Difference in the Seawater Tolerance of Anadromous and Landlocked Populations of Arctic Char (Salvelinus alpinus)

The seawater tolerance of juvenile fish from an anadromous and a landlocked population of Arctic char (Salvelinus alpinus), reared in freshwater under a constant light regime, was compared by making repeated seawater challenge tests from one summer to the next. Fish from the landlocked population had higher mortality rates and higher blood plasma Na+ concentrations after transfer to seawater than those from the anadromous population. The gill Na-K-ATPase activity of the landlocked fish was lower than that of the anadromous fish. For both populations, the smallest fish showed the lowest seawater tolerance, but hypoosmoregulatory ability was independent of fish size for fish larger than about 60 g. By June of the second summer, fish from the anadromous, but not those from the landlocked population, developed seawater tolerance 10 d after transfer to seawater. This increase in hypoosmoregulatory ability was accompanied by a doubling of the gill Na-K-ATPase activity.

Download Full-text

Annual Variations in Rheotactic Behaviour and Seawater Adaptability in Landlocked Arctic Char (Salvelinus alpinus)

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f92-052 ◽

1992 ◽

Vol 49 (3) ◽

pp. 448-452 ◽

Cited By ~ 21

Author(s):

Monika Schmitz

Keyword(s):

Seasonal Changes ◽

Salvelinus Alpinus ◽

Challenge Test ◽

Early Summer ◽

Rapid Decrease ◽

Arctic Char ◽

Migratory Behaviour ◽

Annual Variations ◽

Seawater Tolerance ◽

Seawater Challenge

The existence of basic smoltification characteristics, measured by means of seasonal changes in rheotactic behaviour and seawater adaptability, was studied from February to November in 1- and 2-yr-old landlocked Arctic char (Salvelinus alpinus). Up- and downstream directed movements were monitored in an annular stream tank at a water velocity of 0.2 m/s. A 48-h seawater challenge test using 25‰ seawater was performed at monthly intervals throughout the year to assess seawater adaptability. The 1-yr-old char displayed mainly nondirectional behaviour during spring, but from August onwards the movements were predominantly against the current. Seawater performance improved slightly in this group in May and June. The 2-yr-old char progressively developed a downstream behaviour and exhibited an increased seawater adaptability during spring and early summer. In late August, a marked reversal in rheotactic behaviour occurred, followed by a rapid decrease in seawater tolerance. The results demonstrate that seasonal changes in seawater adaptability and changes in migratory behaviour which were directionally consistent with smolting still exist in a population of Arctic char that has been landlocked for about 6000 yr.

Download Full-text

Development of Hypoosmoregulatory Capacity in Arctic char (Salvelinus alpinus) Reared under either Continuous Light or Natural Photoperiod

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f92-027 ◽

1992 ◽

Vol 49 (2) ◽

pp. 229-237 ◽

Cited By ~ 47

Author(s):

Arne M. Arnesen ◽

Morten Halvorsen ◽

Kjell J. Nilssen

Keyword(s):

Water Content ◽

Salvelinus Alpinus ◽

Plasma Osmolality ◽

Continuous Light ◽

Arctic Char ◽

Direct Transfer ◽

Seawater Tolerance ◽

Natural Photoperiod ◽

Muscle Water Content ◽

Muscle Water

Two groups of Arctic char (Salvelinus alpinus) were reared in freshwater (5–6 °C) under either continuous light (LDL) from first feeding (March) or LDL until July and then natural photoperiod (NDL, 70°N). Direct transfer to seawater (5.5 °C, 35 ppt) in February resulted in both groups exhibiting increases in blood plasma osmolality, Na+, and Mg2+ concentrations and a significant decrease in muscle water content. When tested in May, an improvement in seawater tolerance was evident in both groups. In June, only the NDL fish showed further improvements in hypoosmoregulatory capacity, since they exhibited only minor fluctuations in plasma constituents and muscle water content following direct transfer to seawater. Increased body size could partially explain the improved seawater tolerance in the experimental groups. Acclimation to brackish water prior to transfer to 35 ppt seawater in June improved seawater tolerance only in fish reared under continuous light. The results indicate that the seasonal increase in photoperiod stimulates the development of hypoosmoregulatory capacity whilst the fish are still resident in freshwater.

Download Full-text

The cost of anadromy: marine and freshwater mortality rates in anadromous Arctic char and brown trout in the Arctic region of Norway

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2018-0428 ◽

2019 ◽

Vol 76 (12) ◽

pp. 2408-2417 ◽

Cited By ~ 2

Author(s):

Arne Johan Jensen ◽

Bengt Finstad ◽

Peder Fiske

Keyword(s):

Fresh Water ◽

Brown Trout ◽

Salmo Trutta ◽

Reproductive Output ◽

Energy Use ◽

Salvelinus Alpinus ◽

Arctic Region ◽

Mortality Rates ◽

Arctic Char ◽

The Arctic

It is hypothesized that in diadromous fish, migrations may occur because of differences in the availability of food in marine and freshwater habitats. The benefits of migration to sea may be increased growth opportunities and reproductive output, while the costs may be increased mortality and increased energy use. Here we examine mortality rates of anadromous Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta) in fresh water and at sea over a 25-year period to test these hypotheses. Daily mortality rates were 5–15 times higher at sea than in fresh water, with highest rates for first-time migrants, inferring a clear trade-off between increased mass gain and mortality risk during the sea migration. Descending smolts were caught in a trap at the outlet of the river, individually tagged, and thereafter recorded each time they passed through the trap on their annual migration between the river and the sea. Brown trout females seemed to benefit to a higher degree from migrating to sea than did female Arctic char, probably because of the higher growth rate at sea, and hence higher reproductive output.

Download Full-text

Summer osmoregulatory capacity of the world's northernmost living salmonid

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1997.272.3.r743 ◽

1997 ◽

Vol 272 (3) ◽

pp. R743-R749 ◽

Cited By ~ 5

Author(s):

K. J. Nilssen ◽

O. A. Gulseth ◽

M. Iversen ◽

R. Kjol

Keyword(s):

Salvelinus Alpinus ◽

Arctic Charr ◽

Challenge Test ◽

Plasma Osmolality ◽

High Arctic ◽

Svalbard Archipelago ◽

Anadromous Arctic Charr ◽

Osmoregulatory Capacity ◽

Seawater Tolerance ◽

Seawater Challenge

Anadromous Arctic charr (Salvelinus alpinus L.) were caught on their way to and from the sea with the use of a fish trap placed in the Dieset watercourse located on the Spitsbergen Island (79 degrees 10' Northern latitude) within the high-Arctic Svalbard archipelago. When subjected to a seawater challenge test (34 parts/thousand at 4-5 degrees C), charr on their way to the sea showed only minor and temporary changes in blood plasma osmolality and Na+ and Mg2+ concentrations. The seawater tests also revealed good hypoosmoregulatory capacity for Arctic charr returning from the marine environment 4 wk later. A progressive decrease in seawater tolerance was first documented 7-11 days after their return to the freshwater habitat. Thus the Svalbard charr, being the northernmost anadromous salmonid and probably a direct descendant from the first Salvelinus immigrants to freshwater systems, undergoes a preparatory increase of hypoosmoregulatory capacity (smoltification) before entering the oceanic water bodies. Furthermore, the termination of their short annual seawater stay is probably elicited by factors controlling body systems other than osmoregulation.

Download Full-text