Studies on the Minnow Phoxinus Phoxinus (L.) from an Upland Irish Reservoir System

The paper deals with the population structure and biology of the minnow, Phoxinus phoxinus (L.), in the Roundwood Reservoir system. A total of 4,342 minnow were taken during the study period from three locations, 2,796 fish were used to calculate the age distributions and 3,013 were examined for gut contents. The age data, determined from the otoliths, showed that there are five age classes present. The mean length at the end of the first year (O-Group fish), was 3.41 cm, at the end of the second year (I-Group fish) it was 5.32 cm and 6.68 cm at the end of the third year (II-Group). Only thirteen minnow were found to be older than three years. The breeding season is later than normal and peaks in August and September. Sexual maturity is reached by the majority in their second year and all older fish are mature. Egg diameters were shown to be smaller than for fish from midland Irish waters. In the North and South Lakes the dominant food organisms were found to be chironomid and trichopteran larvae, molluscs and Cladocera. The diet of the fish from the Vartry River contained more ephemeropteran nymphs. Seasonal differences in the diet are noted. The influence of the minnow on the associated fish species is discussed. An account of the distribution of the minnow in Ireland is included as an Appendix.

URI

http://hdl.handle.net/10793/265

Citation

Dauod, H.A. & Bolger, T. & Bracken, J.J., "Studies on the Minnow Phoxinus Phoxinus (L.) from an Upland Irish Reservoir System", Department of Agriculture and Fisheries [Fisheries Division]