Position data loggers and logbooks as tools in fisheries research: results of a pilot study and some recommendations

Global positioning system (GPS) -based position data loggers were used in a 4-month pilot study on micro-scale mapping of Nephrops trawler effort in the Clyde Sea area, west Scotland. Position data loggers supplied unbiased, accurate fishing effort data at a scale hitherto unrecorded. Vessels in the survey carried out between 13 and 59 tows per month ( mean =35.3±2.6 S . E . ) with a mean duration of 3 h and 30 min. Fishing effort was expressed as the number of times a trawl passed through a 0.25′ × 0.25′ pixel . The area covered by fished pixels was 1208 km2, with 29% of these being fished on one occasion during the 4-month period. The maximum number of times a trawl passed through an individual pixel was 27. Trawl location data were combined with daily landings obtained from a complementary confidential logbook scheme using geographic information system (GIS) to produce maps of fishing effort, cumulative landings and landings per unit effort (LPUE). The potential for such studies is discussed and recommendations are given for position data logger deployment and logbook schemes.