Salmon management

Chinook Salmon

History

Chinook salmon were first introduced into Lake Superior by the Michigan Department of Natural Resources in 1967. Minnesota introduced spring-run chinook salmon in 1974 and converted to the fall-run chinook salmon in 1979. This change was made because fall-run fish demonstrated better growth rates and because disease-free spring-run eggs were not available. A detailed investigation of the spring run chinook salmon and a preliminary review of the fall run chinook salmon introduction were undertaken in 1984. When the chinook salmon program was started, it was expected to create a put-grow-take fishery with no natural reproduction.

The percent return (number of fish returned per number. of fish stocked) of adults to the French River trap has varied between approximately 0.2% and 2.0%. from 1991 to 1995, the percent return to the trap declined, and averaged only 0.5%. From 1980 to 1995, the percent return of chinook salmon to the angler in the summer creel has ranged from approximately 0.1% to 1.0%. The percent return of chinook salmon to the fall creel ranged from approximately 0.1% to 0.8% . Combined return rates from the summer and fall creel surveys range from 0.3% to 1.1%. The number of adult chinook salmon returning to the French River trap decreased from 1990 to 1995 . Total angler harvest in the summer fishery has fluctuated, but from 1980 to 1995 averaged 1,632 fish. During the five years when fall creel surveys were conducted, the average annual angler harvest was 1,578 fish.

In 1987, a lake-wide stocking evaluation began to determine the contribution of stocked (fin-clipped) and naturally reproduced (unclipped) fish in the anglers catch and to document the movement of stocked fish throughout the lake. Preliminary results of the study showed substantial natural reproduction throughout the lake. In Minnesota waters preliminary results of the lake-wide stocking evaluation have shown that, in the summer fishery, approximately 50% of the chinook salmon were naturally reproduced, approximately 40% were stocked by Minnesota and 10% were stocked by the other agencies. In the fall stream fishery only 25% of the chinook salmon were naturally reproduced, 70% came from Minnesota stocking and 5% were stocked by other agencies. Returns to the French River trap were 95% Minnesota stocked fish and 5% naturally reproduced fish with only an occasional fish stocked by another agency.

The discovery of bacterial kidney disease (BKD) in chinook salmon from Lake Michigan alerted the French River hatchery staff to investigate BKD in the French River run. Since 1990, paired spawning and a detection method for BKD, called ELISA, have been used on chinook salmon taken for spawn from the French River. Only eggs that are BKD-free have been used for production of brood runs at the French River.

Goals and Objectives

Goal: Provide a sport fishery that allows anglers the opportunity to harvest a trophy size fish.

Objectives:

  1. Manage chinook salmon by stocking up to 350,000 fingerlings so they do not severely affect the stability of the Lake Superior fish community.
  2. Provide an average annual catch of approximately 1,600 chinook salmon to the trolling fishery and 1,000 chinook salmon to the fall stream fishery, realizing that there will be large annual fluctuations.
  3. Use chinook salmon returning to the French River trap to supplement food shelf programs.

Present Management

Regulations - There is no closed season for chinook salmon. The bag limit is 5, or up to 5 when combined with coho, pink and Atlantic salmon. There is a minimum size limit of 10 in.

Stocking - Four streams are annually stocked with a total of 355,000 pre-smolt chinook salmon fingerlings. The MNDNR takes eggs from chinook salmon returning to the Swan River in lake Huron and rears them to fingerling size (100/lb) at the French River Cold Water Hatchery. All eggs taken for the chinook salmon program are tested for BKD and only BKD free eggs are used to produce the feral broodstock. The DNR will continue to stock chinook salmon as long as at least 75 pair of BKD-free chinook return to the Fench River trap for three or more consecutive years.

Assessment - Chinook salmon are assessed by three methods in Minnesota: creel surveys, charter captain reports and returns to the French River trap. The summer creel survey monitors chinook salmon harvested in the boat fishery and the fall creel survey monitors chinook salmon caught in the streams during the spawning run. Very few chinook salmon are taken incidentally in assessment nets. Stream surveys that target juvenile steelhead have sampled a small number of naturally reproduced chinook salmon.

Proposed Management

Regulations - No season or size limit change.

Stocking - If chinook salmon numbers decline to the level where less than 150,000 fingerlings can be produced annually from gametes collected at the French River trap for three years in a row, the dynamics in Lake Superior indicate that the program is no longer viable in its present form and the elimination of stocking should be considered.

