|
by: Lee E. Newman
Abstract |
Introduction |
Objectives |
Study Sites |
Methodology |
Stocking |
Assessment
Results |
Discussion |
Potential
Applications |
Acknowledgments |
Literature Cited
Abstract - This cooperative project of the Grand Portage Tribe and the U.S. Fish and Wildlife Service employed a comprehensive approach toward reestablishing a naturally reproducing coaster brook trout Salvelinus fontinalis population in reservation waters. Lake Superior basin, native coasters (Nipigon strain) were stocked as eyed eggs or fry in three small streams that were historic coaster production habitats. Concurrent with the reintroductions, the Grand Portage Tribal Council and Natural Resources Department effectively mobilized community support for the restoration effort and for self regulation of the harvest. Adult, spawning stage coasters as large as five pounds have entered the stocked streams in five consecutive years and natural reproduction has been documented. This small project provides encouraging evidence of the feasibility of rehabilitation of coaster stocks and may serve as a model for reintroductions in suitable habitats throughout the Lake Superior basin and possibly the Lake Michigan and Lake Huron basins as well.
Brook trout Salvelinus fontinalis, were once abundant and widespread along most of Lake Superior= s 4,385 km of shoreline and entered more than 120 tributary stream systems to reproduce. They were also abundant in Lake Nipigon and common along the shoreline of, and in the tributaries of approximately the northern half of Lake Huron and Lake Michigan. Locally called "coasters", these large, anadromous or shoal spawning brook trout were prized for their size, beauty and food qualities (Shiras 1935, Roosevelt 1865).
Beginning with the arrival and colonization of the Lake Superior region by Europeans during the 1800's, coaster populations were heavily over exploited. Their qualities as a game fish created a world class fly fishery that attracted an international following and their qualities as a food fish fueled an intense local hook and line fishery, and to a lesser degree, a commercial net fishery (Newman and DuBois 1996). These unregulated fisheries decimated native coaster stocks in the time period from 1850 to 1900. As further development of the area proceeded, logging, wildfire, agriculture, mining and other land uses may have also contributed to their decline.
Exotic salmonids (rainbow trout, brown trout, and coho, chinook, pink and Atlantic salmon) were introduced to Lake Superior and may have competed with the coaster populations. Access to springs providing critical spawning habitats (Curry and Noakes 1995) was blocked by road construction and dams for public and private fish hatcheries (Smith and Moyle 1944).
By the early 1900's, only a few, small remnant populations of coasters remained, usually in remote areas, isolated from large human populations. At present, the only known coaster brook trout populations of significant size are found in Ontario's Nipigon District, around Isle Royale and in the private land holdings of the Huron Mountain Club in the Upper Peninsula of Michigan (Newman and DuBois 1996).
Attempts have been made to restore coaster populations in Lake Superior by stocking fingerling and yearling hatchery brook trout on a sporadic basis for more than 100 years. These attempts have consistently produced very low return rates and have not resulted in the establishment of natural reproduction (Smith and Moyle 1944). Wisconsin DNR (B. Swanson, WI DNR, Bayfield WI, person. commun.) also reports low return rates from stockings made from about 1980 to 1994. Participants in a 1992 Workshop on Lake Superior brook trout speculated that the lack of success of past stockings may have been due to stocking the wrong life stage or genetic strain, overharvest of juveniles, the lack of fitness of hatchery reared fish, or that homing or spawning instincts were not properly imprinted, (Minutes, Workshop on Lake Superior Brook Trout, Grand Portage, MN July 27-28, 1992).
Coaster brook trout have been extirpated from Grand Portage Reservation waters since about 1950. Causes of the decline were overfishing, habitat degradation and possibly competition with introduced salmonids (Smith and Moyle 1944).
The fish community objectives for Lake Superior (Busiahn 1990) call for the restoration of depleted stocks of native fish species, and the Lake Superior Brook Trout Rehabilitation Plan (Newman et al., 1999) specifically outlines an approach to coaster brook trout rehabilitation. In accordance with these objectives, the Ashland National Fish & Wildlife Conservation Office (NFWCO) of the U.S. Fish and Wildlife Service and the Grand Portage Natural Resources Department have initiated a cooperative project to reintroduce coaster brook trout to reservation waters.
