Robards et a\ : Variation in fish communities of lower Cook Inlet, Alaska 



969 



100 



75 



diversity, richness, and evenness all 

 increased on the second set, at both 

 tidal states, because of a decrease 

 in dominant species (Table 4). Be- 

 cause species composition of seine 

 catches did not differ significantly 

 between consecutive sets at high 

 and low tidal states (Mann-Whitney 

 rank sum test), it appears that one 

 set is adequate for assessing species 

 richness and dominance, as sug- 

 gested by Allen et al. (1992) 



Twenty-eight species were repre- 

 sented in high tide sets and the 

 overall CPUE was 425, in contrast 

 to 38 species and a CPUE of only 

 191 at low tide. This difference prob- 

 ably resulted from a scarcity of 

 pricklebacks (Stichaeidae), gunnels 

 (Pholidae), and sculpins at high 

 tide. The species difference in 

 catches in part accounted for the 

 moderate coefficient of similarity 

 (Jaccard's) between tidal states 

 (58% and 61% on sets 1 and 2, re- 

 spectively). Catch composition dif- 

 fered significantly between high 

 and low tides (Mann-Whitney rank 

 sum test; T=2645.P=0.02). Several 

 schooling species (e.g. pink salmon, 

 adult sand lance) and one demer- 

 sal species (great sculpin) showed 

 little disparity in overall CPUE or 

 frequency of occurrence between 

 tidal states (Table 5). These species 

 (or age classes) appeared to remain 

 close to the shore throughout the tidal cycle. Other 

 species (e.g. Dolly Varden, juvenile sand lance) ap- 

 parently moved from deeper waters into the inter- 

 tidal zone at high tide, as shown by the greater fre- 

 quency of capture and CPUE. Although Pacific cod, 

 saffron cod, whitespotted greenling {Hexagraniiuofi 

 stelleri ), sil verspotted sculpin, juvenile great sculpin, 

 and rock sole were caught at both tide levels, these 

 species appeared to remain preferentially in the 

 subtidal zone during high tide (Table 5). Overall, 

 species diversity, richness, and evenness were great- 

 est at low tides (Table 4). 



Geographic comparison of beach seine catches from 

 Kachemak Bay, Chisik Island, and the Barren Islands 



A total of 988 fish representing 24 species were 

 caught in 30 beach seine sets in the warmer (Fig. 2 1 

 nearshore waters around Chisik Island during sum- 



Herring 

 «=1 5,305 



Salmonidae 

 n= 10.278 



Sand lance 

 ^^— Juvenile 



M=87,610 



=^ Adult 



«=5,068 



Pleuronectidae 



M A M J 



.1. 



ASOND FMAMJ 

 Month 



S O N D 



Figure 3 



Sea.sonal variation in CPUE (bars) and frequency of occurrence (lines) of se- 

 lected fish species caught by beach seines in Kachemak Bay. 



mer 1996 (Table 6). Dolly Varden was the most com- 

 mon species; it was present in 63% of the sets and 

 represented 30% of total catch by numbers. In con- 

 trast to Kachemak Bay and the Barren Islands, sand 

 lance were found in only 33% of sets and accounted 

 for only 24% of the catch by number. Snake 

 pricklebacks (Lumpenus sagitta; 12% ) and Pacific cod 

 (8% ) were the next most abundant species. Sculpins 

 and flatfishes were also commonly caught in the sets. 

 A total of 180.232 fish representing at least 12 spe- 

 cies (including 482 unidentified sculpins, 1 uniden- 

 tified flatfish, and 1 unidentified greenling) were 

 caught in 40 seine sets in the somewhat cooler (Fig. 2) 

 nearshore waters at the Barren Islands during sum- 

 mer 1996 (Table 6). Barren Islands catches were 

 dominated by sand lance (predominantly juveniles; 

 Table 6). This species was found in 90% of the sets 

 and represented over 99% of the total catch. Other 

 species commonly found in the sets included Pacific 



