Gordon Mack, Angling Correspondent and Martin Williams

One of Scotland's most iconic angling prizes, the Malloch Challenge Trophy for the heaviest salmon caught by fly-fishing, is being reinstated this year with the aim of helping to promote fish conservation.

The solid silver leaping fish, valued at £15,000, was first awarded in 1972 but was retired in 1999 when sponsorship of the prize ended. It was named after the Perth tackle retailer and legendary angler P D Malloch.

Now, with the backing of the Tay Salmon Foundation and the Tay District Salmon Fisheries Board, the elegant trophy will again be contested by anglers from the Tweed to the Thurso. For the first time, however, all fish must be released alive back to the river.

Entries will have to carry an accurate weight or estimation of weight, appropriate measurements and the corroboration of an independent witness. The 2009 salmon fishing season opens next week.

Tay Salmon chairman John Milligan said yesterday: "The board is delighted to have been able to acquire what was for decades the most coveted award in the Scottish angling world. We look forward to receiving entries from rivers across Scotland. I have no doubt that it will be keenly contested."

New trophy secretary Robert Rattray added: "In the last year or so we have seen something of a resurgence in the numbers of very large salmon in Scottish rivers, so I have no doubt the trophy will spawn more interest than ever. It is particularly heartening that from now on it will be closely associated with conservation."

During 28 consecutive years of competition, winning fish were landed from a variety of rivers including the Dee, Spey, Tweed, Tay and Naver. The last winner was a 43lb fish from the Tweed.

Meanwhile, new results from 40 years of intensive scientific research show that Loch Leven in Fife, once dubbed the Queen of Scottish Lochs, is finally on the road to recovery after decades of pollution problems.

Experts say the one-time mecca for anglers is making progress to recover its historic position as one of Scotland's finest brown trout fisheries.

The largest shallow loch in lowland Scotland is recognised as an internationally important nature reserve, not only because it attracts the largest concentration of breeding ducks found anywhere in the UK, but also because it provides an autumn and winter refuge for thousands of migratory ducks, geese and swans.

In the mid-1980s, phosphorus pollution from industry, sewage, and agriculture was entering the loch, causing a serious decline in water quality.

Nutrient levels increased, toxic algal blooms became more common, and water clarity became reduced.

This resulted in both ecological and socio-economic deterioration of Loch Leven which led to questions being raised in parliament.