Dale Fort Blog Number 37

26 09 2014

Dale Fort’s connection with the Pembrokeshire Island of Skokholm

On the 9th of September 2014, my colleague Amy and I were privileged to visit Skokholm in the company of Mark Burton, Kate Locke and Jen Jones of The Skomer Marine Reserve. It has been many years since much attention has been given to the shores of the island and we helped them do some preliminary inspections.

Above the landingcrab coveApproaching the quarry with lighthouseThe Quarry


I thought I’d use this as an opportunity to tell you some of the history of the island and a couple of lesser known stories.

The island of Skokholm is about 2 miles offshore and 7 miles from Dale Fort. The name is Old Norse (like its neighbour Skomer) and its meaning is uncertain. Island of Stocks (where ships were built) or Island of Logs are two dodgy-sounding suggestions.

The island has a similar history to neighbouring Skomer having its first historical mentions as a rabbit warren in the 17th Century (rabbits were probably introduced in the 13th Century). In 1940, the government used Skokholm as a site for myxomatosis trials (that’s a story that might appear in another blog).

Skokholm was the UK’s first full-time bird observatory. It is owned by The Wildlife Trust of South and West Wales, having been purchased from Dale Castle Estates in 2006. It has been managed by the trust since 1937. The island was declared a National Nature Reserve in 2008 mainly because of its seabird colonies (Skokholm and Skomer provide nesting sites for at least half of the world’s population of manx shearwaters)

manx shearwater

Our story today starts with a young man called John Fursdon.

John first visited Skokholm in 1938 when he stayed with the Lockley family who had leased the island and were trying to lead a self-sufficient island existence as well as run the observatory. He liked it so much that he returned in 1939 and again in 1940 when he helped the Lockleys move from the island just after the beginning of the War.

After the conflict ended because of his previous experience John was asked to be the first post-war Warden of Skokholm. He took up the post for the 1946 season.

The West Wales Field Society (WWFS) had decided that they needed a mainland base from which to service their Bird Observatory on Skokholm and to promulgate “education and conservation of the unspoiled countryside of West Wales”.

The Honorary Chairman of the WWFS was one of its founder members, ex-Skokholm resident, Ronald Lockley. He persuaded the recently formed Council for the Promotion of Field Studies (CPFS later to become the FSC) that Dale Fort would be an ideal location for a maritime field centre, with the added bonus of an intimate association with the island of Skokholm.

The WWFS agreed to buy and set up the fort as a field centre if the CPFS agreed to guarantee the financial liability for staffing and maintenance of the fort as a Field Centre. The WWFS then set up an appeal for £10,000 to enable them to purchase the fort and 20 acres of surrounding land.

Appeal leaflet 1946

After protracted negotiations complicated by the fact that the owner was resident in Switzerland; Mrs. Lee-Roberts finally accepted £6000 from The West Wales Field Society for the purchase of Dale Fort. On 15th February 1947 the WWFS signed their half of the contract for the transaction.

Even before Mrs Lee Roberts had signed her half of the contract, her solicitors gave permission for the WWFS to occupy the site and begin the conversion of the buildings. The first man there was John Fursdon, who effectively was the first person in charge at the new field centre. He spent many hours cleaning up the mess left by the military who had occupied the site during the war.

John F with caption   I met John when he visited Dale Fort in 2003, (he died in 2011 aged 91). He had a wealth of amusing stories and was a thoroughly sound egg. Remembering his days on Skokholm, he told me about an unusual problem experienced by Trinity House staff when they attempted to supply the Skokholm Lighthouse.

The lighthouse builders had installed a railway track that led from the landing stage right across the island 1500 metres or so, to the site of the lighthouse on the extreme westerly point. The railway was used to transport building materials to the site.

Skokholm with railway route

After the building was completed the railway was still used to transport supplies and equipment. The stuff would be swung ashore using the large derricks near the landing stage and be loaded into a railway wagon.

There was no mechanical engine, the motive force was provided by a donkey who most of the time was free to wander about the island ad lib. It was an intelligent animal and it soon learned to recognize the sound of the supply vessel while it was still way out at sea and undetected by humans. Before the boat neared the island the donkey would take itself off to the Pond and go and stand in the middle, thus rendering herself unavailable for wagon-hauling. The animal then had to be enticed back onto to dry land in the traditional manner using a carrot on a stick.

