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Reasons for Barbel population decline

At the end of the day, its all conjecture as I said previously, we are not scientists, but our opinion is valid, because we spend more time on the bank than the scientists....so lets hope there will be a meeting of the minds...soon!
 
Lol

There was a definite decline in fish after those long long Floods on the Kennet. What was unusual was that they were Summer Floods at spawning time.

I think Rob Swindells also noted the significant decline on his and DM's Teme bit.

However, this is not the cause of our real problem. One thing I will say. It started at least 10-15 years ago because of the dearth of small fish.

Predation will have an effect BUT not on the scale we are seeing.

Oy Darren, was that OP for Old Person or worse!:rolleyes::mad:;)

Graham
 
Mike Hodgkiss said:
Hello Jon . Out of curiosity , are many otters sighted on the Trent ? I read the river reports and don't recall any mention of the blighters
Click to expand...

I dont know a great deal about the middle trent otters. But they are certainly evident on the tidal stretch with footprints and the odd siting. Personally there might be an handful on the tidal river thats all. There could be more on tributaries especially the Idle.
 
Yes. Agreed. We should see if the Females are carrying viable spawn. Who?

Yes we should discover more about the Initial fish Farming Pellets and have any original EWOS elips analysed..Who

Graham
 
Lawrence Breakspear said:
It could mean Neil that the bigger females no longer have the protection of the shoal, because the decline of the greater numbers of males and become more vulnerable to Otters, thus giving the impression its all the otters fault, maybe it is, maybe it isnt. With the EA stocking Barbel in their 1000's and not having a clue what sex they are, they could be adding to the problem.....maybe?
Click to expand...

If the requirement is at least 7 to 1 for spawning then a reduction in male numbers would be a potential problem, I suppose then that nature would favour male development over female. Just how you sex fingerling barbel I don't know, perhaps all barbel are asexual until a certain age? I need to read up some......and just when I promised the missus that after the 14th I was at her disposal .:)
 
You can age the Barbel, and asses its growth rate (i.e. its size) and this could show if its male or female, with the female being slightly bigger for its age but only on bigger 1lb plus fish, I think....thats how Calverton does it, I bit Heath Robinson I know...
 
Been following this for a while now really interesting.
Is there really no identifying features between male and female barbel apart from size ?
With other species of fish there are distinguishing features ie: fin shape,colour etc
But if I had 2 different 7lb barbel no one could tell me if they were male or female without taking scales and determining age
Surely even then that wouldn't work as sometimes fish have greater growth rates due to ecological reasons such as availability of food natural or otherwise during different periods of their life.
Not being negative but if we can't tell the difference between male or female barbel In our rivers we are never going to determine whether there is a problem with the stock.
Seems strange that we saying 7lb fish are male and all doubles are females when no one seems to really know.
Why can't some of these large doubles be males ?
Also with carp different strains like leney dinks or Simmonds are easily recognised with barbel this doesn't seem to be the case so this is also a problem with determining how well stock is doing unless fish are tagged to record growth and even sex maybe
 
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Dear Graham,

There has been a tremendous amount of research undertaken on this subject with huge amounts of scientific papers written and available for download so I'm surprised you can't find any?

What you need to be looking at is the synthetic steroid 17α-methyltestosterone (MT)that was used as a feed additive to produce predominately male populations of fish.

Also for your information;

The river Trent, almost certainly the finest barbel river in England today, enjoys superb recruitment for barbel and all species of fish containing a wide range of year classes for all fish. Over the last 15 years at least, the number one bait employed for barbel fishing on the Trent has been pellet in a range of forms and brand names as sold by the bait trade. The reality however is that for all the different brand names as sold by the bait trade etc, there are relatively few fish feed companies. I have no doubt what so ever that Trent barbel have gone from strength to strength even though the number one bait used has been the pellet.

Here is some information on the largest fish feed company in the world who have been trading for 40 years;

Skretting the company, has operations on five continents and produces 1.3 million tonnes of feed annually, for more than fifty species of fish. Skretting is a wholly owned subsidiary of the Nutreco feed group, which is listed on the stock exchange in the Netherlands.

Skretting has around 1,300 employees world-wide and production takes place at seventeen production plants in Australia, Canada, Chile, France, Ireland, Italy, Japan, the U.S., Norway, Spain, Turkey and the United Kingdom. These plants produce feed products sold worldwide. Skretting’s head office is located in Stavanger, Norway, where both the Norwegian and international management are also located. Skretting’s international research company, Skretting Aquaculture Research Centre, is also located in Stavanger.

Skretting ARC’s core competencies are within fish and shrimp nutrition and health, feed raw materials, feed safety & quality and feed manufacturing processes. Skretting ARC’s facilities include an extensive research station with hatchery and land based tanks with both fresh and seawater trial facilities, a pilot plant for test feed production and innovative process trials and a well-equipped modern laboratory. The research station is designed for running trials with salmonids through all life stages with different water qualities (temperature and salinity). Facilities are also adapted for running trials with cod after metamorphosis. Main facilities are located within the vicinity of Stavanger, however Skretting also has a trout facility in Italy and is working towards a facility in Asia. In addition, Skretting ARC collaborates with several universities and institutes around the world.

Skretting ARC has participated in several Norwegian Research Council and EU-funded research projects over the years. Its researchers have been authors or co-authors of several scientific publications. Some examples of EU projects are:
SELFDOTT (Self-sustained Aquaculture and Domestication of Bluefin Tuna Thunnus thynnus)
AQUAMAX Sustainable Aquafeeds to Maximise the Health Benefits of Farmed Fish for Consumers
GLIP (Grain Legumes Integrated Programme)

I have had dealings with Skretting UK and they are very helpful at all levels. A simple phone call made to their offices will get you all the information you require concerning the various products they produce plus any specific data you require concerning their products. You can reach them here;

HEAD OFFICE
Wincham
Northwich
Cheshire
CW9 6DF
England

Tel: (01606) 561090
Fax: (01606) 49869
General enquiries e-mail: info.aqua@skretting.com

Skretting are a huge global company with a huge reputation and as such are very serious about fish health and welfare.

