Limnology of a sink-hole pond with special reference to the Northern Red-Bellied Dace, Chrosomus eos Cope

The life history of the northern red-bellied dace, Chrosomus eos Cope, occurring in a sink-hole pond (Hants Co., Nova Scotia) was studied from January 1976 to January 1977. Limnological conditions in the pond were also examined. Age categories of the dace included year groups O⁺ to III⁺ with the mean lengths for these groups ranging from 25 mm (17-32mm) to 52 mm (48-55mm). During the course of the year the predominant year classes were age O⁺ and I⁺ fish with age II⁺ and III⁺ comprising <25% of the total population. Growth was rapid during the first year (length increment 20mm) while decreasing the following three years (length increment 11, 9 and 7mm respectively). Eggs hatch in ≥ 5 days at 20°C. Larval growth rate was estimated to be 3.5mm/month while young-of-the-year and juveniles exhibited estimated growth rates of 1.5mm/month and 1.0 - 2.5mm/month respectively. The length-wet weight relationship yielded the equation W:= 9xl0⁻⁶ L³.¹⁶⁴. Spawning season was from mid-May through July with only one spawning period. Sexual maturity was attained for both males and females at a standard length of ≥ 32mm and age I⁺. Males displaying true breeding colors and females containing mature ova were found from mid-May to the end of July. Fecundity increased with age and size with the number of mature ova (≥0. 70mm) ranging from 142 to 301 for dace 32 to 50mm (age I⁺ - III⁺) in length. There was a good correlation between length and the number of mature Ova, length and ovary weight and between ovary weight and body weight. Percent occurrence of age I⁺ - III⁺ fish declined during the spawning season, a result attributed primarily to the introduction of age o* fish. Stomach analyses indicated dace were detritus feeders. Other aspects relating to the behavior of the dace preceding, during and following the spawning season are discussed,