Tissue or biopsy sampling
Whale sharks are a highly mobile pelagic species that exhibit complex movement patterns seemingly influenced by life-stage, reproduction and feeding. To better understand these movements we use tissue sampling.
To collect the samples, we usually use a modified Hawaiian sling (an elasticated pole), which allows us to take a small (~6mm diameter) sample of skin from the shark. We take these biopsies from the area immediately under the dorsal fin on the left side of the shark to ensure that we are taking it from the thickest part of the skin.
Once the samples have been sequenced, we can answer questions about genetic distances between individuals and sub-populations, to analyse the partitioning of genetic diversity to infer connectivity, and even characterise the relatedness between individuals in terms of siblings, parents and tertiary relations. The results will give us greater insights into how the species has been and is now connected on temporal and spatial scales, will allow us to assess genetic health of sub- and meta-populations, and to understand their habitat use throughout their life-stages.
The collaboration of various regional organisations, together with the variety of genetic markers and software, will allow this study to develop in both fine- (i.e. national) and large- (i.e. international) scales, resulting in comprehensive characterisation of the species both across and within oceans. This information will be used to formulate more effective conservation management plans and to guide resource management for this endangered species.
Blood chemical analysis can be used in a number of ways to study baseline health in many marine species.
Blood draw from whale sharks had only been successfully carried out in captivity until 2017.
The blood is taken from the base of the primary dorsal fin using a two-way stopcock system to avoid seawater contamination.
First the blood vessel must be located then a primary syringe filled before opening the secondary syringe. The sample must be adequately stored and centrifuged for prolonged storage if access to a laboratory is not immediate.
Blood hormonal levels can indicate reproductive status and confirm pregnancy.
This technique has been used very successfully with juvenile whale sharks in many study areas.
Measurement is done by using a digital camera with a non-distorting lens in combination with two lasers.
The lasers are set at a known distance apart, (25cm for the GWSP) and by extrapolation of the pixels, the overall length obtained.
With recapture using the same technique and measurement, growth rates can be calculated.
At present the margin of error would appear to be greater with adults for which reason for future fieldwork stereoscopic image capture will be implemented.
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