Appendix 67 A Review of Bull Trout Life-History and Habitat Use in Relation to Compensation and Improvement Opportunities

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Appendix 67 A Review of Bull Trout Life-History and Habitat Use in Relation to Compensation and Improvement Opportunities A REVIEW OF BULL TROUT (SALVELINUS CONFLUENTUS) LIFE-HISTORY AND HABITAT USE IN
Appendix 67 A Review of Bull Trout Life-History and Habitat Use in Relation to Compensation and Improvement Opportunities A REVIEW OF BULL TROUT (SALVELINUS CONFLUENTUS) LIFE-HISTORY AND HABITAT USE IN RELATION TO COMPENSATION AND IMPROVEMENT OPPORTUNITIES by J.D. McPhail and J.S. Baxter Department of Zoology, U.B.C., 6270 University Boulevard, Vancouver, B.C. V6T 2A9 Fisheries Management Report No A Review of Bull Trout (Salvelinus confluentus) Life-history and Habitat Use in Relation to Compensation and Improvement Opportunities by J.D. McPhail and J.S. Baxter Department of Zoology, U.B.C., 6270 University Boulevard, Vancouver, B.C., V6T 2A9 Fisheries Management Report No Canadian Cataloguing in Publication Data McPhail, J. D. (John Donald), A review of bull trout (Salvelinus confluentus) lifehistory and habitat use in relation to compensation and improvement opportunities (Fisheries management report, ISSN ; no. 104) Issued by Fisheries Branch Includes bibliographical references: p. ISBN Bull trout. I. Baxter, J. S. II. British Columbia. Ministry of Environment, Lands and Parks. III. BC Environment. Fisheries Branch. III. Fisheries Management report (BC Environment. Fisheries Branch) ; no QL638.S2M '.55 C i Abstract McPhail, J. D., and J. S. Baxter A review of bull trout (Salvelinus confluentus) life-history and habitat use in relation to compensation and improvement opportunities. Fisheries Management Report No. 104, 35 p. The bull trout (Salvelinus confluentus) is a char endemic to western North America. It has had a confused taxonomic history, and its specific distinction from the Dolly Varden (Salvelinus malma) is still in doubt. In the areas where the two nominal species overlap there is evidence of hybridization and even introgression. This taxonomic problem has management implications, and will only be solved by studies in the areas of geographic overlap. The bull trout spawns in the fall (September to October) in flowing water. The threshold spawning temperature is around 9 C. Courtship and spawning behaviour are similar to other char. The female chooses the deposition site and digs the redd. The degree of sexual dimorphism varies among populations, but in most populations males develop bright spawning colours and a kype, while females are less colorful. The eggs are about 5-6 mm in diameter and optimal incubation temperature ranges from 2 to 4 C. In the wild, fry emerge approximately 220 days after egg deposition. Newly emerged fry are secretive and hide in the gravel along stream edges, and in side channels. Juveniles are found mainly in pools, but also in riffles and runs. They maintain focal sites near the bottom and are strongly associated with instream cover, especially overhead cover. Juveniles feed primarily on aquatic insects taken from the bottom or from drift. As they grow, their diet shifts to fish, and most adults (except for stream residents) are piscivores. Like many char, the bull trout occurs as a number of life-history forms. The stream-resident form lives out its life in small headwater streams. It is often dwarfed and reaches sexual maturity at a small size, and sometimes at an early age. The fluvial form lives as an adult in large rivers but spawns in small tributary streams. It often attains a large size, reaches sexual maturity at about five, and undergoes long migrations between mainstem rivers and small tributary spawning streams. The lacustrine-adfluvial form has a similar life-history. It spawns in tributary streams but lives as an adult in lakes. It grows to a large size, usually reaches sexual maturity in about its fifth year, and often makes long migrations between lakes and spawning streams. A fourth possible life-history type is anadromy. The evidence for the existence of anadromous bull trout is still slim, but in the Puget Sound-Strait of Georgia region they probably occur. There has been no formal attempt to document the life-history of anadromous bull trout. The evidence for homing in migratory bull trout is equivocal, and some populations probably home with great fidelity while others show a high rate of straying. The genetic structuring of bull trout populations suggest that many populations have been through genetic bottlenecks . Genetic variability within populations is low, but genetic differences among populations often are marked. This, along with striking inter-population differences in nuptial colouration and sexual dimorphism, suggest the existence of distinct stocks. Adult and juvenile densities are often low, and the species is sensitive to environmental degradation and over-fishing. Human activities that create migration barriers, increase siltation, and increase variation in