Ldbropoulou et aL: Habitat selection and diet of luvenile Pagrus pagrus 



499 



ceans, polychaetes, and fish) (Table 4). Polychaetes 

 predominated in terms of percentage by number 

 (35.1%), whereas decapods made up 54.2% of the to- 

 tal weight of stomach contents. Small crustaceans 

 were also consumed in fairly large proportions by 

 number (25.2% ), but their contribution by weight was 

 minor. Fish were a considerable dietary staple by 

 weight ( 23.5% ), although their contribution by num- 

 ber (6.7%) was comparatively low. At the species level, 

 the thalassinid Upogebia tipica, the caprellid Phtisica 

 marina, and the sedentary polychaete Terebellides 

 stroemi were the most exploited prey. Among fish prey, 

 Gobius niger was the species having greatest contribu- 

 tion in the diet of red porgy. Diet breadth was found to 

 be 0.39 (±0.01) for the numerical abundance and 0.31 

 (±0.07) for the biomass of the prey species. 



Food in relation to Fish size 



Although the contribution of prey groups, in terms 

 of both number and weight, varied with fish size 

 (Table 4), there were significant differences only be- 

 tween ingestion of small crustaceans (^'^=28. 46, 

 P<0.001), U. tipica (x^=15.38, F<0.001), and 

 Liocarcinus maculatus (X'=8.24, P<0.01). Small crus- 

 taceans occurred in the younger specimens (0 size 

 class), whereas U. tipica and L. maculatus occurred 

 in greater percentages in the diet offish correspond- 

 ing to size classes 1 and 2. The total amount of food 

 ingested varied significantly among size classes 

 (P=51.95, P<0.001). Pair-wise group comparisons 

 showed three homogeneous groups; the mean con- 

 sumption rate per individual (i.e. g food/size class) 



