Thursday, 22 April 2010

Marloes Peninsula: Porpoises and a Basking Shark

The Northerly winds over the weekend and at the start of the week, while cold, gave a very flat calm sea, and so an unusually good opportunity to look for porpoises. As well as the regular group of 3+ in the northerly tidal flow out of Jack Sound, we found groups of 2+ porpoises in the South, which is unusual, including a couple between St Ann's Head and Skokholm, and another small group between Gateholm and Skomer. While Porpoises clearly can move around a lot, I was very heartened to see so many (and so frequently) on the South side of the peninsula.

Slightly off-cetacean topic, but an incredible marine surprise, was a massive Basking Shark off Marloes Sands on Saturday 17th April. It cruised nearly the whole length of the beach at just after low tide, and at times was as little as 50 yards off the shore. It then swam out to Gateholm, and was last seen, nearly an hour later, heading towards Skokholm. It was surprisingly dynamic, often turning in tight circles, then rising nearly out of the water, before sinking down a couple of feet or so again. How big was it? I tried to estimate its size based upon its dorsal fin. Given the number of feeding Razorbills that it swam close to, I used these as my unit of reference, and that gives an estimate of a fin height and length at the base of between 2 and 2.5 feet ("two and a half Razorbills"). Based on the distance between the dorsal fin and the (much smaller, but frequently visible) tail fin, and the similar distance to the nose (when visible), this gave a length for the whole shark of between 12 and 15 feet.

We looked for it again that evening and the next day, but to no avail.