Science Advisory Report  2013/022

Recovery Potential Assessment for Atlantic Sturgeon (Maritimes Designatable Unit)

Summary

• Estimates of Atlantic Sturgeon spawner abundance in the Saint John River indicate low to modest population abundance, in the range of 1,000 to 3,000 spawners per year. 
• A potential medium-term recovery target could be, at a minimum, to maintain the current annual spawner abundance in the lower Saint John River of approximately 1,000-3,000 spawners, while supporting a population with a broad body size and age distribution for both sexes.
• A potential distribution target would be that all life history stages should be found in the Saint John River, with interannual appearances of multiple age classes within known marine foraging areas (e.g. the Minas Basin).
• The lower Saint John River between Mactaquac and the Reversing Falls, including tributaries, is considered to be important habitat for the Maritimes Designatable Unit of Atlantic Sturgeon, as this bounds the only known spawning area in the Designatable Unit. Adults can begin to ascend the Saint John River as early as May, and spawning is thought to extend into late August.
• The Saint John River Estuary (below the Reversing Falls) is considered to be important habitat for the Maritimes Designatable Unit of Atlantic Sturgeon for its role as a migration route in and out of the Saint John River.
• Migrant, foraging juvenile (as young as 3 years), sub-adult and adult Atlantic Sturgeon are abundant in the Minas Basin during the summer months, and this is also considered to be important habitat for the Maritimes Designatable Unit of Atlantic Sturgeon. The Minas Passage is considered important habitat for the migration of Atlantic Sturgeon in and out of the Minas Basin.
• Current knowledge does not indicate any particular residence requirements, as defined by the Species at Risk Act and DFO guidance material, for Atlantic Sturgeon.
• The primary threat to the Maritimes Designatable Unit of Atlantic Sturgeon is the commercial fishery, which has been authorized since 2010 to remove 350 Atlantic Sturgeon (175 males and 175 females) per year. The recreational angling fishery has a release rate of approximately 98%, and survival of Atlantic Sturgeon that are released live is considered to be very high. There are currently two Aboriginal fishing licences for Atlantic Sturgeon, with very low reported landings (<5 per year).  Some Atlantic Sturgeon have been authorized by DFO to be caught and retained for aquaculture purposes (i.e., breeding). It is prohibited to retain Atlantic Sturgeon captured as bycatch in other fisheries, but rates of incidental capture and total mortality are not well known and may warrant assessment. The Annapolis Tidal Generating Station is known to be a source of mortality for Atlantic Sturgeon in the Bay of Fundy; however, the number of individuals reported to be killed each year is low with 11 mortalities recorded since 1985. The proportion of these that are from the Saint John River is not known. 
• There are a number of existing mitigation measures available to reduce the mortality of Atlantic Sturgeon in the Maritimes Designatable Unit. Additional measures could include: a maximum mesh size limit to increase escapement of larger bodied mature females, an extended seasonal closure to protect a greater proportion of the spawning biomass, an increase in the minimum size, mandatory reporting of Atlantic Sturgeon bycatch in other fisheries, verification of the bycatch rates reported, and a reduction in the allowable take of Atlantic Sturgeon from the Saint John River.  
• A population model for the Maritimes DU of Atlantic Sturgeon continues to be developed, and it is not possible to project future biomass with any certainty at the current time.  However, given the broad age composition of the adult population (Females: 16-44 years, Males: 17-39 years), and the large number of Saint John River juveniles and sub-adults that have been observed in the Minas Basin, it is expected that the population will continue to persist at approximately current levels in the short to medium term (5-10 years) and is not considered to be at risk of extinction within the next generation.

This Science Advisory Report is from the January 15-16, 2013, Recovery Potential Assessment for Atlantic Sturgeon (Maritimes DU). 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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