962 



Abstract.— Nearshore and shelf fish 

 communities were studied in three ar- 

 eas of lower Cook Inlet, Alaska: the 

 Barren Islands (oceanic and well-mixed 

 waters), Kachemak Bay (mixed oceanic 

 waters with significant freshwater run- 

 offi, and Chisik Island (estuarine wa- 

 ters). Fish were sampled with beach 

 seines ^n = 413 sets) and midwater 

 trawls (n=39sets). We found that lower 

 Cook tnlet supported a diverse near- 

 shore fish community of at least 52 spe- 

 cies. Fifty of these species were caught 

 in Kachemak Bay, 24 at Chisik Island, 

 and 12 at the Barren Islands. Pacific 

 sand lance dominated Barren Islands 

 and Kachemak Bay nearshore habitats, 

 comprising gS^f and Tl'/f of total indi- 

 viduals, respectively. The nearshore 

 Chisik Island fish community was not 

 dominated by any one species; instead 

 it exhibited higher diversity. These spa- 

 tial differences appeared linked to lo- 

 cal oceanographic regimes and sedi- 

 ment influx. Analysis of historical data 

 revealed that the nearshore Kachemak 

 Bay fish community changed signifi- 

 cantly between 1976 and 1996, show- 

 ing increased diversity and abundance 

 in several taxa, notably gadids, salmo- 

 nids, pleuronectids, and sculpins. 

 Decadal differences appeared to be re- 

 lated to large-scale climate changes in 

 the North Pacific. Catches of most taxa 

 peaked in May-August, and were low 

 during other months of the year Sev- 

 eral species were present for only part 

 of the summer. Species composition of 

 seine catches differed significantly be- 

 tween consecutive high and low tides, 

 but not between consecutive sets or 

 years. Midwater trawls took 26 species, 

 14 of which were present in Kachemak 

 Bay, 19 near Chisik Island, and 7 at the 

 Barren Islands. Community structures 

 in shelf and nearshore waters were 

 similar: diversity was high and abun- 

 dance low at Chisik Island, whereas a 

 few abundant species dominated at 

 both Kachemak Bay and the Barren 

 Islands. In addition, the low fish abun- 

 dance near Chisik Island appeared to 

 be related to declining seabird numbers 

 at this colony. 



Temporal and geographic variation in 



fish communities of lower Cook Inlet, Alaska 



Martin D. Robards 



John F. Piatt 



Alaska Biological Science Center 



Biological Resources Division 



U S Geological Survey 



101 1 E Tudor Road 



Anchorage. Alaska, 99503 



E-mail address (for M D Robards) Martin_Robardsausgsgov 



Arthur B. Kettle 



Alaska Maritime National Wildlife Refuge 

 US- Fish and Wildlife Service 

 2355 Kachemak Bay Drive 

 Homer, Alaska, 99603 



Alisa A. Abookire 



Alaska Biological Science Center 

 Biological Resources Division 

 U S Geological Survey 

 101 1 E Tudor Road 

 Anchorage, Alaska, 99503 



Manuscript accepted 24 March 1999. 

 Fish. Bull. 97(41:962-977 (1999), 



Dramatic changes in seabird anti 

 marine mammal populations in the 

 Gulf of Alaska have been linked to 

 shifts in abundance and composi- 

 tion of forage fish stocks over the 

 past 20 years (Piatt and Anderson, 

 1996; Anderson et al.M, Coincident 

 with cyclical fluctuations in seawa- 

 ter temperatures, abundance of sev- 

 eral key forage species, including 

 capelin (Mallotus villosus), prickle- 

 backs (mostly Lumpenella longiro- 

 stris), and Pacific sandfish {Tricho- 

 don trichodon) declined precipi- 

 tously in the late 1970s. Meanwhile 

 populations of large predatory fish, 

 including walleye pollock ( Theragra 

 chalcogramma). Pacific cod (Gadus 

 macrocephalus). and several pleuro- 

 nectids increased dramatically. Cor- 

 respondingly, seabird diets shifted 

 from mostly capelin in the 1970s to 

 mostly Pacific sand lance (Ammo- 

 dytes hexapterus) and juvenile pol- 

 lock by the late 1980s (Piatt and 

 Anderson, 1996). Furthermore, a 



variety of seabirds and marine 

 mammals exhibited signs of food 

 stress during the 1980s and early 

 1990s (Piatt and Anderson, 1996), 

 Inferences about changes in Gulf of 

 Alaska fish communities have been 

 based on a limited number of site- 

 specific long-term studies (e.g. 

 Anderson et al.' ); however, evidence 

 is mounting that suggests these 

 changes were wide-spread through- 

 out the region ( Francis et al. , 1998 ). 

 The importance of inshore marine 

 habitats as nursery areas for juve- 

 niles of many marine fish species 

 has been well reported (Poxton et 

 al., 1983; Orsi and Landingham, 

 1985; Bennett, 1989; Blaber et al., 

 1995; Dalley and Anderson, 1997), 

 Studies in other parts of the world 



Anderson, P. J., S.A. Payne, and B. A. 

 Johnson. 1994. Multi-species dynamics 

 and changes in community structure in 

 PavlofBav, Alaska 1972-1992. Natl. Mar 

 Fish. Serv., NOAA, Kodiak, Alaska. 

 Unpubl. manuscript, 26 p. 



