Riparian insect response to experimental salmon carcass additions to Idaho streams.
Terrestrial and emerging aquatic insects incorporate marine-derived nutrients from salmon carcasses either directly by consuming carcass material, or indirectly when salmon nutrients stimulate primary and secondary producers. We hypothesized that addition of salmon carcasses would increase abundance, alter species composition, and affect distribution of insects in riparian areas. In summer 2008 we initiated a large-scale field experiment across 9 streams, consisting of 500-m reaches treated with salmon carcasses (n=3), pelletized salmon (n=3), and un-treated reference reaches (n=3). Sticky traps were deployed laterally at 0, 5, and 25 m intervals at each stream to track patterns. From direct counts, roughly eighty percent of aquatic insects captured were within 5 m of the stream. Treatments caused significant increases in abundance of adult aquatic insects. In addition, terrestrial insects, particularly adult dipterans were attracted to reaches receiving carcass and analog treatments, resulting in altered insect assemblage composition in the stream riparian zone. Increases in both terrestrial dipterans and adult aquatics occurred two to four weeks post-treatment, but effects on aquatic adults persisted longer. Higher aquatic and terrestrial insect abundance could affect predator-prey dynamics in linked streamriparian food webs, as these insects are prey for stream fishes and terrestrial insectivores.
Idaho Chapter of the American Fisheries Society Annual Meeting
Riparian insect response to experimental salmon carcass additions to Idaho streams..
Idaho Chapter of the American Fisheries Society Annual Meeting,
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