Science Serving Maryland's Coasts

Eloy Martinez-Rivera, University of Puerto Rico, Humacao

Class Year: 

Project Title: 

Assessing habitat quality in Chesapeake Bay: Application of RNA:DNA indices to blue crab (Callinectes sapidus)


Blue crab (Callinectes sapidus) is common to a wide range of estuarine habitats along the eastern seaboard of the Americas. Despite its broad distribution, the abundances of crabs in several regions including in the Chesapeake Bay have declined due to explotation and habitat alteration. Resource managers have tried a range of tools and techniques to assess the status of the blue crabs in the Chesapeake Bay. Patterns of habitat-specific production are currently unknown. One technique for measuring habitat-specific production that has proven successful with fishes and other crustaceans is to measure short-term growth using the ratio of RNA:DNA in sample tissues of an organism. This technique has not been validated for blue crab. The objective of this project was to test experimentally the potential of this technique to assess habitat quality and growth of the blue crab in the bay. Crabs from a wide range of sizes were exposed to three food regimes for 7 days. After 7 d, muscle samples from three legs of each crab were extracted for nucleic acid analysis. Nucleic acids concentration in crabs was strongly affected by crab size, tissue type and ration. However, no significant relations were found between factors. As the exploratory nature of this project, other areas should have to be explored to improve this technique for later use in blue crab stock management.