FISHERY BULLETIN: VOL. 76, NO. 2 



Insects: only the larva of the chironomid Tel- 

 matogeton minor. 



Brachyurans: Rhyncoplax bovis and the gut of 

 an unidentified crab (in a single case). 



Molluscs: Gibbula rosea, Helcion pruinosus, 

 Philine aperta, and a rhaciglossid (no shell, so not 

 possible to identify further). 



Hydrozoans: Symplectoscyphus sp. and 

 Thecocarpus formosus were ingested by one fish in 

 the 50- to 70-mm size class. 



Echinoderms: Parechinus sp. 



Tanaidaceans: Leptochelia barnardi most com- 

 monly found, also an Apseudes sp. 



Mysidaceans: only one species, Mysidops 

 similis, could be identified with any certainty. 



Di plod us cervintis 



The diet of Diplodus cervinus is illustrated in 

 Figure 8 and Table 3 (n = 67). The juveniles 

 (10-20 mm) fed mainly on harpacticoid copepods 

 and chironomid larvae. In the next size class 

 (20-35 mm), juveniles of the sand shrimp, 

 Palaemon pacificus, were taken instead of 

 chironomid larvae. This trend continues in the 35- 

 to 50-mm size class, the diet being composed 

 largely of P. pacificus as well as harpacticoid 

 copepods. Polychaetes are more important in this 

 size group, a trend which is maintained in all 

 larger size classes. In the larger fish, there was 

 again a changeover, the percentage of amphipods 

 taken being 65.7% (50-75 mm) and 27.6% (75-100 

 mm). Unidentifiable crustacean fragments in 



100' 



80' 



60 



40 



20 



Length (nun) 10 

 No.of Fish 



135 



Figure 8. — Changes in diet with length in Diplodus cervinus , as 

 shown by the comparative feeding index. Food items included in 

 Others are: chlorophytan algae, cirripede nauplii, coralline al- 

 gae, molluscs, mysidaceans, ostracods, tanaidaceans, and the 

 unidentified trochophore larva. 



these size classes composed 12.6% and 47.9%, re- 

 spectively, which is partly explained by the fact 

 that 6 of the 40 fish were taken at night and their 

 stomach contents were largely digested and thus 

 indistinguishable. The diet of the largest size class 

 ( 100-135 mm) was made up mainly of polychaetes. 



Identity of Food 



The diet was composed of almost all the food 

 species listed for D. sargus, although in differing 

 proportions, as well as the following: Cymodocella 

 eutylos (isopod), Littorina knysnaensis (mollusc), 



Table 3. — Changes in the percentage composition of the food of Diplodus cervinus with length, as assessed by the 

 comparative feeding index (CFI) and occurrence (Occ.) methods. In the case of the latter, all values exceeding 30% 

 have been italicized in order to emphasize those food items which contribute maximally to the diet ( — = absent). 



Size classes (mm) 

 10-20 20-35 35-50 50-75 75-100 100-135 



Taxon CFI Occ. CFI Occ. CFI Occ. CFI Occ. CFI Occ. CFI Occ. 



Chlorophyta — — — — 4.6 12.5 — — — — — — 



Rhodophyta __________1.9 16.7 



Polychaeta 0.2 25 3 8 33.3 17 6 50 17 2 72 4 11.4 18.0 65.4 82.3 

 Crustacea 



Amphipoda 4.1 25 10 33.3 4 25 65 7 74 9 27 6 45 5.8 33.3 



Ostracoda — — 02 22 2 — — — — 0.6 9.0 — — 



Harpacticoid copepoda 56.5 100.0 47,6 77 8 16.5 87.5 2.2 51.7 0.1 9.0 — — 



Isopoda — — 10.0 44.4 4.2 25.0 1.5 20.7 11.0 27.0 1.7 16.7 



Cirripedia (nauplii) — — — — — — 0.5 6,9 — — — — 



Macrura — — 4 7.2 44.4 53.2 50,0 — — 1.0 9.0 — — 



Tanaidacea — — — — — — 0.2 6.8 — — — — 



Mysidacea — — — — — — 0.1 3.4 — — — — 



Insecta 39 50.0 2.2 55.6 4 12.5 — — — — — — 



Mollusca — — — — — — — — 0,4 9 1.9 16.7 



Trochophore larvae 0.2 25.0 — — ___ — ___ — 



Unidentifiable fragments — — — — 3.1 50.0 12.6 79.3 47.9 36.0 23.3 33.3 



No. of fish examined 4 9 8 29 11 6 



Average no of points 

 allotted per stomach 8.3 19.3 8.0 10.0 6.4 11.1 



396 



