Search

Histologic examination of the nonnative green mussel, Perna viridis, and the native scorched mussel, Brachidantes exustus, at three locations in Tampa Bay, Florida, indicated that cycles of gametogenesis and spawning were similar between species. Major spawning periods occurred in the spring (April) in conjunction with increasing water temperature and the fall (September to November) as the water temperature was declining. Over the summer, both species appeared to undergo varying levels of redevelopment, partial spawning and resorption of oocytes. Gametogenesis was limited over the winter. Differences between populations in levels of gametogenic activity and the timing of the fall spawn were most likely related to differences in salinity and available food at the three sites. A higher fecundity (caused by the faster growth rate and greater maximum size of P. viridis) may result in displacement of native bivalves in Tampa Bay, including B. exustus. [ABSTRACT FROM AUTHOR]

Juvenile oyster disease (JOD) has had severe impacts on eastern oyster, Crassostrea virginica,culture in the northeastern United States in recent years. JOD mortalities in Maine have resulted in juvenile crop losses exceeding 90%. Previous research has demonstrated an inverse relationship between oyster size and JOD-induced mortality; thus the use of genetically selected broodstock along with specific management options may help manage JOD-related mortality. The goals of this project were to determine the size specificity and temporal and spatial variability of JOD outbreaks with respect to several lines selected for fast growth. Two lines (including within line unselected controls) having undergone two generations of selection for faster growth, along with an unselected wild line, were deployed during the 1994–1995 growing seasons at two sites in the Damariscotta River, ME, an estuary historically impacted by JOD. Periodic monitoring of size (shell height and live weight) and mortality of replicate cohorts was conducted to track oyster growth and incidence of JOD-induced mortalities. Due to the asynchrony of spat deployment between the cohorts, differences among lines were not feasible to evaluate, but within two lines (Flowers G2and Milford G2), selected sublines both outgrew the within line controls and had lower rates of JOD-induced mortality. The reduced mortality in the selected sublines presumably resulted from their faster growth and hardiness thus enabling the cohort to reach a refuge size/age sooner and reduce its susceptibility to JOD.

Incorporation of 14C into lipid, carbohydrate, and protein fractions of digestive gland, adductor muscle, and ovary body components of the bay scallop, Argopecten irradians concentricus(Say), varied seasonally in conjunction with oogenesis. Resting stage scallops (June-July) were characterized by net radiocarbon losses in ovary fractions. Nutrient storage during this period was indicated by relatively small radiocarbon losses in digestive gland fractions that were equaled by gains in adductor muscle carbohydrate and protein fractions. During the period of oocyte growth (August-October) 14C losses in digestive gland and adductor muscle fractions always exceeded progressive gains in the ovary. Increased carbon turnover (catabolism) of digestive gland lipid and adductor muscle carbohydrate fractions accompanied decreased turnover (anabolism) of ovary lipid, indicating the utilization of these reserves for the production of ova. After spawning (November), 14C was lost from all body component fractions, indicating a state of negative energy balance and generally poor physiological condition. These results directly reinforce the pattern of energy storage and utilization in A. irradians concentricusindicated by previous studies on growth, biochemical composition, and substrate catabolism.