Atlantic salmon (Salmo salar) COSEWIC assessment and status report: chapter 7
Designatable Unit 1 – Nunavik (Quebec fishing area designation - Q11; CU 1)
This DU extends from the tip of Labrador (approximately 60°29’ N, 64°40’ W) west along Ungava Bay to the western extent of the species’ range, and represents the most northerly known populations of Atlantic Salmon in North America. Atlantic Salmon in this unit are geographically disjunct from southern populations with a substantial distance between these populations and those along the Labrador coast (~650 km; limited survey work and Aboriginal traditional knowledge suggest there are no self-sustaining populations between DU 1 and DU 2). Some portions of the Ungava populations also appear to have local migratory patterns (Power 1969, Robitaille et al. 1986), while others range broadly (Power et al. 1987). Genetic data suggest that these populations are distinct from their nearest neighbours and there is little genetic evidence of straying between Ungava and other regions (Fontaine et al. 1997, Dionne et al. 2008). There have been no known stocking events in this DU.
Designatable Unit 2 – Labrador (Salmon Fishing Areas – 1, 2, 14a, and 5 rivers of Quebec fishing area – Q9; CUs 2, 3 and part of 26)
This DU extends from the northern tip of Labrador (approximately 60°29’ N, 64°40’ W) south along the coast of Labrador to the Napitipi River in Quebec. Given the large size of this geographic region there is substantial potential for smaller regional groupings within the DU, particularly in the Lake Melville area. However, the available information only supports a clear separation from other regions at the southern portion of the DU. Within DU 2, genetic data suggest reasonable potential for gene flow and hence re-colonization throughout much of the southern portion of the unit (King et al. 2001, Verspoor 2005, Adams 2007 (FST = 0.017), Dionne et al. 2008). There is evidence from tagging studies, however, that salmon from the southern portion of this unit do not migrate north of Lake Melville (Anderson 1985, Reddin and Lear 1990). Within-unit comparisons showed weak differentiation between northern and southern rivers where pair-wise heterogeneity was calculated (King et al. 2001). Verspoor (2005) did not detect a pattern of differentiation between northern and southern Labrador samples. However, the only sample from Lake Melville (Cape Caribou) was significantly different from the other Labrador samples and suggests the potential for a separate DU at Lake Melville. Unfortunately the Cape Caribou sample was comprised only of a small sample of parr and thus other supporting information is required to justify the creation of a separate DU for Lake Melville. The DU 2 populations did show significant divergence from other nearby DUs including DU 7 (Eastern North Shore) (Dionne et al. 2008) and the insular Newfoundland DUs (FST = 0.021; Adams 2007).
The salmon in DU 2 also appear to have variable life histories with no clear pattern across the DU (Chaput et al. 2006a). They show significant life history divergence from the nearby DUs of insular Newfoundland and the eastern North Shore of Quebec (Chaput et al. 2006a) (MSW versus grilse populations). There have been no known stocking events in this DU.
Designatable Unit 3 – Northeast Newfoundland (Salmon Fishing Areas 3-8; CU 4)
This DU extends from the northern tip of Newfoundland (approximately 51°37’ N, 55°25’ W) south and east along the northeast coast of the Island to the southeast tip of the Avalon Peninsula (approximately 46°38’ N, 53°10’ W). The salmon of the northeast coast of Newfoundland are unique in North America, in that they appear to have genetic profiles intermediate to European and North American salmon (King et al. 2000). Genetic data also suggest that there are distinct differences between salmon populations in DU 3 and salmon populations in both Labrador, and southern and western Newfoundland (Verspoor 2005, Adams 2007, Palstra et al. 2007). The salmon in DU 3 also exhibit life history variation distinct from other nearby DUs (Chaput et al. 2006). Mean age of smoltification was intermediate between Labrador and the rest of insular Newfoundland (3-5 years versus 5-7 in Labrador and 2-4 in southern Newfoundland DUs), and a high proportion of grilse were relatively small 1SW females. This portion of the Canadian range also has the highest incidence of repeat spawners. Juveniles in this DU make heavy use of lacustrine habitat for rearing (e.g., Hutchings 1986). The Exploits and Terra Nova Rivers were stocked extensively in the 1980s and 90s after new habitat was made accessible with fishways (Mullins et al. 2003).