John kindly sent me copies of some of his films based on the wildlife of the islands. The first part of his 1948 Pembrokeshire Wildlife film concerning Skokholm, with his own commentary (added I think when he transferred the film to videotape) can be seen here:


John’s time in charge at Dale Fort was soon to come to an end. In March 1947 an advertisement appeared in The Times from The Council for the Promotion of Field Studies. Assistant Wardens were required for Dale Fort, Flatford Mill and Malham Tarn. Wing Commander J.H. Barrett and several other candidates were interviewed for the posts on 15th April 1947 and John Barrett became the first Council for the Promotion of Field Studies Warden of Dale Fort Field Centre. On 1st July 1947 John and Ruth Barrett and their two children moved to Dale

From The Western Telegraph and Cymric Times 24th July 1947:


£10,000 purchase by West Wales Field Society

Dale Fort with 20 acres of land has been acquired by the West Wales Field Society as a nature centre. It will accommodate 50 students. For the purpose the society requires £10,000. Provided this sum is secured, financial liability for the staffing and management of the Fort as a Field Centre is guaranteed by the Council for the Promotion of Field Studies, which is receiving a grant for that purpose from the Ministry of Education. The CPFS will develop Dale Fort.

The £10,000 is needed to help develop Dale Fort and to pay the expenses of a secretary in conducting the appeal. Any balance will go towards the creation of further field centres and nature reserves.

Mr. R.M. Lockley, the chairman referred to the matter at the annual meeting of the Field Society last Thursday when he said that Skokholm had been established as a Bird Observatory while at Dale Fort they would have a centre for cultural outdoor research of great importance. He thought with energy, practice and forethought they would secure the £10,000.

Mr. John Fursdon said he would like to see the formation of a group or sub-organization to stimulate by means of rambles, lectures, film shows and instruction by experienced naturalists an interest in the locality in birds and wildlife. They had few records of bird life in the interior. They had a good season at Skokholm which had been filled to capacity, although the number of day visitors was limited through the society not having their own boat. They had ringed 2000 birds last year. Naturalists from Sweden and Switzerland were amongst the foreign visitors.

Mr. John Barrett, a former RAF Wing Commander, who has undertaken the duties of Warden at Dale Fort was introduced to the members. He said that the CPFS and the Field Society, working together, could accomplish something very important, something that would be the envy of the world.

Dale Fort was to be the mainland base for visitors to Skokholm from 1947 to 1965. This was a major part of the field centre’s original raison d’etre. Weather permitting, every Thursday an early morning boat would leave Dale Fort Jetty to take new visitors and remove the old ones from the island. Years later (1998), Ruth Barrett’s abiding memory of Skokholm was the ridiculously early start required on Skokholm days. Recently, (11.09.14), Dale Fort was privileged to be visited by Mr and Mrs Barry Page. (Barry was Deputy Warden and Mrs Page was the Bursar in the early 1960s). One of Mr Page’s abiding memories also concerned Skokholm, because he had to get up even earlier on Thursdays and drive to Milford Station to meet the 0430 train to collect the next set of visitors to the island.

In 1969 the lease on Skokholm Island ran out.  Hugh Lloyd-Philips of Dale Castle who owned the island renewed the lease for the West Wales Naturalist Trust (ex-WWFS) but was not happy about the continued involvement of the Field Studies Council. There had been an almighty row over a bungalow, which had been built on the island early in 1967. The island’s owner had not given permission for this erection. The Field Studies Council didn’t think they needed his permission and put it up anyway. It turned out that Lloyd-Philips was right and he insisted that it be pulled down. This was duly done by (much to their amazement) the same builders who had just, with extreme difficulty, put it up. David Stanbury, a regular visitor to the island since 1964 and former Chairman of the Executive Committee of the FSC once informed me that he was one of the few people to actually spend a night in this ill-fated structure. The unhappy result was the cessation of Dale Fort’s formal connection with Skokholm.

Skok bungalow   It had been more than 20 years since my only visit to Skokholm that actually involved going ashore. We’d like to thank Richard The Warden for having us and for not blaming current Dale Fort Staff for the bungalow debacle. We hope to visit this beautiful, interesting place much more frequently in future.



Dale Fort Blog Number 36

5 09 2014

Stats for Twits

A simple guide to the use of hypothesis testing statistics

This blog is not a comprehensive guide to statistics. It is intended to remind/inform you of the general format and structure of hypothesis testing statistics. It does not tell how to do any actual tests.

Even if you think you know nothing about statistics, it’s almost certain that you do. You will probably have heard of terms like the “average” value or maybe the “range” of some data or possibly its “standard deviation” or “variance”. All of these things tell you something about a set of data, they are known as descriptive statistics. The statistics we are concerned with here are called hypothesis-testing statistics. For the most part you will be using them to compare one set of data with another set of data.


