Recovery Strategy for the Striped Bass, St. Lawrence Estuary Population, Canada [Final] 2011: Recovery
The recovery of the striped bass population of the St. Lawrence Estuary is deemed feasible because it meets the four following conditions:
1. Availability of Individuals with Reproductive Capability:
Stocking of striped bass in the St. Lawrence begun in 2002 and six years later mature individuals with spawning capability were once again present in the system. Thanks to the monitoring network, young-of-the-year (aged 0+) were captured in 2008 though no stocking had occurred for that age group that year. This confirms the presence of a spawning population of striped bass in the St. Lawrence. Further stocking over the next few years, combined with natural reproduction, should augment their number. At the present time, it is impossible to determine if the number of stocked individuals is sufficient to ensure recovery of the population and continued stocking is thus recommended.
2. Availability of Adequate Habitat to Support the Species:
The fact that striped bass have been captured in several areas along the St. Lawrence River and Estuary suggests that the recovering population occupies a range comparable to that of the historic population. Biological data collected to date indicates that the growth conditions for striped bass of the new population are good (Pelletier 2009). Furthermore, as previously mentioned, naturally-spawned juveniles have been captured. This is an indication that there exist adequate habitats for spawning, incubation and larval development, though these habitats have not yet been located or quantified.
3. Elimination or Mitigation of Threats:
Several threats to the recovery of the striped bass have been identified in the present recovery strategy. Some of these threats, however, can be eliminated or mitigated. For example:
Accidental captures: The striped bass fishery is presently closed and accidental captures must be immediately released. In 2005, an awareness campaign was carried out among sports fishermen to inform them about the mandatory release of striped bass by-catches and to encourage them to report these catches to the CDPNQ. Several commercial fishermen are also involved in monitoring the striped bass population and have been issued SEG permits which authorize them, within strict guidelines, to keep accidental captures and deliver them to the MRNF.
Habitat disturbance due to dredging: Dredging and sediment disposal practices have improved since the time when the striped bass population disappeared and are now designed to limit impacts on the aquatic ecosystem. During the 1970s, designated deep-water sites were used to dump dredged material. In 2009, the Coast Guard stopped using the dump site just south of Île Madame (adjacent to the historic feeding grounds of immature striped bass). This site should be closed to all users as of 2011.
Disturbance and destruction of habitat: The 1960s and 70s saw the destruction of extensive areas of fish habitat. Today, all development projects likely to cause habitat disturbance or destruction must receive authorization from the DFO, under the Fisheries Act, the ministère du Développement durable, de l’Environnement et des Parcs (MDDEP), under the Environment Quality Act, or the ministère des Ressources naturelles et de la Faune (MRNF), under the Act Respecting the Conservation and Development of Wildlife.
4. Availability of Efficient Recovery Techniques and Measures:
In the United States, the striped bass has been the subject of a great many articles in scientific and technical journals. Numerous recovery techniques and measures are available and have been proven to work in different fields. The measures implemented to date for the St. Lawrence population include production in captivity, stocking and the mandatory release of accidental catches.
To reintroduce striped bass in the St. Lawrence, the goal of the initial program was to stock 50,000 fry each year (Comité aviseur sur la réintroduction du bar rayé 2001), which was to begin in the next few years. However, due to the high survival rate of striped bass kept in captivity at the Baldwin-Coaticook fish hatchery, stocking of surplus individuals began earlier than expected and some of these have begun to spawn in the St. Lawrence. It would appear that the development of a new population has already started.
The striped bass of the historic St. Lawrence population, subjected to overfishing at the pre-spawning stage, was never adequately protected, unlike some of the American populations. The large migratory populations of the east coast (Hudson River, Roanoke River, Chesapeake Bay) remained at very low levels of abundance for over twenty years (1970s and 80s) and this decline in population could not be explained. When a federal law was passed prohibiting all fishing of striped bass in the states along the Atlantic coast, populations recovered in less than five years (Field 1997). When conditions are right, the establishment or recovery of a striped bass population may be achieved rapidly. This may also prove to be the case for the new population of striped bass in the St. Lawrence, given that all fishing has been prohibited.
The goal of the recovery strategy is to restore, over the next ten years, a striped bass population capable of reproducing and sustaining itself in the St. Lawrence Estuary and of integrating itself into the biological community without disturbance.
Population: It is presently impossible to establish a quantitative population objective. There are no estimates of historic population numbers to serve as guidelines for the recovering population. The qualitative population objective is the recovery of a self-sustaining, viable population.
