What is a shark anyway? Shark Trust MD Paul Cox takes time to consider a new study questioning the evolutionary lineage of certain species
UK cod off the menu
Copenhagen blockship unearthed
What is a shark anyway? Shark Trust MD Paul Cox takes time to consider a new study questioning the evolutionary lineage of certain species
UK cod off the menu
The Marine Conservation Society( MCS) has downgraded cod caught in UK waters to the worst rating for sustainability. Consumers have been advised to‘ completely avoid’ the fish and chip shop favourite and opt for European hake instead. Icelandic cod and haddock are other more sustainable alternatives recommended by the MCS. The advice is set out in the charity’ s Good Fish Guide, which helps seafood fans make sustainable choices. The MCS fears cod populations have dropped so low that commercial fishing would take the population below the level necessary for reproduction.
Dannebroge explodes during the Battle of Copenhagen on 2 April 1801. Painting: Gustav Boberg, 1801
Copenhagen blockship unearthed
Maritime archaeologists have discovered the remains of the blockship Dannebroge, which exploded during the Battle of Copenhagen in 1801. The battle was fought between the Danish-Norwegian fleet and the British Royal Navy under the command of Admiral Sir Horatio Nelson. The archaeological team was working at a depth of 15m in close to zero visibility. Their investigation forms part of work required prior to construction of the artificial island of Lynetteholm.
PHOTO: SIMON ROGERSON
Last month, a new video dropped onto the Shark Trust YouTube channel. Called‘ What is a Shark’ it’ s a kind of beginners’ guide to differentiating a shark from those‘ other’ fish. Within days, one of our most dedicated viewers commented that( sic)“ I think it’ s wrong to call sharks fish … apart from their vertebrae they don’ t have anything in common”. It’ s not the first time I’ ve heard it. And sometimes this logic suggests that sharks are somehow‘ different’ and therefore should be treated differently. But is it right and does it really matter anyway? I guess, to start with, we must ask ourselves what is a fish anyway? It seems that pretty much any characteristic of a fish that you come up with will not apply somewhere down the line. Helpfully a quick Google search throws up about 10 different definitions, but this one stands out: A fish is an aquatic, gillbearing, craniate vertebrate that typically lacks limbs with digits and lives in either freshwater or saltwater. Well, that’ s broad enough to include sharks. Case closed.
But are sharks all one group? Of course they are. Or are they? Well, according to some new genetic research – reported in the Smithsonian Magazine – the shark family tree may be“ more complicated than previously thought”.
The analysis, which is yet to be verified by peer review, appears to challenge the long-held view that sharks are one closely related group, somewhat separate from skates and rays, Instead, this spanner in the works suggests that
A sixgill shark, part of the
Hexanchiforme group... do they really have more genetically in common with skates? some shark species belong to a distinct line separate from all other sharks, skates and rays. Meaning, perhaps, that skates and rays are more closely related to sharks than some sharks are. Making sense? The group in question – the outliers – are the Hexanchiformes, which includes the frilled sharks and cow sharks. Perhaps there is a clue in the six or seven gill slits exhibited by cow sharks, rather than the normal five. Who knows? While we have to be cautious about interpretation of genetic data on animals with 400 + million year history, it’ s always good to know that science can get things wrong. But, back to my earlier point, does any of this matter?
The researcher in question, quoted in the Smithsonian, says of the importance of this research“ Sharks hold more evolutionary history than any other vertebrate lineage … we need a good tree to understand what we stand to lose”. Sounds a little like counting deckchairs on the Titanic to me!
But he’ s right, in some regards. It is important for us to understand the links between species and their evolutionary history. It is important for us to have agreed groupings for animals, But it’ s also important to look at the here and now. Whatever you call them or however you subdivide them, sharks swim with fish and get caught with fish. So maybe, if we don’ t want to lose them, we should worry about what we do with them rather than what box we put them in.
If it walks like a duck and quacks like a duck … www. sharktrust. org
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