Tolerance Levels of Cod (Gadus morhua) to Low Salinity

Journal of the Fisheries Research Board of Canada 04/2011; 23(9):1465-1467. DOI: 10.1139/f66-135
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    • "Although the Atlantic cod (Gadus morhua) is a benthopelagic marine species with high population sizes on the continental shelves in the North Atlantic, cod tends to prefer salinities lower than full-strength seawater if a choice is provided (Claireaux et al., 1995) and tolerates long-term exposure to low salinities (Odense et al., 1966). Furthermore, Atlantic cod has been found to grow faster at low (7‰) and intermediate salinities (14 and 15‰) compared with seawater (Dutil et al., 1997; Imsland et al., 2011; Lambert et al., 1994). "
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    ABSTRACT: The effects of salinity and temperature on growth, plasma ions, cortisol and immune parameters were inves-tigated in two experiments. In the first experiment small, medium and large juvenile Atlantic cod Gadus morhua (initial average weights of 1.9, 8 and 83 g, respectively) were reared at four constant salinities (6 to 32‰) for a short period (19–57 days, depending on size), then returned to seawater (32‰) without ac-climation and reared for another period (20–391 days). The highest growth rates were found at 10‰ in all size-classes. After the fish were returned to seawater the growth rates were inversely related to the salinity change in all size-classes and long-term rearing of the medium-sized fish revealed that abrupt salinity in-crease from 6 and 10‰ to seawater may permanently reduce the growth capacity of juvenile cod. In another long-term experiment, there was no significant difference in the growth rate of cod (initial average weight 3.4 g) reared at either 13.5 or 32‰ for 187 days. Rearing at 13.5‰ neither enhanced growth rate at 6.3 °C nor at 10 °C in larger juveniles (> 245 g) compared with rearing in seawater. The study shows that rearing salinity and abrupt salinity changes have limited or no effects on stress and immune-related parameters, and there are no indications of ion regulatory disturbances at salinities as low as 6‰. This shows that the Atlantic cod is an extremely euryhaline marine teleost species, and indicates that commercial Atlantic cod aquaculture can just as well be carried out in locations with low as with high environmental salinity. © 2012 Published by Elsevier B.V.
    Aquaculture 03/2013; 380-383:70-79. DOI:10.1016/j.aquaculture.2012.11.036 · 1.88 Impact Factor
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    ABSTRACT: Environmental tolerances and preferences of cod are reviewed and attempts are made to predict optimum conditions for growth. Physiological energetics data are collated and equations are derived enabling the prediction of food intake and growth rates of cod under different environmental conditions. The findings of nutritional studies are reviewed and hypotheses relating the effects of dietary formulation and food type to digestive efficiency, nutrient storage and body composition are presented. The results are discussed in relation to practical problems associated with the farming of cod.
    Aquaculture 05/1988; 70(1-70):1-19. DOI:10.1016/0044-8486(88)90002-6 · 1.88 Impact Factor
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    ABSTRACT: This study examines the capacity of Atlantic cod (Gadus morhua) to withstand exposure to low salinities ranging from 1 to 7 g/l. Cod were exposed to hypo-osmotic waters (1, 3, 5 and 7 g/l water salinity) at 10°C over a period of 6 days. Mortality rate, changes in osmotic parameters and changes in plasma glucose were monitored as indices of stress. No cod survived more than 20 h after transfer to 1 g/l water salinity, while survival rate increased to 5% in the 3 g/l treatment, to 95% in the 5 g/l treatment and to 100% in the 7 g/l treatment. The 1–7 g/l range in water salinity brought about a gradation in the osmotic response. Plasma osmotic and ionic concentrations dropped sharply in the first 48 h of 1, 3 and 5 g/l treatments. Cod surviving exposure to 3 g/l had low ionic and osmotic concentrations, similar to those of moribund fish, whereas fish in the 5 g/l treatment returned, after 5 days, to higher concentrations close to the average for animals kept in 7 g/l salinity. Cod in the 7 g/l treatment maintained concentrations slightly lower than the average for control fish throughout the experiment. Plasma glucose concentration decreased considerably, in both the control and experimental treatments. The rate of decrease was lower at 7 and 28 g/l salinities than at 1, 3 and 5 g/l salinities. Blood glucose does not appear to be a reliable osmotic stress indicator in Atlantic cod.
    Aquaculture 10/1993; 116(2-3-116):219-231. DOI:10.1016/0044-8486(93)90010-V · 1.88 Impact Factor
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