Penaeid_Shrimp_Shrimp_Emergence_Data

Brown shrimp, Farfantepenaeus aztecus, and white shrimp, Litopenaeus setiferus, were held were held under natural light conditions before experiments. Experiments were conducted in twelve rectangular tanks (58 cm x 149 cm) under fluorescent lighting (7-10 microEinsteins/sec/sq m). Shrimp were placed in randomly-assigned tanks the day before observations were initiated at 0730 h, the lights were turned on, and observations of thepercentage of shrimp burrowed ( 1/2 of their body beneath the substrate) were recorded hourly (starting at 0830 h) throughout the daylight hours. For both species, burrowing rates decreased significantly as the substrate became courser. Brown shrimp burrowing was marginally affected by salinity with the lowest burrowing rates at 5 ppt white shrimp burrowing was not significantly affected by salinity. Large brown shrimp burrowed more than small and medium sized shrimp, but size did not significantly affect burrowing of white shrimp. The presence of a fish predator in the tanks did not affect burrowing of either species, but hunger level significantly affected burrowing for both species.

Study of shrimp behavior

"Juvenile shrimp were collected in the Galveston Bay system of Texas, U.S.A. and held before experiments in the laboratory under natural light conditions (skylights) in fiberglass tanks with a crushed shell substrate. Burrowing experiments were conducted in twelve rectangular tanks (58 cm x 149 cm; 0.86 m2 area) located in a dark temperature controlled room equipped with fluorescent lighting and under a 12:12 h day:night light regime. Light was constant during the daylight period in these experimental tanks and was measured near the substrate using a LI-COR quantum meter (Model LI-185B). From 10 observations in each tank during the simulated daylight hours, the mean intensity was 10.6 (SE=0.18) ¿E (microEinsteins) s-1m-2. This light intensity is comparable to the light reaching the bay bottom during a sunny day when incident light at the water’s surface is ~ 1000-2000 ¿E s-1m-2 and the following approximate conditions occur: water depth 2 m, nephelometric turbidity 20 FTUs, an attenuation coefficient (Kd) of 2.0, and a Secchi disk depth of 0.5-0.7 m. Tanks were filled to a depth of 25 cm with sand-filtered seawater pumped from the Gulf of Mexico off Galveston Island.

When possible, treatments were randomly applied to tanks; the exception was for substrate experiments where different substrates remained in the same tanks throughout the experimental series. Shrimp from holding tanks, however, were randomly placed in tanks during all experiments. Shrimp were moved from holding tanks to experimental tanks in the afternoon on the day before observations were initiated. At 0730 h the next day, the lights came on, and observations on behavior were recorded hourly (starting at 0830 h) throughout the daylight hours (generally 10 hourly observations during the day). Black plastic curtains surrounded each tank, and observations were made through small portals to avoid disturbance. During each hourly observation period, individual shrimp were categorized into one of eight behaviors."