Variations in the feeding habits of Callinectes rathbunae in Las Palmas lagoon (southern Gulf of Mexico) on three temporal scales

Abstract

Las Palmas lagoon is a part of the hydrographic system of Pom-Atasta-Puerto Rico, NE of Laguna de Terminos, southern Gulf of Mexico. Swimming crabs of the genus Callinectes abound in this area and play an important role in the complex trophic dynamics of the macrobenthos. We analysed the feeding habits of Callinectes rathbunae and its variations on three temporal scales. Sampling was carried out from August 1999 through July 2000, both on a monthly basis (9:00-13:00 h) at new moon, and for each season (every 6 h during 24 h) with a small shrimp trawl net. Samples of epi- and infauna were simultaneously taken. The stomachs of all C. rathbunae collected were dissected and the dietary components identified to the lowest taxonomic level possible. Percentage frequency of occurrence (%F) of each taxon was calculated, together with the normalized Levins index (Ba) for each (a) season, (b) size class (20 mm intervals), and (c) day- and night-time period in each season. While the trophic niche breadth of this species does not vary significantly with season, crab size, or time of day, diet components differed among seasons and crab size classes. Results indicate that ontogenic differences in the feeding strategies of this species contribute most importantly to overall variations in diet.