Abstract
The blue crab Callinectes sapidus is an ecologically and economically important component of marine and estuarine ecosystems of the western Atlantic and Gulf of Mexico. Cur- rent stock assessments lack a clear understanding of the age structure of blue crab populations in Florida (USA). Blue crabs and other crustaceans are especially difficult to age because of the com- plex nature of their discrete, rather than continuous, growth patterns. Chesapeake Bay re - searchers developed a method of aging blue crabs by assaying the aging pigment lipofuscin extracted from eyestalk nerve tissue. Here we investigated the usefulness of that method in deter- mining the age of blue crabs inhabiting Florida waters. Assays of a wild-caught, young-of-the- year cohort that was pond-raised revealed a negative linear trend in lipofuscin indices over an 18 mo culture period. Assays of a tank-raised cohort of captive-bred crabs of known age also showed no relationship between the lipofuscin index and age over an 11 mo period. These results suggest that lipofuscin assays, as used in the Chesapeake Bay populations, are not useful in deter- mining the age of blue crabs in Florida waters. Further study is warranted to determine how the procedure might be modified for Florida blue crab populations.
Highlights
Determination of age structure is essential to fishery stock assessments (Beamish & McFarlane 1983)
In the most recent stock assessment of Florida’s blue crab Callinectes sapidus fishery (Murphy et al 2007), it was noted that data on population age structure was lacking
Lipofuscin indices were determined for 2 populations of blue crabs in order to investigate whether the methodology of aging crabs using lipofuscin extraction and normalization to protein could be applied to blue crabs inhabiting Florida waters
Summary
Determination of age structure is essential to fishery stock assessments (Beamish & McFarlane 1983). In the most recent stock assessment of Florida’s blue crab Callinectes sapidus fishery (Murphy et al 2007), it was noted that data on population age structure was lacking. Length-frequency cohort analysis, widely used in finfish fishery management, cannot be used to accurately determine the age of crustaceans (Puckett et al 2008) because of growth rate variability, protracted spawning seasons, the inability to account for biological interactions, discrete growth, and the effects of environmental changes on ecdysis (Hartnoll 2001). The complex process of ecdysis, resulting in the growth of the blue crab, is greatly influenced by salinity and temperature (Steele & Bert 1994). Temporal and spatial differences in temperature and salinity affect growth rates of individuals of Publisher: Inter-Research · www.int-res.com
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