Research Document - 2014/008
Assessment of the Recovery Potential for the Outer Bay of Fundy Population of Atlantic Salmon (Salmo salar): Status, Trends, Distribution, Life History Characteristics and Recovery Targets
By R.A. Jones, L. Anderson, and C.N. Clarke
Abstract
As a part of the Recovery Potential Assessment process that was triggered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) designation of Outer Bay of Fundy (OBoF) Atlantic Salmon population as ‘endangered’ in 2010, this document updates the status, trends and life history information that were last provided in Jones et al. (2010) for the COSEWIC (2010) review. New information related to the current range, distribution and densities of wild origin juvenile salmon from an extensive electrofishing survey completed in 2009, and the abundance and distribution recovery targets for Designatable Unit (DU) 16 are also presented.
Adult salmon counts and estimates of returns to counting facilities (e.g., fishway, counting fence) and subsequent spawners are evaluated against conservation egg requirements that were determined for each index river based on accessible habitat area and the biological characteristic information of the returning adult salmon. Estimates of emigrating juvenile salmon (i.e., pre-smolt, smolt) using rotary screw traps, as well as mean parr densities by electrofishing on two tributaries of the Saint John River are assessed against reference levels.
Overall, the available data on salmon in DU 16 indicates that populations are persisting at low abundance levels. The One-Sea-Winter (1SW) and Multi-Sea-Winter (MSW) returns to counting facilities were the lowest on record in 2012, and, as a result, the wild smolt to 1SW and 2SW salmon return rates were both less than 0.4% on the Nashwaak River. In the past five years, estimated adult abundance on the Saint John River (SJR) upriver of Mactaquac and on the Nashwaak River has averaged about 7% (2-13%) and 22% (3-37%) of their respective conservation egg requirements. The estimated egg deposition upriver of Mactaquac has declined at rates in excess of 80% over the last 15 years, while Nashwaak egg deposition has also declined but to a lesser degree (27-50%) over the same time period depending on the model. Pre-smolt and smolt estimates contributing to the 2012 smolt class for the Tobique River were the highest since monitoring commenced in 2001, and the minimum smolt abundance estimate on the Nashwaak River was higher than 2011 but below the previous 5-year mean. These annual smolt production estimates for both rivers have been less than 0.6 smolts per 100 m² of productive habitat which is low in comparison to the reference value of 3.8 smolts per 100 m² (Symons 1979). Juvenile densities in the Tobique and Nashwaak rivers were considerably below reference values (Elson’s norm) in 2012. Adult returns to other monitored rivers within the DU were extremely low, with decline rates in excess of 80% over the last 15 years for the Magaguadavic River. Decline rates were about 65% when considering total escapement of 1SW and MSW returning adults to DU 16 over the last 15 years. Electrofishing surveys at 189 sites within most of the rivers or tributaries within the DU revealed that juveniles are still present in most of the drainages but at low densities. The systems with the highest mean densities were all tributaries of the SJR, which included the Shikatehawk, Little Presquile, Keswick, Nashwaak, Canaan and Hammond systems.
The proposed recovery target for salmon of the OBoF DU has both an abundance and distribution component. The short-term distribution target was based on seven criteria designed to maintain genotypic, phenotypic, and geographic representation of the DU while offering the best opportunity for recovery. The short-term distribution target is to support the persistence of salmon in the seven priority rivers. Abundance targets are set using the conservation egg requirement of 2.4 eggs per m² of productive habitat. The short-term abundance target for the OBoF DU is to annually achieve the conservation egg requirement in all the seven priority rivers selected for distribution targets. Combined, short-term target rivers represent 56% of the salmon habitat in the OBoF region. This target translates to approximately 54.4 million eggs, which could be produced by 23,500 adult salmon within the 22.62 million m² of productive habitat area. The long-term abundance target is 97 million eggs in the currently accessible 40.46 million m² of productive habitat area. This egg deposition could be produced by 41,200 adult salmon.
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