Assessment - Continue to use the French River trap for determining percent return. The Knife River trap will be operated during the fall to assess the number of chinook salmon entering a river that is not stocked. Conduct a fall anadromous creel survey every other year and a summer lake creel survey annually to monitor angler harvest. Evaluate the catch of chinook salmon at Chester Creek to determine if continued stocking is productive. Continue to monitor and summarize charter captain reports annually.

Justification

A more consistent return of stocked chinook salmon would be beneficial to both anglers and fishery managers. Experimentation with increased size at stocking may show an increase in survival and make returns more predictable. To increase the size of chinook salmon stocked, the number of hatchery-reared fish must be reduced since hatchery space is limited. By reducing numbers, the cost per fish will increase. If survival of stocked fish is improved, by increasing the size at stocking, both numbers and pounds stocked should be reduced so predatory impact does not increase. Chinook salmon harvest at Chester Creek should be examined carefully, because it may provide only a very limited fall stream fishery and a very brief summer fishery. The success of chinook salmon stocking in this stream may be limited by its marginal physical characteristics and the relatively warm summer temperatures in that area of the lake.

Chinook salmon consume more forage per individual than any other Lake Superior species (Negus 1995). In Lakes Michigan and Ontario, chinook salmon are the major predators consuming alewife stocks. Some agencies on those lakes have drastically reduced the stocking quotas for chinook salmon and are concerned about their impact on the fish community (Jones et al. 1993). In Lake Superior, the abundance of rainbow smelt, presently the major forage of chinook salmon (Conner et al. 1993), has declined severely since chinook salmon were first stocked by Michigan in 1969 (see forage chapter). Lake herring abundance has increased, but has not yet reached historical levels (Selgeby and Slade 1994). Limited evidence suggests that chinook salmon have slowly started to change their feeding habits and are now consuming some lake herring along with rainbow smelt. The impact of stocking high numbers of chinook salmon on the fish community is unknown, but is a major concern. A conservative approach to chinook salmon stocking is warranted now that they have become naturalized in Lake Superior.

If survival of stocked or wild chinook salmon increases significantly in the future, or information collected shows declining forage stocks, salmon stocking must be reduced. If the number of adult chinook salmon returning to the French River trap produce fewer than 150,000 fingerlings per year in the hatchery, over a 3 year period, the conditions in the lake have changed and can no longer support the chinook salmon program in its present form. If these criteria are met, continuation of the program should be reevaluated. Gametes collected from a source other than the French River violate the logic this criteria is based on.

Information Needs/Community Interactions

Information on the interaction between chinook salmon and their forage base, and between chinook salmon and other predators in Lake Superior, is necessary before stocking quotas are increased. A hydroacoustic assessment of the forage base would estimate the biomass of forage available. Once the forage biomass is known, the allocation of the forage biomass among predator species and the commercial operators can be determined. Hydroacoustics could also provide information on seasonal habitat selection by chinook salmon. Diet studies of chinook salmon should be conducted at least once every five years to evaluate changes. Seasonal and juvenile diet studies also need to be conducted. Better estimates of survival at different ages need to be determined. Movements and distribution of chinook salmon throughout the lake are poorly understood and abundance estimates need to be refined. Initial bioenergetics modeling has been completed, but the model should be refined using the new information listed above.

Coho Salmon

History

Coho salmon were stocked in the Minnesota waters of Lake Superior from 1969 through 1972 (Hassinger 1974). Stocking was discontinued in 1972 based on slow growth rate, small size of creeled fish, low return rate, late spawning migration, high cost of the hatchery product compared to chinook salmon and low interest by anglers. Because management goals for coho salmon were not met, the program was abandoned in favor of the chinook salmon program in 1972. Currently, Michigan is the only agency on Lake Superior that stocks coho salmon, with an annual quota of 200,000. Peck (1992) found that, in Michigan waters, stocking contributes less than 10% to the overall coho salmon fishery and has made the recommendation to discontinue coho salmon stocking.

Since the early stocking efforts, coho salmon have become naturalized throughout Lake Superior and are second only to the lake trout in frequency of catch by Minnesota anglers. Spawning occurs in Minnesota tributaries, but reproductive success is low due to limited habitat. Natural reproduction in other areas of the lake and the migratory nature of coho salmon account for the fishery which has become established in Minnesota waters. Because coho salmon have only a three year life cycle and are self-sustaining, the harvest fluctuates widely. From 1979 to 1992, the harvest of coho salmon ranged from 1,024 to 11,652 fish (Figure 7.1). A strong or weak year-class can greatly effect the fishery. The average summer harvest of coho salmon in Minnesota waters from 1979 to 1992 was 4,115. The location of the coho salmon catch and the size of the fish caught changes seasonally in Minnesota waters. Smaller fish are caught in MN-l from April to June, slightly larger fish are caught in MN-2 during June and July and the largest fish are caught in MN-3 during August and September. A growing winter fishery for coho salmon has become established in the northern portion of MN-l and southern portion of MN-2. The fall fishery for coho salmon in Minnesota is very limited.