The format you follow is similar for most of these tests:

Invent a null hypothesis

Using your devastating powers of observation, you have noticed that adult humans seem on the whole to be taller than baby ones. You could easily investigate this by measuring some of each kind and comparing the average values of the two sets of data.


An hypothesis is simply a statement which offers an explanation of your observations. In this case our experimental hypothesis might be that all adult humans have had special cosmetic surgery to lengthen their legs and make them taller than babies. Alternatively, we might suggest that adults have been around for longer and therefore have grown bigger. Both of these would be experimental hypotheses, the latter being the more reasonable one.


A null hypothesis is a special sort of hypothesis which you invent purely for the purpose of doing the statistical test. It does not have to agree with your experimental hypothesis. The word null means a condition of nothingness or lacking any distinction. A null hypothesis is sometimes called an hypothesis of no difference.   It is always stated as though there were no difference between the two things you are comparing. If we were doing a test that compared our two average (or mean) heights a suitable null hypothesis would be:

   There is no significant difference between the means of the two sets of data

Remember, it might be obvious that there is a difference but you state it like this anyway. Having done the statistical test you will end up either accepting or rejecting this statement.

Calculate the value of the test statistic

All the tests do something different but the general pattern of what you do is the same. The next thing you do is use your data to calculate a value of the test statistic you are using (this will have a name, usually a letter like “t”, “U”, “rs”). You calculate a value that is specific for your data.

Find the critical value of the test statistic

Statisticians are very clever (except for Heronimous Bing of Oxford, he is thick), they have spent a long time working out what are known as critical values of test statistics for all combinations of circumstances and sets of data. You must extract from one of their tables of critical values the value that applies to your combination of circumstances. What the value is depends on the number of items of data in each data set and the degree of precision you want to use in either accepting or rejecting your null hypothesis. This is the real value of these techniques, they allow you to say how certain you are when you either accept or reject the null hypothesis. You get to choose how certain you want to be.

Here is part of a table of critical values for a statistic called Spearman’s rank correlation coefficient:

Spearman's partial table of critical values

You enter the table at the appropriate number of pairs of data (let’s say we have 9 pairs of data). The critical value lies somewhere along this row.

You will have noticed that each column is headed with a percentage significance level. This is the part where you get to pick the degree of precision or confidence you want in either accepting or rejecting your null hypothesis.

Lets us say that you wanted to be as certain as you could be (using our table above) that you would be correct in accepting or rejecting your null hypothesis. Enter the table at the 1% significance column and find the appropriate critical value by going along the 9 pairs of data row. As you can see the critical value is 0.833.

With this particular test, if the value you’ve calculated for your own data is the same or bigger than this you reject the null hypothesis. If the value for your data is smaller than the critical value you accept the null hypothesis. In accepting or rejecting it at the 1% significance level you are saying: “If I did this test a very large number of times I would expect to be correct in accepting or rejecting my null hypothesis 99% of the time. I would expect a different result due to chance only 1% of the time”. Put simply (and not quite accurately but hopefully you know what I mean): “I’m 99% certain that I’m right in accepting or rejecting my null hypothesis”.

If you are not so concerned with being near certain you can pick a bigger % significance level. If you picked the 5% level the critical value would be 0.683. This is smaller than the critical value for 1% significance and it will be easier for your value (calculated from your own data) to beat it and reject the hypothesis of no difference. However if you do it at this level you would expect different results due to chance 5% of the time. In other words 95 times out of a 100 you’d expect to be correct in accepting or rejecting your null hypothesis. 5 times out of 100 you’d expect a different result due to chance.

There is no law about what level of significance you choose but given the inherent variability of biological systems (or cussedness) it has become generally accepted that a level of 5% is acceptable for field data.

Tests you might use and what they do:

A t-test will tell you if the means of two sets of continuous data, with interval level measurements are significantly different to one another. (If you have a big sample (25+) you can use it for count data as well). Some people call it a z test when you have a big sample but we use the same formulae. For any T test you do the null hypothesis will be: There is no significant difference between the means of the 2 sets of data

A Mann-Whitney U-Test compares the medians of two sets of data and can be used on interval or ordinal data. You can also use it on data that is not normally distributed (unlike a t-test) and for as few as four pieces of data in each sample. For any Mann-Whitney U-Test you do the null hypothesis will be: There is no significant difference between the medians of the two sets of data

A chi2 test does a lot of things but for the most part we use it in a simple way to see if an observed set of data (which has to be counts of things in categories (frequencies)) differs significantly from what we might expect, given our null hypothesis. For any chi2 test you do the null hypothesis will be: There is no significant difference between the observed and the expected frequencies

