Hostetter and Munroe Age. growth, and reproduction of Tautoga onitis 



47 



Figure 1 



Collection localities (marked by stars) in lower Chesapeake Bay and Virginia coastal 

 waters where Tautoga onitis were collected for age, growth, length, and weight param- 

 eters. Stars indicate general collecting areas, with most indicating more than one collec- 

 tion per area. Arrows indicate locations of the Chesapeake Bay Bridge Tunnel (CBBT) 

 and of previous studies on tautog from Rhode Island (by Cooper, see Citations) and from 

 New York and northern New Jersey (by Briggs & Olla and co-workers, see Citations). 



Chesapeake Bay and offshore hardbottom areas (CBBT, 

 wrecks, artificial reefs) of coastal Virginia (Fig. 1). 



Each specimen was measured to the nearest 1 mm 

 for standard length (SL) and total length (TL), and 

 weighed (WT) to the nearest 5g. Length data from 

 both sexes were combined to generate a regression 

 equation for SL on TL (TL = 4.78+1.20 SL). High cor- 

 relation (r 2 =0.98) between these measurements 

 prompted the use of TL in analyses, since this was the 

 more easily and reliably obtained measurement. 



For each fish, an initial determination of sex was 

 made by examining several external characters that 

 have been previously shown to be dimorphic (Cooper 

 1967, Olla & Samet 1977). Adult males usually have a 

 blunt forehead with a more massive mandible, com- 



pared with that of adult females 

 which have a less massive man- 

 dible and more anteriorly-ta- 

 pered profile of the head. Larger 

 males are typically gray and have 

 distinctly visible (especially un- 

 derwater) white markings on the 

 caudal, pelvic, and dorsal fins, 

 and also on the chin region. Fe- 

 males (all sizes) and smaller 

 males tend to have a mottled 

 brown coloration without white 

 markings on the fins and chin 

 region. 



After initial determination of 

 sex based on external character- 

 istics, gonads were then excised, 

 staged macroscopically for matu- 

 rity state, and weighed (gonad 

 weight = GW) to the nearest 

 O.lg (gonad weights were not 

 available for all fish). Maturity 

 stages were defined as fol- 

 lows: Immature — gonads un- 

 differentiated; Mature — gonads 

 obviously differentiated; Ripe — 

 gonads enlarged, containing 

 sperm or ova; Running ripe — 

 sperm or ova expressed when 

 slight pressure applied to abdo- 

 men; Spent — large, flaccid go- 

 nads, often bloody in appearance, 

 with no obvious signs of sperm 

 or ova upon dissection. A go- 

 nadosomatic index (GSI) for fe- 

 males for all years combined was 

 calculated using the formula 

 GSI=GW x 100/WT. 



Scales, saccular otoliths, and 

 opercles were collected and com- 

 pared to determine the best method for ageing tautog. 

 Whole unsectioned opercles (Fig. 2) were prepared fol- 

 lowing procedures used by Cooper (1967). The articu- 

 lar apical center, as defined by Le Cren (1947), 

 McConnell (1952), Bardach (1955), and Cooper (1967), 

 is the center of the high ridge projecting from the me- 

 dial surface of the opercle. Opercular radius (OR), de- 

 fined as the distance from the articular apex center to 

 the midpoint of the posterior margin of the opercle, 

 was measured with dial calipers to 0.1mm (Fig. 2). 

 Similarly, measurements (to 0.1mm) were made along 

 this axis to each annulus to determine annual growth 

 increments. An annulus was defined as the sharp tran- 

 sition from a translucent (hyaline) to an opaque zone 

 on the opercle. Only discernible annuli continuous from 



