TABLE 14. Larval winter flounder yolk absorption time and growth rate from hatching through 40 

 days at four temperature regimes in a laboratory rearing study. 



Other laboratory growth studies on winter 

 flounder larvae (Laurence 1975, 1977; Buckley 

 1980, 1982) were not directly comparable to our 

 results because the published growth rates were 

 not expressed in length. Buckley (1982) reported 

 enhanced growth, measured as protein weight, at 

 a constant temperature of 10°C compared to 5 

 and 7°C, whereas a decrease in growth was found 

 in our study at a mean temperature of 10.8°C 

 compared to 6.9 and 7.5°C. This inconsistency 

 could have been related to insufficient food in our 

 study, as Laurence (1975) found increased meta- 

 bolic demands with increasing temperature. Dur- 

 ing our study, we attempted to maintain excess 

 food levels, but no quantitative sampling of prey 

 densities was conducted. The results of treatments 



1, II, and III agreed with the laboratory results of 

 Laurence (1975), with growth rate increasing as 

 temperatures increased from 2 to 5 to 8°C. 

 Growth was expressed as a daily percent increase 

 in weight from the time of fu'st feeding, or as 

 daily specific growth rates (SGR). In an attempt 

 to make a comparison, the estimated length at 40 

 days from hatching was converted to weight by 

 a length-weigjit relationship and the estimated 

 weight at first feeding was the mean weight (1 1.9 

 lig) at first feeding of the three treatments reported 

 by Laurence (1975). Estimated SGR for treat- 

 ments I, II, III and IV were 10.3, 13.6, 12.7, and 

 11.9% per day, respectively. These estimates 

 were higher than those reported by Laurence for 



2, 5, and 8°C of 2.6, 5.8 and 10% per day, re- 

 spectively. The laboratory conditions of other 

 studies on larval winter flounder growth differed 

 from ours because constant temperatures were 



maintained throughout development. The gradual 

 increase in temperature during development in 

 our study was meant to more closely mimic actual 

 field conditions during larval development. 

 Whether the diflerence in growth rates expressed 

 as SGR was related to the increasing temperatures 

 during the study or an artifact of converting length 

 to weight was not known. 



Mean weekly lengths at station C were used 

 to estimate larval growth rates for comparison 

 with the laboratory-rearing data. This station was 

 used because all developmental stages were col- 

 lected there in abundance (Fig. 19). Examination 

 of mean weekly lengths for each year since 1983 

 showed that growth through time had a sigmoid 

 shape (Fig. 28). During the beginning of the 

 larval season, the weekly mean lengths remained 

 fairly constant at about 3 mm, the approximate 

 size at hatching, due to the recruitment of large 

 numbers of newly-hatched larvae. During the 

 latter portion of the season, mean lengths re- 

 mained constant or declined, probably due to the 

 loss of metamorphosing larvae that were no longer 

 susceptible to capture. To estimate growth rates, 

 a linear regression was fit to those weekly means 

 that showed a consistent increase from week to 

 week during the middle of the larval season (Table 

 15). The range of annual estimated growth rates 

 were similar to those found in the laboratory at 

 the intermediate temperature regimes (treatments 

 II and III). Mean water temperatures were cal- 

 culated from data collected by a continuous tem- 

 perature recorder located at a dock near the mouth 

 of the Niantic River. For 1983 through 1985 

 these data were available only as weekly means. 



Winter Flounder Studies 



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