Science Advisory Report 2017/001

Information in Support of Critical Habitat Identification for Striped Bass (Morone saxatilis) of the St. Lawrence River

Summary

• Since 2010, a series of scientific fisheries and a network of acoustic receivers strategically placed in the St. Lawrence River and its main tributaries have helped to monitor the movements of striped bass fitted with acoustic transmitters and thereby to identify the main areas of adult concentration. In 2013, the implementation of a standardized survey program resulted in an annual recruitment index that monitors reproductive success.
• The range of the St. Lawrence River striped bass population was defined as the area frequented by at least 10 percent of the tagged striped bass. Based on this criterion, the range extends from upstream of Gentilly to Rivière-Ouelle on the south shore, and upstream of the Saguenay, on the north shore. The delineation of the range downstream, on the north shore, is currently inaccurate because no receivers have been installed beyond the Saguenay River. However, the total range extends beyond these boundaries, with an area of overlap with the neighbouring population of the southern Gulf of St. Lawrence.
• The seasons play a major role in the spatial and temporal distribution of striped bass. Striped bass congregate in limited areas in the winter and disperse to cover large areas in the spring and summer. The arrival of fall initiates a movement to return to wintering sites.
• In winter, adult striped bass are heavily concentrated south of Isle-aux-Grues, near Québec City. The movements of striped bass were also observed between these two wintering areas, which suggests that the Chenal des Grands Voiliers linking these two areas is minimally used as a winter travel route.
• During the open water period, an area of special importance for adult striped bass was observed along the north shore of the upper estuary, at Isle-aux-Coudres. Another important area was identified on the south shore of the St. Lawrence, starting upstream of Québec City, continuing along the Chenal des Grands Voiliers south of Île d’Orléans, encompassing the area surrounding Isle-aux-Grues, and ending just downstream of Rivière-Ouelle. Within this area of concentration, three sites are distinguished by an especially significant presence of striped bass during the period suitable for reproduction: Beauport Bay, the mouth of the Rivière du Sud and the Rivière Ouelle. Unlike the first two sites, the presence of striped bass in Rivière Ouelle remains high throughout the open water period.
• A first spawning ground was identified at the mouth of Rivière du Sud at Montmagny in 2011. The observations made at the Québec port area strongly suggest that this is also a spawning area for the striped bass population in the St. Lawrence River.
• Rivière Ouelle seems to play an important role during the reproduction period. Significant concentrations of individuals have been observed before, during, and after the reproduction period, especially of adult females. However, additional work is needed to identify the role of this river.
• An intertidal area of 0-5 metres with habitat potential for the larvae and young-of-the-year was delineated. This area lies between Lévis and Rivière-du-Loup on the south shore, and between Neuville and Petite-Rivière-Saint-François on the north shore, and includes the islands in these areas. However, additional studies are required to better define the areas of particular importance for these early stages.
• Even so, the results confirm the importance of Anse Sainte-Anne as a habitat for young striped bass in the fall.
• Since information on the habitat of sub-adults (individuals one to three years of age) is still missing, additional work is required to identify the critical habitats for this stage of life.

This Science Advisory Report is from the March 15, 2016, meeting on the assessment of habitat required for the survival and recovery of the St. Lawrence Estuary striped bass population. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada Science Advisory Schedule as they become available.

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