GREY SEALS AS COMPETITORS WITH MAN FOR SALMON 



J. D. LOCKIE 



Nature Conservancy, 12 Hope Terrace, Edinburgh 



There are two main problems regarding grey seals (Halichoerus grypus) and 

 their effect on salmon fisheries ; the damage done to nets and their contents, 

 and the influence of seals upon the stocks of the salmon {Salmo salar), from 

 which the commercial catch is drawn. The extent of damage to nets on a 

 sample length of coast-line in Northumberland and Berwickshire (NE 

 England) has been considered elsewhere (Lockie, 1959). 



This paper explores an aspect of the second problem, by attempting to 

 compare the amount of salmon taken by grey seals with that removed by 

 man. Many new facts — published and unpublished from various sources — 

 have been discovered about grey seals in recent years and, in this paper, these 

 facts are drawn together in order to see how far one may justifiably draw 

 firm conclusions about competition between grey seals and man for free- 

 living salmon. 



The study area is 48 km (30 miles) of coast between Goswick, Northum- 

 berland, and Cockburnspath, Berwickshire, including the River Tweed; 

 salmon fishing is carried on throughout its length and the Fame Islands seal 

 colony hes 24 km (15 miles) to the south. 



NUMBER OF GPJEY SEALS ASSOCIATED WITH THE FARNE 

 ISLANDS, BASED ON COUNTS OF PUPS 



Hewer (1957) has attempted to draw up a life-table for the grey seals of 

 Shillay (Scottish Hebrides) compatible with the known vital statistics of this 

 species. These were: that cow seals have their first pups at three years of age; 

 and that bull seals do not enter the true breeding class until about their 

 eighth year and are probably over ten years before they obtain territory on 

 a breeding ground. The basic facts of reproduction were thus similar to those 

 of the Pribilof fur seals [Callorhinus ursinus) for which life-tables have been 

 published (Kenyon & Scheffer, 1954). Using the female life-table. Hewer 

 (1957) then calculated the age structure and size of the Shillay colony from 

 the observed number of pups born. Later work (Hewer, in progress) indicates 



