Hostetter and Munroe: Age, growth, and reproduction of Tautoga onms 



57 



Reproduction and growth 



Maximum GSI values calculated in the present study 

 indicate that spawning commences in late April and 

 continues to early June for tautog taken at inshore 

 sites in Virginia. Finding fish in spawning condition in 

 Virginia in late April is somewhat earlier than reported 

 previously for tautog from more northern inshore ar- 

 eas, and undoubtedly reflects the warmer tempera- 

 tures in coastal waters of Virginia in early spring. 

 Based on laboratory (Olla et al. 1980) and field obser- 

 vations (Chenoweth 1963, Olla et al. 1974, Eklund & 

 Targett 1990, this study) of ripe fish, spawning in tau- 

 tog generally commences when water temperatures 

 reach 11° C or above. In Massachusetts, tautog spawn 

 from mid-May to early August (Stolgitis 1970), while 

 peak spawning was reported to occur from late May 

 to early June in tautog collected within shallow wa- 

 ters of Narragansett Bay, Rhode Island (Chenoweth 

 1963). Near Long Island, tautog eggs have been 

 collected in the plankton from May through early 

 September (Perlmutter 1939, Wheatland 1956, 

 Austin 1973); however, the effective spawning season 

 may be somewhat shorter since few larvae were col- 

 lected when water temperatures exceeded 21.0° C (Aus- 

 tin 1973). 



Highest GSI values for tautog from Virginia occurred 

 over a longer seasonal period than reported for tautog 

 collected inside Narragansett Bay (Chenoweth 1963). 

 We attribute this to the fact that we collected fish over 

 a broad range of sites spread over a much wider geo- 

 graphic area, including many deepwater offshore sta- 

 tions. On hardbottom areas 22-37 km offshore of Mary- 



MONTH 



Figure 1 1 



Relationship demonstrating co-occurrence of time of annulus 

 formation (mean marginal increment, MMI) and peak spawn- 

 ing season Igonadosomatic index, GSI) for Tautoga onitis from 

 coastal waters of Virginia. 



land and northern Virginia, Eklund & Targett (1990) 

 noted significantly higher GSI values for female tau- 

 tog (24-50 cm TL) from May through the beginning of 

 August, with spawning taking place during summer 

 (May-July). This time schedule is similar to what we 

 observed in tautog collected at offshore habitats in 

 southern Virginia, and, as was pointed out by Eklund 

 and Targett, this seasonality also corresponds with 

 the occurrence of tautog eggs and yolksac larvae in 

 Mid-Atlantic Bight plankton samples (Colton et al. 

 1979). 



Annulus formation in tautog collected in Virginia 

 occurs in May or June commensurate with gonadal 

 maturation (Fig. 11). Formation of an annulus on the 

 opercle concomitant with spawning was noted also by 

 Cooper (1967) for tautog from Rhode Island. Decline 

 in physiological condition during gonadal development, 

 presumably representing disruption in somatic growth, 

 was observed in tautog by Chenoweth (1963). Such 

 disruption in somatic growth could contribute to the 

 slow-growth phase observed on opercles during this 

 time. However, annulus formation occurs in sexually 

 immature fish during this same time, indicating that 

 inherent physiological factors other than those associ- 

 ated with spawning also influence annulus formation 

 in these fish. 



Annulus formation in tautog collected in Rhode Is- 

 land occurred in late or middle May at the start of the 

 spawning season (Cooper 1967). In Virginia, we ob- 

 served that annuli formed over a longer time-period 

 (May-July). Warmer water temperatures earlier in 

 spring in Virginia may cause smaller fish to form an- 

 nuli slightly earlier than larger fish. This growth pat- 

 tern would agree with observations that younger and 

 smaller fish are more active than larger fish at lower 

 water temperatures (Olla et al. 1974, 1980). Also, since 

 these smaller fish do not usually participate in spawn- 

 ing activities, all growth during spring would be re- 

 flected as increases in somatic rather than gonadal 

 growth. 



Variation in the estimate of time of annulus forma- 

 tion may have resulted from analyzing data indepen- 

 dent of year of collection. Interannual differences in 

 environmental conditions would be expected when these 

 data are combined. Also, we sampled tautog from vari- 

 ous geographically separated inshore and offshore lo- 

 cations, and small-scale variations in time of annulus 

 formation may be expected in fish collected from these 

 diverse areas. One other source of variation could re- 

 sult from annulus formation during the spawning pe- 

 riod. Since spawning commences earlier and is appar- 

 ently more protracted for fish in southern areas of the 

 species range, the period for annulus formation would 

 also be extended in tautog occurring in Virginia com- 

 pared with those occurring further north. 



