Around 6h30m in the morning team WE LIKE SHARKS is prepared for another day out in the sea. It is essential to leave early and arrive on time to the Portimão submarine canyon, about 12 miles away from the coast. Expectations are high and phrases like “Today we will tag a big hammerhead shark!” echo in our minds. But deep down we know that in all likelihood we will encounter with the amazing blue sharks (Prionace glauca), a common shark species in Portugal.
When we reach the sampling area, fresh chumming is already prepared (sardines, mackerel, other small fish & sometimes tuna), the chum bucket is placed underwater and we wait for the sharks, boat-drifting along in the Atlantic Ocean currents. Meanwhile we think about sharks, we talk about sharks, we breathe sharks…
The chumming recipe*
João Santos getting his hands on the delicacies for our sharks (sardines & mackerels).
We use a utensil to cut and crush the fish and a large drilled bucket that delivers the chum near the surface. Thus, we release the fish scent, but we avoid the sharks to feed on it! This process is called “chumming”.
During these sea trips scientific data is collected. Water temperature, visibility, geographical position and depth, among other variables, allow us to acquire further knowledge on local sharks’ ecology and accomplish a viability study for shark ecotourism in the region.
The project has already undertaken twelve of the eighteen sea trips originally planned. Five trips returned a “zero” result, but all others had sharks around the boat, totalizing 20 blue shark sightings. Water temperature averaged around 18.6ºC. Visibility was higher during warmer months (from 15 to 25 meters) than during spring, when it was somewhat reduced and it seldom exceeded 10 meters. Depth ranged between 56 to 204 meters and chumming* is usually done during 4 to 5 hours.
The first shark appears… and the tagging challenge begins…
We must catch the shark alive and properly tag it, note down its biometric data (lengths and estimated weight) and free it back to the ocean as soon as possibly we can.
Shark Tagging Count Down Challenge
This video shows the first tagging of a blue shark (Prionace glauca). In order to cause the lowest stress, biologists who handled this female with approximately 1.44 m long, tried to make the manoeuvre during the shortest time as possible (approx. 6 minutes). During this first tagging, the oxygenation system of the shark’s gills (a hose with a continuously seawater flow inside its mouth) wasn’t used. Currently all sharks tagged are oxygenated throughout the tagging process or they are tagged and measured while immersed in the sea.
Tags are placed / inserted at the base of the dorsal fin
All tags were kindly donated by the NMFS / NOAA’s Apex Predator Program.
Together, with a catch-and-release operator - CAPE CRUISER – twenty seven blue sharks were already tagged and released during this project until now. Eleven of them were female and sixteen were males. The WLS crew managed to tag seven of these blue sharks.
…And, finally, freedom!
This tagged shark was in a good physical condition when released. It swam slowly away from the boat.
All moments are recorded by photos and/or video, so that who did not had the opportunity to come, can join us on social networks and stay tuned with the project.
Coming soon…The Portuguese Shark Week and the launch of the educational activities!