Basking Shark Breach
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A breaching shark caught on camera![/caption]
The Basking Shark, do you see them as a gentle giant swimming gently along or aerial acrobat breaching clean out of the water, did you know these huge basking shark breach??? In fact the are the biggest shark (and fish) in the whole world to do so!
It's mind boggling when you think about the energy involved in such an activity. For a shark that can weigh numerous tonnes and one that consumes plankton as their sole meal, how can they afford to use such a vast amount of energy to propel their huge bodies out of the water?
There are two theories on why the sharks breach out of the water;
1) To rid themselves of Parasites!
The Sea Lamprey (Petromyzon marinus) attach themselves to the sharks usually on the underside of the shark but sometimes around their bodies too. Their positions sometime co-incides with the location of the 'boy bits' making it a little difficult to tell if the shark is a boy or a girl! The lampreys have a mouth full of hooked teeth and attach themselves to the shark, feeding off them (as parasites do). If you imagine how streamlined the design of a shark is, these lampreys must cause all sorts of turbulence for swimming and hence extra energy required, not good extra work for just eating meals of plankton! Perhaps it may cause irritation to shark (however given the size of their brain and records from the historic shark hunters, we're not sure whether they would 'feel' them). However if they do 'feel' them, how far do you go to scratch an itch!?
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Parasitic Lamprey of a Basking Shark[/caption]
2) Courtship Behaviour
Around our waters it has been said there is a lot of courtship behaviour with the sharks. It has been suggested that sharks perform courtship where they closely follow each other. With our waters also having a mass aggregation of shark later in the season (remember the survey of 918 sharks....), the current thinking is this is could be to do with our late summer plankton bloom or, as seen in many other areas of nature, a large population all heading to one place to try and expand the gene pool! It's around this time we see most of the breaching so 2+2=...?
Our own feeling on it is that that the argument must be balanced.
Ok the parasites might be annoying but is it would expending all that energy? It's a little anthropomorphic to suggest they get annoyed and getting rid of parasites will be purely for biological gain e.g. better streamlining and therefore less energy required for swimming or reducing output via the parasite. So then is the energy saved from the extra drag, worth the acute burst of energy by leaping out of the water? The sharks do swim 1000's of kilometres, so long term vs short term?
The other argument is clear to make comparisons to other parts of nature where elaborate or intensive displays are made to attract a mate (e.g. frigate birds appendage, elephant seals fighting, pub on a Sat night?). You could say this is mostly males in other parts of nature, however we're never usually quick enough to tell on the shark. But is there an argument for the huge amount of energy expended to be a mating activity? E.g the bigger the splash, the stronger the shark, the better the genes?
It will be interesting to try and get more of an understanding of this, maybe this season! If you have any thoughts, answers on a postcard!
See a picture from one of our clients out last August (2103), great skills to capture the shark (nearly) in full flight. Awesome work Ray!
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Breaching Basking Shark caught by Ray Mahoney[/caption]