Recovery Strategy for the Striped Bass, St. Lawrence Estuary Population, Canada [Final] 2011: Critical Habitat

Critical habitat is defined in the Species at Risk Act (2002) subsection 2(1) as:“…the habitat that is necessary for the survival or recovery of a listed wildlife species and that is identified as the species` critical habitat in a recovery strategy or in an action plan for the species.” (subsection 2(1)).

SARA defines habitat for aquatic species at risk as: “… spawning grounds and nursery, rearing, food supply, migration and any other areas on which aquatic species depend directly or indirectly in order to carry out their life processes, or areas where aquatic species formerly occurred and have the potential to be reintroduced.” (subsection 2(1)).

For the striped bass, St. Lawrence population, critical habitat is identified to the extent possible, using the best available information. The critical habitat identified in this recovery strategy is necessary for the recovery of the species, but is insufficient to achieve the population and distribution objectives for the species due to inadequate information. In particular, the specific location of spawning, incubation and larval development habitats and the biophysical features that support their function, are unknown at this time. The schedule of studies outlines the studies required to refine the knowledge of these features and their attributes, and the overall critical habitat, that are necessary to support the population and distribution objectives for the species.

2.7.1.1. Information and methods used to identify critical habitat

The identification of critical habitat requires an understanding of the environmental needs of species during the different stages of its development, as well as of the quality and uses made of the habitat by the species throughout its range. It is also necessary to know the minimum number of individuals and the range required in order to ensure the maintenance of a viable and self-sufficient population. Information on the historic and reintroduced populations of striped bass in the St. Lawrence Estuary is incomplete and is based primarily on accidental captures in the recreational and commercial fisheries. This lack of information has constrained efforts to identify and characterize the habitats being used by the species. In addition, there is very little data available on the functions, features and attributes (i.e. chemical, physical and biological) of the habitats used.

The available data on habitat quality assessment and habitat use by the striped bass of the St. Lawrence Estuary were analyzed in two research documents, one by Pelletier et al. (2010) for the reintroduced population (data from 2002 to 2009) and one by Robitaille (2010) for the historic population. These documents were reviewed during a scientific peer review meeting in April 2010 (DFO 2010a, b). This analysis showed that since being reintroduced, the striped bass of the St. Lawrence Estuary has been using the same range as the historic population to complete all the stages of its life cycle. This range extends from Lake Saint-Pierre to Rivière-du-Loup. However, for the reintroduced population, there is no available information on the location of habitats used for spawning, incubation and larval development. For juveniles (age 0+), since being reintroduced, they have been captured in eel traps in September and October from La Pocatière to Kamouraska, and mostly in Anse Sainte-Anne (96% of captures). At this stage, it is clear that Anse Sainte-Anne is an important habitat for juveniles. Mature and immature do not appear to favour any one habitat but rather move about according to the movements and abundance of their prey. Concentrations of adult-size striped bass have been observed in spring in the basin of the Rivière du Sud in Montmagny and several individuals have been captured during the fall, winter and spring in the plume of warm water discharged by the Gentilly 2 nuclear station.

Data analysis of the historic and reintroduced striped bass populations has helped to identify important functions of the different habitats used at certain development stages (e.g., spawning, incubation and larval development habitat, wintering). However, the location of the habitats providing these functions, and the features that support them, will have to be determined by further studies before other critical habitat can be designated (MPO 2010a, b).

2.7.1.2. Identification of critical habitat: geophysical

Since the reintroduction of striped bass in the St. Lawrence Estuary, the established monitoring network in collaboration with eel fishermen has identified a zone of concentration of juveniles during the fall (from September 1 to October 31). Between 2005 and 2009, 193 juveniles were captured between La Pocatière and Kamouraska, 186 (96 %) of which were in Anse Sainte-Anne (Pelletier et al. 2010). Taking into account the restricted size of the population and the number of fish stocked, the capture of 186 juveniles in this area is quite significant.

Before the disappearance of the striped bass, the first yearly captures of juveniles in fixed fishing gear began in July in Neuville and moved steadily downstream in August to Rivière-Ouelle in September (Robitaille, 2010). Juvenile striped bass are now being captured once again in Rivière-Ouelle and during the same time period as before the species disappeared. In early July, the juveniles are not very mobile and may be obliged to feed on local prey. As summer advances, their swimming capabilities augment and they become more resistant to changes in temperature, turbidity and salinity (Robitaille 2010). They may then migrate towards salt water, as do the striped bass of the Miramichi River at the same developmental stage (Robichaud-Leblanc et al. 1996). This may explain why juveniles were captured in Rivière-Ouelle beginning only at the end of August when they were longer than 65 mm (Robitaille 2010). Because the number of eel traps has decreased considerably since the 1960s, it is not possible at this time to locate the habitats used by juveniles upstream of La Pocatière. The schedule of studies for the identification of critical habitat, along with the action plan, should help fill these knowledge gaps.

