trawlers during the summer and winter seasons ofthe years 2006 and 2007. The type and number of seabird interactions (i.e. contactswith fishing gear) were recorded during shooting and hauling operations, covering72 days of observation and 328 trawls. Black-browed albatrosses, white-chinnedpetrels Procellaria aequinoctialis, southern giant petrels Marconectes giganteus andsouthern royal albatrosses Diomedea epomophora were the most abundant speciesinteracting with trawlers. Confirmed mortalities of black-browed and southernroyal albatrosses were the result of collisions and entanglement with the warpcable while birds were scavenging. The estimated total mortality rate was 0.017birds h1 and 0.105 birds per vessel per day. The intensity of interactions (in termsof the number of contacts per unit time) was largely explained by the distributionof the fishing effort. Seasonality and the incidence of discards were the strongestfactors explaining the occurrence of seabird interactions. The total annualmortality in the trawl fleet under investigation was roughly estimated to be fromseveral hundred to over a thousand albatrosses. However, these figures should beconsidered preliminary due to the limited spatial and temporal coverage of dataand the fact that estimations were based on a low number of observed mortalities.The implementation of a strategic discard management may significantly reducethe number of seabird mortalities from collisions with warp cables or improve theeffectiveness of other complementary mitigation methods. Urgent implementationof mitigation measures is needed in this fleet to reduce the mortality of albatrossesand petrels along the Patagonian shelf.