Seabird mortality associated with ice trawlers in the patagonian shelf: effect of discards on the occurrence of interactions with fishing gear

FAVERO, M., BLANCO, G., GARCÍA, G., COPELLO, S., SECO PON, J., FRERE, E., QUINTANA, F., YORIO, P., RABUFFETTI, 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 trawl fleet (“freshies”) for hake (among other less important targets) operating in waters off central Patagonia (37-48°S), analyzing the effect of environmental and operational variability on the level of seabird 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 over 300 operations. Black-browed albatrosses, White-chinned Petrels, Southern Giant Petrels and Southern Royal Albatrosses were the most abundant 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 total mortality rate was 0.017 birds per hour-1 and 0.139 birds per vessel per day. The intensity of interactions (in terms of number of contacts per unit time) was largely explained by the distribution of the fishing effort. Seasonality and the incidence of discards were the strongest factors explaining the occurrence of seabird interactions. Total annual mortality in the trawl fleet under investigation was estimated to be between 1,200 and 2,800 albatrosses. The implementation of a strategic discard management might significantly reduce the number of seabird mortalities from collisions with warp cables, or improve the effectiveness of other complementary mitigation methods. Urgent implementation of mitigation measures is needed in this fleet to reduce the mortality of albatrosses and petrels along the Patagonian Shelf.