Spearman’s rank correlation coefficient (snappy name eh?) will tell you whether 2 variables are correlated. I.e. Does one variable change as the other one changes? It will tell you whether the relationship is positive (both go up together) or negative (one goes up as the other goes down) and the strength of any correlation. For any Rearman’s spank correlation coefficient you do the null hypothesis will be: There is no significant correlation between the 2 variables

It conveys a much better impression that you know what you are doing if you customize the general null hypothesis to make it pertinent to your own investigation.  For example:

There is no significant difference in mean mass of customers patronizing MacSmug’s Lettuce Emporium and customers patronizing MacBloater’s Land of Grease Burger Bar

The t-test and U-test are both looking for differences between two sets of data. The chi2 test and Spearman’s rank correlation coefficient are both looking for associations between two sets of data.

Finally,  Greek letters do not seem to be catered for by this blog-host so here’s picture of what chi-squared looks like in the original Greek:chi squared

Watch out for the next blog, where we’ll live life even closer to the edge………



Dale Fort Blog Contents 1 – 39

4 09 2014

Dale Fort Blog Contents

Number 1

All about nematodes


Number 2

3 You Tube clips:

Starlings at Mabesgate

Error Bars in Excel 2007

Measuring Heights on Seashores


Number 3

The History of Dale Fort part 1 (all about the rocks)


Number 4

The History of Dale Fort part 2  (the construction  materials of Dale Fort).  Far more exciting than it sounds, you won’t want to miss it, go there NOW


Number 5

Sargassum muticum in Britain (with a video on how it makes babies)


Number 6

The History of Dale Fort part 3, The First Humans


Number 7

Silverfish and their ways


Number 8

The fat-bellied book chewer


Number 9

Seaweed research at Dale Fort


Number 10

Wormhole research at Dale Fort


Number 11

Limpets and their mysterious ways


Number 12

Anne, Bridget, Cadoc and David


Number 13

St David and his friend Elvis


Number 14

Dancing bananas:  Just how many are there?


Number 15

Six-legged female vampires


Number 16

Cry Havoc!  And let loose the dogs of accountancy………The History of Dale Fort part 6


Number 17

Wee timorous beasties


Number 18

A magical island where strange events take place


 Number 19

The many faces of the mean (and by the way Bill, smoking is neither big nor clever)


Number 20

Deviant Beards and other exciting topics


Number 21

Welsh in 10 Minutes (ddim yn rhugl)


Number 22

Halloween Special.  Read it with the light on……..


Number 23

Back to matters more prosaic but useful I hope.  How to get a quick frequency distribution histogram out of Excel 2007


Number 24

Spectacular weather, huge waves, the demise of a bridge, the scaring of a photographer and much more


Number 25

BARNACLES  so much more than just the worst part of a keel-hauling


Number 26

NUNZILLA makes her debut:  She knows about seaweeds, she’s a nun, she’s clockwork, she breaths fire.   What more could you want?  More history, that’s what and you’ll get it in Blog 26


Number 27

TARDIGRADES…….No it’s not a Norwegian swearword.  Their common name is water bears and they are astonishing creatures.  Read about them and then construct your own with our free build your own tardigrade kit.  Ordvykejys….now that’s a Norwegian swear word.


Number 28

House Dust Mites…..I realise that it would be hard to top the spacetastic subjects of the previous blog but house dust mites are still extremely interesting creatures that eat human flesh and give you allergies.  Read all about them here.


Number 29

WOODWORM All you could wish to know and probably more about about the unsung heroes of the Anti-Furniture League


Number 30

Spider Blog,  Spider Blog,   Does whatever a Spider Blog does…..


Number 31

The History of Dale Fort Part the Eighth.  200 years in 1200 words, suitable for home freezing.


Number 32

Red and yellow and not pink and green, orange and not purple and blue……..seaweeds and light


Number 33

Rocky shore monitoring at Dale Fort Part 1.  Channelled wrack and rough winkles have rarely been given so much attention and for so long.


Number 34

Rocky shore monitoring at Dale Fort Part 2.  Species diversity, small winkles, limpets, barnacles and purple topshells.  Possibly more than you ever thought you wanted to know about these fascinating creatures


Number 35

The History of Dale Fort Part the Ninth:  Charles Louis Napoleon,  80 cigarettes a day,  The Ladies of Royal Ballet, Beating up Chartists, Emperor of France, Kidnapper of vultures, World Ping-Pong Champion 1846 (OK I made the last one up)…what a guy…


Number 36

STATS for TWITS.                                                                                                                                                              A simple guide to how hypothesis testing statistics work and some common tests and what they do. Could any blog be more fun than that?   Well yes, actually but I hope you’ll find it useful nonetheless.


