Chris Avery | Wednesday, 3 July 2024
By July typically, I will have caught and released something like 100 to 200 Trout from the Brook, over half of them will have been scale sampled and measured from nose to the forkof the tail, to gain clues into the growth rates, and offer possible enlightenment on the strange and mysterious tales of the Trout population. This focuses my attention somewhat on the age dynamics, noting anomalies, while creating a series of, What’s; Why’s; and How’s? To exercise those little grey cells. Questioning possible bottlenecks in the system that may be dealt with in future years with the addition of some blood, sweat and, trees, or parts of them at least.
For instance providing more habitat focused on a particular stage of the Trout’s maturity where it seems evident our community is lacking. Once dealt with it not only increases that specific age range, but also everything older should inturn, be in better supply as that impasse is bridged.
One question we are always puzzling is what they are eating to make them grow so fast, if it’s not coarse fish fry, then what?
Sadly scale samples can’t tell us that, and actually adds more intrigue and complexity, as it shows sometimes that growth spurt is highest between year 2+ and year 3, but in other years its between year1+ and year 2.
Another perennial and often debated question is the source of these Trout? Are they originally native to the Brook; or from early introductions of fish transferred from natural sources; Yorkshire rivers, and Scottish lochs? Or do they come from a number of later stocked fish from fish farms, Trout that managed to survive the transformation into a wild water and a natural food supply? Surviving until the Autumn, found a way to the Redds, and then instinctively and successfully answered that call of the wild, and if so, just how long has this shameless debauchery been going on in genteel Fotheringhay?
Club records show numerous reports of Trout spotted breeding in various areas back to the 1960’s by environmental officers and fishermen alike. The current Mill owner moved in during the 1970’s when apparently there was good gravels in the millpond and below, they remember Trout regularly breeding outside their house in those days.
Which then leads to the queries; Is the population now a genetic phenotype for the Willowbrook? has there been enough generations to establish that? Is the population above the Culvert Bugger of a Bridge becoming diverse from the impeded Trout below?
These Questions should in time be answered by reading the DNA of a range of the scale samples stored up by the EA since we first started collecting them, even though earlier collections from a dozen or more years ago were of lower numbers and sporadic. Our EA scientist that collate the data on the Scale samples also have access to the resource for analysing DNA, hopefully when the relevant Laboratory has moved on from the more pressing Salmon research that its currently trying to decipher, we may then get to look at some statistical probabilities of our little mob.
Why does this matter? Well on a basic level, if your trying to work with something it helps to cater for its needs if you understand it fully. And, if ever we have to legally defend our speckled friends, or ask for the law to be on our side in a decision, it matters to be able to state that these are a natural breeding population unique to this particular water, and not replaceable with just any Brown Trout. They are distinct to the waters they inhabitant with a robustness and integrity that has adapted which each breeding cycle passed.
My first year back, just from the variety of fish sizes I was catching, it seemed to show a reasonable, though not great number of parr in the lower two beats and a number of larger adult fish around but those juvenile and smaller adult numbers seemed low in proportion to the catch. This was anecdotal evidence though, and was what got me focused on the scale sampling to be restarted with a bigger sample size on a regular basis. I distrust anecdotal evidence from others or myself.
Areas of obviously good juvenile habitat seemed that year to be strangely fish-less, apart from shoals of Dace and Chub moving around. Many old-school ‘rivermen’ and game keepers would have no doubt cited these coarse fish, as the cause of the demise “Out competing our Trout”. The blame always it seemed, easiest attached to another living creature, which could then be eradicated with gay abandon, that being part of the job description of the game keeper and riverman, that, and being the fearful foe of the poachers.
( I’m too much of a whuzz, to be comfortable with indiscriminate killing sprees. And being any sort of fearful prospect, for any sort of foe, is frankly laughable).
When the Willow Brook club was formed and the stream adopted as a Trout fishery, the first plan and stated aim in the press release, was to wipe out the coarse fish and replace them with Trout. Whether they did I’ve no idea. It’s one thing writing about the intention quite another to describe the deed itself and no record was made.