The general location of critical habitat is shown in Figure 5. Facing the municipalities of Saint-Roch-des-Aulnaies, La Pocatière and Rivière-Ouelle, an area bounded to the west by the old dock of Saint-Roch-des-Aulnaies (N 47˚18'56.4'' ; W 70˚10'18.1'') and following the high water line east to the dock at Rivière-Ouelle (N 47˚29'10.2'' ; W 70˚01'10.2''). From there, offshore of Rivière-Ouelle (N 47˚29'29.8'' ; W 70˚01'57.8''), then west along the 5 m isobath of the marine charts to offshore of Saint-Roch-des Aulnaies (N 47˚21'19.6'' ; W 70˚13'46.1''). The total area of critical habitat covers 146.3 km².

Figure 5 Delineation of critical habitat in the intertidal zone and 0 to 5 m depth zone of Anse Sainte-Anne in the St. Lawrence Estuary. Adapted from Pelletier et al. 2010.
Point 1: N 47˚18'56,4'' ; W 70˚10'18.1'' / Point 2: N 47˚29'10.2'' ; W 70˚01'10.2'' / Point 3: N 47˚29'29.8'' ; W 70˚01'57.8'' / Point 4: N 47˚21'19.6'' ; W 70˚13'46.1''.

Following the Science Advisory Report (DFO 2010a, b) and using the best available information, the St. Lawrence Estuary Striped Bass Recovery Team indicated that this area is important and of high quality for the species (especially for juveniles), and that this habitat is required to reach the species` recovery objectives. The schedule of studies to identify critical habitat (see Section 2.7.3) has been designed to enable the acquisition of information necessary to complete or re-evaluate this identification. Further information will serve to better understand the role of Anse Saint-Anne in the recovery of the striped bass of the St. Lawrence Estuary, revealing its unique functions, features and attributes and the range of the juveniles during summer and fall.

2.7.1.3. Identification of critical habitat: Biophysical Functions, features and their attributes

Anse Saint-Anne in La Pocatière is identified as critical habitat because it is a rearing area for juveniles during the fall (i.e. rearing function). The feature of this habitat, or its structural component, is the presence of a bay characterized by several specific and indispensable attributes required to maintain its function:

• availability of sufficient quantity and quality of prey species;
• thermal front area;
• high salinity gradient;
• unique circulation pattern that may contribute to increased local turbidity and greater concentration of preys;
• low tide depth from 0⁶ to 5 m.

Pelletier et al. (2010) presented the following description of the habitat in which juveniles were captured between La Pocatière and Kamouraska. This territory is an extensive intertidal zone characterized by extremely heterogeneous abiotic phenomena. The shoals and strong current circulation produce variations in the salinity gradient that can shift rapidly from 10 to 18%. The coastal area in this sector constitutes an ichthyoplanktonic retention zone of larvae composed primarily of rainbow smelt, Atlantic herring and capelin. The circulation of the water mass creates an important thermal front characterized by a temperature drop of 6 to 7 °C downstream of Rivière-Ouelle. The surface sediments are varied, changing from coarse to finer particles from east to west.

Once again, according to Pelletier et al. (2010), this habitat could be favourable to juvenile striped bass. According to the literature, juveniles are found in abundance in the sheltered bays of the estuaries where they feed primarily on small invertebrates during their first year (Robichaud-Leblanc et al. 1997). They will tolerate salinity levels up to 15% and temperatures between 12 and 23 °C (Bains and Bains 1982).

Anse Sainte-Anne may thus be a feeding ground for juvenile striped bass. The colder, saltier water downstream of Kamouraska could limit the range of juveniles (DFO 2010a, b). Consequently, Anse Sainte-Anne may be the most downstream feeding ground, used just prior to the winter (when feeding ceases), making it an extremely important site at this developmental stage for striped bass. It has been shown that in the Miramichi River, the size of juveniles is an important factor in survival during the winter. Juveniles must accumulate enough energy reserves during the short feeding and growth season to survive the winter which lasts at least 6 months (Robichaud-LeBlanc 1997). The situation may be similar for the striped bass of the St. Lawrence Estuary. In addition, analyses of juvenile striped bass of the historic population reveal no indication of movements upstream or downstream at the onset of the cold season. For example, in Montmagny or in Rivière-Ouelle, where striped bass aged 0+ were captured during the fall, individuals aged 1+ would be captured the following spring (Robitaille 2010).

