FLINT and RABALAIS: GULF OF MEXICO SHRIMP PRODUCTION 



fisheries. Whereas we propose a detrital-based 

 food web dependent on about 80% of the primary 

 producer biomass being directed to the bottom, 

 Steele (1974) indicated that only 307^ of the pri- 

 mary production reached the benthos in the North 

 Sea. On the other hand, Mills and Fournier (1979) 

 observed that the majority of primary production 

 was diverted to the bottom on the Scotian shelf. 

 This primary production, however, was not 

 adequate to satisfy the requirements of the 

 benthic or pelagic food chains. The importance of 

 herbivorous zooplankton and secondary consum- 

 ers, such as ctenophores and chaetognaths, was 

 emphasized by Mills and Fournier as elements 

 potentially characterizing the structure of energy 

 transfer in the Scotian shelf ecosystem. From the 

 evidence available, the inner shelf ecosystem of 

 the northwestern Gulf of Mexico, with its food 

 webs leading to commercially important penaeid 

 shrimp, appears different in structure from other 

 areas with major commercial fisheries. The con- 

 cept that food webs leading to these fishery popu- 

 lations are similarly constructed is not supported 

 by our study, which only further points out what 

 Mills and Fournier (1979) emphasized — detailed 

 regional studies are needed before predictive mod- 

 els can be "developed for these fisheries. 



Our theoretical model of the trophic structure 

 supporting the penaeid populations in the north- 

 western Gulf of Mexico is an approach to the de- 

 tailed regional studies that are necessary. Much 

 still needs to be done to define the pathways of 

 nutrition and the implications of these pathways 

 being interrupted by major environmental distur- 

 bances. Research on shrimp migratory patterns, 

 behavior, response to environmental factors, and 

 fishery statistics alone will not provide adequate 

 information about the functioning of an ecosystem 

 with respect to the trophic structure supporting a 

 commercial fishery. Our study pinpoints some of 

 the potential pathways of energy flow. The need for 

 research to define the functioning of the ecosystem 

 of which penaeid shrimps are a part cannot be 

 overemphasized. 



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