Research Document - 1999/109
Follow-up to the assessment of Atlantic salmon in the Saint John River drainage, N.B., 1998.
By T.L. Marshall, R. Jones, and L. Anderson
Abstract
This document is a sequel to that of previously more detailed assessments (Marshall et al. MS 1997; MS 1998) and a companion document to Marshall et al. (MS 1999). New in this document are assessments of adult returns to the Hammond River and spring smolts from the Nashwaak River in 1998.
Estimated returns in 1998 to the Mactaquac Dam, Saint John River, numbered 4,982 1SW and 971 MSW fish; wild 1SW returns were the second lowest in 29 years and wild MSW returns were the lowest of record. Return rates for one-year (hatchery) smolts were 0.75 for 1SW salmon (up from that of 1997) and 0.08 for MSW salmon, the lowest of record. Spawners numbered 4,622 1SW and 627 MSW, 94 and 13%, respectively, of the fish requirement above Mactaquac. Egg deposition was only 18% of the egg requirement, down by approximately 60% from that in 1997. Eggs from hatchery-origin fish potentially contributed to 76% of the total deposition; the conservation requirement has not been met since 1985.
A mark-and-recapture experiment on the Hammond River in 1998 estimated total river returns to be 196 1SW and 164 MSW salmon, 20.6% and 17.5%, respectively, being of hatchery origin. Escapement was estimated to be 28% and 29%, respectively, of the interim fish conservation requirements and 33% of egg requirements. Redd counts suggested that conservation requirements were approached in a 11.75 km section of main river where they have been met in all but two of the 18 years of redd counts. Densities of juvenile salmon were the third highest of the 18-year data set but still below 'normal' parr abundance.
A mark-and-recapture experiment on the Nashwaak River suggested that the most probably number of spring smolt originating above the adult counting fence site in 1998 was 22,750 fish (17,900 - 32,850). There was no assessment of the numbers of pre-smolts that may have left the system the previous October and November.
Forecasts of returns to the Mactaquac Dam in 1999 suggest a <1% probability that 1SW and MSW returns will meet the conservation egg requirements. Forecasts of returns to the Hammond River were not possible but most indices of stock status suggest that returns in 1999 will be low with respect to conservation requirements.
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