Thermal preferenda and behavior of Atlantic eels (genus Anguilla) in relation to their spawning migration

Abstract

SynopsisThe final preferred temperatures (FPTs) of adult premigratory and migratory life-history phases of American eels, Anguilla rostrata, were determined by chronic tests in a horizontal thermal gradient. Mean FPTs were between 17 and 20°C and were not significantly different between life-history phases, acclimation temperatures, illumination regimes, photoperiods or sexual maturation states. Thermal behavior of eels was highly variable, both among individuals of the various test groups and among repeated tests of single individuals. Light inhibited behavioral thermoregulation by promoting shelter-seeking. The following inferences are drawn from the laboratory findings and observations of migrating A. rostrata and A. anguilla

Occurrence of migrating silver eels Anguilla japonica in the East China Sea

“…Therefore, if migrating eels tend to seek the deepest areas during the initial stage of their marine migration, the location of this canyon may cause some eels to pass through the area based on their movements toward deeper water and they would also avoid swimming directly against any substantial northward flow of the Tsushima Warm Current. In addition, water temperatures in this area are warmer than to the west on the other side of the Tsushima Warm Current (Lie & Cho 1994) and are similar to the apparent preferred water temperature of silver phase American eels of 17 to 20°C (Haro 1991).…”

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“…Haro (1991) described that American eel (Anguilla rostrata) in saltwater preferred the temperature of 17.5 °C for both: matured and unmatured breeders. The most frequently used temperatures in experiments with Japanese eel are between 20ºC and 23°C (Ohta et al, 1995;Kagawa et al, 2003;Abe et al, 2010).…”

Neuroendocrinologie de la reproduction de l'Anguille : de la recherche fondamentale aux problèmes appliqués

“…De la même façon, plus récemment, CASTONGUAY et McCLEAVE (1987) concluaient d'après la capture des petites larves entre 50 et 300 m, que cette zone représentait la gamme de profondeur de l'aire de frai des anguilles (HARO, 1991). Cependant, ces conclusions reposent implicitement sur l'hypothèse, ainsi que le soulignent par exemple BOETIUS et HARDING (1985), d'une faible dérive des oeufs entre le lieu de ponte et l'éclosion.…”

“…Elles ont aussi conduit à l'élaboration de nombreuses hypothèses quant aux facteurs externes potentiellement impliqués dans la reconnaissance du site de frai (dans l'orientation puis l'arrêt de la migration) ainsi que dans le contrôle de la reproduction de l'anguille. En particulier, le rôle d'une température élevée de l'aire de ponte, pour l'orientation de la migration et la stimulation de la maturation sexuelle, a été largement évoqué (par exemple : WESTIN et NYMAN, 1975 ;McCLEAVE et KLECKNER, 1985 ;WESTIN, 1990 ;HARO, 1991).…”