FISHERY BULLETIN: VOL. 71, NO. 4 



(Hubbs and Lagler, 1958). It has also been 

 taken in inland lakes as far south as northern 

 Indiana (Nelson, 1968a), and Moore and Braem 

 (1965) found small numbers in some Lake Sup- 

 erior tributaries. It is a fish of cool, quiet water 

 (Hubbs and Lagler, 1958), and it is generally 

 abundant wherever it occurs in lakes or seas 

 within its range. 



METHODS AND MATERIALS 



The data for the present study were collected 

 in 1967-69 in cooperation with the BCF Great 

 Lakes Biological Laboratory, Ann Arbor, 

 Mich. 4 



Experimental sampling operations were con- 

 ducted aboard the BCF research vessel Siscowet 

 in conjunction with sampling by BCF in the 

 Apostle Islands, Lake Superior. The main ob- 

 jectives of the BCF program were to enumerate 

 juvenile lake trout, monitor spawning success, 

 measure the impact of the lamprey on the trout 

 population, and contribute research on the biol- 

 ogy of other species in the lake. 



One of the main objectives of the ninespine 

 stickleback study was to defiine ecological re- 

 lationships between the stickleback and other 

 fish, particularly the lake trout. With this ob- 

 jective in mind, and within the limitations of 

 the ongoing BCF program, sampling was es- 

 sentially confined to seven stations within the 

 Apostle Islands (Figure 1). Five of these sta- 

 tions (12, 24, 44, 75, and 86) were sampled 

 regularly as juvenile trout index trawl stations 

 and yielded data pertinent to questions of 

 species interaction. Comparatively, they sup- 

 ported varying numbers of trout and stickle- 

 backs, and historically they comprised the 

 known lake trout nursery areas within the 

 islands. At present, only stations 75 and 86 

 support good populations of juvenile trout. 

 The other two stations, 2 and 3, support abun- 

 dant midsummer stickleback populations and 

 comprise shallow, inshore areas. These two 

 stations were outside the regular BCF trout 

 index sampling routine and required special 

 sampling. Collections from these stations pro- 



ChOEVIL'S 

 ROCKY 



SEAR 





.NORTH 

 ' TWIN 



SOUTH , , 

 TWIN SVCAT 



IRONWOOD 



rORK C/°TTER \4 



V ^RASPBERRY J) 



_^ y ^MANITOU 



~srocKTON 



^ Presently the Great Lakes Fishery Laboratory, U.S. 

 Bureau of Sport Fisheries and Wildhfe. 



Figure I. — Sampling stations in the Apostle Islands. 

 Blacked out area in inset shows location of these islands 

 in Lake Superior. 



vided data for stickleback age and growth 

 studies and supportive information about dis- 

 tribution and relative abundance. 



A small semi-balloon otter trawl with a 4.7-m 

 headrope, 38.1-mm mesh body (stretched meas- 

 ure), and 12.7-mm mesh cod end was used 

 from a 16-ft aluminvim boat with a 40-horse- 

 power outboard motor at stations 2 and 3. A 

 large trawl of the same type (9.4-m headrope, 

 50.8-mm body, and 12.7-mm cod end) was 

 used aboard the Siscowet for deepwater trawl- 

 ing. Adult lake trout were sampled with ex- 

 perimental gill nets ranging from 1.3- to 7.6-cm 

 mesh (bar measure). Zooplankters and stickle- 

 backs examined for stomach contents were col- 

 lected with a sled-borne plankton net with a 

 1-m square mouth and 0.158-mm mesh, the 

 bottom edge of which ran approximately 30 cm 

 above the lake bottom. Temperature profiles 



1040 



