Recovery Strategy for the Striped Bass, St. Lawrence Estuary Population, in Canada [Proposed] 2011 : Background

Common Name: Striped Bass (Population of St. Lawrence Estuary)

Scientific Name: Morone saxatilis (Walbaum, 1792)

Date of Assessment: November 2004

COSEWIC Status: Extirpated in 2004.

Reason for Designation: The population from the St. Lawrence Estuary has disappeared as a consequence of illegal fishing, with the last record dating from 1968.

Canadian Occurrence: Quebec

Status History: Designated extirpated in November 2004. Assessment based on a new status report.

The striped bass (Morone saxatilis) is a spiny fish with an elongated, laterally compressed body and a triangular head (Figure 1). It has two separated dorsal fins, the first of which is spiny. The caudal fin is forked. The first three rays of the anal fin are spiny. The pelvic fins are thoracic. The cheeks and opercula are covered with scales. The striped bass has a dark olive-green to black back and a white belly. On the pale or silvery sides, there are seven or eight horizontal dark stripes following the scale rows. None of these stripes extends onto the head.

Figure 1. Striped bass (Morone saxatilis).
Source: Fédération québécoise des chasseurs et pêcheurs (FédéCP).

This fish is well adapted to estuaries and coastal waters. It travels along the coast in compact schools of same-size fish, feeding on invertebrates and fish (see Section 1.4 Needs of the Striped Bass). In the St. Lawrence, the striped bass can live up to twenty years and reach a total length of 90 cm (Vladykov 1953).

1.3.1.1. Global Range

The natural range of the striped bass (excluding areas where it was introduced by humans) extends along the Atlantic coast of North America, from the St. Lawrence River to the St. Johns River in northeast Florida. Native striped bass populations have also existed in the tributaries of the Gulf of Mexico, from the Suwannee River in northwestern Florida to Lake Pontchartrain in Louisiana (Lee et al. 1980; Bain and Bain 1982).

The species was introduced in the common estuary of the Sacramento and San Joaquin rivers, on the Pacific coast, in 1879 (Bonn et al. 1976), and gradually became established in other rivers along the west coast of the United States (Hart 1973; Lee et al. 1980; Setzler et al. 1980).

The striped bass can live in freshwater and, in certain cases, may even complete its life cycle there (Scruggs 1957). It has been introduced as a sports species in numerous lakes and reservoirs in the United States, Mexico, Ecuador, Russia, Latvia, France, Portugal, Turkey and South Africa (Lee et al. 1980; Setzler et al. 1980; Froese and Pauly 2007). In some of these locations, the populations reproduce naturally (Lee et al. 1980; Setzler et al. 1980; Froese and Pauly 2007). Elsewhere, the striped bass thrives well but cannot reproduce and on-going stocking programs are required to maintain population numbers (Lee et al. 1980).

1.3.1.2. Canadian Range

In Canada, five native striped bass populations have existed in three distinct sectors corresponding to the three designatable units recognized by the COSEWIC (Figure 2): the Bay of Fundy, the Southern Gulf and the St. Lawrence Estuary (Robitaille 2004). The populations in the St. John, Annapolis and Shubenacadie rivers belong to the Bay of Fundy group, feeding in that bay during the summer and possibly coming into contact there. These three populations also frequent waters which, during the summer, are home to striped bass migrating from American rivers.

Figure 2 . Location of the five rivers in eastern Canada that have supported striped bass populations.
The filled-in circles indicate extant populations and the open circles indicate rivers in which no spawning activity has been observed for 20 years or more. Inset, range of North American native populations.

There is only one known spawning population in the southern Gulf, that of the Miramichi River. Striped bass have been captured in several estuaries and along the coast between Percé and Margaree, on Cape Breton Island (Melvin 1991). However, these fish all seem to originate in the Miramichi River, where the only known striped bass spawning ground in the entire southern Gulf is found (Bradford et al. 1995; Robichaud-LeBlanc et al. 1996; Douglas et al. 2003). The southern Gulf population is believed to be isolated from both the Bay of Fundy populations and the migratory bass from American rivers. All recaptures of striped bass tagged in the southern Gulf were reported in this sector, except for one in Maryland (Hogans and Melvin 1984).

The third group also contains a single population, that of the St. Lawrence Estuary, which occupied a roughly 300 km stretch of the fluvial and estuarine¹ portion of the river. With respect to the striped bass population of the St. Lawrence Estuary, the distribution of recaptures in a mark-release program between 1944 and 1962 suggests that it was isolated from the other Canadian populations (Beaulieu 1962; Robitaille 2001). Of the 3,009 tagged specimens, 310 were recaptured, all within the sector between Lake Saint-Pierre and Kamouraska. It is mainly in this portion of the St. Lawrence that most of the striped bass captures were made by sports and commercial fishermen (Figure 3). Commercial captures were also regularly recorded in the St. Lawrence Estuary between 1920 and 1965, though none were recorded in the southern Gulf between 1935 and 1968 (Leblanc and Chaput 1991; Douglas et al. 2003). All available data seem to indicate that the St. Lawrence striped bass population is distinct from other Canadian populations.

Figure 3 . Range of the historic population of St. Lawrence Estuary striped bass.
The movement of three-year and older striped bass upstream seems to be linked to spawning activity. Shown are only the areas where striped bass were regularly captured each year before the start of the population decline in the 1950s which terminated in the disappearance of the population.

