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Abstract--Effective assessment and management of migratory species require an understanding of stock boundaries and habitat use during critical life history periods. The blue crab (Callinectes sapidus) is considered a primarily [...]

ABSTRACT Understanding how growth rates are influenced by environmental conditions is important for proper management of commercially harvested species, especially under current and predicted future conditions of global climate change. [...]

ABSTRACT A high-salinity embayment located near Beaufort, North Carolina was surveyed to create a bathymetric profile of the main basin. To examine population dynamics and habitat use within the embayment, [...]

Fiddler crabs are highly sexually dimorphic. Males possess one small (minor) feeding claw and one greatly enlarged (major) claw; females possess two small claws. The major claw is used to attract mates and for burrow defense, but it is costly for the male to possess. We tested the hypothesis that the major claw also functions as a thermoregulatory structure, a function that would allow males to spend a greater amount of time at the surface, foraging and attracting potential mates. Fiddler crabs Uca panacea were exposed to a source of radiant heat and body temperatures were monitored. Four groups of crabs were tested: intact males, males with the minor claw removed, males with the major claw removed, and females. The body temperatures of males without the major claw increased more rapidly and reached higher values than did those of males with the major claw intact, but the results from these animals were similar to those of females. These results support the hypothesized thermoregulatory function of the major claw. The major claw may function as a heat sink, transferring heat away from the body and dissipating it into the air. Enhanced thermoregulatory ability provided by the major claw may partially ameliorate the energetic costs of possessing such a large claw. [ABSTRACT FROM AUTHOR]

Harvest restrictions by sex or reproductive status are used to protect many spawning stocks. In most U.S. states, fishery regulations for blue crabs require release of ovigerous crabs. Ovigerous crabs caught in pots become stressed by capture and physically damage the egg mass and remove eggs. We conducted a survey to assess the extent of egg mass damage in pot-caught crabs as well as crabs caught by hand and not subjected to pot stress. Egg mass damage was more prevalent in pot-caught crabs (>45% during all months) than in crabs caught by hand (<6% during all months). We investigated the postcapture survival, reproductive output, and larval viability of crabs with varying amounts of egg mass damage by collecting ovigerous crabs from the pot fishery and confining them in the field for the duration of their lifetimes. Over 80% of the crabs survived to release the clutch present at capture, and crabs produced up to six clutches of eggs. Of 156 clutches produced in confinement, only 1 was damaged. Crabs confined individually and fed do not experience the stress that causes egg mass damage in pots. The lipid content of early-stage eggs (77.0 ± 1.3% [mean ± SE]), larval carapace width (269.0 ± 3.34 μm), and larval survival time without food (3.0 ± 0.11 d) were similar for all clutches and levels of egg mass damage. Clutch volume decreased by approximately 20% with each subsequent clutch, and the percentage of embryos developing normally decreased from 97 ± 0.6% for clutch 1 to 79 ± 10.8% for clutch 5. Immediate release of ovigerous crabs could be a viable management strategy, but it would have severe economic consequences for fishermen in high-salinity areas. Area closures, combined with subsidies for crabbers during critical times, may be the most viable management strategy until crab populations recover from current diminished levels. [ABSTRACT FROM AUTHOR]

The amphipod Talorchestia longicornis is active on the substrate surface during the night and inactive in its burrows during the day. The underlying circadian rhythm in activity can be entrained by the light : dark cycle. This study considered other aspects of entrainment, such as: whether the compound eyes or extraocular photoreceptors are used to detect entrainment cues, which visual pigment mediates the entrainment process, whether entrainment can also occur in response to diel temperature cycles and whether when presented with conflicting entrainment cues, the light : dark or temperature cycle dominates for entrainment. Entrainment was determined by monitoring temporal changes in surface activity using a video system, and assessed as the number of animals active on a sand substrate at 0.5 h intervals. The compound eyes and not extraocular photoreceptors are used for entrainment to the light : dark cycle. Although T. longicornis has two visual pigments with absorption maxima near 420 and 520 nm, entrainment occurred only by light that simulated the 520 nm absorbing pigment, perhaps because its absorption is matched to the spectrum of ambient light at twilight. The rhythm is also entrained by a diel temperature cycle. If amphipods are simultaneously exposed to a temperature and light : dark cycles phased differently, they entrain to the temperature cycle. These results suggest that for a burrowing amphipod, diel temperature cycles may be a more reliable indicator of environmental conditions than light cycles. [ABSTRACT FROM AUTHOR]