The ultimate objective of this project is to restore one or more viable, self-sustaining stocks of coaster brook trout in the waters of Lake Superior and its tributaries at Grand Portage. As specific biological information regarding coaster brook trout is virtually non-existent, adaptive management techniques were employed, and methodology designed to evaluate the innovative stocking techniques used and to provide information regarding the biology, habitat use and life cycle of the coaster. We also designed the evaluation to provide information regarding the interaction of coaster brook trout with the naturalized stocks of rainbow trout and coho salmon using the stream and lake habitat of the study area.
At Grand Portage three streams with suitable coaster habitat were selected as study sites. The streams all supported coaster brook trout populations in the past, but no brook trout have been reported from them in the last 40 years, except for a few in the 1970's that resulted from stockings made during that period (USFWS, Ashland NFWCO-unpublished file data).
The streams selected for the reintroductions are typical of the Minnesota north shore of Lake Superior. They are primarily fed by surface water and have low groundwater inputs. They have steep gradients, predominantly freestone and bedrock substrates and have highly variable flow and temperature regimes. In general, they have long been considered as marginal trout streams (Smith and Moyle 1944). Two of the streams (Grand Portage Creek and Little Lake Creek) discharge into Lake Superior in Grand Portage Bay, a sheltered bay of 500 hectares surface area with a maximum depth of 7 meters. The other stream (Hollow Rock Creek) discharges into Lake Superior along an unprotected shoreline with steep cliffs and abrupt drop offs to depths of 20 to 50 meters.
Water is supplied to Little Lake Creek by a small watershed (81 ha) through several springs with a combined output of < 1.0 cfs. Length from headwaters to Lake Superior is 0.5 km, and access to anadromous fish is blocked by a perched highway culvert barrier at the mouth and by beaver dams. Maximum flow rates are unknown.
Grand Portage Creek has a total length of 7.0 km and a watershed of 2055 ha. The only barrier to upstream movement of anadromous fish is the box culvert under Minnesota Highway 61 which is 1.4 km from the mouth. A fish passage tube installed in the culvert in 1959 has not provided consistent upstream access for the steelhead population, but modifications made to the structure in late 1993, have allowed steelhead to pass upstream. The average annual flow rate is 3.5 cfs, and maximum rates may exceed 100 cfs.
Hollow Rock Creek is subject to more extreme flow fluctuations than Grand Portage Creek. Maximum and minimum flows are unknown but an average flow for 1984 was recorded as 3.0 cfs, based on four measurements during the year (all spring readings). During 1998 low flows of <1.0 cfs were observed during August and January. A natural falls 0.4 km from the mouth is a barrier to fish passage.
This reintroduction effort focused on a number of areas suspected of being important to coaster brook trout:
To maximize early acclimation and imprinting, the earliest life stages possible were used for the experimental reintroductions (eyed eggs and early stage fry).
The one regional native broodstock available, the Lake Nipigon strain, was selected for use in this reintroduction.
Reintroductions were made into historic habitats where we believed suitable conditions still existed.
Survival, growth and distribution of stocked fish were measured as frequently as could be achieved.
An intensive effort was made by the Grand Portage Tribal Natural Resources Department to provide tribal members and local residents with information on coaster brook trout biology and their needs for extraordinary protection to achieve spawning sizes and ages.
The study streams were stocked with Nipigon Strain brook trout during the time period from 1992 through 2000 (Newman 1995). Eyed eggs were stocked in Little Lake Creek and early stage fry in Grand Portage and Hollow Rock Creeks. Egg stocking was done directly into stream substrates where groundwater upwellings occurred using a technique similar to that described by Gustafson-Marjanen and Moring (1984). Incubators placed in the substrates were used to evaluate hatch success (Newman 1995). Fry (from the same lot of broodstock that produced the eggs stocked in Little Lake Creek) were stocked into stream segments on Hollow Rock and Grand Portage Creeks where habitat potentially suitable for coaster reproduction was present. Fry were stocked both below and immediately above barriers to anadromous fish passage. No stocking of brook trout on reservation waters was done in 1997 to provide a definitive opportunity to evaluate any natural reproduction resulting from the introductions.
To monitor the abundance, growth and maturation of brook trout produced by the introductions, data was collected from several sources:
Annual monitoring of juvenile salmonid populations in the study streams was done by backpack electrofishing during the second week of August each year from 1992 through 2000, and at least twice more each summer as personnel were available.
