The Stocked Rainbow Trout in Minnesota Waters of Lake Superior

For those unfamiliar with the rainbow trout fishery along Minnesota’s North Shore of Lake superior, here is a little background:

There are currently 2 strains of anadromous rainbow trout being stocked into Minnesota waters of Lake Superior (although others have been stocked in past years, such as the Madison strain and the Donaldson Strain). The first is a steelhead strain introduced from the Pacific coast into Lake Superior over 100 years ago, and have since become naturalized with spawning populations using tributary streams along the north and south shores. These “wild” fish spawn in Minnesota tributaries, but barriers near the mouths of most streams limit access to  additional areas that are potentially suitable for spawning. Therefore, steelhead adults are captured annually in the French River to collect spawn, eggs are hatched, and the unfed swim-up fry are later stocked above tributary boundaries.

The second strain currently being stocked is the kamloops strain. The kamloops were introduced into Minnesota waters of Lake Superior in the late 1960s to augment naturalized stocks. Many people think that they came from Kamloops, British Columbia – but this is not true. In fact they are not even really Kamloops rainbow trout. Genetic analyses have shown that these fish do not represent the pure form of Kamloops trout originating in the Kamloops area of British Columbia, so the strain is shown in lowercase. They are merely some form of hybridized rainbow trout.

Due to the perceived threat of hybridization with steelhead, the stocking of kamloops has been limited to reduce the overlap in spawning runs. The kamloops strain is maintained entirely by stocking and is referred to as a hatchery strain. The kamloops strain in Lake Superior cannot successfully reproduce naturally, so by cross breeding with naturalized steelhead they will flaw their genetic integrity ultimately lowering sustaining populations of “wild” steelhead and keeping them from coming back to their once higher populations in Lake Superior.

So the next time you are fishing Minnesota’s North Shore, catch some “loopers” (a.k.a. bastard fish) and eat them up to help preserve the genetic integrity of the “wild” steelhead.

For more information please see the following PDF documents pulled directly from the Minnesota DNR.

Also a FAQ on the DNR’s rainbow trout management in Minnesota waters of Lake Superior:

1) What was the goal of the 1992 Steelhead Plan and was it achieved?

The goal was to “stop the decline of adult steelhead and gather the necessary information to rehabilitate wild steelhead stocks.” This goal has generally been accomplished. The decline in adult steelhead abundance has been largely reversed, and although there are still information needs regarding wild steelhead, the knowledge base on steelhead in Minnesota has grown significantly over the last ten years. Objectives and accomplishments from the 1992 steelhead plan are listed in Appendix 2 of the proposed plan.

2) What is the goal and purpose of the proposed Rainbow Trout Management Plan?

The long-term goal of the proposed plan is to “rehabilitate steelhead stocks using Minnesota strain fish to achieve a level that will allow limited angler harvest largely supported by naturally reproducing populations.” The purpose of this revised rainbow trout plan is to utilize the information gained from the previous plan and work with interested citizens to continue restoration of wild steelhead stocks.

3) Why have steelhead populations declined since the 1970’s?

The restoration of lake trout and the naturalization of coho and chinook salmon, along with a major decline in smelt abundance have increased competition and have made steelhead more vulnerable to predation. Angling pressure for steelhead increased approximately 10-fold from the 1960s to the late 1980s and increased harvest significantly reduced the number of spawners. Land use changes have negatively impacted temperature regimes and stream hydrology degrading spawning and nursery habitats that are necessary for successful reproduction and juvenile steelhead survival.

4) Why doesn’t Lake Superior produce more and larger rainbow trout like those caught in Lake Michigan?

The physical environment of Lake Michigan is better suited for rainbow trout production. Lake Michigan has more in-lake shallow water habitat. Average surface temperature can be 10-15 degree F warmer, and the optimal growing season can be 1-3 months longer, in Lake Michigan. The biological productivity of Lake Michigan is about 3 times that of Lake Superior, creating an environment better suited for rainbow trout growth and survival.

5) Why doesn’t the MNDNR expand the Kamloops stocking program beyond its present range?

Based on studies conducted by MNDNR research biologists and university scientists, hybridization between Kamloops and wild steelhead is a risk and would likely be detrimental to wild steelhead rehabilitation efforts through dilution of steelhead gametes. Specific studies have shown that:

  • When in close proximity, Kamloops and steelhead will interbreed and create hybrid juveniles in the wild.
  • Kamloops eggs have higher mortality than steelhead eggs under natural stream conditions.
  • Steelhead fry are much more wary than Kamloops when startled.
  • Relative survival of stocked steelhead fry to age one in North Shore streams was 5 times greater than survival of Kamloops fry to age one.

