No abstract

Egg production, larval survival, and migration of large benthic stages are considered to be possible bottlenecks to fishery yields for the American lobster Homarus americanus in the eastern Northumberland Strait, southern Gulf of St. Lawrence. Egg production, measured as eggs per trap haul and stage I larval production, was high compared with that of surrounding areas with greater fishery yield. The only area that could have supplied larvae by drift supported average egg production. Low levels of postlarvae developed from this average to high egg production, implicating low larval survival as the proximal cause of low fishery yield. A scarcity of small lobsters in the catch over several decades also indicated that recruitment was low and that the fishable stock was supported by immigration. Because of this spatially variable relationship between egg production and fishery yield, we recommend setting management targets specific to an area.

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.

No abstract

In the southern Gulf of St. Lawrence, there were concerns that freezing seized American lobster (Homarus americanus) to preserve evidence for the court could potentially reduce the carapace length, and compromise the enforcement of a fishery regulation limiting minimal legal size. Tests were performed on 30 soft-and 30 hardshell American lobsters to study the potential for shrinkage when lobsters were cooked and/or frozen. It was found that carapace length reduction was related to the carapace condition. Except for freezing of soft-shell lobsters, all treatments produced a statistically detectable reduction in carapace length. However, the average carapace length reduction ranged from only 0.1-0.5 mm, the highest increase being for hard-shell lobsters after cooking, freezing then thawing (t-test, P-value=1.8×10-10). Out of the 60 animals studied, none had a carapace length reduction over 0.7 mm, while four had a carapace length increase. Although a carapace length reduction could be detected statistically, this should not cause problems in enforcing a minimum legal size.