Deepwater longline survey on the continental slopes of Porcupine Bank, Rockall Bank and Hatton Bank

Abstract

A deepwater survey programme has been operated since 1993 by the Marine Institute (MI), in the deep waters of the Rockall Trough and Porcupine Bank. The first leg of the present survey took place over a period of 12 days in August 2000 on the Western slope of the Porcupine Bank and the western slopes of Rockall Bank and Hatton Bank. The second leg took place on the slopes and shelves of the Porcupine Bank. Fishing was carried out in depths between 150 and 1,800 meters. The primary objective of the survey was to obtain biological samples of chondricthyan and teleost fish, for contaminant analysis of fish by the MI chemistry section and for food technology analysis at the Teagase National Food Centre. The survey was carried out on the commercial long-liner "An Capall Bán," using commercial deepwater autoline gear. In total 26 species of chondricthyan and 24 species of teleost fish were taken. Among the most abundant species in the catch were birdbeak dogfish (22%), leafscale gulpershark (14%), Portuguese dogfish (8%), tusk (17%) and mora (8%). Over the entire survey, discarding was estimated at 43% of the total catch. The main species discarded were bird beak dogfish and greater lantern shark. Catch per unit effort showed that highest abundances were found in the northwestern slope of the Porcupine Bank at 600 - 700 metres and in the western slopes of Rockall Bank and Hatton Bank at 1,000 to 1,200 metres depths.