They had as a club, netted Chub at some distant past date and transferred them to a water that had suffered a severe pollution event. But that’s more like charitable giving, than declaring a wholesale destruction. Unfortunately for future interested parties, there was no follow up to describe what happened to the remaining residents of the brook in their absence, nor how long it took for the balance to return, to help inform the choices of us future custodians.
Even when I first became a member of the club and the yearly AGM challenge was balancing the prospective stocking numbers based upon the latest disastrous and disappointing collective catch returns in from that season. People were talking regularly about wiping out the bigger Chub as the answer to our woes. There was no logic, no scientific basis, no consideration of how the ecosystem and the other inhabitants of the Brook would react and fill this void. It wouldn’t be with longer surviving stocked Trout that was for sure, they just perished from a lack the suitability to survive in the water and an inability to avoid predation.
No contemplation afforded, to the suggestion of someone regularly visiting the main pools and glides in the top two beats and tossing in fish pellets to keep them alive longer and settle them in. Like helping the new neighbors out with a cup of sugar till they learned where the local shops and the cash machine was.
I did suggest it, it seemed to make sense to me if they were going to continue to put stock-farmed, pellet-Pigs in. Feed them what they eat to sustain condition. But it was ridiculed as impractical and unnecessary in favor of killing big Chub, shooting more Cormorants and getting tougher on poachers… three completely unpractical proposals to dispense. As a policy of management it wasn’t so much on a “wing and a prayer” style, but more “let’s just kill and be damned”!
What they expected would be tougher on Poachers, I couldn’t guess. No one was going to be taking the law into their own hands that’s for sure, I can only imagine the solution was shouting “Go Away” even louder… and dropping the word ; Please, out of that request!
I also suggested at the time, if they seriously wanted to improve catch returns of those stocked Trout, there was a simple solution. Supply the members with fishing flies shaped less like natural insects and more like floating fish pellets.
It was oddly dismissed as if I had attempted to make a practical proposal, and was suggested that maybe they (the other members and me) needed to develop more fishing skills rather than relying on these hair brained schemes. Maybe later the penny dropped and it was realized that I was actually taking the piss of the ridiculous stocking policy, while attempting, and obviously failing, to be satirical.
Certainly at that time it seemed that there was only this one ‘mad-cap’ saying that the problem is more likely to be we are overstocking. But then I seemed to be the only member of the club, talking via on-line forums or going to phone or meet other river keepers to share their experiences, and being guided to the right research papers. Seeing where this stocking model had succeeded or failed for others, times were more informed and had moved on from what we were doing.
It seemed the one oracle the club questioned for insight and expertise was the owner of the fish farm. Who strangely recommended as a solution… we buy more of his Trout. Who would have seen that coming?
The consensus was, “lets add another 300 to the 1200, spread it over two stocking dates and roughly, to then apply to cull more of anything that wasn’t Trout”.
The other thing that was a bit silly to be brutally honest, was the bravado, those strong, resolute words made behind closed doors after a few beers on a cold November night in an AGM, were so remote from the reality.
Realistically if we could have been licensed to shoot 100 cormorants not 14 it would have made no difference to the outcome. Whether they are in the water or drying off over a public footpath you can’t make the low shot. Only flying over-head is the safe shot. And being there with a gun when that occurs is a stroke of luck. Despite the braggadocio of an old game keeper in the club in those days, no one ever saw him shoot a Cormorant, or any evidence of shot birds. The other members that went down with shot guns and tried, never hit a single bird in all the years we were licensed to kill.
No coarse fish were ever harmed thankfully, except a Pike. And I have to admit that was me!
A Pike had been spotted up above the mill. It had probably dropped over the dam wall from Apethorpe hall’s decorative lake. I searched it out, and caught it, well I caught a Pike from the area, whether it was ‘the’ Pike, is another matter. My paternal instincts to my precious Trout got the better of me.
I can plead that it was given to person who wanted to try eating Pike and it wasn’t just wasted. I hate culling. I’m not judgmental about others who do it, we live in an environment now devoid of its natural checks and balances.
But personally it makes me feel like I’m playing God, and am not worthy of making that call. Certainly Pike in a water like ours could be claimed to be a natural ‘check and balance’ with a valuable role to play. Killing Pike for the sake of our Trout was then, now that we have a more established Trout population and a fishing club largely on side, I feel less like it’s just me and my few precious wild Trout up against the world, it’s a less defensive and hopefully more tolerant Chris Avery now, I hope.
