Tuesday 8 July 2008

We've been trying to get the database up to date, but it's a running battle as we're collecting data all the time. But currently - and this is a rough and unfiltered count, we've identified 58 Heaviside's dolphins and 46 bottlenose dolphins. This doesn't mean that's how many there are - far from it, it's simply the number we've been able to photograph and identify.

The big difference between the two species is that we keep seeing more or less the same bottlenose dolphins and have identified very few new animals since mid-June. Whereas, the Heaviside's dolphin catalogue continues to grow. They're much harder to photograph and not nearly as well marked.

I've put up pictures below of our two "star performers": T-029 a bottlenose that we've see a grand total of 8 out of the 13 days that we've seen bottlenose so far and C-022, a very boat friendly and photogenic Heaviside's dolphin that we've now seen on 6 different days!
Unfortunately, C-022's distinctive scarring pattern is already starting to fade so we can only use these scars for a short period. The deeper notches found in the trailing edge of some dolphins are much more stable and can be used over several years to identify animals.
The difference in how "boat friendly" individual dolphins are is a problem for the mark-recapture analysis we're trying to do as, unless we can account for it, we will be severely biasing the resulting abundance estimate (downwards) because we are oversampling some members of the population and undersampling others which are less boat friendly. The best way around this is try to 'capture' the entire population. So...we're back out tomorrow.

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