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Recovery Strategy for the Atlantic Whitefish (Coregonus huntsmani) in Canada (Final)

1. Background


1.1 Status

1.1.1 Canadian Status

COSEWIC Assessment Summary

Common name: Atlantic whitefish

Scientific name: Coregonus huntsmani

Status: Endangered

Occurrence: Nova Scotia.

Reason for Designation: This species, endemic to Nova Scotia, is found only in the Tusket1 and Petite Rivière watersheds. It continues to decline because of habitat loss and degradation caused by acidification, hydroelectric dams, introductions of exotic species, and incidental fishing.

Status History: Designated Endangered in April 1984. Status re-examined and confirmed in November 2000. Last assessment based on an updated status report.

1 subsequently considered extirpated from the Tusket River (Bradford et al. 2004a)

1.1.2 Global Status

In 1996 the Atlantic whitefish was globally assessed as Vulnerable by the World Conservation Union (IUCN). It is listed in the IUCN Red Book with the designation VU D2, which implies the species is not endangered but facing a high risk of extinction in the wild in the medium-term future3. The 1996 designation indicated that the population is very small and is characterized by an acute restriction in its area of occupancy.

1.2 Distribution

1.2.1 Global Range

The Atlantic whitefish is endemic to Nova Scotia, meaning that it is found nowhere else in the world. In Nova Scotia it was historically found only in the Tusket and Petite Rivière watersheds, and their adjacent estuaries and bays (Figure 1). This species was extirpated from the Tusket River system sometime after 1982 (Bradford et al. 2004a).

Figure 1. Map showing the historical Canadian watershed distribution of Atlantic whitefish.4
Figure 1. Map showing the historical Canadian watershed distribution of Atlantic whitefish.

Despite extensive commercial and recreational fisheries in fresh and coastal waters throughout Nova Scotia, as well as extensive province-wide fish surveys, Atlantic whitefish populations have not been reported outside these two watersheds. Isolated captures of specimens identified as Atlantic whitefish were reported at the mouth of the Sissiboo River in southwestern Nova Scotia in 1919 (Scott and Scott 1988), at Halls Harbour on the Minas Channel in 1958 (Edge and Gilhen 2001) and in the LaHave Estuary in 1995 and 1997 (Edge and Gilhen 2001). These specimens may have been members of the Tusket or Petite populations.

1.2.2 Tusket River Watershed

The Tusket River population of Atlantic whitefish appears to have been entirely anadromous. They have not been recorded in the watershed since 1982. The population is now considered to be extirpated (Bradford et al. 2004a).

Figure 2. Tusket-Annis rivers watershed and estuary.
Figure 2. Tusket-Annis rivers watershed and estuary.

Occurrences were recorded in the non-tidal lower portions of both the Tusket River and the Annis River, as well as in the estuary that these two rivers share. Individuals have also been reported in Yarmouth Harbour located several kilometers to the west of the Tusket River (Figure 2). There is no information concerning the distance ascended by Atlantic whitefish in either the Tusket or Annis rivers (Bradford et al. 2004a; Figure 2).

1.2.3 Petite Rivière Watershed

The Petite Rivière system supports a significant resident Atlantic whitefish population distributed among three lakes: Minamkeak, Milipsigate and Hebb (Edge and Gilhen 2001; Figure 3). The lakes, which collectively cover a surface area of barely more than 16.0 km², cannot be accessed from the sea since the dam at Hebbville (Figure 3) is a complete barrier to upstream fish passage. The first confirmed specimen of Atlantic whitefish was found at the outlet from Milipsigate Lake in 1923 (Piers 1927).

There is no documented record of an anadromous run of Atlantic whitefish on the Petite Rivière prior to or after the construction of the dams on the Petite system. Since the construction of the dams, there have been reported occurrences of Atlantic whitefish below the lakes in Fancy Lake, and in the tidal portions of the Petite Rivière (Figure 3). As resident populations were not found in any recent surveys of the lakes below the dams (Bradford et al. 2004a), it is presumed that these fish somehow passed or were swept over the Hebbville dam and moved from there into downstream areas. There is no evidence to document this movement over the dam, including when or at what age Atlantic whitefish might pass over it. Specimens, that are also likely strays from the lake-resident population (Bradford et al. 2004a), have been captured in the LaHave River estuary (Edge and Gilhen 2001) which lies to the east of the Petite Rivière (Figure 3).