Number 37

A visit to another magical island (see also Blog Number 18) and some lesser known aspects of its history


Number 38

Nadolig Llawen pawb

Merry Christmas Everybody (c N. Holder 1973)


Number 39

One of the great things about geography at Dale Fort is that you get to go to some of the  best and most interesting places .  Here we visit The Preseli Mountains to study The Afon Synfynwy (translation: The river who runs back up the slope to the church where the goat is tied to the tree with the wasp’s nest on the 3rd bough from the top by the church with the wobbly pew at the back)


Dale Fort Blog Number 35

4 09 2014

The History of Dale Fort

Part the Ninth

Blog 32 ended with the defeat of Tate and his Legion Noire.   Napoleon Bonaparte was finally defeated  at Waterloo in 1815 and this really ought to have resulted in a cessation of hostilities between Britain and France.  There was however his nephew Charles Louis Napoleon to deal with first.

Shipbuilding in Milford Haven

By 1800 there were around 30 small shipyards on the shores of Milford Haven. These had developed during the Napoleonic Wars. The existing Royal Dockyards were intermittently busy with repairs and maintenance of the expanded British Fleet, which was trying to blockade the major ports of Europe against the French Navy. These yards were on permanent standby for this work. The Royal Navy therefore developed a policy of having its new ships built at private yards, where interruptions for repairs and re-fitting would not occur.

Milford Haven was used because it had convenient access to oak, iron and a suitable labour force. The Royal Navy had secured the services of the renowned (French) naval architect Barrallier who was in charge of the dockyard. The dockyard was defended by two 24-pounders at Milford and a larger battery at Hakin (an established village before the building of Milford Haven) comprising six 32-pounders.

SB ML 32lb In 1809 Sir Charles Greville, the founder of Milford Haven agreed with the Navy a price of £4466 for a piece of land for the building of a new Royal Dockyard. Shortly after Greville died and his brother Robert took over. Robert demanded more money and refused to complete the contract. The Navy decided instead to move across the river to Pater where there was a government owned piece of land that they could use. By 1814 all their facilities had been moved to the new site, which was now called Pembroke Dock. According to J.F.Rees in The Story of Milford this deprived Milford of its one great chance for prosperity

Charles Greville 1809George, The Prince Regent, signed the order that officially created Pembroke Dock in 1815. The Royal Navy was by far the single most expensive commitment of government and for more than 100 years Pembroke Dock was to be an extremely important facility. There were 13 slipways for building on, (more than any other yard) and more than 250 ships were built there. These ranged from small cutters to massive ships like HMS Howe which at 6.5 thousand tons was twice the size of Nelson’s flagship Victory. The yard initiated the era of steel ships with the launch of HMS Iris in 1877. HMS Drake launched in 1901 was 553.5 feet long.

Pembroke dockyard 1820 labelledThere had been little serious attempt to defend Milford Haven since Elizabethan times. Britain had just finished its biggest ever series of wars against Napoleon’s France and memories of him remained strong. It was only 25 years since Tate’s failed invasion at Fishguard (see Blog Number 31 ) and Britain now had a major Dockyard on the shores of the largely unprotected Milford Haven.

Charles Louis Napoleon

Events in France were to confirm the views of the British that they should continue to be wary of the threat from over the Channel. The sole remaining Bonaparte was Charles Louis Napoleon Bonaparte, the nephew of the “real” Napoleon. As a result of his link with Napoleon Bonaparte, Charles Louis had an overwhelming sense of his own destiny. He set about promulgating the romantic side of Bonapartism by publishing various political pamphlets. Twice he tried and failed to seize power in France. In 1836 he attempted to incite mutiny among French troops at Strasburg.

He was deported to New York, from whence he travelled to London. In 1840 he landed at Boulogne with a force of 50 men and a vulture (the unfortunate bird was acting as a substitute for the Imperial Eagle). A scuffle ensued and Charles Louis made his escape by diving into the sea. He was plucked from the water and arrested as he swam for a nearby rowing boat. He was now seen as something of a joke in France, but he cut a dignified figure at his trial. His defence was that since his uncle (Napoleon Bonaparte) had attained power by plebiscite and this had never been revoked, a Bonaparte (himself) should still be in charge. The French King Louis Phillipe was lenient and Charles Louis’ punishment was to be confined to a suit of rooms in the fort at Ham. The Imperial Vulture was sent to the Paris Zoo, where despite being entirely innocent it too was confined.

