Morphological conditioning of a hatchery-raised invertebrate, Callinectes sapidus, to improve field survivorship after release

Do Hatchery-Reared Blue Crabs Differ from Wild Crabs, and Does it Matter?

“…Juvenile topshell (Trochus niloticus) possess spines that are thought to provide effective protection from predation by allowing them to physically lock into crevices (Purcell, 2002). We found that crabs maintained in the laboratory (both cultured and wild individuals kept for 30 days) had shorter spines than wild crabs (Davis et al, 2004(Davis et al, , 2005b (Figure 1). After time in the field, however, hatchery-reared crabs had spines of similar length to wild crabs, resulting from either individual spine increases (suggesting spine length is a plastic trait) or differential mortality of short-spined crabs (Davis et al, 2005b).…”

“…We found that crabs maintained in the laboratory (both cultured and wild individuals kept for 30 days) had shorter spines than wild crabs (Davis et al, 2004(Davis et al, , 2005b (Figure 1). After time in the field, however, hatchery-reared crabs had spines of similar length to wild crabs, resulting from either individual spine increases (suggesting spine length is a plastic trait) or differential mortality of short-spined crabs (Davis et al, 2005b). In addition, in one experiment, cultured crabs maintained in aquaria and exposed for 27 days visually and chemically to striped bass predators increased their spine length relative to control crabs that were not exposed to predators, and to crabs that were exposed to predatory adult blue crabs.…”

“…These differences, however, faded after cultured crabs were exposed to sediment for 1-2 days in the laboratory and 5 days in the field (Davis et al, 2005b). Hatchery-reared and wild crabs showed similar ability to use endocrine control of chromatophores to match their color to the background, often within 1-2 hr.…”

“…However, in another experiment, changes in spine length in response to predators were not apparent. Some tethering experiments with unconditioned hatchery-reared crabs indicated that spines do have an important effect on survival: crabs that survived had significantly longer spines than those that did not (Davis et al, 2005b). Also, crabs conditioned to have larger spines had higher survivorship than unconditioned crabs in two field tethering experiments and one laboratory experiment (Davis et al, 2005b).…”

“…Some tethering experiments with unconditioned hatchery-reared crabs indicated that spines do have an important effect on survival: crabs that survived had significantly longer spines than those that did not (Davis et al, 2005b). Also, crabs conditioned to have larger spines had higher survivorship than unconditioned crabs in two field tethering experiments and one laboratory experiment (Davis et al, 2005b). While survivorship of hatchery-reared crabs was lower than wild crabs in some cases, overall survivorship of tagged cultured and wild crabs did not differ in the field.…”