Over the last few weeks, I've been talking with Francis Yarrow of the Norfolk and Norwich Naturalists Society.

Eastern Daily Press: Guineas of Gold – crucians about to be restocked. Picture: John BaileyGuineas of Gold – crucians about to be restocked. Picture: John Bailey (Image: Archant)

He's involved with Project 150, an idea to honour the 125th anniversary of the society. The object is to look at 150 fascinating and noteworthy Norfolk species that sometimes don't grab our full attention. Francis very kindly consulted me about the question of the burbot, or more accurately the burbot's demise.

So what is, or was, a burbot? I suppose, in non-scientific terms, a burbot looks a little like a mottled eel in so far as it is long, thin and bottom dwelling. However, it's a member of the cod family, growing abnormally well into double figures. Despite its family grouping, the burbot is a freshwater fish, and sometimes called the eelpout here in East Anglia.

It is, of course, the East Anglian eelpout that has concerned Francis, me and many anglers over the last half century or more. Back in the 19th century and before, the eelpout was hugely common. There are all sorts of stories of it proliferating in the Yare, the Thet, the Ouse and all through the Fenland drains. And that's just for starters. I'm old enough to remember talking with old men then, back in the 1960s who presumably had been born in the 1880s. These old-timers told me that burbot were then as common as eels. They could be netted, speared and caught on long lines and sometimes in such numbers they were simply fed to the pigs.

Certainly, until the First World War, or thereabouts, there was little concern for the future of the burbot. However, the burbot could already have been in trouble. What records there are suggest that numbers were falling by the Second World War and it is probably the last burbot ever seen alive in East Anglia was taken from the Cam, I believe, in 1969. During the 80s there was talk of burbot being seen here or there and there have been even more recent reports, but all uncorroborated. I think most of us would agree that the burbot has gone AWOL for at least half a century. The whole question is why?

Eastern Daily Press: Dr Carl Sayer has worked tirelessly to bring crucians back to East Anglia. Picture: John BaileyDr Carl Sayer has worked tirelessly to bring crucians back to East Anglia. Picture: John Bailey (Image: Archant)

Francis and I enjoyed a half-hour conversation only recently covering all the possibilities of this most extraordinary debate. Could global warming be the reason that burbot have declined? It's true that burbot today seem to flourish in the cold waters of Finland and Scandinavia and throughout Siberia. However, those of us remembering the winters of 1947 (I don't) and 1963 (I do) might rather dispute this idea. I'm not sure there is any real evidence that East Anglia was noticeably warming up in the 1920s or so.

Obviously, pollution could have a lot to do with the end of the eelpout. Certainly new insecticides and agricultural chemicals appeared after the Second World War which could have had a disastrous impact in the type of waters that the burbot favoured. I think it is fair to say that most fish species began to suffer during this period and it's possible the burbot was particularly susceptible.

Fish species do, from time to time, suffer from various killer viruses. Many of us will remember the perch disease of the 1970s which nearly wiped perch out from all our East Anglian waters. The decline of eels has also been largely put at the door of a mystery virus. Perhaps the eelpout went the same way but more dramatically so.

Perhaps predation was a problem, but I can't think what was new on the scene to destroy a species that had been eternal. Or how about over-fishing? Perhaps the pigs were just overfed? My own view is that perhaps dredging had something to do with it. After the Second World War, deep dredging became the norm. It could just be that the habitat of these bottom dwellers was destroyed, mile upon mile, with no chance of recovery. I don't know, nobody knows, but that's where I put my money.

I don't want you to think that the end of the eelpout is just a fanciful debate. It's not. It's an example of how an under-rated species can disappear off our radar without anyone barely lifting an eyebrow. We are seeing the same thing with our fish species today. Where, for example, have wild carp gone over the last half century? These ancient carp survivors from mediaeval times really are on their last legs. When did you last catch a long, lean, grey common carp that went like a torpedo? How many ruffe have I caught in the last 40 years? Not a single one. How about you? And what about bullheads? Forty years ago, if I rummaged under the stones of any East Anglian river, I'd find them in profusion. I spent a couple of days looking for bullheads in August last year and drew a big, fat blank.

Most worrying of all, our beloved crucian carp nearly bit the dust this century. Fortunately, Dr Carl Sayer of University College London came to their rescue and down to Carl's work and that of his myriad helpers, the crucian seems to be thriving again.

A last word on the burbot. Once, on a trip in Siberia, my fellow anglers and I were so hungry we set about catching burbot to eat. A burbot fights like a branch. It looks like a streak of sludge. It tastes like wood pulp. The only good news I can think of is that if we had to lose a fish species, I'd forever vote for the vanishing burbot.