and chaetognath were determined in the labora- 

 tory using larvae hatched from wild adults ac- 

 cording to methods detailed by Reeve and Walter 

 (1972) for S. hispida and Baker and Reeve 

 (1974) for M. mccradyi. Three separate popula- 

 tions of the chaetognath and two of the ctenophore 

 were grown at each of three temperatures (21°, 

 26°, 31°C), which corresponded to the mean 

 monthly minimum, annual mean, and mean 

 monthly maximum temperatures (to the nearest 

 1°C) off the laboratory dock in Biscayne Bay over 

 11 yr (unpubl. records). Food was provided in the 

 form of naturally occurring zooplankton of suit- 

 able size (see previously cited information on cul- 

 ture technique), consisting mostly of the copepods 

 Acartia tonsa and Paracalanus parvus, main- 

 tained at a level such that no more than 50% were 

 grazed down over 24 h. 



Growth rates were measured as length increase 

 to avoid sacrificing any members of the popula- 

 tions and the data converted to ash-free dry 

 weight as previously described. Total length of 

 Mnemiopsis was measured from the aboral to the 

 oral pole (or tip of the oral lobes in adults) as 

 described in detail by Baker (1973). 



FISHERY BULLETIN: VOL. 73, NO. 2 



Production Calculation 



The method of calculating production was that 

 employed by Mullin and Brooks (1970) and Hirota 

 (1974), where for each size class an exponential 

 coefficient of daily growth (G) and mortality (M) is 

 obtained from laboratory growth rate and field 

 size-frequency data. 



The growth coefficients were computed from the 

 slope of the line relating the logarithm of increase 

 in ash-free dry weight and age (Figure 1) follow- 

 ing Crisp (1971). Data from each rearing 

 experiment were combined for each species at the 

 specified temperature. For S. hispida, the 

 semilogarithmic relationship is linear over most of 

 its size range until growth levels off at maturity 

 (Reeve and Walter 1972). The termination of the 

 linear (i.e., constant exponential growth) phase 

 was arbitrarily set at 20, 25, and 30 days at 31°, 

 26°, and 21° C respectively, and the slope of the line 

 calculated by linear regression analysis. At each 

 temperature, slopes at two points beyond the 

 linear phase were required, and these were derived 

 by extrapolation on the basis of the remaining 

 data points and other (unpubl.) data on lengths of 



I r 



01 



>- 



Q 001 



UJ 

 UJ 



tr 



I 

 to 

 < 



001 



10 20 30 



AGE IN DAYS 



40 



50 



100 



10 



ct 

 Q 



X 



< 



01 



01 



MNEMIOPSIS 



10 



20 30 



AGE IN DAYS 



40 



50 



Figure L— Growth rate of Sagitta and Mnemiopsis at three different temperatures. 



242 



