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Fishery Bulletin 88(2), 1990 



Low-relief rocky reefs and sand/eelgrass were tem- 

 porary habitats primarily utilized during the summer, 

 coincident with summer vegetation growth. Presum- 

 ably rockfishes utilize these habitats when structure 

 and prey availability are highest and subsequently 

 move to other more suitable habitats (Matthews In 

 press). Although rockfish densities were low, these 

 habitats cover considerably more area than artificial 

 reefs or high-relief rocky reefs in Puget Sound, and 

 thus are important to rockfish. 



The highest densities of rockfishes were observed on 

 the artificial reefs, primarily 80-200 mm quillback rock- 

 fish. Artificial reefs had high densities of 80-200 mm 

 quillback rockfish throughout the year, although some 

 fluctuations occurred, and high densities of large cop- 

 per rockfish in the fall, winter, and spring. No other 

 reefs surveyed had such high densities of 80-200 mm 

 rockfishes of any species, and it is not known whether 

 this results from higher survival of small (juillback 

 rockfish on artificial reefs. Furthermore, it is puzzling 

 that more large quillback rockfish were not found on 

 the artificial reefs, considering the abundance of 80- 

 200 mm quillback rockfish. Several hypotheses could 

 explain the low numbers of large quillback rockfish on 

 the artificial reefs: (1) Artificial reefs are not suitable 

 habitat for large quillback rockfish, i.e., they leave 

 when they grow large; (2) the fish have not yet grown 

 to the larger size; (3) some factor is preventing the fish 

 from growing; or (4) there is a high mortality of fish 

 once they reach the 200-mm size. I ruled out the pos- 

 sibility that large copper rockfish competitively ex- 

 cluded large quillbacks, as the two species coexist on 

 high-relief natural reefs, although competition may be 

 reduced at high-relief habitats if resources are not 

 limiting. The shortage of large quillback rockfish on the 

 artificial reefs is not depth-related since large quillbacks 

 have been observed at similar depths in other studies 

 (Moulton 1977, Richards 1987) and at HRl and HR2. 

 Again, the lack of large quillback rockfish was not due 

 to fishing pressure: I observed low levels of fishing at 

 both artificial reefs. Furthermore, if fishing pressure 

 was responsible for the lack of large fish, there would 

 be few large copper rockfish. In any case, this apparent 

 refuge for 80-200 mm quillback rockfish should be in- 

 vestigated to determine if rockfish leave once they 

 reach a certain size and eventually contribute to recrea- 

 tional fisheries. Although it has been well established 

 that artificial reefs attract high densities of fish, in this 

 case 80-200 mm quillback rockfish, there is no infor- 

 mation that verifies whether there is adequate food or 

 if growth or mortality is similar to that observed on 

 natural reefs (Ambrose and Swarbrick 1989). 



Year-to-year comparison 



In a 4-year study of kelp-bed fishes in southern Califor- 

 nia, Ebeling et al. (1980) found little annual variation 

 in numbers of bottom assemblages, including rock- 

 fishes. Although my study demonstrated significant 

 seasonal changes within a habitat (artificial reefs, low 

 relief, sand/eelgrass), when analyzed between seasons 

 there were few differences between years, with the ex- 

 ception of YOY. Ebeling et al. (1980) suggested that 

 the low annual variation in kelp-bed fish assemblages 

 was characteristic of stable communities in predictable 

 environments. Although more recent work (Ebeling 

 and Laur 1988) demonstrated the dramatic effect 

 storms can have on fish populations, Puget Sound is 

 a relatively protected environment not subjected to 

 open ocean waves and surge. Thus year-to-year varia- 

 tion in Puget Sound rockfish populations may be small. 



Species comparison 



Copper rockfish occurred on all habitats and can be con- 

 sidered a habitat generalist. Large copper rockfish 

 were observed on all four habitats, although they left 

 the artificial reefs in the summer and moved into 

 shallower low-relief and sand/eelgrass areas. Buckley 

 and Hueckel (1985) also noted a seasonal decrease of 

 copper rockfish densities during the summer on Gedney 

 Island artificial reef in central Puget Sound, and 

 highest densities were noted during the fall and winter. 

 They speculated rockfish movement was in response 

 to prey occurrence (surfperch). Moulton (1977) specu- 

 lated that copper rockfish move to deeper water dur- 

 ing the fall in northern Puget Sound due to seasonal 

 depth preference or prey availability. Turbulence pre- 

 sumably does not contribute to movement; in Puget 

 Sound most water motion on the bottom is from cur- 

 rents, not surge or turbulence, and water motion is 

 similar in the summer and winter. In the summer, cop- 

 per rockfish utilized several habitats: high-relief rocky 

 reefs, low-relief reefs, and sand/eelgrass. Their appear- 

 ance on the shallower reefs during the summer and 

 disappearance from the deeper artificial reefs is not 

 simply a shallower depth preference in the summer; 

 copper rockfish were observed during the summer at 

 the high-relief reefs even at comparable artificial reef 

 depths. 



Quillback rockfish were more restricted in tlieir dis- 

 tribution when compared with copper rockfish. Similar- 

 ly, quillback rockfish were not as widely distributed as 

 copper rockfish at 12 study sites in the Strait of Georgia 

 (Richards 1987). The small (juillback rockfish were seen 

 in very high densities on the artificial reefs, but infre- 

 quently on other habitats. Large quillback rockfish 

 were primarily seen on high-relief rocky and artificial 



