Fisheries ecology of common wolffish, Anarhichas lupus, in the North Sea

• Main Author: Liao, Yih-Yia
• Format: Thesis
• Language: unknown
• Published: 1999
• Subjects: Arctic; North Atlantic; Northeast Atlantic
• Online Access: http://etheses.dur.ac.uk/4403/; http://etheses.dur.ac.uk/4403/1/4403_1923.pdf

The common wolffish (Anarhichas lupus), a benthivorous species, is widely dispersed, although not abundant in the North Sea north of 54ºN latitude. Despite being widely distributed in sub Arctic and cold North Atlantic waters, little is known of the ecology of this species in the North Sea. This thesis aimed to provide ecological information for this species at the southern limit of its range in the Northeast Atlantic. North Sea common wolffish are regarded as sedentary in habit and mainly inhabited depths ranging from 60 m to 150 m. The bottom temperatures where this species were found in the North Sea ranged between 3ºC and 12ºC. The common wolffish is a by-catch species for the North Sea bottom trawl fishery. The long-term catch data and CPUE (catch per unit effort) indicated that the stock abundance of North Sea common wolfish has been decreasing over the last decades. However, it is suggested from VPA (virtual population analysis) and Yield-per-recruit analysis, that the North Sea common wolfish stock is still in a safe condition but has been overexploited. The means of total mortality (Z), natural mortality (M) and fishing mortality (F) of this species for 1996-1998 were 0.47, 0.17 and 0.30, respectively. Both resting metabolic rate (RMR) and maximum metabolic rate (MMR) were low for this species. RMR and MMR were measured for six adult common wolffish (mean weight, 1.39kg) at 5ºC and 10ºC. At 5ºC the mean RMR± SE was 12.18 ± 1.6 mgO(_2),kg(^-1)h(^-1), and mean MMR ± SE was 70.65 ± 7.63 mgO(_2)kg(^-1)h(^-1). At 10ºC the mean RMR±SE was 25.43 ±1.31 mgO(_2) kg (^-1)h(^-1), and mean MMR ± SE was 113.84 ± 16.26 mgO(_2) kg(^-1)h(^-1). Absolute metabolic scope was 53% greater at 10ºC than at 5ºC.The main food for common wolffish in the North Sea were Decapoda comprising 39 % of the overall diet by occurrence, with hermit crabs (Paguridae) being the dominant species. Other important dietary components were Bivalvia (20 %) and Gastropoda (12 %). Sea urchins (Echinidae), which are important prey of common wolffish ...