natural temperature and flow regimes within streams, are particularly harmful. Bull trout do not do well in competition with introduced salmonids, and there is evidence that introduced lake trout have replaced bull trout in a number of lakes. Bull trout are declining in numbers throughout their range, especially at the southern edges of their distribution where a number of populations have become extinct. Unfortunately, opportunities for enhancement are limited, and the major hope for restoring bull trout numbers lies with regulation (e.g., closures, gear restrictions and harvest limits) and public education. ii Acknowledgements This review was made possible by the interest and help of a large number of people. Their assistance is gratefully acknowledged. University of BC: Gordon Haas, Nancy Keen, Edwin Landale, Dave O'Brien, Dr. E. B. Taylor, and Peter Troffe; Ministry of Environment, Lands and Parks: Poul Bech; Ted Down, Ted Euchner, Jay Hammond, Ross Neuman, Gerry Oliver, Erie Parkinson, Marvin Rosenau; BCHydro: Gary Birch, Yolanda Wiez; Aquatic Resources Ltd.: Tim Slaney; Pisces Environmental Consulting Services Ltd.: J. H. Allan; R. L.& L. Ltd.: Gary Ash, Larry Hildebrand, Curtiss McLeod; Washington Department of Wildlife: Paul Mongillo; Seattle Water Department: Katherine Lynch; Department of Fisheries and Oceans: Gordon Ennis, Cathy Gee, and AI Stobbart; Peter McCart; Diana McPhail produced the maps. Final editing and publishing was funded under an agreement with Forest Renewal B.C. (Project NumberBDSSP006-Habitat Requirements of Vulnerable Char Populations). iii Table of Contents Abstract Acknowledgements Table of Contents i ii iii 1.0 INTRODUCTION BULL TROUT LITERATURE BIOLOGY OF RELEVANT LIFE HISTORY STAGES Spawning Areas and habitat characteristics Season and conditions Behaviour Sex ratio Fecundity Sexual dimorphism Egg development and hatching Egg size Development rate Alevin size Fry habitat and feeding Fry habitat Fry behaviour Fry feeding Juvenile habitat and feeding Juvenile habitat Juvenile feeding Adult habitats and feeding Adult habitats Stream resident populations Fluvial populations Adfluvial populations Anadromous populations Adult feeding Growth and Maturity OTHER RELEVANT BIOLOGICAL FEATURES Migration and homing Migrations Homing Stocks Population size and controls Population size Population controls 17 iv Table of Contents (continued) 5.0 ENVIRONMENTAL IMPACTS ON BULL TROUT Impoundments Reservoirs Other impacts Logging, pipe lines, oil exploration, and road construction Recreational fisheries Interactions with other species Competition Hybridization OPPORTUNITIES FOR HABITAT COMPENSATION AND IMPROVEMENT Spawning habitats Egg development habitat Natural propagation Artificial propagation Fry habitat Juvenile habitat Adult habitat Public education and involvement programs Essential biological research REFERENCES 24 1 1.0 INTRODUCTION The bull trout (Salvelinus confluentus) is an endemic western North American char. Most of the species' original distribution (Fig. 1) was to the west of the Continental Divide, and extended from northern California (the McCloud River) and a few upper Snake tributaries in Nevada, throughout most of Oregon (from the Willamette system east), Washington, Idaho, inter-mountain Montana, British Columbia, and the southeastern headwaters of the Yukon system (Lindsey et al. 1981). In addition, the species was native to east-flowing rivers in the Rocky Mountain foothills of northern Montana (Brown 1971) and Alberta (Nelson and Paetz 1992). In British Columbia and Washington, the bull trout is an interior species found predominately in areas east of the Coast Mountains (Cascades). In recent years the bull trout's range has contracted, especially along its southern edges. Apparently, bull trout are now extinct in the McCloud River of California (Rode 1988) and, in the Willamette system in Oregon, the species has disappeared from at least three major tributaries (Goetz 1989). Its status in the Bruneau River, Nevada, where it was reported by Miller and Morton (1952) is unclear, but it is probably extinct. In Washington (Brown 1992) and Alberta (Carl 1985) there is evidence for precipitous declines in a number of populations. In British Columbia the major declines appear to be in the Columbia system and in the lower Fraser Valley (Hagen and Baxter 1992; Hagen 1993a, b; Gordon Haas, University of British Columbia, Vancouver, personal communication; Al Stobbart, Department of Fisheries and Oceans, Pitt River Hatchery, personal communication), along with other systems where overfishing has occurred. This loss of peripheral southern populations, and evidence of declines elsewhere, has led to a general concern about the status of bull trout and this, in turn, has resulted in an petition to list bull trout under the US Endangered Species Act. Under this act, the US Fish and Wildlife Service (Department of the Interior), is required to examine the available evidence and, within 90 days, determine whether a status review is warranted. This 90 day examination was positive (Federal