Sharks and other marine mammals in
The annual bloom of plant and animal plankton, as reported in articles in the Banner last month, provides food for many species including small fish which in turn provide food for larger fish and many seabirds around our coast.
Mass plankton blooms, like the one reported around Arran in June this year, give hope that the increase in food abundance will herald the arrival of some of Scotland’s most iconic marine species: marine mammals and sharks.
There are more than 30 species of sharks, skates and rays – fish species known as elasmobranchs that have a skeleton made out of cartilage instead of bone – recorded in Scottish waters. Around Arran, snorkellers and divers often happen across small-spotted catshark, also known as dogfish, and in 2017 the first cuckoo ray was spotted in the South Arran Marine Protected Area (MPA) in 30 years.
Arguably the most noteworthy shark in our seas is the basking shark – the biggest fish in UK waters and second largest in the world – which can grow more than 10m (33 feet) long and weigh up to several tonnes. Unlike most other sharks, these gentle giants feed entirely on plankton, one of only three shark species worldwide to do so. Basking sharks used to be common visitors to the Firth of Clyde, but their oil-rich livers led to them being hunted here and elsewhere in Scottish waters, with an active fishery in the Clyde until as recently as the 1990s when laws were introduced to protect them.
Today, basking sharks are seasonal visitors to Arran and are most commonly seen in August and September, with numbers varying from year to year. A distinctive ‘classic’ triangular shark fin is the most visible sign to look out for, along with the tip of the tail fin that can often also be seen. Elsewhere in Arran’s seas, you may get lucky and see an array of marine mammals, with seals the easiest to observe. Around the island we have a number of sites where these delightful animals haul out on to rocks to rest, moult and breed. Scotland supports internationally important populations of grey and harbour – also known as common – seals, with Arran’s coastlines and seas supporting healthy ‘bobs’, or herds, of both. Although the grey seal is more abundant in Scotland, locally you’re most likely to see the harbour seal.
At first glance, both species look similar, however, the harbour seal has more of a puppy dog face, while the grey has a longer head and Roman nose. Both species are long lived – approximately 30 years – and feed on a variety of marine species including fish, squid,