FISHERY BULLETIN: VOL. 70, NO. 1 



METHODS 



Sampling of zooplankton was initiated in mid- 

 1969, using a 0.25 m- mouth area cylinder-cone 

 net with 100 micron mesh aperture, hauled ver- 

 tically from 20 m or 50 m. The samples were 

 collected at infrequent intervals during 1969 and 

 the first 14 weeks in 1970; thereafter vertical 

 net hauls were made at two locations at least 

 once every 4 days until the first week of No- 

 vember. Additional vertical net hauls were 

 made once or twice each month from the lake 

 bottom, 200 m, to the surface. Miller nets (Mil- 

 ler, 1961) with 0.01 m- mouth area and 100 mi- 

 cron mesh aperture were used at weekly intervals 

 during the period June through August and 

 thereafter at monthly intervals to determine the 

 area] and vertical distribution of zooplankton. 

 The areal sampling at 18 locations along the 

 lake consisted of 5 min oblique tows from 20 m 

 to the surface while underway at 2 m/sec. The 

 daylight vertical distribution of zooplankton was 

 monitored at 18 depths between the surface and 

 65 m by making three consecutive tows each with 

 six Miller nets at 2 m/sec at one location. Ad- 

 ditional tows were made to sample other depths 

 and also at other periods of the day. Details 

 of the sampling and sampling locations are re- 

 ported elsewhere (Kennedy et al., 1971"). 



' Kennedy, 0. D., K. Stephens, R. J. LeBrasseur, T. R. 

 Parsons, and M. Takahashi. 1971. Primary and sec- 

 ondary productivity data for Great Central Lake, B.C., 

 1970. Fish. Res. Board Can., Manuscr. Rep. No. 1127, 

 379 p. 



In the analyses of samples special effort was 

 made to maintain up to date species counts and 

 measurements for comparison with other events 

 as they were occurring in the lake. The common 

 zooplankton constituents were identified, mea- 

 sured into size categories, and counted from an 

 aliquot of the total sample ; fractions of 1/50 or 

 1/100 using a Stempel pipette were used de- 

 pending upon the sample size. The size cate- 

 gories (length in microns) reported in Table 1 

 were based upon individual measurements for 

 different stages of development of the respective 

 species. It is to be noted that the lengths refer 

 to mean sizes of organisms during the spring 

 and summer growing period. Individual length 

 measurements for the different species and for 

 diflferent times of the year may be found in the 

 MS data report (see footnote 2). 



Species counts in vertical net hauls are re- 

 ported as number per m^, in oblique and hori- 

 zontal tows as number per m^ In this report, 

 unless otherwise indicated, counts all refer to 

 numbers of individuals which fall within the size 

 range occupied by mature (Stage VI) copepods 

 and egg-bearing cladocera; these were usually 

 the two largest size groups for the species re- 

 ported in Table 1. 



RESULTS 

 SPECIES 



Table 2 lists the species of zooplankton which 

 have been found in Great Central Lake. Addi- 

 tional species may be present as minor constitu- 



Species 



Table 1. — Zooplankton size ranges for species sorting in Great Central Lake. 



Group 



III 



IV 



VI 



VII 



26 



