Abstract. — Otoliths, scales, dor- 

 sal spines, and pectoral-fin rays 

 were compared to ascertain the 

 best hardpart for determining the 

 age of weakfish, Cynoscion regalis. 

 Each showed concentric marks, 

 which could be interpreted as an- 

 nuli. Sectioned otoliths, however, 

 consistently showed the clearest 

 marks, had 100% agreement be- 

 tween and within readers, and 

 were validated by the marginal in- 

 crement method for ages 1-5. This 

 validated method of ageing weak- 

 fish was then compared with the 

 traditionally used scale method. 

 The scale method was less precise, 

 as demonstrated by lower percent 

 agreement, and generally assigned 

 younger ages for fish older than age 

 6 (as determined by otoliths). Con- 

 sequently, mean sizes at age based 

 on scales showed no clear signs of 

 an asymptote, whereas those based 

 on otoliths did. Otolith annuli 

 formed in April and May, whereas 

 scale annulus formation was more 

 variable, ranging from April to Au- 

 gust. This extended time of annu- 

 lus formation made scales poorly 

 suited for back calculation. 



A comparison of a validated 

 otolith method to age weakfish, 

 Cynoscion regalis, with the 

 traditional scale method 



Susan K. Lowerre-Barbieri 



Virginia Institute of Marine Science, College of William and Mary 

 Gloucester Point. Virginia 23062 



Present address University of Georgia Marine Institute 



Sapelo Island. Georgia 31327 



Mark E. Chittenden Jr. 



Virginia Institute of Marine Science, College of William and Mary 

 Gloucester Point. Virginia 23062 



Cynthia M. Jones 



Applied Marine Research Laboratory, Old Dominion University 

 Norfolk. Virginia 23529 



The weakfish, Cynoscion regalis, is 

 a recreationally and commercially 

 important sciaenid found from east- 

 ern Florida to Massachusetts, and 

 is most abundant from North Caro- 

 lina to New York (Mercer, 1985). 

 Believed to be resident year-round 

 in the Carolinas, they are found far- 

 ther north only seasonally (Bigelow 

 and Schroeder, 1953). In the spring, 

 weakfish migrate northward and 

 inshore to estuarine feeding and 

 spawning grounds; this pattern is 

 reversed in the fall (Wilk, 1979). 

 Most fish are believed to overwinter 

 off North Carolina (Pearson, 1932). 

 Weakfish are found in Chesapeake 

 Bay, roughly from April through No- 

 vember (Pearson, 1941; Massmann et 

 al., 1958), where they support one of 

 the region's most important fisheries 

 (Rothschild et al., 1981). 



Weakfish age and growth studies 

 have been based almost exclusively 

 on scales (Taylor, 1916; Nesbit, 

 1954; Perlmutter et al., 1956; Mass- 

 mann, 1963a; Merriner, 1973; Shep- 



herd and Grimes, 1983). However, 

 problems with this method have 

 been reported: 1 ) small fish may not 

 lay down a first annulus on scales 

 (Welsh and Breder, 1923), 2) older 

 fish have closely spaced annuli that 

 are difficult to interpret (Taylor, 

 1916; Shepherd, 1988), 3) annuli 

 form over a long time period, April- 

 August, and scales are difficult to 

 interpret during annulus formation 

 (Nesbit, 1954; Massmann, 1963b), 

 4) the time annuli form varies an- 

 nually and regionally ( Perlmutter et 

 al. , 1956 ), and 5 ) checks (false annuli ) 

 and regenerated scales are common 

 (Merriner, 1973). The scale method 

 of ageing weakfish also has not been 

 conclusively validated by current 

 standards (Beamish and McFarlane, 

 1983; Brothers, 1983). Perlmutter et 

 al. (1956) and Shepherd and Grimes 

 (1983) both tried to validate annuli 

 on scales by the marginal increment 

 method, however they used pooled 

 age data and did not report the age 

 range. 



Manuscript accepted 8 November 199.3. 

 Fishery Bulletin 92:555-568 ( 1994). 



Contribution 1826 from the College of William and Mary. School of Marine Science, Vir- 

 ginia Institute of Marine Science, Gloucester Point. Virginia 23062. 



555 



