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The dorsal fin of a starry smooth-hound shark with a research tag, by Joost van Uffelen

Tagging sharks in the Netherlands

Travelling all over the world to see and photograph sharks and other big marine life sometimes makes me a bit blind to our Dutch wildlife.

Making up for that I signed up for the SharkaTag event (pronounced like sharkattack, but different :-) ) joining the boat organized by the Dutch Shark Society.

SharkaTag has been introduced in the Netherlands after its first research projects were held in the past years in the UK.

By catching, tagging and releasing sharks more is learned about their behavior, which ultimately should lead to knowledge on how to protect these animals that play a vital role in the marine ecosystem.

Data that is gathered helps in uncovering facts about their migration patterns, population size and population dynamics.

Shark populations have dropped dramatically worldwide due to targeted and non-targeted (by-catch) fisheries; a good reason to assess their conservation status and the progress in recovery that some of the species should make.

That sharks are "hot" becomes clear when looking at massive TV productions like "Shark Week" of Discovery Channel. A Dutch national TV crew also came out to film the SharkaTag event, again, emphasizing the interest on sharks in general.

Neeltje Jans

At the Dutch storm barrier (aka stormvloedkering) the North Sea water flows in and out of the Oosterschelde (a big estuary system) through dynamic hatches.

The hatches (42m long and 6-12m high) are usually open, but are closed when a severe storm hits the coastline.

They are lifted with hydraulic systems that allow not only to lower and raise the hatches, but also to put extra pressure on them during a storm to keep them down.

The storm barrier was built after the big flood of 1953, in which 1836 people lost their lives. A storm in combination with springtide swept a major flood into the province of Zeeland with great destruction.

Old and undermaintained dikes gave way to the immense power of the sea and nearly the complete province of Zeeland submerged. In an effort to prevent this from happening again the "Stormvloedkering" was built.

It is a pretty cool sight to behold and a master piece of engineering if you ask me. I'd recommend anybody to visit the museum when visiting the Netherlands.

BTW: earlier this year a humpback whale swam through one of the hatches of the barrier and entered the estuary only to swim back out a few days later despite concerns of the public for the health of the animal!

Catching Dutch sharks!

The entrance of the Oosterschelde is also home to a few different species of sharks during summertime. Both cat and houndshark species find their home in the North Sea and the estuaries.  

We caught starry smooth-hound sharks (aka "gladde haai" in Dutch), but also other sharks were caught during the week. The starry smooth-hound sharks grow up to 1,40m, a decent size shark if you ask me!

Once taken on board the sharks would be put in a oxygenated tub first. Then they would be measured and the needed details were logged. Also the depth, date and time of catch were recorded.

Next was the tagging process. The sharks were tagged with a plastic tag with a unique number and the phonenumber plus the website of the research institute.

Before they knew it the sharks were back in the water on their way to the seafloor where they forage for crustaceans and small fish.

In the past years a total of 1800 starry smooth-hound sharks have been tagged of which 60 have been recaptured. One of them was tagged in the Netherlands and was recaptured off the coast of South-West France at the border with Spain!

Pretty cool discovery.. It was nice to be taking part in this research program and even more so because these were Dutch sharks!

By the way: of the four sharks that were caught during the day on our boat, only one of them was a male shark.

Male sharks can be distinguished from female sharks by the presence of their claspers (sexual organs). Yes... sharks have two!

Sometimes I can't help but wonder where shark #7753 is at this moment.. ;-)

 

joostvanuffelen's picture
About the Author:
Joost loves the oceans, travelling and (underwater)photography. Combining those three elements he creates ocean art, travel reports and ocean photo stories...


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