Designatable Unit 4 – South Newfoundland (Salmon Fishing Areas 9-12; CUs 5, 6)
This DU extends from the southeast tip of the Avalon Peninsula, Mistaken Point (approximately 46°38’ N, 53°10’ W) westward along the south coast of Newfoundland to Cape Ray (approximately 47°37’ N, 59°19’ W). Unlike DU 3, freshwater habitat in DU 4 tends to have relatively low pH values (5.0-6.0). Genetic data suggest that populations along this coast have reduced gene flow among local rivers and between DU 4 and other regions of the Island (Palstra et al. 2007). Adams (2007) also demonstrated significant genetic differences between two rivers from DU 3 and two rivers found on the southern Avalon (southeastern DU 4) using a suite of 10 microsatellite markers. Like Palstra et al. (2007), Verspoor (2005) found significant genetic differentiation among south coast rivers, but there did not appear to be a geographic pattern to the divergence. The relatively high levels of population structure in DU 4, as evidenced by the substantially higher interregional FST values on the south coast of the Island reported by Palstra et al. (2007), suggest potential subdivision of this DU in the future.
Salmon in DU 4 also experience substantially different ocean conditions than fish in DUs 2-3, entering an area influenced by the Gulf Stream versus the Labrador Current. Population trends for south coast rivers also appear to be distinct from the other DUs in Newfoundland. Much like the genetic data, the life history data for the south coast are variable and show no clear geographic pattern (Chaput et al. 2006a). There is a mix of early and late runs, smolt age is variable and both the proportion of female grilse and migratory routes appear to vary along the coast. Rocky River was stocked after the construction of a fishway at the river mouth. Anadromous salmon were absent prior to the fishway construction.
Designatable Unit 5 – Southwest Newfoundland (Bay St. George region) (Salmon Fishing Area 13; CU 7)
This DU extends from Cape Ray (approximately 47°37’ N, 59°19’ W) northwards along the west coast of Newfoundland to approximately 49°24’ N, 58°15’ W. This particular DU is the only region of insular Newfoundland with significant numbers of MSW salmon (Dempson and Clarke 2001) and minimal lacustrine habitat. Genetic comparisons of populations in this region with those in the rest of the Island suggest the populations here represent a distinct group, but that within the region gene flow appears to be higher than in DUs 3 and 4 (lowest FST values reported by Palstra et al. (2007) and Verspoor (2005)). DU 5 also has the youngest mean smolt ages (3 years) on insular Newfoundland and the lowest proportion of female grilse. DU 5 is separated from mainland DUs by the Gulf of St. Lawrence, and genetic data suggest low levels of gene flow between insular populations and the mainland (Verspoor 2005). Hughes Brook and Corner Brook stream have both been stocked in this DU.
Designatable Unit 6 – Northwest Newfoundland (Salmon Fishing Area 14a; CU 8)
This DU extends northward along the west coast of Newfoundland, from approximately 49°24’ N, 58°15’ W to the tip of the Great Northern Peninsula (approximately 51°37’ N, 55°25’ W). Smolts from populations of DU 6 most likely migrate northward through the Strait of Belle Isle (B. Dempson, Dept. of Fisheries and Oceans, Pers. Comm.) and they have life histories that are mixed and intermediate between DU 2 and DU 5 (Chaput et al. 2006a). Freshwater habitat in DU 6 is significantly more alkaline than the rest of insular Newfoundland, due to a large amount of limestone in the region’s geology. Unfortunately, genetic data for this DU are sparse. Several rivers in this DU such as the Big East, St. Genevieve and River of Ponds have a MSW component. From 1972-1976, DFO annually transferred 50-300 adult salmon from Western Arm Brook into a good spawning habitat upstream from the fishway in the Torrent River.
Designatable Unit 7 – Quebec Eastern North Shore, (Quebec Fishing Area – 9, western portion; most of CU 26)
This DU extends from the Napitipi River (not inclusive) westward along the north shore of the St. Lawrence to the Kegaska River (inclusive) in the west. Dionne et al. (2008) used microsatellite markers, temperature, difficulty of river ascension, and 1SW percentage to differentiate among regions of the North Shore. DU 7 is characterized by populations with high proportions of 1SW salmon and rivers with lower temperature regimes than DU 8. The genetic data also suggest these populations have lower levels of gene flow within the DU than within other areas of the North Shore (Dionne et al. 2008) (mean FST = 0.037 versus 0.027 in DU 8). There are no known stocking events in this DU.