In 2002, following an action plan for the reintroduction of striped bass in the St. Lawrence (Comité aviseur sur la réintroduction du bar rayé 2001), a reintroduction program was developed in Quebec, which included fish breeding in Quebec hatcheries using striped bass captured in the Miramichi River in New Brunswick. Between 2002 and 2009, more than 6,300 striped bass measuring over 60 mm in length (ages² 0+ to 6+) and 6.5 million larvae, 2 to 4 mm long, were stocked in order to promote the recovery of the striped bass population of the St. Lawrence Estuary. The aim of the reintroduction program, which will stock up to 50,000 autumn fry (Comité aviseur sur la réintroduction du bar rayé 2001), is to establish a population capable of self-reproducing. Since being reintroduced, striped bass have been captured in the sector once occupied by the extirpated population, between Lake Saint-Pierre and Rivière-du-Loup (DFO 2010a, b; Pelletier et al. 2010).

The present recovery strategy is concerned with the striped bass population reintroduced in the St. Lawrence Estuary (known as the new population), intended to replace the one which disappeared in the late sixties (known as the historic population).

1.3.2.1. Global population trends

Within the natural range of the striped bass, the status of the different populations varies greatly. The species is globally listed as common, widespread and abundant, but at the national and subnational levels, status varies considerably (Table 1). Some eastern American coastal rivers contain abundant populations characterized by lengthy migrations between the Bay of Fundy and northern Florida. The abundance and omnipresence of these migrating fish seem to indicate a general global abundance of the species. However, several spawning populations disappeared during the 20th century, including, for example, most of those in the tributaries of the Gulf of Mexico.

Table 1.Status of the striped bass according to NatureServe (NatureServe 2009).

*The conservation status of a species or ecosystem is designated by a number from 1 to 5, preceded by a letter reflecting the appropriate geographic scale of the assessment: G: Global; N: National; and S: Subnational (i.e., state or province). The numbers have the following meaning: 1 = critically imperilled; 2 = imperilled; 3 = vulnerable; 4 = apparently secure; 5 = secure; X: presumed extinct or extirpated; H: possibly extinct or extirpated; N: non-breeding; NA: not applicable —a conservation status rank is not applicable because the species or ecosystem is not a suitable target for conservation activities; NR: unranked—national or subnational conservation status not yet assessed http://www.natureserve.org.

1.3.2.2. Canadian population trends

In 2004, in Canada, in the three rivers where spawning populations had previously existed (the St. John, Annapolis and St. Lawrence rivers), no sign of reproductive activity had been observed and no capture of striped bass of local origin had been confirmed in over twenty years (Robitaille 2004). However, since the reintroduction of striped bass in the St. Lawrence, signs of natural reproduction were observed in 2008 (Bourget et al. 2008; Pelletier 2009). The populations in the Shubenacadie River (Bay of Fundy population) and the Miramichi River (Southern Gulf of St. Lawrence population) still appear capable of producing new individuals (Robitaille 2004).

The striped bass is an anadromous fish typical of the estuaries and coastal waters of North America (Scott and Scott 1988). Spawning, incubation and early larval development occur in freshwater in the spring. The young subsequently move downstream to brackish water and then on to salt water where they feed and grow until they reach maturity, approximately 3 years for males and 4 or 5 years for females (Berlinsky et al. 1995; Douglas et al. 2003; Powles 2003). In Canada, striped bass reproduce during three or four weeks beginning around the end of May and early June, in fresh or slightly brackish water. The spawning ground of the striped bass of the St. Lawrence Estuary has never been located, but available data seems to indicate that it lies in Lake Saint-Pierre or just downstream from there in the adjacent section of the fluvial estuary (Montpetit 1897; Vladykov and Brousseau 1957; Beaulieu 1962; Cuerrier 1962; Magnin and Beaulieu 1967; Robitaille 2001).

Of the various habitats used by the striped bass during its life cycle, the most important for the maintenance of the population appears to be the spawning, incubation and rearing habitats (Albrecht 1964; Auld and Schubel 1978; Dudley and Black 1978; Kernehan et al. 1981; Jessop 1990, 1991; Melvin 1991; Van den Avyle and Maynard 1994). Egg survival to hatching is closely tied to the physicochemical properties of the incubation habitat, particularly temperature, dissolved oxygen and the presence of a moderate current (Cooper and Polgar 1981). The duration of incubation is a function of temperature. The highest hatching rates (87%) and larval survival rates in the first 24 hours (76%) are obtained at 18oC (Morgan et al. 1981). At that temperature, the eggs hatch approximately 48 hours after fertilization (Pearson 1938; Raney 1952). Egg survival rapidly declines when the water temperature exceeds 23oC and gradually declines as water temperature drops below 17oC, with almost no eggs surviving at temperatures below 12oC (Morgan and Rasin 1973; Rogers et al. 1977). Two other factors, sufficient dissolved oxygen and the presence of a current, may have a combined effect on egg survival. The eggs are generally heavier than water and, in the absence of current, sink to the bottom, where they are more exposed to anoxia, a lack of oxygen (Chittenden 1971; Rawstron et al. 1989). The presence of a moderate current creates low turbulence levels, which keep the eggs suspended in the water column during incubation.

