SHARKS

SHARKS - SHOULD WE EAT THEM?

In January there was a bargain on the fish counter at Carrefour in Santa Pola, tintorera.  It had been previously frozen and hence the very cheap price.  I was aware that it was from the Shark family but it had a certificate of provenance from the Department of Agriculture, so I assumed it was OK.

Perhaps I should have read my posting from 4 years ago and erred on the side of caution.
Stocks in and around Europe have increased following catch limitations set by the EU (and the catch in Spain is legal) but all species of shark appear to be at risk or vulnerable so should we be eating them?

In his book on Mediterranean Seafood, Alan Davidson lists the 7 best varieties for eating as:

Porbeagle (Spanish caillon) Hammerhead, Nurse-hound dogfish, lesser spotted dogfish (rough hound), smooth hound, spur dog & angel shark but he does say that the tope (Spanish cazon) and  blue shark (Spanish tintorera) are also good

In his book on the Seafood of Spain and Portugal, Davidson mentions other species including the Mako (marrajo), Thresher shark (Zorro) and several varieties of dogfish but singles out the tope as being one of the best for eating and also rates Porbeagle among the highest followed by Mako and then blue shark.

All of the species mentioned are found regularly in British waters (except the hammerhead which may be an occasional visitor) as well as in the Atlantic and parts of the Mediterranean.

Apart from the issue of sustainability some people appear to have an aversion to eating shark "because they eat people" but generally sharks found in European waters pose no threat to humans and are not aggressive. They usually inhabit deep waters and rarely come close to the shore. I have read that there have been only a dozen recorded incidents involving people and blue sharks in the last 500 years!

On the other hand, the white shark is dangerous but is not usually found around Europe and you are unlikely to find it on the fishmonger's counter.  You won't find basking sharks either. Basking sharks, the gentle giants of the sea, and the second largest fish, are common visitors to the UK but are a protected species throughout the EU.

There is a cap on blue shark catch in the North Atlantic as part of an international agreement but similar rules do not apply in the south Atlantic. For the present, fish caught and landed in the North Atlantic should be OK but the situation will need to be closely monitored.  The biggest threat to the blue shark comes from the market for shark fins for soup in China and other parts of southeast Asia and the practice of catching them for the fins only and the bodies being tossed back into the sea.

In the UK, blue sharks appear to be caught mainly for "sport"  and then returned alive to the sea. The largest on record, caught off the coast of Cornwall, near Penzance in 2017, was 9 feet long and weighed 256lb beating the previous 58-year record of 214lbs.

British record blue shark

Another reason given for not eating members of the shark family is the smell and a belief that they urinate through their skin.  In my teens I regularly dissected dogfish as part of the A-Level Zoology syllabus, and can confirm that they do have a conventional urinary system. They have kidneys and a urinary duct just like any other vertebrate and excrete quite a lot of waste products in their urine in the normal way.

So what is the myth about them urinating through their skin?  All fish have a problem that their blood and body fluids are less salty than the sea and therefore they lose water through osmosis. Bony fishes overcome this by constant drinking of water and passing it over their gills to get rid of excessive salt and they excrete nitrogenous waste in the form of ammonia, which is a very toxic compound.

The cartilaginous (non-bony) fish such as sharks, on the other hand, convert ammonia to less toxic urea which is stored in the blood and prevents the loss of water through osmosis.  Unlike bony fishes they do not have to constantly drink water and they excrete nitrogenous wastes as urea, which is less harmful to the environment than ammonia.  In a live shark, ammonia doesn't accumulate because it is quickly converted to urea. When the shark dies, however, the urea breaks down forming ammonia, which is why fresh shark meat and other cartilaginous fish, such as skate (rays) may smell of ammonia. Sharks which are bled when caught and cut into steaks are less likely to have this smell when they reach the fishmonger.  The cartilaginous fish eaten mostly in the UK are dogfish (usually marketed as Huss, Rock Salmon or Flake) and skate.

Some cookery books suggest eating skate when it is one or two days old when the ammoniacal smell will have disappeared or soaking the flesh in water or lemon juice before cooking.  Others say this is unnecessary as the smell indicates that the urea has been converted to ammonia and that in any smell, and the ammonia itself, will disappear in cooking.  So long as stocks remain sustainable, I for one will continue eating skate but will check the species and source.

And of course, the one big advantage of eating cartilaginous fish - and a great plus with children (and me) is they have no bones!

John Austin

Santa Pola, April 2018