Whilst imprisoned Charles Louis wrote several popular books outlining social reforms and became well  thought of by many sections of French society. In 1846 he affected his escape. This he did by totally destroying his rooms.   When workmen arrived to repair the damage Charles Louis put a plank on his shoulder and simply walked out. He escaped to London where he joined the Special Constabulary and helped them bash up The Chartists. He also worked his way through 80 cigarettes a day and the ladies of the Royal Ballet.

ChartistRiot            Charles Louis Napoleon and his chums beat up some poor people who would like to vote

The monarchy of Louis Philippe was under pressure for several reasons: Firstly, the public remembered the glory days of Napoleon Bonaparte. By comparison Louis Philippe’s conservative foreign policy was seen as capitulating to England. Secondly, social conditions were poor for the majority and unemployment was rampant. Thirdly, socialism and expansion of the franchise were ideas increasing in popularity. In Britain, the Chartists were demanding an expanded franchise. Louis Philippe provoked further unease in Britain by appointing his son, Prince de Joinville as head of the French Navy. Joinville had a record of anti-British sentiment and the French Navy was in a period of expansion.

As early as 1845 Palmerston had addressed the House of Commons pointing out that the new technologies of steam ships and railways rendered Britain’s natural defence – the English Channel virtually useless. Palmerston said: Steam navigation has rendered that which was before impassable by a military force nothing more than a river passable by a steam bridge. Railways would permit the mobilization and transport of troops in numbers and at speeds never before allowed for.

Palmerston labelledTowards the end of 1846 General Sir John Fox Burgoyne published a report on the state of Britain’s coastal defences. (Observations on the possible results of a war with France under our present system of military preparation). Burgoyne was Inspector General of Fortifications and his report concluded that the French Navy could gain control of the Channel for long enough to land a massive army on the coast of Britain. Burgoyne recommended modernization of fortresses and naval dockyards. A month later Palmerston published a report extolling a similarly pessimistic view. In early 1847 the Duke of Wellington published a discourse along similar lines. Wellington’s report was leaked to the press and stimulated public panic and concern.

The worry about France was temporarily eased when King Louis Philipe abdicated in 1848 and a provisional government took over (The Second Republic). The provisional government initiated work programmes intended to improve the lot of the working classes. Most of these failed. Dissatisfaction came to a head when the Parisian working class rose up, erected barricades and demanded a better deal. The military and the rest of France did not see why this should be tolerated and 10,000 deaths and serious injuries were the result. Thousands were deported. The Second Republic was not off to a good start and conditions were ideal for the emergence of a new leader.

Charles Louis Napoleon now returned to France and in December 1848 won the elections for President by a landslide. The connection with Napoleon Bonaparte together with his previously published plans for social reform had won him the Presidency. Charles Louis’ period in office was due to end by law in December 1852. On December 2nd 1851 he staged a coup d’etat. He then asked the people for a mandate allowing him to remain as president for ten more years.

The results were as follows: Out of 8 million voters, 7.4 million voted for him and 0.6 million against. 500 people were killed, 27,000 arrested and 10,000 deported. Charles Louis justified it all thus: the votes of 7 million have granted me absolution. He spent the next year touring France and generally becoming more popular by virtue of his social reforms.

Calls were being made for him to become Emperor. Given his sense of destiny and his lineage one would not expect those calls to have gone unheeded. Another plebiscite was asked for and granted. Charles Louis dissolved The Second Republic and began The Second Empire. This was when he assumed the title Napoleon III. The second plebiscite marked the end of democracy in France. The Emperor Napoleon III now said I don’t mind being baptized in the waters of universal suffrage, but I refuse to live with my feet in them.

 CNP and E

All this caused more consternation in Britain. Palmerston was again at the forefront of those who insisted that there was a real possibility of an invasion by France. It was believed that 50-60,000 troops could be landed from Cherbourg in a single night. Although there was no evidence of the massive build up of shipping required to transport all these men, panic was still the result.

The Duke of Wellington was also concerned about the Americans. The Oregon Border Dispute of the mid 1840s was an argument between the British Government and the USA as to the precise placement of the Canadian border. Some American politicians made speeches tacitly threatening the British with military force. Lord Aberdeen, the Foreign Secretary was dispatched to negotiate.   In his History of the English Speaking Peoples Churchill states that the solution was arrived at in June 1846 as a result of Aberdeen’s accommodating nature. The Duke of Wellington was not known for his accommodating nature and felt that there existed a real threat from the USA. Any invading force would certainly approach the West Coast of Britain possibly via Ireland. The nearest relief was at Cardiff, at least two days away and there was a huge and vulnerable dockyard at Pembroke Dock.

