Terms of Reference

Lake Utopia Rainbow Smelt, Large-bodied Population (LURS-LbP) Population Abundance and Allowable Harm Estimate

Regional Science Response Process – Maritimes Region

November 19, 2019
Dartmouth, Nova Scotia

Chairperson: Tara McIntyre

Context

Lake Utopia is part of the Magaguadavic River watershed in southwestern New Brunswick. Lake Utopia Rainbow Smelt (LURS) 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 form (SbP) and a large-bodied form (LbP). Lake Utopia Rainbow Smelt (LURS-LbP) was designated as Threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in November 2008. The rationale for the designation was the “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” (see: COSEWIC 2008). A Recovery Potential Assessment (RPA) for Lake Utopia Rainbow Smelt (Osmerus mordax) (both SbP and LbP) was undertaken in 2010 (DFO 2011). A Recovery Strategy for the LURS-SbP (sympatric with the LURS-LbP) was published in 2016 (DFO 2016a). The Recovery Strategy adopts the interim recovery abundance target for LURS-LbP recommended in the RPA. LURS-LbP was re-assessed as Endangered by COSEWIC in 2018 and listed as Threatened under the Species at Risk Act (SARA) in August 2019.  A Science Response was completed in 2017 (DFO 2018) to estimate the population abundance for LURS-LbP based on sampling conducted in 2014 and 2017 and to provide advice on an appropriate population objective as well as advice on the likelihood that the population objective can be achieved under current levels of mortality. However, the estimated abundances for the 2014 and 2017 spawning run estimates were uncertain as genetic analyses of the 2014 spawning run indicated a mismatch between assigned genotype and the minimum fork length used to differentiate LbP from SbP spawners.

Since that time, genetic analysis of the 2017 and 2018 LURS-LbP spawning runs as well as tissue sampling of SbP spawners in 2017 and 2018 has produced relevant information for proposing a  revised minimum fork length criterion that corresponds to genetic differences between the two body forms. The intent of this meeting is to recommend an updated minimum fork length criterion, update the 2017 LURS-LbP abundance estimate, and discuss implications for the recommended recovery target for LURS-LbP on the level of mortality the species can sustain without jeopardizing its survival or recovery.

Objective

• Provide an updated population abundance estimate for LURS-LbP based on sampling conducted in 2014 and 2017 and on genetic analysis of these samples.
• Recommend an updated minimum fork length criterion for distinguishing LURS-LbP from LURS-SbP based on the new genetic analysis.
• Discuss how the genetic analyses and updated abundance estimates affect the  likelihood that the updated abundance objective for LURS-LbP can be achieved under current levels of mortality.

Expected Publications

• Science Response

Expected Participation

• DFO Science
• DFO Ecosystem Management

References

COSEWIC 2008. COSEWIC Assessment and Update Status Report on the Rainbow Smelt, Lake Utopia Large-bodied Population and Small-bodied Population Osmerus mordax in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 28 pp.

DFO. 2011. Recovery Potential Assessment for Lake Utopia Rainbow Smelt (Osmerus mordax) Designatable Units. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2011/004.

DFO. 2016a. Recovery Strategy for the Lake Utopia Rainbow Smelt (Osmerus mordax), Small-bodied Population (sympatric with the Large-bodied Population), in Canada. Species at Risk Act Recovery Strategy Series. Fisheries and Oceans Canada. Ottawa viii + 57 pp.

DFO. 2016b. Estimating Lake Utopia Rainbow Smelt (Osmerus mordax) Spawner Abundance and Allowable Harm. DFO Can. Sci. Advis. Sec. Sci. Resp. 2016/024.

DFO. 2018. Updated Estimate of Lake Utopia Rainbow Smelt (Osmerus mordax), Large-bodied Population, Spawner Abundance and Allowable Harm. DFO Can. Sci. Advis. Sec. Sci. Resp. 2018/019.