FISHERY BULLETIN: VOL. 78. NO. 2 



km. At the station where vegetation and epiben- 

 thic prey organisms were sparse, pinfish took more 

 food from the water column (e.g., copepods, chae- 

 tognaths, and polychaete larvae) than at other 

 stations. Due to the lack of vegetable matter at 

 this station, pinfish consumed Brachidontes exus- 

 tus which lives on oyster bars near the unvege- 

 tated site. A high percentage of empty stomachs at 

 the unvegetated site indicates that feeding condi- 

 tions there were poor, especially for postlarval and 

 adult pinfish. Although selection of food by fish is 

 confounded by food preferences, the consumption 

 of food by pinfish appears to reflect local, geo- 

 graphic, and seasonal abundances of the food or- 

 ganisms and the morphological limitations of the 

 consumer. 



Temporal variations in the food habits of L. 

 rhomboides were well explained by abundance of 

 prey types in the field, but the correlations were 

 complex. Amphipod, shrimp, and plant consump- 

 tions were all directly related to the abundance of 

 these primary food items in the field. Seasonal 

 relationships between food abundance and con- 

 sumption by fishes were observed by Lawler 

 (1965), Repsys et al. (1976), and Hickey (1975). 

 Diurnal changes in food habits have also been 

 explained by changes in prey availabilities (Hob- 

 son and Chess 1976; Robertson and Howard 1978). 

 Keast's ( 1 970) observation that close correlation of 

 prey availability with seasonality in food habits 

 holds for only the most important prey types was 

 also observed in this study. For example, poly- 

 chaetes were relatively minor components of 

 pinfish diets and showed no correlation with sea- 

 sonal abundance patterns. On a statistical basis, 

 however, absolute abundance of a food item in 

 Apalachee Bay explained only part of the varia- 

 tion in consumption of that item. For example, 

 although amphipod consumption by juvenile 

 pinfish was directly related to amphipod abun- 

 dance in the field, amphipod intake was also in- 

 versely related to shrimp and plant abundances. 

 These inverse relationships were often stronger 

 than the positive relationship with amphipod 

 abundance. Similarly, shrimp consumption was 

 negatively correlated with amphipod and plant 

 abundances, suggesting that the relative abun- 

 dance of preferred prey items may be as important 

 as absolute abundance of any one type. The picture 

 is further clouded by the fact that plant material, 

 which serves as an important food source for 

 pinfish >35 mm, is also an obvious component of 

 the habitat that lends protection to many small 



348 



prey species (Nelson 1978; Stoner 1979a). Two ex- 

 planations for the increased plant consumption 

 with benthic macrophy te biomass are plausible: 1 ) 

 plant material is taken as a simple response to its 

 abundance, and/or 2) T. testudinum blades pro- 

 vide amphipods, shrimp, and other animal prey 

 with protection from fish predation and inhibit the 

 consumption of these animals; therefore, as blade 

 density or plant biomass increases, macrophytes 

 and epiphytes are taken as alternative food. Both 

 mechanisms are probably influential in the de- 

 termination of food habits in pinfish; however, the 

 latter hypothesis is probably the most important 

 mechanism since cellulase activity is not found in 

 the alimentary tract of L. rhomboides (Stickney 

 and Shumway 1974). Densely vegetated seagrass 

 habitats support greater densities and biomass of 

 potential prey species than unvegetated or 

 sparsely vegetated substrates (O'Gower and 

 Wacasey 1967; Orth 1977; Brook 1978; Stoner in 

 press), although is is unknown as yet whether 

 this relationship is due to reduced predation on the 

 animals or some property inherent in the struc- 

 ture of the habitat. The problem of omnivory in 

 pinfish would be an especially fertile area for in- 

 vestigation in terms of optimal foraging theory, 

 but a large array of carefully controlled field and 

 laboratory experiments would be required. 



Dietary specialization is generally found to be 

 correlated with increasing food abundance. This 

 conclusion is supported by models of predator-prey 

 relationships (see review by Pyke et al. 1977) and 

 empirical studies with fishes (Ivlev 1961; Zaret 

 and Rand 1971; Werner and Hall 1974). On the 

 basis of seasonal prey abundance patterns and the 

 diets of pinfish between 16 and 80 mm SL, dietary 

 specialization did occur with periods of high prey 

 abundance. For example, at the vegetated stations 

 amphipods and other macrobenthic organisms 

 were most abundant between February and May. 

 Lowest dietary diversities occurred during the 

 same time period. With adult fish, however, the 

 characteristic relationship did not seem to hold. 

 Fenholloway 12 and Econfina 10 showed similar 

 seasonal trends in abundance of food organisms 

 yet seasonality of dietary diversity was entirely 

 different at the two stations. Also, on a spatial 

 basis, lowest dietary diversity occurred at the site 

 with extremely low food abundance (Fenholloway 

 11) for fish between 16 and 80 mm SL. More 

 generalized diets were found at the vegetated sites 

 where food was more abundant. The predicted re- 

 lationship of increasing dietary specialization 