Designatable Unit 8 – Quebec Western North Shore (Quebec Fishing Areas – 7 and 8; CUs 24, 25)
This DU extends eastward from the Natashquan River (inclusive) along the Quebec North Shore to the Escoumins River in the west (inclusive). Dionne et al. (2008) provided microsatellite, habitat and life history data that segregate this region of the North Shore from DUs 7 and 10. The eastern edge of the DU appears to be a transitional area to DU 7 (Dionne et al. 2008) and does not have a clear geographic feature as a boundary. The western edge of the DU transitions into DU 10 in a similar fashion. The salmon of DU 8 have the highest proportion of MSW salmon by a significant margin relative to the other populations in the North Shore DUs. Stocking in this DU was substantial and has occurred in multiple rivers (Fontaine et al. 1997; Dionne et al. 2008).
Designatable Unit 9 – Anticosti Island (Quebec Fishing Area 10; CU 27)
This DU encompasses Anticosti Island. DU 9’s freshwater habitat is lower gradient than DU 7’s. However, in terms of temperature, DU 9’s freshwater habitat is similar to DU 7’s (based on degree days: 945 versus 938) but is cooler than DU 8, 10, 11 or 12. Genetic data from Dionne et al. (2008) show divergence of DU 9 with neighbouring DUs. These data also suggest that gene flow within DU 9 is high with no significant differences among several rivers (FST = 0.002). Some stocking has occurred in this DU in the past, mainly in the Jupiter River. For example, one-year and two-year-old smolts, as well as fall fingerlings, were stocked in this river during 1993 to 1995 (Caron et al. 1996).
Designatable Unit 10 – Inner St. Lawrence (Quebec Fishing Area 4, 5 and 6; CUs 21, 22, 23, part of 20)
This DU extends west along the northern shore of the St. Lawrence from the Escoumins River (not included) into the lower St. Lawrence River and returns eastward along the southern shore of the St. Lawrence to the Ouelle River (included). DU 10 is characterized by a higher proportion of 1SW salmon than DU 8 and a lower mean age at smoltification. Freshwater habitat is also the warmest along the Quebec North Shore. The genetic data from Dionne et al. (2008) suggests limited gene flow between this DU and DUs 8 and 12. Stocking in this DU was substantial and has occurred in multiple rivers (Fontaine et al. 1997, Dionne et al. 2008).
Designatable Unit 11 – Lake Ontarioiii
Approximately 67 tributaries of Lake Ontario were known to support runs of Atlantic Salmon. Scales obtained from two adult museum specimens indicate an exclusively freshwater growth history, suggesting that at least some salmon populations that originally inhabited Lake Ontario were potamodromous (freshwater resident) (Blair 1938).
Some authors have suggested that prior to the construction of the R.H. Saunders Dam in 1958 in the St. Lawrence River, some Atlantic Salmon would have migrated a distance of 2,400 km to the Atlantic Ocean (summarized in Parsons 1973). However, since potamodromous individuals in Lake Ontario experienced improved growth in Lake Ontario, similar to that acquired in the marine environment for anadromous populations, it seems there would have been few ecological benefits for Lake Ontario salmon to undertake an extensive marine migration. Unfortunately, there are few data to support or oppose the existence of anadromy in at least some Lake Ontario populations. Nonetheless, Lake Ontario Atlantic Salmon differed notably from other DUs in Canada in that age of smoltification was the lowest in the Canadian range, there were spring and fall spawning runs, and if anadromy did occur, it would likely have required prolonged staging in freshwater. These facts, along with the general concurrence of biologists that at least many populations were potamodromous, suggest that Lake Ontario Atlantic Salmon population were likely reproductively isolated from other Atlantic Salmon populations in North America.
