Research Document - 1999/006

Genetic investigations on striped bass (Morone saxatilis) in the Canadian Maritime provinces.

By M. Robinson and S.C. Courtenay

Abstract

The striped bass (Morone saxatilis) is an anadromous fish native to the eastern coast of North America. Analysis of mtDNA restricted fragment length polymorphisms (RFLPs) has shown that the Bay of Fundy and the southern Gulf of St. Lawrence each contain a genetically distinct stock of striped bass. Juvenile bass from two neighboring rivers in the southern Gulf of St. Lawrence (Miramichi and Tabusintac) were not differentiated by this mtDNA RFLP analysis. No evidence of mixing was observed between the Bay of Fundy and southern Gulf of St. Lawrence striped bass populations. A second analysis of mtDNA from Bay of Fundy fish has shown that striped bass in the Saint John River are composed largely of American fish from the US coastal migratory stock. Studies in the southern Gulf of St. Lawrence have shown that young-of-the-year (YOY) striped bass from the Miramichi estuary are migratory. During the late summer of 1997 and 1998, YOY striped bass extended their range beyond the Miramichi Estuary to at least the Richibucto Estuary in the south. The magnitude of the range extension to the north was not investigated. Plankton sampling and beach seining in the Kouchibouguac and Richibucto Rivers in 1997 and 1998 failed to find any evidence of striped bass spawning. A microsatellite analysis of nuclear DNA is underway to determine if YOY collected in the Kouchibouguac and Richibucto estuaries are emigrants from the Miramichi River. This study will also serve to confirm previous conclusions regarding the level of divergence between Bay of Fundy and southern Gulf of St. Lawrence striped bass stocks. At this time there is evidence of only 2 spawning populations of striped bass in Canada: the Miramichi River in the southern Gulf of St. Lawrence and the Shubenacadie River System in the Bay of Fundy. Although the Miramichi River may be the only striped bass spawning site in the southern Gulf, many other rivers and estuaries in the area may act as important rearing habitat or "nursery areas" for YOY migrants.

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