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Research Document - 2004/019

Assessments of Atlantic salmon stocks in southwest New Brunswick, an update to 2003

By Jones, R.A., Anderson, L., Goff, T.

Abstract

Total one-sea-winter (1SW) (1,304) and multi-sea-winter (MSW) (752) returns destined for upstream of Mactaquac Dam on the Saint John River in 2003 were the second and third lowest, respectively, in 34 years of record. Hatchery-origin fish comprised 71% of 1SW and 68% of MSW fish with the MSW percentage being the highest on record. Return rates for hatchery-released smolts were 0.0034 (1SW) and 0.0015 (2SW), a decrease of 24% and an increase of 317%, respectively, from the values in 2002. Spawners numbered 1,136 1SW and 555 MSW salmon, 23% and 11% of the respective requirements. The egg deposition estimate (31% from wild fish) was 12% of the requirement, double the value estimated in 2002.

Counts at the Nashwaak River fence resulted in a return of 297 1SW and 113 MSW salmon. Return rates for wild smolts to 1SW and 2SW fish in 2003 were 0.0191 and 0.0090, a decrease of 39% and an increase of 385%, respectively, from the previous year. Spawners represented 14% and 5% of the respective 1SW and MSW conservation requirements. An egg deposition of 7% of the requirement was the second lowest since operation of the fence recommenced in 1993.

Fishway counts from the Magaguadavic and St. Croix rivers were 29 (including seven post smolts) and 24 salmon, respectively. Including the post smolts, thirty-two or 60% of the combined counts were deemed of aquaculture origin and denied access to both rivers. On the Magaguadavic River, 3 1SW and 3 MSW wild salmon were released upstream of the fishway which resulted in an estimated egg deposition of about 2% of the requirement. All hatchery salmon, 6 1SW and 9 MSW fish, ascending the St. Croix River at Milltown were retained for the hatchery program. For the sixth consecutive year no wild or hatchery returning salmon were released to spawn upriver of Milltown Dam.

Projected returns, based on the average returns of the previous five years, for populations originating upriver of Mactaquac Dam on the Saint John River in 2004 are 2,340 1SW (90% C.I.; 960 - 3,720) and 940 MSW (90% C.I.; 180 – 1,890) salmon. The probabilities of attaining the conservation requirement of 4,900 for both 1SW and MSW fish are near zero. Without a significant increase in marine survival, it is very unlikely that returns will provide even one-quarter of the conservation egg requirement in 2004.

Based on the five year average, 410 1SW (90% C.I.; 140 - 690) and 190 MSW (90% C.I.; 50 - 330) salmon are predicted to return to the Nashwaak River in 2004. Using the range (minimum and maximum) of smolt-to-1SW return rates observed since 1999 to the 2003 wild smolt estimate, the predicted 1SW returns to the Nashwaak in 2004 are more likely to be between 140 and 280 fish. Similarly, the predicted 2SW salmon return in 2004, from the 2002 smolt class, ranges from 40 to 130 fish. The probability of attaining the conservation requirement of 2,040 for both 1SW and MSW salmon is therefore near zero.

Wild and hatchery 1SW and MSW salmon returning to the Magaguadavic and St. Croix rivers in 2004 are projected to be no greater than the few fish that returned in 2003. There is a zero probability of attaining the conservation requirement in 2004.

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