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Chelatna pike suppression in 2018 and 2019

Citation

DeCino, Robert et al. (2020), Chelatna pike suppression in 2018 and 2019, Dryad, Dataset, https://doi.org/10.5061/dryad.fttdz08q3

Abstract

Northern pike are an invasive species in southcentral Alaska and have caused the decline and extirpation of salmonids and other native fish populations across the region. Over the last decade, adaptive management of invasive pike populations has included population suppression, eradication, outreach, angler engagement, and research to mitigate damages from pike where feasible. Pike suppression efforts have been focused in open drainages of the northern and western Cook Inlet areas, and eradication efforts have been primarily focused on the Kenai Peninsula and the municipality of Anchorage. Between 2010 and 2020, almost 40,000 pike were removed from southcentral Alaska waters as a result of suppression programs, and pike have been successfully eradicated from over 20 lakes and creeks from the Kenai Peninsula and Anchorage, nearly completing total eradication of pike from known distributions in those areas. Northern pike control actions are tailored to the unique conditions of waters prioritized for their management, and all efforts support the goal of preventing further spread of this invasive aquatic apex predator to vulnerable waters.

Methods

Variable-mesh gillnets and hoop traps were used to capture and remove northern pike in Chelatna Lake from late May through June 30..  Gillnets typically capture larger pike (>250 mm) and hoop traps capture smaller pik. Pike removal efforts began immediately after ice melt in the lake, because northern pike are more active and vulnerable to capture during their spring spawning season.

Each day, ten variable-mesh gillnets were deployed at 10 shallow and vegetated sites that typically provide optimal northern pike habitat.  Nets will be deployed in the afternoon or evening and retrieved the next morning.  Time of each net set and retrieval will be recorded to the nearest minute.  Gillnets used were 22.9 m long x 1.8 m deep and constructed of 5 panels with 2.5 cm, 3.8 cm, 5.1 cm, 6.4 cm and 7.6 cm mesh sizes.  The top line, a floating core line and the bottom line lead weighted to sink.  Gillnet mesh sizes were chosen to increase the size range and catchability of northern pike.

Each day, up to ten hoop nets were deployed near the 10 sites in close proximity to variable-mesh gillnets. Hoop nets have 0.8 m diameter opening with 4.6 m wing leads.  Nets were set near shore in water depths ranging from 1-3 m, and in general nets wereset perpendicular to the shoreline.  Nets were retrieved one at a time and samples processed before retrieving other nets to prevent mixing fish from different net sets.

Captured pike were removed from the nets and quickly dispatched using a small bat. Species other than northern pike were removed and released immediately.  Northern pike fork length (length from tip of nose to fork of tail) were be measured to the nearest mm, weight to the nearest gram, and sex will be determined.  Scales and cleithra were taken from each fish for age determination in the laboratory. 

Stomach contents were recorded based on a visual evaluation of percent of total volume for each prey type. Prey categories included sockeye smolt, sockeye fry, coho smolt, coho fry, other salmonid, trout, stickleback, partial unidentified fish, insects, leeches, snails, unidentified prey.  If juvenile salmon are found in the stomach, they will be counted by species and their lengths measured to the nearest mm. Harvested pike were donated to local residents or cut in half and disposed of in the middle of the lake in accordance with permits.

Usage Notes

see readme chelatna_pike_suppression for file description and definitions

Funding

Alaska Sustainable Salmon Fund, Award: NA16NMF4380336

Alaska Sustainable Salmon Fund, Award: 44609

Alaska Sustainable Salmon Fund, Award: 44613

Alaska Sustainable Salmon Fund, Award: 44617

Alaska Sustainable Salmon Fund, Award: 44626

Alaska Sustainable Salmon Fund, Award: 44807

Alaska Sustainable Salmon Fund, Award: 44910

Alaska Sustainable Salmon Fund, Award: 44168

Alaska Sustainable Salmon Fund, Award: 44353

Alaska Sustainable Salmon Fund, Award: 44365

Alaska Sustainable Salmon Fund, Award: 51003

Alaska Sustainable Salmon Fund, Award: 52013