Shark Chronicles 023 – Stable Isotope Sampling

Shark Chronicles 023 – Stable Isotope Sampling

Posted by Amy Blessington on August 14, 2008

On Monday 11th August, a SAMPLA team including Ryan, Ed, Christine, Nico and Amy anchored by Seal Island to do some chumming.

A white shark is sample for stable isotope analysis
We were lucky enough to see more sharks than we had done for a while and they had decided to be bold and playful. Amy took the bait rope and was able to lure the sharks close to the boat so that they were in reach of Ryan and the genetic pole. A quick ‘pop’ and he removed a small plug of flesh with the screw-like tip. Quite often the sharks don’t appreciate being jabbed with the pole and swim off never to be seen again but the individuals we had didn’t seem too bothered and kept coming back to the bait. One was very heavily scarred and a large wound running down from its dorsal fin showed it was a tough shark. Usually, it is a good day for SAMPLA if we manage to get one biopsy sample but Ryan was on fire as were the sharks so in total we obtained three stable isotope samples and two genetic samples, all in one morning! Once the stable isotope samples are taken they are carefully removed from the tip of the pole with tweezers and frozen to preserve the cells and prevent further biological reactions that may alter the isotope composition. Genetic samples are preserved in alcohol.

This data collection by SAMPLA is in association with Keshnee Pillay, a doctoral student at Marine Coastal Management. Stable isotope analysis of the sharks’ flesh can tell us about the isotope ratios of carbon, nitrogen and oxygen present. These enter the sharks’ tissues from the food it has eaten and so inferences can be made into the food chain and energy flow through the ecosystem, along with samples ranging from plants and invertebrates to seals and fish. SAMPLA is always eager to collaborate with other scientists, institutions and the government to broaden our research into the great white shark, plus we get to have all the fun working with the sharks themselves!

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