Cleveland Diving Club While winter underwater sea diving may be limited, for some, a keen interest in marine creatures cannot be, in all honesty, quelled when one lives so close to the sea. Catching sight of marine mammals such as seals and dolphins is very exciting and spotting nomadic pods of dolphins skimming the waves is truly spell binding (Photo 1). It’s hard to imagine that millions of years ago dolphins were once terrestrial creatures who have since evolved back to the sea. For dolphin spotters a little knowledge can greatly enhance their quest when seeking to spot them again. For example, during spring and summer dolphins hunt migrating salmon on a rising tide (flood tide) therefore, knowing moon phases and tide predictions are a distinct advantage. The Common Dolphin (photo 2) is the more frequent visitor to the North Sea along with Bottle Dolphins. Being inquisitive, sociable and fun-loving dolphins love interacting with boats, swimming, leaping and showing off their water aerobics antics as they travel along with it (photo 3). This is great for divers using a rib to get to a dive site which is when some of these photos were taken. Renowned for their intelligence and whistling communications dolphins have a diverse language to the point each dolphin has its own whistle signature i.e. name. As a species, dolphins are masters of how marine mammals live successfully in the sea. For example, they can reach speeds of up to 30 km per hour and dive to 1000 ft (304.8m) before coming up for air. In addition, having a separate breathing and food passage stops them from drowning as they hunt and eat on the go, with one of their two stomachs, storing food while the other one digests it. Another tale of two halves is how dolphins sleep as, unlike seals, they never leave the water. Being ‘conscience breathers,’ dolphins need to think about breathing as they would drown if they fell asleep completely. So, by alternating shutting down one half of the brain and closing the opposite eye while sleeping, the side of the brain not shut down can monitor the environment and control its breathing. Unsurprisingly, as intelligent creatures, dolphins have a sophisticated and compassionate social structure within the pod which not only includes tending to the ill or older dolphins but also have a dolphin ‘midwife,’ who supports the live birth of a dolphin calf to ensures the calf gets to the surface for that all important first breath. Unfortunately, not all events can be covered and when this little chap became disoriented and exhausted off Redcar beach recently, humans were on hand to protect him while he rested before helping him on his way (photo 4). Depending on the species wild dolphins can live up to 90 plus years but this is halved when they are kept in captivity with smaller dolphins living as little as 25 years. Regrettably there are about 2913 captive dolphins around the world. Most dolphin species have yet to be considered endangered, but it is sad news for the New Zealand ‘Maui’ dolphins who are on the brink of extinction, a primary cause being discarded fishing gear (ghost gear.) Thankfully the actions of our regional ‘ghost gear’ hunters are helping to keep our waters safer for our visiting dolphins. Cleveland Divers can be contacted via their ’Facebook’ page ‘The Diving Club-Cleveland’ or on 07960 608529.
June 19