An ode to the harbour porpoise

Categories // Bay of Biscay Wildlife Officer

An ode to the harbour porpoise

Calm crossings through the Bay of Biscay treated not only the passengers but the wildlife officers onboard the Cap Finistère .

Hello there! I’m back from another two-weeks on board the Cap Finistère, and once again, I’ve had a cracking time. The bad weather from last week seemed to just disappear overnight, and myself and Heather were treated to some beautifully flat crossings across the Bay of Biscay. We were fortunate enough to spot my first official basking sharks, breaching sunfish, two species of dolphin (common and striped), and several close encounters with fin whales; all of which delighted our eager passengers.

However, instead of telling you more about fin whales, I wanted to dedicate this blog to one of my favourite species of cetaceans…..the harbour porpoise! I do get a few raised eyebrows when I make that statement, as surely the humble harbour porpoise can’t compete with those glamourous orcas, the jaw dropping blue whales, or the elusive beaked whales? But to me, they are just marvellous!

Despite being the smallest cetacean in Europe (maximum 1.4-2 metres), the harbour porpoise is actually one of the most abundant and commonly sighted of all the whale, dolphin and porpoise species in our waters. They are known to prefer shallower waters and are most frequently sighted closer to shore although offshore populations have been recorded. Here on the Cap Finistère we tend to encounter these delightful species in the English Channel and the Northern Bay of Biscay, especially in between the islands off the coast of Brittany and Brest.

As odontocetes (toothed whales), porpoises are frequently mistaken for their larger dolphin cousins. However, here at ORCA we employ a few “tricks of the trade” to help us tell the two apart when we are on deck watch:

1. We take a look at the animals’ size. Harbour porpoises, with a maximum size of 2 metres, are smaller than dolphins. However, judging size can be difficult from a distance.

2. Next, we examine the dorsal fins. Whilst dolphin dorsal fins are tall and curved, the harbour porpoises have a far smaller, equilateral triangle shaped fin

3. Finally, we take a few minutes to examine their behaviour. Whilst dolphins are renowned for their spontaneous acrobatic displays as they jump through the water and attempt to bow-ride, the harbour porpoise is far more reserved and very rarely leap or breach. In fact, you’re more likely to see them perform delicate little rolls through the water.

Even after considering all these differences, it can actually be quite difficult to spot harbour porpoises at sea, as their small size and relatively low surface profile makes it hard to see them in anything but “perfect” sea conditions. I generally consider myself quite lucky when I catch a glimpse of one!

Sadly, these animals do face several threats. Due to their preference for shallower waters, harbour porpoises are especially vulnerable to chemical pollution, noise pollution, and depletion of prey through over fishing. Furthermore, the porpoises themselves are also frequently caught as incidental bycatch.

I think that pretty much sums up my very brief introduction to my beloved harbour porpoises; and you never know, next time you’re looking out to sea you might catch sight of a little triangular dorsal fin, gently moving through the water.

In any case, I wish Heather and Sam the best of luck with their cetacean spotting this week and look forward to catching up with them.


Wildlife Officer - Bay of Biscay - Cap Finistère

Photo credit: Laura Bartlett