The survival of the larvae, like the eggs, also depends on physical variables, including temperature and dissolved oxygen. However, an additional requirement, i.e., a sufficiently abundant food supply, comes into play upon resorption of the yolk sac and the onset of feeding (Chittenden 1971; Rawstron et al. 1989). This key period occurs approximately on the eighth day of existence of the larvae, when they measure 6 to 7 mm. In natural environments, the rate of survival of larvae that have exhausted their yolk reserves is directly related to the abundance of zooplankton in their environment (Kernehan et al. 1981; Martin et al. 1985). It has been shown that in Chesapeake Bay, where the eggs and larvae are transported from several rivers where striped bass are known to spawn, the density of individuals in the first stages of development varies according to distance from the point of maximum turbidity (North and Houde 2003). Environmental characteristics and vertical migration of larvae in the water column, depending on the tides, enables them to maintain their position in the estuary, in areas where there is an abundance of prey. A zone of maximum turbidity also exists in the St. Lawrence, between Île d'Orléans and Île aux Coudres. This zone contains high densities of zooplankton, including the copepod Eurytemora affinis, and is known as a rearing ground for rainbow smelt (Osmerus mordax) and other fish species (Sirois and Dodson 2000). The striped bass of the St. Lawrence may also spend the early stages of their development there. After 35 to 50 days in the transformational larval stage, the young reach a length of 20 mm and possess the typical shape of the striped bass which they will maintain into adulthood.

Immature and adult striped bass frequent coastal and estuarine habitats (Bain and Bain 1982). During their first two years, they feed primarily on invertebrates, but gradually become piscivorous, chasing schools of soft-rayed fish, particularly juvenile clupeids (Trent and Hasler 1966; Manooch 1973; Austin 1980; Gardinier and Hoff 1982; Dew 1988). In summer, the movement of striped bass appears to follow that of their preferred prey. Adult bass tolerate and withstand variations in salinity, temperature, pH or turbidity (Talbot 1966; Auld and Schubel 1978; Setzler et al. 1980). Canadian striped bass populations typically migrate upstream in the fall and overwinter in fresh and brackish waters to avoid the cold winter ocean waters. The confined presence of striped bass in these overwintering zones may increase the risks of mortality due to environmental accidents or poaching.

The striped bass has a life expectancy of up to 30 years (Secor 2000). The largest known specimen, captured in North Carolina in 1891, weighed 56.8 kg and measured 1.82 m (Raney 1952). The growing conditions in Canadian waters are such that the maximum size of striped bass is less than 1 m. This figure is an estimate because very few individuals survive long enough to reach their maximum size. The largest striped bass caught in the St. Lawrence Estuary measured 91.5 cm (total length) and weighed 10.9 kg. After an examination of its scales, its age was estimated at 19 years (Vladykov 1953).

Typical of estuarine environments, the striped bass is highly dependent on the quality of the habitats it frequents during its life cycle, particularly the fluvial environments where it spawns. An abundant striped bass population is an indicator that a river and its estuary are in good condition and that the harvest rate is adequate (Bain and Bain 1982).

The striped bass does not build a nest and does not care for its offspring. Females discharge a large quantity of eggs into the water column. A tiny proportion of these eggs survive into adulthood. During the first weeks of their existence, most of the larvae will be preyed upon by various aquatic organisms (e.g., insects, invertebrates, fish) (Smith and Kernehan 1981; McGovern and Olney 1988; Monteleone and Houde 1992; Andreasen 1995). The survival rate of striped bass increases, however, after their first summer (Goodyear 1985).

At the adult stage, the striped bass, together with other fish, birds and mammals, occupies a high trophic level within the estuarine and coastal communities of North America (Hartman and Brandt 1995a). The species is adapted to estuaries, where it is one of the most important piscivorous species and an important component of the biodiversity of the aquatic ecosystem. It is able to withstand rapid variations in temperature, turbidity and salinity in these environments (Bain and Bain 1982). It moves along the coast in compact, same-size schools in search of food, especially at night (Koo et Wilson 1972). Consequently, the reintroduction of striped bass in the St. Lawrence would contribute to the restoration of biodiversity in this ecosystem (Comité aviseur sur la réintroduction du bar rayé 2001).

In an estuary which opens onto both fresh and salt waters, striped bass may compete with other piscivorous species (Hartman and Brandt 1995a, b). This may be the case in the St. Lawrence. According to striped bass fishermen at the wharf in Lotbinière, yellow walleye (Sander vitreus) avoid waters in which striped bass hunt in groups (C. Mélançon, undated manuscript). According to active fishermen surveyed during the 1940s, 1950s and 1960s, yellow walleye and sauger (S. canadense) were present in the St. Lawrence Estuary but captures of these species were less frequent before the disappearance of the striped bass (Robitaille and Girard 2002). The increase in abundance of yellow walleye may be explained by the fact that this species, and possibly others, have partially occupied the ecological niche vacated by the striped bass. If this is the case, the return of the striped bass may lead to a physical displacement (periodical or permanent) of walleye to other habitats and a subsequent reallocation of resources.

The known limiting factors are of particular concern during the early stages of development when fish are sensitive and less mobile. The reproductive strategy of this species is based on a very high rate of fecundity which offsets the high mortality rate during the early developmental stages. The striped bass is a highly fecund fish. Upon reaching sexual maturity at about 4 or 5 years of age, females carry approximately 53,000 eggs, a number which will grow as the fish increases in size, reaching about one and a half million eggs in ten-year-old individuals (Paramore 1998).

The existence and integrity of adequate environments for spawning, incubation and larval development, providing satisfactory water flow, temperature and water quality, are essential for the survival of a striped bass population (Albrecht 1964; Dudley and Black 1978; Kernehan et al. 1981; Jessop 1990, 1991; Melvin 1991; Van den Avyle and Maynard 1994). Survival to the end of the larval stage seems to be a key factor in year-class strength (Cooper and Polgar 1981) and thus in adult abundance several years later (Goodyear 1985; Ulanowicz and Polgar 1980). In the structure of the adult population, year classes that were produced in years in which conditions were favourable for spawning often dominate (Polgar 1981; Cooper and Polgar 1981; Goodyear 1985).