The presence of Atlantic whitefish in Minamkeak Lake has particular significance in light of the 1903 diversion of this lake from the Medway River (Figure 3) to the Petite Rivière (Edge and Gilhen 2001). Recent surveys showed that Atlantic whitefish are not resident within the Medway River, including the sub-drainage into which Minamkeak once drained (Bradford et al. 2004a). Presence of Atlantic whitefish in Minamkeak Lake is likely a consequence of colonization from Milipsigate and Hebb lakes sometime after the diversion (Bradford et al. 2004a).

1.3 Legal Protection

Atlantic whitefish are listed under Schedule 1, Part 2 of the Species at Risk Act (SARA) and therefore, the SARA provisions against the killing, harming, harassing, capturing or taking of individuals (SARA Section 32), and the damage or destruction of residence (SARA Section 33) apply.

Figure 3. Petite Rivière watershed and Green Bay estuary.
Figure 3. Petite Rivière watershed and Green Bay estuary.

In addition to SARA, the Fisheries Act and its supporting regulations have direct and/or indirect application to Atlantic whitefish. The Fisheries Act protects fish and fish habitat, whilst its supporting regulations (the Fishery (General) Regulations (F(G)R's), the Maritime Provinces Fishery Regulations (MPFR's), the Atlantic Fishery Regulations, 1985 (AFR's), and the Aboriginal Communal Fishing Licences Regulations (ACFLR's)) provide the tools to protect, conserve and manage fisheries.

With respect to fisheries, three of the most important regulatory provisions are:

  • a) section 6 of the MPFR's which prohibits the retention or possession of Atlantic whitefish,
  • b) section 6 of the F(G)R's which provides for the issue of variation orders to close any fishing season set out in regulations, and;
  • c) section 22 of the F(G)R's which provides for the issue of licence conditions.

After discussions with stakeholders, DFO and the Province have agreed to implement additional management measures on the Petite Rivière to protect Atlantic whitefish, primarily from incidental capture. By variation order, all angling is now prohibited annually from April 1 to June 30 in the inland waters of Minamkeak, Milipsigate and Hebb lakes (Figure 3), including the thoroughfares joining them. Commencing in 2005, only unbaited lures and artificial flies (no bait) are permitted during the open angling season from July 1 to September 30. One commercial gaspereau gill net licence holder in the estuary of the Petite Rivière was required, by licence condition, to relocate his fishing gear.

With respect to the protection of fish and fish habitat, some important regulatory provisions of the Fisheries Act include:

  • a) section 20 - 22 which deal with requirements for fish passage and the construction of fish-ways;
  • b) section 32 which prohibits the destruction of fish by means other than fishing unless authorized by the Minister;
  • c) section 35(2) which prohibits the harmful alteration, disruption or destruction of fish habitat unless authorized by the Minister, and;
  • d) section 36(3) which prohibits the deposition of deleterious substances into waters frequented by fish.

These sections of the Fisheries Act are administered by DFO, with the exception of section 36 which is administered by Environment Canada.

The Atlantic whitefish and its habitat are also protected by provincial legislation including the 1998 Nova Scotia Endangered Species Act and the 1994-95 Nova Scotia Environment Act. Minamkeak, Milipsigate and Hebb lakes form the water supply for the town of Bridgewater, and as such they will receive environmental protection as a designated 'Protected Water Area' under the provincial Environment Act. This type of designation involves a combination of regulations and best management practices which are rolled-out through a 'Source Water Protection Plan' and will address all activities in the watershed that could impact water quality (e.g., forestry, agriculture, road construction, recreational use, mining, etc.). The only fishery known to or likely to capture Atlantic whitefish in these three lakes is the recreational angling fishery which has either been closed or significantly modified to eliminate the likelihood of harm.

1.4 General Biology and Description

1.4.1 Physical Description

The Atlantic whitefish is a member of the salmon and trout family (Salmonidae) (Scott and Scott 1988) and belongs to the whitefish subfamily Coregoninae. It appears salmon-like, with silvery sides, a silvery white underbelly, and a back that is dark bluish-black or dark green (Figure 4). There are no spots or upper body markings. It has a deeply forked caudal (tail) fin and an adipose fin (small, fleshy fin between dorsal and caudal fins, typical of salmonids).