The wave of panic that ensued hurried the government into a programme of improving coastal fortifications in The Solent, The Channel Islands and Milford Haven. After 200 years of neglect the defences of Milford Haven were being taken seriously.

Watch future blogs for what happened next.

Dale Fort Blog Number 34

4 09 2014

Rocky Shore Monitoring at Dale Fort

1996 – 2014

Part the Second

Species Diversity on the 3 Transects 1996 – 2014

1) Dale Fort Jetty Beach

Jetty total spp 1996 -2014The numbers of species were low immediately after the 1996 oil spill. This was not a causal effect. The first survey of the Dale Fort Jetty Beach transect was carried out before any oiling occurred (year zero on the graph above). In fact by one year after the spill numbers of species had actually increased. Numbers peaked in 2013 and declined slightly in 2014

2) Castle Beach

Total spp castle 1996 - 2014  The year after the oil spill species numbers had increased and following that remained very consistent until 2014 (last point on the graph above) when numbers peaked at 39 species.

3) Monkhaven

Monk toitak spp 1996 - 2014No effects of the oil spill on total species numbers at Monkhaven were evident. The apparent decline in 2003 (6th point from left on the graph above) was due to huge swells preventing safe access to the lower three sites. For the past decade species numbers have been extremely consistent at Monkhaven.




Total Number of Species Found on all 3 Sites, 1996 – 2014

3 spp graphsThe general pattern in terms of species diversity seems to be one of increasing stability with increasing exposure. This seemed strange in that the more stressful environment seems to have the most consistent number of species. Therefore, it was decided to look at a species which had very variable numbers see if the pattern of stability with increasing exposure was repeated at a single species level.

Melarhaphe neritoides

Melarhaphe neritoides is a small snail that lives on the upper parts of rocky shores, browsing on micro-algae and lichens. It favours exposed conditions but is also found at the sheltered Dale Fort Jetty site.

It was chosen because its numbers vary a lot from year to year. If similar patterns of stability are seen in this species’ abundance as the patterns of stability seen for all species at the sites (see above) it suggests that these patterns are real and not an artefact of sampling. The general pattern is indeed the same. Jetty Beach was the most variable by far and Castle Beach and Monkhaven were remarkably consistent. There was a peak in numbers at both Castle Beach and Monkhaven in 2003.

Melarhaphe 3 sites 1996 - 2014Limpets

Limpets are large, obvious, common, long-lived mainly herbivorous animals that occupy an extensive vertical range on rocky shores of all degrees of exposure. They are therefore ideal subjects for rocky shore monitoring.


Abundance of Patella vulgata (common limpet) on the 3 transects.

1) Dale Fort Jetty Beach

Limpets Jetty 1996 -2014

In terms of total numbers there appeared to be a cycle of 10 – 12 years from peak to minimum abundance of limpets on Jetty Beach. An increase over the next few years would provide evidence that this is a true cyclic phenomenon.

The numbers of animals at each site (lower graph) are rather variable. It is noticeable that the first year of monitoring (red line) had the lowest numbers in the middle shore and this may be an effect of oil deposition. Limpet casualties were evident during 1996.

2) Castle Beach

Limpets Castle 1996 -2014

At Castle Beach there was less evidence of cyclic behaviour in terms of total numbers of limpets. Any cycle that might be there would seem to be a shorter one of 5 – 7 years or so. This may be a reflection of increased exposure and intra-specific competition resulting in reduced longevity for the population as a whole at Castle Beach.

The numbers at each site on the Castle Beach transect were extremely consistent from year to year. The earliest, latest, and middle year records all tracked the 19 year mean very closely (see lower graph).

3) Monkhaven

Monk limpets 1996 -2014Following the possible patterns of Dale Fort Jetty Beach and Castle Beach the total numbers of limpets on the Monkhaven transect showed some evidence of cyclic behaviour. Interestingly, there was a possible trend of diminution of length of cycle with increasing exposure. The total numbers cycle at Monkhaven seems to be one of 4 – 5 years, slightly shorter than the cycle at Castle Beach which in turn was slightly shorter than the one at Dale Fort Jetty Beach (see Dale Fort Jetty Beach upper chart).

In common with the trends in total numbers the numbers of animals at each site at Monkhaven showed the most consistent pattern of all with very little change from year to year (see Monkhaven lower graph).