The striped bass population of the St. Lawrence Estuary may be exposed to further limiting factors because it lives at the northern limit of the species` range (Robitaille 2004). The harsher climactic conditions which the northern populations of this species must confront may result in a variable mortality according to size (Hurst and Conover 1998). It is estimated that juveniles that reach at least 100 mm in length by the end of their first growing season have a better chance of surviving the prolonged fast of their first winter under the ice than do smaller individuals (Bernier 1996; Bradford and Chaput 1997).

Another limiting factor relative to the biology of the striped bass of the northern populations is the confinement of individuals during the winter. The concentration of a high proportion of spawners in a restricted area may aggravate the repercussions of an episode of accidental mortality or increase the vulnerability of the fish to poaching. Three-year and older striped bass of the historic population used to migrate to Lake Saint-Pierre in the fall, where they would winter. Many of these individuals were the size of spawners and, consequently, naturalists at that time believed that this congregation of fish was in preparation for spawning activity, though this activity was never directly observed (Montpetit 1897; Vladykov 1947; Vladykov and Brousseau 1957; Cuerrier 1962; Magnin and Beaulieu 1967). It is impossible to foresee whether the striped bass of the new population will gather in Lake Saint-Pierre and the surrounding waters. To date, most of the captures of large striped bass in the Upper Estuary during the cold season have been concentrated in the plume of discharged water from the Gentilly 2 nuclear generating station (see section 1.5 Threats). This facility may be somewhat attractive for the species and could affect the winter distribution of adult striped bass. Concentrations of adult striped bass have also been observed in the spring by sports fishermen in the basin of the Rivière du Sud in Montmagny (Pelletier et al. 2010; DFO 2010a, b).

Finally, striped bass must have access to abundant food resources during the summer, without which their condition may deteriorate and the incidence of disease increase (Overton et al. 2000). They can, however, migrate to other areas to satisfy their needs.

According to the COSEWIC status report (Robitaille 2004), Canadian striped bass populations may be threatened by overfishing, modifications to spawning habitat due to changes in water flow, and by pollution. In addition, as mentioned in the preceding section, they may be exposed to further limiting factors because they are at the northern limit of the species` range (Robitaille 2004).

The following evaluation of threats to the survival and recovery of the striped bass combines two main sources: observations of factors which seem to have had a negative effect on the historic population; and phenomena which are presently active in the estuary and which affect fish populations in that environment. At present, the analysis of these two sources and the assessment of the relative importance of the different threats are based on the practical experience and the judgement of the members of the Recovery Team. Over the next five years, new information on the recovering population and the consequences of any new incidents which may occur will be incorporated in the threats classification.

The Recovery Team has assessed each threat according to six parameters (Table 2):

Table 2. Classification of threats to the striped bass population of the St. Lawrence Estuary.

1.5.2.1. Threats to Habitat

Fish habitat is comprised of the spawning grounds and nursery, rearing, food supply and migration upon which the survival of the fish depends, directly or indirectly. It includes the physical, chemical and biological attributes of the environment which are essential in the life cycle of the fish. It identifies the freshwater, estuarine and marine environments which, directly or indirectly, support fish stocks which are or could be the object of commercial, subsistence and recreational fisheries. The Recovery Team has identified a number of threats which may have a negative effect on the habitat of the striped bass of the St. Lawrence.

Habitat Disturbance Due to Dredging: Data and observations indicate radical changes in the distribution of immature striped bass before the disappearance of the species, coinciding with dredging and maintenance operations in the Traverse du Nord, the section of the shipping lane adjacent to Île d'Orléans (Robitaille 2001; Robitaille and Girard 2002; G. Labrecque, extirpated population technicians/biologists, pers. comm. 1990). According to project workers and local residents who observed the work being done, the dredged material was deposited in the area immediately surrounding the channel and on the banks of the nearest islands (Robitaille and Girard 2002). In the 1950s, analysis of recaptures of tagged fish by biologists of the Marine Biology Laboratory of the Department of Marine Fisheries (Vladykov 1945; Beaulieu 1962) revealed a change in the distribution of immature individuals aged from 1 to 2 years, previously abundant along the southern section of Île d'Orléans. Beginning in 1957, recaptures of these fish were only recorded along the South Shore, between Saint-Vallier and Rivière-Ouelle (Robitaille 2001). Observations by fishermen at the time corroborate this change in distribution: according to them, striped bass very rapidly became scarce around Île d'Orléans, Île Madame and Île au Ruau. Striped bass could only be caught on the South Shore or around the Montmagny Islands (Robitaille and Girard 2002) (Figure 4).

Changes to the aquatic environment which may have resulted from dredging and the dumping of dredged materials were reported over an extensive area, from Île Madame to the downstream end of Île aux Oies (Robitaille and Girard 2002). In several locations, an accumulation of silt or sand was observed on the river bottom, gradually decreasing water depth (Figure 4). Some of the channels between the islands, used by smaller vessels during low tide (for example, the passage between Île Madame and Île Ruau) were no longer navigable after the widening of the Traverse du Nord (Robitaille and Girard 2002). Over the years, shoals, such as the banks at Île au Ruau, also began to appear at ebb tide (Robitaille and Girard 2002).

Figure 4 . Map of a section of the St. Lawrence Estuary where, according to local fishermen, the accumulation of sand may have reduced water depth between Île Madame and Île aux Grues (in pink).
Adapted from Robitaille and Girard (2002).