The biomass of potential prey in Anse Sainte-Anne is considerable and the unique circulation pattern may contribute to the concentrations of prey and juvenile striped bass (DFO 2010a, b). D’Anglejan (1981) explains how exchanges between the independent water circulation of the Anse Sainte-Anne plateau, the silty flats of the intertidal zone and the Rivière Ouelle increases local turbidity. This concentration of suspended matter promotes primary production which is beneficial to the larvae of forage-fish and juvenile striped bass.

Data collected between 2002 and 2009 by the MRNF demonstrate that rainbow smelt make up most, approximately 75%, of the fish larvae community in Anse Sainte-Anne. The remaining 25% consists of Atlantic herring larvae and capelin larvae (Guy Verreault, MRNF, unpublished data). The analysis of the stomach contents of striped bass captured before the disappearance of the species revealed that prey consumed by juvenile striped bass vary according to place and season and include zooplankton, insects, worms, crustaceans (gammarus in freshwater and mysids in brackish water), and fish. Fish species most frequently identified were rainbow smelt, alewife (Alosa pseudoharengus), and banded killifish (Fondulus diaphanus) (Robitaille 2010). In addition, a review of the literature on the diet of the striped bass revealed that juveniles primarily consumed fish of the clupeidae family, such as Alosa spp and Atlantic herring, and shrimp of the mysidacea group (Walter et al. 2003).

To identify Anse Sainte-Anne as critical habitat is justified since it is a zone of juvenile concentration during the fall and will help ensure the recruitment and recovery of the species. The identified area covers 146.3 km² of sub-littoral and intertidal zone with a low tide depth from 0 to 5 m (Figure 5). Despite the fragmentary nature of information on habitat use by the reintroduced striped bass population, identification of this zone of juvenile concentration during the fall as critical habitat is a precautionary measure; particularly since juveniles were observed there before the disappearance of the striped bass and this area may be a vital feeding ground prior to the cold season (most downstream site).

A 940 km2 area of potential habitat consisting of a 320 km² intertidal zone and a 620 km² zone of low tide depths from 0 to 5 m was located between Neuville and Kamouraska (Pelletier et al. 2010). It is still too early to gauge the importance of this potential habitat but it will be possible to use Anse Sainte-Anne as a starting point in identifying critical habitat further upstream. The inventories which are part of the schedule of studies and the action plan will contribute to a better understanding of habitat use by striped bass in Anse Sainte-Anne and in the sector of the identified potential habitats. A more comprehensive description of habitat functions, features and attributes is also required.

Table 6 summarizes the essential functions, features and attributes of the striped bass critical habitat identified in this recovery strategy. At this time, critical habitat has been identified in the Anse Sainte-Anne where rearing functions for juveniles are supported. Data analysis of the historic and reintroduced striped bass population (DFO 2010a, b) has helped to identify important functions that would take place in other types of habitat (e.g., spawning and nursery), but these habitats have not been located yet. The schedule of studies to identify critical habitat aims to acquire the knowledge required to locate some of these habitats as well as other rearing habitats, particularly in the area of potential habitat identified by Pelletier et al. (2010). This should help identify other critical habitats.

Since habitat use is often temporal in nature, every activity is assessed on a case-by-case basis and site-specific mitigation is applied where it is reliable and available. The Government of Canada Species at Risk Act Policies, (2011 [draft]) describes destruction of critical habitat in the following manner: “Destruction of critical habitat would result if any part of the critical habitat were degraded, either permanently or temporarily, such that it would not serve its function when needed by the species. Destruction may result from single or multiple activities at one point in time or from cumulative effects of one or more activities over time.”

The critical habitat of the striped bass may be destroyed by human activities which modify the features or attributes necessary for the rearing function of the Anse Sainte-Anne critical habitat. Juveniles` presence in this bay (i.e. feature) could be explained by several attributes of the habitat: availability of sufficient quality and quantity of prey, thermal front area, high salinity gradient, unique circulation pattern that may contribute to increased turbidity and greater concentration of preys, and low tide depth from 0 to 5 m.

