Why do we tag sea turtles?

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2021-02-09 Carapace measurements

Throughout the season, we regularly conduct tagging events at the Harbour of Argostoli. These events involve us taking turtles out of the water to record a number of different measurements. One of the measurements we record is the curved carapace (top/dorsal part of the shell) length (CCL), which allows us to deduce the approximate age of a turtle. Another measurement involves the length of the tail, one of the very few sexually dimorphic features of a turtle. The length of the tail can only be used once the turtle has hit maturity around 15 to 25 years, it will extend beyond the carapace in males compared to the females where it typically will not.

2021-02-09 metal tag placement

During tagging events, we not only take measurements but most importantly apply small metal tags onto two flippers that give each turtle a unique identification. The front of the tag is an exclusive number per turtle and on the back, contact information can be found for the organisation that applied the tag. This enables other organisations to contact the original organisation if a tag or turtle is found, an example; if a turtle that we tagged in Kefalonia appears in another location the person who found the turtle/tag can contact Wildlife Sense. Alongside the external metal tags, a microchip is also inserted, much like the one a dog or a cat would receive. We do this because external tags are subject to wear and tear, whereas, microchips are inserted internally into muscle mass and will, more often than not, be there for the remainder of the turtle's life.

If a turtle has been submitted to the above-mentioned process it is classified as a tagged turtle. If a tagged turtle is taken out a subsequent year for a necessary reason, they are remeasured. This data can help create a better understanding of the growth rates and other life-history traits of the turtles found around Kefalonia. It has been understood by various studies that growth rates and life-history traits vary between feeding grounds, therefore, it is important to establish rates that apply to our location.

2021-02-09 Release on tagging event

Lastly and very importantly, we assess the condition of every turtle we take out of the water. We ensure the absence of fishing lines and hooks around the flipper and neck regions. Furthermore, we look for any signs of boat and propeller strikes as well as any indications that the turtle may be unwell such as an unusually high barnacle, leech, and algae load in combination with very slow movement.

In conclusion, these tagging events are a fundamental part of the research we perform. They give us an insight into the ecology and movement pattern of the turtles that visit the harbour every summer!

Written by Josh Witzmann

Tags: research, threats, Argostoli, conservation, fishing hook, fishing line, sea turtle, injured, rescue, Tagging


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