Ocean linked to depleted salmon stocks

IN 2007, the government finally gave way to international pressure and banned drift net fishing for salmon in Irish coastal waters.

Conservationists were delighted because they felt the fish had been on a slow slide into extinction in this country. But is there any evidence the move has halted the decline in stocks? It’s not that easy to find out. Given the salmon’s lifecycle, it’s still a bit soon for any improvements to appear. But the lack of data on the internet is surprising. 103 rivers were closed to angling at the same time as the drift net ban. Some have since been reopened, but many of them only on a catch-and- release basis. As much of the data on salmon stocks came from observations and catch returns of anglers, the closures led to a reduction in the amount of information available.

There have been other factors. Many electronic fish counters were destroyed by floods over the past couple of winters and funds have not always been available to repair or replace them. There has also been a move towards managing salmon rivers on an individual basis rather than doing it centrally. This is basically a good idea because each river has its own particular identity and set of problems, but it has led to a dearth of national data.

But by scraping together anecdotal and regional data and the scraps of hard scientific evidence that are available a picture starts to emerge. There are some positive signs. The average size of salmon returning to Irish rivers definitely seems to have increased since the drift netting ban. Southern rivers seem to be getting better runs of fish than those in the northern part of the country. Salmon have been reported from a number of small rivers and tributaries where they have been absent or very rare for some decades.

But it’s not all good news. The overall increase in numbers that should have been seen by now hasn’t happened. An international conference on Atlantic salmon held in La Rochelle in France last month was quite pessimistic. One expert predicted that southern stocks (that includes Ireland) would be extinct by 2040 despite the conservation efforts. The conference concluded that, while there were still some problems in fresh water and inshore coastal waters (including salmon farming), the main problem was something happening in the ocean.

The exact nature of this problem is still a mystery, though many experts suspect that ocean warming combined with possible changes in ocean currents are a factor. But there is a huge effort under way at present to solve all the mysteries surrounding the movement and ecology of salmon once they leave inshore waters.

An international research effort involving several concerned nations, including Ireland, is using the latest technology to track and monitor salmon in the deep ocean. It’s called SalSea and it’s making progress in finding out exactly where salmon go, what they feed on and what feeds on them. Its final results could determine whether this iconic fish continues to swim in Irish rivers.

In the meantime, a news snippet the other day recorded another piece of bad news for the Atlantic salmon. For 30 years authorities in Britain have been trying to reintroduce them to the River Thames. There were some initial successes with media reports of salmon being caught at spots on the river where they hadn’t been seen for over a century. But overall the project has been deemed a failure and is due to close down this autumn. Salmon are a difficult species to conserve but even more difficult to reintroduce to a river once they become extinct.

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