Dredging of the sea-bed and riparian modifications in the flood-plain such as infilling are examples of anthropogenic activities that are likely to result in the destruction of critical habitat of the striped bass by altering one or several attributes of Anse Sainte-Anne, such that it would not serve its function (table 7). It is important to mention that any human activity in Anse Sainte-Anne must be assessed on a case-by-case basis to determine if it is likely to destroy a feature of critical habitat, or its attributes such that the function is no longer available to the species when it is required.

The activities described in this table (table 7) are neither exhaustive nor exclusive and have been guided by the General Threats described in section 1.5 of this recovery strategy. The absence of a specific human activity does not preclude, or fetter the department`s ability to regulate it pursuant to SARA. Furthermore, the inclusion of an activity does not result in its automatic prohibition since it is destruction of CH that is prohibited. In every case, where information is available, thresholds and limits are associated with attributes to better inform management and regulatory decision-making. However, in many cases, the knowledge of a species and its critical habitat may be lacking, in particular information must be acquired in terms of threshold of tolerance of the species or its habitat to disturbance from human activities.

This recovery strategy includes an identification of critical habitat to the extent possible, based on the best available information. Further work is required to identify additional critical habitat necessary to support the population and distribution objectives for the species. To complete the identification of critical habitat, it is important to describe the distribution of striped bass according to season and developmental stage and to characterize the habitats used in order to understand what they provide to the species (Table 8). Once the habitats have been located and characterized, it will be possible to identify the habitats necessary for the recovery of the species. The schedule will be instrumental in reaching objective 2.4.5 of the present recovery strategy and completing the identification of critical habitat required for the forthcoming action plan. The ranking of studies according to developmental stage and the schedule itself are conditional on an increase in population. They will be updated in the forthcoming action plan.

The Species at Risk Act provides for the protection of the critical habitat of a listed species. The habitats of the striped bass are also protected under other Canadian laws includingthe Fisheries Act, the Canadian Environmental Protection Act and the Canadian Environmental Assessment Act. The provisions of these acts must be enforced in order to prevent disturbance, degradation or destruction of habitat in areas likely to contain spawning grounds, incubation habitats or habitats of larval development and consequently to protect the species.

In Quebec, protection of fish habitat is provided by the Act Respecting the Conservation and Development of Wildlife and the Environment Quality Act. In addition, shorelines are afforded protection under the Politique de protection des rives, du littoral et des plaines inondables (Protection policy for lakeshores, riverbanks, littoral zones and floodplains),the Cities and Towns Act and the Act Respecting Land Use Planning and Development.

Prior to the reintroduction of striped bass in the St. Lawrence Estuary, a risk analysis was conducted (Robitaille 2000). This document, approved by the members of the Comité aviseur sur la réintroduction du bar rayé, presents a review of the scientific and technical literature on the possible biological repercussions of reintroducing striped bass, including the effects on predators and competitors. The risk analysis concludes that the reintroduction of striped bass in the St. Lawrence Estuary should not lead to any significant decreases in the abundance of prey species. If the striped bass population recovers, a reallocation of trophic resources may occur between this species and other predators. The quantity of food resources consumed by the striped bass would not necessarily add to the quantity presently consumed by the piscivores in the area; the increased competition for resources may force other predators to expand their range or alter their diet. An evaluation of the effects on prey abundance would need to take into consideration not only the quantity of prey consumed by striped bass, but also the amount no longer consumed by other, displaced predators. This risk analysis, though, does not eliminate the need for adequate monitoring of the biological communities in this sector of the St. Lawrence. It does suggest, however, that the monitoring program should not be concentrated exclusively on just a few predator species, such as the vulnerable rainbow smelt and American shad, but should extend to other elements of the community, particularly the principal piscivores (Robitaille 2000).

The goal of the striped bass recovery strategy (Section 2.2 Recovery Goal) takes these knowledge gaps into account and stipulates that the recovery of the striped bass in the St. Lawrence Estuary must not cause significant disturbance to the biological community presently in place. In order to gauge the possible impacts the reintroduction of striped bass may have on the biological community, one of the recovery objectives formulated (Section 2.4 Recovery Objectives) calls for the monitoring of “the status of certain components of the ichthyological community (prey, predators, competitors) in relationship with the striped bass” and several measures to this end have been proposed (Section 2.5 Approaches Recommended to Meet Recovery Objectives). If significant changes to the biological community appear attributable to the reintroduction of striped bass, adjustments will be made to the recovery strategy.

