Effect of winter food deprivation on growth and sexual maturity of Atlantic salmon (Salmo salar) in seawater

Abstract

By identifying individual Atlantic salmon (Salmo salar) smolts (age 1+, mean weight 95 g), a tank study with four treatments (n = 175 fish per tank) indicated that maturation as grilse is associated with changes in somatic growth over many months, from July of the first summer in seawater onwards. The grilse rate in both sexes was associated with a relatively high condition factor from July onwards, but was independent of fork length. Food deprivation in either early winter , late winter (February-April, 0.7-4.0°C), or both early and late winter (double deprived) reduced the female grilse rate (p < 0.01) to 4, 7, and 2% versus 18% in the control, whereas male grilse rate was reduced by a lesser degree (p > 0.05), 43, 39, and 33% versus 44% in the control. Mean condition factor among both maturing and immature fish decreased by a similar degree due to food deprivation but from spring onwards increased by a faster rate among incipient grilse. In a large experiment in four sea cages (each n = 3885 fish) using similar food deprivation treatments, the reduction in grilse rate was statistically significant in both sexes: among males, 28-36 versus 43% in the control; among females, 3-4 versus 6% in the control.Résumé : Dans une étude en bassins avec quatre traitements (n = 175 poissons par bassin) dans laquelle des smolts de saumon atlantique (Salmo salar) (âge 1+, poids moyen de 95 g) étaient identifiés individuellement, on a observé que la maturation précoce (madeleineaux) était associée avec des changements dans la croissance somatique sur de nombreux mois, à partir du mois de juillet du premier été en eau de mer. Le taux d'apparition des madeleineaux chez les deux sexes était associé à un coefficient de condition relativement élevé à partir de juillet, mais était indépendant de la longueur à la fourche. La privation de nourriture au début de l'hiver (novembre à décembre, 8,2 à 4,1°C), à la fin de l'hiver (février à avril, 0,7 à 4,0°C) ou durant ces deux périodes (double privation) a réduit le taux d'apparition des madeleineaux femelles (p < 0,01) à 4, 7, et 2% contre 18% chez les témoins considérant que le taux d'apparition des madeleineaux mâles a été réduit par un peu de degré (p > 0,05), 43, 39 et 33% contre 44% chez les témoins. Le coefficient de condition moyen parmi tous les deux mfrissant et non mfrs les poissons a diminué par un degré semblable df à la privation de nourriture mais à partir du printemps a agumenté à une vitesse plus rapide parmi les madeleineaux naissants. Dans une expérience de grande envergure effectuée dans quatre cages marines (n = 3 885 poissons par cage) utilisant les mêmes traitements de privation de nourriture, la réduction du taux d'apparition des madeleineaux a été statistiquement significative chez les deux sexes : dans le cas des mâles, il a été de 28 à 36 contre 43% chez les témoins, et dans le cas des femelles, de 3 à 4 contre 6% chez les témoins.[Traduit par la Rédaction] Duston and Saunders 207

Influence of food restriction on the reproduction and larval performance of matrinxã, Brycon amazonicus (Spix and Agassiz, 1829)

“…The effects of food restriction in reproductive fish performance are still controversial (Townshend and Wooton, 1984;Ridelman et al, 1984;Thorpe et al, 1990;Jobling et al 1993;Reimers et al, 1993;Cerdá et al, 1994;Silverstein and Shimma, 1994;Karlsen et al, 1995;Toguyeni et al, 1996;Hopkins and Unwin 1997;Sohn et al, 1998;Collins and Anderson, 1999;Coward and Bromage, 1999;Duston and Saunders, 1999;Bromley et al, 2000;Carvalho, 2001) but the differences might come from the differences in the experimental design used in these studies (species, restriction and refeeding severity, season).…”

“…However, reduction in feeding rate has shown to inhibit gonadal maturation in salmonids (Thorpe et al 1990;Reimers et al, 1993;Hopkins and Unwin, 1997), Dicentrarchus labrax Linnaeus, 1758 (Cerdá et al 1994), and maturation of Scophthalmus maximus Linnaeus, 1758 females, but not males (Bromley et al, 2000). Females are believed to be more responsive to food restriction (Karlsen et al, 1995;Silverstein and Shimma, 1994;Duston and Saunders, 1999). On the other hand, feeding ratio reduction (cycles of 3 days fed/2 days unfed imposed throughout one year) did not affect gonadal development and plasma testosterone levels of Brycon amazonicus Spix and Agassiz, 1829 male and female (Carvalho, 2001).…”

Desenvolvimento gonadal de fêmeas de matrinxã, Brycon amazonicus, submetidas a restrição alimentar

“…Por outro lado, houve redução de machos maduros de salmão do Atlântico quando a restrição alimentar ocorreu no inverno (REIMERS et al, 1993) e na primavera (ROWE & THORPE, 1990). Há evidências de que a restrição alimentar afeta mais as fêmeas (SILVERSTEIN & SHIMA, 1994;KARLSEN et al, 1995;DUSTON & SAUNDERS, 1999), dependendo da duração da restrição. Em truta arcoíris, não houve alteração no tamanho das gônadas, composição e viabilidade dos ovos quando a restrição começou 40 dias antes da desova (RIDELMAN et al, 1984), mas a restrição de nove meses diminuiu a fecundidade e resultou em ovos maiores (BAGENAL, 1969).…”

“…Em alguns estudos com peixes, a restrição afetou a maturação nos machos (ROWE & THORPE, 1990;REIMERS et al, 1993) e em outros não (JOBLING et al, 1993;TOWNSHEND & WOOTTON, 1984). Os efeitos negativos da privação de alimento são mais intensos em fêmeas (SILVERSTEIN & SHIMA, 1994;KARLSEN et al, 1995;DUSTON & SAUNDERS, 1999) (RIDELMAN et al, 1984), mas uma restrição mais prolongada reduziu a fecundidade na mesma espécie (BAGENAL, 1969;KNOX et al, 1988) e em Cichlasoma nigrofasciatum (TOWNSHEND & WOOTTON, 1984). Entretanto, nenhum prejuízo no desenvolvimento ovariano foi relatado em Macquaria ambigua após redução da alimentação (COLLINS & ANDERSON, 1999).…”

Effects of Partial and Full Feed Restriction on the Plasma Levels of Thyroid Hormones and Testicular Activity in the Male Air-breathing Catfish, Clarias gariepinus during Different Phases of the Breeding Cycle

“…In fishes, food deprivation suppresses the plasma T 4 and T 3 levels, reduces thyroid tissue sensitivity to thyroid stimulating hormone (TSH), causes a reduction in 5'-monodeiodinase and eliminates the plasma thyroid hormone daily patterns (Eales et al, 1981;Flood and Eales, 1983;Shields and Eales, 1986;Cerda-Reverter et al, 1996;Power et al, 2000;Gaylord et al, 2001). Besides thyroid hormones, starvation has also been reported to affect reproductive function in different fish species (Silverstein and Shimma, 1994;Karlsen et al, 1995;Collins and Anderson, 1999;Duston and Saunders, 1999;Frantzen et al, 2004). However, these reports on the effects of feed restriction on the thyroid hormones and gonadal activity are limited to only a few temperate zone fish species and without any reference to the phases of the annual breeding cycle when the studies were conducted.…”