Another ' what is it' moment but honestly don't click and enlarge.
It's the vertebrae of a basking shark. They've been overfished thanks to their highly valued fins and are now on the Convention on International Trade in Endangered Species. They don't reproduce quickly, having low fertility, are slow growing, long lived but slow to mature.
This is what a basking shark does best. Lazes at the surface of the sea with mouth (what a north and south it is) open, filter feeding on zooplankton. In one hour they can filter enough water to fill an Olympic-size swimmig pool.
They are the second largest fish behind whale sharks but not much is known about their habits. Pregnant females and and young have never been spotted and they disappear for half the year. Scientists have tagged them but since they live for 50 years or more and the tags fall off after a year, it's hard to follow their migration patterns.
Which is where this section of vertebrae comes in. Like tree rings, the vertebrae consists of distinct layers of tissue laid down sequentially over an individual's life time in an alternating light/dark banding pattern. Using vertebrae from sharks that have stranded on beaches, scientists are looking for a radioactive isotope from nuclear bomb blasts set off in the l950s. the residue which fell all over us and the ocean. Different areas of the ocean have different ratios of stable carbon and nitrogen isotopes so when overlain on a map of the ocean, they create distinct isotope patches and when the whales eat the plankton in these patches it shows up in the layers and in time will enable scientists to map their migration pathways.
Knowing where and when they go will help form a plan of conservation that will also help whale sharks and great whites thanks to the research of Li Ling Hamady.
As you can see in this map, colour variations represent different ratios of nitrogen isotopes in the ocean.