|Rheotaxis in juvenile sole Solea solea (L.): influence of salinity and light conditions|
Champalbert, G.; Marchand, J.; le Campion, J. (1994). Rheotaxis in juvenile sole Solea solea (L.): influence of salinity and light conditions. Neth. J. Sea Res. 32(3-4): 309-319
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579, more
|Authors|| || Top |
- Champalbert, G.
- Marchand, J.
- le Campion, J.
The effects of water currents, salinity and light regime on the orientation and swimming activity were studied in juvenile wild and hatchery-reared sole of two size ranges (10-20 mm; 21-30 mm) in an oval flume with a straight working section and a thin bed of fine sand. Short-term experiments using increasing water velocities were carried out at low salinities (S=26, 18 and 11) similar to those found in estuarine areas where recently metamorphosed juveniles settle and develop. Long-term experiments (24 h) were carried out with constant water velocities (3 cm·s-1 and 5 cm·s-1 in juveniles of 10-20 mm and 21-30 mm, respectively) and 4 water salinities (S=35, 26,18 and 11). The behaviour of juvenile sole was dependent on current speed regardless of light conditions. In the short-term experiments, the number of rheopositive fish increased with increased current. At low salinities, regardless of the origin and the size of the animals, the relationship between water velocity and rheopositive reactions was not significantly different under different light conditions. In long-term experiments, most juveniles remained oriented against the current during the nycthemeral cycle but the percentage of rheopositive-responding fish was higher during the dark phases or in total darkness than during the illuminated phases or under constant illumination. The interrelations between current, salinity and light are discussed and a hypothesis is proposed to explain the migration of juvenile sole towards coastal areas and estuaries.