THE impact of otters on fish stocks has been thrust back into the spotlight following a surge of sightings up and down the country.
Media outlets have published photographic evidence of the predators in more heavily populated areas, including Wolverhampton and Salisbury city centres, while videos have also emerged online of the mammals taking birds – a trend some anglers speculate will rise as the species runs out of fish to eat in certain areas.
The increased sightings are grave concern for Barbel Society chairman Steve Pope, who believes we’ve reached a tipping point on our river systems.
“These are normally elusive animals that are now getting spotted increasingly,” he said.
“Nobody really knows how many are out there, and I fear that the natural predator-prey balance on our rivers is now out of sync.”
Steve said that a petition to the Government is in the pipeline, requesting a review on the protections around otters.
“We have to look at anecdotal evidence, which shows the otter playing a huge part in decimating barbel populations on the Kennet, Ouse and Bristol Avon, to name a few,” he added.
“There are parts of the Severn where it was once possible to catch 10 barbel a day, but where now you’d be lucky to catch one. With the exception of the Trent and Wye, there are few strongholds left now, just small and localised populations. Once these are hit, I fear barbel fishing in this country could be finished. It’s time for us to act, as this is a man-made problem, not the fault of the otter.”
There are many, however, who think that a balance is returning to our rivers, and that we may be over the worst of the problem. Hampshire Avon barbel record holder Pete Reading said:
“I’ve fished the Avon and Stour for 40 years and the otters have had little impact. They are often blamed for declines of certain species, when there are many other contributing factors. What happened on the Great Ouse in particular was an opportunist predator taking advantage of a very old population of barbel. These older fish aren’t as healthy and are an easy meal. Younger, fitter fish are far better at evading these predators.”
These sentiments are supported by fellow specialist and Ouse regular Jamie Cartwright.
“It’s all down to balance,” he said.
“I see quite a lot of otters while fishing, but not a lot of evidence of large kills.”
Jamie has also observed a decline in another creature threatening fish stocks – the signal crayfish – and believes otters could actually be playing a part in controlling this invasive species.
“In the last five years crayfish activity has fallen dramatically on the stretches I fish. We aren’t seeing quite as many big chub and perch, but a healthy population of smaller fish is coming through,” Jamie added.
This observation of otters and crayfish hasn’t just been noticed on the Ouse either. Keen angler Dr Mark Everard has noticed similar patterns on his local Bristol Avon.
“Otters are typically stone turners,” he said.
“This makes a crayfish the perfect meal, and otters are controlling their numbers. Analysis of otter spraints in some areas are entirely made up of crayfish. Studies also show an otter’s diet is made up of far more small fish than people realise.”
Professional ecologist Daniel Wood revealed just how varied otter’s diets can be.
“They will exploit the most prolific species in any area,” he said.
“In rivers, this is predominantly smaller species such as bullheads, chub and dace. There is a study on a Somerset wetland, however, where 41% of the spraints collected featured bird remains – mainly coots and even juvenile cormorants. Of course, if an otter encounters a big fish while foraging, it will take it, but there’s a lot of easier meals. It’s well documented that otters love eels and with their decline, it appears that crayfish have replaced that part of their diet.”
In Dan’s study of otter spraints on the Bristol Avon, bullheads were present in 72% of the samples, whereas large fish featured in just 31%. He suggests that the issue of declining barbel populations may have more complex contributing factors.
“Improving river habitat and creating spawning gravels are what is needed to see a growth in barbel stocks again.”
Dan also had some interesting insights into the apparent boom in otter sightings.
“Otters are territorial, with a ‘patch’ of around 10 miles, so they limit their own numbers well. When people are seeing multiples, they could be looking at families of otters,” he added.
So, are anglers’ concerns justified? Professor of Invasion & Fish Ecology at Bournemouth University, Rob Britton, offered this summary of the argument.
“It comes down to how you view the part of otter diet that is of interest to anglers,” he said.
“Whenever I’ve studied otter diets, the proportion of angler target species is low. This is not to trivialise the loss of large fish and is of little consolation to anglers or fishery owners if high-value fish are taken. For this reason, the use of otter fencing is still a good preventative measure.”
