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

Abstract

At-sea sampling is a common approach used by fisheries scientists to assess changes in fished 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 fishing 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) fishery 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 efficient to sample a few traps (at least 3) every day for the entire fishing season than the traditional at-sea sampling of the entire fishing gear twice or three times in a season by scientific personnel. Designing a harvester-based at-sea sampling programme could be an efficient approach for reducing costs while gathering essential fishery data, improving dialogue between the industry and scientists, and increasing harvesters' participation in managing the resource.

A fisher-based, catch-sampling program for a large-scale, benthic molluscan fishery

“…In contrast, the evidence from our simulations indicated that measuring the entire catch from 10% of fishing days would not provide representative data on the length structure of the commercial catch in this fishery. This is because this sampling program is unlikely to capture the heterogeneity in length structures among different abalone populations, as the catch is sampled from only a small sub-set of the actual number of fishing days (Pennington et al, 2002;Comeau et al, 2009). This finding is consistent with previous studies that demonstrate increased precision and accuracy through sampling more primary units (Pennington and Volstad, 1994;McGarvey and Pennington, 2001).…”

“…Collection of these fishery-dependent data is typically far less expensive than obtaining fishery-independent information, such as survey measures of abundance (Prince and Hilborn, 1998;Kimura and Somerton, 2006;Kristensen et al, 2006;McGarvey et al, 2008). Cost is an important consideration, particularly where licence or access fees are levied against fishers to recover expenses associated with the management of their fishery, and has led to more adaptive measures being employed to collect relevant data (Hart et al, 2008;Prince et al, 2008;Comeau et al, 2009).…”

Catch variation among traps in an American lobster (Homarus americanus) trawl

“…Among those factors, different types of fishing strategy such as trap and trawl design are clearly relevant (Comeau et al, 2009). A better understanding of these factors will minimize the risk associated with population estimates from catch data directly from the commercial fishery (Smith and Tremblay, 2003).…”

“…While the effects of biotic and abiotic factors have been well documented, little research has examined the effects of fishing strategies on catch rates (Miller and Rodger, 1996;Comeau et al, 2009), particularly trap and trawl design. Trap design can vary by size, material, and location of entrances, while trawl design (a trawl is a group of traps connected on a line to a surface buoy; Comeau et al (2009)) includes the number and spacing of traps and the presence of extra buoys (Smith and Tremblay, 2003).…”

“…Trap design can vary by size, material, and location of entrances, while trawl design (a trawl is a group of traps connected on a line to a surface buoy; Comeau et al (2009)) includes the number and spacing of traps and the presence of extra buoys (Smith and Tremblay, 2003). When relying on catch data from the commercial fishery for population estimates, it is important to understand the variability in catch rates that may occur if different fishing strategies, such as trap and trawl design, are used (Comeau et al, 2009). Furthermore, in relation to trawl design, commercial fishermen often report that the first trap in the trawl (the one attached to the surface buoy) catches fewer lobsters compared to the other traps.…”