Borders brown trout still much of a mystery for biologists

Lyne Water Trout released by Shaun Robertson who worked at the Tweed Foundation Fish Conservation Centre.
Lyne Water Trout released by Shaun Robertson who worked at the Tweed Foundation Fish Conservation Centre.

BIOLOGISTS responsible for unravelling the mysteries of life in the River Tweed are hoping a new online recording project will help finally shed light on local brown trout populations.

The Scottish Fisheries Co-ordination Centre (SFCC) is an association of fisheries trusts, district salmon fishery boards, the Scottish Government and others involved in the management of the country’s freshwater fisheries.

Trout Fishing on the River Tweed at Walkerburn.

Trout Fishing on the River Tweed at Walkerburn.

The SFCC Angling Diary is designed to overcome the problems of traditional paper-based angling diaries and logbooks by turning them into a single online diary (www.anglingdiary.org.uk).

The diary is free to use and anglers can use it to record information on it, which they can choose to keep private or share as a valuable angling and biological community resource.

Fisheries biologists such as those at the Tweed Foundation are excited at the prospect of, for the first time, having a reliable supply of continuous angling data to help discover more about brown trout populations in the Borders.

Among them is Tweed Foundation head biologist, Dr Ron Campbell, and his colleague, Kenny Galt - the latter is in the unique position of being Scotland’s only dedicated full-time trout and grayling biologist.

Ron explained that the Foundation’s only real ‘window’ into how trout numbers have fared over the generations has been the competition records of local angling clubs and associations.

“Occasionally you get a good series when someone’s kept a series of records well. You can see the effect changes in regulations have on catches.

“Selkirk Angling Association is a good example. It has a very good series of competition records from the 1920s. But they then changed the minimum size from 2ozs to 2.5ozs and the catch rate fell by half when they did that.

“Without records it’s all just anecdotal. That’s where the national online angling diary scheme - which Foundation assistant biologist James Hunt has been involved with - comes in.

“The advantage from our point of view is if anglers do opt to share their information, we get to use the data. You see, salmon fisheries have to keep records by law, so there’s lots of records for that because it is a commercial business. But that’s not the case for brown trout and there’s just a black hole as far as data is concerned.”

Ron says recent surveys of trout spawning grounds have shown them, with a few odd exceptions, all to be “stuffed” with trout fry. “The thing is we don’t know if these are going to be brown trout or sea trout.

“That’s the biggest puzzle. We hear all these complaints from anglers on the one hand and all these burns are stuffed with trout fry on the other hand. So what’s the story? That’s our main focus.”

Ron says the advent of new techniques enabling the chemical composition of trout fry to be determined should, hopefully, help solve this riddle. “We’re doing the chemical analysis for Napier University and are looking for funding at moment to start mapping the Tweed catchment on a large scale, so instead of just saying there’s all these trout fry we can start to find out, whether these fry are sea or or brown trout.

“Because we have no idea of what the relative strengths of brown trout and sea trout are. It could be that 90% of the trout fry in this catchment come from sea trout eggs, which would give you a very different picture of what’s going on.

“But it’s more complicated than that because although female sea trout tend to go to sea - most sea trout are females - you also get little males which stay behind in freshwater even though they come from sea trout eggs.”

Kenny pointed out it was still early days. “What trout do in different places, a mixture of different ancestry, how they evolved to suit different places, geology and other factors are all combined to decide what a fish does,” he told us.

“Trout might be doing something completely different in one place from another, so it maybe there are separate populations. Or maybe there’s very complex population structures or it maybe not, but until we look, we’re not going to find out.

“Trout have always been so common that people have taken them for granted - that’s also why trout fishing is so cheap in Scotland. Yet trout is the fish that needs the most research work done on it, but is probably the one which has had the least done.”

Ron added that trout has always been seen as the poor relation in research terms when compared with the economic importance of salmon to Scottish rivers.

“But if we can develop this tool to separate out brown and sea trout, it would be a huge step. But what we will find out, I can’t even begin to guess at.”

On claims from some quarters that it is the work to improve salmon habitats and the catch-and-release policy for salmon which have had a negative impact on trout fishing, Kenny explained: “Salmon and trout don’t overlap much. Salmon spawn in the main streams, while trout spawn in little streams. The habitats are segregated. What happens in one doesn’t have much impact on the other.”

As for the experience of trout anglers themselves, it all depends on who you talk to. Already this season a number of large trout have been landed including a 7lbs monster at St Boswells

As Ron says, skilful anglers always do well. “The rule of thumb is that is 90% of anglers catch 10% of trout, while 10% of anglers catch 90% of trout.

“Angling techniques have changed a lot over the years. There used to be a lot more burn fishing for example.” Ron, Kenny and their colleagues survey about a third of catchment each sumer, including trout burns, and have extensive data from sampling going back to early 1990s which shows there has been no real difference in trout fry levels.

Kenny has also surveyed anglers - who they are, where they come from, how do they fish and what they think constitute’s a good day’s fishing. It turns out the average Tweed angler has been fishing for 36 years.

Ron added: “The more anglers we can get reporting their trout catches, the more robust the data will be. But we’ve only got a handful at moment and we need more.”

“Catches are influenced by angling ability, weather, time of year and so on,” said Kenny. “We need enough returns over the course of a season to average out the variations you get.”

Kenny recently repeated the fly life survey last carried out by a team from Edinburgh University in 1974. “I’ve not yet finalised the data recorded but it’s fairly obvious the fly life has changed and those changes are most likely responsible for changes in the river. It is most likely due to temperature changes because the river’s getting warmer.

“Straight away there’s an indication that we’re living along a river that has already changed, at the very least slightly, but even slight changes can have huge impacts on fly life.

“And if fly life is changing, who knows in what ways the fish are changing. Feeding habitats have changed because the food’s changed. Who knows how those have changed over last 30 or 40 years. Changes in the natural environment, mean those things living in it change too.”