FISHERY BULLETIN: VOL. 79, NO. 4 



Table 4.— SGIO: Changes in selectivity with fish size considered by principal prey taxon. Range offish size is divided 

 to maximize heterogeneity between size intervals for each principal prey taxon as described in text. 



'NS = not significant; •••P<0.001;"P< 0.01 ;'P<0.05. 



^Ali members of the same family pooled. 



^Positive identification of species difficult for this species, pooled with Mediomastus californiensis . 



"Species not found in box core, calculation based on numbers of representatives of same genus. 



^Species pooled with Pectinaria belglca. 



^No representative of genus in box core — no eiectivity values calculated. 



'Based on frequency of occurrence in fish compared with numbers of ophiuroids found in box core. 



SG29, out of 35 principal prey taxa (taxa occurring 

 in at least 10% of stomachs containing food), 27 

 showed significant changes in frequency of occur- 

 rence. Five types of prey frequency patterns were 

 apparent for these 27 prey over the size range of 

 fish sampled, 11-42 cm. Examples are shown in 

 Figure 2. 



The first prey pattern, typified by the polychaete 

 Decamastus gracilis (I), reflects prey which oc- 

 curred at low frequencies in diets of small-sized 

 fish (11-20 cm) and at increasing frequency in diets 

 in intermediate-sized fish (21-30 cm), and which 

 remained approximately constant at that same 

 frequency in the diets of large-sized fish (30-42 cm) 

 (Figure 2). Other taxa for which this pattern 

 existed include the Ophiuroidea; polychaetes 

 Aedicira antennata, Spiophanes berkeleyorum , the 

 Sigalionidae, Ninoe gemmea, Spiophanes sp.; and 

 the Scaphopoda, many of which are sessile or 

 motile outside of tubes and surface feeders. 



The second prey pattern describes taxa which 

 occurred at relatively high frequency in diets of 

 small-sized fish and occurred at decreased fre- 

 quency in diets of intermediate- and large-sized 

 fish; e.g., the small tubed polychaetes Myriochele 

 oculata (II) and M. heeri, the amphipod Har- 

 piniopsis fulgens, and small ampharetid 



polychaetes. The cumacean Eudorella pacifica, 

 pelecypod group Adontorhina cyclia-Axinopsida 

 serricata, and polychaete Nephtys sp. also oc- 

 curred often in diets of intermediate-sized fish, but 

 occurred at low frequency in diets of large-sized 

 fish. 



The third prey pattern is depicted by a hump- 

 shaped curve, in which case a prey taxon occurred 

 at low frequencies in diets of small- and large- 

 sized fish but at relatively high frequencies in 

 diets of intermediate-sized fish. Many principal 

 prey taxa belong to this category, including the 

 polychaetes Anaitides groenlandica (III), 

 Aricidea ramosa, Sternaspis fossor, Paraonis 

 gracilis, Apistobranchus ornatus, Cossura sp., and 

 Terebellides stroemii. 



The fourth prey pattern reflects increasing prey 

 frequency with increasing fish size. Prey taxa fol- 

 lowing this pattern included many larger tubed, 

 surface and subsurface feeding polychaetes: 

 Nothria elegans (IV), Pectinaria californiensis, 

 Glycera capitata, Pista cristata, and the Maldan- 

 idae. 



The fifth prey pattern includes prey whose fre- 

 quency of occurrence in diets did not change sig- 

 nificantly over the entire size range of fish sam- 

 pled; e.g., polychaetes Lumbrineris latreilli (V), 



754 