Compilation of catch data by Grand Portage tribal personnel was done periodically by interviewing sport fishermen and tribal commercial fishermen during 1995 to approximate catches of brook trout in reservation waters of Lake Superior from June 1 to November 1, 1995. Brook trout caught by Grand Portage Natural Resources Department personnel, incidental to other fisheries projects during biological assessments in 1995, were also included.
Annual spawning stream sampling, below barriers, was conducted from October through early November 1994 through 1999. Stream segments below barriers on Hollow Rock Creek and Grand Portage Creek were sampled by backpack electrofishing to determine if adult brook trout were returning to spawn. All sexually mature fish were measured and scale sampled for age composition.
Distribution, movement and habitat use by adults was monitored by radio telemetry.
Egg stocking
The survival rate (eyed egg to swim up fry) found in test incubators ranged from 84% to 100% where incubators were properly placed (Newman 1995). In Little Lake Creek, numerous brook trout fry were observed in the areas stocked when the incubators were lifted and young of the year (yoy) were observed to be common (1993-1996 and 1998-2000), and adults were captured annually in the stream from 1994 through 1999. As this stream had no brook trout population before eggs were introduced, the only likely source was the egg stocking. This stream has an impassable fish barrier (perched road culvert) at the outlet and fish can not re-enter from Lake Superior.
Fry stocking
Fry stocking resulted in yoy and yearling brook trout year classes in Hollow Rock and Grand Portage Creeks in each year stocked. Monitoring in stream and in Lake Superior has shown that:
The number of brook trout observed per station was lower than the number of rainbow trout in all stations where lake access is available.
Juvenile rainbow trout abundance and growth rates have not changed since the introduction of brook trout in 1992.
Abundance of yoy brook trout was generally higher in stream samples above migration barriers (without rainbow trout), than below barriers where they competed with rainbow trout.
Brook trout yoy growth above barriers was slightly better than below barriers (by an average of 0.76 cm by August 10). Yearlings averaged 1.52 cm larger than their cohorts below barriers. The difference is likely the result of competition with the rainbow trout below barriers.
Age1 fish in Lake Superior on August 10 were 2.58 cm longer than their cohorts in the streams. Either the lake caught fish had begun to grow faster than those staying in streams, or fish immigrating to Lake Superior were the larger and faster growing individuals in the population.
Coloration and markings of the lake caught brook trout were markedly different from those in stream. Markings (vermiculations and spots) were pale and indistinct while silver color was pronounced, particularly in age 2 or older fish.
Emigration of juvenile brook trout from the streams was usually complete during the yearling year, but emigration and immigration occurred whenever stream conditions warranted.
Radio tagged adults in Lake Superior used shallow water (< 7 m) and nearshore areas (<150 m) from shore exclusively, and usually did not travel more than 20 km from there capture location.
YOY brook trout captured in Hollow Rock Creek (a year when no brook trout were stocked).
Production of adult fish
No means were available for conducting an accurate survey of the number of coasters produced by these reintroductions, either in the streams or Lake Superior. However, it was observed that:
A total of 20 A adult@ brook trout (> 305 mm) were reported caught in Lake Superior during 1995 in tribal subsistence nets and 18 caught by anglers in the tribal marina (the only place where anglers were sampled). A total of 60 brook trout were caught in Lake Superior by tribal natural resources department personnel incidental to other fisheries projects. The 98 brook trout were all age 2+ to 4+. These 98 fish represent an unknown portion of the total population.
Fall sampling of Hollow Rock and Grand Portage Creeks on a few occasions each year from 1995 through 1999 produced from 10 to 25 individual, adult fish in each stream per year.
Age and length at maturity:
Table 2- Length and sex data, 52 sexually mature coasters captured in Hollow Rock and Grand Portage Creeks from 1995 through 1999
| Scale age of fish |
Males Number in sample/average length |
Females Number in sample/average length |
|
1+ |
N=2/23.1 cm |
N=0 |
|
2+ |
N=3/31.7 cm |
N=1/28.9 cm |
|
3+ |
N=20/43.2 cm |
N=22/46.2 cm |
|
4+ |
N-2/49.2 cm |
N=2/52.3 cm |
Public education and community involvement
Personnel of the Grand Portage Natural Resources Department were highly successful in generating interest in and support for restoration of coaster brook trout. The effort included educational presentations and personal contact with all age groups. Special emphasis was placed on elementary and high school students who were provided field and class room experiences with the project. Tribal members and local residents developed a strong sense of ownership and pride in this project and a solid understanding of coaster biology. This understanding was vital to the voluntary catch and release program that allowed coasters to survive to reproductive size and ages.