Since the early 1970's, anglers have looked beyond the relatively small size of coho salmon, and have accepted the fish because of it's catchability, exceptional fighting characteristics, and fine eating qualities. There is renewed interest by some anglers to reestablish a stocking program for coho salmon. Coho salmon are a low priority species for a hatchery program for the following reasons:

  1. Coho salmon are expensive to rear since they spend 1.5 years in the hatchery system before being stocked. This requires more raceway space, food and personnel compared to fish that are reared to fingerling size.
  2. Most coho salmon recruit to the anglers' catch at age 2 and are only available for one year before they die.
  3. In Minnesota, coho salmon have returned to streams too late for a popular fall stream fishery (late October - late November).
  4. In the Michigan waters of Lake Superior, when hatchery reared coho salmon were stocked into waters that already supported wild populations, their contribution to the fishery was poor (Peck 1992).

Combined, these factors create a very expensive hatchery product that is only available to anglers for a very short period of time.

Goals and Objectives

Goal: Provide a coho salmon fishery sustained by natural reproduction.

Objectives:

  1. Sustain an average annual catch of 4,000 coho salmon from the summer fishery based on natural reproduction.
  2. Evaluate the use of regulations to distribute the coho salmon catch among a larger group of anglers.
  3. Cooperate and coordinate closely with Wisconsin on wild coho salmon management since very little production of coho salmon occurs in Minnesota tributaries.

Present Management

Regulations - There is no closed season for coho salmon. The bag limit is 5, or an aggregate of 5 when combined with chinook, pink and Atlantic salmon. There is a minimum size of 10 in.

Stocking - No stocking has been done in Minnesota since 1972.

Assessment - Coho salmon in Minnesota are assessed by three methods: creel surveys, charter captain reports and returns to the French River trap. In most years fewer than 25 coho salmon are captured at the French River trap. Very few are taken incidentally in lake trout assessment nets. Stream surveys targeting juvenile steelhead have sampled a small number of naturally reproduced coho salmon.

Proposed Management

Regulations - No change in season or size limit.

Stocking - Do not initiate a stocking program.

Assessment - Initiate a winter creel survey and repeat once every 3 years. Continue to conduct a summer lake creel survey annually and a fall anadromous creel survey every other year to monitor angler harvest. Continue to monitor and summarize charter captain reports annually. Monitor the French River trap and Knife River trap to count adults entering those two rivers. Work closely with Wisconsin to determine what proportion of the coho salmon harvested in Minnesota are produced in Wisconsin.

Justification
Since coho salmon have provided a high quality fishery based on natural reproduction and a hatchery program would have a low benefit:cost ratio, no stocking is recommended. There is concern among biologists that high numbers of coho salmon could affect other Lake Superior species. Coho salmon ascend tributary streams each fall in search of spawning habitat and use spring upwellings when available. They probably utilize some of the same spawning areas and food items as brook, brown and rainbow trout (Fausch and White 1986). In the lake, coho salmon have less impact than chinook salmon on large forage species and this reduces the competition with adult lake trout and chinook salmon. The coho salmon diet probably overlaps with that of rainbow trout and with juveniles of all species in the lake. The year-class strength of coho salmon fluctuates based on stream conditions during early life stages and abundance of parental stock, which could be affected by a combination of fishing mortality and predation. Since the life cycle of coho salmon is only 3 years, and the spawning population is made up of only one year class (3-year old), fluctuations in population size can be extreme and will be reflected by annual variations in angler harvest.

Information Needs/Community Interactions

More information on the interactions between coho salmon and their forage base, and coho salmon and other species in Lake Superior is necessary. Diet surveys conducted every 5 years are needed to identify overlaps between coho salmon and other Lake Superior species at all life stages, in the lake and streams. The reduction in possession limit may allow more escapement of spawners during years of low adult abundance and may also distribute the available catch among more anglers. In most years, a relatively large winter fishery for coho salmon takes place in the Two Harbors area. A winter creel survey should be developed and repeated every three years to monitor this fishery. Habitat utilization and seasonal movement patterns of coho salmon should be determined using hydroacoustics, and possibly telemetry, to enhance our understanding of their role in the Lake Superior fish community.