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

Abstract

The diet of juvenile pink shrimp (Farfantepenaeus duorarum Burkenroad, previously Penaeus duorarum) from Long Key Bight, Florida Keys, was studied using stomach content examination, pigment measurements, and stable isotope (δ13C and δ15N) analysis. Samples were taken over approximately 24 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 content volume. Other common components of the diet were bivalves (mainly Tellina sp.) with 15% volume, calcareous algae (8%), plant detritus (5%), copepods (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 determined experimentally at 1.3 ± 0.5 h−1. Daily rations (in percent body weight) calculated from time series of stomach fullness ranged between 11 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. δ13C-values of whole animals of both species were identical at −10.0 ± 1.6‰ PDB. δ15N-values of both species were also not significantly different (pooled mean: 5.9 ± 1.7‰). Stomach contents of wild-caught F. duorarum and stomach contents of F. duorarum fed T. floridanus also showed similar stable isotope values.