GRISWOLD and SMITH: LIFE HISTORY OF NINESPINE STICKLEBACK 



Table 11. — Average catch per 1-mile trawl tow (CPE) at various index stations in the Apostle Islands 

 calculated from Bureau of Commercial Fisheries index trawling data, 1965 through 1968. 



' Taken from: Bailey, R. AA. (chairman). 1970. A list of common and scientific names of fishes from the United 

 States and Canada. Am. Fish. Soc, Spec. Publ. 6, 149 p. 



trawl was towed through the area. This allowed 

 estimation of minimum density. 



Catches with this trawl were highly variable 

 even though visual sightings, during both day 

 and night, indicated fish were quite evenly 

 distributed. Light obviously influenced catch 

 because no fish were caught during the day- 

 light hours even though they could be seen. 

 Moonlight intensity probably influenced the 

 catch, as did wind direction and intensity, by 

 adversely affecting the efficiency of the samp- 

 ling operation. It is entirely possible these 

 factors also influenced catches by Siscoivet in 

 deeper waters. 



Summer nighttime trawl tows on the sandy 

 beach, station 2, usually caught from 300 to 

 2,500 sticklebacks in V4 mile (Table 12). These 



Table 12. — Catches of sticklebacks in 1967 and 1968 on 

 the sand beach of station 2 during the night using the 

 4.7-m otter trawl and outboard. 



values correspond to minimum density estimates 

 of 0.18 to 1.49 fish per square meter. Sticklebacks 

 were the only species caught in the area during 

 their summer concentration, but johnny darters, 

 Etheostoma nigrum Rafinesque, pygmy white- 

 fish, Prosopium coulten (Eigenmann and Eigen- 

 mann), trout-perch, and smelt were found there 

 in spring and fall. 



REPRODUCTION 



Maturation 



The gonads of 401 spring-collected fish from 

 which otoliths were extracted were analyzed 

 for maturity. In addition, 34 male and 72 female 

 I annulus fish (determined from length-frequen- 

 cy histograms) were included in maturity studies. 



Both male and female sticklebacks matured 

 over 3 yr (Table 13). A greater percentage of 

 males matured at age 1, with large size being a 

 prerequisite for early maturity. By age 2, nearly 

 all fish of each sex were sexually mature, but 

 neither sex was 100% mature until the third 

 year of life. Jones and Hynes (1950) found 99% 

 of a sample of European ninespine sticklebacks 

 mature with 2 yr. 



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