Science Response 2016/033

Effects of dredging activities on St. Lawrence beluga and their habitat

Context

The Fisheries Protection Program of the Department of Fisheries and Oceans regularly receives requests to review maintenance dredging and at-sea disposal of dredged sediment for wharves located in the Beluga distribution range in the St. Lawrence Estuary (SLE).

This Science Advisory Report stems from a request that the Regional Ecosystems Management Branch (REMB) submitted to the Regional Science Branch. This branch prepared a Science Advisory Report in 2002: Programme décennal de dragage d’entretien au quai de Rivière-du-Loup – Questions relatives aux effets sur le béluga de l’estuaire du Saint-Laurent. Since our knowledge of the Beluga and its status have changed since 2002, the REMB would like to verify the following:

1. Is the SAR the Science Branch prepared in 2002 still valid for wharf repairs and dredging in Rivière-du-Loup, particularly for aspects related to the identified impacts and mitigation measures proposed?

Dredging should not be permitted in April, May or June. Work should begin in early July and continue intensively (night and day, 7 days a week) to ensure that it is completed before the end of July or by mid-August at the latest.

1. Is there new information on the potential effects of dredging (including at‑sea disposal of dredged sediment) on the Beluga?
2. Are new mitigation measures recommended at the site of the dredging and at-sea disposal of dredged sediment in Rivière-du-Loup?
3. If the work is being performed outside periods when food resources are at their peaks (April to June), would it be preferable to advise that work be carried out as quickly as possible or in a way to provide periods of low ambient noise (e.g., work stoppage at night for eight consecutive hours) to provide an auditory rest from the noise, promote physiological recovery and increase the effectiveness of communication, among other things?
2. Could the SAR apply to all dredging and sediment disposal projects carried out in the Beluga's range?
1. Should different measures apply for dredging work carried out in the distribution range other than the critical habitat?
2. Should different measures apply for dredging work carried out in the distribution range (outside the critical habitat) during periods when the Estuary is highly used (June to October) compared with similar projects carried out outside this period (November to May)?

The document is structured to provide basic information on the current status of the SLE Beluga population, as well as their biology and ecology. Given the rapid development of research related to effects that onshore and offshore development projects have on marine mammals, a section was prepared to review the mechanisms and expected magnitude of the effects associated with dredging activities with regard to marine mammals and Belugas. Since the request includes aspects specific to recurring dredging areas like Rivière-du-Loup, a section was also added to deal specifically with this area.

This Science Response Report results from the Science Response Process of May 2016 on the Assessment of the effects of dredging activities on St. Lawrence beluga and their habitat.

Complete document (PDF, 275 KB)

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