Angling Times This Week

[Worms]

Hi Nick,

 

So a heron weighes 5 - 8 pounds, a goosander around 5 lbs and a kingfisher merely 35 - 40 grammes. Whats the comparison?

 

A heron nips away in the margins, the goosander is a problem especially for the game fish as they take a lot of small fish / parr and as for the kingfisher, he takes very very small fish.

 

The fecundity of fish allows and encourages large scale predation on fry / small fish but obviously is reliant on a head of mature fish to spawn and keep the cycle going. I would say the cormorant is more of a problem than the three put together.

 

If we only had predators that took juvenile fish I would not be typing this out now but I just dont see what comparison you are trying to draw with the Otter, a large mammal..... which takes fish of all sizes, bigger the better.

 

A single pair of otters, male and female using the figures given above (and which I dont doubt unless told otherwise) would eat 14% of 17kg = 2.38 kilo's per day or 868 kilo's / 1911 lbs per year. Thats just a single pair per year, totally forgetting their breeding cycle / young. I suppose thats why it suits the purpose to say they have a territory of 25 miles of river. Does that mean the whole of the River Wye, 157 miles long... only has 6 pairs of otters? Naturally, this leads onto the question of just how many pairs of otters are there on the River Wye? Or other Rivers come to that.

 

Then add in partially eating their kill. Now I always used to think otters were hard to find sign of because they completely consumed their catch, starting by chewing off the tail first in case they drop the fish when it struggles, thats probably also why anglers catch fish with parts of the caudal fin missing - it got away but is now partially disabled for later chases. The otter then eats the rest, the lot head to tail but no...a number of anglers find partially eaten carcasses and a quick look on the web shows that in studies otters are shown to routinely leave a large part of the kill, after taking the favoured organs / viscera area.

 

Therefore the total fish kill poundage wise, will be much much greater than the above figure of 1911 lb's per pair per year (excluding young).

 

Also the claim that they will not expend energy catching healthy bigger fish is questionable. If they can catch them then they will... as they will receive a bigger meal for the extra energy expended.

 

Glad you enjoyed watching the otter eating the frog close up, fantastic being so close to an animal that has such acute senses. I understand why you get a buzz out of it. Do you run Otter field trips for customers?

 

Hopefully the figures above allow a better overall picture for contributors to AN, though figures for a breeding pair and their young, plus approximate numbers of otters on each river surveyed (presumably compared with otters numbers originally introduced... so expansion can be monitored) would be far better again and I think would raise a few eyebrows.

 

Kind Regards

Jeff

I certainly wouldn't argue with your figures Jeff. Next, total the amount of fish of all species and all sizes taken by the Goosanders, Herons, Kingfishers, Moorhens, Terns, Otters, Mink, occasional Badgers, Foxes, Polecat, Gulls, Rats, Pike, Trout, Perch, Eels, Chub and the eggs taken by smaller fish and invertebrates and of course Man. Then add the deaths by disease, pollution, accident, parasite infection etc. And the figure would be almost unbelievable.

 

It just goes to show how resilient and fecund nature is. The majority of the fish in the river will be 'non-specimen' size and those will be the vast majority that are consumed. Anglers, particularly those that know a river well will make judgements about the health of the fish numbers based on what they see.....and why not. My view of this reasoning is to an extent slightly different. As anglers on rivers we are only present to view happenings for a tiny fraction of the available time. The proof of the pudding as it were is in the overall result. The three rivers that I fish the most, the Wye, the Teme and the Lugg all have significant otter populations. The Teme and the Lugg particularly have fish stocks (based on my and friends capture results) that have increased both in individual size and weight and overall population numbers. Certain species have gone or declined such as gudgeon in the Teme. Other species have come in or increased, such as bream, bleak (new fish on the Teme in the stretches I fish) and the average sizes of the chub and barbel are easily double that of 25 years ago.

 

I will mention one thing that I think could be a significant factor in the disappearance of some individual fish. Guiding! no names, no pack-drill........just repetitive targetting of specimen fish day after day after day. This is repeated across the country on lots of rivers with hopeful future record catchers. This is not a dig at the individuals or indeed the considerable skills that these guys have but, I seriously question whether the fish can take the pressure. This could lead to potential weakness and increased susceptibility to predation. I have no proof but the barbel 'disappearances' seem to be happening on rivers that have a high guiding culture/rate!

 

As yet I have found no otter kills on the Wye, Teme or the Lugg. The Wye is easily explained, I haven't fished it much at all this year. The Teme, well, otter tracks and spraints on both of my regular stretches and the same on the Lugg. All spraints investigated have contained small (as in fish under 1 lb) bones! If AN regulars could collect otter spraints. The analysis of the contents would be of value to all concerned!

