Relation between stock size and catch data of Atlantic salmon (Salmo salar) and Arctic charr (Salvelinus alpinus)

Reliable catch statistics are one of the most important factors in fisheries research and in managing exploita- tion of fish stocks. For more than 30 years catches in Icelandic rivers have been reported in logbooks. In these logbooks, fish species, fish size, fishing pool, date, etc. were registered. It has been suggested that the total number of salmonids caught annually reflects the total population in each river. Fishing effort, i.e. the number of rods per day, has been regulated by authorities, as well as the length of the fishing season. However some minor changes have developed gradually over time. In the '90s new fish counters were introduced, making possible to evaluate the relation between run and catch. The counter gives the number of migrating fish and their size. The run was divided into one-sea-winter salmon (1SW), two-sea-winter salmon (2SW) and charr, by size. The relationship between the total stock size and the number of fish caught for 1SW salmon, 2SW salmon and charr in the Vesturdalsá and Blanda rivers was then examined. This relationship was highly sig- nificant in all cases, except for charr in the River Blanda. The results showed that the salmon catch statistics in the Vesturdalsá and Blanda rivers are good indicators of the size of the salmon run. This relationship was not as strong for the charr. Furthermore, the size of the population of salmon and charr showed similar fluc- tuations.