Ecology of the northern creek chub, Semotilus atromaculatus atromaculatus (Mitchill), in the Mink River, Manitoba

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Moshenko, R. W.
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Northern creek chub were most abundant in the middle zone (gradient of 7 m/km) of the Mink River. In spring, adults (Age 3+) inhabited shallow water environments (current > 15 cm/sec, depth < 25 cm) and after spawning moved into slower and deeper waters. Juveniles (age 1-2) were dispersed throughout moderately deep pools and channels (current 0-30 cm/sec, depth 25-50 cm) from spring to early fall. Age 0 fish were found mostly in slow shallow water environments throughout summer. In October, all age classes moved into the deepest sheltered pools (current 0-15 cm/sec, depth > 50 cm, overhanging cover > 10%) where they apparently overwinter. These seasonal changes in abundance between environments were confirmed by following the movements of marked fish. Diet of creek chub was highly variable due to seasonal differences of avialability of food resources. Small chub fed mostly on aquatic insect larvae and terrestial insects, while larger fish ( > 50 mm) utilized fewer but larger food items. Food varied from aquatic insect larvae in spring, brook stickle-back (Culaea inconstans) in early summer, crayfish in late summer, to frogs and fish in autumn. Males attain sexual maturity at age IV and live to age VI, females at age III and live to age V. Adult sex ratio was 1.5 females per male. Spawning occurred during a two-week period starting in mid May when the water temperature first reached 14 C. Males built nests in the gravel substrate of shallow channel environments. Estimates of fecundity were correlated with fork length. Total mature ova per female varied from 1146 - 7539