 

My claim on the bigger fish predation is that in my opinion otters are more likely to take small fish than risk taking larger ones. If a larger fish is showing a weakness however then I would be the first person to expect an otter to make a kill. That's how they function.

 

As for guiding trips for otters. Not something I have thought of and, to be honest, even when I'm looking for them they usually catch me unawares by coming up behind me when I'm rolling a fag with the camera well and truly in the bag.......just like fishing really!

 

Regards, Nick

[Jeffwill]

I certainly wouldn't argue with your figures Jeff. Next, total the amount of fish of all species and all sizes taken by the Goosanders, Herons, Kingfishers, Moorhens, Terns, Otters, Mink, occasional Badgers, Foxes, Polecat, Gulls, Rats, Pike, Trout, Perch, Eels, Chub and the eggs taken by smaller fish and invertebrates and of course Man. Then add the deaths by disease, pollution, accident, parasite infection etc. And the figure would be almost unbelievable.

 

It just goes to show how resilient and fecund nature is. The majority of the fish in the river will be 'non-specimen' size and those will be the vast majority that are consumed. Anglers, particularly those that know a river well will make judgements about the health of the fish numbers based on what they see.....and why not. My view of this reasoning is to an extent slightly different. As anglers on rivers we are only present to view happenings for a tiny fraction of the available time. The proof of the pudding as it were is in the overall result. The three rivers that I fish the most, the Wye, the Teme and the Lugg all have significant otter populations. The Teme and the Lugg particularly have fish stocks (based on my and friends capture results) that have increased both in individual size and weight and overall population numbers. Certain species have gone or declined such as gudgeon in the Teme. Other species have come in or increased, such as bream, bleak (new fish on the Teme in the stretches I fish) and the average sizes of the chub and barbel are easily double that of 25 years ago.

 

I will mention one thing that I think could be a significant factor in the disappearance of some individual fish. Guiding! no names, no pack-drill........just repetitive targetting of specimen fish day after day after day. This is repeated across the country on lots of rivers with hopeful future record catchers. This is not a dig at the individuals or indeed the considerable skills that these guys have but, I seriously question whether the fish can take the pressure. This could lead to potential weakness and increased susceptibility to predation. I have no proof but the barbel 'disappearances' seem to be happening on rivers that have a high guiding culture/rate!

 

As yet I have found no otter kills on the Wye, Teme or the Lugg. The Wye is easily explained, I haven't fished it much at all this year. The Teme, well, otter tracks and spraints on both of my regular stretches and the same on the Lugg. All spraints investigated have contained small (as in fish under 1 lb) bones! If AN regulars could collect otter spraints. The analysis of the contents would be of value to all concerned!

 

My claim on the bigger fish predation is that in my opinion otters are more likely to take small fish than risk taking larger ones. If a larger fish is showing a weakness however then I would be the first person to expect an otter to make a kill. That's how they function.

 

As for guiding trips for otters. Not something I have thought of and, to be honest, even when I'm looking for them they usually catch me unawares by coming up behind me when I'm rolling a fag with the camera well and truly in the bag.......just like fishing really!

 

Regards, Nick

 

 

Thanks for that Nick, very nicely put. You are a lucky man to fish those rivers and get to know them so well. I am still keen to know though:

 

1/ The number of Otters spread along the Wye, estimate split by male / female and cubs if possible. (Not to know this after stocking Otters would be irresponsible of relevant Quango's)

2/ The number originally stocked (so that expansion can be assessed)

3/ The amount of fish consumed in an average year by female otter and an average litter of cubs

 

I am just trying to get a reasonable and accurate assessment of the number of tonnes of fish killed per year attributable purely to Otters on the Wye and or other rivers. Then anglers can decide if Otters have a bigger or smaller take, impact or whatever from the river than they previously thought. Its only right that people should have the full facts in front of them to make decisions or form opinions.

 

Conversely its possible that Otters help to keep the fish stock healthy, disease free by killing

old fish, diseased fish etc etc. Does a river exist these days that does not have otters that can be surveyed?

 

Its also claimed Otters "push out" Mink which hopefully in turn will help Water Voles, in certain area's, though I suppose unless they actually kill the mink they are just moving the problem on. Public funds should definitely be targeted at culling mink. Their impact on the waterfowl, voles etc has been catastrophic.

 

Thanks again

Jeff.

[Worms]

Thanks for that Nick, very nicely put. You are a lucky man to fish those rivers and get to know them so well. I am still keen to know though:

 

1/ The number of Otters spread along the Wye, estimate split by male / female and cubs if possible. (Not to know this after stocking Otters would be irresponsible of relevant Quango's)

2/ The number originally stocked (so that expansion can be assessed)

3/ The amount of fish consumed in an average year by female otter and an average litter of cubs

 

I am just trying to get a reasonable and accurate assessment of the number of tonnes of fish killed per year attributable purely to Otters on the Wye and or other rivers. Then anglers can decide if Otters have a bigger or smaller take, impact or whatever from the river than they previously thought. Its only right that people should have the full facts in front of them to make decisions or form opinions.

 

Conversely its possible that Otters help to keep the fish stock healthy, disease free by killing

old fish, diseased fish etc etc. Does a river exist these days that does not have otters that can be surveyed?

 

Its also claimed Otters "push out" Mink which hopefully in turn will help Water Voles, in certain area's, though I suppose unless they actually kill the mink they are just moving the problem on. Public funds should definitely be targeted at culling mink. Their impact on the waterfowl, voles etc has been catastrophic.

 

Thanks again

Jeff.

A quote from the SAC (Special Area of Conservation) site designation page. http://www.jncc.gov.uk/ProtectedSites/SACs...Ucode=UK0012642

"The Wye holds the densest and most well-established otter Lutra lutra population in Wales, representative of otters occurring in lowland freshwater habitats in the borders of Wales. The river has bank-side vegetation cover, abundant food supply, clean water and undisturbed areas of dense scrub suitable for breeding, making it particularly favourable as otter habitat. The population remained even during the lowest point of the UK decline, confirming that the site is particularly favourable for this species and the population likely to be highly stable."

 

This is including the flood plains and tributaries of the river, not just the Wye. Astonishingly enough, the River Wye catchment area is over 4,000 sq/km!

Below is a section taken from the Worcestershire Biodiversity Action Plan (BAP) http://worcestershire.whub.org.uk/home/wcc-bio-s1-otter-3.pdf ://http://worcestershire.whub.org.uk/h...s1-otter-3.pdf ://http://worcestershire.whub.org.uk/h...s1-otter-3.pdf which goes some way to explaining why otters are difficult to count.....territory size!

 

"Territory sizes have most frequently been measured in terms of length of waterway, but this may not present an accurate

picture in places where part or all of the range consists of lakes or ponds, or when comparing very large waterways with small ones. Male otters are frequently found to maintain territories of up to 50 km of riverbank but this may not reflect the total area of habitat occupied. Likewise, otters found to maintain territories along seemingly short sections of river may in fact be using extensive areas of habitat adjacent to the main body of the river: this will include wet woodland and scrub as well as more obvious wetland habitat."

 

Unfortunately there are no absolute figures for otters on the Wye. Partly because any figures are old (2002 survey, a new survey is being conducted as we speak and results will be published in 2010) and partly because of the methods used to conduct otter surveys. This is to walk the watercourse until signs of otter are detected. The last detailed survey in 2002 (4th survey) used previous survey sites to mark the increase in the and An otter can have a considerable range and this range will include tributaries and pools as well as the main river. In fact there is strong evidence to suggest that otters may spend more time foraging in the tributaries and pools than in the main river system. From a variety of studies most more than 7 years old indicate an average figure of one otter per km²

 

I will try and answer your questions as best I can. Unfortunately with survey limitations and an expanding population accurate figures are impossible to obtain hence the length of the answers!

 

1. No definitive figure as yet but probably near peak in the Wye catchment. Sex ratios I assume to be 1:1 as with most mammalian predators. The majority of evidence of sex ratios is unfortunately from casualty figures (mainly traffic) which gives figures between 1.4:1 (male: female) in Finland and 1.6:1 in England and Wales. Juvenile mortality figures show 1:1. Some older survey work suggests ratios of 1-1.2:1 of live animals but then again, dog otters are more mobile and more likely to be seen especially if a female is nursing cubs. With dead animal figures my guess is that dog otters are more likely to be killed as they have a wider foraging range. Juvenile mortality shows equal distribution of young otters!

 

Territories of dog otters will overlap those of bitches. Dogs may father pups from more than one female. It is likely that some dog otters (probably younger ones) do not breed until a territory is established or an older animal is usurped/dies.

 

The general concensus from a variety of (reliable) sources indicates that fish comprise approximately 67% of the otter's prey (in Europe). This will vary somewhat depending on availability, season and area.

 

I have tried to find out fish biomass figures for the Wye but I have not been successful. Apparent average figures for UK rivers are in the region of 25g m². This can rocket to figures exceeding 260g m² in some areas of tidal rivers with salmon runs at some times of the year. My guess is that the Wye fits in there somewhere. A number of studies have calculated that a river exceeding 5g m² would support viable otter populations (and keeping the fish population viable obviously!)

 

2. None

 

3. I would estimate food consumption of the female as that of a low weight animal, say 7kg and that of young to be somewhat less after weaning and increasing to adult levels depending on food availability etc. 2-3 cubs born after a gestation period of 63 days at any time of the year. Weaned after 3-4 months. Young leave the mother at about 1 year. Sexually mature at 2-3 years.

