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The Atlantic salmon (Salmo salar L.) of the North Esk with particular reference to th
By W.M. Shearer
Fisheries Research, Volume 10, Issues 1-2 Fisheries Research and the Atlantic Salmon - Assessment and Regulation in a Time of Change, December 1990, Pages 93-123, ISSN 0165-7836, DOI: 10.1016/0165-7836(90)90017-P.
This study examined the length, weight and age structure of the North Esk Atlantic salmon (Salmo salar L.) population by inspecting the in-river net and coble catch supplemented with trap catches during the Annual Close Season. In addition, the levels of exploitation exerted on the total stock by the in-river net and coble fishery have been calculated using the net catch together with the number of fish escaping capture and counted at Logie as they crossed the automatic fish counter in the appropriate period.
Fish entered the North Esk in every month in the year. Some fish entering in October of one year could not spawn until the following spawning season.
Four sea- and five river-age groups were identified in the catches. In all years, the two main components of the net and trap catches had spent either 2 or 3 years in the river, followed by one or two winters in the sea before returning to spawn. Fish derived from 1-year-old smolts were generally caught in the second half of the year and those from 4-year-old smolts in the first half of the year. One-sea winter (1SW) fish were seldom caught before May and three-sea winter (3SW) and older fish after May. The mean monthly smolt ages of the 1SW and 2SW fish declined with calendar date of capture, and the implications for management of this result are discussed. Excepting the 3SW and older sea-age groups, the length and weight of fish having the same sea age generally increased with time. Thus, 1SW and 2SW fish caught in August were generally longer and heavier than fish having the same sea age caught in May or February.
In 1981-1989, the number of fish counted over the automatic counter at Logie showed no upward or downward trend.
In some years, the number of fish belonging to a particular spawning stock which migrated over the automatic fish counter at Logie during the fishing season and after it had closed was almost equal.
The level of exploitation exerted by the net and coble fishery on the total stock of 1SW and multi-sea-winter fish ranged between 15 and 40%, and 26 and 59%, respectively.