Scott and Scott (1988) describe Atlantic whitefish as having between 91 and 100 scales along the lateral line, a terminal mouth (lower and upper jaws equal) and small but well developed teeth.

Figure 4. Schematic depicting an adult Atlantic whitefish.
Figure 4. Schematic depicting an adult Atlantic whitefish : location of Terminal mouth, Adipose fin and Forked tail.

While growth of the species in the wild has not been studied, anadromous specimens from the Tusket River are known to have been larger than the landlocked Petite Rivière individuals. Records suggest adults can reach 50 cm (20 in) in length and up to 3.63 kg (8 lb.) in weight (Edge and Gilhen 2001). However, anadromous adults typically average 38 cm (15 in) while the smaller landlocked individuals range 20 to 25 cm (8-10 in) (Bradford 2000).

1.4.2 Common and Scientific Name

The common name Atlantic whitefish was employed by Scott (1967) and Scott and Crossman (1973) in reference to its regular occurrence in salt water off Yarmouth County, Nova Scotia, and its upstream fall migration in the Tusket River (Scott 1987). Originally described as Coregonus canadensis by Scott (1967) the species name canadensis was found to be already in use. Hence the name Coregonus huntsmani was recommended by Scott in 1987 in honour of the late Dr. A.G. Huntsman, noted Canadian marine biologist, who was aware of the presence of an unusual whitefish in Nova Scotia waters at least as early as 1921 (Huntsman 1922). The species was also referred to in the past as Acadian whitefish, Sault whitefish, round whitefish, and common whitefish.

1.4.3 Distinguishing Traits

Atlantic whitefish can be recognized on the basis of their external appearance. The species can be distinguished from most other salmonids by its larger scales. Additional features are used to distinguish Atlantic whitefish from the lake whitefish, C. clupeaformis, which is a common species in Nova Scotian lakes. The number of lateral line scales differs (average of 93.8 in Atlantic whitefish versus an average of 76.6 in lake whitefish), as does the number of vertebrae (average of 65.3 in Atlantic whitefish versus 60.6 in lake whitefish), the mouth shape (near- terminal for Atlantic whitefish, sub-terminal for lake whitefish), and Atlantic whitefish have small teeth while lake whitefish do not (Edge et al. 1991; Hasselman 2003). Genetically, Atlantic whitefish differ from both lake whitefish and cisco (Bernatchez et al. 1991; Murray 2005).

The distinguishing external traits of the Atlantic whitefish are published annually in the Nova Scotia Angler's Handbook, along with a request for members of the public to contact authorities with suspected sightings of the species. Additionally, habitat stewardship initiatives within the Petite Rivière area have included production and distribution of a handbook and brochure which provides information on the Petite Rivière watershed and the endangered Atlantic whitefish.

1.4.4 Life History

Little is known about the life history of Atlantic whitefish and what is known relates primarily to adults.

Anadromous population

The Atlantic whitefish was anadromous (sea-going) in the Tusket River (Figure 2); and, despite the lack of recorded evidence, they likely occurred historically in Petite Rivière as well (Figure 3). Individuals on the Tusket were known to occur in the estuary and sea waters in the summer, migrate into freshwater in the early fall (around September), move upstream in October and November with spawning probably occurring in the late fall or winter, overwinter, and return to the sea in the spring (Edge and Gilhen 2001). Specimens captured in the Tusket River during October and November had well developed gonads but had not yet spawned while specimens collected in May and June had poorly developed gonads (Edge and Gilhen 2001). Neither specific locations nor characteristics of the spawning habitat of the anadromous Atlantic whitefish population that once existed in the Tusket watershed are known (Bradford et al. 2004a).

Atlantic whitefish specimens captured in the marine environment contained shrimp, amphipods, fish and marine worms (Edge 1987).