We have concluded that the technique of stocking eyed eggs on created or improved spawning substrates is a promising method for the reintroduction of extirpated stocks of brook trout, particularly where good spawning and rearing habitats exist. These tests demonstrated that high hatch rates can be produced in a variety of substrates and habitats.
We theorize that brook trout produced by stocking eyed eggs will have substantial survival advantages over those stocked as fingerlings or yearlings from hatchery sources. Acclimation to natural conditions, synchronization of life cycle with natural food supplies and the imprinting of homing instincts will be nearer to that of naturally reproduced wild fish. Costs are low for the eyed egg stocking technique in streams. This method also compares favorably to the use of Vibert boxes where substantial costs are involved and regular maintenance and cleaning are required while in use. We saw no evidence of fungus or disease in any of the egg stockings.
Employing the technique of stocking early stage fry may provide many of the same benefits as stocking eyed eggs. Costs are only slightly higher and early acclimation and imprinting could also be good, but has not yet been proven.
Among sexually mature fish returning to streams, the dominance of the age 3+ year class, especially in females, indicates that most coasters of the Nipigon strain will not mature sexually in the wild until this age, a pattern consistent with that found in the Nipigon River (R. Swainson, OMNR, Nipigon, person. commun.). Nipigons are known to be 95% sexually mature at age 2+ when grown in hatchery conditions at the Dorion (OMNR) Fish Culture Station (J. Sagar, Manager). However, sexual maturation in the wild environment appears to be delayed by anadromy as suggested by Thorpe (1987). This maturation pattern may be the key element in managing coaster populations. With the obvious vulnerability of all brook trout to over harvest, protection of adults to allow for spawning twice before harvest will likely require size limits over 50 cm (20 inches) as suggested in the Lake Superior Brook Trout Rehabilitation Plan (Newman et al., 1999).
The total number of coaster brook trout in Lake Superior produced by the introductions at Grand Portage and how those fish have distributed in Lake Superior is largely unknown. The stream habitats used are so small that total production is not very high. We believe however, that at least 3 year classes (ages 2 through 4) are fairly abundant along about 20 km of shoreline in the vicinity of Grand Portage and assume that perhaps 30 to 50 adults are returning to attempt to spawn in each of the two streams.
Conclusive evidence was found in 1997 to show that the reintroduced coasters at Grand Portage are reproducing. The standard stations on Hollow Rock Creek produced about 40 yoy, that were concentrated below the falls that is the first anadromous fish barrier. We suspect, but can not be sure, that this may be the site where successful spawning occurred. In 1998 and 1999, yoy brook trout sampled in Grand Portage Creek showed an unusual bi-modal distribution of lengths. We suspect that this was the result of having both a hatchery and a naturally reproduced year class of yoy present. If successful reproduction of coasters is occurring in both of these marginal trout streams, it is an indicator that spawning habitat may not be as severely limited as expected, either here or in other Lake Superior streams.
Our results suggest that vital elements of future successful coaster brook trout population reintroductions will include biological factors such as using native strains and stocking appropriate life stages in suitable habitats. Most importantly, stocks will require protection to reach the unusual sizes and ages that are needed by coasters. The protection may be possible through special regulations, but ideally it might be best provided by an informed and motivated community as was the case at Grand Portage.
The scale of this project was so limited that the area affected is only about 1.8 km of anadromous habitat and 30 km of Lake Superior shoreline. The populations involved are so small that their continued existence is tenuous at best. However, the exciting possibility does exist that the techniques applied here might be applicable to many of the120 historic coaster streams and much of the 4,385 km of shoreline on Lake Superior where coaster stocks have been extirpated. There may also be potential for reintroductions in some habitats on Lake Huron and Lake Michigan.
The author acknowledges that the success of this project is fully due to individual members of the Grand Portage Reservation, the Tribal Council and the personnel of the Grand Portage Natural Resources Department. Without their enthusiastic support and hard work, none of it would have been possible. Thanks are also extended to the Ontario Ministry of Natural Resources personnel for their technical advise, for supplying the eggs and fry stocked in this project, and for their enthusiastic support of coaster brook trout restoration at both Grand Portage and throughout Lake Superior.
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