Substrate selection by demersal calanoid copepods in shallow waters of Galveston Bay, Texas.
Natural substrate selection during the day by demersal calanoid copepods in Galveston Bay was examined with a suction sampler. Copepods were most abundant on silty-sand areas and sand flats compared with oysters. This substrate selection was more marked for males than for females and for juveniles compared to adults. Plankton tows at night over the different substrates provided density estimates of copepod populations which paralleled daytime densities. Pseudodiaptomus coronatus was the dominant species in the benthic samples and was most abundant on the silty-sand substrate fringing the oyster reef. A manipulative field experiment using containers filled with known substrates showed more P. coronatus present on oyster shell hash and clay than on sand. In laboratory studies on substrate selection by P. coronatus, clay and sand substrates were selected over oyster shell and the glass control. Differences in results of the various methods may be attributed to predator abundance and/or substrate coloration. Acartia tonsa and Paracalanus crassirostris exhibited demersal tendencies but showed no consistent substrate preferences. Pseudocyclops sp. was found almost exclusively on the oyster shell in the substrate container. Pigmented calanoid copepods that are larger (P. coronatus) and slower (Pseudocyclops sp.) possibly utilize different substrates as an adaptive strategy against predation pressure.