Research Document 2023/043
Information on Atlantic Salmon (Salmo salar) from Salmon Fishing Area 17 (Gulf Prince Edward Island) of relevance to the development of a 2nd COSEWIC status report
By Cairns, D.K., Roloson, S.D., MacFarlane, R.E., and Guignion, R.E.
Abstract
To support preparation of a forthcoming Committee on the Status of Endangered Wildlife in Canada (COSEWIC) review, this report assembles data on Atlantic Salmon (Salmo salar) biology, demographics, habitat, and threats for Prince Edward Island (PEI) (Salmon Fishing Area 17). Historical accounts indicate that the original PEI Atlantic Salmon population was dominated by late-run and large (≥ 63 cm) fish. These characteristics are retained in small rivers. At least 38,826,353 Atlantic Salmon have been stocked in PEI in 1880 - 2020, mostly in larger rivers. The proportion of early-run and small Salmon has been increased in larger rivers by the stocking of fish intended to increase summer angling opportunities. Sea ages of returning adults are generally one year for small Salmon and two years for large Salmon. Return rates for fish of hatchery origin range from 0.5 to 5.9%. Data on return rates of naturally spawned fish are unavailable. In the Morell River, PEI's traditionally most important Salmon river, mean fecundity is 3,143 eggs for small Salmon and 4,963 eggs for large Salmon. The egg phase (1 year), juvenile phase (mean 2.32 years), and sea phase (mean 1.77 years) sum to 5.09 years, which is the mean generation time of the population. The typical early life history pattern of PEI Atlantic Salmon occurs in rivers, with eggs hatching as fry, fry developing into parr, and parr turning into smolts which leave on marine migrations. However, some juvenile males mature precociously, and some parr occupy ponds and estuaries. The ancestral trait of late-run and large returnees is shared by Atlantic Salmon in southeast New Brunswick and northern Nova Scotia. Genetic data on Salmon in stocked rivers suggest an affinity with Salmon in a broad geographic area centred in the southern Gulf of St. Lawrence. However, genetic samples from two small rivers in northeastern PEI clustered with each other but did not show affinities with samples from elsewhere in Canada. Redd counts for the period 1990 - 2019 showed rising trends in four rivers and falling trends in five rivers. Redd counts for the period 2004 - 2019 showed rising trends in 13 rivers and falling trends in six rivers. Seventy-one PEI rivers are large enough that they probably supported Atlantic Salmon populations in pristine times. For 2000 - 2019, juvenile electrofishing and redd surveys detected Atlantic Salmon at least once in 40 rivers, but detected Atlantic Salmon in every monitored year in only 12 rivers. The spawning population of Atlantic Salmon on PEI is estimated at 717, based on redd counts. Sediment deposition on spawning and rearing habitat is a major threat to Atlantic Salmon on PEI. Additional threats include pesticide-related fish kills, water extraction for municipal and irrigation purposes, climate change leading to more frequent droughts and higher water temperatures, fish passage impairment by dams (including beaver Castor canadensis dams), and competition with non-native Rainbow Trout (Oncorhynchus mykiss).
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