Validation and Application of Lipofuscin-Based Age Determination for Chesapeake Bay Blue Crabs Callinectes sapidus

—Quantifying lipofuscin (LF), a metabolic byproduct that accumulates in postmitotic cells, serves as one of the principal approaches for aging crustaceans, but the accuracy of this method remains an important issue. Here, we quantified LF accumulation as a function of chronological age and temperature (degree-days) in an economically important crustacean, the blue crab Callinectes sapidus, to test the accuracy of LF-based age estimates and determine the age-specific partial recruitment of juveniles to summer and fall commercial fisheries. Three known-age juvenile cohorts (63–83 d) were reared in ponds up to 1.8 years of age. Field collections were conducted in two subestuaries of Chesapeake Bay from June to October during 2003 and 2004. Lipofuscin accumulation oscillated seasonally in known-age cohorts. Significant (log e transformed) LF accumulation occurred at average intervals of 2.5 months, with the exception of winter months (mean temperature1⁄4 88C). Seasonalized von Bertalanffy functions accurately depicted age-specific LF accumulation but were cohort specific. The relationship between LF and temperature degree-day (TD day) was similar among cohorts and genders, and a single LF–TD day model was applied to field-collected crabs. The mean age prediction error of this model was 2.0 months. Lipofuscin-based age composition of field collections indicated that the peeler–soft crab and hard crab fisheries were predominately composed of recruits less than age 1.5 from August to October. The consequences of this short (approximately annual) generation time is that recruitment and landings will be responsive to environmental factors affecting growth and the annual variations in egg production, settlement, and postsettlement survival. Age-dependent assessments are a cornerstone in fisheries management, and careful attention is warranted in developing age determination procedures (Beamish and McFarlane 1983; Campana 2001). Crustaceans present unique challenges for management owing to their lack of traditional aging structures (i.e., otoliths, scales, and fin spines) and the periodic loss of their only hard parts through molting (Hartnoll 2001; Smith and Addison 2003). Typically, length frequency modal analysis has been used as an alternative to direct aging (Jennings et al. 2001), but the effectiveness of resolving length modes is often compromised by gear selectivity, protracted spawning periods, and seasonal growth dynamics (Hilborn and Walters 1992). Beginning with Ettershank’s (1983) work on Antarctic krill Euphausia superba, quantifying lipofuscin (LF) has become an alternative approach for age determination in crustaceans. Lipofuscin occurs as fluorescent granular pigments in postmitotic tissue (i.e., neural tissue), and is believed to be the product of free radical-mediated lipid peroxidation and the accumulation of nondegradable oxidized macromolecules in lysosomes (Hill and Womersley 1993; Brunk and Terman 2002; Chowdhury et al. 2004). The amount of LF increases with age and senescence, often showing a positive relationship with chronological age (Brunk and Terman 2002). Accordingly, several studies have quantified LF to estimate age, growth, and longevity for diverse taxa, including Antarctic krill (Ettershank 1983), lobster (Wahle et al. 1996; Sheehy et al. 1998, 1999), shrimp (Vila et al. 2000; Bluhm and Brey 2001; Kodama et al. 2005), crayfish (Sheehy 1992; Belchier et al. 1998), swimming crab Callinectes sapidus (Ju et al. 2001, 2003), amphipod Waldeckia obesa (Bluhm et al. 2001), fish (Vernet et al. 1988), and clam Eurhomalea exalbida (Lomovasky et al. 2002). Several methods of quantifying LF have been * Corresponding author: [email protected] Received December 19, 2007; accepted April 20, 2008 Published online November 20, 2008 Y:/f/fitr/3b2/@fitr13706/fitr-137-06-05.3d Thursday, 13 November 2008 12:55 pm Allen Press, Inc. Page 1637 1637 Transactions of the American Fisheries Society 137:1637–1649, 2008 Copyright by the American Fisheries Society 2008 DOI: 10.1577/T07-278.1 [Article]