Ecology of the quillback (Carpiodes cyprinus) of Dauphin Lake, Manitoba
The ecology of the quillback (Carpiodes cyprinus) of the Dauphin Lake, Manitoba, was studied during the open water periods of 1984 and 1985. Spring spawning runs were monitored with a fish fence on the Ochre River while quillback were collected from Dauphin Lake in beach seining surveys carried out each summer. Quillback spawning migrations commenced when water temperatures reached 5 C but were confined to pulses of runoff following snowmelt and precipitation events. Movements were concentrated in the mid-afternoon and early night hours. Some migrants moved upstream as far as 32 km but others only 1.6 km. Spawning was observed, usually over riffles, at water temperatures of 7 to 18 C in late April to mid June. The mean fork length (FL) of spawning adults was 420 mm and mean weight 1770 g. Fecundity ranged from 51,600 to 360,000 in fish of 970 to 3150 g (358 to 507 mm FL) and was linear with wet weight where ln(fec) = 2.35 + 1.27 ln(wet weight). Large (>1200 g) females had significantly heavier ova and greater % wet gonad weight than small individuals. The maximum recorded % gonad weight was 22.5%. Hatching of larvae occurred 229.8 degree days after spawning. Mean total length of newly hatched larvae was 7.95 mm. Larvae drifted overnight while still in the prolarval stage. Overnight predation on larvae by shiners (Notropis cornutus and N. hudsonius) and darters (Etheostoma nigrum and Percina shumardii) was recorded. Adults marked with Floy FD anchor tags had an 8.6% annual tag loss rate. The mean growth rate of tagged adults was less than 7.5 mm/year. Commercial exploitation of the marked population was <1% per year and recreational exploitation negligible. Fin ray ageing was validated, but only to age 8, and otoliths, opercles, vertebrae and scales were validated to the same age by comparison. Otoliths gave the oldest ages thereafter. Male quillback mature at 4, 5 or 6 years of age and females at 6, 7 or 8 years at minimum fork lengths of 280 and 345 mm respectively. The largest individual captured was a pre-spawn female of 560 mm FL (626 mm TL) and about 4 kg wet weight. Length-weight relationships were ln(wet weight) = -9.839 + 2.834 ln(FL) for spent adults and ln(wet weight) = -12.136 + 3.243 ln(FL) for juveniles. Quillback ate small (<.6 mm diam.) benthic items including chironomids, entomostracans and Difflugia. Large quantities of sand and organic detritus usually were present in stomachs. The diet of large (>200 mm FL) and small quillback from inshore samples was very similar. Several quillback taken offshore consumed nearly 100% entomostracans but very little sand suggesting that facultative midwater feeding may occur. Post-spawning migrants consumed small quantities of fish eggs. Preferred substrates were loose sandy to sandy-silty combinations in areas sheltered from wave action. Young-of-year (YOY) were taken only in shallow inshore waters, while adults preferred deeper water except on hot, calm days when they could also be taken inshore.