Information Page.
Cod and grayling.
Over the past week a couple of things came to my notice. Firstly there was a little leaflet written, by one of my ex-students and colleagues Anton Ibbotson, for the Grayling Society, Environment Agency and CEH. I'm sure that you will be able to get hold of a copy from your local branch of the EA if you fancy a read but I'll mention a few snippets to whet your appetite.
Grayling are wonderful fish. They have so many unique characteristics that they are unmistakeable - the smell of thyme in the slime, the teardrop shaped eye, the great coloured flag of a dorsal fin and the undershot mouth for starters.
In England grayling are a relic of the last ice age and in many parts of their range they are under threat from overfishing and pollution. My own experience of management techniques consist of seeing thousands upon thousands removed from rivers, as vermin, by trout fishing clubs. It never seemed reduce the numbers. Dr ibbotson suggests that grayling removal may have a negative impact on the fishery. Culling simply reduces the average size of grayling with no effect on the quality of the trout fishing.
I always knew that grayling were 'delicate' fish and needed careful handling but apparently because they have quite a small liver they are susceptible to poisoning by pollutants and this makes them better indicators of water quality than many other fish.
Seemingly grayling migrate long distances to spawn and in Norway they have been tracked on journeys of up to 75 miles. On a smaller scale they are known to shift from deep water in the daytime into shallow slow-flowing stretches in the dark.
One of the biggest surprises to me related to the size of grayling. I'd always thought that grayling in the rivers of Finland, Sweden and Norway reached huge sizes. However, it seems that this may have been a case of mistaken identity and the big fish were probably 'whitefish'. The grayling over there attain weights of about three pounds, just as they do here.
Anyway there is lots of good information in the leaflet (It's called "Grayling, the past, the present and the future.") So grab yourself a copy or, if you're really keen why not join the Grayling Society, c/o 7 Oaktree Way, Little Sandhurst, Berkshire, GU47 8QS. (I'm not a member myself so I've no axe to grind here).
The other bit of info. that came to my notice was about cod.
It was from a paper by Canadian scientists and dealt with the long term crash in the Newfoundland (Northwest Atlantic) cod fishery. Now it is well known that these cod stocks were seriously overfished and despite severe catch restrictions being imposed have never really recovered (a sharp lesson here for our own politicians and commercial fishermen!). Now the cod is a quick growing species and produces millions of eggs (unlike bass or mullet for example) but has clearly been unable to make good the deficiencies following overfishing. WHY?
It seems that there are twelve Northwest Atlantic cod stocks and the main contributing factors to the ongoing stock failure are increased natural death rates, slower growth, and reduced numbers of young fish recruited. However, a key influence which was apparently unknown before is the effect of fishing pressure by boats seeking other species. In other words the bycatch of cod is sufficient to keep stocks down and not only should they have stopped cod fishing but also other types of commercial activities in the area. Let's hope our fisheries people get the message.
If you have any comments or questions about fish, methods, tactics or 'what have you.'get in touch with me by sending an E-MAIL to - docladle@hotmail.com
INFORMATION SPOT
Grayling and cod.
Effect of grayling removal.
