Conservation of endemic landlocked salmonids in regulated rivers: a case‐study from Lake Vänern, Sweden

Abstract

Conservation of migratory salmonids requires understanding their ecology at multiple scales, combined with assessing anthropogenic impacts. We present a case‐study from over 100 years of data for the endemic landlocked Atlantic salmon (Salmo salar, Salmonidae) and brown trout (Salmo trutta, Salmonidae) in Lake Vänern, Sweden. We use this case‐study to develop life history‐based research and monitoring priorities for migratory salmonids. In Vänern, small wild populations of salmon and trout remain only in the heavily regulated Rivers Klar (Klarälven) and Gullspång (Gullspångsälven), and commercial and sport fisheries are maintained by hatchery stocking. These populations represent some of the last remaining large‐bodied (up to 20 kg) landlocked salmon stocks worldwide. We found that one of four stocks of wild fish has increased since 1996; the other three remain critically low. Hatchery return rates for three of four stocks appear stable at roughly 1% and annual fisheries catch is roughly 75 metric tons, with an estimated 7.5% of hatchery smolts being recruited to the fishery; this also appears relatively stable since 1990. Our analysis reveals much uncertainty in key data requirements, including both river return and fisheries catch rates, estimates of wild smolt production and survival, and hatchery breeding and genetics protocols. These uncertainties, coupled with a lack of information on their riverine and lacustrine ecology, preclude effective management of these unique populations. We conclude with a framework for a life history‐based approach to research and monitoring for Vänern salmon and trout, which should be applicable for all endemic, migratory salmonid populations.

MULTIPLICATIVE LOSS OF LANDLOCKED ATLANTIC SALMON Salmo salar L. SMOLTS DURING DOWNSTREAM MIGRATION TROUGH MULTIPLE DAMS

“…There is little information on the timing of the smolt migration period in Klarälven, but our results and other studies (Nordberg, ; Piccolo et al ., ; Lans et al ., ) suggest that migration occurs from late May through early July, with a peak in late June, which is considerably later compared with most anadromous populations. Because of water regulation, discharge downstream HEP‐9 Höljes typically gradually declines during the smolt migration period.…”

The Migratory Behaviour and Fallback Rate of Landlocked Atlantic Salmon (Salmo salar)in a Regulated River: does Timing Matter?

“…The late (August-September) mean discharge was 285 m 3 /s in 2012 and 121 m 3 /s in 2013. The River Klarälven has been dammed for hydropower purposes since the beginning of 1900s but has also been affected by other anthropogenic activities even earlier (Piccolo et al, 2012). Today there are 11 hydropower plants in the river, nine of which are situated in Sweden.…”

“…The River Klarälven in Sweden hosts one of three remaining large-bodied, landlocked, populations of salmon in Europe (Piccolo et al, 2012). Populations of both Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) in the River Klarälven have experienced dramatic declines due to anthropogenic activities such as timber logging and hydropower development.…”

“…Populations of both Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) in the River Klarälven have experienced dramatic declines due to anthropogenic activities such as timber logging and hydropower development. Despite supplementary stocking and trap and truck activities dating back to the 1930s, the populations are still considered to be low (Piccolo et al, 2012). Today, all remaining spawning habitats are located upstream of eight hydropower plants, and consequently fish caught at the lowermost power plant are transported and released for spawning upstream of those plants.…”

The Land Ethic and conservation of native salmonids

“…Much discussion about the core values of 'New' and 'Old' conservation biology followed, in part centred upon why we conserve naturewhether nature should be conserved for its instrumental value or for its intrinsic value (see Tallis et al 2014 for a summary). Overfishing, habitat loss and hydropower development caused populations to decline as low as 100 wild spawners by the 1970s, but restoration efforts have results in population recovery (Piccolo et al 2012). Intrinsic values are those found in nature itselfvalues that exist Fig.…”