FOOD HABITS OF JUVENILE MARINE FISHES: EVIDENCE OF THE 



CLEANING HABIT IN THE LEATHERJACKET, OLIGOPLITES SAURUS, 



AND THE SPOTTAIL PINFISH, DIPLODUS HOLBROOKI 



William E. S. Carr and Clayton A. Adams' 



ABSTRACT 



Quantitative gravimetric analyses of stomach contents of juvenile leatherjacket, Oligo- 

 plites saurus, and spottail pinfish, Diplodus holbrooki, have revealed that both species 

 pass through a stage in which they clean ectoparasites from other fishes. This cleaning 

 stage is most evident in juveniles between 26 and 40 mm standard length and is far less 

 evident among juveniles of larger or smaller size. These findings represent the first 

 report that cleaning is practiced by either species and the first quantitative data on the 

 significance of the cleaning habit to members of the Family Carangidae and Family 

 Sparidae. Neither 0. saurus nor D. holbrooki depend exclusively on cleaning as a source 

 of food. Juveniles of O. saurus feed heavily on plankton and small shrimp whereas 

 juveniles of D. holbrooki feed heavily on epiphytic algae, plankton, and encrusting or- 

 ganisms. Juveniles of both species exhibit distinct changes in diet during growth. 



The important role of the estuarine zone in pro- 

 viding nursery areas utilized by the juvenile 

 stages of a large number of marine fishes is now 

 well documented (Sykes and Finucane, 1966; 

 Smith, Swartz, and Massmann, 1966; and 

 others). Although much is known about the 

 food habits of the adults and subadults of most 

 estuarine-dependent species, only a limited lit- 

 erature exists on the food habits of the smaller 

 juvenile individuals. Consequently, we have 

 been studying the food habits of juveniles of all 

 available species of fishes which inhabit certain 

 nursery areas in the nearshore estuarine zone 

 between the Crystal River and the Withlacoochee 

 River on the northwest coast of Florida. To date 

 our study involves 18 species which we are 

 studying concurrently. 



In the course of the investigation described 

 above, we have discovered that juveniles of two 

 species, the leatherjacket, Oligoplites saurus 

 (Bloch and Schneider) (a carangid), and the 

 spottail pinfish, Diplodus holbrooki (Bean) (a 

 sparid), clean ectoparasites from other fishes. 



^ Department of Zoology, University of Florida, 

 Gainesville, FL 32601. 



This phenomenon has not been reported previ- 

 ously for either species. The report which 

 follows describes the diets of juveniles of both 

 species and shows that these diets include con- 

 siderable amounts of ectoparasites and other 

 material obtained by cleaning. 



MATERIALS AND METHODS 



DESCRIPTION OF STUDY AREA AND 

 SAMPLING METHODS 



Specimens of juvenile Oligoplites saurus and 

 Diplodus holbrooki were collected in the vicinity 

 of the Florida Power Corporation steam electric 

 station located 7.5 miles northwest of the 

 town of Crystal River, Fla. (lat 23°57'N, long 

 82°45'W). This station is situated approxi- 

 mately 3 miles northwest of the mouth of the 

 Crystal River and 4 miles southeast of the mouth 

 of the Withlacoochee River on the northwest 

 coast of Florida. Sampling sites in this estuarine 

 area were located to the north and south of the 

 dikes delimiting the intake canal of the electric 

 station. The sampling sites were densely veg- 

 etated with seagrasses, primarily Ruppia mar- 

 itima and Diplanthera wrightii, and several 



Manuscript accepted March 1972. 



FISHERY BULLETIN: VOL. 70, NO. 4, 1972. 



1111 



