Beluga whale (Delphinapterus leucas), St. Lawrence Estuary population, recovery strategy: chapter 3

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2. Recovery

• 2.1 Population and distribution objectives
• 2.2 Recovery objectives
• 2.3 Strategies and measures to achieve recovery objectives
  • 2.3.1 Recovery planning
  • 2.3.2 Narrative to support the recovery planning
• 2.4 Critical habitat
  • 2.4.1 Information and methods used to identify critical habitat
  • 2.4.2 Description of critical habitat
  • 2.4.3 Schedule of studies to identify critical habitat
  • 2.4.4 Examples of activities likely to destroy critical habitat
• 2.5 Knowledge gaps
• 2.6 Measuring progress
• 2.7 Statement on action plans

2.1 Population and distribution objectives

In the St. Lawrence Beluga Recovery Plan published in 1995, the recovery goal was: “to bring population numbers and conditions to a state at which natural events and human activity will not threaten the survival of the St. Lawrence beluga whale population…it appears that reducing pollution and disturbance should ensure that humans and belugas will continue sharing the St. Lawrence Estuary” (Fisheries and Oceans Canada [DFO] and World Wildlife Fund [WWF], 1995). The goal of the current recovery strategy remains to restore the beluga population to a level where its survival is no longer threatened by natural and anthropogenic disturbances.

The historical population is estimated at 10 100 individuals (DFO, 2005b). The long-term population objective of the St. Lawrence Estuary beluga is 7070 individuals, or 70% of its historical population, which corresponds to the precautionary approach adopted by DFO for managing various marine resources (DFO, 2006; Hammill and Stenson, 2007). However, this population could be considered no longer at risk before this objective is reached (DFO, 2005b). At the current 1% annual growth rate, this long term objective could be achieved by 2100. If limiting factors for population growth are identified and eliminated, the growth rate could attain a theoretical maximum of approximately 4%, in which case the long-term population objective would be achieved by 2050 (Figure 8). This recovery strategy also aims for a minimum 2% population growth rate. In order to have an intermediate population objective that could maintain genetic diversity, an objective of 1000 mature individuals was also determined. According to the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assessment criteria, achievement of this intermediate objective could result in a lower risk category. As the population increases, it is hoped that the distribution area of the St. Lawrence beluga will also increase to a minimum level corresponding to 70% of the historical distribution area (DFO, 2005b).

Figure 8. Time to meet the population objective of 7070 individuals at the current growth rate of approximately 1% and at the theoretical maximum rate of 4%

2.2 Recovery objectives

To achieve the population and distribution objectives of this recovery strategy, six recovery objectives have been identified:

1. Reduce contaminants in belugas, their prey, and their habitat that could prevent population recovery;
2. Reduce anthropogenic disturbances;
3. Ensure adequate and accessible food supply;
4. Mitigate the effects of other threats to population recovery; 
5. Protect beluga habitat throughout the entire distribution range;
6. Ensure regular monitoring of the St. Lawrence Estuary beluga population.

Strategies to reach these recovery objectives are put forward in the following table.

2.3 Strategies and measures to achieve recovery objectives

2.3.1 Recovery planning

Level of priority: Beneficial, or useful for recovery; Necessary, or having great potential for recovery; Critical, or indispensable for recovery.

2.3.2 Narrative to support the recovery planning table

Each of the first three objectives targets a specific threat to the recovery of the St. Lawrence beluga: contaminants, anthropogenic disturbances, and prey availability. Many toxic chemicals discharged by past, current, and future industrial processes and modern consumer products can hinder the recovery of the St. Lawrence belugas by interfering with their vital functions or by inducing potentially fatal pathologies. A reduction in contaminant levels is therefore a priority objective to ensure the recovery of this population. Anthropogenic disturbances, on the other hand, stem primarily from the high volume of commercial and recreational marine traffic along the St. Lawrence Estuary, including observation activities at sea. There is a need to propose approaches to reduce the risk related to anthropogenic disturbances from the different types of vessels or noise associated with human activities. Many fish stocks in the St. Lawrence Estuary have been reduced in recent decades. Despite their varied diet, belugas may no longer be able to find prey in sufficient quantity or quality to ensure population recovery in the Estuary. Another objective of the recovery strategy is therefore to ensure adequate and accessible food supply.

Other threats to the recovery of the St. Lawrence beluga have been included under the fourth objective: “Mitigate the consequences of other threats to population recovery.” It is critical that approaches be proposed to mitigate or eliminate all threats, and that vigilance be maintained to identify new threats. It is equally critical to deepen our understanding of habitat use in order to protect important areas in the St. Lawrence. Belugas occupy various habitats, depending on the season, and we know little about what are the important features of the habitat, or about the functions they support.

Finally, despite the ban on hunting, the growth rate of the St. Lawrence Estuary beluga population remains very low. Continued monitoring of the population status, particularly the juvenile mortality rate, is required to determine the effectiveness of any recovery measures. Monitoring is also essential to identify and better understand the most serious threats to this population and to find the means to mitigate or eliminate them.