Designatable Unit 12 – Gaspé-Southern Gulf of St. Lawrence (Quebec Fishing Area 1, 2 and 3; Salmon Fishing Areas 15, 16, 17 and 18; CUs 9, 10, 11, 12, 18, 19, part of 20)
This DU extends from the Ouelle River (excluded) in the western Gaspé to the northern tip of Cape Breton (approximately 47°02’ N, 60°35’ W). Data from Dionne et al. (2008) suggest that the Gaspé and northeastern New Brunswick represent a regional grouping. The mean FST (0.011) between rivers was the second lowest among the seven regions identified, after DU 9. Dionne et al. (2008) did not include the southeastern Gulf of St. Lawrence in their analysis, but the authors of this report could find no evidence that the southeastern Gulf exhibited genetic or life history divergence from the western Gulf of St. Lawrence. There is some evidence from neutral genetic markers that rivers of western Cape Breton may be divergent from the western Gulf (P. O’Reilly, Dept. of Fisheries and Oceans, Pers. Comm.), but more data are needed. Verspoor (2005) also found relatively little evidence of divergence within this region. Thus, the southeastern Gulf rivers were included in the unit. Genetic data are not available for Atlantic salmon on Prince Edward Island. While salmon populations in small streams probably reflect the province’s original populations, those in larger PEI streams are heavily influenced by stocking from eastern New Brunswick. Size distributions and run-timing of adults returning to these streams are also broadly similar to those found elsewhere in the southeastern Gulf (Cairns et al. 2009). For these reasons, PEI salmon populations are placed within DU 12. As stated above, this region has an extensive history of stocking (Fontaine et al. 1997 Breau et al. 2009, Cairns et al. 2009, Cameron et al. 2009, Chaput et al. 2010). PEI both provided salmon eggs for other rivers in the Maritimes and received substantial numbers of eggs and juveniles from mainland rivers. For most of this DU, stocking events have been common for at least the past 100 years.
Designatable Unit 13 – Eastern Cape Breton (Salmon Fishing Area 19; CUs 13, 14)
This DU extends from the northern tip of Cape Breton Island (approximately 47°02’ N, 60°35’ W) to northeastern Nova Scotia (approximately 45°39’N, 61°25’ W). The populations in this DU appear to be genetically distinct from its southern neighbour, DU 14 (Nova Scotia Southern Upland) (Verspoor 2005). Within this DU there is substantial life history variation between Atlantic coast rivers and the Bras d’Or Lakes rivers. The Atlantic rivers, for example have higher proportions of 1SW fish. Substantial differences in freshwater habitat (e.g., stream gradient) and divergent demographic trends suggest that there is some structuring within the DU. However, sparse genetic data do not appear to support any clear geographic pattern (P. O’Reilly, Dept. of Fisheries and Oceans, Pers. Comm.). Stocking in this DU has occurred in some rivers since at least 1902 when the federal government opened the Margaree hatchery (DFO 1997), but for the most part has been discontinued for over a decade.
Designatable Unit 14 – Nova Scotia Southern Upland (Salmon Fishing Area 20-21; CU 15)
This DU extends from northeastern mainland Nova Scotia (approximately 45°39’N, 61°25’ W) southward and into the Bay of Fundy to Cape Split (approximately 45°20’ N, 64°30’ W). Both mtDNA and microsatellite data suggest that gene flow between DU 14 and the neighbouring DUs (13 and 15) is minimal (DFO and MRNF 2008). Many rivers in DU 14 have freshwater habitat with relatively low pH. They also have lower proportions of MSW fish than their northern neighbours. Southerly populations in DU 14 also have some of the youngest smolt ages reported in Canada (Chaput et al. 2006a). This DU also has an extensive history of stocking, including recent efforts to slow the decline of a few of the severely depressed populations in the DU (J. Gibson Pers. Comm.).
Designatable Unit 15 – Inner Bay of Fundy (portions of Salmon Fishing Areas 22 and 23; CU 16)
This DU extends from Cape Split (approximately 45°20’ N, 64°30’ W) around the Inner Bay of Fundy to a point just east of the Saint John River estuary (approximately 45°12’ N, 65°57’). This DU has strong genetic differentiation from nearby DUs and appears to exhibit unique migratory behaviour (within the Bay of Fundy/Gulf of Maine) (COSEWIC 2006b). Over 40 million salmon of differing ages have been stocked into rivers of this region since the turn of the 20th century. Early sources are unclear, but recent stocking has been done with inner Bay of Fundy progeny (Gibson et al. 2003). These recent stocking events, intended to maximize exposure of salmon to wild environments, are a part of a captive-rearing program thought to have prevented, at least temporarily, the extinction of salmon in this DU (Gibson et al. 2008).
