Patricia M. Biesiot

CULTURE OF COBIA (RACHYCENTRON-CANADUM) - CRYOPRESERVATION OF SPERM AND INDUCED SPAWNING

Abstract Studies toward the development of cobia ( Rachycentron canadum ) aquaculture were initiated. Methods of cryopreserving cobia sperm were compared and sperm motility was assessed after longterm frozen storage. Sperm stored in 10% dimethyl sulfoxide, 3 mM glucose, and 10% raw chicken egg yolk showed approximately 100% motility upon thawing after more than 1 year of storage at −80°C. Sperm motility declined after about 60 min at room temperature, but approximately 100% motility could be restored by addition of a few drops of 5 mM theophylline. Ripe, wild-caught female cobia were held in recirculating seawater systems and ovulation was induced by injection of human chorionic gonadotropin at a concentration of 275 IU/kg of body weight. Fertilization was attempted using the cryopreserved sperm. Although fertilization did not occur, we are optimistic that cobia aquaculture is feasible.

Biochemical composition of the deep-sea red crab Chaceon quinquedens (Geryonidae): Organic reserves of developing embryos and adults

Deep-sea red crabs Chaceon quinquedens (Smith) were collected in traps at depths of 860 and 1043 m in the northern Gulf of Mexico. Ovigerous crabs were maintained in the laboratory and the developing embryos were sampled every 2 wk until hatching. Proximate analysis (lipid, protein, carbohydrate, and ash) of embryos was performed to determine patterns and rates of organic reserve utilization during embryogenesis. Midgut gland, gonads, and clutch (as appropriate) of adult crabs (males, non-ovigerous females and ovigerous females) were analyzed for the same components as the embryos. Red crab embryos exhibited different patterns of yolk deposition and subsequent depletion of yolk components during embryogenesis. There was a range of lipid to protein (L:P) ratios among the different clutches examined, indicating plasticity in the relative proportions of lipid and protein yolk. The energy used for embryogenesis was estimated by converting the amounts of lipid, protein and carbohydrate in the embryos to their caloric equivalents; final values, taken from 9 mo-old embryos whose siblings were hatching as zoeae, were subtracted from the initial values of sibling embryos sampled at the time of collection (2 to 3 mo old). The amount of energy consumed during embryogenesis in the laboratory was relatively constant (0.12 to 0.13 cal egg-1). There was considerable variability among the concentrations of organic reserves in the midgut gland of adult crabs and in the ovaries of females. Variations in midgut gland L:P ratios and ovaries were related to the reproductive status of the females, but there were no trends related to depth of capture.

Factors Influencing Refuge Occupation by Stone Crab Menippe adina Juveniles in Mississippi Sound

Abstract A greater understanding of population dynamics is essential in the management of any species. The Western Gulf stone crab, Menippe adina, is taken as incidental by-catch in the blue crab, Callinectes sapidus, fishery in Mississippi. However, there is a lack of information on the ecology of M. adina in estuaries of the northern Gulf of Mexico. We know that M. adina is associated with hard-bottom habitats such as rock-rubble jetties and oyster reefs and that this habitat is sparse in Mississippi Sound, which mainly consists of soft-bottom habitat. Many studies have demonstrated that habitat complexity is important to several benthic crustaceans because it provides a matrix of different sized refuges that organisms can use to escape from predation. The importance and availability of refugia varies throughout the life history of organisms because of the increase in size of an organism as it grows. Refuge limitation acting on a specific size class may create a demographic bottleneck thereby limiting the production of a population through mortality, migration, or stunting of the affected size class. We tested this refuge limitation bottleneck hypothesis in juvenile stone crabs by supplementing an existing oyster reef with four different sizes of polyvinyl chloride (PVC) pipe. We found that lack of refuge affected both population size structure and density of large juvenile stone crabs on the reef. We also found that competition for available refuges may occur among M. adina and two other xanthid crab species, Eurypanopeus depressus and Panopeus simpsoni. We examined the diet of oyster toadfish, Opsanus beta, in Mississippi Sound and found that the three xanthid crabs comprised a significantly large portion of oyster toadfish diet. Predation by O. beta emphasized the importance of the availability of suitable refugia for the xanthids.

Fecundity and Egg Diameter of Primiparous and Multiparous Blue Crab Callinectes Sapidus (Brachyura: Portunidae) in Mississippi Waters

ABSTRACT Blue crabs Callinectes sapidus Rathbun, 1896 support large commercial and recreational fisheries along the Atlantic coast and in the Gulf of Mexico (GOM). Female blue crabs are traditionally believed to produce one to six broods in their lifetime. However, recent evidence has shown that females have the ability to spawn up to eight broods in a single spawning season, with as many as 18 broods over their lifespan. In this study, fecundity and egg diameter were examined by brood class (primiparous, multiparous) in the spring and summer/fall. Mean carapace width of females was significantly different between brood class and season, with the largest females in the spring. There was a positive relationship between fecundity and carapace width. Although primiparous spring females were the most fecund (3.2 ± 1.5 million eggs), no statistically significant differences in fecundity by brood class and season were found. Loss of eggs occurred during embryonic development; primiparous females lost ∼0.9 million eggs whereas multiparous females lost ∼0.1 million. Egg diameter and carapace width of the female were positively correlated. There was no difference in egg diameter between brood classes, but eggs were 9.9% larger in diameter during the spring than summer/fall. There was an inverse relationship between fecundity and egg diameter. Seasonality appeared to play an important role in the reproductive life history of blue crabs in the northern GOM. Larger crabs and larger eggs in the spring may be related to quality and quantity of available food and temperature conditions for optimal growth.