Predation by introduced fish can magnify the terrestrial arthropod subsidies in mountain lakes

A portion of the terrestrial subsidies to lentic habitats consists of arthropods. In high mountain, originally fishless lakes, terrestrial arthropods are an important seasonal food resource for introduced fish. Here we investigate how brook trout Salvelinus fontinalis can alter the input of terrestrial arthropods in ten high mountain lakes contrasting for their stocking history (with and without fish, or manipulated for fish eradication). We used a food consumption model to calculate the minimum and maximum number/biomass of arthropods consumed by fish and we found that they can exceed several folds the number/biomass of arthropods sinking into the lakes, at least under the metabolic rates expected for fish for most of the summer. We interpret this result as an indirect indication that arthropods usually cannot overcome the surface tension at the lake surface and that fish can work as a vector across the water-air interface. We infer that pathways for dead and alive arthropods to leave the lakes do exist and fish can transfer into the water column many arthropods whose fate was leaving the lakes, which may have overlooked ecological and conservation implications.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author