Whither goest the biggest fish?

7 02 2013
© W Osborn (AIMS)

© W Osborn (AIMS)

Well, since my own institute beat me to the punch on announcing our latest whale shark paper (really, far too keen, ladies & gents), I thought I’d better follow up with a post of my own.

We’ve mentioned our previous whale shark research before (see here and here for previous posts, and see the end of this post for a full list of our whale shark publications), but this is a lovely extension of that work by my recently completed PhD student, Ana Sequeira.

Her latest contribution, Inferred global connectivity of whale shark Rhincodon typus populations just published online in Journal of Fish Biology, describes what a lot of whale shark punters & researchers alike have suspected for a long time – global connectivity of all the oceans’ whale shark populations. The problem hasn’t been a lack of ‘evidence’ for this per se; there is now sufficient evidence from genetic studies that at least on the generational scale (a single generation could be up to 37 years long), populations among the major ocean basins are connected via migration (Castro et al. 2007Schmidt et al. 2009). The problem instead is that no one has ever observed a shark voyage between ocean basins, nor has anyone really suggested how and over what time scales this (must) happen.

Until now, that is. Read the rest of this entry »

Big sharks. Big mystery.

9 03 2011

My PhD student, Ana Sequeira, has just written a great little guest blog post for the Environment Institute‘s blog. Given I’m en route to Tasmania for a quick consultancy meeting, I thought I’d let myself off the hook and reproduce the post here. Well done, Ana (and hint to my other students – your time on ConservationBytes.com is coming…).

This week is Seaweek and guest blogger Ana Sequeira describes how whale shark distribution might be shifting according to seasonal environmental predictors.

Ana Sequeira is a PhD student at the University of Adelaide (Global Ecology Group). Her main research interests are to develop models applied to the marine environment to describe key environmental processes, species distribution patterns and ecological interactions.

The main objective of her PhD thesis is to investigate behavioural ecology of whale sharks. She is now trying to understand which environmental variables may affect whale shark distribution.

The whale shark (Rhincodon typus, Smith 1828) is the largest fish in the ocean and can reach more than 12 m in total length. Although little is known about their habitat selection or migration patterns, the whale shark appears to be a highly mobile species. They predictably form near shore aggregations in some coastal locations (e.g. off Ningaloo reef in Western Australia) what makes them the subject of highly lucrative marine ecotourism industries. Also, artisanal and small-scale fisheries for the species still exist in many parts of the tropics.

Since the whale sharks is classified a Vulnerable species (IUCN Red List), understanding their migratory behaviour became of chief importance as they can be travelling from regions where they are protected to regions where they are still harvested. Read the rest of this entry »


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