In the summer of 2015, Whitby Whale Watching reported a truly bumper year with sightings on 60 consecutive trips, and a previously unheard of six species of cetacean in one four-hour period. “No other operator in the UK has ever had that,” says Jill Smith. The reliability of sightings was put to the test recently when a TV crew arrived to film Coast to Coast with Tony Robinson. “Within 15 minutes of leaving harbour, the minkes were there, and they performed as though to order, it was amazing,” adds Smith.
So are the so-called great whales becoming more common, or are we just getting better at spotting them? It’s a complicated picture. Take humpbacks, which have been spotted off Yorkshire for the last six years. There are two main humpback breeding areas in the Atlantic – one in the west centred on the Caribbean, and another much smaller one in the east, around the Azores. It’s possible that the eastern population was always smaller, but whaling on this side of the Atlantic was also much more intense and went on for a longer period than in the western Atlantic, with the result that this species and other large whales haven’t been common in British waters in living memory.
But the eastern Atlantic humpback population has been recovering well over recent decades, and the obvious assumption was that the increase in sightings around Britain involved members of that population. Interestingly, however, the evidence suggests otherwise.
Dr Peter Evans, of the Sea Watch Foundation, has been studying marine mammal records for 30 years. “Our photo-ID records show that some of the western Atlantic breeding population cross over to Iceland and Norway and we thought we might be getting some of those animals, especially as there are more humpback records around the north of Britain than the south,” he says.
A thrilling breakthrough for that theory came last December, when naturalists Brydon Thomason and Richard Shucksmith took a spectacular series of photographs of humpbacks visiting Shetland, including the first underwater video footage shot in British waters. But the real scoop came when the images of the uniquely marked tail flukes of one individual were matched with pictures taken nine months earlier, off the Caribbean island of Guadeloupe.
Both the whales photographed by Thomason and Shucksmith appeared to be adults. So what were they doing on the far side of the ocean from their supposed breeding grounds, during what for them is the breeding season?
“Possibly they weren’t quite fully mature,” says Evans. “Or they’re non breeding adults – humpbacks don’t breed every year.” Might they breed here one day? “It’s not impossible,” he adds. “But we’ve never seen calves so at the moment we can’t say that that’s happening.”
Photo ID evidence may explain where some of the whales are coming from. The next obvious question is why? Whitby Whale Watching skipper Bryan Clarkson is in no doubt – as an ex-fisherman he has seen North Sea stocks of important prey fish rising and knows great whales have great appetites. Evans agrees: “Humpback and fin whales only come in when there is a lot of food. We know numbers of herring and mackerel are increasing after over-exploitation in the 1960s, and sprats are also doing well.”
This all sounds very positive, certainly for people hoping for a whale encounter close to home, but Dr Evans sounds a note of caution. “We can’t assume it’s all good news. While the increase in sightings of humpbacks appears to reflect a genuine increase in abundance, it’s too soon to say the same of some other species, like fin and sperm whales. In fact, it could be that the change we’re seeing in their distribution is due to climate change.”
Fin and sperm whales usually live in deep water off the edge of the continental shelf, where they are much less easy to monitor, so Evans and his colleagues at the Sea Watch Foundation don’t see strong evidence that they are increasing in the way humpbacks seem to be. Recovering stocks of important prey are likely to be drawing these species into the North Sea, but the jury is still out on whether this changing pattern is a good thing. “The changes we’re seeing might also reflect the fact that these areas are getting warmer and more productive year round, but at the same time we know the biomass of tiny plankton dwelling copepod crustaceans is declining, which is potentially very bad news for fin whales, and more extreme weather conditions will work against lots of species,” says Evans.
So it could be that some of the whales visiting the North Sea are doing so driven by hunger. Certainly the large numbers of sperm whales that stranded around North Sea coasts in 2016 were thin and vulnerable – at least five died on or close to British beaches. Stormy weather and military sonar may also have played a part in their fate. What’s clear is that monitoring is essential. Every whale sighting provides valuable data that may contribute to greater understanding of these mysterious and undeniably great lives.
The Sea Watch Foundation is celebrating its 25th year in 2017 with an extended version of its annual National Whale and Dolphin Watch from July 29 to August 6. To record any sea mammal sighting or investigate whale watching opportunities further afield, visit seawatchfoundation.org.uk.
To book an excursion with Whitby Whale Watching go to whitbywhalewatching.net. Trips operate from July 22 to late October, with peak season for sightings in August and September.