Maintenance work on the shipping lane is still required on an annual basis in order to remove the sand which accumulates there. Several locations within the striped bass range must be dredged, particularly in Lake Saint-Pierre, near Bécancour, and at the Traverse du Nord. However, dredging practices have changed in recent decades; dredged material is now deposited in designated areas, chosen according to their dispersion capacity. The maintenance of the shipping lane continues, nevertheless, to have an impact on aquatic wildlife. Studies have revealed the negative effects which the dumping of dredged material has on benthic fauna and on the feeding grounds of Atlantic sturgeon (Acipenser oxyrinchus) and lake sturgeon (A. fulvescens)(Hatin et al. 2007; Nellis et al. 2007; McQuinn and Nellis 2007). In the estuary, the shipping lane is the largest area which is regularly dredged. This activity may increase in the coming years with the increase in marine traffic, the presence of increasingly larger vessels and decreasing water levels due to climate change. In addition, a great number of sites (docks, marinas, access channels) also require periodical dredging.

Consequently, the Recovery Team believes that this threat warrants a high level of concern and that additional research is necessary on the effects that dredging has on the striped bass.

Disturbance and Destruction of Habitat: The loss and destruction of habitats (bank-hardening, construction of walls, roads and docks, flood-plain and swamp infilling) may significantly modify the habitat of aquatic species. Practices such as these are still common and may be detrimental to the recovery of the striped bass in the St. Lawrence Estuary, particularly in Anse Sainte-Anne at La Pocatière, identified as critical habitat.

In 2004, an inventory was conducted of several sites³ where juvenile striped bass had been captured before the disappearance of the species and this revealed that some of these sites had undergone major changes. The most remarkable seems to be the fishing zone in Saint-Grégoire de Montmorency, where striped bass of all sizes had once been caught (A. Michaud, extirpated population technician/biologist, pers. comm.1990). This area is just downstream of what was once the Maizerets Flats and the Bay of Beauport, an important wetland adjacent to Quebec City. Between 1945 and 2008, in the area between the Saint-Charles River and the Île d`Orléans bridge, an estimated 360 ha of aquatic and riparian habitat was lost due to backfilling for the port of Quebec City and the construction of a highway in the 1970s (Robitaille et al. 1988). A major portion of one location where striped bass were caught in abundance disappeared beneath the highway (Robitaille 2005) and one section of the wetland is now cut off from the river by an embankment and the flow of water, regulated by the tides, must pass through concrete culverts.

Not all the encroachment on the riparian environment is so extensive, but the Recovery Team deems that the cumulative loss of these important habitats for juvenile development may reduce the estuary`s carrying capacity for the reintroduced striped bass population and the entire aquatic community, warranting a high level of concern.

Discharge from the Gentilly 2 Nuclear Station (thermal attraction and decompression of gases): The Gentilly nuclear station (located near Trois-Rivières), which has been operating since 1983 on the south shore of the upper estuary, discharges hot water which attracts several fish species during the cold season. Reintroduced adult striped bass were regularly captured in this area between 2006 and 2009, during the fall, winter and spring (Hydro-Québec Production 2007; Alliance Environnement inc. 2008). In comparison, in 2009, no winter captures of the species were reported in the fishing zones around the power station, in places such as the dock in Bécancour, in Sainte-Angèle-de-Laval or in Lake Saint-Pierre and its archipelago, where the recreational fishery was monitored from January to March. It is impossible to determine with certainty whether the striped bass are spawning in the plume of warmer water and, consequently, whether the eggs and larvae are being transported to the colder neighbouring waters where they are exposed to a thermal shock (Donaldson et al. 2008). However, among the specimens captured in this area in March, females were present that required only a slight pressure on the abdomen to discharge their eggs. At this stage, females are ready to spawn and the eggs survive in the environment only briefly (DFO 2010a, b). The thermal attraction created by the discharged water from the power station may thus have important consequences if a high proportion of spawners from the reintroduced striped bass population frequent this area, though this is not yet confirmed by the available data (DFO 2010a, b).

Furthermore, the discharged water from the power station is saturated with gas, which produces symptoms of gas disease in some fish species (Mikaélian 1999; Lair 2006, 2007). In the subcutaneous tissue of channel catfish (Ictalurus punctatus), gas bubbles which lead to inflammation and possible infection have been observed (Lair 2006). It is impossible to gauge, from the available data, the significance and the scope of this phenomenon outside the channel of discharged water. Striped bass captured in this area have presented no signs of gas disease (Aecom Tecsult inc. 2009).

It is presently impossible to determine whether a significant percentage of adult striped bass frequents this area during the winter months, but it will be important to study how the striped bass use this area. Studies are presently under way. In light of the uncertainty as to a possible impact on the survival and recovery of the striped bass, the Recovery Team, as a precautionary measure, has judged the level of concern of this threat as moderate.

Contamination: Many industrial, municipal and agricultural contaminants from the entire St. Lawrence Basin and the Great Lakes reach the estuary. They are able to accumulate in the food chain and, through bio-amplification, reach high levels in the flesh of organisms at the top of the food chain, including striped bass. Some of the effects of these contaminants, either direct or synergetic, have been observed in aquatic organisms. Among the substances considered to be contaminants, the focus initially was on those that produce primary toxic effects (Korn and Earnest 1974; Hall 1991). However, it has since been shown that the introduction into aquatic environments of several families of synthetic compounds (e.g., antioxidants, detergents, organometallics, steroids, organochlorines, organo-nitrates) can cause hormonal disruptions in aquatic organisms, leading to such things as femininization and inhibition of gamete production (Aravindakshan et al. 2004).

