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Report, 2005

The Behavior and Ecology of Downstream Migrating Atlantic Salmon (Salmo salar L.) and Brown Trout (Salmo trutta L.) in Regulated Rivers In Northern Sweden

Ferguson, John W


This paper describes the life history diversity of the family Salmonidae with an emphasis on Atlantic salmon and anadromous (sea run) brown trout in northern Sweden. Baltic Atlantic salmon are a genetically unique stock with a distribution almost totally restricted to the Baltic Sea. Stock abundance has been negatively affected by many anthropogenic factors including the development of hydropower facilities and conversion of natural rivers into regulated systems, and today approximately 85% of the Atlantic salmon populations in Sweden have been extirpated from their historic range. Remaining wild salmon are found primarily in rivers in northern Sweden and Finland that flow into the Gulf of Bothnia. Rivers in northern Sweden offer some of the best available habitat for wild salmon and trout, and keystone populations remain in the river Piteälven, and the river Vindelälven which is the major tributary to the river Umeälven. This paper also reviews the downstream migration behavior and survival of smolts and post-spawn adults (kelts) through turbines and spillways in regulated rivers. Improving survival during this phase of the salmonid life cycle will increase adult escapements and help recover depressed populations. For example, eliminating the mortality associated with salmon smolts passing the Stornorrfors Power Station on the river Umeälven is estimated to improve the escapement of adult female salmon in the river Vindelälven by 110% within 10 years. This review highlights that little is known about the downstream migrations of juvenile and adult Atlantic salmon and sea run brown trout in northern Sweden. Additional information is needed on how smolts and adults approach, pass, and survive through spillways and power stations, and two approaches for gathering information on behavior and survival are discussed: model and empirical studies. Existing techniques for both approaches are available and can easily be modified to provide timely and costeffective methods to evaluate the behavior and survival of salmon and trout passing dams in northern Sweden. Based on this review the following activities are recommended: 1) model the downstream migration of smolts and kelts to estimate dates of dam passage and obtain a basic understanding of passage timing; 2) model the probability of fish injury through Francis and Kaplan turbines to ascertain whether changes in turbine operations during the downstream migration would improve the survival of juvenile salmon and trout and increase adult escapements; and 3) obtain empirical estimates of downstream migrant survival through turbines, spillways, and dams under existing operations and evaluate the effectiveness of new operations or guidance structures installed to improve passage survival. Data from these studies will provide salmon and power station managers with information needed to develop improved passage conditions, help achieve salmon and trout conservation and rebuilding goals in the rivers of northern Sweden, and conserve the unique genetic diversity of Baltic Atlantic salmon and anadromous brown trout in the region

Published in

Rapport / Sveriges lantbruksuniversitet, Vattenbruksinstitutionen
2005, number: 44
Publisher: Vattenbruksinstitutionen, SLU

Authors' information

Ferguson, John W.

UKÄ Subject classification

Fish and Aquacultural Science

URI (permanent link to this page)