Range: From the fisheries data on the historic population and analyses of mark-recapture data, it is possible to make a provisional identification of the range that the new population may cover. At the present moment, striped bass seem to occupy the same distribution zone, but it is impossible to determine the precise area. It is, however, important to note that the habitats frequented by juvenile striped bass, before the disappearance of the species, have been severely reduced since the 1960s, especially around Quebec City and the along the North Shore. This could alter the new population`s range. This habitat loss may also have reduced the carrying capacity of foreshore habitat for juveniles, which may impact the entire population in unforeseeable ways. Changes have also occurred in the biological community of the estuary. Native species such as rainbow smelt and Atlantic tomcod (Microgadus tomcod) have undergone decreases in abundance while other species, such as yellow walleye, have increased in numbers. Some exotic species, such as the round goby, have moved into the area. It is impossible to determine whether the area`s carrying capacity in terms of predator fish, and the striped bass in particular, has been altered. Taking into account these changes and the existing knowledge gaps, the distribution range objective can only be described qualitatively: it should include all adequate habitat.
Data gathered by the monitoring network will help fill the knowledge gaps and will serve to define quantitative population and distribution objectives
The following list of objectives takes into account the fact that several of the stages outlined in the working document of the Comité aviseur sur la réintroduction du bar rayé have been completed (see Section 1.6 Measures Completed or Underway). The objectives described below are designed to contribute towards the same goal without, however, repeating work already done.
The first objective is to increase the present number of striped bass in the St. Lawrence by stocking 50,000 autumn fry each year, the same number put forward in the MRNF action plan for the reintroduction of striped bass (Comité aviseur sur la réintroduction du bar rayé 2001). In order to officially begin the reintroduction program, the survival of fry in hatcheries needs to improve because presently the survival rate of larvae is excellent, but the present rate of mortality before reaching the fry stage is too high to produce the 50,000 fry proposed in the MRNF plan. Until now, the stocked specimens have been the surplus individuals bred in the hatcheries (considered surplus based on the requirements of spawning stock and the space available for the development of larvae).
Initial data on the new population, particularly concerning development and the start of natural reproduction, suggest that the recovery of the striped bass has already begun. However, the species is noted for its irregular recruitment, which is dependent on a variety of conditions in the habitats where early development occurs. It is thus vital to continue the stocking initiative for several more years.
The objective here is to fill critical gaps in our knowledge of the new, as well as the historic, populations. More data is required on the areas where spawning, incubation and larval development occur. Also required is a more precise determination of the present boundaries of some other habitats, the approximate limits of which have been deduced from data on the historic population (e.g., spawning, incubation and larval development grounds, summer feeding grounds, migration routes, and overwintering grounds).
More information is required on the habitats used by striped bass during the different stages in the life cycle and during the different seasons to ensure the protection of the population. This will also enable researchers to design sampling strategies to identify the parameters of population dynamics.
This objective is to monitor the status of the population by identifying the biological and dynamic characteristics of the recovering striped bass population, the natural production and survival of new individuals and the total range being used.
These data, collected on a regular basis, will provide a comprehensive overview of the striped bass population (e.g., fecundity, survival in the different stages, and factors which most influence population dynamics) and will be used to determine quantitative population and distribution objectives. They will also make it possible to conduct regular evaluations of the stocking protocol in order to avoid disrupting the natural reproduction of the striped bass.
The recovery of the striped bass may provoke changes within the biological community of the estuary. The fourth objective is to acquire biological data on the fish in the estuary that interact with striped bass: prey, predators and competitors. In order to make the proper adjustments to the reintroduction program, it is necessary to develop indicators to identify which changes within the biological community are caused by the reintroduction of striped bass.
This objective is directly connected to the second objective. Once the habitats used by the striped bass have been located, it will be possible to determine which are the most vital (in terms of their function and the proportion of the population located there during certain periods of the year) and consequently implement the appropriate protective measures. Habitats necessary to the survival or recovery of the striped bass may be designated critical habitat under the SARA.
The measures required to reach these objectives are presented in Table 4, together with their levels of priority, the strategies they represent and, where appropriate, the threats they address.
The level of priority distinguishes between measures considered essential, necessary or desirable in order to reach the objectives. The “Strategy” column identifies which of the following five categories of actions the measures fall under:
- Inventory and monitoring
- Acquisition of knowledge
- Artificial production and stocking
- Protection, restoration and stewardship
- Outreach
To be able to evaluate the implementation and progress of the recovery strategy, a list of performance indicators for each objective is presented in Table 5. These performance indicators will help determine whether the recovery methods are having a positive impact on the species. They will also assist in evaluating whether or not the recovery objectives are being met and assessing the level of progress being made.
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