2010 NORTHEASTERN NATURALIST 17(2):313–324 Distribution and Abundance of Salmonids in Prince Edward Island Streams Daryl Guignion1, Todd Dupuis2, Kevin Teather1,*, and Rosanne MacFarlane3 Abstract - The freshwater sports fishery of Prince Edward Island (PEI) revolves largely around three salmonid species—Salvelinus fontinalis (Brook Trout), Salmo salar (Atlantic Salmon), and the nonnative Oncorhynchus mykiss (Rainbow Trout). However, little is known about their current distribution and relative abundance on the Island. Of particular concern is the status of Atlantic Salmon, whose populations have declined dramatically in other parts of the Maritimes and are listed as “may be at risk” on PEI. We systematically sampled 69 streams with suitable juvenile salmonid habitat (riffle with gravel/cobble substrate), to provide baseline data concerning the population status of these three species. Brook Trout were found in all 69 streams, with a median density of 78.3 fish per 100 m2. Atlantic Salmon were found in 23 sites, at a median density of 11.6 fish per 100 m2. Rainbow Trout were found in only 19 streams, but at slightly higher densities of 16.2 fish per 100 m2. Present day distribution and abundance of all three species on the Island have been influenced by habitat modification and degradation. Introduction The number of freshwater and diadromous fish species that utilize watercourses on Prince Edward Island (PEI) is limited when compared with other Maritime Provinces (Curry 2007). Of particular interest for economic, recreational, and conservation reasons is the current status of three salmonid species. Salvelinus fontinalis (Mitchell) (Brook Trout) are apparently ubiquitous on the Island, found even in many of the smallest of streams. The small spring-fed streams of Prince Edward Island are excellent nursery areas for Salmo salar (L.) (Atlantic Salmon) (Saunders 1960). Old records indicate that this species was widespread, occurring in most of the major streams on the Island (Dunfield 1985). The decline in populations of this species around Prince Edward Island has long been recognized, although most detailed studies have been limited to the Morell River (Bielak et al. 1991, Cairns et al. 2000, Davidson and Bielak 1992, Ducharme 1977) and a few of the other major rivers (Cairns et al. 1995, 1996; Davidson and Angus 1994). Nearly all of these studies were based primarily on angler surveys. Oncorhynchus mykiss (Walbaum) (Rainbow 1Department of Biology, University of Prince Edward Island, Charlottetown, PE, Canada C1A 4 P3. 2Atlantic Salmon Federation, Department of Biology, University of Prince Edward Island, Charlottetown, PE, Canada C1A 4P3. 3Prince Edward Island Department of Energy, Environment and Forestry, Jones Building, 4th Floor, 11 Kent Street, PO Box 2000, Charlottetown, PE, Canada C1A 7N8. *Corresponding author - Kteather@upei.ca. 314 Northeastern Naturalist Vol. 17, No. 2 Trout) is a spring-spawning, non-native species on Prince Edward Island that has been intentionally released over the past 75 years. Some cagerearing sites have also become release points, as many trout have escaped from these fish-rearing facilities. Intentional, but illegal, releases have also occurred more recently, although it is difficult to substantiate these. Salmonid habitat on PEI is being negatively impacted in a variety of ways. Sedimentation due to poor land-use practices reduces survival of eggs and young fry (see Opperman et al. 2005). In addition, sediments often carry harmful agrichemicals that are known or suspected to have been responsible for at least 29 recorded fish kills in Island streams between 1966 and 2000 (Mutch et al. 2002). While the long-term effects of fish kills on salmonid populations are not known, short-term changes in community composition have been observed (Gormley et al. 2005a, Johnston and Cheverie 1980). Gormley et al. (2005a) suggested that the introduced Rainbow Trout is less sensitive to agricultural runoff than Brook Trout and that this tolerance, in part, could explain its success in Island streams. Stream blockages resulting from Castor canadensis Kuhl (Beaver) activity, faulty fishways, or poor water quality affect salmonids and other anadromous fish species (Collen and Gibson 2001). On Prince Edward Island, Beavers have been particularly influential in modifying stream habitat in the past 100 years. While it is unlikely that this species occurred here before the first European settlers arrived (Sobey 