Designatable Unit 16 – Outer Bay of Fundy (Portion of Salmon Fishing Area 23; CU 17)
This DU extends westwards from just east of the Saint John River estuary (approximately 45°12’ N, 65°57’) to the border with the United States of America. Genetic data suggest minimal gene flow between this DU and nearby DUs 14 and 15 (King et al. 2000, Verspoor et al. 2002 and Verspoor 2005). Within this DU the Serpentine River has a unique run of salmon that return late in the fall and spawn the following year (Saunders 1981). DU 16 also has a higher proportion of MSW salmon migrating to the North Atlantic than DU 15 (Amiro 2003). Termination of this DU at the border with the United States reflects the scope of this report. From a biological perspective, the U.S. populations may be included in the DU (relationship not examined in this case).
|DU||Adjacent DUs||Salmon/Quebec Fishing Areas||Genetic Variation||Phenotypic Variation||Geographic||Ecological/Habitat|
|1 - Nunavik||2||Q11||Limited gene flow with other DUs based on neutral markers
Verspoor (2005), Dionne et al. (2008), Fontaine et al. (1997).
|Evidence of local migratory routes.||Disjunct from the rest of the species distribution (~650 km of coastline).||At the northern extreme of the species’ range in Canada, Arctic-like conditions.|
|2 - Labrador||1,3,6,7||SFA 1,2, 14b and 6 rivers from Q9||Minimal evidence of sub-structuring in southern portion of DU, data deficient in northern portion. Some evidence Lake Melville may be distinct
King et al. (2001), Adams (2007), Dionne et al. (2008).
|Higher incidence of MSW fish. Smolt primarily age 4+ (Chaput et al. 2006a).||Separated from insular Newfoundland by the Strait of Belle Isle.||Arctic and subarctic conditions in much of the DU. Anadromous Arctic char and brook trout abundant in many watersheds.|
|3 - Northeast Newfoundland||2,4,6||SFA 3-8||‘European-type’ mtDNA genotypes present in this area, Low levels of gene flow with other DUs based on neutral genetic markers. Some evidence of within-DU sub-structure
King et al. 2000, Verspoor (2005), Adams (2007), Palstra et al. (2007).
|Primarily grilse populations. Smolt predominantly age 4 (Chaput et al. 2006a).
Highest incidence of repeat spawners in Canadian range. Substantial non-anadromous population components.
|All rivers flow directly into open Northeast Atlantic and the Grand Banks.||Relatively low natural pH 6.1-6.5. Low gradient rivers.|
|4 - South Newfoundland||3,5||SFA 9-12||Evidence of within-DU sub-structuring, but no geographic pattern. Low levels of gene flow with other DUs based on neutral markers
Verspoor (2005), Adams (2007), Palstra et al. (2007).
|Some rivers have early run timing, and median smolt age of 3 years (Chaput et al. 2006a). Substantial non-anadromous population components.||Rivers empty into a region influenced by the Gulf Stream versus the Labrador Current.||Relatively low pH water usually < 5.5. Some areas are high gradient systems. Milder climate relative to northern portions of insular Newfoundland.|
|5 - Southwest Newfoundland||4,6||SFA 13||Evidence of higher rates of gene flow within this DU than among adjacent DUs and within other DUs
Verspoor (2005), Palstra et al. (2007).
|Earliest ages of smoltification on the Island. Only DU on insular Newfoundland with a substantial MSW component (Chaput et al. 2006a).||Rivers empty in the Cabot Strait and Gulf of St. Lawrence. Close proximity to southern DUs (e.g., DU 13).||Many low gradient streams, limited lacustrine habitat.|
|6 - Northwest Newfoundland||2,5,7||SFA 14a||Data deficient.||Small MSW component (Chaput et al. 2006a).||Rivers flow into the Strait of Belle Isle.||Lacustrine habitat abundant.|
|7 - Quebec Eastern North Shore||2,6,8,9||Part of Q8 and Q9||Neutral markers suggest higher gene flow within this region than among adjacent DUs. Data suggest western border with DU 8 may be ambiguous.