2.4 Critical habitat

The Species at Risk Act (SARA) stipulates that a recovery strategy must include “an identification of the species’ critical habitat, to the extent possible, based on the best available information, […], and examples of activities that are likely to result in its destruction” (paragraph 41(1)(c)). This identification is designed to facilitate the protection of the critical habitat of the St. Lawrence beluga from human activities that can destroy it and compromise the survival and recovery of the species.

Critical habitat is defined in the Species at Risk Act (2002) section 2(1) as:

SARA defines habitat for aquatic species at risk as:

For the St. Lawrence beluga, 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 survival and recovery of the species, but, due to inadequate information, it is not possible to know whether it is sufficient to achieve the population and distribution objectives for the species. In particular, knowledge on critical habitat features and their attributes which support vital functions is insufficient. The schedule of studies outlines the research required to obtain better knowledge on the critical habitat and to identify additional critical habitat necessary to support the population and distribution objectives for the species.

2.4.1 Information and methods used to identify critical habitat

In order to identify the critical habitat of the St. Lawrence beluga, all the available information on the beluga’s habitat requirements, its prey, seasonal distribution, use and characteristics of its habitat has been reviewed (Mosnier et al., 2009). The information was gathered from academic, governmental, and non-governmental sources. This literature review was used to produce a science advisory report on the identification of critical habitat for the St. Lawrence beluga that was peer-reviewed and published (DFO, 2009a). The identification of critical habitat was then discussed with the St. Lawrence beluga Recovery Team in May 2010. This team includes marine mammal experts. Using the available information and the scientific advisory report (DFO, 2009a), the Recovery Team recommended the identification of the critical habitat as it is presented in this strategy.

To date, the knowledge of the beluga’s habitat is largely based on the current summer use. Historical use and current winter habitat use are less well known. Present knowledge suggests a spatial segregation of belugas based on sex and age, which is typical of this species in the summer. The Upper Estuary, where the females with calves and juveniles are concentrated, is likely an important habitat for calving and rearing of the young. The reasons why this segregation occurs and the habitat’s attributes that make it critical to the survival of females, calves and juveniles are not clearly defined. The identification of the St. Lawrence beluga critical habitat is based on the summer distribution range of females and their calves because this habitat supports the function of calving and rearing of the young and thus juvenile survival. Based on the hypothesis of juveniles having difficulties to survive that was put forward to explain the absence of recovery since the hunting ban, the Minister of Fisheries and Oceans considers this habitat critical to the survival and recovery of the St. Lawrence beluga. The northern portion of the Lower Estuary is known to be used for feeding by groups of adults only, which are not as strongly attached to this habitat as groups of females with calves and juveniles to their summer habitat. Only groups of adults exhibit a greater mobility for feeding and likely occupy a larger area, even in the summer. The use of this area by the beluga will have to be further studied as indicated in the schedule of studies to identify critical habitat (Table 5).

Figure 9. Critical habitat of the St. Lawrence beluga.

2.4.2 Description of critical habitat

Critical habitat has been identified using the area of occupancy approach and corresponds to the summer distribution of groups made up of adults and new-born calves and juveniles, i.e. the Upper Estuary, from the Battures aux Loups Marins to the Saguenay River and the southern portion of the Lower Estuary (Figure 9).

Oceanographic processes leading to mineral-rich and productive cold water upwelling offer a suitable environment and favour continous beluga presence. The distribution pattern of the beluga throughout its summering ground probably reflects the different ecological and behavioral needs of the different social groups. In summer, i.e. from June to October, belugas congregate in groups according to sex and age. In the St. Lawrence, groups made up of adult females accompanied by their new-born calves and juveniles concentrate in the Upper Estuary, while groups of adults only tend to gather in the northern section of the Lower Estuary (Figure 6). Females are very strongly attached to their summer habitat, characterized by an abundance of prey and shallower waters (Table 4), to which they return every year. The identified critical habitat (Figure 9) clearly provides support for calving and the rearing of the young, a fundamental issue in the survival and recovery of this threatened species (DFO, 2009a; Mosnier et al., 2009). The rearing of the young requires access to quality food sources and an environment that is conducive to communication. The shallower waters preferred by females, new-born calves, and juveniles may offer protection from predators and ensure access to adequate food resources for smaller belugas with limited diving capabilities.

Although the physical, chemical and biological characteristics that make these habitats critical for the survival and recovery of the beluga are not well known, the fact that females and their calves return so faithfully to sites in the Upper Estuary, the Saguenay River, and the southern portion of the Lower Estuary supports the critical importance of these areas (DFO, 2009a).