In all studies, hybrids between steelhead and Kamloops performed at an intermediate level, with the maternal steelhead cross having higher survival than the maternal Kamloops cross.

6) Given the potential negative genetic impacts of Kamloops on naturalized steelhead, why doesn’t the MNDNR discontinue the program?

Over half of the angling pressure in the spring fishery is directed at Kamloops and the catch rates of Kamloops are generally double those of steelhead. In addition, winter creel surveys show that fishing pressure for Kamloops surpasses spring fishing pressure for all rainbow trout strains. Kamloops are the only rainbow trout that can be harvested in Minnesota’s portion of Lake Superior. The Kamloops fishery is a relatively low cost hatchery program that provides both a winter and early spring shore fishery for rainbow trout where it otherwise would not exist. An alternative to elimination of the program is to restrict Kamloops stocking to a limited geographic area and attempt to reduce straying from that area so the hybridization risk is minimized.

7) Why does this plan put so much emphasis on the Knife River system?

The Knife River system contains about half of all migratory fish habitat in Minnesota and in the past has had one of the largest steelhead runs. The draft plan proposes to stock yearling steelhead to bolster the Knife River run, as the numbers of adult fish have not increased significantly. Although survival of hatchery-reared yearlings has been disappointing, they can have a significant impact on the number of adults returning to a stream, if a large number of yearlings are stocked in that stream. Analysis of wild downstream migrants captured in the Knife River smolt trap suggests declining returns of adults in 2005 and 2006. The option of not stocking the stream and letting it recover without intervention is appealing, however, rehabilitation would probably take much longer.

8. Why doesn’t the MNDNR increase the number of steelhead smolts stocked?

Raising steelhead smolts is expensive and production costs average between $2.50 and $3.00 per fish. The return rate of adults derived from stocked steelhead smolts has been disappointing, averaging about one percent since the program began. Much of the scientific literature suggests that significant genetic risks accompany hatchery intervention in the rehabilitation of wild steelhead populations. However, many anglers feel this risk is worth taking, and that there may be an even greater risk in allowing the present population to decline further. Stocking high numbers of hatchery-reared smolts in the Knife River where the outcome can be evaluated will help determine the effectiveness of this strategy.

9) Why does the MNDNR continue to stock steelhead fry as part of the proposed management plan?

Stocking steelhead fry above natural barriers to supplement natural reproduction of steelhead in short run streams has been a successful method to increase smolt production. Information gained from the French River smolt trap indicates that smolts produced from stocked fry are ten times more likely to return as adults than hatchery-reared yearlings. The creation of a “wild” steelhead brood stock should supply a stable source of gametes for fry production. This is an experimental program, and will require some modifications to optimize, but has potential to significantly increase smolt production in streams where fry are stocked.

10) Will there be any new regulation changes with the revised plan?

No, the plan proposes to continue restrictive harvest regulations to protect wild steelhead while allowing harvest of hatchery-reared Kamloops. The MNDNR will work with interested anglers to explore the need for additional spawning closures on specific streams.

11) Will the MNDNR ever allow harvest of wild steelhead?

As the rehabilitation process proceeds and adult steelhead abundance increases, we will consider relaxing restrictive harvest regulations on a group of streams that would be monitored extensively to determine how angling pressure and the steelhead populations respond. Based on what is learned from this experimental approach we would develop and discuss new, less restrictive regulations with interested anglers.

12) What does the MNDNR do to protect and/or restore stream habitats within the Lake Superior watershed?

Identification and removal of beaver dams and other obstructions by the MNDNR increases the spawning and nursery habitat available to steelhead. Sediment control through the review of development permits, consultation on roadway construction and culvert sightings, bank stabilization, and cooperative rip-rap projects are methods used by the MNDNR to minimize the erosion of stream banks. Easement and land acquisition programs along stream corridors have increased, but are expensive. Cooperative in-stream habitat improvement projects have been conducted by local angling groups and the MNDNR with the goal of increasing smolt production. On a broader scale, the MNDNR works with other agencies and private landowners to implement and monitor the success of watershed scale projects such as those on the Knife, Nemadji and Flute-Reed rivers. Efforts to coordinate with foresters and other land managers to positively influence vegetation management in the riparian zone and sub-watersheds will continue to be important to protecting and maintaining the water quality of North Shore streams.

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