Utter Claptrap!

[Nightwing]

Interesting discussion about pike.

They are native to both Eurasia and North America..so I don't see why they could not also have made it to Scottland? Indeed..given their almost universal population coverage in the northern U.S., and Canada, as well as northern Asia..I would think it much more strange if they were NOT found naturaly in Scottland....

JMHO, however, as I don't live there!

[StuMac]

There's another thread on here from a few months back where I made similar points. I think the east west watershed is probably their natural boudary.

[Peter Waller]

Sift out the hyperbole and exageration and maybe it isn't so far off the mark. But do pike live to 50 years of age?

 

I wouldn't bother to travel to Scotland for the trout fishing, I would for the pike though!

[Andy Macfarlane]

Nightwing:

Interesting discussion about pike.

They are native to both Eurasia and North America..so I don't see why they could not also  have made it to Scottland?   Indeed..given their almost universal population coverage in the northern U.S., and Canada, as well as northern Asia..I would think it much more strange if they were NOT found naturaly in Scottland....

JMHO, however, as I don't live there!

Exactly. I fail to see how both Char and Powan could end up in land locked Highland lochs after the glacial water receeded but Pike didn't. All three are just as capable of living in brackish water. All three are found side by side in waters all over the Northern hemisphere, including Scotland but it seems it is only in Scotland that stocking of Pike has taken place.

[Vagabond]

The views of Nightwing and Andy are certainly based on common-sense, and my gut-feeling is to agree. However, there are one or two bits of evidence re pike distribution that need explaining.

 

1/ Maitland and Cambell (Freshwater Fishes, New Naturalist 1992) claim there is genetic evidence that pike were indigenous to SE England after the last ice age and have been spread Northwest since then. They say

 

"Genetic constitution of samples of pike from N America, Scandinavia, Netherlands, England and Ireland (note they do not mention Wales or Scotland - whether that is deliberate or whether they share the widespread delusion that England is synonymous with Britain - I know not) have been investigated biochemically ..... these results are comparable with the hypothesis that the distribution of pike in the British Isles has progressively moved north and west"

 

They don't quote a source - does anyone know what it is?

 

2/ If Andy/Nightwing are right, then pike should be present in the Hebrides and Northwest Highlands. Pike are present on Islay, but as far as I know, not in the other Isles - does anyone know differently? On the mainland, are pike present in (say) Lochs Loyal and Shin ? What is the furthest north anyone has encountered pike ? I have had them in Loch Cluanie - any advance on that?

 

3/ A couple of bits of circumstantial evidence.

 

a/ Re Andy's point as to why people might carry bucketloads of pike up to hill tarns. In the middle ages pike were used as a food fish by the poorer classes so that is a powerful motive to try to spread them.

 

b/ The Gaelic name for pike is Gailliasc which translated means "Foreign fish"

[Leon Roskilly]

Research seems to suggest that nature has many strategies for moving fish around (see below)

 

As fish are (mostly) unable to fly, and bodies of water are often completely seperated, that's quite sensible when you think about it!

 

It would seem that if a species exist in a region, sooner or later they will find their way to all bodies of water in that region, and whether they thrive or wither there will depend upon whether local conditions are favourable.

 

eg temperature, acidity, prey abundance, predator etc etc

 

When conditions change, then it is to be expected that a species that had in the past been repulsed by environmental conditions in a particular water, could now thrive.

 

Global warming, increased nutrients etc are fast changing conditions in most of our big waters, and as the past equilibrium is changed, so the mix of inhabitants and the results of repeated colonisation attempts will be different.

 

Tight Lines - leon

 

----------------------------

 

Negative Islands

 

I heard a Radio 4 programme some time ago where scientists studying evolutionary theory were bemoaning that, in this modern age, they didn't have the advantage of Darwin who was able to study isolated island populations.

 

They then had the brainwave that lakes are 'negative islands', so (spurning waters connected by river flood plains etc), they set out to see what genetic variations they could find as species seperated by millenia evolved to local conditions.

 

In all cases, they were disappointed.

 

The studies revealed that there was evidence of 'recent' gene swapping between fish species that should be geographically isolated!