Lake resident population

Spawning of the landlocked population in the Petite Rivière lakes also probably occurs in early winter. Neither specific locations nor characteristics of the spawning habitat of the land-locked Atlantic whitefish are known. Fish occurring in Minamkeak, Milipsigate and Hebb lakes are genetically identical (Murray 2005). No eggs or larvae have been collected from the wild. A single juvenile was sampled from an aggregation of Atlantic whitefish of similar size on one occasion in June 2000 in Hebb Lake (Hasselman 2003). The paucity of information on these life stages precludes any understanding of age structure and mortality rates.

Adults feed on a wide variety of aquatic organisms. Stomach analyses of specimens from the landlocked Petite Rivière population indicated a diet that includes aquatic insects and small fish but not benthic organisms (Edge and Gilhen 2001).

As mentioned previously, it is possible that Atlantic whitefish are swept over the Hebbville dam since there is nothing to prevent their downstream passage. However, these fish that do pass over this dam, are not able to re-join the lake resident population since there is no upstream fish passage provided. Furthermore, while there have been records of Atlantic whitefish below the Hebbville dam, there is no evidence to indicate that these fish represent a viable population (Bradford et al. 2004a).

1.4.5 Habitat Requirements

Little is known of the habitat requirements of Atlantic whitefish. Spawning, nursery, and rearing ground locations and preferences are not known, and migration areas are not understood. In the Tusket population, adults were frequently caught in the estuary. Lake resident Atlantic whitefish appear to be more prevalent in warmer surface waters than are lake whitefish. Recent field and laboratory research indicates that the species can tolerate full sea water from an early stage of development (DFO unpublished data).

1.5 Population Size and Trends

While there is insufficient information available at this time to enable accurate quantitative estimates of the Atlantic whitefish populations' sizes and trends in the Tusket and Petite watersheds, the following general qualitative comments can be made.

1.5.1 Tusket River Population

Once abundant, the Tusket River population apparently declined rapidly in the 1940s and 1950s, likely a result of the combined effects of construction and operation of the Tusket hydro-electric facility, poaching, and river acidification (Gilhen 1977; Bradford et al. 2004a). The decline continued; by the 1970s it was a novelty for one specimen to be taken in a season by a gaspereau fisherman. The last confirmed specimen captured on the Tusket River was in 1964 (Edge et al. 1991; Bradford et al. 2004a). No individuals have been observed or captured in any of the years of fishway monitoring since 1995 (Bradford et al. 2004a). It is believed that this population no longer exists (Edge and Gilhen 2001; Bradford et al. 2004a).

On the adjacent Annis River, catch also decreased over time, to the point that by the late 1970s a combined catch of fewer than ten individuals per year in the gaspereau fishery was typical (Edge and Gilhen 2001). There are no reports of Atlantic whitefish being captured in the Annis River since 1982 (Edge and Gilhen 2001; Bradford et al. 2004a).

1.5.2 Petite Rivière Population

There are anecdotal reports of Atlantic whitefish in the Petite Rivière watershed as early as the 1870s (Edge and Gilhen 2001). The recent trend for the Petite Rivière lake resident population is uncertain as there is no population estimate for the lakes. There have been records of Atlantic whitefish occurring below the Hebbville dam since its construction; however, a research trapnet set in the estuary during autumn 1999 and spring 2000 failed to capture a single Atlantic whitefish (Bradford et al. 2004a). Therefore, the presence of a viable anadromous population of Atlantic whitefish below the Hebbville dam is unlikely, or it exists below the level of detection currently possible.

1.6 Threats and Limiting Factors

Modification of the Tusket River and Petite Rivière watersheds through human activities has altered their physical habitat, hydrography and water chemistry. Species abundance has also been affected by past over-harvesting. Past and present significant threats, limiting factors, and habitat alterations include (in no particular order) (Bradford et al. 2004b; DFO 2004b):

  • construction and operation of hydroelectric dams and water supply impoundments;
  • acidification of habitat resulting from acid rain;
  • land use practices, in particular agriculture and forestry;
  • Historical fishing activities, and;
  • introduction and spread of non-native fish species which may pose competitive or predation risks (e.g., smallmouth bass, chain pickerel).

