White 



et al ; Reproductive seasonality, fecundity, and spawning frequency of Tautoga onitis 



435 



ment, or modes of oocjrtes, except for 

 hydrated oocytes (0.95 to 1.25 mm) — a 

 finding that indicates asynchronous 

 oocyte development. The presence of 

 primary growth through advanced 

 yolked oocytes, as well as oocytes in 

 FOM and POFs in histologic sections 

 of fully developed and partially spent 

 ovaries (Fig. 2, C and F), is evidence 

 that tautog exhibit a multiple spawn- 

 ing pattern. 



Ovarian cycle 



( 1 ) Immature 



1) 



Sexual Maturity 



f7^ (7) Rest 



ing 



(2) Developing 



(6) Spent/ 

 Regressing 



Egg maturation in tautog is a complex 

 process comprising both seasonal and 

 annual components. This complex pat- 

 tern of multiple spawning exhibited by 

 an inner spawning cycle (made up of 

 hydration, ovulation, spawning, and 

 redevelopment) within the annual 

 ovarian developmental cycle, is sum- 

 marized for tautog in Virginia in Figure 

 6. In the spring, fully developed ovaries 

 contain primary growth to advanced 

 yolked oocytes, but lack POFs. Fish enter the spawning cycle 

 by hydration and ovulation of the first batch of oocytes. After 

 the first spawning event, partially spent^redeveloping ova- 

 ries contain fresh POFs (indicating recent spawning during 

 the previous 24 hours) and another batch of oocytes in FOM 

 in preparation for the next spawning event. Thereafter, the 

 inner spawning cycle is repeated throughout the spawning 

 season. Histological examination of hydrated ovaries during 

 the spawning season revealed the co-occurrence of hydrated 

 oocytes (indicating an imminent spawn) and degenerating 

 POFs, suggesting that some tautog are capable of repeating 

 the inner spawning cycle on a daily basis. At the end of the 

 spawning season, ovaries progress to the spent-regressing 

 stage, where, through the process of oocyte atresia, the 

 remaining stock of yolked oocytes are resorbed before the 

 ovary enters the resting stage. 



Batch fecundity 



Batch fecundity was determined for 29 female tautog rang- 

 ing in total length from 260 to 520 mm, total weight 475 to 

 3,500 g, and ages 3-9 (Fig. 7). Although there was a high 

 degree of variation in batch fecundity between individual 

 fish, significant relationships were found between batch 

 fecundity and fish length, weight, and age. Batch fecundity 

 was more closely related to total length and total weight 

 than to age. Batch fecundity (BF) increased significantly 

 with total length (ANOVA, n=29, F=16.92, P<0.0005, 

 power=0.97), following the regression equation (Fig. 7A) 



f'^:^ (3a) Partially spent/ 

 Redeveloping 



(3) Fully 

 Developed 



FOM 



Ovulation 



(5) Running Ripe 



(4) Hydrated 



^g 



Figure 6 



Annual and spawning season cycles of ovarian development in tautog. FOM = final 

 oocyte maturation. 



BF = 56,066 Ln(TW) - 322,091 



=0.501. 



Batch fecundity also increased significantly with age 

 (ANOVA, n=29, F=10.22, P<0.004, power=0.88), following 

 the regression equation ( Fig. 7C ) 



BF = 15,73 1(AG£) - 20,599 



[r2=0.271. 



BF = 425.76(rL)- 84,534 



|r2=0.39]. 



Batch fecundity increased significantly with total weight 

 (ANOVA, n=29, F=16.80, P<0.0005, power=0.99), the 

 regression equation being (Fig. 7B) 



Tautog relative fecundity (BF/GW) did not increase sig- 

 nificantly with fish length (ANOVA, n=29, F=1.98, P=0.17) 

 or age (ANOVA, n=29, F=1.72, P=0.20), but there was a 

 significant increase in relative fecundity with total fish 

 weight (ANOVA, n=29, P=4.46, P=0.044). 



Spawning frequency 



Histological examination of 169 tautog collected from 7 

 April 1995 to 15 June 1995 revealed some variation in the 

 abundance of three reproductive states that were indica- 

 tive of imminent or recent spawning. Forty-four percent of 

 female tautog had HOs, 32'y^ had fresh POFs without any 

 HOs, and 84'2 of females collected had 1-day-old POFs 

 (Table 4). Tautog spawning frequency was calculated as 

 1.2 days based on the percentage of fish with 1-day-old 

 POFs following the methods of Hunter and Goldberg 

 (1980). Number of spawnings per female tautog in 1995 

 was calculated as the spawning season (70 days) divided 

 by spawning frequency (1.2 days/spawning), yielding 58 

 spawnings per female. 



Individual tautog in natural habitats were capable of 

 spawning daily after entering the spawning season. Evi- 

 dence of daily spawning was provided by the rapid ovarian 

 development observed in histological sections: 1) 70 fish 

 with HOs and degenerating POFs: 2) 90 fish with both 

 fresh and degenerating POFs: and 3) partially spent/ 