 

Nature seems to have worked out how to move fish around!

 

----------

 

 

http://www.nature.com/cgi-taf/DynaPage.taf...s/6888240a.html

 

Abstract

 

The isolating nature of freshwater systems may lead to expectations of substantial genetic subdivision among populations of obligate freshwater species.

 

We examined the genetic structure of populations of the freshwater fish Hypseleotris compressa (Gobiidae) using allozyme and mtDNA markers.

 

Fifteen east coast Queensland populations and one Northern Territory population were sampled to examine levels of differentiation within and between drainages at near, medium and broad scales.

 

Initial allozyme data suggested high levels of gene flow and connectivity among populations at broad spatial scales.

 

However there was no significant relationship between geographical distance and gene flow among east coast populations which may indicate, among other possibilities, that these populations are not at equilibrium between gene flow and genetic drift.

 

Analyses of a 567-bp fragment of the ATPase6 mtDNA gene revealed a star-shaped phylogeny, with many singleton, recently derived haplotypes.

 

Tajima's test of neutrality was significantly negative.

 

The allozyme and mtDNA data may be indicative of an historical demographic change that was reflected in the nonequilibrium pattern exhibited by contemporary populations.

 

As estimating current levels of gene flow would violate basic assumptions of underlying models, approximations were not made.

 

Nevertheless, patterns of genetic variation among populations of H. compressa do not match traditional expectations for a freshwater fish, and it would appear that there has been at least historical connectivity between populations now inhabiting different drainages.

 

 

Full Text:

 

http://www.nature.com/cgi-taf/DynaPage.taf...l/6888240a.html

 

---------------------------------------

 

http://www.nature.com/cgi-taf/DynaPage.taf...s/6883020a.html

 

Abstract

 

 

Among the many freshwater habitats occupied by the mosquitofish (Gambusia hubbsi) on Andros Island, Bahamas, are blueholes: vertical caves that filled with water as sea levels rose during the past 15 000 years.

 

At the present time, many of the blueholes on Andros Island appear to be highly isolated habitats analogous to islands.

 

However, geographical distance among blueholes and the geological history of bluehole formation may also affect the genetic structure of G. hubbsi populations in blueholes.

 

Thirty-two isozyme loci in 14 G. hubbsi populations inhabiting blueholes and three inhabiting surface-water habitats were assayed to gain insight into the effects of geological history and geographical distribution on population structure.

 

Genetic structure among populations is high and significant (FST=0.38-0.4) and Nei's genetic distance (D) is low among all populations.

 

Although G. hubbsi populations are closely related, bluehole geology imposes significant barriers to gene flow.

 

A pattern of isolation-by-distance was not evident in the genetic data.

 

Furthermore, none of the bluehole populations appears to be a source from which other bluehole populations were founded.

 

Rather, they appear to be 'sinks' into which migration may occur rarely.

 

Genetic drift appears to have had a profound effect on allozyme allele frequencies in the G. hubbsi populations that were sampled.

 

Local population structure measured by allozymes appears to be more heavily influenced by historical population dynamics and stochastic migration than by geographical locality or age of the blueholes.

 

Full Text: http://www.nature.com/cgi-taf/DynaPage.taf...ml&filetype=PDF

 

----------------------------------------

 

http://www.nature.com/cgi-taf/DynaPage.taf...re01547_fs.html

 

 

Nature 422, 714 - 716 (17 April 2003); doi:10.1038/nature01547

 

Explaining the excess of rare species in natural species abundance distributions

ANNE E. MAGURRAN*† AND PETER A. HENDERSON†‡

* Gatty Marine Laboratory, School of Biology, University of St Andrews, St Andrews, Fife KY16 8LB, UK

‡ Pisces Conservation Ltd, IRC House, The Square, Pennington, Lymington, Hampshire SO41 8GN, UK

† The authors contributed equally to this work

Correspondence and requests for materials should be addressed to A.E.M. (e-mail: aem1@st-andrews.ac.uk). The full data set can be downloaded from the Pisces Conservation Ltd website (http://www.irchouse.demon.co.uk/latestreports.html).

 

The observation that a few species in ecological communities are exceptionally abundant, whereas most are rare, prompted the development of species abundance models.

