MARK WINTLE

Mark Wintle, an angler for thirty-five years, is on a quest to discover and bring to you the magic of fishing. Previously heavily involved with match fishing he now fishes for the sheer fun of it. With an open and enquiring mind, each week Mark will bring to you articles on fishing different rivers, different methods and what makes rivers, and occasionally stillwaters, tick. Add to this a mixed bag of articles on catching big fish, tackle design, angling politics and a few surprises.

Are you stuck in a rut fishing the same swim every week? Do you dare to try something different and see a whole new world of angling open up? Yes? Then read Mark Wintle’s regular weekly column.


The Lower Stour

CHUB POPULATIONS IN RIVERS

1959, 1975, 1976, 1984, 1990, 1995, 2003. What is so special about those years? And what is the significance of them for the chub angler? All hot summers. There have been other hot summers but there is some evidence that these years were exceptional spawning years for chub in our rivers. In the long term, many other factors have an impact on how well a particular species does over time, including pollution, weed cutting and predation. I am going to look at how the influence of these hot summers has affected the chub population of the Dorset Stour and Hampshire Avon. The other question I want to try and answer is why are chub getting so much bigger?

Chub Class of ’59 on the Stour

Why do we, as coarse anglers, need to know the long-term effect of these good spawning years? I believe that, within reason, it is possible to predict future trends based on what has happened in the past and using knowledge of fish life spans and growth rates. In the early 1970’s fishery scientists discovered that many large chub present in the Dorset Stour had been born in 1959. They predicted that in time the dominance of this year class would pass. By the early 1980’s large chub were much fewer than had been the case a few years earlier. This does not mean that large chub were non-existent simply much rarer than before. After all, chub were still being successfully spawned in the years after 1959 but to a less dominant extent. Anglers spoke of a river in decline and told of the good old days when five and six pound chub were landed.

Remember 1976? And 1975?

But the foundations for a revival had already been laid with the twin good spawning years of 1975 and 1976. With no floods over the winter of 1975/6 fry survival was high. By the end of the seventies the Stour started to fill with young fast growing chub. A decade later these fish were hefty four pounders with a good sprinkling of five pounders. The chub were back. My own diaries record catches of up to 14 chub in the late eighties/early nineties. These catches included up to seven over four pounds with an occasional five pounder, yet by the mid-nineties bags of good chub were rare on the Stour. Dave Slater reckons that bigger chub (including fish over 8lbs) were present at this time but very difficult to catch due to the way chub behave in big shoals. The real giants use the smaller shoal fish as ‘tasters’ to check out what is on offer. The capture of the smaller shoal fish triggers the giant’s suspicions so it simply melts away. Recently I have seen shoals of middleweight chub (2-4 pounds) at a variety of venues on the Stour.

Chub are growing faster, much faster, and fatter


Giant chub
In 2003 it is unlikely that many chub survive from 1975/6 but it is possible that today’s monsters of seven pounds plus are fish from 1984. In time they too will pass and we will hopefully see a new class of super chub that were born in 1990, and eventually those from 1995. According to the latest Environment Agency survey (1998) results a Stour chub of about a pound is six years old, and one of four pounds about 12 or 13 years. But when the previous survey (1992) was taken, chub took four years longer to reach a size of 20 inches (a nominal 4lbs). This demonstrates that chub are showing a substantial improvement in growth rates achieved in a relatively short period (less than a third of their life span). Chub appear to reach their maximum size at about 18 – 20 years old and can live several years beyond this. The EA surveys have not confirmed chub growing or living much beyond this though a life span of thirty years must just about be conceivable. Until the next survey is published, (probably due out in 2004) we won’t know whether this trend is increasing or stabilising. Another observable feature is that chub have once again become the stout fish of old and live up to their name. So, we have a double effect of chub of a set size not only being much younger than previously but also heavier for the same length. There are far fewer long lean fish and far more short deep fish. Length, girth and weight readings bear this out. Some exceptional fish of less than 20 inches have exceeded 6lbs.

