Postcapture Survival and Future Reproductive Potential of Ovigerous Blue Crabs Callinectes sapidus Caught in the Central North Carolina Pot Fishery

Abstract

Harvest restrictions by sex or reproductive status are used to protect many spawning stocks. In most U.S. states, fishery regulations for blue crabs Callinectes sapidus 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.

Mitigating unaccounted fishing mortality from gillnets and traps

“…; Darnell et al . ). Some studies (13) were carried out in both the field and laboratory (Simonson and Hochberg ; Bellchambers et al .…”

“…The majority of studies examining the fate of discards from gillnets and traps have followed this approach, although some monitoring periods have ranged between 3 and 20 days, up to a maximum of 321 days (Darnell et al . ).…”

“…; Darnell et al . ). Almost exclusively, such injuries have been reported and quantified for crustaceans discarded from traps ( n = 8), and only once from gillnets (Uhlmann et al .…”

“…So-called press experiments, where stressors were applied repeatedly, were rarely carried out (Eno et al 2001;Tallack 2007;Coleman et al 2013). Most (n = 75) of the reviewed studies were field based, and often direct assessments in a conventional scenario (or as close as possible), using local gears and techniques to catch organisms and then monitoring components of their unaccounted fishing mortality (Cole et al 2003;Tallack 2007;Broadhurst et al 2009;Darnell et al 2010). Some studies (13) were carried out in both the field and laboratory (Simonson and Hochberg 1986;Bellchambers et al 2005;Hatfield et al 2011).…”

Effects of pot fishing on the physical condition of snow crab (Chionoecetes opilio) and southern Tanner crab (Chionoecetes bairdi)

“…To date, many studies have examined the effects of stressors, such as trauma from the hauling of pots, air exposure, and adverse temperatures, that are associated with capture, handling, and discarding of crabs (van Tamelen, 2005;Tallack, 2007;Stoner, 2009;Darnell et al, 2010). Decompression due to fast transport through the water column is one of the stressors that affect crabs during fi shing with pots.…”