 

Nevertheless, despite the large literature on the commonness and rarity of species inspired by these pioneering studies, some widespread empirical patterns of species abundance resist easy explanation.

 

Notable among these is the observation that in large assemblages there are more rare species than the log normal model predicts.

 

Here we use a long-term (21-year) data set, from an estuarine fish community, to show how an ecological community can be separated into two components. Core species, which are persistent, abundant and biologically associated with estuarine habitats, are log normally distributed. Occasional species occur infrequently in the record, are typically low in abundance and have different habitat requirements; they follow a log series distribution. These distributions are overlaid, producing the negative skew that characterizes real data sets.

 

 

Full Text: http://www.nature.com/cgi-taf/DynaPage.taf...re01547_fs.html

[StuMac]

The work quoted by Miatland and Cambell would have used methods that are pretty crude by todays standards (I thnik polymorphisms in enzymes etc). The real way to look at populations is to look at mitochondrail DNA, which is passed directly down the female line. If anyone's interested theres an excellent book, The Seven Daughers of Eve by Bryan Sykes, which expalins it all realy well. Available in the popular science section of any good bookshop.

 

Different populations usually have discinct patterns of mutations in mitochondrial DNA, and these can be readily recognised. If (for example) you carted a female pike from Norfolk and populated Islay with its ofspring, then they will have a 'Norfolk' mitochondrain DNA patern that may be easily recognizable.

 

The statement that pike were indiginous to SE england after the last ice age and then moved NW is a bit of a "non fact". SE england wasn't covered with ice. Pike can't live under ice and and so all its saying is that pike followed the retreating ice, which we all know.

 

Despite papers listed above, there are examples of isolated fish populations. The classic is the powan in L. Lomond, these are herring like gfishes which were stuck there as the loch was cut off from the sea. It you look at the map you can see that L. Lomond was basically an arm of the Firth of Clyde that was cut off from the sea by a huge heap of galcial morrain which now has Dunbarton / balloch built on it.

 

This is actually a question thats starting to interest me. I did my first degree in Zoology and run a research lab, although I don't work as a Zoologist. I'm thinking of chatting to some people who really know about fish biology (possibly the characters in St Andrews mentioned above) may see if we can work out some sort of collaboration. It's be quite nice to "go back to my roots" and do some proper biology!

[salvelinus]

Stumac,

Maitland is probably the best person to talk to about fish populations/communities in Britain.

 

Char would be naturally the first fish to colonise after (in the melt waters of) an ice age because of their biology. The are the most northerly distributed freshwater species. Powan/white fish would have been soon after along with eels and trout and soon after that salmon.

 

Char only (And trout only) lakes used to exist in Scotland and Ireland. While some remain most have had extra species (trout, perch and pike most commonly) added by anglers and locals looking for increased food supplies and increased sporting opportunities.

 

Pike are absent from the south west of Ireland. None of the river systems or lakes have naturally occuring populations. It is strange that while char, trout, salmon, eels are present in all geographical areas (North, south east and west) that pike never colonised the southwest corner of ireland.

 

If you are interested in single species communities look at the research into char only lake in Iceland, Sweden and elsewhere - you will find it very interesting.

[Tog]

Fish seem able to colonise just about any bit of water even without mans help. Waterfowl and prededary birds have a habit of lake hopping fish and their eggs about the place. Maybe a pike egg or two hitched a lift on an eel?

But once again big bad angler gets the blame!

Personaly I think 'fish swappers' give yet another arrow to the anti's when disease and decimation set in and I can't condone such action - but nature has her way of redressing the balance when given time.(although I do wonder how we can reduce the **** cormorants)!

[StuMac]

Grayling and pike are actually the most Northerly true freshwater fish (i.e. those without a marine phase in their life cycle).

 

I think there can be no real doubt that pike were introduced to Ireland (despite what the Irish Pike Society says). However, given the range of habitats that they occupy in Scandinavia, Russia and Canada, and given the recent geological history of Britain. I find it very hard to accept that natural populations are not found in Eastward draining rivers.

 

I think the westward limit of their natural geographic range would be the East West watershed of the British mainland.