Science Response 2018/019
Updated Estimate of Lake Utopia Rainbow Smelt (Osmerus mordax), Large-bodied Population, Spawner Abundance and Allowable Harm
Context
Lake Utopia is part of the Magaguadavic River watershed in southwestern New Brunswick. Lake Utopia Rainbow Smelt (LURS) (Osmerus mordax) represent one of the only three confirmed occurrences in Canada where genetically divergent smelt populations co-exist. Two populations of smelt co-exist in Lake Utopia; a Small-bodied Population (LURS-SbP) and a Large-bodied Population (LURS-LbP). Lake Utopia Rainbow Smelt (Large-bodied) Population was designated Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in November 2008. The rationale for the designation was “population is part of a genetically divergent sympatric pair of Osmerus that is endemic to a single lake in Canada with an extremely small index of area of occupancy (6 sq. km). It spawns in only three (3) small streams in the watershed and could quickly become extinct through degradation of spawning streams from increasing development around the lake shore and impacts of the dip-net fishery. This population is threatened by introduction of exotic species and by increasing eutrophication” (COSEWIC 2008). A Recovery Potential Assessment (RPA) for both LURS populations was undertaken in 2010 (DFO 2011).
The LURS-LbP is currently under consideration for listing as Threatened under the Species at Risk Act (SARA). Interim abundance and distribution objectives for LURS-LbP were proposed in the LURS RPA (DFO 2011) and adopted in the LURS-SbP Recovery Strategy (DFO 2016a). A Science Response Process (DFO 2016b) was undertaken in 2016 to estimate LURS-LbP abundance based on sampling conducted in 2014, update the interim population abundance target and provide advice on the likelihood that the population objective could be achieved under current levels of mortality. The results were inconclusive due to uncertainty about the genetic assignment of the smelt sampled and limitations associated with reliance on data from a single spawning season (DFO 2016b). Genetic analysis of the smelt sampled in 2014 has since produced relevant information that was not available at the time of the 2016 Science Response. Also, additional biological information and abundance estimates are available from a mark-recapture project conducted during the Mill Lake Stream LURS spawning run in 2017.
A Science Response Process was held on October 17, 2017, on Lake Utopia Rainbow Smelt, Large-bodied Population (LURS-LbP) Population Abundance and Allowable Harm (update to the 2016 Science Response), in Dartmouth, Nova Scotia. The intent of this meeting was to provide updated information on LURS-LbP abundance estimate, abundance target, and allowable harm, where available. The objectives were to:
- Provide a population abundance estimate for the LURS-LbP based on sampling conducted in 2014 and 2017 and on genetic analyses undertaken on the samples collected in 2014.
- Provide an updated recovery abundance target for the LURS-LbP to replace the interim recovery abundance target proposed in the Recovery Potential Assessment (DFO 2011).
- Provide the likelihood that the updated abundance objective for the LURS-LbP can be achieved under current levels of mortality.
- Provide the maximum level of allowable harm that the LURS-LbP can sustain without jeopardizing its survival or recovery.
This Science Response Report results from the Science Response Process of October 17, 2017, on the Lake Utopia Rainbow Smelt Large-bodied Population Abundance and Allowable Harm Estimate (update to 2016 Science Response).
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