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Fishery Bulletin 88(3), 1990 



size, but not size-specific ovary weight, were related 

 to seawater temperature 60-90 days before spawning. 

 Again, fecundity increased with increasing tempera- 

 ture while egg size decreased. 



Results from this study demonstrate that water 

 temperatures during the latter stages of gamete 

 maturation (48-51 days prior to spawning) and during 

 embiyo and larval development affect the size and com- 

 position of winter flounder larvae produced. Further, 

 the interaction between acclimation temperature of 

 adults and incubation temperature of embryos and lar- 

 vae also appears to have a strong effect on size and 

 composition of larvae. While the number of oocytes 

 entering vitellogenesis is probably determined earlier 

 in the reproductive cycle (Brown 1957, Dunn 1970, 

 Tyler and Dunn 1976, Burton and Idler 1984), several 

 important functions occur during the latter stages of 

 gamete development, including further deposition of 

 yolk and final meiotic division. 



Our data on size and chemical composition of winter 

 flounder at hatching and first feeding suggest a more 

 complex relation between water temperature and lar- 

 val size than observed between water temperature and 

 egg size. These data may help explain some of the 

 variability observed in the relation between yolk-con- 

 version efficiency or maximum larval size and incuba- 

 tion temperature (Sweet and Kinne 1964, Alderdice 

 and Forrester 1968, Laurence and Rogers 1976, 

 Linden et al. 1980, Johns et al. 1981, Laurence and 

 Howell 1981, Buckley 1982). Our data suggest that lar- 

 val size and composition at hatch and first feeding are 

 dependent not only upon incubation temperature but 

 also upon water temperature during the final stages 

 of gamete maturation and upon the interaction of water 

 temperature during these two time-periods. This im- 

 plies that the contents of the egg are modified in some 

 way in response to water temperature prior to spawn- 

 ing. Most likely, this temperature response goes beyond 

 simply producing a larger or smaller egg with com- 

 ponents in the same proportion. The ratio of major 

 organic components including protein, lipids, carbo- 

 hydrates, and nucleic acids may be altered in response 

 to temperature. More subtle, but possibly more signifi- 

 cant, changes in the composition of the developing 

 oocyte in response to water temperature may include 

 alterations in the content, composition, activity, or 

 stability of enzymes, hormones, maternal messenger 

 RNA, and stable RNA (tRNA and rRNA). Any conclu- 

 sions about the efficiency of yolk utilization at different 

 incubation temperatures should take into account the 

 thermal history of the spawning adults. 



Winter flounder reproductive strategy has most like- 

 ly evolved to exploit the dramatic increase in water 

 temperature during the spnng in the shallow estuaries 

 along the northwest margin of the Atlantic Ocean. 



Between spawning and metamorphosis, a period of 

 about 2 months in winter flounder, water temperatures 

 warm an average 10°C (from ~2° to 12°C) affecting 

 not only the abundance and composition of predators 

 and prey but also the rates of metabolic processes 

 (Laurence 1975, 1977). This maximizes size and condi- 

 tion of first-feeding larvae at low temperatures (Table 

 4), allows relatively long resistance to starvation at in- 

 termediate temperatures, and facilitates rapid larval 

 and postlarval growth at higher temperatures (Buckley 

 1982). Mortality of late embryos and larvae at cold 

 temperatures (<2°C) (Laurence 1975, Buckley 1982) 

 indicates that good survival of winter flounder is de- 

 pendent upon the expected spring warming. While 

 gametogenesis and embryo and larval development 

 show a wide range of temperature tolerance in winter 

 flounder, these processes appear to have been opti- 

 mized for cold winter temperatures followed by gradual 

 spring warming. Our data suggest that cold winters 

 followed by gradual spring warming favor good sur- 

 vival and recruitment of winter flounder by facilitating 

 production of the largest larvae at first feeding (high 

 standard length and DNA content) in the best condi- 

 tion (high RNA and protein content). These data may 

 explain in part the observed correlation between cold 

 years and strong year-classes (Jeffries and Johnson 

 1977, Jeffries and Terceiro 1985, Northeast Utilities 

 1988). 



Citations 



Alderdice, D.F., and C.R. Forrester 



1968 Some effect.s of salinity ami teni|ieraturt' on early develop- 

 ment and .survival of the English sole (Pa roph rys pentuhis). J. 

 Fish. Res. Board Can. 25:49.5-521. 

 Bagenal, T.L. 



1971 The interrelation of the size of fish eggs, the date of 

 spawning and the production cycle. J. Fish. Biol. 3:207-219. 

 Bailey, K.M.. and R.S. Batty 



1984 Lal_H)ratory study of predation by .4 urclin aurita on lar- 

 vae of cod, flounder, plaice and herring: development and 

 vulnerability to capture. Mar. Biol. (Berl.) 8.3:287-291. 

 Blaxter, J.H.S., and G. Hempel 



1966 Utilization of yolk by herring larvae. J. Mar. Biol. 

 Assoc, U.K. 46:219-234. 

 Brett, J.R. 



1970 Temperature— fishes, hi Kinne, 0. (ed.), Marine ecology, 

 vol. 1, Environmental factors, p. 515-560. Wiley, London. 

 Brown, M.E. 



1957 Experimental studies on gi'owth. /n Brown. M.E. (ed.). 

 The physiology of fishes, chap. 9, p. 361-400. Acad. Press, 

 NY. 

 Buckley, L.J. 



1979 Relations between RNA-DNA ratio, prey density, and 

 growth rate in Atlantic cod (Gadus morhua) larvae. J. Fish. 

 Res. Board Can. 36:1497-1502. 

 1982 Effects of temperature on growth and biochemical com- 

 position of larval winter flounder Pxeudupleurimectes nmeri- 

 ainus. Mar. Ecol. Prog. Ser. 8:181-186. 