2002), there were several attempts to introduce them after 1900 (Cameron 1958). Currently, they are widely distributed on the Island and frequently prevent the movements of anadromous fishes (ASE Consultants, Inc. and UPEI Biology Department 1997). We believe, from the limited data available, that species distributions have changed in the past century, probably in response to poor agriculture practices, river damming, and intentional and unintentional releases of Rainbow Trout. If we are to effectively manage fish stocks, many of which are important economically, we must have a better understanding of their current status. Major declines in the populations of Atlantic Salmon have occurred in North America and Europe. Parrish et al. (1998) have suggested a number of factors that have likely contributed to this decline, including damming, dewatering of streams, pollution, overfishing, intensive aquaculture, and changing oceanic conditions. Little information is available on the population status of this species on Prince Edward Island, where it is listed by the Canadian Endangered Species Conservation Council as “may be at risk”. The objective of this project was to collect detailed information concerning the current distribution of Atlantic Salmon and Rainbow Trout as well as abundance estimates of all three salmonid species on PEI. While anecdotal records have provided some information concerning the abundance and distribution of salmonids across the island, no systematic sampling of all major watersheds has yet been carried out. 2010 D. Guignion, T. Dupuis, K. Teather, and R. MacFarlane 315 Methods Site selection The Recreational Fisheries Plan groups PEI watersheds into 20 clusters (ASE Consultants, Inc. and Island International Consultants, Inc.1992; Fig. 1). All 2nd to 3rd order streams considered to have habitat for salmonids were identified for the study; only Area C (Fig. 1) did not contain a potential salmonid stream. Sampling sites were chosen that had the most suitable habitat for juvenile Atlantic Salmon and Rainbow Trout (riffles with gravelcobble- boulder substrate). There were deeper pools in each of the sampling sites that provided habitat for Brook Trout. One site was chosen within one-half kilometer of head of tide, and an additional one or more sites were selected further upstream, if possible. On many of the smaller rivers, only one site was sampled. Electrofishing was done when the water temperature was below 19 °C, the water was not turbid, and flows were not unusually high. Some streams selected were not surveyed either because Beaver dams made it impossible to find more than a few meters of free-flowing stream or gradients were low and streamside vegetation too dense to find suitable gravel-cobble substrate. The four largest rivers (Dunk, West, Valleyfield, and Murray) were not electrofished because our barrier nets were inadequate for the stream width. Population assessment In the summer of 2000, sampling involved electrofishing approximately 100 m2 of stream using only an upstream barrier net. Sampling in 2001 Figure 1. Watershed complexes of Prince Edward Island. Names of individual watersheds sampled in each complex is provided in Table 1. 316 Northeastern Naturalist Vol. 17, No. 2 involved placing barrier nets at each end of the site. The measured area of the stream sampled ranged from 90 to 350 m2. Electrofishing at each site was conducted using a generator- or battery-powered Smith-Root electrofisher. Three consecutive sampling runs were performed, with the fish captured during each run placed into separate 40–50 L tubs. The population of each species in a site was estimated using the program POPDN3, version 1.3 (1985). This program provides the population estimate (per 100 m2) using the maximum likelihood method with the standard error and 90% confidence limits. Fish were immobilized with either ENO® (536 mg sodium citrate/g) or clove oil (1.25 x 10-2 ppt), identified to species, measured (fork length) to the nearest mm, and weighed to the nearest 0.1 g. After processing, fish were placed in a bucket of clean stream water and released when fully recovered. Median densities were calculated for all age classes combined. Results We were able to obtain density estimates for 65 streams across the Island, in 19 of the 20 clusters (Table 1). Brook Trout were present in all streams (Fig. 2a), with densities ranging from fewer than 1 per 100 m2 (Midgell and Naufrage rivers) to more than 400 per 100 