Register, May 17, 1993) and a status review was completed in The review recommended that bull trout be listed in the conterminous United States, but that the information on population trends in Canada and Alaska is insufficient to warrant listing throughout the species entire range (Federal Register, June 10, 1994). One problem the status review did not grapple with is the bull trout's confused taxonomic history, especially with regard to its relationship to the Dolly Varden (Salvelinus malma). The bull trout was originally described from the Puyallup River, southern Puget Sound, in 1858 (Suckley 1858); however, for over one hundred years it was treated as either a subspecies, or a variant, of the Dolly Varden. In 1978, the bull trout was resurrected from synonymy and redescribed as a distinct species (Cavender 1978) but, even now, its taxonomic status and relationships are not clear. There is a growing body of information (chromosomal, morphological, and molecular) that indicates the Arctic char (Salvelinus alpinus) is the closest relative of the Dolly Varden, and that the bull trout represents a lineage distinct from the Dolly Varden-Arctic char lineage (Cavender 1980; Cavender and Kimura 1989; Grewe et al. 1989; Phillips et al. 1989; Haas and McPhail 1991; Phillips and Pleyte 1991). A serious problem with this conclusion is the geographic origin of the data. With one exception, Haas and McPhail (1991), it is based on studies of allopatric populations of bull trout and Dolly Varden; however, the critical test of a species is whether two forms can coexist without significant gene exchange (Mayr 1963). For example, the coastal and westslope cutthroat trout (Oncorhynchus clarki clarki and 0. clarki lewisi), have interior and coastal distributions much like those of bull trout and Dolly Varden; also the level of morphological differentiation between the two cutthroat trout is similar to that found between the two char. There is, however, no natural area of overlap in the geographic distributions of the two cutthroat trout. Consequently, their ability to coexist is untestable. Thus, their taxonomic status becomes a matter of judgement and, in this case, the weight of taxonomic opinion favours subspecific status for the two cutthroat trout (Benkhe 1992; Allendorf and Leary 1988). Fig. 1. Approximate original distribution of bull trout Salvelinus confluentus. 2 3 Therefore the presence of an area of overlap is a critical difference between the bull trout-dolly Varden situation and the two subspecies of cutthroat trout. Although the bull trout is primarily an interior species, and the Dolly Varden is a coastal species, in some areas the two forms come in contact. Indeed, it is their ability to coexist, apparently without extensive hybridization, that is the most compelling argument for their status as separate species (Cavender 1978; Haas and McPhail 1991; Baxter et al. in prep.). Their geographic ranges overlap where the Interior Plateau abuts against the Coast Mountains in northern and west-central British Columbia, and in the lower Fraser Valley, as well as in the Puget Sound and Olympic Peninsula regions of western Washington (Fig. 2). It is what happens in these areas of range overlap (sympatry) that is crucial to understanding the relationship between bull trout and Dolly Varden. Unfortunately, until recently research has focused on bull trout outside the area of overlap and, consequently, the picture in areas of sympatry is not clear. Although the data are sketchy, in northern and west-central British Columbia, Dolly Varden and bull trout appear to occur in the same river systems without extensive hybridization (Haas and McPhail 1991). In such areas, there are often clear ecological differences between the two char: the bull trout are usually the adfluvial form (adults in lakes but spawning in tributary streams), and Dolly Varden are permanent stream residents (Bustard and Royea 1995; McPhail personal observations). In contrast, in the more southern areas of overlap (e.g., the lower Fraser Valley and Skagit River) the situation is confused. At some sites both char are present, while at other sites only one or the other of the char is present, and at other sites there is morphological evidence of hybridization (Brown 1992; McPhail personal observations). In addition, in these areas, molecular markers (both mitochondrial and nuclear) that are diagnostic for each of the species in allopatry (Grewe et al. 1989; Phillips and Pleyte 1991) turn up in the wrong morphological species (McPhail and Taylor 1995). Such observations imply that in areas of contact, bull trout and Dolly Varden can, and do, exchange genes. This brings the specific status of the bull trout into doubt. Indeed, the two char show all of the attributes of classical subspecies (Bailey et al. 1954): clear morphological differences that are stable over most of their largely allopatric distributions, a small (relative to their allopatric distributions) area of overlap, and clear evidence of gene exchange within the area of overlap. In such