Bigfins from small beginnings

2293f67a-e7df-4e6e-8d59-eb04bd425665

Editor's Picks
Features Post
The brightest pupils
04 October 2021
Features Post
Dealing with egg ‘fungus’
04 October 2021
Features Post
Rathbun’s tetra in the wild
13 September 2021
Fishkeeping News Post
Report: 2021 BKKS National Koi Show results
13 September 2021
Features Post
The World's forgotten fishes
16 August 2021


Japanese ‘Bigfin reef squid' are being reared at a British aquarium for the first time.

Squid are the most difficult member of the cephalopod family to rear in captivity, but marine experts at the Sea Life displays development facility in Weymouth look set to succeed.

Aquarist Greg Casten hatched nearly 200 from eggs collected in the seas off Japan, and has managed to grow 35 of them from just a couple of millimeters five weeks ago, to around 3cm.

"There is a long way to go and we will undoubtedly lose a few more yet," said Greg, "but with 35 having made it through the delicate first few weeks the chances are good we’ll get some through to maturity."

Already having notched up rare breeding successes with mud octopuses and flamboyant cuttlefish, Greg’s biggest challenge with the squid has been their tendency to eat each other.

“They flourish best in small groups, but are also notorious cannibals, so I have to monitor them carefully and separate any that fail to grow as quick as the rest,” he said.

He has also had to source food – mainly plankton and tiny shrimps — in steadily increasing sizes to keep his tiny charges healthy and well fed.

Adult Bigfins – so called because their fins encircle their whole bodies — reach up to 33 cm/13", and are fished in vast quantities for the Asian food market.

They have the fastest recorded growth rate of any marine invertebrate, weighing as much as 600 grams (1.3lbs) after just four months.

They live for only six months however, by which time males can reach almost 90 grams (3.12 lbs).

The Weymouth project, for which a special new breeding unit had to be built to enable very close control of lighting, and the quality, temperature and flow of water, is — like the squid — still in its infancy.

"Our goal is to complete the life cyle,” said Greg, “to rear enough adults to produce more eggs, and then rear a second generation.

"All of this will be done behind-the-scenes in quarantine tanks with water flow systems that prevent the squid touching the sides and potentially damaging their very delicate bodies.

"The next stage will then be to develop suitable clear-acrylic tanks for them which will ultimately enable us to display these amazing creatures in our global network of Sea Life aquariums.

That is a desirable goal, he adds, because of the incredible light show that bigfin squid can put on almost from birth.

"Few creatures can rival them for inspiring wonder and fascination in the marine world, and that leads on naturally to concern for marine welfare and support for conservation efforts," Greg added.

Like octopuses and cuttlefish bigfin squid have millions of ink-sacs embedded in their skin and control the release of different colours from these to produce amazing shimmering colour patterns.

"It is even more dramatic in squid though," said Greg, "and Bigfins are also thought to have reflective cells that mean they can turn green in green light, blue in blue and so on, to render themselves almost invisible."

If Greg’s nursery performs as he hopes it will, bigfin squid could be dazzling visitors to Sea Life’s 40-plus aquariums around the world within two years.

Why not take out a subscription to Practical Fishkeeping magazine? See our latest subscription offer.