NOTE Chen et al : Feeding and growth of larval Etrumeus teres and Brevoortia patronus 



187 



In two comparisons, the growth 

 curves of these species differed, 

 i.e., the sum of squares of the dif- 

 ferences between observed and 

 predicted lengths was greater 

 when data for the two species 

 were pooled than when the data 

 were considered separately. In 

 the comparison of larvae col- 

 lected in December 1980, the 

 sum of squares of deviations was 

 6.327 for pooled data and 2.736 

 for data considered separately 

 (total observations = 161). In the 

 comparison of larvae collected in 

 February 1981, from two tran- 

 sects, the sum of squares of devi- 

 ations was 13.255 for pooled data 

 and 10.477 for data considered 

 separately (total observations = 

 611). 



Elmmam lerat 



Brevoofll* palronu* 



ESTIMATED AQE (DAYS) 



Figure 2 



Age-specific growth rates of larval round herring Etrumeus teres and gulf menhaden 

 Brevoortia patronus collected in December 1980 (A) and February 1981 (B) in the north- 

 em Gulf of Mexico. Specific grovrth rates-at-age were derived from the log form of the 

 Laird-Gompertz growth model parameters. 



Discussion 



The large, spatulate, and toothed jaws of larval round 

 herring might enable them to eat larger food organisms 

 than gulf menhaden, but while the diets of larval round 

 herring and gulf menhaden differed, the width of food 

 organisms coincided. Diets, then, do not directly reflect 

 differences in jaw structure and dentition. The ptero- 

 pods eaten by both species were Limacina trochifor- 

 mis, the cyclopoid copepods were primarily of the 

 genera Oncaea and Corycaeus, and the calanoid cope- 

 pods were primarily of the genera Paracalanus and 



Acartia. Round herring larvae ate more pteropods and 

 cyclopoid copepods, but fewer calanoid copepods than 

 did gulf menhaden larvae. 



The more offshore distribution of larval round her- 

 ring in the central and western northern Gulf of Mex- 

 ico (Shaw and Drullinger 1990; present data) may 

 explain differences in diet and growth. All of the food 

 organisms eaten by larval round herring and gulf 

 menhaden are broadly distributed in continental shelf 

 waters, but some of the copepods have different pat- 

 terns of distribution across the shelf in the northern 



