RESPONSES OF PLANKTONIC AND BENTHIC COMMUNITIES TO FERTILIZER AND FEED APPLICATIONS IN SHRIMP MARICULTURE PONDS

An experiment was performed to evaluate the responses of naturally occurring populations of plankton and benthos to applications of inorganic fertilizer and commercial marine ration in a shrimp grow‐out facility near Angleton, Texas. Ten ponds were stocked with an average of 17,000 post‐larval Penaeus stylirostris on July 8, 1980. Three of these ponds received fertilizer 19 days before stocking and again 7 days after stocking. Another 3 ponds were fed daily with Ralston Purina Experimental Marine Ration 20 beginning on the stocking day. Three other ponds received the 2 fertilizer applications and daily feed. One control pond was not given fertilizer or feed. Beginning 19 days before stocking and continuing for 14 weeks, samples were collected and quantitatively analyzed for chlorophyll, zoo‐plankton and benthic organisms. Results indicated that fertilizer stimulates the production of chlorophyll and planktonic copepods. Planktonic rotifers varied independently of feed or fertilizer. Densities of planktonic polychaete larvae seemed to be related to changes in the populations of benthic adult polychaetes. The benthic community was dominated by polychaetes, harpacticoid copepods and nematodes. Polychaetes tended to be more abundant when feed was present. Harpacticoids and nematodes did not seem to be affected by experimental treatments. All benthos fell to very low densities after 50 days of the study. The best shrimp production occurred in feed and fertilized ponds, followed by feed only, fertilizer only and the control. Potential linkages between natural production and shrimp growth are discussed.