Bioassays of mercury in the scales of specimens from the historic population revealed that the exposure of striped bass to this metal reached a peak in the mid-1940s, decreased during the following decade and then increased again during the 1960s (Desjardins et al. 2003, 2006). However, there exists no information to suggest that the level of mercury in the historic and the new populations could affect the viability of the species. As for the other contaminants likely to affect the striped bass, information is either incomplete or unavailable.

The Recovery Team is unable to assess the gravity of the threat which contaminants pose for the new population of striped bass but, as a precautionary measure, considers the level of concern to be moderate.

Obstacles to Migration: Obstacles to the free movement of striped bass may: 1) fragment the habitats used by the fish over the course of a year; and 2) isolate populations from one another. Before the disappearance of the species, 1+ year-old striped bass often traveled along the coast in schools searching for food during the summer (Beaulieu 1962; Robitaille 2001). In October, mature striped bass from the St. Lawrence began a migration towards the Upper Estuary and Lake Saint-Pierre, in preparation for spawning (Montpetit 1897; Vladykov 1947; Vladykov and Brousseau 1957; Magnin and Beaulieu 1967; Robitaille 2001). Construction projects or the introduction of obstacles along these routes may affect the migration of the new population. The effects that the obstacles may have can vary depending on the nature of the construction projects and their location relative to the migration route of the striped bass.

The Recovery Team considers the level of concern of this threat to be low because there presently exist no major obstacles to the movement of striped bass within their distribution range.

Eutrophication: Domestic sewage systems and the spread of manure and fertilizers on agricultural land contribute to the eutrophication of aquatic environments. This can disrupt local biological communities through the spread of stringy algae and of cyanobacteria, habitat degradation (e.g., the spawning grounds of rainbow smelt), the prevalence of tolerant species, incidences of anoxia, and other phenomena. Eutrophication may alter aquatic habitats in the tributaries which drain agricultural lands and in the alluvial fans where they empty into the river.

Besides the degradation of local habitat and an indirect effect stemming from a decrease in the abundance of certain prey species, according to the Recovery Team this factor does not appear to constitute a serious threat to the recovery of the striped bass in its entire distribution area. It has thus been given a low level of concern.

Climate Change: In the medium and long term, the St. Lawrence Estuary may undergo many changes brought on by climate warming: decreases in freshwater flows, a rise in sea level, advance of the saline front, lengthening of the growth season, changes in the biological community of the estuary, etc. An increase of 0.7 ºC in air temperature during the last century has been recorded (Environment Canada 2001, Lemmen and Warren 2004, Environment Canada 1999). According to the different climate forecast models for 2050, average air temperature during the summer may rise by 2 to 4 ºC in Quebec (Bourque and Simonet 2007). In the long term, these changes may affect the aquatic habitats in the estuary and, consequently, the striped bass.

The Recovery Team considers it unlikely that, based on inter-annual variations in weather conditions, there will be negative impacts on striped bass due to climate change. The level of concern for this threat is thus low. If necessary, the situation will be reviewed and considered in the future action plan.

1.5.2.2. Threats Due to the Harvesting of Individuals

The historic striped bass population was subjected to intense commercial and recreational fishing, and poaching, right up to the time of its disappearance (Caron 1877; Montpetit 1897; Beaulieu 1985; J. Brousseau, A. Michaud, G. Labrecque, extirpated population technicians/biologists, pers. comm. 1990; Robitaille and Girard 2002). At that time, the number of catches was not regulated and size limits, introduced near the end, were not generally respected (A. Michaud, extirpated population technician/biologist, pers. comm. 1990). The use of fixed fishing gear, extensive throughout the estuary, resulted in abundant captures of juveniles that would die at low tide (G. Labrecque, extirpated population technician/biologist, pers. comm. 1990). Mortality due to fishing, already high, increased after habitat modifications reduced the range of immature striped bass (Robitaille 2001).

Today, the management of fisheries resource exploitation is much more structured. In 2005, sports fishing for striped bass was prohibited in the St. Lawrence downstream of the Quebec City bridge and the prohibition was extended to cover all of Quebec in 2007. Furthermore, the directed commercial fishery of striped bass is no longer sanctioned. However, there is still a by-catch of striped bass by commercial and sports fishermen. Under the Quebec Fishery Regulations of the Fisheries Act, striped bass must be immediately released when caught, in the area where they are caught and with due precaution not to injure the fish if it is still alive.

In order to assess and monitor the impact of the fisheries, a network to monitor accidental captures of striped bass has been created. This network is composed mainly of commercial fishermen who have been issued a permit for the capture of wildlife for scientific, educational and wildlife management purposes (SEG) ⁴. They are authorized to keep striped bass that are accidentally captured, in order to give them to the biologists of the ministère des Ressources naturelles et de la Faune du Québec (MRNF) for analysis. Since 2009, any live striped bass over 20 cm long that are captured must be released. In addition to the information gathered by this network, there are observations of caught and released striped bass which sports fishermen report to the Centre de données sur le patrimoine naturel du Québec (CDPNQ⁵). In 2005, the Fédération québécoise des chasseurs et pêcheurs (FédéCP), in collaboration with the MRNF, conducted a widespread awareness campaign to inform commercial and sports fishermen about the reintroduction of striped bass, the mandatory catch and release regulation, and the importance of reporting captures to the CDPNQ. Between 2003 and 2009, 507 striped bass were brought to MRNF biologists for analysis and 163 observations were recorded. These data made it possible to compile the first biological status report on the reintroduced population (Pelletier 2009) and to better identify habitat use (Pelletier et al. 2010).