As for the coarse fish affect around Trout; a few observations, nothing that would stand up in court mind.
It seems when the Juveniles are around, and on a feeding station by a bank or under the food lane, the Dace tend to drop back and pick off what’s available that’s passed the Trout, they don’t dislodge the Trout, on the contrary, it appears the Trout are stationed in exactly where you were expect piscine Des’ Res to be, and all the other fish keep a respectable distance.
It seems a pattern when fishing your way upstream, pick up a few Dace in the more open water and above them , where the food lane over a shallow glide is concentrated by some cover… There will be a Trout, often not much bigger than those diminutive Dace, seemingly ruling that roost.
Even when a number of large chub shoal up in a productive food lane, you can often see a big Trout in amongst them picking off the choice cuts on the menu.
The coarse fish seem to suffer the Trout more than the other way round. And it’s the huge amount of fry from those coarse fish that probably fatten up our Trout and contribute to giving them the unusually quick growth rates. Removing them would only skew the balance for a while until the Brook again found its natural levels, or something else would prosper in the vacuum created. In what is realistically a Chub Water, my guess is that gap would probably cause an explosion in the population of smaller Chub until some natural Chubby equilibrium is reached.
If those ‘pesky’ Coarse fish were not blamed for the low numbers of Trout caught by the old style game keepers, the next obvious target would be predation and amongst thoseblamed and persecuted, Pike; Kingfishers; Otters; Cormorant; Herons; Mergansers; (and/or poachers). Again this seems to me, to be prejudiced old school gamekeeper logic and the answer again lies in killing the potential suspects and thus unbalancing the ecology.
The Kingfishers found on a Trout stream nesting in a shear soil bankside, traditionally had the entrance hole to the nest blocked up with a stone. When it comes to being a fish catching machines they are quite rightly called ‘king’. It takes 6 weeks to raise a brood of 6 chicks, they raise three broods in a year. We have regularly two pairs working the fishery. 4 Adults with 36 chicks mouths to be fed from one little Trout stream.
That’s 252 days of catching food to feed those broods between those 2 pairs per year ( and not accounting for the huge amount they catch themselves for snacking and just keeping alive). A pair needs to catch between 100 -120 fish per day to feed the six chicks. So to feed the next generation in our littlefishery over a season, 25,200+ fish are taken. That’s just raising chicks! Which sounds devastating.
Trout fry, lets remind ourselves live surrounded by cover in the margins, not in the open stream bed.
A renown BBC wildlife camera man rigged a camera by a kingfisher nest hole entrance on a river in the South west of England in recent years, and logged each visit by the parents over a season, noting the fish species taken in to the nest. The fish were almost exclusively of just one species.
Though they take Sticklebacks, Minnows, course fish fry, even Tadpoles and some big insects, their favored target is Bullheads. Bullheads live in and around the stream bed eating Mayfly and caddis larvae as well as fish eggs, all dining habits that are in competition or directly detrimental to our Trout.
Take away those Kingfishers from a Trout stream and the stress of the Bullhead population increases, reducing the available food sources and becoming a serious limiting factor in that numbers game, of eggs surviving life in the redds to successfully hatching, which is what so much of our river management is focused upon..
We just did a monthly kick sample for insects on WillowBrook, the Bullheads have hatched from eggs now from a few months back, and are a variety of sizes, we normally catch half a dozen fat adults in a small patch of gravel, or hidden under the Ranunculus. We had a few dozen bullheads from a few small patches of typical stream, let’s say from about two square metres of stream bed. They seem like individuals as they don’t shoal, but they are prolific in a stream like ours.
While I’m on a rant in defense of my beloved Kingfishers, did you know the feathers are actually dull brown? They do not have blue pigment. Ability to flash electric blue on the dullest of days, is not so much Bio-chemistry but Physics, via a phenomenon known as ‘Structural Colouration’. Using sugars, the cells of the feathers create a surface nano-structure that optimizes reflection of blue light from the sun, appearing as flashing electric blue in our eyes.
And then there’s the other scourge of the Trout stream; Otters.
