Seawater Adaptation and Parr–Smolt Transformation of Juvenile Atlantic Salmon, Salmo salar

Abstract

Seawater adaptation of 1- and 2-yr-old Atlantic salmon, Salmo salar, presmolts and smolts was assessed during exposure to salinity increasing from 0.1 to 31‰ by examining changes in the osmotic concentration of their serum, urine, and intestinal fluid. Both age-classes adapted to seawater equally well; the marine osmoregulatory mechanisms apparently function before completion of parr–smolt transformation. Adaptation was possible during the parr stage for fish exceeding 12–13 cm fork length. The timing of transformation was synchronous for 1- and 2-yr-old juveniles as demonstrated by changes in their lipid and moisture content and condition factor (K). Condition factor of juveniles at the Mactaquac Hatchery, New Brunswick (45°58′N), decreased from February until the second half of May, while lipid content decreased from February until the second half of June. Migratory activity of juveniles at this location was maximal during the second half of May coincident with attainment of minimum K values and decreased during the first half of June as K values increased. While timing of changes in lipid and moisture content and K values were similar for juveniles at the Mersey Hatchery, Nova Scotia (44°10′N), lipid content of fish at the more southerly station decreased at a greater rate and migratory activity was apparent earlier. This was probably attributable to the advanced temperature cycle at that location. Smolt-release dates are discussed in terms of the development of the marine osmoregulatory mechanisms and the timing of parr–smolt transformation. Key words: Atlantic salmon, seawater adaptation, parr–smolt transformation, migration, hatchery management

Anadromy and residency in steelhead and rainbow trout (Oncorhynchus mykiss): a review of the processes and patterns

“…Earlier sampling may have revealed higher lipids in maturing males because a substantial proportion of lipids had to be metabolized for sexual development (Sargent et al 1989). This has been found for Atlantic salmon (Simpson 1992), though it is important to note that lipids are also metabolized when individuals undergo the smoltification process (Farmer et al 1978). Regardless, given that growth and size are not necessarily correlated with lipids Sutton et al 2000), studies that only consider measures of growth or body size may not fully elucidate how individual condition can influence life history patterns (Table 3; Sloat and Reeves 2014).…”

Impact of smolt production strategy on vertebral growth and mineralisation during smoltification and the early seawater phase in Atlantic salmon (Salmo salar, L.)

“…2006.08.008 adapted to a pelagic life in the sea (Folmar and Dickhoff, 1980;Hoar, 1988). This transformation involves down stream swimming (Lundqvist and Eriksson, 1985), de velopment of hypo-osmoregulatory ability (Johnston and Saunders, 1981;McCormick etal., 1987), silvering of the body (Johnston and Eales, 1967) and development of a more streamlined body (Farmer et al, 1978). In coho salmon (Oncorhynchus kisutch), the change in body shape during parr-smolt transformation is related to differential growth, primarily in the caudal part of the fish (Winans and Nishioka, 1987).…”

Increased winter temperature did not affect completion of smolting in Atlantic salmon

“…The increased winter temperature caused significant differences in growth between groups (Fig. 4), but all four groups exhibited a similar temporary decrease in condition factor in spring, characteristic of the completion of smolting (Farmer et al, 1978;Winans and Nishioka, 1987;Duston and Saunders, 1990).…”