The insatiable demand for bluefin tuna.doc - ALAN DEIDUN by jianghongl


									The insatiable demand for bluefin tunaMajestic Marine Giant in Peril

Tuna and its exploitation has been hogging the limelight for quite some time now. DR
ALAN DEIDUN gives an insight into the biology of the bluefin tuna and what’s stoking
the white-hot demand for its meat.

The term tuna is too vague a term, since together with the mackerels, tuna species make
up a 50 species-strong family of bony fish. The seven different species of tuna of
commercial interest include the bluefin tuna, albacore, skipjack (the stuff gracing your
salads), bonito, yellowfin and bigeye. To fully unravel the intricate net of terminology,
there are actually three different species of bluefin tuna – the one normally encountered
in Mediterranean waters is the Atlantic bluefin, whose range girdles the entire Atlantic
Ocean, from the coasts of North Carolina to the waters off north-western Africa and into
the Mediterranean.
This species is head and gills above other fish species for two major reasons: firstly,
contrary to most of the other approximately 20,000 fish species, it is warm-blooded,
maintaining a body temperature of 27oC, despite diving to depths of up to one kilometre,
where the ambient sea temperature can plummet to around fiveoCoC…
Secondly, the species is truly a juggernaut, attaining gargantuan dimensions close to three
quarters of a ton and a length of four metres – dimensions normally reserved for marine
mammals like whales. And, despite its prohibitive size, the bluefin tuna cleaves the water
at a breakneck speed of up to 55 mph, living for around 30 years.
Tuna is caught commercially by two main methods, purse seine and long lining. It has
become almost a cliché, but most bluefin is destined to satiate the ravenous Japanese
appetite for tuna – at the Tsukiji fish market in Tokyo, a single bluefin tuna sold for a
staggering $173,600. In fact, the species has scaled new heights, from being a fish that
samurai would not eat since they perceived it as being unclean to maguro, a delicacy that
can be as expensive as truffles or caviar…
Toro, the best quality maguro, comes from the fatty belly meat of the adult bluefin. The
crave for this meat, and raw tuna meat to make sushi and sashimi, has recently exploded
worldwide, with Mediterranean bluefin tuna being especially sought after for itstheir oil-
rich tissue. However, as most of this tuna is bred in pens off our shores, the fish are
closely monitored to ensure appealing colour and scrumptious taste.
The history of catching tuna dates back hundreds of years, and even people such as
Aristotle wrote about the bluefin before he died in 322 BC. Nowadays, the movements of
this species are tracked by means of pop-off satellite tags. Locally, bluefin tuna used to
approach our shores closely, and some coastal stretches are even named after the annual
occurrences: Dawret it-Tonn in Mellieha, where the old tunnery building has recently
been opened as a museum.
Made from netting and stretching like a wall vertically from seafloor to sea surface, a
Mediterranean tuna trap is called a tonnara or madrague. A net wall can stretch out from
the coast to over a mile offshore, steering migrating tuna towards an offshore netted
enclosure about 100 feet, or more, to the side and plunging down to the sandy bottom at
130 feet. Through a vertical opening, the tuna find their way into this netted enclosure,
but once inside and circling as a school, cannot find their way out to escape.
The Egadian Islands off the western coast of Sicily have been since the remotest of times
the hubs of the tunny fisheries. The world-renowned bloodbath known as la Mattanza is
suffused in deeply-rooted rituals. In fact, the men involved in the tuna haul are led by a
captain whose authority is undisputed… and he always has the final word over all aspects
of the kill. From his six-oared boat, he directs the congregation of fishermen telling them
when there are enough tuna in the death chamber to start the kill properly.
When heaving the net up to the boats, the fishermen harpoon the surfacing fish turning
the sea into a crimson blanket. A plaque at Favignana records the annual quantities of
tuna caught – the 1848 kill of 4,353 fish has etched an indelible mark in the islands’
The timing of la Mattanza is finely-tuned with the fish’s migratory timepiece. In fact, in
the April-June period, tuna skirt the Egadian Archipelago to lay eggs on the shallow
bottom, whilst in the July-August period they again pass by to reach their native waters of
the Atlantic Ocean. Local acumen has it that the first fortnight in June is the optimum
period for tuna kills.
Today, the Mattanza at the Egadian Islands is just a dying flourish of the traditional tuna
fishery industry… now it’s much less romantic, and the hegemony of the Japanese
fishing firms. Bonagia, also close to Trapani, is the other site besides the Egadian Islands
where la Mattanza is still carried out – some locals say that the chores are still performed
just to please the visiting tourists.
The International Commission for the Conservation of Atlantic Tunas (ICCAT) is a
regulatory body established in 1969 which establishes annual quotas for each tuna-
country nation – quotas which are repeatedly flouted. The annual establishment of such
quotas results in the pitting of ICCAT against the European Commission, the latter eager
to safeguard the interests of fishing nations. The Mediterranean branch of the World
Wildlife Fund (WWF) has long campaigned for a drastic reduction of the annual catch
quotas and issues a monthly bluefin tuna bulletin.
This year’s tuna fishing was abruptly and prematurely shut down in view of the flagrant
disrespect towards established quotas. Our islands have assumed over recent years a key
role in the fattening of tunas, caught by purse seining during the May-July period, in
pens, and in the export of such tuna to Japan (almost 7 million kg of tuna of local
provenance have been exported over the last year). Spotter planes are sometimes
deployed for the location of large tuna schools – their use is permitted only during a few
weeks in June.
A possible panacea to the current tuna depravation could be its taming – i.e. breeding the
fish in captivity, to avoid taking it from the wild, as is the norm for countless other fish-
farmed species. After such attempts by the Americans in the past floundered, the
Australians are now bristling with optimism as a pilot project conduced by Clean Seas in
Port Lincoln, South Australia.
In 2005, a research team at the Spanish Institute of Oceanography in Puerto de Mazarron,
Spain, successfully retrieved eggs and sperm from captive Atlantic bluefin broodstrock,
performed in vitro vertilisation which yielded larvae. Hence, current omens are pointing
towards this sleek giant becoming yet another ‘cattle of the seas’.

To top