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Research Document - 2006/025

Assessments of Atlantic salmon stocks in southern and western New Brunswick (SFA 23), an update to 2005

By Jones, R.A., L. Anderson, J.J. Flanagan and T. Goff

Abstract

Total one-sea-winter (1SW) (1,159) and multi-sea-winter (MSW) (350) returns destined for upriver of Mactaquac Dam on the Saint John River in 2005 were both the lowest on record since 1970. Wild origin fish comprised 74% of 1SW and 73% of MSW fish. Return rates for hatchery-released smolts were 0.38% (1SW) and 0.05% (2SW), an increase of 18% and a decrease of 54%, respectively, from the values in 2004. Spawners numbered 1,060 1SW and 273 MSW salmon, 22% and 6% of the respective requirements. The egg deposition estimate (80% from wild fish) was 6% of the requirement, the lowest value on record. An additional 5.2 million eggs (or 18% of requirement) were potentially deposited from captive-reared spawners in 2005.

Counts at the Nashwaak River fence resulted in a return of 731 1SW and 162 MSW salmon. Return rates for wild smolts to 1SW and 2SW fish in 2005 were 5.13% and 1.58%, a decrease of 20% and an increase of 25% from the previous year. Spawners represented 35% and 8% of the respective 1SW and MSW conservation requirements. An egg deposition of 16% of the requirement was similar to the previous year and slightly better than the five-year mean.

Counts of wild, hatchery and aquaculture origin salmon from fishways operated on the Magaguadavic and St. Croix rivers were 72 and 39 fish, respectively. Including the post smolts, ninety-six or 86% of the combined counts were deemed of aquaculture origin and denied access to both rivers. On the Magaguadavic River, five wild and four hatchery 1SW wild salmon were released upstream of the fishway which resulted in an estimated egg deposition of less than about 2% of the requirement. All hatchery salmon, two 1SW and four MSW fish, ascending the St. Croix River at Milltown were retained for broodstock purposes.

Total estimated returns and escapement of 1SW and MSW salmon to the Big Salmon River based on diver observations were 60 fish. The sixty fish represented less than 10% of the requirement and were three times greater than the returns the previous year.

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 2006 are 1,600 1SW (90% C.I.; 820 - 2,360) and 680 MSW (90% C.I.; 160 – 1,250) 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 both freshwater and marine survival, it is very unlikely that returns will be much greater than 2,000 fish in 2006.

Based on the five year average, 440 1SW (90% C.I.; 120 - 780) and 170 MSW (90% C.I.; 50 - 290) salmon are predicted to return to the Nashwaak River in 2006. Using the range (minimum and maximum) of smolt-to-1SW return rates observed since 1999 to the 2005 wild smolt estimate, the predicted 1SW returns to the Nashwaak in 2006 would be between 80 and 330 fish. Similarly, the predicted 2SW salmon return in 2006, from the 2004 smolt class, ranges from 40 to 210 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, St. Croix and Big Salmon rivers in 2006 are projected to be similar to the few fish that returned in 2005. There is a zero probability of attaining the conservation requirement in 2006.

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