Results of 1997 Longline Survey of the Rockall Trough

Abstract

The present survey took place over a period of 12 days in August 1997 along the eastern slope of Rockall Trough between 53 and 58ºN including the Northern slope of the Porcupine Bank. Fishing was carried out in six separate areas, in depths between 300 and 2,925 meters. The primary objective of the survey was to obtain samples of chondricthyan and teleost fish for the Marine Institute (MI) deepwater research programme, for contaminant analysis of fish by the MI chemistry section and for food technology analysis at the Teagasc National Food Centre. The survey was carried out on the Norwegian commercial long-liner "Skarheim," using commercial deep-water autoline gear. In total over 70,000 hooks were set during the trip and on average 80% of these were baited. In total 20 species of chondricthyan and 18 species of teleost fish were taken. Among the most abundant species in the catch were leafscale gulper shark Centrophorus squamosus (36%), bird beak dogfish Deania calcea (21 %), Portuguese dogfish Centrascyflium coefofepis (13%), tusk, Brosme brosme (11%) and mora, Mora mora (6%). Over the entire survey, discarding was estimated as 30% of the total catch. The main species discarded were bird beak dogfish and greater lantern shark Etmopterus princeps. Catch per 1,000 hooks showed that highest abundances were found at 600 - 1,100 metres throughout the whole fishing area. Three settings were made at depths between 2,000 and 3,000 meters. These shots gave valuable information about depth distribution of different species and also brought up species that have never been recorded in the Rockall Trough before.