FISHERY BULLETIN: VOL. 71, NO. 4 



Ninespine sticklebacks from Lake Superior 

 grow as large, or larger, than those reported in 

 other areas. The most comprehensive growth 

 calculations on the ninespine stickleback prior 

 to this study was done by Jones and Hynes 

 (1950) on a population in a small English 

 stream. They found fish reached only 37 mm 

 in 1 yr and 46 mm in 3 yr. The largest fish re- 

 corded was 55 mm. These fish were in direct 

 competition with a population of threespine 

 sticklebacks. Nelson (1968b) found the largest 

 fish in a northern Indiana lake to be 67.3 mm. 

 Bertin (1925) and Leiner (1934) both record 

 European ninespine sticklebacks over 80 mm, 

 but Blegvad (1917) found none over 50 mm 

 in Danish brackish waters. McKenzie and 

 Keenleyside (1970) report fish up to 75 mm in 

 Lake Huron. The formula, TL = 1.14SL, was 

 calculated from 300 Lake Superior fish and 

 used to convert reported SL (standard length) 

 to TL (total length) for these comparisons. 



Walford (1946) proposed a transformation 

 of growth data to be expressed as a straight 

 line described by the equation: 



u + 1 



= Loo (l-K) + KL 



f 



where 



Li oc 



K 



body length at age t + 1 

 body length at age t 

 ultimate length 

 slope. 



The ultimate length is found graphically 

 where the Walford line intersects a line drawn 

 at 45° through the origin of the graph and is 

 theoretically the greatest length a fish of the 

 population will attain. The slope of the line, K, 

 indicates the decrease in growth rate. 



Walford lines were plotted for Apostle Is- 

 lands sticklebacks from stations 2 and 3 (Figure 

 7). Means of stations 2 and 3 grand average 

 calculated lengths at each annulus were used to 

 combine station data for each sex. 



Calculated values were: 



The ultimate length for males is less than ex- 



20 30 40 50 60 70 80 90 

 LENGTH AT AGE t (mm) 



Figure 7. — Walford lines for Apostle Islands ninespine 

 sticklebacks. Short dashed line, males; long dashed hne, 

 females. 



pected from what is known about male length 

 frequency (Table 4). This is probably due to 

 the small number of points used because of the 

 short life span. More points can be included 

 for the female relationship, and the ultimate 

 length is reasonable. 



Growth in Weight 



Plots of weight against length were made for 

 males and females by calculating average weights 

 for fish at 1-mm intervals. Weights for females 

 in the mature size range were less than male 

 weights. The cause for this was the abrupt drop 

 in weight of females which had just spawned, 

 since the mature female gonad accounts for up 

 to 10% of total fish weight. After females collected 

 in late June and July were omitted from the 

 length-weight plots, the lines for males and 

 females appeared similar. 



Analysis of covariance showed slope, and in- 

 tercept differences were nonsignificant at the 



0.05 level (Fi,745 = 2.71 and Fi,746= 1-36, res- 

 pectively), and the data were pooled to calcu- 

 late a length-weight relationship. The resultant 

 regression included 748 fish and was described 

 by the formula: 



1046 