In 2009, the DFO conducted an analysis of the possible impact of accidental captures in the commercial and recreational fisheries on the survival and recovery of the striped bass population of the St. Lawrence Estuary (DFO 2009). The analysis concluded that: “overall, freshwater and marine environment fisheries as they are currently carried out, are not very likely to have an impact on survival and recovery of the striped bass population in the St. Lawrence Estuary”. The Recovery Team has thus determined that the level of concern for this threat is low in all three areas: commercial fishery, recreational fishery and poaching.

Accidental Captures in the Recreational Fishery: Sports fishermen in the estuary may accidentally catch striped bass but they are obliged to release them immediately. Analysis of the impact of the fisheries has concluded that the mandatory release of captured fish, together with the awareness campaign carried out, makes it unlikely that recreational fishing will harm the survival and recovery of the striped bass (DFO 2009).

Accidental Captures in the Commercial Fishery: The risk of accidental capture of striped bass in commercial fishing gear varies according to location and season. The greatest risk for the new population, as it was for the historic population, comes from fixed gear designed to trap American eels (Anguilla rostrata) in the Middle Estuary. Since being reintroduced, some striped bass have been caught in fixed nets set for American shad (Alosa sapidissima) and in fyke nets, but these captures are negligible according to the commercial fishery monitoring reports (DFO 2009).

The number of eel traps in the St. Lawrence Estuary has declined dramatically since the 1950s. Presently, most of them are set in the Middle Estuary in September. In 2009, the number of authorized traps in the river and in the estuary saw a 73% drop, from 190 to 51 traps (about 35 are set each year). There are now only 21 commercial eel fishermen operating within the distribution range of the striped bass between Saint-Romuald and Rimouski (one fisherman near Quebec City and 20 others between Île d'Orléans and the mouth of the Saguenay River on the North Shore and Rimouski on the South Shore). As mentioned in the analysis of the impact of accidental catches (DFO 2009: "the sector where juvenile striped bass were very vulnerable prior to their disappearance is no longer a sector where the fishing effort is significant".

Analysis of the impact of the fisheries has concluded that all the freshwater and marine commercial fisheries have no or almost no impact on the survival and recovery of the striped bass except for the fyke nets and eel traps whose impact was deemed low and moderate respectively (DFO 2009). Should an increase in by-catches present a problem, measures may be implemented to redress the situation (e.g., closure of selected fishing zones).

Poaching: This activity is much harder to evaluate because of the lack of reliable data. According to the available information, there is no indication of an illegal fishery specifically targeting striped bass since its reintroduction.

1.5.2.3. Biological Threats

Exotic Invasive Species: Several exotic species have established themselves in the St. Lawrence River and Estuary. Exotic species can alter ecosystems and their ecological functions and may represent a threat to the striped bass (e.g., competition for habitat and food resources, restructuring of the food chain, predation).

The introduction of non-native organisms seems to have begun in the 19th century and has accelerated dramatically during the last decades. It is estimated that at least 185 exotic species have colonized the Great Lakes Basin since 1980, 88 of which have moved into the St. Lawrence River (Ricciardi 2006; NCRAIS 2009; De Lafontaine, Environment Canada, pers. comm. 2009). Several fish species have been introduced including the tench (Tinca tinca) and the round goby (Neogobius melanostomus). The latter has rapidly become quite abundant in several sections of the St. Lawrence, including the area once used by the striped bass.

The impact of invasive species on the new striped bass population has not yet been determined and is not currently known. The Recovery Team consequently considers this threat as a low level of concern because no major impact on the striped bass population is foreseen.

Parasites and Pathogens: Necropsies performed on striped bass of the historic population revealed that several specimens had unidentified parasitic worms in their digestive tracts and abdominal cavities (J. Brousseau, laboratory notes). One of these worms may be the Philometra sp. (Séguin et al. 2007), a parasite which was also found in wild striped bass transferred from the Miramichi River to the St. Lawrence in 2005. In the southern Gulf of St. Lawrence, striped bass are often carriers of the Philometra sp. nematode and their general condition does not appear to be affected (S. Douglas, DFO, pers. comm. 2005).

The new population of striped bass will likely be host to a number of parasites, as are other fish species in the St. Lawrence, and may be exposed to certain pathogens, such as viral hemorrhagic septicemia (VHS) which is present in the Great Lakes Basin and in the Maritimes. VHS was first identified in 2005 and 2006 in the Great Lakes and is associated with mass mortalities in numerous fish species in the area. To date, no case of VHS has been detected in Quebec (C. Brisson-Bonenfant, MRNF, pers. comm. 2009). Several analyses were conducted prior to the implementation of the action plan for the reintroduction of striped bass from the Miramichi River. They showed that the risk of introducing new parasites or pathogens in the St. Lawrence was low (Robitaille 2000). After striped bass infected with VHS were discovered in the Miramichi River, captures of fish from that river ceased as part of the reintroduction program. Additional analyses at the hatchery confirmed that the individuals kept for reproduction in captivity were not carriers of VHS.

Parasites and pathogens do not presently appear to constitute a threat to the survival and recovery of the population, the Recovery Team considers this a low level of concern. It is however important to take the necessary precautions to ensure that the stocking of striped bass does not introduce new parasites and pathogens in the St. Lawrence.