The Limpets of Site 5 Castle Beach

All sites are recorded photographically to enable further analysis. A middle shore site at Castle Beach was selected for a detailed limpet-size investigation. This site proved easy to photograph consistently.   Initially this was done with photographic film. Prints were examined under a Wild binocular microscope and the maximum length of all positively identified animals was measured using Vernier Callipers. Actual size was determined using the 0.5m sides of the quadrats as a scale. From 2002 photographs were digital and large prints negated the need for a microscope.

Limpets site 5 castle 1996 - 2014Mean maximum diameter of limpets at Site 5 on the Castle Beach transect seems to be exhibiting cyclic behaviour. There are about 8 – 10 years between the largest mean maximum diameter and smallest mean maximum diameter. It seemed reasonable that mean maximum diameter might be negatively correlated with limpet density.   The figures seem to indicate that peaks in limpet density might correspond with troughs in mean maximum diameter. This is particularly so between 2006 and 2013. However, regression analysis for the years 2006 to 2013 indicates this not to be the case (see below)




















Limpet size density CB site 5 2006 2013There seems to be no simple correlation between limpet size and density, a conclusion similar to that of Ballantine (1961):


” There is no direct relationship between mean size and population density (expressed as weight per occupied area) in P. vulgata.”


W.J. BALLANTINE (1961) PhD thesis


Other workers have found the opposite:


“For site A, a Spearman’s rank correlation coefficient of -0.84 confirms that the inverse

relationship between mean limpet size and limpet density was significant at the 1% level.”


Field Studies, 10, (2003) 579 – 599




It is difficult to make any firm conclusions from the above. It seems reasonable to suppose though that there is no simple relationship between limpet size and density. Inter-specific biotoc interactions are probably important as are interactions with the physical




environment. It was noted that the lowest barnacle density recorded coincided with the smallest limpet mean maximum diameter and a low limpet density (see below).

Barnacle density site 5 castle 1996 - 2014This would imply a that there might be extra space available on the rock for species to occupy in 2014. Limpet numbers might therefore expand over the next few years. On the other hand barnacles tend to settle in the spring and summer months while limpets tend to settle in the autumn. Could it be that barnacles will already be occupying the space by the time of the next limpet settlement? The most abundant mid-shore barnacle is Semibalanus balanoides. This species requires a month of mean water temperature below 7.2 o C before it can breed ( MarLin website, 2014). This temperature was not achieved during 2014 (Data logger next to site 5). Could this reduce the breeding success of S. balanoides?   S. balanoides is an osmoconformer. 2013 – 2014 saw huge rainfall, could this have increased barnacle mortality? If as some authorities believe sea temperatures are rising, then might S. balanoides be replaced at lower shore levels by the warm water species Chthamalus stellatus? These questions and many more will only be answered by further monitoring.



Gibbula umbilicalis (purple topshell) at Castle Beach

This species was of interest because it is thought to be a warm water species that is currently extending its range northwards. This has been seen by some authorities as evidence that sea temperatures are rising. It is a small herbivorous snail that occupies the middle to lower parts of sheltered to moderately exposed rocky shores.

Purple tops at castle 1996 - 2014 There was a drop to one individual about a year after the oil spill. This was followed by an increase that fluctuated from year to year but overall numbers climbed to a maximum of 15 after 10 years. G.umbilicalis seemed to be increasing year on year. However, 2007 and 2008 changed all that, because the numbers were decreasing again. 2009 to 2011 saw a rapid increase and numbers peaked at 29 (2009 – 10 was the coldest winter for decades). 2011 to 2013 saw another increase and 2014 a decrease. The causal factors responsible for this variation are unknown. G. umbilicalis is however an extremely mobile species. Factors like weather conditions are likely to have a huge influence on count data e.g. As a result of animals seeking out appropriate microhabitats like crevices during dry, warm weather. This renders them very difficult to detect. 2014 was the stormiest year for decades and the reduction in numbers might be due to increased mortality due to excessive wave action.


There is a paucity of long-term, reliable, quantitative data even from shores that have been studied for decades.

The most important variable in most data sets is the people that collected the data.

The Dale Fort data set has the unusual feature that the same person (the author) has collected the data from the beginning. This should ensure maximum consistency.

Methodologies should strive for consistency and repeatability to try to reduce the effects of personnel changes.

The very strong ecotone caused by the rise and fall of the tide overwhelms most changes you can represent using multivariate analysis.

If/when the next oil spill occurs we will be able to make much more definite statements about the effects, particularly on limpets but also for several other species.

Seashores are one of the few natural habitats that remain in the UK. Their inhabitants indicate the state of the seas and as we depend, for our very existence, on the seas they are worthy of study.

Continuing to add to this long-term data set will facilitate the recognition and interpretation of any anthropogenic or other changes in the future.