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



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Table 1 



Description of macroscopic and microscopic gonad stages (modified from Lowerre-Barbieri et al.,1996) for female tautog. Mac- 

 roscopic criteria refer to whole fresh ovaries. Gonad stages 4, 5, and 3a comprise the inner spawning cycle. FOM = final oocyte 

 maturation. GSI = gonadosomatic index. GVBD = germinal vesicle breakdown. POF = postovulatory follicle. MA = macrophage 

 aggregate. 



Gonad stage 



Macroscopic criteria 



Microscopic criteria 



1 Immature 



2 Developing 



3 Fully 

 developed 



4 Hydrated 



5 Running ripe 



3a 



Partially 



spent/ 



redeveloping 



Spent/ 

 regressing 



7 Resting 



Ovaries very small, tubular in shape, white to light 

 pink in color; no oocytes visible (mean GSI=0.50) 



Ovaries small to medium, tubular shape, dark yel- 

 low to light orange in color; yolked (opaque) oocytes 

 begin to appear (mean GSI=2.25 ) 



Ovaries medium to large, appear slightly grainy, 

 pale mustard in color; yolked oocytes are abundant 

 (mean GSI=3.25 ) 



Ovaries large to very large, pink to orange in color; 

 firm, yolked oocytes interspersed with large trans- 

 parent (hydrated) oocytes (mean GSI=11.74 ) 



Ovaries large to very large; few transparent oocytes 

 in ovarian tissue, transparent oocytes have been 

 ovulated into expanded lumen, and are easily ex- 

 truded when gonad is excised (mean GSI=10.12) 



Ovaries somewhat flaccid, large, slightly more pink 

 than in hydrated stage; lumen has collapsed, occa- 

 sionally a few remnant hydrated oocytes extruded 

 from excised ovary (mean GSI=8.84); similar to 

 stage 3. 



Ovaries flaccid, small to medium, red to purple; 

 some tissue devoid of yolked oocytes at anterior 

 end of ovary, yolked oocytes visible but less abun- 

 dant (mean GSI=1. 37) 



Ovaries small, purple-opaque to maroon in color; 

 few or no yolked (opaque) oocytes visible (mean 

 GSI=1.50) 



Oogonia and primary growth oocytes present; high pro- 

 portion of connective tissue, no atresia or MAs, ovarian 

 membrane thinner than in resting stage. 



Primary growth, cortical alveoli, and some partially 

 yolked oocytes present. 



Primary growth to advanced yolked oocytes present; no 

 FOM stages, POFs, or remnant HOs. 



Primary growth to germinal vesicle migration (GVMl 

 and hydrated oocytes present, hydrated oocytes are 

 unovulated; 1-day POFs may be present. 



Primary growth through GVM, and ovulated hydrated 

 oocytes and fresh POFs present; lumen usually seen as 

 separation of ovigerous folds. 



Primary growth through GVBD oocytes present, no 

 unovulated hydrated oocytes, few remnant ovulated 

 hydrated oocytes; lumen collapsed, POFs abundant. 



Primary growth through advanced yolked oocytes pres- 

 ent; major atresia of all stages except primary growth 

 oocytes. 



Primary growth and cortical alveoli oocytes present, 

 occasional atretic oocytes; MAs abundant, more oogonia 

 tissue, less connective tissue, and thicker ovarian mem- 

 brane than in immature stage. 



in Table 1, and shown in Figure 2, A-H. Percent agreement 

 between macroscopic and microscopic female gonad stages 

 was calculated to evaluate the accuracy of macroscopic 

 staging (used in all previous studies of tautog reproduc- 

 tive biology). Microscopic stages were assumed to be more 

 accurate because histologic examination provides evidence 

 of differences in cellular development. 



Chi-square analysis (n=489 fish) was used to test for 

 significant deviations from an expected 1:1 sex ratio for all 

 fish. Deviations from a 1:1 sex ratio among 100-mm length 

 intervals were also analyzed by chi-square to determine if 

 size or age had a significant effect on sex ratio. 



Length and age at maturity were analyzed for fish col- 

 lected from April to rnid-June to reduce the possibility of 

 classifying resting, mature fish as immature. Females were 

 considered mature if classified into microscopic stages 2-7 



(Table 1). Males were considered mature if spermatoc3ftes 

 or spermatozoa were present in histological sections. 

 Length at maturity was based on 110 females and 79 

 males (150-350 mm TL). A logistic regression curve was 

 fitted to the data, to estimate length at 50% maturity (Lgg). 

 Age at maturity was based on 135 females and 104 males 

 (ages 1-6). 



To determine the annual spawning season, a gonadoso- 

 matic index (GSl=(gonad weight I somatic weight) x 100) 

 was calculated by using somatic weight [S'W=TW-GW) 

 for each sex. A more precise estimate of tautog spawning 

 season was determined from microscopic gonad stages. The 

 spawning season was defined by the first and last day that 

 female tautog. were collected with ovaries staged as either 

 hydrated, running ripe, or partially spent/redeveloping. 

 Spawning locations were detected by the presence of hy- 