The Comité aviseur sur la réintroduction du bar rayé (2001), composed of striped bass and fisheries specialists, released a statement supporting the introduction of this species in the St. Lawrence (Appendix 2). An agreement was signed between DFO - Gulf Region, and the MRNF to allow the sampling of up to 2,000 juvenile striped bass each year in the Miramichi River in New Brunswick. Representatives from the recreational and commercial fisheries and from aboriginal communities were then consulted to obtain their approval for the reintroduction project.

In 1999, and from 2002 to 2006, juvenile striped bass were captured in the Miramichi River and transported to the Baldwin-Coaticook hatchery in Quebec in order to develop and serve in artificial reproduction. The survival rate of the transferred striped bass in hatcheries proved to be greater than anticipated. Beginning in 2002, the St. Lawrence River was stocked with surplus fish from this program (Table 3), usually as part of a media event advertising the reintroduction of striped bass. As previously mentioned, between 2002 and 2009 more than 6,300 striped bass, over 60 mm long (age 0+ to 6+), and almost 6.5 million larvae, 2 to 4 mm long, were released into the St. Lawrence between Saint-Pierre-les-Becquets and Rivière-Ouelle. The stocking of striped bass produced in hatcheries began in 2006; these were initially surplus larvae that could not develop in hatchery environments because the necessary installations were not yet available. The Baldwin-Coaticook hatchery was renovated to permit the production of this species and, after a few years of trials and readjustments, is very close to success in producing fry, the preferred stage for stocking. The goal of the reintroduction program is to stock 50,000 autumn fry yearly with the objective of reaching a population capable of self-reproduction (Comité aviseur sur la réintroduction du bar rayé 2001). Methods of tagging larvae (chemical tagging), juveniles and adults (microchips) will provide the means to identify which of the striped bass captured in the St. Lawrence were stocked and which are of natural origin and to track abundance levels over time.

Table 3. Number of striped bass stocked in the St. Lawrence, by age group and length

In 2005, fishing of this species was prohibited downstream of the Quebec City bridge and the prohibition was extended to cover all of Quebec in 2007. In 2005, the FédéCP and the MRNF launched an awareness program informing sports fishermen how to identify the species and advising them to release all catches immediately and report captures to the Centre de données du patrimoine naturel du Québec (CDPNQ). Hundreds of notices were posted around docks, marinas and boat ramps, all along the river and the estuary.

In 2004, a network to monitor accidental catches of striped bass in commercial fishing gear was established, supplemented by observations reported to the CDPNQ (Bourget et al. 2008). Various biological and morphometric parameters of striped bass conserved at the MRNF are being analyzed in laboratories. The data gathered by this network have confirmed that the reintroduced striped bass are developing well in the St. Lawrence and are occupying a distribution range similar to that of the historic population. In 2008, this data helped show that natural spawning had occurred in the estuary because 38 striped bass individuals born that year (age 0+) were captured, and no stocking had occurred for this age group that year (Pelletier 2009). A report on the biology of the new striped bass population was produced (Pelletier 2009) and new information became available on habitat use (Pelletier et al. 2010). In addition, necropsies ensured regular monitoring of diseases and parasites (Guy Verreault, MRNF, pers. comm. 2010).

The results of analyses of the data and specimen collections of the extirpated population will also be used to facilitate the reintroduction of the striped bass. These data were used to document the biology and exploitation of the extirpated population (Robitaille 2001), the food sources of juveniles (Robitaille 2005), and the population`s exposure to mercury contamination (Desjardins et al. 2003, 2006).

When the striped bass population of the St. Lawrence Estuary disappeared at the end of the 1960s, it had been the object of scant research, focused primarily on its movements (Beaulieu 1962), its feeding habits (Brousseau 1955) and its development (Magnin and Beaulieu 1967). Further analyses were made possible through the additional collection of data and specimens (Robitaille 2001, 2005, 2010; Desjardins et al. 2003, 2006). It is not possible at the present time to determine to what extent the biological descriptors of the historic population may apply to the reintroduced population. Regular monitoring of the latter is first required.

Recovery activities are difficult to plan due to the lack of information on present day spawning grounds, the reproductive process, and the early stages of development. It will be necessary to locate the various habitats used during the different stages in the life cycle, particularly the habitats vital for spawning and larval development. This will make it possible to ensure the protection of these habitats and to accumulate measurements on abundance and survival during these critical stages. It will also enable the identification of the environmental parameters which influence the vitality of cohorts of the new striped bass population.

It is equally important to offer a description of the interspecific relationships of striped bass with other aquatic organisms, particularly prey, predator and competing fish species. A better understanding of this network of interactions will provide valuable indicators of the health of the striped bass population and of the species it interacts with. This will ensure that the recovery of the striped bass will not be achieved at the cost of other species endemic to the estuary. Finally, special attention should be paid to the threats listed above (see Section 1.5), particularly the ones of greatest concern, in order to formulate precise assessments of the risks they present and, if need be, to develop the appropriate mitigation measures.

¹The St. Lawrence Estuary extends from the outflow of Lake Saint-Pierre to a line between Pointe-des-Monts and Matane.

² Age is expressed in years.

³ In the St. Lawrence Estuary, specimens of juvenile striped bass captured in fixed gear between 1946 and 1962, from Neuville and Rivière Ouelle, were preserved (Robitaille 2005).

⁴ A special permit issued by the MRNF for the capture of animals for scientific, educational or wildlife management purposes (SEG permit).

⁵ http://www.cdpnq.gouv.qc.ca/index-en.htm