DOI: 10.5061/dryad.fttdz08q3
title: Chelatna pike suppression in 2018 and 2019

description: 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.
description: 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 (&gt;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<i> </i>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.
description: see readme chelatna_pike_suppression for file description and
 definitions