Research Document - 2003/008
Assessment of striped bass (Morone saxatilis) in the Maritime Provinces in the context of species at risk
By Douglas, S.G., Bradford, R.G., and Chaput, G.
Abstract
There are two extant populations of striped bass in the Maritime Provinces: the southern Gulf of St. Lawrence population that spawns in the Northwest Miramichi River in northern New Brunswick, and a population in the Bay of Fundy that spawns in the Shubenacadie-Stewiacke River, Nova Scotia. Evidence of extirpated striped bass populations exist for the Annapolis and Saint John rivers that flow into the Bay of Fundy. Genetic discreteness between the two extant Canadian populations and their discreteness from adjacent spawning populations of the eastern U.S.A. has been demonstrated from analyses of mitochondrial and nuclear DNA. There are no reported occurrences of fish tagged in either the NW Miramichi or the Shubenacadie-Stewiacke having been recaptured as spawners in any river other than their presumed river of origin. Both populations of striped bass in the Maritime Provinces are managed as discrete biological units. Their genetic structuring relative to the larger striped bass assemblage in eastern North America, in combination with evidence for unique life-history attributes of probable adaptive significance at the population level, and their contribution to biodiversity within two recognizable biogeographic regions within Canada lend support to their designation as "evolutionarily significant units". As such, the present DFO management framework for this species is already applied at the level that reflects their conservation significance. Assessment of the striped bass spawning run to the NW Miramichi since 1993 reveals that this population has undergone large fluctuations in size. Spawner estimates for the NW Miramichi peaked in 1995 at 50,000 fish, dropped to approximately 4,000 fish between 1998 and 2000, but have recovered to between 24,000 and 29,000 in 2001 and 2002. Spawner abundance data available for the Shubenacadie-Stewiacke population does not yet lend itself to analysis of interannual trends. Provisional estimates of spawner abundance for 2002 are in the range of 20 to 30 thousand fish of minimum reproductive age (age 3+ years). Available data indicate that several age classes have contributed eggs to the population every year since 1999. Based on landings, and tag returns, the area of occupancy for striped bass in the southern Gulf of St. Lawrence appears unchanged with striped bass occurring seasonally throughout the inshore, coastal portions of the whole region. Beach seine surveys indicate that young-of-the-year striped bass leave the Miramichi system during summer and are distributed throughout much of the southern Gulf by the end of their first growing season. Tag returns from fish marked while descending the Shubenacadie River in May (1999-2002) suggest a summer range within Minas Basin, although this interpretation is likely confounded by low recreational fishing effort outside of Minas Basin. The summer seaward distribution of young-of-the-year Shubenacadie-Stewiacke striped bass appears to be limited to the inner, turbid, and relatively warm water portions of Minas Basin. All indications are that there are in excess of 10,000 mature individuals in both extant Maritime populations.
Accessibility Notice
This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.
- Date modified: