With the higher than normal winds curtailing a lot of boat fishing pretty much since the Tagathon event in November, I’d been dying to get back up to my boat at Loch Sunart for a couple of days to see what was about. As always, I’d been watching the weather forecast for days beforehand and it was looking good for the weekend with SE winds below 10mph for both days. Billy McCormack was to be my crew mate and we were joined for Saturday by Darren, Paul and Graham on Paisley Pete – another Warrior 165.

Launching at Salen (http://www.salenjetty.co.uk/) on Saturday went as smoothly as usual and we had lines down at my favourite mark for just before 9.30. The others were out slightly earlier and Darren had been straight into a decent fish when he boated a nice spurdog at 10lb 10oz. We only had to wait half an hour ourselves for our first “banger” to show and this was to be the pattern for the rest of the day.

There was a brief respite from the spurdogs around slack low water about 2.30 in the afternoon. When I say “respite”, a large skate decided to devour a single calamari and battle commenced. We began to think this was a male fish as it did a lot of thrashing about and nodding around the seabed where it held solidly for 20 minutes. Very gently. I managed to get a few half turns of line back and it was soon rising slowly at a rate of two reel turns per rod lift. This mark was 210 feet deep which was 90 reel turns to my leader knot. I managed to get it about two thirds of the way to the surface when the brand new braid unfortunately snapped and it was gone.

As the flood tide began, the spurs returned. Many were around the 7-8lb size and all but two were female. We had several “doubles” with the biggest one of the day bending the scales to 14lb 9oz. It was decided to fish on into the dark and return to moor at the jetty by GPS. Our final tally for the day was a fantastic 35 spurdogs falling to squid and mackerel baits, 20 of which are now fitted with SSTP micro tags. All were clean fish apart from one which had a small bug clinging to it’s flank. I’ll hopefully find out from the kindly boffins at Marine Scotland what it was?

Over on Paisley Pete, they’d packed up to go home earlier on, but still ended with 12 tagged fish including one recapture. This included five into double figures. Other species we landed were a small thornback ray, a few small whiting and numerous LSDs.

Once again, we stayed with Nikki and Richard at the excellent Salen House B’n’B (http://www.salenhouse.co.uk/). After a hot shower at the digs, it was a short saunter up to the nearby Salen Hotel (http://www.salenhotel.co.uk/) for dinner, a very quiet shandy, a review of the photos we’d taken and to reflect on our good fortune. Being very dedicated anglers, we only had a couple of drinks and were of course in bed for 10pm (?????).

Sunday dawned colder and windier with my head feeling as though it had a Vulcan bomber performing very noisy destructive engine tests inside. I’m sure this must have been down to the balsamic vinegar I had on my chips the previous evening???? After a fantastic breakfast, it was back to the same mark we’d fished the previous day. Things didn’t go quite to plan though and it was lunchtime before I’d tagged the first decent spur of the day – a nice female of exactly 7lb. Surprisingly and disappointingly, this was to be our only biggie of the day. We fished several different marks up and down the loch, including some “exploring” work to the South of Carna island. After being liberally sprayed with bait, rain, food etc. for two days, the boat was tidied and lines were up for just after 4pm. The low water recovery was easy enough thanks to the deep water at the slipway and after securing everything it was off home, tired but happy.

Good fishing. Good company. Good weekend!

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3. Measure it !

The development of electronic tags opened up a wide range of new possibilities and allowed more detailed behavioural studies on short-term movements, migrations, diving behaviour and habitat use. Sharks in particular were identified as strong candidates for electronic tagging programmes due to their size, robustness and the toughness of their skin allowing external tags to be firmly anchored. To date electronic tags have been used to monitor the behaviour of many species of fish, sea bird, turtle and marine mammal.

Early electronic tagging projects aimed to provide basic information on shark movements and were carried out by fitting a transmitter to a shark and tracking it manually. Many projects now use static hydrophone receivers which are moored in areas of interest and continuously record the movements of any tagged sharks in the vicinity. One example of this is the common skate acoustic tagging project currently ongoing in the Sound of Jura.

This project used both acoustic pinger tags and data storage tags to monitor the movement of common skate in the Sound of Jura using an array of hydrophone receivers. The image below shows a common skate from the Sound of Jura fitted with a white data storage tag.

Data storage or archival tags have been used to identify changes in behaviour in response to seasonal or daily variations. Blue, shortfin mako and bigeye thresher sharks have shown pronounced variations in diving behaviour on a diel (24 hour) scale; sharks were found to make their deepest dives during daylight hours and spend the vast majority of the night in surface waters. This behaviour has also been observed in swordfish, bluefin tuna and black marlin. It is thought that periodic vertical movements in these predatory species are likely to be closely linked to the diel movements of prey species (which is in turn influenced by the vertical migration of zooplankton!)

Tags are generally fitted externally by attachment to dart tags or directly to fins or spines though other methods exist including attachment via a body harness.

Electronic tags have also been fitted internally by surgical implanting the tag in the body cavity of anaesthetized sharks or by hiding the tag in a piece of bait and feeding it to free swimming sharks. This image shows a spurdog from Loch Etive, Argyll being fitted with an acoustic tag as part of an ongoing tagging project in the area.

Since the first electronic tagging project in 1965 at least 26 species of shark have been tagged and their movements tracked. During this time electronic tags have become more sophisticated and can now perform a wide range of functions including monitoring body temperature, swimming speed, depth, salinity, light intensity and water temperature.

Some species of shark, particularly those that spend a significant amount of time at the surface, have been tracked using satellite tags. Satellite tags are generally attached to the shark by a tether and internal anchor, this allows the tag to float on the surface and emit radio waves that can be picked up by satellites allowing accurate positioning and tracking. Blue sharks, whale sharks and basking sharks have been tracked using satellite tags.

Some forms of satellite-tracked data storage tags can be set to “pop off” after a certain period of time, this allows the tag to detach from the shark and float to the surface where it can be located using a GPS and retrieved.

Data recorded using electronic tags can provide a valuable insight into the natural behaviour of sharks. Movements can generally be attributed to sexual activity, habitat characteristics and prey type and as such the data retrieved is often integral to developing sound fisheries management or conservation measures.

Tomorrows "History of Tagging" segment will look specifically at the growth of shark tagging projects around the World.

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2. Tagging porbeagle
3. An overview of the tags we use

In part 1 of this segment we will discuss the origins of fish tagging and the progressive sophistication of tagging technology in the years that followed.

The Origins of Tagging

Although it may seem like a relatively recent development, the fact is that people have been tagging fish since the early 1600’s. All early tagging projects involved salmonids, a particularly valuable source of food at the time. The earliest records of fish “"tagging” involved juvenile Atlantic salmon (Salmo salar) which were marked by tying coloured wool ribbons around the fishes tail to monitor movements from the river to sea. Although the methods may seem primitive when compared to modern day tagging projects that often employ a range of sophisticated electronic tags, the aims and principles of fish tagging projects have remained relatively unchanged for centuries.

By the 1800’s tagging methods had changed dramatically, although still largely focused on salmon a wide range of tags and alternative methods of tracking individual fish were now available. This included fin clippings and wire tags that could be attached to the fins, jaw, gill cover or tail of the fish.

In 1893, the Fisheries Board of Scotland initiated a project that tagged 600 Atlantic herring (Clupea harengus) using small barbed hooks, each of which carried a unique number inscribed on a small metal plate. However, despite the accolade of being the first known record of an attempt to tag and track a pelagic species, no tags were ever returned from this project!

The Peterson Disc Tag

The introduction of the Peterson disc tag in 1894 represented the single most significant development in fish tagging at the time. This simple tag is made up of two plastic buttons which are bound together by a pin made of plastic or metal and is generally placed on the fin of a fish similar to an ear piercing. The simple concept and ease of use allowed the expansion of tagging programmes and applications worldwide. The tags were initially used to monitor the movement of plaice in the North Sea but soon expanded to include cod, haddock, pollock and halibut.

Despite their popularity the Peterson disc tag is not without its problems, correct placement of the tag is crucial to ensure a strong hold but to not interfere with growth. Although tagging instructions generally advised that the tagger leave a 5mm gap between the tag and the body of the fish, shedding rates – particularly on juvenile or fast growing fish – were estimated at well above 50% per year.

Even to this day this Peterson disc style of tag remains popular and is generally considered the most widely used tag in the history of fish biology.

Rototags

The Peterson disc tag would eventually pave the way for the development of Rototags, a type of tag similar to that used for cattle. Rototags are applied in the same was as a Peterson disc: by piercing a small hole through the fin of the fish through which the tag is placed using a special applicator.

Rototags had much better retention rates that Peterson discs with a shedding rate of around 6-8% per year when applied correctly. However the tag also shared many problems of the Peterson disc, once again the tag could interfere with growth if incorrectly fitted and was prone to tearing out when the incorrectly applied.

The Rototag was the first tag used to track the movements of sharks, a revolutionary project that yielded mixed results.

Rototags were found to have the highest retention rate when fitted to the dorsal fish of shark species. However if the tag was placed too close to the base of the fin on fast growing species it was often found to cause irritation and many sharks in early tagging projects were recaptured with abraded dorsal fins suggesting that the irritation had caused the shark to rub on the sea bed in an attempt to dislodge the tag. Conversely if the Rototag was placed too far from the base of the dorsal fin the tag was prone to tearing out and shedding rates increased dramatically.

Rototags are still used today and can prove extremely effective when properly applied. In 1998 a Rototag was returned from a fish 28 years after the tag was applied making it one of the longest “times at liberty” ever recorded for an external tag, a testament to this style of tags suitability for shark tagging projects.

A smoothhound caught off Holyhead, Wales. A Small, white Rototag can clearly be seen on the sharks dorsal fin.

Dart Tags

The demand for an external tag that was easily visible but had a high retention rate led to the development of the “internal anchor” tag by Rounsefell in 1936. The tags developed almost 80 years ago by Rounsefell where the forerunner of modern day dart tags that are used by tagging programmes worldwide, including the SSTP.

The first dart tags had a stainless steel, “M” shaped head that was used to anchor the tag under the fish’s skin and were applied using a mounted needle. Dart tags opened up a wide range of possibilities, sharks could now be tagged in the water using a needle mounted on a long pole. This meant that larger species such as great white and whale sharks could now be easily tagged and that smaller species could be tagged without the stress and danger of capture and handling.

By the 1950’s cheap vinyl tubing was readily available and would eventually replace the stainless steel dart tags used previously. Subcutaneous nylon dart tags (as used by the SSTP) were first used in the 1960’s. Although retention rates were slightly lower than Rototags the benefits of using nylon dart tags far outweighed any possible drawbacks.

Dart tags are easily applied, have high retention rates, don’t interfere with growth and cause little irritation to the fish due to their small size and streamlined profile which creates very little friction in flowing water.

The blunt end of the nylon dart tag is inserted into a sharp canula (hollow needle) or tagging gun. The tag is then inserted at a 45° angle into the dorsal musculature of the fish to anchor the barb ensuring the head of the tag is pointing towards the head of the fish as shown below, this ensures that the tag remains streamlined and does not irritate the fish by creating resistance or vibrations when the fish swims. Once the canula is removed, a light pull on the tag sets the nylon barb and makes sure the tag is fixed in place.

Dart tags are now one of the most popular styles of tags and are used in tagging projects worldwide.

A spurdog with an SSTP nylon dart tag. The inset picture above shows a close up of the SSTP dart tag inserted into the dorsal musculature of a spurdog, each tag carries a unique number to allow individual fish to be identified. Additional data on size, sex and fish condition is recorded by the angler.

We hope you found this introduction to the history of fish tagging interesting! In part 2 of this segment we will look at the development of internal and electronic tags which would go on to have a significant influence on tagging shark tagging projects around the world.

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1. An overview of the tags we use
2. The Origins of Shark Tagging Programmes
3. Update: “Sores” on Tagged Skate

As tagging is a popular method for studying shark and skate species, there has been a lot of research into the effects of tags on elasmobranchs. Below is a synopsis from a piece of research work into this area.

In a study by Heupel & Bennett (1997), tissues from around tag sites were removed at time intervals ranging from 100 min to 284 days post-tagging. These samples showed acute and chronic responses to tagging.

Note: the use of the words ‘acute’ and ‘chronic’ do not refer to the severity of the reaction to the tag, but are makers of the time scale of the reaction with acute being short term effects (the insertion of the tag causing bleeding and tissue trauma) chronic refers to a reaction lasting longer than three months, in this case the permanent scar tissue.

Acute responses consisted of localized tissue breakdown and haemorrhaging, and occurred within the first few hours after tag insertion. At 10 h post-tagging, an intermediate response was apparent. This phase was characterized by further haemorrhaging and red and white blood cell movement into the wound area.

The chronic response observed in the 10–284-day post-tagging samples was characterized by fibrous tissue (scar tissue) formation to sequester the tag. Scar tissue presumably protects the adjacent musculature from further trauma produced by movement of the tag and provides a continuous barrier between the internal and external milieu.

Tissue repair appeared to progress consistently in all specimens and no secondary infections at the tag site were seen. Tagging produced only localized tissue disruption and did not appear to be detrimental to the long term health of individual sharks.

While healing from a tag wound may take longer than a normal wound due to irritation from the tag while scar tissue is formed, this doesn’t appear to be long term issue. There have been problems with previous tagging studies using inappropriate tags, such as the older fashioned ‘cattle ear’ tags, which restrict growth. Modern dart tags minimise irritation and in no way interfere with growth and are ideal for this type of work being used by many research programmes throughout the world.

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The Supreme Apex Predator:

Sharks have been around for over three hundred million years; The modern shark are highly evolved and have been unchanged for over one hundred million years. Human beings on the other hand have been around for little over one hundred thousand years and we are still evolving. Sharks are fish, and have little or no bone what-so-ever. Their skeleton consists of cartilage, similar to the top part of the human ear or nose.

There are over three hundred and sixty different kind of sharks, (not including Rays, Skates and Chimaeras which are a relative, being cartilaginous fish). One of the smallest being the Pygmy shark which is no more than 20 centimetres in length to the largest fish in the world the Whale-shark, which can reach staggering 12 metres; a fact made even more incredible when you remember that tiny plankton are its staple diet.

The general public have a fear and usually a total misconception about these amazing fish due largely to false press reports, Hollywood images, books and hear-say.

Perspective:

In fact 80% of sharks are totally harmless less than a metre in length and eat small fishes, crustaceans and invertebrates. A Shark will only attack if threatened or hungry. Humans are not on the menu unless we are mistaken for their natural food in murky water or on the surface where the Shark can only see shadows.

Globally there are about seventy reported shark attacks a year with about five or six being fatal but almost 200 people each year die from being struck by lightning; 600 people a year just falling out of bed; 2,800 from choking and 40,000 from snake bites. In fact you are more likely to suffer fatal injury from a bee sting.!

Quite possibly this unfounded information has contributed to the almost total annihilation of many species of Shark. It is estimated that around 70 million sharks are captured and killed annually, Not just for food (including shark fin soup) but as by-catch by fishermen trawling for other fish or trapped in tuna nets.