 

Births in the Wye catchment area are usually timed to coincide with spawning salmon and sea trout, amphibian breeding and smolt migration.

 

The following is taken from: Ecology of the European Otter Conserving Natura 2000 Rivers Ecology Series No. 10

Paul Chanin

 

"Otters have been recorded feeding on a very wide range of fish from <50 mm in length and 1 g in

weight (Kruuk et al. 1993), up to 900 mm in length and weighing 6.3 kg (Carss, Kruuk & Conroy 1990).

Even larger specimens (20 kg+) have been reported by carp fishermen (Mitchell-Jones, pers. comm.)."

 

That last bits a surprise eh!

 

I'm sorry if I can't answer your questions fully but the natural otter population increase is following suitable habitat with suitable prey. Re-introductions were very limited and not at all on the Wye and Bristol Avon. All are nature-al re-colonisations.

 

Nick

Edited August 5, 2009 by Worms

[Worms]

I have edited last night's post with more info!

[denzil]

i think in the winter the otter are more of a problem when it gets cold the fish are a lot less active and will hardly move at times i'm guessing this makes big fish more attractive as food in these conditions. one big mouth full rather than several small ones. any thoughts guys? cheers denzil

[Anderoo]

My personal feeling is that there are a hundred or more animals that eat fish, and any 'right' we have to preserve fish stocks for our own selfish ends is way down Nature's priority list.

 

Angling is (to me) the skill of trying to locate and outwit wild fish, and to enjoy the natural world in all its diversity, and to do what we can to look after it. Not to manipulate it so the fishing is easier/better. If my local stretch of river suddenly stops producing 5lb chub because something ate all of them (unlikely, but for the sake of argument), well yes, that would be a shame. But I have the whole world out there to go fishing in, and I bet if I came back in 5 years the big chub would be back, pollution and abstraction problems permitting.

 

In the meantime, perhaps a 3lb chub would become the new 'big' weight to aim for, and catching a 3lber would take exactly the same combination of location, keeping very quiet, baiting and casting as catching a 5lber. Or does the extra 2lbs make all the difference?

 

I enjoy trying to catch big fish, but I know that if I fail I still get to eat something when I get home. You can't blame wild creatures for eating fish.

 

If there was such a creature that 'decimates' rivers and lakes, rampaging through and eating or simply killing everything before moving on, then that would be a problem. Luckily there isn't, apart from perhaps cormorants and small fish. But again, their hand was forced.

 

I wonder how many people would be up in arms about this if the weeklies hadn't pushed the story so much? Would we even be talking about it?

 

(The river I mentioned has populations of otters by the way, and has had for some time, and a very healthy fish population of all sizes.)

 

I just don't believe that otters are a problem. It seems like whenever anyone has a bad day's fishing they have to find a scapegoat. It is possible for the fish to still be in the river somewhere but not get caught!

 

Around here the river fishing is really good, and there are plenty of otters.

 

I think I'll stop ranting now, I've forgotten what my point was

[denzil]

the thing is that these are not wild otters they have been bred and released into our waterways by man so i cant see how this new balance is natural

[Worms]

the thing is that these are not wild otters they have been bred and released into our waterways by man so i cant see how this new balance is natural

At the risk of repeating myself and without appearing to be rude, no otters have been re-introduced into the Bristol Avon catchment or, for that matter into the Wye catchment.

 

An Environment Agency statement:

 

"Between 1983 and 1999 a small number (117) of captive-bred otters were released to the wild by the Otter Trust. The Vincent Wildlife Trust released rehabilitated animals between 1990 and 1996 (49), over half as part of a Yorkshire release programme, but also a few into East Anglia, Northumbria and on the Trent. No introductions of captive-bred otters have occurred since 1999."

 

The majority of the 117 otter trust releases were in East Anglia and the East Midlands.

 

The expansion of otters that you see now in most of the country are wild, wild, wild and have never been handled by Humans. The reason for their success is the control (ban) of certain organochlorine pesticides and the money spent by the Environment Agency, Natural England, Conservation volunteers and a myriad other groups and charities including many angling clubs, large and small that have improved the quality of our natural rivers and waterways. These improvements have contributed to suitable vegetation, bank erosion defences, fish spawning grounds and overall health of the rivers. THIS IS WHY THE OTTERS HAVE COME BACK! otters will NOT colonise areas that do not have suitable quantities of prey, or suitable natal den areas and they dislike disturbance. If you read the previous posts in this thread carefully you will find a lot more facts about otters. They will not eat all the fish in a natural fishery!

[yorkio]

I think I'll stop ranting now, I've forgotten what my point was

I think you made your point very well indeed and I couldn't agree more.

[Anderoo]

the thing is that these are not wild otters they have been bred and released into our waterways by man so i cant see how this new balance is natural

 

 

Denzil, do you have any further information on this please? Where did this information come from?