Benthic Habitats and the Effects of Fishing

Symposium Abstract: Spatial and Temporal Patterns in Trawling Activity in the Canadian Atlantic and Pacific

D. W. Kulka and D. A. Pitcher

doi: https://doi.org/10.47886/9781888569605.ch125

GIS was used to spatially analyze trawling in Canadian Atlantic and Pacific waters as part of a program to assess the effect of trawling on benthic habitats. Data for 1980-2000 (Atlantic) and 1994- 2000 (Pacific) in the form of geo-referenced fishing set locations were used to spatially describe effort location. The results are a series of maps depicting the spatial distribution of trawling intensity. Temporal changes and patterns in trawling intensity are described. In the Atlantic, trawl grounds are patchy and complex covering between 8 and 38% of the shelf in any year although actual trawled bottom area is much smaller. Spatial patterns of trawling changed dramatically over the time sequence analyzed but locations of high intensity trawling were similar from one year to the next. The spatial patterns were most stable during the 1980’s while the greatest changes occurred during the early 1990’s. There were numerous persistent areas of trawling spread mainly along the shelf edge and between the banks. A substantial portion (shallow and shoreward) of the shelf was consistently unfished. In the Pacific, the trawl locations were more consistent but the observed timeframe was much shorter (1994-2000). Trawl grounds comprised a string of partially joined patches along the shelf edge off Vancouver Island, three patches within the southern Queen Charlotte Sound, south and east of Queen Charlotte Island at deeper locations and on the shelf edge north and west of Queen Charlotte Island. The results, a first step in quantifying trawl effects, provide precise information on extent and intensity of bottom disturbance due to trawling.