The implementation of the recovery strategy will require an adaptive management approach. As new data is accumulated and progress is made in the recovery, or if new environmental conditions indicate that the proposed recovery measures are no longer appropriate, revised and more efficient approaches will be implemented. It is also recommended that the striped bass be part of all recovery initiatives targeting associated species.

If possible, the action plan (one or several chapters) will be developed within the five years following the approval of the recovery strategy. This delay allows for the acquisition of more information required to complete, as much as possible, the identification of critical habitat.

The Species at Risk Act stipulates that “No person shall kill, harm, harass, capture or take an individual of a wildlife species that is listed as an extirpated species, an endangered species or a threatened species.” (subsection 32 (1)). Under subsection 83(4) of the Species at Risk Act, “Subsections 32(1) and (2), section 33 and subsections 36(1), 58(1), 60(1) and 61(1) do not apply to a person who is engaging in activities that are permitted by a recovery strategy, an action plan or a management plan and who is also authorized under an Act of Parliament to engage in that activity, including a regulation made under section 53, 59 or 71.”

Although fishing for striped bass is prohibited in the St. Lawrence, accidental captures occur in the commercial and sports fisheries. The immediate release of this fish is mandatory, according to the Quebec Fishery Regulations (1990), SOR/90-214of the Fisheries Act,R.S.C., 1985, c. F-14.

In 2009, a committee of experts from the MRNF and DFO was formed to evaluate the impact of accidental captures of striped bass in the commercial and sports fisheries on the survival and recovery of the population. Despite the lack of data on the biology of the population and its vulnerability to accidental captures, the committee concluded that the freshwater and marine fisheries, as they are presently carried out, are unlikely, over all, to impact the survival and recovery of the striped bass population of the St. Lawrence Estuary (DFO 2009).

The committee report contained five recommendations to mitigate the impact of the fisheries, as a cause of mortality, on the striped bass population of the St. Lawrence Estuary and to monitor the population:

1. Implement mitigation measures (e.g., mandatory release of catches) to reduce the possible impact of the commercial and sports fisheries on the striped bass population;
2. Take the necessary steps to ensure that accidental captures are recorded;
3. Promote awareness in the fishing industry;
4. Maintain a monitoring network focused in part on the accidental captures of striped bass by commercial fishermen and authorizing the collection of specimens;
5. Re-evaluate the impact of accidental captures within five years, or sooner if changes are observed in the vulnerability of striped bass to accidental captures in the commercial and sports fisheries.

In accordance with subsection 83(4) of SARA, the present recovery strategy authorizes fishermen to carry out sport or commercial fishing subject to the following conditions:

• fishing is carried out in accordance with a sport or commercial fishing license issued under the provisions of the Quebec Fishery Regulations (1990), SOR/90-214;
• any person who accidentally captures a striped bass while fishing shall without delay return the fish to the waters in which it was caught and, if the fish is alive, release it in a manner that causes the least harm to the fish.

A monitoring network has been set up to document the establishment of striped bass which have been stocked, to evaluate population parameters, to trace their movements, and to verify the occurrence of natural reproduction. Commercial fishermen who are part of the network must possess a permit for the capture of wildlife for scientific, educational or wildlife management purposes (SEG permit) issued by the MRNF authorizing them to keep accidentally captured striped bass and deliver them to MRNF biologists.

In accordance with subsection 83(4) of SARA, the present recovery strategy authorizes fishermen to carry out commercial fishing and the capture of striped bass for scientific, educational or wildlife management purposes, subject to the following conditions:

• fishing is carried out in accordance with a commercial fishing license and a permit for the capture of wildlife for scientific, educational or wildlife management purposes (SEG permit) issued under the provisions of the Quebec Fishery Regulations (1990), SOR/90-214;
• any person who accidentally captures a striped bass while fishing must deliver it to the MRNF biologists responsible for striped bass and following the dates and conditions of the SEG permit referring to the species.

Furthermore, in accordance with subsection 83(4) of SARA, the present recovery strategy authorizes fishermen to fish under the provisions of an aboriginal communal fishing licence, subject to the following conditions:

• fishing is carried out in accordance with a communal licence issued under the provisions of the Aboriginal Communal Fishing Licences Regulations, SOR/93-332;
• any person who accidentally captures a striped bass while fishing shall without delay return the fish to the waters in which it was caught and, if the fish is alive, release it in a manner that causes the least harm to the fish.

⁶ Corresponds to the chart datum (CD) derived from the mean level of low water at spring tide.