Population Structure of Atlantic Salmon in Maine with Reference to Populations from Atlantic Canada

Abstract

Anadromous Atlantic salmon Salmo salar from 12 rivers in Maine, 3 rivers in New Brunswick, and 2 rivers each in Nova Scotia, Quebec, Newfoundland, and Labrador as well as 2 landlocked strains in Maine (N ϭ 3,863) were genotyped at 11 microsatellite loci. Fish in the drainages of Maine's Kennebec and Penobscot rivers were genetically similar to those sampled from the 8 rivers recently listed as containing an endangered distinct population segment under the United States' Endangered Species Act. Genetic distance estimates confirm that Maine's Atlantic salmon, both landlocked and anadromous, represent a discrete population unit, genetically as independent from any Canadian population as the Canadian populations are from each other. Within Maine, the anadromous and landlocked populations were statistically distinct. Anadromous Atlantic salmon were more genetically similar among year-classes within rivers than among rivers, as would be expected if the river is the unit of population. The effective number of breeders estimated within each river is larger than the number of adults estimated from samples and redd counts over the 10-year period from 1991 to 2000. subsistence and commercial fishery resource for both native North Americans and European settlers through the beginning of the industrial revolution. The Atlantic salmon was nearly extirpated from New England in the 19th century, when habitat loss resulting from dam construction and logging

Reduced Genetic Diversity and Effective Population Size in an Endangered Atlantic Salmon (Salmo Salar) Population from Maine, USA

“…Given that 95.6% of returning Dennys river salmon from 1947-1994 were 2-Sea-Winter individuals (Baum 1997), generation length (t) may be assumed to be roughly 4 years. However, parentage attributable to precocious male parr has been shown to have a strong effect on such estimates (Spidle et al 2003), and it has been suggested that precocious parr may compensate for decreased numbers of anadromous spawners (Martinez et al 2000). Although there is no a priori information about the proportion of successfully breeding precocious parr in this population, it is reasonable to assume that, if present, it would reduce the generation length.…”

“…Pooling temporally separated samples to increase sample sizes is standard practice when spawning events involve individuals of different ages Spidle et al 2001;Spidle et al 2003), and has been recommended for species with overlapping generations when populations are small and the potential effects of drift are large (Waples 1990). To increase the sample size of our $1975 sample, we pooled individual returning salmon obtained from 1974-1976.…”

“…Seven microsatellite loci, previously used to assess genetic variation in Maine Atlantic salmon populations Koljonen et al 2002;Spidle et al 2003) and currently used to assess Federally-maintained river-specific broodstocks, were screened: Ssa289 (McConnell et al 1995), Ssa85, Ssa171, Ssa197, Ssa202 (O'Reilly et al 1996, SSOSL311 (Slettan et al 1995), and SSOSL438 (Slettan et al 1996). Final concentrations of reagents in a 25 ll Polymerase Chain Reaction (PCR) cocktail were: $10 ng of genomic DNA, 1· PCR buffer pH 9.5 [10 mM KCl, 20 mM Tris-HCl pH 8.3, 10 mM (NH 4 ) 2 SO 4 ], 2.0 mM MgCl 2 , 200 lM each dNTP, 0.05-0.25 lM each primer (reverse primer 5'-labeled with fluorescent dye), and 0.75 units of Taq DNA polymerase.…”

“…Numerous studies have examined historic samples across multiple generations in Atlantic salmon populations to investigate temporal trends in genetic diversity and divergence Tessier and Bernatchez 1999;Sa¨isa¨et al 2003). Recent studies of genetic population structuring among Maine Atlantic salmon stocks have included investigation of temporal trends during the 1990's Spidle et al 2003), a time period post-dating significant declines of these runs. To obtain information on the relative persistence of the genetic composition for populations of conservation concern, researchers should, whenever possible, analyze contemporary and historical samples over long periods of time, particularly those spanning observed population decline.…”

Restoration and enhancement of Atlantic salmon populations: what we have learned from North Iberian rivers

“…The different areas of the river appear to contain distinct sub-populations (significant F ST values), with migration between them (M values) but exhibiting significant spatial population structuring, which is temporally stable and comprising at least two well differentiated units (upstream and downstream) and a mixture in the rest of the drainage. This differs somewhat with the suggestion of the existence of a metapopulation linking neighbouring rivers in this region proposed by Ayllon et al (2006) and Kuparinen et al (2010), revealing for the first time the occurrence of fine population structuring at the within river level in northern Spain, as has been described for Atlantic salmon at other latitudes (Ståhl, 1983;Heggberget et al, 1986;Verspoor and Jordan, 1989;Hurrell and Price, 1993;Garant et al, 2000;Spidle et al, 2003;Vähä et al, 2007;Primmer et al, 2006;Dillane et al, 2008). As already proposed by other authors (Garcia-Vazquez et al, 1991;Vespoor, 1997) stocking with foreign fish should be discarded as a method for restoration and enhancement of this Atlantic salmon population.…”