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Use of Non-Native Macroalgal Habitat by Hatchery-Reared and Wild Blue Crab Juveniles
Mahalak, Kristin
Mahalak, Kristin
Abstract
Seagrass beds are considered the preferred nursery habitat for juvenile blue crabs, Callinectes sapidus, increasing both survival and growth in early juvenile stages. Degradation of this structured nursery habitat and a drastic decline in spawning stock, due to natural and fishing mortality, has many scientists concerned about the Chesapeake Bay's blue crab population. This study aimed to determine whether non-native macroalgae, Gracilaria spp., may function as an alternative nursery habitat for juvenile crabs and whether Gracilaria spp. may help to increase release success of hatchery-reared cohorts as part of stock enhancement efforts. In this study, ~28,000 hatchery-reared blue crab juveniles (mean size 7.15mm carapace width-CW) were released near the mouth of the York River in an unvegetated mud cove enhanced with ~3600 L of Gracilaria spp. Sampling was conducted in two areas of the cove using a basket apparatus. The number and size (carapace width-CW) of crabs were measured during each sampling. The crabs collected during sampling were identified as hatchery-reared or wild using genetic analysis. Crab density at each site suggests Gracilaria in the mud cove had a carrying capacity of ~4-8 crabs m-2. Genetic analysis determined that some hatchery-reared crabs remained within the mud cove for the entire 43 day study period. Mean carapace width for the hatchery-reared cohort increased from 7.15mm (SE+/- 0.0581) to 26.6mm (SE+/- 1.93). In addition, settlement of wild juvenile recruits in Gracilaria was observed in early August. These findings suggest that the non-native macroalgae, Gracilaria spp., serves as an alternative nursery habitat for blue crab juveniles and release of hatchery-reared juveniles into habitats containing Gracilaria may help to increase post-release success.
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Thesis is part of Honors ETD pilot project, 2008-2013. Migrated from Dspace in 2016.
Date
2008-05-06
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Keywords
Blue crab nursery habitat, Gracilaria, Stock enhancement, Genetic tracking
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Biology