Friday, November 7, 2008

Week 44

Week 44

A grey gloomy week for weather after our week away, fish, pheasants and dogs all in good order after a week in the hands of my parents. The dogs especially resigned to having to return to their place back on the dog bed after a week sitting on the settee with their Nana and Grandad.

The Brown trout in the river are now on the shallows and starting to kick up their redds; the Cock fish in particular looking and behaving in an aggressive manner as they jockey for position on the gravels next to the gravid females. Fish at this time of the year are particularly susceptible to fungal infections, a cut or scratch sustained while scraping a Redd or battling with a Cock fish easily becoming infected. If the fish is fit and healthy it has every chance of overcoming the infection and recovering; if a little under the weather or in poor condition the infection can take hold and ultimately kill the fish. The Redds are easily identifiable by the clean gravel exposed by the fishes digging, and every year the fish cut redds in the same places. The water must be fast and the gravel suitably loose, the hen will then lie in the scrape accompanied by a male/males express her eggs at the same time as he expresses his milt, any fertilised eggs becoming embedded in the pile of gravel at the rear of the scrape, it is incredibly hit and miss, a female Brown Trout will express several thousand eggs of which only a few will be fertilised.

I have also stripped some fish from the stew ponds and laid the eggs down the hatchery trough. This involves holding the female fish by the tail and firmly pushing down along her belly towards the vent to express the eggs. The eggs are yellowy orange in colour and between four and six millimetres in diameter. Three or four females are stripped into a bowl before the boys come on the scene; the cocks require a little squeeze by the vent to express a jet of milt into the eggs. The egg milt mixture is then mixed gently to ensure that all the eggs are fertilised and left for just over a minute. Pouring water in and out of the bowl before the eggs are left to swell up for ten minutes then washes off the Excess milt. The stripped fish are placed back into fast running water to recover and the fertilised eggs moved to the Hatchery, where they are laid out in baskets in a shallow trough of water with spring water flowing through them at a constant ten degrees centigrade. This process is simple and natural and produces normal male and female Brown Trout that we use to stock the river. Triploid Trout production and all female Trout production involve a slightly different procedure. For Triploids the eggs are submitted to either a high-pressure treatment or temperature treatment around twenty minutes after fertilisation, this interferes with normal embryonic development at the eight cell stage and results in a sterile fish. All female production requires the use of an XX male for fertilisation, these are female fish that have been fed a diet of methyl testosterone for a specific period resulting in them developing testes and male characteristics, they are however unable to express milt and must be sacrificed in order for the milt to be used to produce all female progeny.
We have our first day shooting next week, so I have spent some time trimming branches along some of the rides where the guns will be standing, the Ducks continue to pour onto the pond at night along with about half a dozen cormorants. We have also had a few Grayling fishermen over the past week who have caught several fish up to two pound. I think we have an Otter back on the scene and it may be necessary to improve the predator protection around the stew ponds.

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