e. Organic detritus has a complex origin. 



5. An alternative model of the trophic relationships of the coimunity 

 is presented. The observed food of each species is presented as a 

 continuum in which each type of food can be represented quantitatively 

 and comparatively. 



6. The abundant consumer species of the Lake Pontchartrain community 

 comprise two groups: those that feed heavily upon organic detritus 

 and those that exhibit a broad range of food tolerance. (G.S. and 

 author's summary) 



Keywords: estuarine community, aquatic ecosystem, primary production, 

 trophic relationships, Louisiana 



III-E-3 



Darnell, R.M. 1958. Food habitats of fishes and larger invertebrates of 

 Lake Pontchartrain, Louisiana, an estuarine corranunity. Publications 

 of the Institute of N'arine Science, University of Texas 5:353-416. 



This report deals with food habitats of 35 estuarine species of fishes 

 and invertebrates found in Lake Pontchartrain, Louisiana. About 1,399 

 detailed quantitative analyses and 100 quantitative analyses were carried 

 out. Nearly all the specimens were collected within a 14-month period. 



The food studies revealed two primary food chains within Lake Ponchartrain. 

 The first pathway proceeds from copepods ( Acartia ) through small fishes 

 (Anchoa, Brevoortia , very young sciaenids, etc. ). , to larger predators. 

 The second proceeds from small benthic invertebrates through larger 

 invertebrates and small bottom- dwelling fishes (catfishes, young 

 sciaenids, etc.), to the same large predators. Organic detritus, 

 which was prominent in the food of the fishes and larger invertebrates, 

 probably also serves as an important source of nutrition for the copepods 

 and small benthic invertebrates of this turbid estuary. Such detritus 

 has a very complex origin and it has been shown by other workers to 

 be rich in bacteria. 



An ontogenetic progression of food stages was clearly demonstrated 

 for several of the well studied species, and for one species (Atlantic 

 croaker) as many as four distinct nutritional stages were recognized. 

 Within a given stage considerable substitution of food items was 

 often observed. In some cases it was possible to correlate ontogenetic 

 changes in food utilization with changes in morphology, habitat, 

 feeding time, and behavior. As a result of their highly varied diets 

 including much detritus, most, if not all, of the species examined 

 are considered to be omnivorous. Distinct trophic levels (in the 

 sense of Lindeman) were not recognizable in this estuarine community. 



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