PRELIMINARY EVIDENCE FOR FRACTIONAL SPAWNING BY THE NORTHERN REDBELLYDACE, PHOXINUS-EOS

Field data on reproductive ecology of the Northern Redbelly Dace at Cl ear Lake, Ontario, over two years, 1984 and 1985, suggested that this species was a multiple or fractional spawner. The spawning season was long (mid-June to mid-August) and the density of larvae was low. We te sted the hypothesis that the extended spawning season was caused by la ter maturation of small fish. Gonado-somatic indices for large and sma ll dace showed the same seasonal pattern (0.15 end-June, and 0.07 end- July). Fecundity (mature eggs) estimates showed inconsistent relations hips with lengths (r2 = 0.01-0.72) and wide fluctuations in ranges, bo th of which are characteristics of fractional spawners. Egg diameter f requencies within the ovaries were bimodal, lending further support to our supposition that even in the more northern portion of its range, Phoxinus eos is a fractional spawner.