Effects of caging juvenile predators on benthic infaunal populations at experimental open bay disposal areas in Galveston Bay, Texas




Minello, Thomas J. and Ronald Wooten, Jr.

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National Marine Fisheries Service, Southeast Fisheries Center,


Predator enclosure experiments were conducted in the spring and fall of 1992 at control plots and experimental plots (which were made of dredge material) in Galveston Bay in order to the examine the trophic relationships between macrobentic and nektonic consumers and benthic infaunal prey. Caged for a period of 3-5 days were juvenile brown shrimp, sciaenid fish, white shrimp, and blue crabs. Survival of crustacean predators in the cages was high, while none of the experimental fish survived. The impact of enclosed predators on the benthic infauna was determined by comparing biomass and infaunal density in treatment cages with control cages which contained no predators. Growth of the predators was also measured. The most abundant infaunal group, the annelids, appeared not to experience any predation by experimental predators. Previous research had shown that annelids were commonly eaten in the diets of these predators and were a valuable prey item. Annelid densities at the plots may have been too low to allow efficient exploitation by predators. It did not appear that blue crabs fed on an infauna although positive crab growth was measured at the control plots. Growth rates of the blue crab were significantly reduced at experimental plots with dredged material. Juvenile brown shrimp and white shrimp fed on small mollusks and amphipods. Prey reduction was greater at control polts than at experimental plots. This suggests that dredged material sediments provided fewer prey. Shrimp growth rates were not significantly different among the plots.


73 pgs.


nekton, benthos, dredge spoil, fish population, feeding, feeds, dredging spoil, environmental aspects, fish populations, houston ship channel, galveston ship channel, environmental conditions