Declining wild fish runs

SALMON

Recent high rod catches of salmon (prompting media headlines like "Record angling catches") are misleading. Rod catches should not be confused with salmon runs. Indeed high catches should not be interpreted as "salmon abundance", at least in historical terms.

Salmon, that reached our natal rivers in the 1960s, 1970s and 1980s, were those that had successfully circumnavigated the profusion of coastal and estuary nets which could easily kill up to 500,000 salmon and grilse annually (and that was just the declared catch). Netting effort is now just a small fraction of what it was back then; in other words human predation prior to fish entering our rivers is hugely reduced. Thus fish that now return to our coasts are far more likely to reach their rivers of origin than was the case prior to the great netting buy-outs in the late 1980s and 1990s.

In essence the decline in exploitation by nets has been a vital compensating factor for the dramatic fall in the marine survival of salmon – before the fish arrive back on the Scottish coast after one or two (occasionally more) years at sea.

Marine survival is currently in single figures; fairly recently it was 25 to 30 per cent and in the 1960s even higher. This issue is now by far the most critical factor affecting Atlantic salmon fisheries and the need to maximise the number of wild smolts going to sea has never been more important.

SEA TROUT

To quote Marine Scotland's catch statistics for 2011: "Total rod catches (retained and released) of sea trout for Scotland as a whole have declined over much of the period since 1952, when our records began. Although catches have shown a slight increase since 2008, total reported rod catch in 2011 was the sixth lowest in the 60 year time series".

This decline is despite the great contraction in the netting industry. Two regions – the East (Tweed to Tay) and North (Kyle of Sutherland to Hope) – are bucking the downward trend in rod catches. Sea trout stocks elsewhere are a major cause for concern, particularly in the salmon farming areas of the west Highlands and Inner Hebrides; here mature sea trout are very scarce indeed as few fish seem to survive beyond the finnock stage.

Salmon population trends since the 1970s