Publication Abstract

Spatial and temporal patterns in North Sea fishing effort

Spatial and temporal patterns in North Sea fishing effort

S. Jennings, K.J. Warr, S.P.R. Greenstreet and A.J. Cotter

1. An understanding of spatial and temporal patterns in fishing effort is a prerequisite for investigating the effects of fishing in the marine environment. We describe patterns in demersal (bottom) fishing effort by trawlers and seine netters in the North Sea.

2. Total international demersal fishing effort (vessels largely > 12 m) was relatively constant in the period 1990-1995. In 1994, total effort was 2.5 million h y-1 of which 51 % and 44 was due to beam and otter trawling repectively.

3. Spatial analyses indicate that the proportion of beam trawling effort increases from north to south while the proportion of otter trawling and seine net effort increases from south to north.

4. Plots of annual fishing effort by ICES statistical rectangle (211 boxes of 0.5° latitude by 1° longitude) indicate that the majority of fishing effort is concentrated in relatively few rectangles.

5. Mean annual total trawling effort (1990-1995) exceeded 40 000 h in 4 % of rectangles. Effort was less than 2 000 h in 29% of rectangles and 10 000 h in 66% of rectangles.

6. Most seine netting is conducted by Scottish vessels in the northern and central North Sea. Seine netting effort has declined between 1991 and 1994 to 125 000 h year-'.

7. The validity of reported trawling effort in the southern and central North Sea was tested by comparing official effort reports with calculated trawler sightings-per-unit-effort (SPUE) from fisheries enforcement boats and overflights.

8. Reported effort provides a good general picture of the areas where fishing effort is concentrated. However, the large scale resolution of reported effort (by rectangle) provides a poor indication of the specificity of fishing grounds. SPUE data suggest that parts of rectangles are heavily fished while others are unfished.

9. If fishing effort data are needed to examine the wider ecological effects of fishing then the resolution at which data are collected will have to be increased. Satellite tagging of vessels may help to acheive this.

Reference:

S. Jennings, K.J. Warr, S.P.R. Greenstreet and A.J. Cotter, 2000. Spatial and temporal patterns in North Sea fishing effort, pp3-14, In: Effects of fishing on non-target species and habitats: biological conservation and socio-economic issues (ed. M. J. Kaiser and S. J. de Groot). Oxford: Blackwell Science

S. Jennings*, K.J. Warr*, S.P.R. Greenstreet and A.J. Cotter*

pp3-14, In: Effects of fishing on non-target species and habitats: biological conservation and socio-economic issues (ed. M. J. Kaiser and S. J. de Groot). Oxford: Blackwell Science