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Please help - GCN: |
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Tom Lawlor Member Joined: 24 Jun 2004 No. of posts: 3  View other posts by Tom Lawlor |
Posted: 28 Jun 2004 I am interested in obtaining data to support/disprove the hypothesis that GCN
require deep open water with, in particular, nil to zero fish populations. It is, understandably, proving difficult to obtain specific information relating to individual newt habitats. I do not require the exact locations although it would prove useful if the topography was known together with the regional area. The hypothesis forms the basis of an Open University project. I require two sets of data - ponds with fish populations and ponds without / with benign populations. The intention is to analyse the data and attempt to correlate factors that are based on actual sites throughout the UK. You would of course be welcome to a copy of the final project and data. Would it be possible to solicit yourself and other colleagues in order to obtain specific data? If not could you, please, suggest an alternative avenue. (I complete an Hons Degree in Environment next year, and I have also managed to gain diplomas in Pollution Control and Environmental Policy). Regards, Tom Tom Lawlor |
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Caleb Forum Coordinator Joined: 17 Feb 2003 No. of posts: 448 View other posts by Caleb |
Posted: 28 Jun 2004 This sounds quite similar to work that was done at Leicester Poly (now De Montfort University) in the 90s. The idea was to produce an 'expert system' computer program to predict the suitability of a given pond for crested newts. This was published in the Herpetological Journal in 2000, you can see an abstract here You may be able to get data from the Biological Records Centre, who hold national records for all native herp species. |
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Tom Lawlor Member Joined: 24 Jun 2004 No. of posts: 3 View other posts by Tom Lawlor |
Posted: 30 Jun 2004 Caleb, Thank-you for the reply. I have, so far, contacted great number of organisations, but with limited success. I have obtained some specific data - GCN's in ditches 2 m wide, ponds no more than 50 cm deep (population of approximately 300) and one pond that had GCN's prior to the stocking of carp by an angling club. The latter was some time ago, but it shows that even so called benign species, stocked in sufficient numbers, can have a disastrous effect Tom Tom Lawlor |
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Gemma Fairchild Krag Committee Joined: 14 Feb 2003 No. of posts: 193 View other posts by Gemma Fairchild |
Posted: 30 Jun 2004 Tom, I know that odonates can be wiped out by carp due them uprooting aquatic plants encouraging blooms of planktonic algae, which eventually lower oxygen content making the pond unviable. Could it be a similar process affecting GCN? ----RAUK e-Forum---- 
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calumma Senior Member Joined: 27 Jun 2003 No. of posts: 351 View other posts by calumma |
Posted: 30 Jun 2004 Tom, I have data on this subject that I would be willing to discuss. I believe Richard Griffiths has passed my details on to you. Contact me and we can talk. Lee Brady Lee Brady Kent Herpetofauna Recorder | Independent Ecological Consultant |
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Tom Lawlor Member Joined: 24 Jun 2004 No. of posts: 3 View other posts by Tom Lawlor |
Posted: 30 Jun 2004 Gemma, I suppose itĘs a possibility, it all depends on the level of stocking thatĘs undertaken. I know that surface area is a key factor in determining a sustainable population. Perhaps consideration should be given to the effects of biological oxygen demand (BOD) due to the eventual dacay of algae blooms brought on by disturbing silt deposits. I really donĘt know if carp actively prey on newt larvae or if itĘs because there is an insufficient alternative for them to feed on. Tom Lawlor |
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Rex Sumner Member Joined: 23 Jun 2004 No. of posts: 7 View other posts by Rex Sumner |
Posted: 01 Jul 2004 Carp are opportunistic feeders but definitely omnivorous. They feed avidly on snails, slugs and worms in addition to vegetation while anglers create high protein mixes to tempt them. However they hunt mainly by smell, or whatever you wish to call the sense using their tendrils. I would imagine that an inactive newt would be happily consumed, but one that chose to swim away would get away. Evolution therefore dictates that the carp would become predators of sickly and dying newts rather than active ones, but a high stocking level of carp could easily change this feeding behaviour to hunting by sight and chasing, which would eradicate the newts in short order. A succesful fishing fly has been developed to catch rainbow trout based on the GCN! Rex |
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Gemma Fairchild Krag Committee Joined: 14 Feb 2003 No. of posts: 193 View other posts by Gemma Fairchild |
