If you have anything to do with fisheries or if you have any fishy business in mind, I'd heartily recommend you contact Steve Barnes of Quiet Sports Fisheries, writes John Bailey.

Over the years I've known him, I've realised he is a fount of knowledge and experience with something ever-new to pass on about the waters that we fish.

It was with relish, therefore, that I looked forward to working with Steve the other day. The task before us was to net a small lake of less than an acre to see exactly what the stocks of fish in there were up to.

For years, the water had been very prolific but, of late, there have seemed to be fewer fish of fewer species and Steve was called in, along with his nets and his electro-fishing gear, to give a realistic assessment. Steve and helper Ben were their usual ultra-professional selves. They netted the open water comprehensively and then electro-fished the thick weed beds with military precision.

As we'd expected, the carp were still there in the water, and in some numbers. Moreover, they were in fine, late winter condition, burnished with deep mahogany coloration. One or two exhibited old otter wounds but, thankfully, these were well-healed and evidently the carp were thriving.

The rest of the survey does not read quite as well. After a hard day, Steve produced two roach of size, a single one-pound tench, three or four small jacks and three very tiny perch. We also proved that the reed beds were full of sprat-sized silver fish showering away from the boat in large numbers. But, I repeat, these really were miniscule fish.

The lessons I think are interesting for everyone who fishes stillwaters. Above all, it is fascinating to reflect that virtually all the fish that Steve produced on the day came from the area of the reed beds.

You might have expected fish to be lurking in the overhanging alder trees that surround the water, but these were completely barren of fish as well. The answer is obvious. If you are fishing over the next few weeks on any stillwater, fish as close to any reed beds as you can.

Just a few years back, I'm quite sure Steve would have turned up some large perch, numerous tench and some very decent roach. To all intents and purposes, it seems that these fish have been completely eradicated from the water in question. Steve was so meticulous and so thorough that he feels sure these would have shown during the course of a long day's work. We have to assume they are no longer with us. Even the pike numbers were unexpectedly low.

Let's play nature detective. Perhaps those fish have been stolen. I feel this is highly unlikely. The lake is in a private estate and well-keepered.

We did find a cheap, old telescopic rod in the net after one haul and this could have been thrown away hastily by a lad from the village, perhaps. However, I think we can rule out large-scale poaching.

Perhaps the fish have simply died out. Big perch, as we know, come and go with depressing regularity. However, this does not really explain the absence of decent roach and the almost complete blank on the tench front. Tench populations do wind down, but not as quickly as this one has.

The only other possibility here is the effect of predation. We know otters pass by regularly and presumably they're not in the lake for swimming practice. However, the carp that we caught did not exhibit any signs of fresh otter damage so that's a question within itself. Would the otters just target the tench, the roach, the perch and the pike?

More likely, we lost those fish over three or four years to cormorant activity. We frequently fail to understand the size of fish a cormorant can cope with. Certainly jacks of two pounds pose no problem and that one pound tench could certainly have seen his brothers and sisters disappear down those rapacious gullets.

Or again, perhaps it's a mix of all these elements. Perhaps some fish have died off naturally. Perhaps even one or two were nicked by local lads. Perhaps otters have had some and cormorants the rest.

At the end of everything, what this does reveal is the fact that water and nature are ever volatile and you can never take anything for granted. You constantly have to be alert to any changes that might be taking place.

Everything can surprise you. For example, there was a nice segment on Countryfile a week or so back regarding the return of great crested grebes to our waters. Well, they're not really as common as you might expect on my waters and that's because a good number are eaten on a regular basis by the otter population. When I contacted Countryfile, they did not want to know about this piece of information. It seems they're quite content for their view of nature to exist in some sort of idealised bubble.

We as anglers must be more realistic and days like this with Steve show we have to be constantly alert to what is happening around us.