River- and Sex-Specific Annual Survival Rates of Mature Anadromous Alewife (Alosa pseudoharengus)

During multiple annual spawning runs from 2013 to 2021, over 9,000 mature anadromous alewife (Alosa pseudoharengus A. Wilson, 1811) were monitored with passive integrated transponders (PITs) in four rivers of the Chignecto Isthmus, Bay Fundy, Canada. A subsample 384 individuals tagged during 2016–2019 aged 3 6 years (mean ± SD; 4.2 0.7 years, n = 232, males; 4.5 152, females). Biotelemetry revealed that one unsexed individual survived seven post tagging, possibly making it 10–13 old. Return rates varied among rivers, lowest most anthropogenically impacted river. and ageing data used estimate apparent survival ranging 0.25 0.50 depending on river year. Based capture-mark-recapture (CMR) analysis biotelemetry three less estimated overall was 0.396, total instantaneous mortality (Z) 0.93, future life expectancy time release 1.08 years. Frequency distribution ages 4–6 for pooled all study a lower rate 0.301, Z 1.20, 0.83 The detection 0.89–0.98 but year, 2017-2018 related malfunctioning tide gate preventing upstream fish passage subsequent detection. CMR, males had higher compared females, which translated into an mean increase 0.05. Alewife survivorship our highlighted limited ecosystem-based management period is required mitigate connectivity issues avoid loss population cohorts decrease risk extirpation.