Variability in trap catches for an American lobster, Homarus americanus, spring fishery

Abstract

At-sea sampling is a common approach used by fsheries scientists to assess changes in fshed populations. Traditional sampling programmes focus on short intensive sampling periods by fisheries personnel, although there has been a move to increase temporal sampling frequency within a fshing season by using harvesters. To determine the suitability of these two options, we compared the precision of estimates obtained for the American lobster (Homarus americanus) fshery in the southern Gulf of St. Lawrence, Canada. The sampling variance estimation for the mean catch-per-unit-effort (CPUE) was based on a three-stage sampling design with days as the primary unit, and buoy and trap as secondary and third stage units, respectively. Using the estimated variance components to predict and compare the variance of the mean CPUE for different at-sea sampling designs, we show that it would be more effcient to sample a few traps (at least 3) every day for the entire fshing season than the traditional at-sea sampling of the entire fshing gear twice or three times in a season by scientifc personnel. Designing a harvester-based at-sea sampling programme could be an effcient approach for reducing costs while gathering essential fshery data, improving dialogue between the industry and scientists, and increasing harvesters' participation in managing the resource. © The Royal Society of New Zealand 2009.