cases, however, evidence of hybridization is not sufficient evidence of gene exchange. The critical issue is the fate of hybrids. Are hybrids between Dolly Varden and bull trout sterile, or can they backcross? Are they ecologically fit, or are they selected against because their intermediate morphology places them at an ecological disadvantage relative to pure Dolly Varden and bull trout? These are questions that need answers before a rational decision can be made on the taxonomic status of bull trout, and they are questions that can only be answered in the areas where the ranges of the two char overlap. In the two regions of British Columbia that are the focus of this review (the Columbia-Kootenay system and the Peace-Liard system) the taxonomic status of bull trout is of little concern. Only bull trout occur in the Columbia-Kootenay system, but in the Peace system (Thutade Lake tributaries) and the southwestern headwaters of the Liard there are both bull trout and Dolly Varden (Lindsey 1956; Haas and McPhail 1991; McPhail and Carveth 1992; Baxter et al. in prep.). Presumably, Dolly Varden colonized these regions by way of headwater captures of coastal drainages (the Skeena and Stikine rivers). As in other areas of overlap, there is morphological evidence for hybridization (UBC Fish Collection), and in the Thutade system both morphological and molecular evidence of gene flow (Baxter et al. in prep.) Both the lower Liard and lower Peace contain only bull trout, but it is not clear how far downstream in the Mackenzie system bull trout extend. There are records of char from many streams that rise in the Mackenzie and Richardson mountains (Hatfield et al. 1972) but no specimens are available for examination; however, a biologist experienced with bull trout, Arctic char and Dolly Varden (Peter McCart, Fisheries Consultant, Calgary, personal communication) reports bull trout downstream as far as the confluence of the Great Bear and Mackenzie rivers. In the upper Columbia and upper Kootenay systems, bull trout are widely distributed; however, in British Columbia they are curiously absent from western Columbia tributaries (e.g., Kettle, Okanagan and Similkameen rivers; McPhail and Carveth 1992). 4 Fig. 2. Approximate British Columbia distribution of bull trout (Salvelinus confluentus) and Dolly Varden (Salvelinus malma) showing areas of overlap. 5 2.0 BULL TROUT LITERATURE Most of the literature that specifically refers to bull trout is relatively recent. Before the bull trout was re-described in 1978, government agencies in both the US and Canada showed little interest in the species, and many anglers, at least in British Columbia, did not regard bull trout as a real sport fish. All this changed with the appreciation that bull trout were in decline, especially in the United States, and that they might qualify for protected status under the 1973 Endangered Species Act. After 1978, interest in the species on both sides of the border started to grow. In an early report on bull trout biology in the Arrow Lakes (McPhail and Murray 1979), the only paper cited from the primary literature (peer reviewed journals) that dealt with the life-history and ecology of bull trout was Cavender's re-description of the species (Cavender 1978). Through the 1980s, however, the literature on bull trout grew rapidly. Forty-one biologists attended the Flathead River basin bull trout conference (MacDonald 1985), and by 1989 a literature review of the biology of bull trout (Goetz 1989) listed 92 citations containing information on bull trout. In the 1990s the literature continues to grow at an accelerating rate, and conferences on bull trout have become commonplace events (e.g., the Gearhart Mountain Workshop, 1992; the Calgary Bull Trout Conference, 1994). Unfortunately, much of the recent bull trout literature is in the so called grey literature. This grey literature consists of consultants reports, government reports, and unpublished theses. It often contains original and useful information, but accessing the grey literature is a vexing problem. Usually these reports are only cursorily reviewed and have limited distributions: they are rarely deposited in major libraries, and almost never appear in standard abstracts. Consequently, there is no efficient way to find this material and, as a result, it is often over-looked. Unfortunately, in British Columbia, and in the surrounding provinces and states, most of the recent information on bull trout life-history, ecology and management is buried in this grey literature. 3.0 BIOLOGY OF RELEVANT LIFE HISTORY STAGES 3.1 Spawning Areas and habitat characteristics As far as is known, all bull trout populations spawn in flowing water (Heimer 1965; McPhail and Murray 1979; Oliver 1979; Leggett 1980; Goetz 1989; Pratt 1992). Apparently, bull trout avoid large rivers (e.g., the mainstem Fraser, Columbia, Peace or Liard rivers) for spawning, and instead prefer spawning sites in smaller, lower order rivers; however, this avoidance of large rivers may be more app
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