We present results of an international collaboration to survey American lobster Homarus americanus Milne-Edwards, 1837 nurseries in Atlantic Canada and the northeast United States from 2007 to 2009 under a standardized protocol involving two sampling methods, diver-based suction sampling and passive collectors. We surveyed young-of-year and older juveniles at 191 sampling sites over 39 sampling areas considerably expanding the known depth range and geographic limits of benthic recruitment. Young-of-year densities were strongly correlated in space with the abundance of older juveniles, signifying consistently strong settlement in the Gulf of Maine, lower Bay of Fundy, southwestern Nova Scotia and southern Gulf of St. Lawrence, and relatively weak settlement in southern New England, eastern coastal Nova Scotia and Newfoundland, a pattern consistent with commercial lobster harvests. Passive collectors elucidated bathymetric patterns of young-of-year recruitment in oceanographically contrasting regions. Although we observed young-of-year lobsters as deep as 80 m, they were most abundant above the thermocline in summer-stratified regions, such as the western Gulf of Maine and southern New England, and depth-wise differences were less extreme in thermally mixed waters of the eastern Gulf of MaineÁFundy region, a finding consistent with previous observations that postlarvae concentrate above the thermocline. Between the two samplers, we detected no sampling bias for young-of-year lobsters, although collectors may slightly underrepresent older juveniles entering from the surrounding sea bed. Finally, we found that interactions between juvenile lobsters and suspected predators or competitors in collectors, such as crabs and fishes, are weak and unlikely to bias collector results.

Wahle, R. A., Bergeron, C. E., Chute, A. S., Jacobson, L. D., and Chen, Y. 2008. The Northwest Atlantic deep-sea red crab (Chaceon quinquedens) population before and after the onset of harvesting. – ICES Journal of Marine Science, 65: 862–872. The population structure of deep-sea red crab (Chaceon quinquedens) in a nearly unexploited state is compared with its condition three decades later after more than a decade of sustained harvesting. Our study is based on a camera and net trawl survey conducted in 1974, which we repeated between 2003 and 2005 on the southern New England shelf break. Although the overall biomass of red crabs was estimated to be higher than in 1974, the abundance of large males, which are targeted by the fishery, was considerably lower. In particular, the biomass of large males (≥114 mm carapace width), considered in 1974 to be marketable, declined by 42%. Declines were most evident at depths and regions most accessible to the fishing fleet based in southern New England. With the change in fishery selectivity towards smaller male crabs, the abundance of currently harvestable crabs is about equal to 1974 levels. No declines were observed in the biomass of female and smaller male crabs not targeted by the fishery. Indeed, the abundance of juveniles appears considerably higher than in 1974. Perhaps, adverse effects on reproduction attributable to a reduction in the numbers of large males may be a consequence of fishing, but fishery impacts and productivity are difficult to assess because key biological information is lacking.

Passive collectors are used widely in postlarval settlement and recruitment monitoring of spiny lobsters and crabs, but they have only been used in a limited way with clawed lobsters. For nearly two decades, diver-based suction sampling has served to monitor spatial-temporal patterns of American lobster (Homarus americanus) postlarval settlement and early juvenile abundance in shallow near-shore nurseries. Collectors could reveal settlement patterns in zones beyond the practical limits of diving. In 2005, we launched a fisherscientist collaboration to evaluate the performance of passive collectors designed to extend the reach of sampling, and to be deployable from a vessel equipped with a standard pot-hauler. Building on previous designs, our collectors comprised wire mesh trays lined with fine screening on the floor and walls and filled with cobble to simulate natural nursery habitat. Results indicate that no newly settled lobsters were lost during the retrieval process, and densities of young-of-year lobsters found in the collectors were similar to those in directly adjacent natural cobble habitat sampled by divers with suction samplers. The collectors also proved to be effective samplers of juvenile fish and crabs, suggesting a possibility for wider application. This success bodes well for expanded deployment of cobble collectors to broaden our understanding of the recruitment processes of lobster and other cobble-dwelling fauna along the coast of New England, United States and Atlantic Canada.