Hamilton and Konar: Implications of substrate complexity and kelp variability for Alaskan nearshore fisfi communities 



195 



northern edge of their range are subject 

 to wide fluctuations in all of these factors, 

 as well as wide inter-annual variation in 

 intensity and duration of seasonal factors. 

 It is these extremes that make studying 

 these habitats difficult or impossible dur- 

 ing all but summer months and result in 

 the paucity of consistent seasonal data in 

 northern Pacific systems. 



Aerial surveys of kelp beds in Kache- 

 mak Bay during three consecutive sum- 

 mers (2000-2002) showed significant dif- 

 ferences in size, location, and presence of 

 Nereocystis canopy (Schoch and Chenelot, 

 2004), illustrating great interannual vari- 

 ability that may be apparent on relatively 

 short temporal scales. Such variability 

 was also observed in the present study, in 

 that three of five sites originally contain- 

 ing canopy kelp did not recruit Nereocystis 

 juveniles the second summer. Although 

 this canopy kelp species is considered an 

 annual, we observed Nereocystis individu- 

 als reproducing into a second summer. 



Our findings of relatively more fishes 

 inhabiting Nereocystis beds than under- 

 story-only kelp beds indicates that areas 

 characterized by enhanced Nereocystis 

 growth may have greater fish densities. In 

 one northern California study, densities of 

 kelp greenling in Nereocystis beds were 

 four times greater than in the present 

 study (Bodkin, 1986). Nereocystis beds in 

 California were similarly more important 

 to rockfishes (Bodkin, 1986; Love et al., 

 1991) than understory kelp alone. How- 

 ever, the existence of high understory kelp 

 densities in the canopy-containing sites 

 may be of greater importance to fishes 

 than the canopy itself. In our study sites, 

 both the greenlings and grouped fishes were positively 

 associated with densities of annual understory. In addi- 

 tion, fishes in the present study were usually observed 

 in close association with the understory and substratum 

 as has been typical in other south-central Alaska stud- 

 ies (Rosenthal-, Dean et al., 2000). The perennial-domi- 

 nated understory of south-central Alaska kelp beds may 

 provide a degree of habitat stability for some fishes for 

 at least part of the year. 



It is difficult to account for all factors influencing a 

 natural system, particularly without knowing the re- 

 cent history of the community. Because little is known 



^ Rosenthal, R. J. 1979. A preliminary assessment of compo- 

 sition and food webs for demersal fish assemblages in several 

 shallow subtidal habitats in lower Cook Inlet, Alaska, 58 p. 

 In Final report by Dames and Moore, Inc., 800 Cordova 

 Street, Suite 101, Anchorage, AK 99501. for Alaska Depart- 

 ment of Fish and Game. Commercial Fisheries Division, 

 211 Mission Rd., Kodiak, Alaska 99615. 



about interactions between kelp and fish communities 

 and their natural variability in south-central Alaska, 

 investigation of more obvious, small-scale processes 

 over an entire year is necessary. Physical factors, such 

 as size of the kelp beds and related edge effects of the 

 habitat, salinity fluctuations and freshwater runoff, 

 degree and direction of exposure to light and tidal cur- 

 rents, and the frequency of storm events may play a sig- 

 nificant role in structuring these dynamic communities. 

 In addition, biological factors that may influence algal 

 community structure include inter- and intra-species 

 competition and herbivory. A growing body of evidence 

 points to the importance of temporal and spatial scales 

 in ecological processes (i.e., Dayton and Tegner, 1984; 

 Wiens and Addicott, 1986; Foster, 1990). The structur- 

 ally complex kelp beds surveyed in the present study 

 appear to provide critical habitat throughout the year 

 for greenling species. However, this habitat is also sea- 

 sonally important to rockfishes and codfishes (both 

 adult and juvenile). 