Posted: 01 Jul 2004 Tom, The process of deoxygenation is also promoted by shading of oxygenating plants by the algea. I wonder how much of an affect this would have on the GCN larvae as opposed to direct predation of adults by carp. I suppose, as ever it's a mixture of factors specific to each pond. ----RAUK e-Forum----
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calumma Senior Member Joined: 27 Jun 2003 No. of posts: 351 View other posts by calumma |
Posted: 05 Jul 2004 I have had several people ask me about the impact of carp on gcn. Even grass carp (popular in the US but appearing over here) can have a serious impact and I have never surveyed a 'good' carp pond (goldfish aside) that has also supported a medium to large population of gcn. Younger grass carp feed on small water animals that include zooplankton (water fleas etc). Since crested newt larvae are nektonic (i.e. they swim around in the open water feeding on zooplankton) they can also be eaten by young grass carp. But note that I *often* survey ponds that support both stickleback and gcn. Indeed I once netted an adult female gcn with a stickleback in her mouth! Lee Lee Brady Kent Herpetofauna Recorder | Independent Ecological Consultant |
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B Lewis Krag Committee Joined: 24 Aug 2004 No. of posts: 146  View other posts by B Lewis |
Posted: 06 Sep 2004 I think it's quite interesting to see just how GCNs can survive and breed in very poor conditions. I have surveyed a number of ponds this year that have been way off the mark of the the 'text-book' GCN pond even with bits of engine and asbestos in them. Some eutrophic and some with good fish populations esp. Stickleback. GCNs appear to be quite hardy little critters and it would seem that they can cope with quite 'harsh' and varied conditions especially in the metapopulation scenario. I read a paper recently on the ability of Carp to increase the villi on the lung walls in order to make better use when obtaining oxygen from poor water quality (environmental pressure response). Does anyone know if this happens with other water-based animals, particularly amphibians. Brett.
Lewis Ecology Brett Lewis Photography Kent Reptile & Amphibian Group DICE - University of Kent |
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Caleb Forum Coordinator Joined: 17 Feb 2003 No. of posts: 448 View other posts by Caleb |
Posted: 07 Sep 2004 Brett- did the GCNs have any breeding success in these ponds? I've seen adults in some pretty 'unsuitable' ponds, but these ponds never seemed to produce many larvae. In one group of ponds I looked at some years ago, I think that the destruction of one good pond led to newts appearing in almost any nearby waterbody over the next few years. Of course, the 'unsuitable' ponds may have been more suitable in the past... |
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B Lewis Krag Committee Joined: 24 Aug 2004 No. of posts: 146 View other posts by B Lewis |
Posted: 07 Sep 2004 Caleb, It depends on how you define 'breeding success'. There were adult male and female animals, eggs, then larvae. But to estimate breeding success would be difficult from the single season survey. They were obviously reproducing. One pond in particular was within proximity (50m or so) of a pristine pond that was every bit a breeding pond. It was this pond that had asbestos, rusty metal etc... with reproducing animals that was drawn to my attention. Another one recently surveyed was of similar poor quality and had been deemed, from desk-top surveyors, to be unlikely to contain GCN's however first visit and a quick netting revealed the presence of GCN larvae. Now this pond again was linked by a network of waterways, but had recently been separated due to its ephemeral qualities. I have also seen reproductive success in ponds containing fish such as stickleback. I am therefore often wary to committing myself to say that it is likely or unlikely to contain GCNs when fish are present. It really depends on the rest of the habitat suitability and waterbody connectivity. It just goes to show you need to be out in the field to see these thingsą nature never really follows the text book..! :o) Brett. Lewis Ecology Brett Lewis Photography Kent Reptile & Amphibian Group DICE - University of Kent |
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Caleb Forum Coordinator Joined: 17 Feb 2003 No. of posts: 448 View other posts by Caleb |
Posted: 08 Sep 2004 Interesting to hear about these ponds, especially the example where newts use an 'unsuitable' pond where a good one is available nearby. To contrast with this, Gemma mentioned a site in this thread that has adjacent ponds, one with fish, one without- apparently the GCNs never even enter the pond with fish in. I made a brief visit to a similar site earlier this year- two linked ponds, one with sticklebacks, one without. No newts seen at all in the pond with fish (but loads of toad tadpoles), quite a few smooth and crested newts in the other pond (but very few tadpoles). |
- Please help - GCN |