Science Advisory Report  2014/053

 Recovery Potential Assessment for the Bay of Fundy Striped Bass (Morone saxatilis) Designatable Unit

Summary

• The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has designated the Bay of Fundy (BoF) Striped Bass Designated Unit (DU) as ‘at risk’ on two occasions, most recently as Endangered in 2012.
• The BoF DU is considered to be comprised of three spawning populations: the Saint John River population in New Brunswick, the Shubenacadie River, and Annapolis River populations in Nova Scotia.
• The BoF DU presently consists of a single known spawning population in the Shubenacadie River, Nova Scotia.  There is a possible spawning population in the Saint John River, New Brunswick, but there has been no direct evidence of spawning activity there in the last 30 years. Striped Bass in the BoF DU also historically spawned in the Annapolis River, Nova Scotia.  While Striped Bass continue to feed in this river, no viable spawning has occurred since 1976.
• Evaluation of the status and area of occupancy of the BoF Striped Bass DU is confounded by the presence of US migrants within the BoF and Gulf of Maine.
• There are indications that the spawner abundance in the Shubenacadie River may have increased since 2002.
• Striped Bass populations exhibit significant variability in recruitment, the consequence of variable spawner success and survival past the early life-history.  Survival through the first winter is dependent on body size.  Individuals with pre-winter body sizes of smaller than approximately 10 to 11 cm fork length by the fall are less likely to survive.
• Based on presence of eggs, larvae, and ripe and running adult males and females, the tidal portion of the Stewiacke River lying 0 km to 6 km upstream of the confluence with the tidal Shubenacadie River is the only extant spawning site known to be used annually by the BoF Striped Bass DU.
• Genetic data acquired since the 2006 RPA supports the presence of a spawning population in the Saint John River; however, there has been no documented spawning activity in more than 30 years.
• Viable spawning by Striped Bass has not been observed in the Annapolis River since 1976.  Although eggs have been collected from the river as late as 1990, survival beyond the egg stage is, therefore, thought to be very low to negligible.
• Age 1+ year and Age 2+ years juvenile Striped Bass possessing the genetic traits of the Shubenacadie River population have been detected within the Saint John River, indicating that the range of the Shubenacadie River population includes a large portion of the coastal and estuarial areas of the BoF.
• Most Age 0+ year Shubenacadie River Striped Bass appear to over-winter in tidal brackish water, although the specific over-wintering sites are not known.
• There are no life stages of Striped Bass that are thought to use a dwelling-place that meets the criteria for being declared a residence, as described in the Species at Risk Act and DFO draft guidelines.
• Due to the insufficient historical and present abundance data, it is not possible to establish abundance targets for either the BoF DU or the individual river populations at this time. However, there is no indication of a continued loss of spawning populations from within the DU and, therefore, of a further decline in general status.
• The primary threats facing the extant spawning population in the Shubenacadie River system are direct mortality through directed recreational angling and Food, Social and Ceremonial fisheries and, to a lesser extent, illegal fishing (poaching) and bycatch in commercial fisheries.
• There is an association between the decline in the Annapolis River Striped Bass population, the construction of the Annapolis Royal Causeway in 1960, and the subsequent construction of the Annapolis Tidal Station starting in 1980. The headpond is located downstream of the known spawning site on the Annapolis River and its alteration has had direct impacts on the quality of and access to this habitat.
• A reduced status for native Saint John River Striped Bass has been attributed to habitat degradation and loss, although direct cause-effect evidence for this specific population has not been gathered. Construction of the large Mactaquac hydroelectric dam upstream of a suspected important historical spawning ground is believed to be the single greatest factor contributing to the decline in the native population. The construction of the dam in 1967 may have significantly modified the spawning, egg incubation or larval habitats of the Saint John River population.

This Science Advisory Report is from the February 10-11, 2014, Recovery Potential Assessment for Striped Bass (Morone saxatilis, Bay of Fundy Designatable Unit.  Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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