As autumn run salmon tend to spawn in the main stem of the Tay or in larger tributaries like the Isla, it is difficult to gauge the health of this component of the population. It is wholly impractical to use fish counters, for example on rivers of this size.
An alternative method of estimating population size in such circumstances is to tag fish entering rivers and determine angling “exploitation rates” on the basis of tag recaptures and then to scale up the relevant total number of fish caught by anglers.
Therefore, in 2011 and 2012, the Tay Foundation, which holds the leases of most of the former netting stations in the Tay estuary, agreed to allow experimental netting to be carried out for the purposes of tagging and releasing fish. A licence was also obtained from Marine Scotland to fish after the end of the official netting season (20 August). The netting was conducted by former netsmen of the Tay Salmon Fisheries Company.
In the event, netting salmon proved to be no simple task. Many stones and other snags had accumulated on the bottom of the river since nets last operated in 1996 and these were a considerable hindrance. River flows were also not ideal and only a handful of fish were caught in both years and as a result the operation was curtailed early in both cases.
A tagged salmon caught during experimental netting in the upper Tay estuary, August 2011.
Experimental salmon netting in the upper Tay estuary, August 2011