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April 2017 Newsletter

A Closer Look #170

Egg Incubators

Return of the Arctic Grayling to the State of Michigan?

The Arctic grayling is a coldwater fish that occurs in northern regions of the world. Two populations historically existed in the contiguous USA: Montana and Michigan. The Arctic grayling was extirpated from Michigan in the early 1900s due to degradation of streams (primarily from logging), overharvest, and introduction of non-native trout. In Montana, Arctic grayling currently inhabit only a small portion of the historic area where it once occurred. Recent conservation efforts in Montana have focused on reestablishing Arctic grayling populations using incubators to hatch fertilized eggs in the streams targeted for reintroduction. The in-stream egg incubators are small, flow-through units that allow rearing and hatching of eggs directly at the site of reintroduction. This technique provides an opportunity for newly hatched fry to acclimate to local environmental conditions through imprinting on water chemistry at the “spawning” location and has proved more effective for reestablishing populations than traditional stocking practices (where juvenile fish are raised in hatcheries for stocking).

Carl Ruetz’s lab is working in collaboration with the Little River Band of Ottawa Indians (LRBOI) to test egg-incubator designs in three tributaries of the Manistee River. In this “pilot” study, researchers are using rainbow trout eggs as surrogates for Arctic grayling eggs, which are not yet available in Michigan. This research will support a larger effort by the Michigan Department of Natural Resources in partnership with the LRBOI to reintroduce Arctic grayling to Michigan. A first step in the Michigan effort is to determine whether the egg incubator designs that have been used effectively in Montana are appropriate for Michigan streams.