Genetic enhancement of landlocked salmon and adfluvial brown trout by crossbreeding

The primary objective of conserving and restoring endangered migratory fish stocks is to safeguard their genetic diversity and thereby their capacity to adapt through natural selection. The genetic variation of the landlocked salmon and brown trout populations managed within the Vuoksi watershed is very low, which may complicate the re-establishment of their natural life cycles in their original or new habitats. The genetic narrowness of these populations can only be broadened by introducing new genetic variants through stock crossbreeding. In this project, the inclusion of the Hiitolanjoki (Ladoga) landlocked salmon population is promoted as part of the genetic restoration of the Saimaa landlocked salmon. In addition, experimental studies seek answers to how crossing landlocked salmon with geographically close anadromous salmon stocks affects the viability and performance of the resulting offspring across different hybrid generations. Regarding brown trout, the project supports, through stock crossbreeding and supportive stockings, the potential of small streams flowing into Lake Pielinen to restore wild migratory populations. Hybrids of migratory and resident trout are produced and stocked into a few selected rivers from which the resident trout have previously been captured for hatchery broodstock. The aim is to increase genetic diversity and the occurrence of the migratory form in small and locally adapted (isolated) brown trout populations. The outcomes of the stockings will be monitored through electrofishing surveys and genetic analyses.

The experimental work is carried out in cooperation with the Universities of Eastern Finland and Jyväskylä, and lake-monitoring data on hybrid salmon are collected from PIT-tagged stocked fish through the data collection coordinated by Elinvoimainen järvilohi ry (Lake Puulavesi). Part of the experimental material used in the study has already been collected during a previous project.

Hatchery broodstock reserves will be established from the crosses of both salmonid species to create preparedness for advancing the hybridization programme and for the subsequent use of fish material in stockings conducted for stock management. The work is carried out at Luke’s Enonkoski, Keminmaa and Taivalkoski aquaculture units.

Because hybrid material originating from different brown trout stocks is used in the stockings, the measure has undergone Luke’s internal ethical assessment for experimental research. The success of the stockings will be monitored through electrofishing surveys conducted in the rivers and through genetic analyses of collected samples. In addition, the project will produce a second genetically diverse year class of brown trout hybrids (F1) and the first backcross generation, from which hatchery broodstocks will be established at the Taivalkoski aquaculture station for further rearing. Regional activities will be carried out in cooperation with local fisheries managers.