Spawning success in Atlantic salmon (Salmo salar L.): a long‐term DNA profiling‐based study conducted in a natural stream

Abstract

Spawning success of Atlantic salmon (Salmo salar L.) was investigated, under near-natural conditions, in the Girnock Burn, an 8-km long tributary of the River Dee in Scotland. Employing minisatellite-based DNA profiling, mating outcomes were resolved over three spawning seasons by assigning parentage to progeny samples removed from spawning nests ('redds'). While individual spawning patterns differed markedly, consistent trends were present over the 3 years studied. Multiple spawning was found to be prevalent. More than 50% of anadromous spawners of both sexes contributed to more than one redd. Up to six redds for a single female and seven for a single male were detected. Both sexes ranged extensively. Distance between redds involving the same parent varied from a few metres to > 5 km. Distances > 1 km were common. Both males and females ranged to a similar extent. Range limit was not correlated to fish size. Pairs were not monogamous, both males and females mating with different partners at different sites. Size assortative mating was apparent among 1991 spawners but was not detected for 1992 or 1995. Redd superimposition was found to be common (17-22% of redds over the 3 years), although it was not correlated to the number of anadromous spawners present. High levels of nonanadromous mature parr mating success (40-50% of total progeny sampled) were recorded, and these likely contribute greatly to the effective population size. The relevance of these findings at the individual and population level is discussed, with particular reference to management implications.

Age Structure, Changing Demography and Effective Population Size in Atlantic Salmon (Salmo salar)

“…Nevertheless, the reasoning implies that parr reproductive contribution increases N e by reducing the variance in (male) individual reproductive success. Empirical investigations have often applied theory for discrete generations, through the influence of mature parr on sex bias (e.g., L'Abée-Lund 1989; Consuegra et al 2005) or individual reproductive success in a single breeding season (e.g., Martinez et al 2000;Taggart et al 2001). Both approaches may not correctly reflect processes in agestructured populations with overlapping generations.…”

“…We attempted to account for the influence of male parr maturation on age-specific reproductive contribution of males as follows. In the absence of data for the rivers, we used empirical values from observations under natural ( Jordan and Youngson 1992;Martinez et al 2000;Garant et al 2001;Taggart et al 2001) and experimental conditions (Hutchings and Myers 1988;Moran et al 1996;Thomaz et al 1997;Garcia-Vazquez et al 2001;Hutchings 2001, 2002). These studies suggest that mature male parr account for $30% of the fertilizations in direct competition with anadromous fish, over a wide range of operational sex ratios.…”

Addition of spawning gravel—a means to restore spawning habitat of atlantic salmon (Salmo salar L.), and Anadromous and resident brown trout (Salmo trutta L.) in regulated rivers

“…the portion of eggs resulting from one spawning act also called an egg pocket) or several nests spawned in successive pits (Ottaway et al, 1981;Crisp and Carling, 1989). Normally the female will spread her offspring in several redds within the river (Webb and Hawkins, 1989;Baglinière et al, 1990;Barlaup et al, 1994;Garant et al, 2001;Taggart et al, 2001).…”

Behaviour and survival of wild Atlantic salmon Salmo salar captured and released while surveillance angling for escaped farmed salmon

“…Salmon that are holding position prior to spawning are likely maintaining a position near their eventual spawning site and not necessarily on it (Økland et al 2001(Økland et al , Richard et al 2014. Movement away from holding pools therefore does not necessarily suggest a loss of territory, especially given that individuals move among pools during the spawning season (Taggart et al 2001), and a comparison to the movement exhibited by salmon in 2014 indicated no major differences in displacement.…”