STONER: FEEDING ECOLOGY OF LAGODON RHOMBOIDES 



Table 2. — Composition of stomach contents of Lagodon rhom- 

 boides at four stations in Apalachee Bay, Fla. Each value is the 

 mean percentage of the total dry weight of stomach contents for 

 the fish size class indicated. 



^ 100 n 



Item 



Fen 11 



Fen 12 Econ 10 Econ 12 



n (% empty) 

 Calanoid copepods 

 Invertebrate eggs 

 Detritus 

 Harpacticoid 

 copepods 

 Amphipods 



n (% empty) 

 Harpacticoid 

 copepods 

 Amphipods 

 Invertebrate eggs 

 Shrimp postlarvae 

 Polychaetes 

 Plant matter 

 Shrimp 



Calanoid copepods 

 Miscellaneous 



n (% empty) 

 Amphipods 

 Plant matter 

 Harpacticoid 

 copepods 

 Shrimp postlarvae 

 Shrimp 

 Polychaetes 

 Calanoid copepods 

 Invertebrate eggs 

 Bivalves 

 Miscellaneous 



n (% empty) 



Plant matter 



Polychaetes 



Amphipods 



Bivalves 



Miscellaneous 



Total number 



% Empty 



SL = 11-15mm 

 23(70.0) 10(70 0) 



58.1 91.9 



23.9 



18.0 8.1 



SL = 16-35 mm 

 14(14.3) 140(5.0) 



7.0 



30.0 



9.5 



3.0 



3.0 



40.0 

 7.5 



40.8 

 18.3 

 8.0 

 6.0 

 2.8 

 2.9 

 5.3 



15.9 



SL = 36-80 mm 

 35(8.6) 380(6.6) 

 56.8 272 



16.5 25.3 



0.8 

 0.8 

 1.3 

 3.3 

 3.3 

 0.8 



16.4 



5.6 

 2.8 



12.3 

 5.0 

 2.9 

 3.5 

 3.7 



11.7 



SL > 80 mm 

 10(30.0) 85(15.3) 



6.0 

 0.7 

 6.0 

 81.3 

 6.0 



82 



29.3 



63.3 



4.9 



8.1 



10.1 



13.6 



615 



8.4 



35(42.8) 

 17.3 

 47.7 



19.0 

 16.0 



213(1.4) 



26.5 



38.5 

 2.7 



13.5 

 1.7 

 2.5 

 1.5 

 1.0 



12.1 



460(3.0) 

 27.2 

 30.0 



6.4 

 4.2 

 9.7 

 2.5 

 2.6 

 29 

 0.4 

 14.1 



78(11.5) 



84.3 



0.1 



2.4 



0.4 



12.8 



786 



5.2 



7.3 

 7.5 

 1.0 

 4.2 

 0.2 

 5.2 

 8.0 



408(4.4) 

 30.1 

 23.0 



6.0 

 1.4 

 17.7 

 5.2 

 3.6 

 5.0 



8.0 



20(15.0) 

 91.7 



2.0 



63 

 691 

 5.5 



larval fish at Econfina stations 10 and 12 only. The 

 small epifaunal amphipod Gitanopsis tortugae, 

 one of the few species consumed by small pinfish, 

 was collected only at these two stations during 

 these months (see Stoner (1979a) for a detailed 

 analysis of prey species consumed by L. rhom- 

 hoides). Because no data are available on abun- 

 dance of harpacticoid copepods in Apalachee Bay, 

 the importance of their abundance to food habits of 

 pinfish remains unknown. 



The main components of the diets of pinfish be- 

 tween 16 and 35 mm were amphipods, harpac- 

 ticoid copepods, and shrimp postlarvae at the 

 three vegetated sites; amphipods and calanoid 

 copepods at Fenholloway 11. Shrimp and shrimp 

 postlarvae were abundant at the vegetated sta- 

 tions, but few in number at the unvegetated site 

 (Table 3). This probably explains the differences in 

 shrimp consumption. Calanoid copepods were ap- 





80 



60 - 



40 



20 



A 2 



y = 0.026 X * 13.13 

 r = 0.804 



1 1 1 1 



1000 2000 3000 4000 



Abundance of Copepods (N/nn^) 



Figure 4. — Percentage of stomach contents (dry weight) of post- 

 larval pinfish composed of calanoid copepods shown as a fimction 

 of copepod abundance in Apalachee Bay, Fla. Cross = Fenhollo- 

 way 11, triangle = Fenholloway 12, dots = Econfina 10, circles = 

 Econfina 12 . Months are indicated by numbers beside the plotted 

 points. 



parently substituted for shrimp at Fenholloway 

 11, although the copepods were less abundant at 

 that site than at other stations (Econfina 10 and 

 12) between April and July (Table 3). Low abun- 

 dance of harpacticoid copepods may explain their 

 relatively low contribution to the food habits of 

 young pinfish at the unvegetated site. 



Diets of fish from 36 to 80 mm were similar at 

 the three vegetated stations and included large 

 amounts of amphipod, shrimp, and plant material. 

 At the unvegetated site, amphipods made up ap- 

 proximately twice the percentage found in fish 

 from vegetated stations. Because of low shrimp 

 abundance at the unvegetated site, shrimp con- 

 tributed little to the diets of fish inhabiting that 

 site. Amphipods appear to have been substituted 

 for shrimp. 



Fish >80 mm demonstrated wide variability in 

 the percentage of the stomach contents composed 

 of plant material, ranging from 6.0% at Fenhollo- 

 way 11 to 91.7% at Econfina 12. The diet offish 

 from the unvegetated station was dominated by 

 the mussel Brachidontes exustus. For adult fish, 

 the mean percentage of the diet composed of plant 

 material was a direct function of the mean stand- 

 ing crop of benthic macrophytes at a given station 

 (r = 0.952, P<0.05); however, there was wide 

 temporal variation in the standing crop of benthic 

 macrophytes at the vegetated sites (Table 3) which 

 was not followed by proportional changes in plant 

 consumption at Econfina 10 and Fenholloway 12. 



341 



