Date Thesis Awarded

5-2008

Document Type

Honors Thesis

Degree Name

Bachelors of Science (BS)

Department

Biology

Advisor

Paul D. Heideman

Committee Member

Rochelle Seitz

Committee Member

Romuald Lipcius

Committee Member

Randolph M. Chambers

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.

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

Comments

Thesis is part of Honors ETD pilot project, 2008-2013. Migrated from Dspace in 2016.

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