Not sure how this will turn out but here we go anyway
So what are EDSs?.
EDSs are substances that can, and do interfere with the hormonal system of fish.
The Endocrine System and how it work
The endocrine system consists of endocrine glands in the body of higher organisms. There are nine in the human body - hypothalamus brain thyroid gland throat testis are to list three in particular. Each gland releases hormones (a chemical message produced by one set of cells that affects other sets of cells) directly into the bloodstream. The hormones then circulate in the bloodstream until they lock into the target cells, much the same as a key fits a lock. An example of this would be testosterone released by the testes that has many functions (Saturday night fighting stuff this, in young males after 10 pints of lager) thought to be responsible for sex drive and muscle formation amongst others. (Apologies to the biologists and physiologists for over simplifying this section.)
The take away point, is that hormones operate in a lock and key procedure and are target specific. The hormone being the key and the receptor cell being the lock. Suffice to say that a particular hormone will only fit the cell or group of cells that it is intended for. The understanding of this principle is critical to what follows.
How EDSs Work
EDSs act as false hormonal keys (hormone mimics) and/or hormone blockers that enter the cell and stop the true hormone entering the locking mechanism. In regards to fish, the effect this has is to block and/or stop the femininising or masculising process. Suffice to say, they feminise males and masculinise females.( known as intersexing) The evidence for this manifesting itself in the form of males showing signs of egg formation and females developing rudimentary testes development.
Effects on fishlife
There is now overwhelming evidence starting to emerge that intersexing of river fish is a reality, along with other aquatic life forms. American studies have found intersexing in turtles, alligators, otters, birds as well as fish. At a recent meeting I attended, it was stated that of the rivers tested by the EA, "Not a single river showed signs of no intersexing in the fish stocks analysed." The problem being most acute down flow of any sewage discharge points. With a 30 - 100 % totality of samples.
You don't have to be a genius to work out that on the heavily urbanised river systems with many sewage outflows and other point sources, the whole river and stock may be affected. The cure lies in the removal of EDSs from the whole environment and not just the water environment.
Postscript
Whilst this article is perhaps depressing to read, there is some light at the end of the tunnel. The EA are drawing up Environmental Quality Standards (EQSs) for some of the known substances. They are also committed to what is known as the UK's Biodiversity Action Plan for Sustainable River Systems (includes fish). In my view, their effectiveness on both counts will only be as good as the pressure we bring to bare on them.
You know the script, Write to MP, MEP, Sec. of State. Presscot at DETR. and Blair if you like. The louder we shout the more notice and action we'll get.
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