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Paired male and female Tanner crabs, Chionoecetes bairdi, in a premating embrace were collected from shallow-(< 13 m) and deepwater (> 150 m) benthic environments by scuba and submersible, respectively. Pubescent females were restricted to shallow water; males grasping them were significantly smaller than those grasping oldshell multiparous females with eyed embryos in a large, deepwater mating aggregation. Males appeared to select for large sizes among pubescent females, but not among multiparous females, which were limited in size range. Grasping males were 82.6–166.2 mm carapace width (CW) [Formula: see text] and represented at least three different width frequency modes; all were larger than their female partners. Paired females represented two modes with mean CW ≈ 77 mm for pubescent and 99 mm for multiparous individuals. Only one to three of 176 male graspers were small-clawed (morphometrically immature), a statistically nonsignificant proportion; several others had partially regenerated claws but were otherwise morphometrically mature, as evidenced by the second right merus. These data support the hypothesis that the attainment of morphometric maturity, evidenced by a relatively large chela to body size ratio, is a prerequisite for functional maturity, the ability to mate competitively in wild populations.

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The incidence of epizootic shell disease in American lobster Homarus americanus has increased in southern New England, USA, in the last decade, but few longitudinal studies have followed the disease progress in individual lobsters or demonstrated direct effects on mortality or growth. Diseased lobsters were held in the laboratory for 1 yr, and the progression of disease and its effects on molting, mortality, and growth were monitored. A quantitative disease index (QDI) was developed by measuring disease lesions in digital images of the carapace and expressing the result as a proportion of shell area. Some lobsters died due to high temperatures, but at least 13 of 55 lobsters (24%) died as a direct result of disease-related problems, mostly during molting, and there was a significant relationship between mortality and high values of the QDI. Lobsters that molted successfully were free of disease lesions, but many had exoskeletal deformities. There was no relationship between pre-molt size and disease severity, but molt increment was significantly correlated with premolt carapace length (CL) and negatively correlated with QDI. However, percentage growth was negatively correlated with QDI, but not with pre-molt CL. These significant lethal and sublethal effects of epizootic shell disease should be considered in lobster management.

ABSTRACT-Swimming behavior was observed and substrate preference determined for glaucothoe stage postlarvae of the red klng crab Paralithodes camtschaticus In the laboratory. One hundred 1 d old glaucothoe were placed into each of 3 replicate 10 1 aquana, each containing a choice of 3 substrates: sand, gravel, or synthetic fiber mesh. Glaucothoe began settling on the first day, and <10% remained swimming after Day 6. Glaucothoe showed a significant preference for the structurally con~plex mesh substrate. Occupancy of mesh increased from 49% on Day 2 to 75% by metamorphosis to the first crab (Cl) instar, with a mean of 62 * 11 %. Glaucothoe rejected sand, and only 1 % were observed on it. Settlement was also tested in aquaria with only sand, gravel or mesh substrates. Glaucothoe in gravel-or ~~e s h -o n l y aq~iai-ia s~lttled rapldly. whereas 40% of glaucothoe in the sand-onlv aquarium continued swimming until metamorphosis to C1 instar In addition, mean time-to-metamorphos~s in the sand-only aquarium (17.6 d) was significantly greater than in other experimental aquarla (16 8 d). Glaucothoe in the sand-only aquarium exhibited marked diurnal swimming behavior; 66 % were swimming at 14:OO h (vs a maximum of 12 % in other aquaria), but only 5 % (vs l %) were swimming at 02:OO h. Daytime swimming probably allows glaucothoe to avoid nocturnal predators while searching for preferred substrates, i.e. those which are structurally complex, can be easily grasped, and provide a high degree of interstitial space.

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Alteration and degradation of benthic structure by fishing gear can impede efforts to manage fish stock sustainably. Although the impacts of mobile gear are well known, effects of passive gear (e.g. fish traps) upon structure have been little studied. We modified commercial traps for American lobster Homarus americanus and black sea bass Centropristis striata by attaching GoPro® cameras to ascertain the degree and nature of impacts to seafloor habitats. Customized traps were included within a line of 20 traps, deployed and retrieved according to standard commercial fishing practice. Less than 5% of traps landed directly on bedforms when deployed. However, during retrieval traps dragged along the ocean floor, increasing trap–habitat contact rate to 50%, and causing traps to collide with corals, bryozoans, and other epifauna. Drag time of traps depended on the position in the trap line. Experimentally extending the trap line reduced drag time during retrieval for traps near the distal end of the line. Our results show that impacts of commercial trap fishing can be substantial during trap retrieval, and that the impact depends on their location on a trap line. Fishing practices should be developed that minimize effects of trap retrieval on structural benthic habitat.