Why are they getting bigger?

The consensus is that a combination of decreased competition from other species, more food in the form of highly nutritious anglers baits, and most importantly a longer growing season from a warmer climate have all contributed to increased growth. It is my belief that the longer growing season has a double whammy effect. How? If a fish previously was able to grow for seven months and hold steady for five months, and now is able to grow for ten months and hold steady for two months then not only is the growing period greatly extended but also the drain on the fishes’ reserves is considerably reduced. The growth check caused by spawning is a constant factor. This increase in growth rates is exactly mirrored on the Hampshire Avon.

Signal Crayfish

Further afield on the Kennet, Thames and Great Ouse, there is conjecture that huge increases in available food as a result of population explosions of signal crayfish has also contributed to the growth rates of chub in those rivers. Huge chub are turning up from many other rivers that certainly don’t have signal crayfish in them. I therefore believe that the extended growing season is more likely to be the reason for the increase in size. One thing that I have discovered about signal crayfish is that eventually the population crashes. Signals were stocked into some of the Ringwood pits many years ago. Though still present, it is now very rare to see one, a far cry from their bait-robbing days. Apparently, the fungal disease that they carry not only wipes out the native crayfish but also eventually causes a massive decline in their own numbers. I’d be interested what others think about this.

The Avon situation

Because I didn’t fish the Avon to anything like the same extent as the Stour during the eighties I don’t have such a clear picture of the Avon chub population. What is clear though is that there are some truly huge chub currently present in the Avon, with a number of seven pounders and possibly eight pounders. Again there are the shoal fish of three to four pounds though not in great numbers. The last time fish of this size were about in big shoals was in 1999, since then they are much fewer in number. At present I am at a loss to explain what happened around that time. My own catches dropped from 10 to 12 chub from very good swims and three to four from any swim to three or four chub from the very good swims and hardly any anywhere else, and that’s how the situation remains three years on. What also seem to be absent at present are the small chub, the ones from four ounces to a pound, and this is worrying.

Hookworm problems in the sixties


Hookworm
There are several factors on the Avon that are different to the Stour. Way back in the sixties through into the seventies chub were especially badly affected on the Avon by a parasitic hookworm (pomporynchus laevis). This orange maggot-like grub used freshwater shrimps and snails as intermediate host. When the chub ate the infected shrimps/snails the parasites developed and attached themselves to the gut of the chub. A chub could be host to hundreds of these hookworms. The draconian weed cutting of that time made these shrimps easily available to the chub. The result was emaciated chub highlighted by Dick Walker (see picture of chub dissected by Walker). Fish that ought to have weighed five pounds struggled to make three. A gradual change in weed cutting practice, fought for by Pete Hutchinson, Pete Reading and Gerry Swanton, eventually turned the tide, and this parasite no longer affects the chub (or other fish) to the same degree. Latest practice is to almost eliminate weed cutting. Whether otter predation is having an impact is also not clear on the Avon, certainly barbel and big roach have been taken in some areas, and cormorant predation is getting worse not better. Trout farming is another fly in the ointment on the Avon. This has two detrimental effects; firstly the effluent from a large farm is equivalent to the sewage effluent from a large town, and secondly the many escapee rainbow trout annihilate coarse fish fry.

What of the future?

There would seem to be enough middleweight chub around to supply the future leviathans. It is possible that we may have a blip when the current monsters die of old age so that, and this is pure speculation, for three or four years there is a dearth of very big chub (7lbs +) not that they are that common anyway. Whether sufficient small chub will make it through to be the middleweights and giants of the future remains to be seen.

What do you think?

I have floated a number of theories so what do the experts think? What will happen on the Trent, Ribble, Lea, and Thames etc, in five years, ten years time?

NEXT WEEK: ‘Summer Chub on the Float’

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