UK: Tamar salmon tagged to provide vital data on health of fish stocks
Fishing experts have also caught nearly 900 sea trout smolts, so they can be identified when they return to the Tamar.
Salmon and sea trout are monitored intensively on the Tamar River to provide information on biology and stock status. The Tamar is one of 3 index rivers in England and Wales, but the only index river reporting sea survival rates for salmon and sea trout.
Some 4,093 salmon smolts, heading out to sea as part of their migration to their adult feeding grounds at sea, were trapped using the Environment Agency’s rotating smolt trap on the Tamar river.
Fishing experts then carefully injected a tiny tag (the size of iron filings) into their nasal cartilage. This tag can be detected in all adult fish that return to the Tamar and are caught in the Gunnislake Fish Trap. The information can then be used to calculate survival rates at sea.
Sea trout smolts are tagged or finned every other year to distinguish between different age classes and calculate sea survival rates. line of tagged or fin-clipped fish, only data collected from the Gunnislake adult trap is used to calculate marine survival rates and it is best that any fish caught be released as soon as as possible.
Paul Elsmere, head of environmental monitoring for the Environment Agency, said:
This information is vitally important and provides vital data on the health of our salmon stocks, and is used to inform national and international salmon management and conservation measures.
Salmon are a key indicator of climate change and are considered by many to be the perfect barometer to gauge the health of our oceans and rivers, as they have life stages in both environments.
Climate change, including extreme weather events, pollution, rising sea temperatures and a host of other man-made issues, have all had a major – negative – impact on salmon populations.
Since the beginning of the Tamar index river program in 2004, we have recorded significant changes in run timing, stock structure, body size and condition, recruitment of juveniles, and the emergence of new diseases and conditions. , all of which may be linked to climate change.