New Chiller Unit at Iron River NFH Produces “Cool” Results
BY CAREY EDWARDS, IRON RIVER NFH
Fahrenheit, the hatch date was delayed by one month for these fry. Credit: USFWS
The Iron River National Fish Hatchery (NFH) produces 1.6 million lake trout and coaster brook trout annually for restoration purposes in the upper Great Lakes. The Klondike Reef strain of lake trout makes up 200,000 of our total number. These fish spawn in early September which is a month and a half earlier than most other strains of lake trout. The early spawn time has our eggs incubating in some of the warmest water temperatures the hatchery experiences, which leads to faster development of eggs and fry. This has a trickle-down effect that equates to larger fish in the spring when space is limited in both raceways and fish trucks.
This past fall, an egg incubation chiller room was constructed to combat this issue. The chiller room contains a small health incubator and two troughs capable of holding five egg jars each. A pump recirculates water through a chiller and UV unit before entering the system. Shortly after eye-up, the Klondike eggs were placed into jars and water chilled to 35 degrees Fahrenheit was used to incubate them (regular spring water is twelve degrees warmer). The chilled water had the desired effect we were looking for…delayed hatch by one month. The fry have just started to eat (also delayed by a month!) and will be monitored for any adverse effects that could be seen from the chilling process. The outcome has proven successful so far and the chiller is currently being used on another group of lake trout eggs to slow down development.