m2 (Huntley River). Rainbow Trout were found in 19 of the streams (Fig. 2b), with densities ranging from 3.4 per 100 m2 (Clyde River) to 92.7 per 100 m2 (Tryon River). Atlantic Salmon were captured in 23 rivers (Fig 2c), with densities of less than 1 per 100 m2 (Wilmot, Bradshaw, and Black rivers and Bells Creek) to more than 160 per 100 m2 (Mill River). In streams where all three salmonid species were captured, Brook Trout had the highest median densities (78.4 per 100 m2), Table 1. Density and distribution of three salmonid species in Prince Edward Island rivers grouped by watershed cluster (WC; Fig. 1). Standard deviations are provided when more than one sample was collected from that stream. Brook Rainbow Atlantic WC Stream n Trout Trout Salmon Total A Huntley River 1 416.5 0.0 0.0 416.5 Montrose River 1 59.0 0.0 0.0 59.0 Tignish River 1 108.5 0.0 0.0 108.5 Miminigash River 1 22.1 0.0 0.0 22.1 L. Miminigash River 2 64.7 ± 42.6 0.0 0.0 64.7 Black Pond Bk 1 76.6 0.0 0.0 76.6 B B. Pierre Jacques River 1 40.0 0.0 0.0 40.0 Brae River 1 176.8 0.0 0.0 176.8 L.Pierre Jacques River 1 56.8 0.0 0.0 56.8 MacWilliams River 1 42.9 0.0 0.0 42.9 D Dunk River 12 72.5 ± 40.2 21.7 ± 33.7 10.5 ± 24.9 104.7 Wilmot River 10 85.5 ± 34.0 10.8 ± 14.9 0.3 ± 1.0 96.6 Bradshaw River 6 101.5 ± 77.0 9.6 ± 23.5 0.2 ± 0.4 111.3 E DeSable River 2 84.0 ± 11.5 0.0 0.0 84.0 Tryon River 2 88.3 ± 36.3 92.7 ± 86.6 0.0 181.0 Westmoreland River 2 39.3 ± 37.1 11.6 ± 16.4 0.0 50.9 2010 D. Guignion, T. Dupuis, K. Teather, and R. MacFarlane 317 Table 1, continued. Brook Rainbow Atlantic WC Stream n Trout Trout Salmon Total F Clyde River 1 183.7 3.4 0.0 187.1 North River 2 100.8 ± 39.8 6.5 ± 9.2 0.0 107.3 West River 1 157.2 10.6 2.4 170.2 G Clarks Creek 1 12.9 17.5 0.0 30.4 Glenfinnan River 1 137.0 7.2 0.0 144.2 Hillsborough Riveriver 1 34.4 20.2 0.0 54.6 Pisquid River 2 97.5 ± 94.5 6.2 ± 8.8 4.7 ± 6.6 104.4 H Belle Riveriver 2 110.4 ± 9.5 0.0 0.0 110.4 Flat Riveriver 1 180.5 0.0 0.0 180.5 Orwell River 1 79.9 5.0 0.0 84.9 Pinette River 3 85.9 ± 32.5 0.0 0.0 85.9 Vernon River 1 98.1 4.3 0.0 102.4 I Fox River 1 175.2 0.0 0.0 175.2 Murray River 2 199.9 ± 76.4 0.0 0.0 199.9 South River 1 123.4 0.0 0.0 123.4 J Brudenell Riveriver 1 175.9 32.3 2.4 210.6 Cardigan Riveriver 1 70.8 42.9 22.2 135.9 Montague River 1 347.8 33.2 0.0 381.0 Sturgeon River 2 78.4 ± 27.1 0.0 0.0 78.4 Valleyfield River 1 24.5 23.5 0.0 48 K Boughton River 2 53.4 ± 18.8 0.0 0.0 53.4 Fortune River 1 29.3 0.0 0.0 29.3 L Bear Riveriver 1 47.7 0.0 0.0 47.7 Black Pond Creek 1 76.6 0.0 0.0 76.6 Cross River 3 38.2 ± 13.2 0.0 74.9 ± 87.4 113.1 Hay River 1 100.0 0.0 29.9 129.9 North Lake Creek 3 75.7 ± 84.6 0.0 13.5 ± 18.9 89.2 Priest Pond Creek 3 39.6 ± 41.5 0.0 10.0 ± 6.1 49.6 Souris River 2 106.5 ± 9.5 66.8 ± 75.7 0.0 173.3 M Cow Creek 3 35.6 ± 18.2 0.0 16.2 ± 20.9 47.8 Naufrage River 2 0.5 ± 0.7 0.0 19.9 ± 1.6 20.4 N Bristol Creek 1 80.6 0.0 0.0 80.6 Midgell River 1 0.9 0.0 19.4 20.3 Morell River 2 46.0 ± 51.1 0.0 49.6 ± 40.0 95.6 St. Peters River 1 5.6 0.0 169.8 175.4 O Winter River 2 80.5 ± 43.7 0.0 0.0 80.5 P Auld Creek 1 235.1 0.0 0.0 235.1 Bells Creek 2 102.7 ± 4.0 0.0 0.5 ± 0.7 103.2 Black River 2 35.7 ± 40.4 0.0 0.5 ± 0.7 36.2 Hunter River 1 168.1 0.0 0.0 168.1 Wheatley River 1 9.6 0.0 0.0 9.6 Q Trout River (New London) 1 144.7 0.0 0.0 144.7 R Indian River 1 21.0 0.0 0.0 21.0 S Ellerslie Brook 1 69.4 0.0 0.0 69.4 Little Trout River 1 56.7 0.0 15.9 72.6 Trout River (Tyne Valley) 1 49.2 0.0 21.3 70.5 T Cains Brook 2 69.5 ± 5.9 0.0 31.1 ± 41.2 100.6 Mill River 2 120.3 ± 38.8 0.0 163.8 ± 218.1 284.1 Trout River (Coleman) 1 98.7 0.0 31.1 129.8 318 Northeastern Naturalist Vol. 17, No. 2 Figure 2. Individual watersheds on Prince Edward Island in which (a) Brook Trout, (b) Atlantic Salmon, and (c) Rainbow Trout were captured. 2010 D. Guignion, T. Dupuis, K. Teather, and R. MacFarlane 319 followed by Atlantic Salmon (16.2 per 100 m2) and Rainbow Trout (11.6 per 100 m2). There were only seven streams in which all three species were found. The median density of all salmonids at each site (containing one, two, or all three species) was 95.6 per 100 m2. Alosa pseudoharengus (Wilson) (Gaspereau), Morone americana (Gmelin) (White Perch), Gasterosteus aculeatus (L.) (Threespine Stickleback), Apeltes quadracus (Mitchell) (Fourspine Stickleback), Pungitius pungitius (L.) (Ninespine Stickleback), Notemigonus crysoleucas (Mitchell) (Golden Shiners), Phoxinus eos (Cope) (Northern Redbelly Dace), Fundulus diaphanous (Lesueur) (Banded Killifish), and Anguilla rostrata (Lesueur) (American Eels) were also encountered, but populations were not estimated. We report on populations of Cottus cognatus (Richardson) (Slimy Sculpins) elsewhere (Gormley et al. 2005b). Discussion Brook Trout are widely distributed in streams and rivers on Prince Edward Island. Streams on PEI have an abundance of springs or groundwater upwelling zones where Brook Trout spawn (Blanchfield and Ridgeway 2005). Such areas ensure that trout eggs are well oxygenated and that metabolic wastes are removed from developing embryos (Curry et al. 1995). Although Brook Trout are found in most streams on the Island, high water temperatures can render some areas inhospitable (ASE Consultants, Inc. and UPEI Biology Department 1997). When stream water temperatures increase, Brook Trout move towards springs and cold water seeps that serve as temporary refuges (MacMillan 1998, Power 1980). Even streams which have been seriously degraded or which have a history of fish kills often have reasonable populations, although we have observed an absence of trout in the upper reaches of streams that dry up in late summer or if fish kills occur in upper tributaries and re-colonization is inhibited because of physical obstructions. Our study was the first to carry out an Island-wide survey using a systematic sampling technique on Atlantic Salmon. As expected, populations of Atlantic Salmon were found to be absent or precariously low in many regions of Prince Edward Island. Low numbers or absence of salmon from many streams is probably attributable to a variety of factors including blockages, agrichemicals, sediments, and poaching. Streams with low gradients were particularly vulnerable to water quality problems and access difficulties after Beaver were re-introduced to PEI about half a century ago. Beaver impoundments seriously alter local habitats, and resulting increases in water temperatures and decreases in oxygen concentrations may be quite damaging to salmonids (Collen and Gibson 2001). The Fortune River was once well known for its salmon run; however, during the 1980s when more than 150 Beaver dams were removed, we found no evidence of salmon over three years of sampling. Other smaller streams such as the Marie and Bear rivers presumably lost salmon runs because of blockages. 320 Northeastern Naturalist Vol. 17, No. 2 Although Rainbow Trout have been released in a large number of streams across PEI, their distribution remains largely limited to two regions in the central and eastern parts of the Island. The reasons why they have become established in these areas are not clear, but may be related to higher gradient streams within the watersheds that may provide more suitable breeding habitat. We are currently examining the history of Rainbow Trout release on the Island as well as the stream conditions under which they have been successful to better understand the distribution of this non-native species. The three salmonid species were found together in only seven of the 65 streams sampled (Table 1). Salmon and Brook Trout were found together in 23, Rainbow Trout and Brook Trout in 19, while Rainbow Trout and Atlantic Salmon occurred together in only seven. Species-specific differences in habitat preferences and breeding activity are important in regulating their coexistence in small Island streams. Stoneman and Jones (2000) noted that Rainbow Trout were found in riffle areas with large substrate, while small substrate and more cover favored Brook Trout in Ontario streams. Cunjak and Green (1982) found that where the two species occurred in the same stream, Brook Trout favored areas with slower water and more cover. Gibson (1966) suggested a number of habitat differences between Atlantic Salmon and Brook Trout, including: Atlantic Salmon were found primarily in riffles, while Brook Trout were found in pools; Atlantic Salmon tended to be more tolerant of high temperatures; and Brook Trout were found more often under overhanging cover. Further, food partitioning may facilitate the co-existence of these two species (Mookerji et al. 2004). In contrast, there is substantial niche overlap between early life-history stages of Rainbow Trout and Atlantic Salmon (Hearn and Kynyard 1986), and competition between these two species has been proposed as one of the reasons for the lack of colonization success of Atlantic Salmon in British Columbia streams (Volpe et al. 2001) as well as the difficulty in