CHECKING OF CRITERIA USED FOR DETERMINING THE POSITION OF SEA WINTER BAND ON ADULT ATLANTIC SALMON (SALMO-SALAR L) SCALES IN FRANCE AND SPAIN

The factors used to determine the position of sea winter band on scales were reexamined for the Atlantic salmon (Salmo salar L.) French and Spanish stocks. A total of 658 scales of salmon caught in 24 French (1988 fishing season) and six Spanish (fishing seasons from 1984 to 1989) rivers were analysed. The first winter band occur well at a back-calculated length between 40 cm and 60 cm estimated by linear regression as only 2.3% of fishes had a size outside these limits. There is no significant difference between the two stocks. In multi sea-winter salmon, 24.3% of French and 48% of Spanish fish had a second winter band occurring at a back-calculated length equal or superior to 1.55 time this of the first winter. In three sea-winter salmon, 45.2% of French fish and 70.8% of Spanish fish three sea-winter old had a third winter band occurring at a back-calculated length equal or superior to 1.2 time those one of the second winter. In the two last cases, there is a significant difference between the two stocks. The results are discussed and it is proposed to adopt the 1.40 and 1.17 values to determine the position of the second and third winter band as the percentage of well determined fishes increases strongly in the French and Spanish stocks.