Science Advisory Report 2020/038

Stock Assessment of Newfoundland and Labrador Atlantic Salmon in 2018

Summary

• Twenty-two populations of Atlantic Salmon were monitored in 2018, 20 using counting fences and fishways and two by snorkel surveys.
  • Of the 22 rivers monitored in 2018, 21 were included in the stock assessment; four in Labrador and 17 in Newfoundland. Northwest River-Port Blandford was not assessed in 2018 since the count was incomplete. Four of the 21 assessed rivers in Newfoundland also counted juvenile salmon (smolt) migrating to sea (Figure 1).
• In 2018, five assessed rivers showed declines in total returns, and three of these had declines of greater than 30% compared to their previous generation mean (2012-17 and 2013-17 for Labrador and Newfoundland, respectively). Seven rivers had declines in total returns compared to the generation mean prior to 2016 (2010-15 for Labrador and 2011-15 for Newfoundland), four of which were greater than 30%. Data were unavailable during the previous generation and the generation prior to 2016 for six rivers (Table 3).
• Of the 15 assessed rivers for which there is information on returns over the previous three generations (2000-17 and 2003-17 for Labrador and Newfoundland, respectively), total returns in 2018 were lower on one of four rivers in Labrador and on five of eleven rivers in Newfoundland. Of these, four Newfoundland rivers had declines greater than 30% (Table 3).
• In 2018, estimated spawning escapements (eggs) were below the river-specific Limit Reference Point (LRP) (critical zone) on two of the four assessed rivers in Labrador. Estimated spawning escapement exceeded the river-specific Upper Stock Reference Point (USR) (healthy zone) on English River and fell between the LRP and USR (cautious zone) on Muddy Bay Brook.
• In Newfoundland, estimated spawning escapements (eggs) were below the LRP (critical zone) for eight of the 17 assessed rivers in 2018. Of the remaining nine Newfoundland rivers, seven rivers exceeded the USR (healthy zone) and two fell between the LRP and USR (cautious zone).
• The Labrador Indigenous and subsistence fisheries harvest in 2018, inferred from logbook returns (73% return rate), was 12,930 salmon (8,793 small, 4,137 large), which was 5.5% less than the previous six-year mean (2012-17) of 13,496 salmon (8,255 small, 5,241 large).
• Estimates of recreational catches for NL have been highly variable since 2005 (total catch range of 38,900 to 76,100 salmon). Preliminary estimates of retained and released salmon in 2018 were 13,626 and 25,055 (38,681 total).
• Returns of Atlantic Salmon to rivers on the south coast of Newfoundland (Salmon Fishing Areas [SFAs] 9-11) remain poor. Record low returns occurred at Conne River and Little River (>30 years for each river). All three monitored rivers in SFA 11 remain in the critical zone and marine survival rates also remain low (less than 3%).
• Marine survival continues to be the major factor limiting the abundance of Atlantic Salmon in the NL region. Returns in any given year are determined primarily by marine survival rather than variations in smolt production. Inter-annual estimates of marine survival continue to fluctuate, with survival in 2018 ranging between 0.8% and 9.3% for the five monitored rivers where marine survival estimates were available. The 2018 marine survival estimate for Conne River in SFA 11 (0.8%) is a record low in a 32 year time series.

Genetics

• Genetic analysis of mixed stock Atlantic Salmon fisheries in coastal Labrador (2017-18), West Greenland (2017-18) and St. Pierre et Miquelon (2015, 2017-18) revealed significant differences in stock composition, with Labrador exploiting 98-99% Labrador-origin salmon. The other two fisheries exploited mixtures of North American migratory stocks. In West Greenland, there was also a significant contribution from United Kingdom and Iceland stocks.
• Research on the distribution and abundance of Atlantic Salmon from marine aquaculture cages and hybridization with wild salmon continued in 2018.
  • Five escapees were recaptured at the Garnish River counting fence during regular monitoring activities. Additionally, 400 escapees were recaptured in the marine environment following an escape event of 2,000-3,000 farmed salmon in late-July, 2018.
  • Examination of the relative survival of wild, hybrid, and feral juveniles in the wild suggests decreased survival of aquaculture salmon offspring and simulation modeling suggests negative impacts on the character and size of wild populations experiencing hybridization.

Catch-and-Release Mortality

• Consistent with published findings, results from a catch-and-release mortality model indicate that the probability of mortality for a caught and released Atlantic Salmon increases significantly with increasing water temperature.

Environment

• Mean annual air temperature in Newfoundland and southern Labrador in 2018 was near the long-term average (1981-2010) characterized by a warm winter and summer, and a cold spring. Summer sea surface temperatures were colder than the long-term average in offshore regions, a trend observed since 2015. Driven by the warm summer, the water temperature in the inshore regions of Newfoundland (e.g., Comfort Cove) were above the long-term average in summer 2018.
• Since 2015, primary and secondary production indices in the NL Shelf show overall low productivity at the lower trophic levels (phytoplankton and zooplankton) and changes in zooplankton community structure with potential impacts on energy transfer to higher trophic levels including Atlantic Salmon.

River Temperatures

• Summer river temperatures fluctuate throughout the day and vary considerably by geographic location in NL, with some rivers experiencing changes in excess of 5°C.
• Average water temperatures in July and August for nine monitored rivers in Newfoundland from 1960-2016 showed a significant increase over time.
• Average water temperatures in July for four monitored rivers in Labrador showed no significant change over time, whereas water temperatures in August showed a slight increase.

River Closure Trends in Newfoundland

• The number of river closures due to environmental conditions (high water temperature and/or low water level) across all SFAs in Newfoundland during 2018 was the highest on record (131 rivers closed) while the percentage of angling days closed in 2017 and 2018 were the highest since 1987.

This Science Advisory Report is from the March 5 to March 7, 2019 Regional Peer Review Process on the Assessment of Atlantic Salmon in Newfoundland and Labrador. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Scheduleas they become available.

Science Advisory Report 2020/038 (PDF, 1,195 KB)

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