Spatial structure of the resource of Pandalus borealis and some implications for trawl survey

• Published in: Fisheries research 2002-11, Vol.58 (2), p.171-183
• Main Authors: Kingsley, M.C.S, Carlsson, D.M, Kanneworff, P, Pennington, M
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Fundamental and applied biological sciences. Psychology; Marine; Pandalus borealis; Spatial structure; Survey accuracy; Tow duration; Trawl survey
• ISSN: 0165-7836; 1872-6763
• DOI: 10.1016/S0165-7836(01)00388-5

Spatial structure of fisheries resources affects the design of resource surveys. A trawl survey is a component of the assessment of the stock of northern shrimp Pandalus borealis in West Greenland waters. In connection with optimising tow durations, the spatial structure of the resource has been studied by carrying out experimental surveys consisting of contiguous tows along transects. Shorter tow durations of 15 and 30 min have been introduced to the survey. Experimental survey fishing in 1997 on isobathic transects comprising six to seven 1 h tows showed in most cases only small differences in catch rates between contiguous tows. In 2000, on transects comprising separated pairs of contiguous 15 min tows, there was high variation along the transects, high correlation between the catches at contiguous tows and small short-range variation in resource density. In the assessment survey, overall, shorter tows appeared to make catches that were not more variable than those of longer tows, and using shorter tows had little effect on the precision of the estimate of total biomass from the survey. However, the trawl was estimated to fish for the equivalent of 2.8 min more than the recorded tow duration, predicting that biomass estimates from surveys based on short tows would be biased upwards relative to long-tow surveys.