Furthermore, I'm sure Alan Henshaw of EA Calverton Fish Farm will also furnish you with the relevant information you require concerning the effects on wild barbel stocks via aquaculture feeds.

Regards,

Lee.
 
You can sex mature barbel by looking at the vent, near the anal fin; females have a fleshy protruding tubular vent, males have a single small hole flush with the skin, but the smaller the barbel the harder it is to see.

At one time Calverton selected the larger fish for some stockings, but as far as I am aware now stock the whole size range from that year class to ensure no sex selection occurs.
I do not think it likely that the sex ratio will vary much within stocked fish anyway, and have any real effect of spawning success.

Far more likely candidates for poor spawning success and recruitment are the obvious ones of poor habitat linked with low flows; barbel need plenty of clean gravel and clean water flowing over it to spawn successfully, plus refuge areas for fry to develop and over-winter in safely.

A combination of other negative factors, such as predation on fry by crays,algae choking eggs, unseasonal flood events, will all play a part in limiting populations.
There will not be a simple answer to what is a very complex question, but interesting to discuss all possibilities.

Hampshire Avon is full of tiny barbel this year, with baby fish from the last two years of spawning in great abundance, so something was right recently; be interesting to see how many survive in the next few years.
 
Gary Cream said:
Been following this for a while now really interesting.
Is there really no identifying features between male and female barbel apart from size ?
With other species of fish there are distinguishing features ie: fin shape,colour etc
But if I had 2 different 7lb barbel no one could tell me if they were male or female without taking scales and determining age
Surely even then that wouldn't work as sometimes fish have greater growth rates due to ecological reasons such as availability of food natural or otherwise during different periods of their life.
Not being negative but if we can't tell the difference between male or female barbel In our rivers we are never going to determine whether there is a problem with the stock.
Seems strange that we saying 7lb fish are male and all doubles are females when no one seems to really know.
Why can't some of these large doubles be males ?
Also with carp different strains like leney dinks or Simmonds are easily recognised with barbel this doesn't seem to be the case so this is also a problem with determining how well stock is doing unless fish are tagged to record growth and even sex maybe
Click to expand...

The way Calverton calculated smaller Barbels sex, as Ray Walton was told, they would be both the same age, but the female would weigh slightly more and measure bigger, as fish become bigger and start to develop milt or Ova then it becomes easier, then once they get over 10 pounds, they will normally be female as in all species of fish, Barbel males maximum size is about 7 pound, though I am sure there will be exceptions to the rule
 
Thanks Lee.

I looked at EWOS.

Strange that the research I did indicated that the desired effect was to produce female salmon.????

I am not convinced all producers detailed all their products unique advantages though.

However. STEROID MT. When fed to mixed sex fish it had the following effect on females

Concentration-dependent reductions in egg number, fertilisation rate and increases in abnormal sexual behaviour in females were observed.

Graham
 
I was there at Calverton helping Lizzie Rhymes mark the barbel with the orange spot Howard, just after we had marked a few thousand for stocking into the Dorset Stour.
We used blue, green and red spots, for three different stocking sites.
Do not know how they prospered in the Upper Thames, only a few have been spotted on the Stour, but these stockings can be very hit and miss, and very difficult to monitor.
Sometimes the barbel just turn up almost out of nowhere after a few years, sometimes it just does not work.
 
Pete I think the vent difference doesn't occur until well after what we call the fingerling size and research papers show that that the correct male to female ratio is essential (in the wild) to successful spawning, thats how nature created it, but you are right the correct environment is also critical, and bear in mind there are no signal crays in the Teme.
 
Mark, I have had a few thoughts about Calverton and the baby barbel they are producing and I think this is well worth getting an answer from the people who work there.
The water that enters Calverton has a consistent temperature of 9C, they then warm this water to the individual requirements of each species.
As the sex of many species is temperature related I wondered if they are producing just female or mainly female fish.
From what I can work out, barbel need a temperature of between 14-18C to spawn, and need approximately 180 degree days to hatch, which means 10 days at 18C or 14 days at 14C, approximately that is.
So if at the lowest temperatures only females are produced and at the highest only males (or the other way round) this will obviously have far reaching effects on the long term populations of the rivers they are stocked into.
Barbel spawn most successfully when there is a male to female ratio of 3-1, the females need just that many males courting her to" get her going" so to speak, any more or less just doesn't do it for them.
So if at least the majority of fish reared at Calverton are female it will unbalance the species natural spawning cycle.
If what I say is true regarding temperature and the sex of a fish, then the temperature of our rivers will most often produce males towards the ratio that I mention.
So if rivers such as the Ouse and Wensum are or have been stocked with mainly female fish and considering the rarity of fish below 8lbs (large fish are female) this could well be the case.
People often say that on some rivers there are insufficient spawning sites, I think this may well be incorrect considering for example the work carried out at the Wensum to create such areas and yet the fish there still do not spawn successfully.
I do not think Calverton are producing sterile fish but there is a chance they are producing the wrong ratio of boys to girls.
Anne xxx
 
I have done some further research following Lee Fletchers info.

Although Lee talks about turning fish to males it seems that the MT has been proven to actually cause total sterility in male fish in tests on grass carp and common carp as well as trout.

I wonder what level of of steroids we introduced to the food chain!

Is it time to take a serious look at this???
 
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