THERE are few creatures in our natural environment that instil in us such a feeling of wonder and awe than that of the large marine mammals – the great whales – members of that order of mammals known as cetaceans.
Most encounters with these leviathans of the deep ocean occur when, either through illness or accident, they wash up dead or dying on the shores of Ireland only to become a foul smelling amorphous mass providing rich pickings for the birds and beasties that make our intertidal zone home.
Some parts of the world provide such rich feeding potential for these huge animals that they come so close inshore that they may be seen from land based lookouts or by those hardy souls who venture out in boats to get fleeting glimpses of these huge mammals as they surface to breath. For all their superficial fish like appearance they are of course air breathing and they bear live young, like man.
Ireland is one such place where sightings of these unique and enigmatic creatures may be made; most frequently off the south coast.
The largest of these winter visitors to Ireland is the mighty fin whale. The second largest mammal on earth, the fin whale (Balaenoptera physalus) is most frequently seen in Irish inshore waters during the autumn and winter months in search of the herring shoals on which they feed.
More certain species identification requires a close view of the bottom right hand jaw which is white in colour; a job not for the faint hearted as an adult fin whale may reach lengths of 70′ or more; over twice the length of the average small fishing vessel and weigh in excess of 65 tonnes.
Numbers vary each year but the south coast of Ireland is one of the few locations in the world where fin whales can be seen with a land backdrop as they have been encountered as close as a few hundred meters off the rocky shoreline of Sherkin Island in West Cork.
The North Atlantic population of fin whales is known to feed on both krill (small shrimp like crustaceans) and shoaling fish.
It appears to be the abundant stocks of herring that accumulate off the south coast of Ireland during the autumn and winter that attract these animals from their deep ocean, pelagic existence into inshore waters.
Being an apex predator, feeding at the top of the food pyramid, the presence of these animals, capable of consuming herring quantities over an hour, measured in tonnes, are a direct indicator of how herring stocks have recovered from overfishing during the last 10 years and may be an indication of the condition of marine ecosystems off the south coast of Ireland as a whole.
Over exploitation of fish stocks in general, coastal development and pollution are the main issues that will need to be taken into consideration when developing a conservation strategy for this species when they visit the Irish coast.
Little is known of the movement patterns of this large cetacean species in the northern hemisphere but the north Atlantic population is considered to number in the region of 40,000 animals.
Whaling activities were responsible for the serious decline in their numbers globally during the 20th century, but a moratorium on commercial whaling put in place in the mid 1980’s saw an increase in their numbers both north and south of the equator.
Inclusion of this species in the current commercial whaling campaigns of Iceland and Japan, in flagrant disregard for the moratorium, may jeopardise the precarious conservation status of this iconic, still endangered marine mammal.
Nic Slocum is a zoologist and operator of Whale Watch West Cork www.whalewatchwestcork.com.