When I first came across a family of Otters I kept it quiet from all but a selected few until I was sure that there was no reaction that could affect them, and engaged on a public relations front for them, feeling out others opinions before sharing the news. It’s not a ‘hard-sell’ anymore though, people are keen to see them and feel blessed when they have, it seems to be a badge of honour like having breeding Trout, that evoke an extra quality and special status to the waters.
In a stream where the population of Chub and Dace vastly outnumber the Trout, it’s much more likely they are feeding on the coarse fish numbers. The odd times I see a large unfinished meal on the bank its usually a large Chub or a rare Carp that’s somehow got in the system. Certainly a few local Carp populations have been wiped out by Otters. Ours seem to have a taste for large Swan Mussels. The Best PR for Otters was a photograph of one from a nearby river in Cambridge, heroically with a distressed Cormorant firmly in its jaws. We had a Mink problem years back and lost our water voles due to the Mink it was thought. Since the Otters return we now don’t see Mink, and the water voles have again appeared.
My personal understanding of the question at the beginning of this; “What had caused this population bottle neck” where a few generations seemed low in numbers, lead me to wonder that instead of blaming the other living creatures that shared our gaff, had there been a few bad years of breeding for some reason? Was it a cultural problem, a man made setback ? Had the gravels failed as Redds, excessive diffuse pollution, or, were we lacking adequate fry habitat for the hatchlings?
Bigger fish, sounds ideal for a fishery. But in a population which we know that Trout grow fast and only last four or maybe 5 years at most. Within a few seasons, with diminishing recruitment, you will have lost much of your breeding sized population, and could be facing population collapse.
As the season progressed and the nights again started to shorten each week I explored lines of thoughts and sought answers to this as I developed a growing urgency that we needed to make sure those gravels worked this year.
Had there been a catastrophic winter where the gravels and eggs had been washed away? Maybe this accounted for the build-up of gravels down at the Nassington Road Bridge?
We certainly had no shortage of gravel there now! Not that thebeds were suitable for Redds. But no, there had been no huge floods in my absence, and in any case I’ve seen the Brook at its highest levels, where it will take away trees and bank side fixings, but down on the bottom things seem to stay pretty calm and settled below those shifting waters, deeper down on the Stream bed.
Had the habitat contractors flow deflectors and bank revetment been at fault? No, I couldn’t believe that. A few badly positioned Groynes can clear some areas close by, it happens occasionally when the stream doesn’t react as you expect. But this would have a least been counterbalanced byall the many improvements he had created. This failure was despite his fine works it seemed
Typically in a stretch of stream like this lowest beat. We may see half a dozen or more spawning grounds used as Redds, a few of them will seem to be prime spots that get most of the attention. And a few arears the Trout will spring a surprise on you and discover a hidden gem.
One of these prime spots each year seemed to be the Willow brook Trout’s favorite postcode, that I could always expect to see activity on. So I started my search there.
It seemed instantly changed from my memory of the place, the gravel beds that stretched across the stream now seem concentrated on the main hump that had taken most of the previous spawning activity, but there was much less of it to be seen. Working down with my boot I soon passed through a remaining thin layer of gravel into solid ground, was this silted up compacted gravel? I couldn’t tell. The Water height was right as was the flow speed, but there was no depth to the usable gravel, the stream around was now silt and weeds. It was a depressing state.
Had the gravels gone, or had they become silted up and silted over? I suspected the former, but had no way at the time of determining the answer.
I decided there and then to survey the entire stretch, and carefully note each potential Redd site that we could work on cleaning up, and started making enquiries about the motorized pump and tubes that had been entrusted to us by the Wild Trout Trust.
No one was very forthcoming with the answer, there was much buck passing and it seemed no one was beyond lip service in helping me trace its whereabouts.
As for the answer to the gravels themself and my complaint that they seem to have vanished from a few areas and become silted over, again, I was met with silence. Weird in a club with many opinionated gobshites, no one was offering anythingback. Almost like an elephant had appeared at the time it was frustrating, only later did I realise how strange people were reacting and should have suspected something un-fishy.
I decided to brush up on my ‘Surveying for ideal Redd’s’research and find a helper on the bankside while as searched as many inches of the Nassington road bridge beat as I could cover and answer the question, “What the bloody hell has happened to our gravels”?
All the best!
Chris