Shark fin soup:

One of the main reasons Sharks populations have been decimated in recent years is the appetite for the Chinese delicacy Shark Fin Soup. This dish is seen as a status symbol by rich Chinese and as China grows economically, the lust to prove one’s riches grows.

This trend has seen an ever increasing decline in Shark stocks.

Shark Fin Soup is considered beneficial to the health in many Asian countries. Also it is believed to prevent cancer, and be an aphrodisiac, although there is no scientific proof of these claims.

The way the sharks are captured and have their fins removed with a red hot blade and then thrown back into the sea, still alive, but unable to move and subsequently suffer an awful death, has had many claiming that this practice is unlawful and barbaric.

Shark fins may be sold for anything up to $500.

Impact:

Sharks are extremely vulnerable to over fishing due the fact they can take up to and over seven years to reach sexual maturity and do not give birth to hundreds of offspring like most other fish do.

Many species are now threatened and some are on the Global ICUN Red List, they include; The Blue Shark, Long Fin Mako, Great White Shark, Salmon Shark, Megamouth, Big eyed Sand-tiger and Crocodile Shark. Other sharks which find themselves on the endangered list are The Short Fin Mako, Thresher, Porbeagle and Silky shark are also in a real danger of extinction.

Adapted from : ArticlesBase.com – The Myths of the Shark!

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• There are more than 360 shark species.
• Sharks don’t always bite, just sometimes. Unlike humans sharks can not eat continuously in a row, so most often they bite to determine if the object is worth their digestive time. If they’ve bitten it and don’t think it is worth their while they will leave it and find something better. It is almost like us people inspecting a menu deciding what to eat.
• According to experiments it has been concluded that sharks may be afraid of dolphins.
• It is possible for female sharks to reproduce and give birth without having any physical contact with a male shark. Not always, but sometimes. One particular case has been documented of a female shark not having had contact with a male shark in three years, but has given birth to a baby shark without any parental DNA present; resulting in the newborn almost being an exact replica of his mother.
• In some cultures sharks are worshipped as gods.
• Sharks are said to have been living on earth for 400 million years.
• When a shark dies its cartilage dissolves and its teeth drop to the bottom of the ocean where it is covered with sandy sediment which prevents oxygen and destructive bacteria from reaching the tooth and that is why when you find a shark tooth fossil it is grey, black or brown and not white of colour.

Now whether you are fascinated by the shark specie, fear them or are just intrigued with them, the above facts should help give a little insight to this incredible creature.

Condensed from an article source: ArticlesBase.com – What You Should Know About Sharks

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A sharks sense of smell and sight is keen, it can both spot a one part per million of blood in seawater and can hear prey that is mile away. They also possesses electro receptor organs called Ampullae of Lorenzini which give them the greatest electrical sensitivity in all of the animal kingdom and help them find hidden prey.

Sharks are very peculiar beasts and it is no wonder people centuries over have been fascinated by them.  Many of us have mistakenly believed that sharks are significantly threat to human life. The greater number of the 370 species of sharks is harmless. Sharks can eat varieties of food.

The whale and basking sharks are the biggest species on this kind which are plankton eater and not a threat to humans, however, many of the bigger fast swimming sharks are true meat-eating animals and an astounding different and amount of food have been found in some of these marine creatures.

Acting as a scavengers as well as top carnivores, sharks are truly important in the ecology of the oceans. The reaction on shark’s attacks is often not based on facts but in emotions because shark attack on human is an exceptionally rare occurrence.

There are increasing dangers from humans that these sharks and their cartilaginous relatives, skates and rates are facing. For every person killed by a shark, over 23,000 tonnes of sharks and rays are killed through commercial fishing because we, humans target them for their meat and for their fins. They are also killed as by catch when some other species is in target.

Sharks have a low reproductive capacity and are not substituting their numbers as fast as humans are killing them. More protection for these marine creatures is needed before they are slaughtered to extinction.

Condensed from an article on: ArticlesBase.com – Shocking Shark Videos

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