CHRISTENSEN: TROPHIC RELATIONSHIPS OF SPARID FISHES 



lOOi 



80 



60 



40 



20' 



Ottiers 



■, rww~-- | Ti ll I N , i rn— --i ^ - - . .T ^ 



Length (mm) 5 15 20 25 35 50 165 



No of Fish 72 36 K 12 6 9 



Figure 7. — Changes in diet with length of Diplodus sargus, 

 collected between August and December 1975, as shown by the 

 comparative feeding index. Food items included in Others are 

 the same as for Figure 8, in addition to the unidentified 

 trochophore larva. 



algae, diatoms, chironomid larvae, and hydrozoa 

 as they grow larger. 



Identity of Food 



Diatoms: two species of the genus Licmophora, 

 predominantly L. pfannkucheae , as well as L. 

 ehrenbergii. 



Other algae: the chlorophytan algae of the 



genus Ulua most frequent, although some of the 

 larger size classes also fed on Caulerpa filiformis 

 (50-165 mm: 7.5% in summer and 2.9% in winter), 

 Bryopsis sp., Enteromorpha sp., and Valonia sp. 

 Some rhodophytans taken, including Ceramium 

 sp., Hypnea spicivera, Polysiphonia sp., and 

 Tayloriella spp. 



Harpacticoid copepods: 12 species, only 4 com- 

 mon, identification was not possible. 



Amphipods: 28 species — 7 caprellid species in- 

 cluding Caprella danilevskii, C. penantis, C. 

 scaura, and Caprellina longicollis; Cerapus 

 tubularis; Corophium? acherusicum, and C? 

 triaenunyx; Cymadusa sp.; two Gammaropsis 

 species including G. holmesi; Jassa spp.; 

 Lysianassa ceratina; and L. variegata; two Maera 

 species; Paramoera capensis; Parelasmopus 

 suluensis; two Photis species; Temnophlias sp.; 

 Urothoe sp.; and three unidentified species. 



Isopods: nine species — Cymodocella pustulata, 

 C. siiblevis, Dynamenella huttoni, D. mac- 

 rocephala. Exosphaeroma antikraussi, Gnathia 

 sp., Janiropsis sp., Panathui-a sp., and a Stene- 

 trium species. 



Polychaetes: Dodecaceria pulchra. E alalia 

 triliueata, two Nereis species, an Onuphis sp., and 

 terebellid tentacles most commonly found in the 

 gut contents, as well as Pista sp.. Pumatoleois 

 kraussi, and Serpula vermicularis. 



Ostracods were not identified. 



Table 2. — Changes in percentage composition of the food of Diplodus sargus with length during the period August 



to December 1975, as assessed by the comparative feeding index (CFI ) and occurrence (Occ.) methods. In the case of 



the former, all values greater than 30% have been italicized in order to emphasize those food items which 

 contribute maximally to the diet ( — = absent). 



size classes (mm) 



5^15 15-20 20^55 25-35 35-50 50-165 



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



Chlorophyta 02 42 06 83 2,9 28 6 33 4 50 135 33,3 143 55.6 



Rhodophyta ______ 0,9 33,3 0,8 33,3 — — 



Chrysophyta ______ 0,7 25,0 87 33,3 7,4 11,1 



Hydrozoa — — — — — — — — — — 11 111 



Polychaeta 11 20,8 10,4 47.2 4,0 35 7 14,7 33,3 09 16 7 4.0 22.2 

 Crustacea 



Amphipoda 0.3 6 9 17 27 8 14 1 57 1 2 4 25 6 5 50 62 5 100.0 



Ostracoda 6.0 37 5 5.5 55 6 6 4 64 3 8 16 7 4 16 7 1 111 



Harpacticoid copepoda 67 8 86.1 58.? 94.4 47.6 100.0 29 6 83.3 176 100.0 — — 



Isopoda 1.0 16 7 2 1 25 3 4 42 9 3 25 6 9 50 9 8 44 4 



Brachyura 0.1 5.6 - - 2 14.3 2 8 3 — — 2 111 



Cirnpedia 8.8 36 1 139 66 7 215 42 9 13 83 — — - - 

 Leptostraca — — 03 56 — — — 

 Tanaldacea — — — — 2 14 3 — — 



Macrura — — — — 7 71 — 



Insecta 8 8 36 1 4 8 27 8 5 214 3 8 33 3 37 2 50 — — 



Moliusca — — — — — — — — — — 0311,1 



Trochophore larvae 4.6 30.6 0.3 5.6 16 14 3 12 83 — — — — 



Unidentifiable fragments 1.3 20.8 2.3 30.6 2.9 28.6 8.1 41.7 7.5 50.0 0.2 11.1 



No. of fish examined 72 36 14 12 6 9 

 Average no. of points 



allotted per stomach 13.7 17^ 204 12^0 14^8 182 



395 



