Epsilon Archive for Student Projects

Abstract

The purpose of this study was to investigate migration patterns and spawning habitat of ide (Leuciscus idus) in three streams on Gotland (Idån, Närkån & Snoderån). Visual surveys were conducted from land along fixed routes every 2–7 days from March 11 (Idån and Snoderån) and March 24 (Närkån) to April 27. Spawning was first observed April 1 and that the number of observed fish correlated with spawning. The temperature varied between 6.6 – 9.1 ˚C in the different streams when spawning occurred, and the spawning grounds with highest egg density were at shallower depths (0,5 m/s), at higher water velocity (>0,5 m/s) and with stone, gravel and blocks as the dominated substrate. One week after spawning was first observed, potential spawning sites were surveyed for eggs, with egg density (categories 1–7), water depth, water velocity and substrate type recorded. A fry trap in Idån was deployed two weeks after spawning was first observed. Downstream-drifting fry were caught 5 weeks after spawning, with 260 individuals caught over a three-week period. Fry ranged in body length from 5 to 16 mm, suggesting variation in hatching time and growth rate among individuals. Results also indicated that ide showed a preference for areas with overhead cover such as bridges and trees, and that fish numbers increased further upstream during peak spawning. Future research using telemetry could provide insights into individual migration routes before and after spawning and whether ide exhibit homing behaviour.