Supporting evaluation components of the Lake Huron Technical Committee’s cisco reintroduction study: a multi-agency effort to promote cisco recovery in the western basin of Lake Huron (FY19)

Contributing Authors

Kevin McDonnell (USFWS,

Executive Summary

The U.S. Fish and Wildlife service conducted two surveys in 2019 aimed at documenting the current distribution, composition, and density of the larval coregonid community in Saginaw Bay. Sampling was limited to pelagic ichthyoplankton and beach seining due to the funding and logistic limitations. No sampling was possible in 2020 due to the impact of the covid-19 pandemic on field operations. Pelagic ichthyoplankton surveys were conducted weekly at 40, randomly selected, spatially balanced, depth stratified (0-3,3-6,….,15m+) sites throughout Saginaw Bay from April 8 – April 23 2019. During each ichthyoplankton sample larvae were sampled within 1m of the surface using a 500-µm, 2 x 1m neuston net. Larval coregonids were present in each depth bin >3m throughout the entire Bay in all three weeks of sampling. Observed larval coregonid densities of individual neuston tows ranged between 0 and 0.478 individuals/m3 with sampled coregonid larvae ranging between 8.79 and 17.21mm in total length. Observed larval coregonid densities pooled across sampling weeks and depth bins indicated that densities increased during the sampling period and were highest in the 3-6m range across the sampling period. We relied on meristics and morphology to differentiate larval lake whitefish and cisco, which unfortunately proved to be difficult. The vast majority (>96%) of the total ichthyoplankton catch could not be reliably identified past the Coregonus genus. Confirmed lake whitefish and cisco only made up 3.3% and 0.04% of the total catch respectively. Approximately 1500 larval coregonids were made available for genetic sequencing to aid in the development of future genetic-based assignment techniques (Building Molecular Tools for Coregonine Species Identification, Stott et al.). More than 1800 larvae had additional key morphometrics (myomere counts, head length, body depth, etc…) counted and measured to provide further information for future identification efforts. Beach seining was done at two sites on the eastern shore of Saginaw Bay near Tawas and north of AuGres. Access to sites suitable for beach seining was made difficult due to the relatively high water levels being experienced by the upper Great Lakes. Beach seines (50m in length, 3.175mm mesh) were conducted on May 30th and July 2nd 2019 at each site. 185 young of year lake whitefish (mean total length 28mm) were sampled during the sampling at Tawas Beach on May 30. Unfortunately, no other coregonids were observed during any of the other beach seines.

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Restoration Framework Phase

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