Development of osmotic and ionic regulation in two races of chinook salmon Oncorhynchus tshawytscha

Effects of size, age and photoperiod on hypoosmoregulation in brook trout, Salvelinus fontinalis

“…This is a common feature of salmonid osmoregulation (Parry, 1958;Conte and Wagner, 1965;Wagner et al, 1969). The size at which hi gh survi val in seawater is attai ned (under simil ar exposure conditons) is species dependent, and is near the size at which migration into seawater occurs ( …”

“…It follows that generic or species differences in seawater c survival also relate to differences in ion transport capability (Parry, 1958;ciarke et al, 1978). This concept is shown schemati cally in Fi g. 6, where 1 i ne A may represent si ze dependent osmoregualtion in a species of Salvelinus, line B Salmo, and (Wagner et al, 1969;Healy, 1980) (Conte et al, 1966;Healy,1980) Support for the rel ative shape of these 1 i nes (simil ar intercepts and decreasing slopes) is scarce. found that plasma osmolarity of Atlantic salmon (6-15 cm) after exposure to -32 ppt seawater was a decreasing function of size.…”

“…Al though several researchers have concl uded that si ze is the primary factor determining seawater suvival in salmonids (Huntsman and Hoar, 1939;Parry, 1958;Houston, 1961;Wagner et al, 1969;Wagner, 1974) and striped mullet, Mugil cephalus (Nordlie et al, 1982), few have attempted to, separate the effects of si ze and age. Conte and Wagner (1965) and Conte et ale (1966) determined that size, rather than age determi ned seawater survi val in rai nbow trout and coho salmon, although they did not manipulate growth rates to control for age.…”

“…There is a large body of evidence indicating that size dependent survival of a salmonid species, following exposure to seawater, is related to size dependent ion transport capabilities (Conte and Wagner, 1965;Conte et al, 1966;Wagner et al, 1969;; present study), and that a critical level ~f (Na+J, (Cl-J or total pl asma osmol ari ty determi nes survi val (Gordon, 1959;Jackson, 1981). It follows that generic or species differences in seawater c survival also relate to differences in ion transport capability (Parry, 1958;ciarke et al, 1978).…”

“…Increased size has been shown to be a determinant of hypoosmoregulatory ability in a variety of salmonids, acti ng di rectly to i nfl uence sal i ni ty tol erance (Huntsman and Hoar, 1939;El son, 1957;Parry, 1958;Houston, 1961;Wagner et al, 1969;Wagner, 1974) as well as the process of smoltification . Although size has been implicated as the primary effector of ontogenetic changes in osmoregulatory ability, few studies have attempted to separate the nonnally covarying properties of size and age.…”