Nutrient Restoration Using Atlantic Salmon Carcasses as a Component of Habitat Management in Scottish Highland Streams

Abstract

It has long been known that an excess of nutrients can degrade freshwater ecosystems and fish habitat. However, in some situations human activities can reduce nutrients below natural levels and negatively affect fish production. Nutrient restoration or augmentation may therefore be required for effective habitat management. In this study, we restored nutrients in the form of adult Atlantic salmon carcasses to streams in the Conon river system in northeastern Scotland. We monitored colonisation of the carcasses by aquatic macroinvertebrates, assessed incorporation of carcass-derived nutrients into aquatic food webs and compared invertebrate abundance (IA) in carcass-addition and reference sites. The isotopic signatures of periphyton, macroinvertebrates and juvenile salmon were all enriched after carcass addition, indicating incorporation of marine-derived nutrients. Atlantic salmon carcasses were rapidly and intensively colonised by a wide range of macroinvertebrates, some of which were found on carcasses nearly exclusively. Larval blackflies (Simuliidae) were the most abundant colonists in early samples. By late May and June, when carcasses were in an advanced state of decomposition (<20% of initial mass), larval chironomid (non-biting) midges, which appeared to use carcasses largely as a food source, were the dominant invertebrates. In the multiple-stream study, carcass-addition sections had significantly higher total invertebrate biomass than reference sections. Incorporation of marine-derived nutrients by all major food web components, extensive invertebrate colonisation of Atlantic salmon carcasses and increased IA suggest that nutrient restoration may be an important part of habitat management, and may partly be accomplished by ensuring the availability of marine-derived nutrients from migratory Atlantic salmon. Salmonid Fisheries: Freshwater Habitat Management Paul Kemp

More than just fish food: ecosystem services provided by freshwater insects

“…It is difficult to disentangle the relative contribution of aquatic insects over other macroinvertebrates to the processing of organic matter as studies tend to take a community approach. However, we can at least identify the groups and species which may be most important such as the facultative shredders Leuctridae and Nemouridae (Plecoptera), specialist shredders Potamophylax and Sericostoma (Trichoptera, Limnephilidae and Sericostomatidae) (De Nadaï-Monoury et al, 2014), and blackflies (Diptera, Simulidae) (Nislow et al, 2010).…”

“…However, we can at least identify the groups and species which may be most important such as the facultative shredders Leuctridae and Nemouridae (Plecoptera), specialist shredders Potamophylax and Sericostoma (Trichoptera, Limnephilidae and Sericostomatidae) (De Nadaï-Monoury et al, 2014), and blackflies (Diptera, Simulidae) (Nislow et al, 2010).…”

Simulating nutrient release from parental carcasses increases the growth, biomass and genetic diversity of juvenile Atlantic salmon

“…While emigrating juveniles also transport nutrients in the opposite direction, the relative scale of the nutrient flows is such that the majority of anadromous populations generate a net import of marine‐derived nutrients to freshwater communities (Childress, Allan, & McIntyre, ; Flecker, Mcintyre, Moore, Taylor, & Hall, ; Naiman et al, ; Walters, Barnes, & Post, ). The effect—generally in the form of increased productivity and/or biomass—is detectable in freshwater food webs, especially when ecosystems are otherwise oligotrophic (Claeson, Li, Compton, & Bisson, ; Guyette, Loftin, Zydlewski, & Cunjak, ; Nislow et al, ).…”

“…To date, most studies on the impact of nutrient restoration in freshwater streams find that the addition of carcasses or carcass analogues increases invertebrate abundance and biomass (Claeson et al, ; Nislow et al, ; Wipfli et al, ) and generally benefits fish growth and body condition (Guyette et al, ; Williams et al, ; Wipfli, Hudson, Caouette, & Chaloner, ). However, effects on fish density and biomass are unclear, in part due to the limitations of field studies in controlling for the immigration of non‐experimental fish into restored areas, as shown by Bilby et al ().…”

Factors driving spatial and temporal variation in production and production / biomass ratio of stream-resident brown trout (Salmo trutta) in Cantabrian streams

“…The assessment of production dynamics of freshwater organisms has a long history (Waters, 1969), and relationships among production, life history traits and environmental factors have been reported for a broad array of aquatic taxa across different systems (Waters, 1977;Banse & Mosher, 1980;Plante & Downing, 1989;Benke, 1993;Randall & Mills, 2000). In particular, investigations on stream-living fish include a variety of studies relating production dynamics to the productive capacity of the stream (Kwak & Waters, 1997;Randall & Mills, 2000), geographical regions (Crisp, Mann & McCormack, 1974, 1975Mann, Blackburn & Beaumont, 1989;Mazzoni & Lobó n-Cerviá, 2000) and environmental variability (Lobó n-Cerviá, 2003) and include experimental research (Warren et al, 1964;Bergheim & Hesthagen, 1990;Nislow et al, 2010).…”