Dionne et al. (2008).
|Characterized by populations with high proportions of 1SW salmon (Chaput et al. 2006a).||No clear geographic boundary with DU 8 or DU 2, but separated from other DUs by Gulf of St. Lawrence||Rivers with lower temperature regimes than DU 8|
|8 - Quebec Western North Shore||7,9,10||Part of Q7 and Q8||Neutral markers suggest within DU gene flow is higher than among adjacent DUs. Some evidence of transitional areas on borders.
Dionne et al. (2008)
|Highest proportion of MSW salmon by a significant margin relative to the other DUs of the North Shore (Chaput et al. 2006a).||No clear geographic boundary with DU 7 or DU 10, but separated from other DUs by Gulf of St. Lawrence.||Higher gradient rivers than nearby DUs (Dionne et al. 2008).|
|9 - Anticosti Island||7,8,10,12, 13||Q10||Neutral markers suggest gene flow within this DU may be variable. Low levels of distinction among some rivers, but clearly divergent from mainland
Dionne et al. (2008).
|Higher proportion of 1SW salmon than many nearby DUs (Chaput et al. 2006a).||Distinct island system in the Gulf of St. Lawrence.||Lower gradient rivers (Dionne et al. 2008).|
|10 - Inner St. Lawrence||8,11,12||Q4,5,6||Neutral markers suggest divergence from adjacent DUs
Dionne et al. (2008).
|Lower mean age at smoltification than nearby DUs (Chaput et al. 2006a).||NA||Freshwater habitat is also the warmest along the Quebec North Shore.|
|11- Lake Ontario||10||FMZ 20||Data deficient||Likely potamodromous with the possibility of some anadromous populations. Had the youngest smolt ages in Canadian range.||Inland lake system||Unknown|
|12 - Gaspé-Southern Gulf of St. Lawrence||9,10,13||Q1,2,3 and SFA 15,16,17,18||Data deficient, but some evidence of divergence at eastern (Dionne et al. 2008) and western edges (P. O'Reilly pers. comm.)||Variable life histories across the DU, but no clear geographic pattern (Chaput et al. 2006a).||Encompasses entire southern Gulf of St. Lawrence and PEI.||Variable across the DU. PEI is a distinct island system. Miramichi River is the dominant system.|
|13 - Eastern Cape Breton||12,14||SFA 19||Absence of mitochondrial haplotype observed in DU14
Verspoor et al. (2005).
|Variable life histories across the DU. Some evidence of western and eastern geographic pattern (Chaput et al. 2006a).||Island system. Many of the DU rivers flow into the open Atlantic Ocean. Large inland lake system.||Higher gradient rivers than nearby DUs.|
|14 - Nova Scotia Southern Upland||13,15||SFA 20, 21||Allozyme, mitochondrial, and microsatellite data suggest divergence among DUs 14,15,16. Verspoor (2005), Verspoor et al. (2005). O'Reilly, pers. com.||Lower proportions of MSW fish than their northern neighbours. Southerly populations in DU 14 also have some of the youngest smolt ages reported in Canada (Chaput et al. 2006a).||Rivers flow into Western North Atlantic Ocean||Many rivers in DU 14 have freshwater habitat with relatively low pH.|
|15 - Inner Bay of Fundy||14,16||Portions of SFA 22 and 23||Allozyme, mitochondrial, and microsatellite data suggest divergence among DUs 14,15,16. Verspoor (2005), Verspoor et al. (2005). O'Reilly, pers. com.||Unique migratory behaviour.||Confined to the inner Bay of Fundy.||Unique Bay of Fundy tidal system.|
|16 - Outer Bay of Fundy||15||Portion of SFA 23||Allozyme, mitochondrial, and microsatellite data suggest divergence among DUs 14,15,16 Verspoor (2005), Verspoor et al. (2005). O'Reilly, pers. com.||DU 16 has a higher proportion of MSW salmon migrating to the North Atlantic than DU 15 (Chaput et al. 2006a).
Several systems with unusual run timing.
iii Elements of this section have been copied, abstracted and/or synthesized from COSEWIC (2006a).
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