Hatchery system helps determine fish stocking
Written by Gaylord Herald Times   
Wednesday, 29 March 2006 15:45

This past fall, significant reductions were agreed upon by the fishery management agencies for both Lakes Huron and Michigan in terms of the number of Chinook salmon that will be stocked in the future.

Anglers often question the Dept. of Natural Resources (DNR) why more steelhead or coho salmon yearlings - or for that matter brown and rainbow trout - cannot be produced if less Chinook salmon are being produced.

According to the DNR, the main reasons why more yearlings are not produced are the hatchery life cycle of these species and the rearing abilities of DNR hatcheries. Chinook salmon are reared indoors for six months and they don't typically use outside raceway space that could be used by coho salmon and steelhead. Producing fewer spring fingerling Chinook salmon does not, contrary to belief, open up more rearing space for the other yearling species because they don't occupy the same space at the same time.

Hatchery fish are a lot like people in that they have preferences for their surroundings. Some hatchery fish prefer cool water, and some prefer warm water. Some like crowded runs, while others like more space. Fish are also similar to people in that they have a wide range of tolerance for disease. The environmental preferences that fish have, as determined by their life history, determine the best hatchery for them to be reared in. The goal of any good hatchery management program is to match the species to be reared with the optimal environment. If the right environment is provided for in terms of temperature and space, the species will generally do well and the fish produced will be healthy.

Water temperature plays a key role in determining which fish can be reared at which DNR hatchery. Species such as rainbow and brown trout rear best in cold water in the range of 45 to 48 degrees. Salmon and steelhead, on the other hand, perform better in warmer hatchery water in the range of 50 to 55 degrees.

Wolf Lake State Fish Hatchery near Kalamazoo, Platte River State Hatchery near Honor and the Thompson State Fish Hatchery near Manistique in the central Upper Peninsula all have warmer waters, thus are good for rearing salmon species.

The DNR's other three hatcheries are trout-oriented and include Harrietta State Fish Hatchery near Cadillac, Oden State Fish Hatchery near Petoskey and Marquette State Fish Hatchery at Marquette. These three hatcheries have colder water than the salmon hatcheries and are better suited for rearing trout, including browns, rainbows, brook and lake trout. Marquette and Oden State Fish Hatcheries are broodstock facilities that have captive (adult) fish that provide eggs for the rearing program. Because the adult broodstock are very valuable and could not be replaced if lost to disease, hatchery staffs are very careful in protecting these fish from diseases from outside the hatchery. Typically, the DNR does not bring in Great Lakes fish or eggs directly into these broodstock facilities.

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