Fish Production and Biomass Studies in Relation to Photosynthesis in the Laguna Madre of Texas

Hellier, Thomas

The rate of growth of populations of animal consumers depends to a considerable extent on the rate of food supply derived from photosynthetic production of plant material either within the community or that imported into the community. Yet few studies directly relate fish production to plant production. In the present study an effort has been made to relatefish production to gross plant production in a shallow, frequently hypersaline coastal bay, the Upper Laguna Madre of Texas. The Upper Laguna Madre is located on the Texas Gulf Coast immediately south of Corpus Christi Bay, and is separated from the Gulf of Mexico by a narrow barrier island, Padre Island. Biomass estimates of the animal species present were determined with a new population sampling device, the drop-net quadrat. The principle of this method is to instantaneously isolate a segment of the study area with its natural fish population, and by extrapolation determine the approximate density of the fish population of the area. Twenty-nine samples were taken over a 17 month period from March. 1958, to August, 1959.Age and growth estimates of the dominant fish species were determined by scale analysis, and by reference to length frequency histograms. A total of 31 species were taken during the study, five of which constituted approximately 70 percent of the biomass. These five species were: Mugil; cephalus, Lagodon rhomboides, Leiostomus xanthurus, Anchoa mitchlli, and Menidia beryllina. Fish production as used in this paper was defined as the weight increase of the fish per unit time while the fish were in the study area. The monthly weight increases for all of the individuals collected during each month were totaled and placed on a per acre basis. Primary gross plant production was measured by the diurnal oxygen method with oxygen samples taken every three hours over a 24 hour period. Biomass estimates of fish and larger invertebrates ranged from a summer maxim of 337 pounds(per acre g/m2) to a winter minimum of 18 pounds per (2.Og/m2). The annual fish productionestimate was 137 pounds per acre (15.4 g/m2 dry weight) as compared with an annual gross primary plant production estimate of 4177 g/m2/yr expressed as oxygen. The seasonal migration and growth of fish stocks are in phase with the primary production of food.

Fish Production and Biomass Studies in Relation to Photosynthesis in the Laguna Madre of Texas

Series