While the threats faced by Atlantic whitefish in the two watersheds (Tusket and Petite) exhibit common traits, the significance of the threats varies between the two systems (DFO 2004b). In the Tusket, habitat alteration and inadequate fish passage due to hydroelectric dam construction and operation, acidification, chain pickerel and smallmouth bass predation, and over-harvesting are identified as the most significant threats. By contrast, the Petite Rivière is better buffered and thus less affected by acidification; however the construction and operation of water supply facilities and predation by smallmouth bass are identified as the most significant factors threatening the population.

These threats have been recently reviewed during a DFO Regional Advisory Process meeting to evaluate the level of mortality that would not jeopardize the survival or recovery of Atlantic whitefish and to identify the potential sources of human-induced harm. In support of this review, factors potentially resulting in mortality of Atlantic whitefish as a result of human activities were considered (Bradford et al. 2004b). The conclusions of this meeting are summarized in a Status Report (DFO 2004a) and in section 2.7 of this document. The scope for the harm assessment documented in the Status Report (DFO 2004a) was limited to the area of known occupancy (i.e., the three Petite Rivière lakes).

1.6.1 Hydroelectric Development and Water Supply Impoundment

The construction and operation of hydroelectric dams and water supply impoundments have transformed lake and riverine habitat to reservoir habitat; the resulting fluctuating water level regimes have altered the original habitat and the dams have either blocked or impeded fish passage. A chronology of hydroelectric generation on the Tusket and Petite rivers in relation to fish passage and habitat requirements can be found in Bradford et al. 2004b.

Atlantic whitefish migration in the Tusket River is thought to have been limited by the Tusket River dams and past seasonal closures of the fish ladders (Edge and Gilhen 2001). The fish ladders were closed annually in the fall interrupting or preventing the Atlantic whitefish fall spawning migration. The damming of the Tusket River at Tusket Falls (Figure 2) in 1929 interfered with the migratory movement of the Atlantic whitefish for many years. Although a fishway, originally constructed of timber, was built in 1930, and rebuilt in 1941 due to decay, the structure was considered unsatisfactory and a new fishway was constructed in 1949. Additional improvements and changes were made to the fishways at both the Main Diversion Dam (Lake Vaughn) and the Powerhouse Dam (Tusket Falls) in the 1960s and 70s to facilitate downstream passage for diadromous species (e.g., salmon and gaspereau), improve the overall efficiency of the fishways for fish migration, and reduce mortality associated with fish passing through the turbines. In the 1980s and 90s ongoing studies with DFO and other stakeholders on the Tusket River focused on manipulation of operation schedules and maintenance flows to coincide with migratory movements of fish. Changes were mostly associated with attempts to improve upstream and downstream passage for Atlantic salmon and gaspereau. Since 2003 the Powerhouse fish ladder operating period has been extended to the end of December to accommodate any possible remnant Atlantic whitefish spawning migrations. Monitoring devices were also installed in an attempt to confirm the presence or absence of Atlantic whitefish in the Tusket River system. No Atlantic whitefish have been observed migrating through this monitoring device (NSPI 2003), and the species is now considered extirpated from the Tusket River system. Were Atlantic whitefish re-established on the Tusket River, the existing fishway should be suitable providing operations accommodated its migration times.

In the Petite Rivière system, waterbodies have been impounded and diverted for various reasons since the late 1790s; those in the upper watershed now constitute the Town of Bridgewater water supply. The construction of a hydroelectric dam at the foot of Hebb Lake as early as 1901 effectively blocked any upstream migration of fishes beyond this point. Dams without fish ladders presently obstruct the Petite Rivière at the outlets of Minamkeak, Milipsigate and Hebb lakes (Figure 3). While it is not known if adult anadromous Atlantic whitefish migrated to these lakes to spawn prior to the existence of the dams, the Hebbville dam now eliminates any likelihood of upstream migration to the lakes, including any individuals attempting to rejoin the population after having fallen over the dam. Fish passage is also impeded at the former dam site at Conquerall Mills, around an existing dam at Crousetown; and, is impeded or blocked at the dams at Milipsigate and Minamkeak lakes (Figure 3). A brief description of each barrier to fish passage on the Petite Rivière is provided in Table 1 below.