reintroducing Atlantic Salmon into Ontario streams (Johnson and Wedge 1999). Atlantic Salmon and Rainbow Trout have co-existed in certain rivers on Prince Edward Island for decades, but in nearly all rivers where juvenile Atlantic Salmon populations have remained high or even moderate (greater than 20 per 100 m2), there are no Rainbow Trout. The one exception is the Cardigan River, where it is likely that both Atlantic Salmon and Rainbow Trout occasionally escape to the river from a local fish hatchery. The main threats to all freshwater species are sedimentation, pesticide runoff, and blockage to fish passage. Silt running into streams, exacerbated by intensive agricultural activity, has long been recognized as having a major impact on fish populations on Prince Edward Island (see Smith 1958). Waters (1995) suggested that the increased turbidity and reduction of light transmission through the water accompanying sedimentation probably hinders feeding by fish. Sedimentation has a more direct effect on salmonid egg and fry survival (Argent and Flebbe 1999, Everest et al. 1987, Greig et al. 2005, Kondolf 2000, Levasseur et al. 2006, Reiser and White 1988). 2010 D. Guignion, T. Dupuis, K. Teather, and R. MacFarlane 321 Fish kills, due to pesticide runoff from agricultural areas, may have also influenced the relative numbers of the three salmonid species on PEI. The 29 recorded fish kills in Island streams between 1966 and 2000 usually occurred as a result of runoff from agricultural fields after heavy rainfall events (Mutch et al. 2002). Both Johnston and Cheverie (1980) and Gormley et al. (2005a) found that Rainbow Trout suffered lower mortality and populations recovered more rapidly than those of Brook Trout after such events. It is likely that Atlantic Salmon are also heavily impacted. Juvenile salmon would be in the stream tributaries during the period when fish kills are most likely to occur (August–September) and thus would be vulnerable to pesticide run-off events. Long-term impacts of such events have not been studied. Several Island streams are now, or have in the past, been completely blocked to anadromous fish movements. Many other streams have partial blockages, either because of poorly designed/maintained fishways or water quality (ASE Consultants, Inc. and UPEI Biology Department 1997). Some streams are also inundated with active and inactive Beaver dams, and flowing water is difficult to find. In many other watercourses, numerous Beaver dams have been removed, often after anadromous fish populations have been severely compromised. Streams that currently support small runs of Atlantic Salmon could have their populations of salmon extirpated by Beaver blockages unless a concerted effort is made to provide access for spawning fish and adequate nursery areas for juveniles. The distribution and population numbers of the three species of salmonids on Prince Edward Island have been modified greatly in the past few decades. Brook Trout remain ubiquitous across the Island and are absent in only very small streams or those that have been impeded by blockages. The distribution and subsequent spread of Rainbow Trout is no doubt related to widespread stocking and unintentional releases from aquaculture sites. However, why they were successful in some streams and not others is still under investigation. Populations of Atlantic Salmon have probably already been lost from most streams in which they originally occurred and are seriously threatened in many others. Although intentional stocking programs have supplemented Atlantic Salmon populations over the past four decades (Cairns et al. 1995, Ducharme 1977, Guignion and MacFarlane 1992), habitat alteration due to stream blockages and siltation continue to negatively impact numbers. Acknowledgments We thank Alison Conohan, Eddie Francis, Nick Gautreau, Karen Gormley, Carrie Jardine, and especially Dierdre Squires for their assistance in fish sampling. This project was made possible with funding from the Atlantic Salmon Federation, the PEI Department of Environment, and the University of Prince Edward Island. 322 Northeastern Naturalist Vol. 17, No. 2 Literature Cited Argent, D.G., and P.A. Flebbe. 1999. Fine-sediment effects on Brook Trout eggs in laboratory streams. Fisheries Research 39:253–262. ASE Consultants, Inc. and Island International Consultants, Inc. 1992. A recreational fisheries development plan for Prince Edward Island. 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