Title
Under-ice population density estimation of Alaska blackfish
Author(s)
Fraley, Kevin M.;Haynes, Trevor B.;López, J. Andrés
Published
2018
Publisher
North American Journal of Fisheries Management
Published Version DOI
https://doi.org/10.1002/nafm.10050
Abstract
Alaska Blackfish Dallia pectoralis are an understudied but ecologically important mudminnow occurring in lentic ecosystems of subarctic and Arctic Alaska. We sampled a population of Alaska Blackfish during the winter months in an upland pond near Fairbanks, Alaska, and used a simple mark-recapture estimator to provide the first population estimate for this species. We found that blackfish density in the pond was approximately 0.27 individuals per m2, equating to an estimated biomass of 15 g per m2 of pond surface area, which is similar to density estimates reported for other species of mudminnow. We tested capture methods, and found that under-ice minnow trapping was a poor method during early winter (September-December), but was highly effective near methane sumps and areas of high muskrat activity in late winter (March-April). Qualitatively, near-shore minnow trapping, seining, and kick-netting during the ice-free season were less effective than under-ice trapping. Cursorily, pelvic fin clips were more effective for batch marking blackfish than two types of subcutaneous tags, given the high numbers of individuals we captured and the relatively small body size and dark skin of the species making visualizing tags difficult. This study demonstrated that Alaska Blackfish can occur at high densities in their typical habitat, underscoring their importance as a forage fish in freshwater ecosystems of Alaska that support sport and subsistence fisheries for piscivorous fishes. Extending this approach across the geographic range of Alaska Blackfish will improve understanding of the ecological role of this species in the varying aquatic ecosystems where it occurs.

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