Feeding strategy and daily ration of juvenile pink shrimp (Farfantepenaeusduorarum) in a South Florida seagrass bed

The diet of juvenile pink shrimp (Farfantepenaeus duorarum Burkenroad, prev iously Penaeus duorarum) from Long Key Eight, Florida Keys, was studied usi ng stomach content examination, pigment measurements, and stable isotope (d elta(13)C and delta(15)N) analysis. Samples were taken over approximately 2 4 h on four occasions from December 1997 to June 1998. Juvenile F. duorarum fed nocturnally, the main prey being the seagrass shrimp Thor floridanus ( Decapoda: Caridea: Hippolytidae), which accounted for 34% of the stomach co ntent volume. Other common components of the diet were bivalves (mainly Tel lina sp.) with 15% volume, calcareous algae (8%), plant detritus (5%), cope pods (3%), and seagrass fragments (2%). Pigment concentrations (chlorophyll a plus phaeopigments) in F. duorarum stomachs ranged from 7 to 73 mg l(-1) or 40 to 310 ng stomach(-1). The exponential gastric evacuation rate was d etermined experimentally at 1.3 +/- 0.5 h(-1). Daily rations (in percent bo dy weight) calculated from time series of stomach fullness ranged between 1 1 and 16% d(-1). Total consumption by the population (in wet weight) ranged between 0.05 and 0.3 g m(-2) d(-1). Stable isotope measurements confirmed that T. floridanus was the main food source for F. duorarum. delta(13)C-val ues of whole animals of both species were identical at -10.0 +/- 1.6 parts per thousand, PDB. delta(15)N-values of both species were also not signific antly different (pooled mean: 5.9 +/- 1.7 parts per thousand,). Stomach con tents of wild-caught F. duorarum and stomach contents of F. duorarum fed T. floridanus also showed similar stable isotope values.