11). The significant results in 1963 were due to a few 

 very large catches in the middle and late time 

 periods in surface tows only. No consistent differ- 

 ences are apparent. 



Threespine Sticklebacks 



Threespine sticklebacks were captured with tow 

 nets and all other suitable gear in all basins of the 

 Naknek system (Table 3). In general, the areas that 

 yielded only few juvenile sockeye salmon — North 

 Arm, Grosvenor Lake, and Brooks Lake — also 

 yielded only few threespine sticklebacks. 



The outstanding feature of the abundance of three- 

 spine sticklebacks in the tow net catches is the varia- 

 tion from one sampling period to the next. The abun- 

 dance of threespine sticklebacks during each summer 

 from 1961 to 1963 in the West End (a region of great 

 abundance) by sampling area (Fig. 10) illustrates this 

 point. No significant differences in abundance with 

 time, depth, or area appeared in the split-plot analysis 

 of variance of data collected in 1962-64 in Coville 

 Lake, the lake for which most data are available 

 (Table 1 1). Catches of threespine sticklebacks resem- 

 ble those of the pond smelt (Fig. 9) in that the abun- 

 dance in tow nets fluctuated independently in adjacent 

 sampling areas. 



The catches of threespine sticklebacks increased 

 during the summer in some lakes and were fairly uni- 

 form through the summer in others. Only a few 

 threespine sticklebacks were captured with tow nets in 

 the first half of July in Coville Lake, Iliuk Arm. and 

 South Bay, but in August they were taken in moderate 

 numbers in these basins. A similar increase in catches 

 during the summer occurred in the lakes where they 

 were never taken abundantly, i.e., Grosvenor Lake. 

 North Arm, and Brooks Lake. In the areas of rela- 

 tively great abundance, Northwest Basin and West 

 End, this species was about as numerous in catches 

 the first half of July as in late August. At Karluk Lake 

 on Kodiak Island, in 1961 and 1962, threespine 

 sticklebacks were abundant in the littoral areas and 

 virtually absent in the pelagic areas in early July, but 

 by summer they were mostly in the pelagic areas." A 

 similar shift to pelagic areas was found in Lake Nerka 

 of the Wood River system (Burgner, 1962). 



Age threespine sticklebacks were rare in tow net 

 catches until late August and even then they were so 

 small that they could pass easily through the smallest 

 mesh of the net unless their spines were erect. 



Ninespine Sticklebacks 



Ninespine sticklebacks and threespine sticklebacks 

 commonly occurred in the same catches and, in gen- 

 eral, the observations on threespine sticklebacks apply 

 to ninespine sticklebacks. The average abundance of 



6 B. Drucker. National Marine Fisheries Service. Auke Bay 

 Fisheries Laboratory. Auke Bay, AK 99821, pers. comm. 



377 



4 37 



3 



o 



340 

 320 

 300 

 280 

 260 

 240 

 2 20 



IE 

 UJ 

 O- 



I 200 

 tn 



o 180 



tc 



ui 



2 160 



Z 



140 



120 



100 



60 



60 



40 - 



20 - 



•CI 

 • C -2 



I I I 



234 1234 1234 



1961 1962 1963 



SEMIMONTHLY TIME PERIOD 



Figure 9. — Mean number of pond smelt per standard tow in Coville 

 Lake (units C-l and C-2) by semimonthly time periods, 1961-63. Time 

 periods are: 1 — July 1-15; 2 — July 16-31; 3 — August 1-15; 4 — August 

 16-31. 



ninespine sticklebacks in the tow nets was markedly 

 lower in July than in August both in Coville Lake, 

 where moderate numbers were captured, and in Iliuk 

 Arm, South Bay, and Northwest Basin, where only a 

 few were captured. Four of the five significant differ- 

 ences in abundance shown in the split-plot analysis for 



24 