Table 1: Descriptions of barriers to fish passage in the Petite Rivière (adapted from Conrad 2005).
CrousetownA 2.4 m high timber dam located at a former sawmill site. The dam includes a run-around type of fishway constructed from loose native stone that is considered to be inefficient for fish passage.
ConquerallThe dam at the former Conquerall Mills hydro site was partially dismantled, allowing a 9 m space between the remaining concrete abutments. The resulting short series of rapids constitutes a 1.2 m drop which may present a small in-stream barrier to Atlantic whitefish passage upstream.
HebbvilleThe Town of Bridgewater water supply storage dam at Hebb Lake consists of a concrete flow-control structure and a long rock and earth fill berm. This berm is several hundred meters long and ends at a large pond. The pond is supplied by steady seepage through the berm and is drained by way of a meandering outlet channel and 1.5 m diameter culvert, finally emptying into the main channel of the river about 60 m downstream of the main concrete flow control structure. Other than the spillway, no fish passage is provided at this dam.
MilipsigateA concrete dam structure operated by the Town of Bridgewater for flow regulation purposes. Other than the spillway, no fish passage is provided at this dam.
MinamkeakThe uppermost storage dam for the Town of Bridgewater and is used for flow regulation purposes. Other than the spillway, no fish passage is provided at this concrete dam structure.

1.6.2 Acidification

Acidification may be another limiting factor for Atlantic whitefish. The rivers most affected by acidification in Nova Scotia are in the Southern Upland Region, which include the Petite and Tusket, where a combination of hard-rock geology, inadequately buffered soils and prevailing weather patterns have resulted in severe acidification of the rivers and lakes. The Tusket is more affected by acid rain than the Petite. While research on the effect of low pH on various life stages of Atlantic whitefish is underway, the impacts may be comparable to those of other salmonids. Acid toxicity has been identified as a major factor in low wild salmon abundance in Southern Upland rivers (DFO 2000), for example. Data from Clair et al. (2004) indicate that the Petite Rivière as well as portions of the Tusket River possess sufficient buffering capacity for Atlantic whitefish survival (Bradford et al. 2004b).

1.6.3 Land Use Practices

Land use practices can contribute to aquatic habitat degradation. Sectors such as agriculture, residential development and forestry undertake land-based activities in the Petite and Tusket watersheds. While there are no studies linking these activities specifically to effects on Atlantic whitefish, it can be inferred that should common activities not be properly mitigated, they could result in effects to fish and fish habitat.

In the upper reaches of the Petite Rivière watershed, agricultural activities have introduced bacterial contaminants and silt into watercourses. The majority of farming in the area occurs in the upper reaches of the natural watershed boundary of the Petite Rivière lakes and accounts for 2.5% of the land in the natural watershed (Kendall and Llewellyn 2001). Although farming in the area is on the decline and lands formerly used for farming are growing over, common farming practices involve raising livestock in small numbers and using manure to fertilize hay fields (Kendall and Llewellyn 2001). No large scale pesticide or herbicide application is known to occur, however concerns were raised by Kendall and Llewellyn (2001) about the application of manure on fields near watercourses, and the practice of watering livestock directly in watercourses. Manure in waterways is a concern since it can increase bacterial counts and decrease pH levels; however, in the Petite Rivière watershed levels are not thought to pose significant detrimental effect on the water supply (Llewellyn et al. 2000).

With respect to forestry, Sayah (1999, cited by Llewellyn et al. 2000) noted overlaps between clear cut areas and waterbodies within the natural watershed boundary of the Petite Rivière drainage. Forestry activities including roads, skidding trails, and clear cuts can cause accelerated soil erosion and siltation that can lead to a reduction in the productivity of the aquatic ecosystem and affect the rate and quantity of water runoff. All these factors can be harmful to fish habitat and lethal to fish (Birtwell 1999). Clear cutting has not, however, been reported directly surrounding the three lakes where Atlantic whitefish are found (Kendall & Llewellyn 2001). Under the Nova Scotia Forest Act (1989), there are Wildlife Habitat and Watercourses Protection Regulations which specify various requirements to protect watercourses that fall within forested areas (e.g., leaving buffer zones around watercourses). It is not known whether Atlantic whitefish have any particular sensitivity that would not accommodate forestry activities when undertaken according to the provincial guidelines and regulations. Generally, there is no indication of non-compliance in current forestry practices around the three lakes where Atlantic whitefish are currently found.

