FISHERY BULLETIN: VOL. 78, NO. 2 



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Figure 9. — Breadth of diet in Lagodon rhomboides from four 

 sites in Apalachee Bay, Fla., shown as a function of season. Each 

 value is the Shannon- Weiner index, H', for the food items con- 

 sumed by fish of three size classes. Crosses = Fenholloway 11, 

 triangles = Fenholloway 12, dots = Econfina 10, circles = 

 Econfina 12. 



mm, dietary diversity was highest at the sparsely 

 vegetated station because, in addition to plant 

 material, mussels, polychaetes, and other animal 

 prey made an important contribution to the diet. 

 At the Econfina stations, the diets of adult fish 

 were dominated by plant material causing low 

 dietary diversity. 



Pinfish between 36 and 80 mm SL showed 

 greatest breadth in diet; however, some degree of 

 seasonality in dietary diversity occurred in all fish 

 >15 mm (Figure 9). In fish between 16 and 35 mm, 

 peak dietary breadth in June and July corre- 

 sponded with periods of low amphipod abundance 

 and a change in food habits to alternative prey 

 types including shrimp and plant material. Low- 

 est dietary breadth in fish between 36 and 80 mm 

 occurred in the late winter and spring when am- 

 phipods were abundant and macrophyte biomass 

 was low. Diversity of food items available was 

 probably lowest at this time. Dietary diversity in 

 fish >80 mm SL reflected the degree of carnivory 

 by the fish. At Fenholloway 12 dietary diversity 



346 



was highest in March and April when various 

 animal foods were consumed in large quantities. 

 At Econfina 10, highest diversity occurred in Au- 

 gust when a large number of animal foods 

 supplemented a normally herbivorous diet. Dur- 

 ing late spring and summer months, dietary di- 

 versity indices at Econfina 10 and Fenholloway 12 

 converged to similar values as fish at both stations 

 became largely herbivorous. Very low dietary di- 

 versities occurred at Econfina 10 in September 

 and October because over 98% of the diet was 

 composed of plant material. 



DISCUSSION 



Pinfish from Apalachee Bay passed through five 

 major ontogenetic feeding stages, including 1) 

 planktivory; 2) carnivory on amphipods and har- 

 pacticoid copepods; 3) omnivory on amphipods, 

 shrimp, and microepiphytes; 4) omnivory on 

 epiphytes, amphipods, polychaetes, and isopods; 

 and 5) herbivory on epiphytes and vascular plant 

 material (primarily S. filiforme). Darnell (1958) 

 and Carr and Adams ( 1973) provide the most reli- 

 able data for comparison with the present study on 

 food habits of L. rhomboides since each provided 

 information on ontogenetic variation in the diets 

 of the fish. Darnell, studying stomachs of pinfish 

 from Lake Ponchartrain, La., found that the im- 

 portance of amphipods and other small crusta- 

 ceans decreased with pinfish length (40-150 mm 

 SL), while vegetable material became increas- 

 ingly important in diet with fish size. Except that 

 Darnell found dipterans to be a common food item 

 in fish from Lake Ponchartrain, his findings were 

 similar to mine. Pinfish collected near Crystal 

 River, Fla., showed five trophic stages (Carr and 

 Adams 1973); the stages were different from those 

 reported here (Table 7). Unlike pinfish from 

 Apalachee Bay, those from Crystal River became 

 herbivores at an early stage (36-60 mm SL), and 

 later showed strict carnivory on fish and shrimp 

 (>80 mm SL). Fishes were rarely found in the 

 stomachs of pinfish from Apalachee Bay and the 

 pattern of increasing herbivory with fish length 

 appeared to hold except at the unvegetated site 

 where plant material was not available. Because 

 stomach analyses for both geographical areas cov- 

 ered a full year, differences between the findings of 

 the two studies cannot be attributed to artifacts 

 introduced by seasonal variation in diet. Rather, it 

 is likely that different abundances of suitable prey 

 or plant items explain geographical differences in 



