Otolith microchemistry and acoustic telemetry reveal anadromy in non-native rainbow trout (Oncorhynchus mykiss) in Prince Edward Island, Canada

This study examined the migratory patterns of introduced rainbow trout (Oncorhynchus mykiss) in three rivers in Prince Edward Island, Canada, using acoustic telemetry and otolith microchemistry. Only 6% of acoustically tagged fish in three river systems left coastal embayments. A cohort of rainbow trout in all three rivers entered saline waters. Habitat use differed among migrants in the three rivers, as Montague River fish occupied estuary habitat (mean 20.79 PSU) more often than West River and Dunk River fish that tended to occupy both riverine tidal (mean 1.27 and 4.29 PSU, respectively) and freshwater habitats (<0.5 PSU), particularly during summer months (July and August). A second cohort of rainbow trout remained exclusively in fresh water. Migratory individuals were more likely to arise from anadromous mothers, but freshwater mothers produced migratory offspring in all sites. Migratory individuals were significantly larger than nonmigratory freshwater residents. This study suggests that partial residency was the primary strategy, with prominent tidal occupation, while secondary marine and freshwater contingents were included in the full range of successful migratory strategies.

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Population structure of sympatric anadromous and nonanadromous Oncorhynchus mykiss: evidence from spawning surveys and otolith microchemistry

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f00-192 ◽

2000 ◽

Vol 57 (10) ◽

pp. 2152-2162 ◽

Cited By ~ 68

Author(s):

Christian E Zimmerman ◽

Gordon H Reeves

Keyword(s):

Population Structure ◽

Rainbow Trout ◽

Oncorhynchus Mykiss ◽

Electron Microprobe ◽

Otolith Microchemistry ◽

Maternal Origin ◽

Isolated Populations ◽

Rainbow Trout Oncorhynchus Mykiss ◽

Deschutes River ◽

Spawning Sites

Reproductive isolation between steelhead and resident rainbow trout (Oncorhynchus mykiss) was examined in the Deschutes River, Oregon, through surveys of spawning timing and location. Otolith microchemistry was used to determine the occurrence of steelhead and resident rainbow trout progeny in the adult populations of steelhead and resident rainbow trout in the Deschutes River and in the Babine River, British Columbia. In the 3 years studied, steelhead spawning occurred from mid March through May and resident rainbow trout spawning occurred from mid March through August. The timing of 50% spawning was 9-10 weeks earlier for steelhead than for resident rainbow trout. Spawning sites selected by steelhead were in deeper water and had larger substrate than those selected by resident rainbow trout. Maternal origin was identified by comparing Sr/Ca ratios in the primordia and freshwater growth regions of the otolith with a wavelength-dispersive electron microprobe. In the Deschutes River, only steelhead of steelhead maternal origin and resident rainbow trout of resident rainbow trout origin were observed. In the Babine River, steelhead of resident rainbow trout origin and resident rainbow trout of steelhead maternal origin were also observed. Based on these findings, we suggest that steelhead and resident rainbow trout in the Deschutes River may constitute reproductively isolated populations.

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