Riparian Predators

How Salmon are faring in our rivers is a very topical subject currently, but just what are their on-shore predators?

Sawbill Ducks 

Mergansers and Goosanders are to be found in considerable numbers throughout the River Earn system. They feed extensively and exclusively on the fry and juveniles of salmon, sea-trout, brown trout and grayling. Once they were very rare but since their increasing numbers have been given protection by Government bodies they have multiplied enormously. As a concession, permission is granted to cull a ridiculously small number of these predators, but this has only a negligible benefit in controlling their expansion. 

They are highly successful predators. They frequently produce clutches of up to a dozen juveniles, and because the female parent is a very vigilant and protective guardian, these clutches frequently achieve adulthood with negligible losses. Mrs Mallard on the other hand often produces eight or nine chicks, of which frequently, only two or three achieve adulthood. 

On examination of a number of dead adult birds I have found in recent years, their stomachs are found to contain the maximum of juvenile salmonoids, “just like a John West sardine tin”. 

Cormorants 

Cormorants are sea-birds which have adopted a freshwater environment as a preferred option to starving in the estuaries of our rivers. They possess a voracious appetite and will take juvenile salmonoids and adult grilse, sea-trout, finnock, brown trout and grayling up to 3lbs in weight. They hunt by swimming underwater to intercept their prey and can do this at great speed. Large numbers of these birds appear as autumn commences and they are present throughout the winter and into the Spring before they return to their marine environment. 

However, nowadays, some colonies of these birds are now resident in fresh water throughout the year and Loch Earn hosts a number of such colonies. Typically, it is permissible to shoot only a very small number of these birds under a licence. However, once again, this has very little impact on their populations and the subsequent damage they do to depleting fish stocks. 

Cormorants are particularly destructive during a period of cold frosty weather in winter when ponds and fisheries, where they find fishing particularly rewarding, are frozen over and as a result it is impractical for them to fish there. They then revert to raid sections of the river which are unlikely to have frozen. In the bitter cold winter of 2010-11, their activities in the Earn resulted in the loss of all piscine juveniles. 

Otters 

Otters take salmon, sea-trout, brown trout, and grayling and indeed any other edible creature which comes their way. They are a particular nuisance when migratory fish are spawning, exhibiting a preference for the hen fish when they are full of roe.

Such fish are a small minority of the available stock and a most precious minority at that. 

In past times, otters would feed on eels as their staple diet; however, with the near disappearance of eels from freshwater otters are more catholic in their tastes nowadays. Otters do cause problems, but their numbers are few. Moreover, they are allies against mink which are a more lethal threat to fish stocks. An otter will pursue a mink, kill it and eat it if he can. 

Beavers 

Although beavers do not predate on our fish stocks directly, their presence and activities cause considerable problems for fishing (as well as agricultural) interests. The felling of perfectly healthy trees, which protect the integrity of the banks and have been planted for that purpose, but which also supply shade and a source of insects which nourish piscine juveniles, is very regrettable. Beavers form their ‘lodges’ by excavating through ancient man-made flood bankings which results in the constant loss of arable ground and the re-alignment of the river courses. Some of our pools have already been altered for the worse by their activities and their felling activities requires plenty of activity, tidying up their destructive trends with a chainsaw. 

Beavers are now present in number on the Machany Burn, a prime spawning burn, now de-graded. Where they have created dams across the burn in areas where salmon formerly spawned on gravelly areas, such locations are no longer fit for spawning. 

We utterly reject that the activities of beavers in this area mitigates flooding in any way, instead judge that their presence is negative and destructive to both other wildlife and the river environment generally. They might look cuddly, but they are incredibly harmful to the river environment. 

Mink 

Mink are a serious threat to fish stocks in the Earn and have been since about 1960 when some well-intentioned but idiotic animal-rights saboteurs “liberated” the inhabitants of a commercial mink farm at Dalchonzie on the Upper Earn. It would be impossible to calculate the damage and mortality caused by the descendants of these liberated mink over the intervening sixty years. They are a threat to all Fur, Fin and Feather. 

However, as previously mentioned, they are pursued by the otter as well as many shooting and sporting interests in this area, who are anxious to cull them. They are shot and trapped extensively, and as a result, they are thankfully few in number. 

Dolphins 

Dolphins restrict their activities to the estuaries of rivers. However, there are now substantial pods of dolphins residing throughout the year on every large east coast river estuary in Scotland. Depending on their size, a dolphin requires between 5-15 kilos of food per day to fund its energy requirements. This does not include the fish that they damage by playing with them, tossing them around like a rugby ball for the amusement of the Chris Packhams of this world. 5-15 kilos, 365 days a year, 20-30 dolphins per estuary, you can do the maths! 

Seals 

To the surprise of many, seals do not respect their preference to feast on salmon flesh to the estuarial areas of the Tay and Earn but will follow the runs of migratory salmon up river (as far as Kinkell Bridge) in order to prey on them. 

In former times, should a seal be found in freshwater one might shoot it with impunity. It was also acceptable that the operators of commercial salmon netting stations might dispose of seals if they were deemed to be interfering with the netsman’s ability to operate. 

Nowadays, seals swim up the sixteen miles from salt water to gorge themselves on spawning salmon performing on the gravel at Kinkell Bridge. They will also ambush fish at any stage of this journey, and I have had to apologise to anglers who have come to fish our pool, for the presence of seals within them, attacking fish through the months of September and October. Clearly, this causes major problems and with seal numbers increasing, the damage they do is likely to increase as well.

Ospreys 

Ospreys usually return from their annual sojourn in Africa towards the end of March. There are some nine osprey nests in the vicinity of Kinkell. Although they will take fish up to a good size (grilse and sea-trout to 3-4lbs), they usually confine their activities to visiting stocked ponds and small fisheries where the fishing is easier, much to the annoyance of their operators.

They are significant predators but stunning with it.

The Marine Lamprey

Thankfully, these creatures are very rare. They are a primitive cartilaginous being of prehistoric appearance, approximately a metre long and as thick as a man’s arm. They possess seven gill slits on either flank and instead of a mouth, a sucker with inward pointing, rasping, teeth. For a better description, I suggest that you might read Henry Williamson’s description in “Salar the Salmon”. 

They are unpopular with fishermen as, when they migrate, mimicking the journey of the salmon to the same area of the river when salmon spawn themselves, typically in June or July, they hitch a ride on the side or belly of a salmon until they arrive at their destination. In the meantime, they suck the blood and goodness from their host before dropping off. 

They are regarded as an indicator of a clear and pure river and do not tolerate a poor environment. In the past they were gaffed out as enemies of salmon. This was achieved as they are extremely vulnerable in the period just prior to spawning when they crate their spawning bed. I have witnessed them only on a few occasions over the last 22 years here on the Earn.

American Signal Crayfish

These creatures were inadvertently and carefully released into the River Earn near a trout hatchery some fifteen years ago. Those who were responsible for this carelessness should have been shot! This creature is alien to the UK, much bigger and more destructive than the native crayfish. It burrows into soft riverbanks, honeycombs and collapses them, but even more unfortunately, it feeds on fertilised salmon eggs, burrowing into the ground containing the eggs and feasting on them. There is no evidence to date that they have migrated as far downstream as Kinkell and that is pleasing. It is possible that the rocky nature of the riverbed immediately above Kinkell and continuing downstream to the Tippeny pool has proved an impossible barrier to these invaders.

Let’s hope so.

Written by: Sandy McIntosh, Ghillie at Kinkell, River Earn