SUBSTRATE PREFERENCE IN AGE-0 RED SNAPPER, LUTJANUS-CAMPECHANUS

We tested age-0 red snapper, Lutjanus campechanus, for sand or shell s ubstrate preference in a circular tank (1.5 m diameter x 0.6 m deep). The test tank was divided into two equal areas of whole oyster shell o r sand substrates. All trials were video taped for 20 to 25 min. Tapes were viewed on a monitor and locations of all fish recorded and timed with respect to substrate. Mean +/- SE time on shell was 11.6 +/- 0.5 sec (4 fish trial(-1)) and 13.8 +/- 1.1 sec (1 fish trial(-1)). Mean +/- SE time on sand was 9.7 +/- 0.4 sec (4 fish trial(-1)) and 8.9 +/- 0.5 sec (1 fish trial(-1)). Fish spent significantly more time on she ll compared to sand substrate in four-fish trials (paired t-test, p < 0.10) and also in single-fish trials (paired t-test, p < 0.05). Shell substrate may offer increased food and shelter for age-0 red snapper c ompared to sand substrate. However. a preference for shell substrate i n the natural habitat may occur only during the nursery period, becaus e as fish grow (> 100 mm TL) in the late fall they probably outgrow th e shell habitat.