On the Orientation of the Plaice (Pleuronectes Platessa L.) I. Evidence for Orientating Factors Derived from the Ices Transplantation Experiments in the Years 1904-1909
Re-examination of the original data of the ICES displacement experiments carried out in the first decade of this century showed that plaice return towards the initial ground, even when displaced over considerable distances to unfamiliar territory. The speed of homing is low and the majority of the transplanted fish never returns exactly to the ground where they were caught. After one year the cluster of transplanted fish, as a whole, has reached a position between the catch and the release position. No further gain in homing was achieved in the second year after release, the cluster of displaced fish after two years more or less coinciding with the position reached after one year. Plaice displaced over a distance of 190 miles or more only showed a homing tendency in the first two months after release. A number of displacement experiments showed that recruits were not guided by the residual bottom currents when selecting their spawning grounds. Adult plaice, revisiting their spawning grounds, did not use the currents as directional clues for migration.