Herbivory potential of postlarval brown shrimp associated with salt marshes

Laboratory feeding experiments were used to study the herbivory potential of postlarval brown shrimp (Penaeus aztecus Ives). Plant materials fed to shrimp included Skeletonema costatum (Greville) Cleve, Isochrysis sp., Spartina detritus, and Spartina epiphytes. A total of 16 treatments were derived from all possible combinations of the four materials. After 16 days the greatest increases in length and weight occurred in those treatments containing Skeletonema costatum (Skeletonema group) followed by Spartina epiphytes exclusive of the presence of Skeletonema (epiphyte group). Shrimp growth did not occur in beakers with (1) no food, (2) Isochrysis sp. or Spartina detritus alone or (3) Isochrysis and detritus in combination (Isochrysis-detritus-no food group). Ecdysis occurred in all treatments, except where no food was present, including those in which there was no measurable growth. Survival and growth were significantly higher in the Skeletonema and epiphyte groups compared to the Isochrysis-detritus-no food group. These results indicate that planktonic diatoms, such as Skeletonema, and epiphytes of Spartina are potential sources of nutrition for postlarval Penaeus aztecus in Spartina marshes.