1.6.4 Historical Fishing Activities

Past harvesting practices, including poaching and incidental captures, may have been a factor in the decline of Atlantic whitefish populations. Atlantic whitefish were reportedly fished in the Tusket system prior to the 1960s and in the Petite Rivière until recently. Captured primarily by gill and dip nets, and occasionally by angling, the fish were used for human consumption, reportedly supporting a minor sport fishery and yielding a good food fish of fine flavour. They may also have been utilized for other purposes including bait for lobster traps and fertilizer (Scott and Scott 1988 and P. Longue, DFO 2001 personal communication).

Atlantic whitefish were once very abundant in the Tusket and Annis Rivers. Prior to 1940, it was reportedly not uncommon to catch 200 in a net when fishing for gaspereau on the Tusket River (Bradford et al. 2004a). The accumulation of Atlantic whitefish in the upper pools of the Tusket hydro facility fish ladders facilitated poaching in the 1950s. (Gilhen 1977; Scott and Scott 1988). Similarly, on the Annis River, incidental catches of 50 to 100 individuals during the gaspereau fishery was common as late as 1970.

In the Petite Rivière system, a small angling fishery around Milipsigate and Hebb lakes may have existed as early as 1870s (Edge and Gilhen 2001). Atlantic whitefish were reported as occasional bycatch in the May-June gaspereau fishery in the Petite estuary. There have been no legal directed or bycatch fisheries for the species, since at least 1978. Section 6 of the Maritime Provinces Fishery Regulations which specifically prohibits the retention or possession of Atlantic whitefish came into effect in 1993.

1.6.5 Interactions with Non-native Fish Species

Non-indigenous fish predators threaten Atlantic whitefish. Smallmouth bass (Micropterus dolomieu) and chain pickerel (Esox niger) have been identified as possible threats to Atlantic whitefish (Edge and Gilhen 2001). Smallmouth bass has been introduced into both systems, and chain pickerel are found in the Tusket system. The introduction and increasing range of smallmouth bass in both watersheds is also of concern, in particular the presence of this species in Minamkeak Lake, one of the three upper lakes of the Petite watershed which collectively support the only significant remaining population of Atlantic whitefish. The relationship of these introduced species to Atlantic whitefish is not well understood, but may pose competitive and predation risks (Bradford et al. 2004b).

1.7 Critical Habitat

Critical habitat as defined under section 2 of SARA is the “habitat necessary for the survival or recovery of a listed wildlife species and that is identified as the species' critical habitat in the recovery strategy or in an action plan for the species”.

While the state of knowledge on habitat requirements of Atlantic whitefish is increasing as new scientific evidence becomes available, it is currently not possible to identify critical habitat for this species and thus critical habitat for Atlantic whitefish is not identified in this recovery strategy and will wait to be designated at a later stage in an action plan. As set out in SARA, if information is inadequate to identify critical habitat within the recovery strategy, a schedule of studies must be prepared. Such a schedule, when implemented, will yield new information to enable the species' critical habitat to be described.

Appendix II includes a list of research and monitoring activities that collectively, constitute a schedule of studies. This schedule of studies describes the activities that are needed to define the critical habitat for this species. Despite not being able to identify critical habitat for Atlantic whitefish at this time, the following description of the habitat fundamental to the survival of the species may be useful in a future description of its critical habitat.

Atlantic whitefish, known historically to occur in the Tusket and Petite rivers, no longer exist outside of the Petite Rivière drainage. Life-cycle closure is achieved by fish resident within Hebb, Milipsigate and Minamkeak lakes (Figure 3). Species survival, and ultimately recovery, is therefore wholly contingent on the continued viability of this population whose global area of occupancy is now confined to approximately 16km2 of semi-natural lake habitat. While there are no indications that current human activities pose a threat to the survival of Atlantic whitefish, or that habitat quality within the lakes is inadequate, there is no scope for a further decline in either the abundance or the distribution of this species and the habitat it occupies (DFO 2004a).

3 This assessment was based on IUCN criteria, which differs from the criteria used by COSEWIC; and inaccurately identifies the distribution of the species as being the Great Lakes region of North America.

4 All map images derived from the Nova Scotia Topographic Database (NSTDB) and used by permission of Service Nova Scotia. Maps intended for illustrative purposes only.