2.4.3 Schedule of studies to identify critical habitat

Paragraph 41(1) c.1 of SARA calls for “a schedule of studies to identify critical habitat, where available information is inadequate.” This recovery strategy includes the identification of critical habitat to the extent possible based on the best available information. Further studies are needed to fully identify the St. Lawrence beluga critical habitat, meaning the critical habitat needed to support the population and distribution objectives. As few studies have been conducted on the critical habitat used by the beluga outside the area between Kamouraska and Rimouski, it is impossible at this time to determine the contribution of these other areas to the critical habitat. Moreover, the beluga’s preferred habitat outside the summer season is largely unknown. More information is also needed on the attributes of the identified critical habitat in order to make sure that they are of adequate quality and quantity to support vital functions of the species. In particular, a better understanding of the attributes is needed to understand the requirements of the beluga towards its acoustic environement and the various biophysical caracteristics of the habitat (underwater topography, currents, water temperature, salinity, oxygen, pH, nutrients, freshwater discharge and turbidity) that can influence presence of belugas or their prey.

The schedule of studies presented in Table 5 describes the research activities required to identify all critical habitat of the St. Lawrence beluga in accordance with the population and distribution objectives.

2.4.4 Examples of activities likely to destroy critical habitat

The definition of destruction is interpreted in the following manner:

Under SARA, critical habitat must be legally protected from destruction once it is identified. This will be accomplished through a s.58 Order, which will prohibit the destruction of the identified critical habitat unless permitted by the Minister of Fisheries and Oceans Canada pursuant to the conditions of SARA.

It is important to mention that any human activity must be assessed on a case-by-case basis and mitigation measures have to be applied when available and efficient. The activities described in Table 6 are not exhaustive and have been guided by the “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 because it is destruction of critical habitat that is prohibited. Activities generating high levels of noise and those that could destroy the habitat attributes likely to impact significantly prey abundance can result in the destruction of critical habitat.

Excessive noise pollution can prevent belugas from carrying out these vital functions, and would therefore constitute the destruction of critical habitat.  Although the threshold level of acoustic degradation that would destroy the St. Lawrence beluga’s critical habitat has not yet been established, the scientific literature (Richardson et al., 1990; Richardson et al., 1995) and the U.S. National Marine Fisheries Services (NMFS, 2003) have established the threshold level of disturbance for marine mammals at 120 dB from continuous sources and 160 dB from pulse sources. The threshold for physical damage is set at 180 dB. These thresholds are given as an indication only; they can vary according to several factors such as sound frequency or oceanographic conditions.

A marked decrease in the availability of sufficient quantity and quality of beluga prey within the critical habitat would compromise that habitat’s function as a food source. Underwater topography, currents, water temperature, salinity, oxygen, pH, nutrients, water regime or freshwater discharge, and turbidity can potentially affect the beluga’s prey. Barriers to fish migration can also affect their abundance and their availability.

2.5 Knowledge gaps

Although many threats have been identified, only a few, such as contaminants, have been closely studied, while others remain hypothetical. It is therefore imperative to conduct further research on the population status and limiting factors for population growth. The following is a partial list of the main research priorities to fully implement this recovery strategy:

Biology and ecology

• Population dynamics (particularly juvenile survival rate)
• Distribution and seasonal behaviour (especially outside summer)
• Social structure and reproduction strategies
• Diet and energy requirements

Habitat

• Key prey species distribution, abundance, habitat, biology, and threats

Threats

• The complete spectrum of anthropogenic environmental contaminants to which belugas and their prey are exposed, in space and over time, with particular attention to the identification of sources of environmental contaminants, in particular emerging contaminants and their effects on belugas, their prey, and their habitat
• Short- and long-term effects of disturbance due to noise levels and physical proximity to human activity
• Anthropogenic sources of pathogens
• Frequency and intensity of ship strikes and entanglement
• Threat mitigation measures
• Other obstacles to recovery
• The influence of climate change on the impacts of threats to recovery

As mentioned in the previous section, many research and monitoring programs are currently gathering more information on threats to the recovery of St. Lawrence belugas, its population status, and the impact of current or proposed management strategies. It is important to continue this research while focusing on actual, potential, and anticipated threats to the St. Lawrence beluga population. In addition, a full evaluation of the impacts of these threats on recovery will require a better understanding of the population dynamics, in particular the juvenile recruitment rate and seasonal habitat use. The research activities required to identify critical habitat are described in section 2.4.3 Schedule of studies to identify critical habitat.

2.6 Measuring progress

The performance indicators presented below provide a way to define and measure progress toward achieving the population and distribution objectives. Specific progress towards implementing the recovery strategy will be measured against indicators outlined in subsequent action plans.

• Increase in population size
• Increase in the number of mature individuals to 1000 adult belugas
• Increase in the distribution area
• Increase in the yearly recruitment rate
• Steady state calving percentage
• Decrease in the mortality rate of juveniles

2.7 Statement on action plans

An action plan for the St. Lawrence Estuary beluga population will be completed within 5 years, by 2016.