Review of morphological and behavioural differences between reared and wild individuals: Implications for sea‐ranching of Atlantic salmon, Salmo salar L., Atlantic cod, Gadus morhua L., and European lobster, Homarus gammarus L.

Abstract

The main question which must be raised when planning to enhance natural populations through sea ranching is whether reared organisms are fit for a life in the wild, or more specifically, whether there are differences between reared and naturally resident individuals. The causes and effects of these differences are reviewed, and results from the Norwegian enhancement programme, which compared reared and wild individuals of Atlantic salmon, Salmo salar L., Atlantic cod, Gadus morhua L., and European lobster, Homarus gammarus L., are discussed with emphasis on morphological and behavioural differences. It was concluded that exposure to an artificial rearing environment during ontogeny can affect both the phenotype and the behaviour of the reared individuals, and thereby, their potential for survival after release into the wild as well. Suggestions are made as to how to diminish observed differences, and thereby, improve the survival potential.

Deformities in larvae and juvenile European lobster (<i>Homarus gammarus</i>) exposed to lower pH at two different temperatures

“…Wickins et al (1995) did report moulting abnormalities in European lobster larvae in relation to testing different diets, but with no further description of what the abnormalities were. In aquaculture, hatcheryinduced changes due to feed, tank design and/or substrate have been described for a number of fish and shellfish species (Olla et al, 1998;Svåsand et al, 1998;Tsukamoto et al, 1999;and references therein). In shellfish, most changes documented are morphological, e.g.…”

Effect of size‐selective mortality on growth of coastal cod illustrated by tagging data and an individual‐based growth and mortality model

“…Differences in food intake and food quality have been observed during the first weeks after release (Nordeide & Sal vanes 1991 ), but the diet of the reared cod gradually changed to the same prey choice as wild cod after a few weeks (Kristiansen & Svasand 1992). In most studies the growth rates of reared cod have been equal to or better than those of wild cod of the same age (Kristiansen 1987;Nordeide & Fossa 1992;Svasand et al 1998b;Ottera et al 1999;Paper II). Small released cod suffered high mortality during their first months in the sea (Nordeide & Salvanes 1991;Svasand & Kristiansen, 1990b, Papers II-IV;Julliard et al in press), and we should assume that this mortality was higher than for similarly aged wild cod in the release areas.…”

Migratory behaviour and ocean survival of escaped out-of-season smolts of farmed Atlantic salmon Salmo salar

“…The pollack, which is the dominant fish predator in this fjord (Salvanes 1995), is evidently very capable of preying on salmon smolts. High losses of hatchery-reared fish after releases into the wild are common (Svåsand et al 1998, Thorstad et al 2011. However, predation in the fjord was probably much lower in May and June 2008, when all the acoustically tagged smolts survived the migration out of the fjord (Skilbrei 2010a), than in the period September to December 2008, when a high proportion were taken by predators within the fjord.…”