CUTTLEFISH CULTURE
by  Bob Alexander (Weymouth)



 

British Cuttlefish:

SEPIA

Sepia officinalis   Linnaeus
Sepia elegans  d'Orbigny
Sepia orbignyana  Férussac

SEPIOLA

Sepiola atlantica    d'Orbigny
Rossia macrosoma   (Delle Chiaje)
 
 
 


Sea Grapes

The black eggs of the Cuttlefish, Sepia officinalis, can be collected from early spring until mid-summer, beyond the low spring tide mark in sea grass or around the bottom of seaweed fronds. The black eggs, generally called "sea grapes" are all of a similar size, about 15 to 25 mm long and are usually set in bunches.

Collected eggs are best suspended in a net to keep them clear of the bottom, in a small hatchery aquarium at 14° C in fresh seawater.  It is advisable to have a mature fine gravel filter (not coral gravel) and carbon box filter already in place for when the eggs hatch, with an additional air stone providing good circulation around the eggs.

Hatching Eggs

When the eggs hatch, each will produce a perfectly formed cuttlefish between 12 and 20 mm long1, able to swim, squirt ink and feed.  Newly born cuttlefishes are very prone to damaging themselves, particularly when trying to make a shallow burrow in the filter bed if sharp gravel has been used.  The most vulnerable part of them is their rear end where the skin is easily damaged and least likely to heal.   Although an open wound at the rear end is not likely to heal, it does not seem to affect their growth or well being but it does make them vulnerable to disease or attack.

The hatchlings will begin to feed after 24 hours on small live mysids2 (about 10 mm long).  Well-fed hatchlings will grow quite fast, doubling their size in 21 days, and are eager to try any new live food.

Dead food at this stage of their life is simply ignored.  At 30 to 40 mm long; they will to eat crabs of 5 to 10 mm3 and prawns nearly as long as themselves.

Ink Discharges

If available, the young cuttlefish will attempt to eat larger creatures than it can cope with, and as it releases the unmanageable prey it will squirt out a jet of black ink to cover its retreat. One cuttlefish squirting ink can immediately frighten others into doing the same, so great care must be taken not to frighten them when introducing live food or when cleaning the aquarium.

When first ejected the ink has a thick slimy consistency and can be removed from the aquarium with a fine hand net; if left, within minutes it begins to dissolve and colour the whole aquarium grey.  The dissolved ink will be removed from the water quite readily by the carbon box filter whilst the cuttlefish are small, but as they grow to about 4 cm it is best to change the box filter for a protein skimmer for more rapid and effective ink removal.

Growing To Maturity

After 3 months and attaining a size of about 5 cm, their growth rate will slow down and they will spend more time lying on the bottom in their small shallow burrows. The aquarium size does not appear to affect either the size or rate at which they will grow.  Eventually they will either have to be moved from the hatchery to a bigger aquarium to give them more room, or some will have to be removed to make more room for those that are left.  Over-crowding will make them become more and more aggressive towards each other during feeding, resulting in the tank being continually black from ink squirting.

Illustrations by Chris Hicks (Northolt)

 As a guide, a 36"x12"x12" aquarium is the minimum requirement for four 6 cm cuttlefish, and at least ten live prawns should be put in together when feeding to avoid fighting. Fighting, in some instances, can be to the death. It should be remembered that in their natural environment cuttlefish are solitary creatures, only coming together to mate.

Temperature Control

In the winter the aquarium temperature should be kept at 14° C  if growth is to be maintained, with an absolute minimum of 10° C. At the lower temperature, although the cuttlefish will show an interest in live foods it will not have the same appetite to pursue it.   At a temperature of 8° C and below they will begin to die.

As the cuttlefish grow, their normal mature outward characteristics will begin to show, a striped appearance changing to a throb when feeding, a white body with two distinctive black eye-like spots in the centre of their back to warn off attackers, a skin texture changing from smooth to mottled at a moment's notice, and finally the ability to flatten out its body and stretch out its fins to make itself look as big as possible when disturbed in its burrow by other cuttlefish.
 

Feeding

As the cuttlefish reaches maturity it is noticeable that its head is smaller in proportion to its body than it was when it was immature.  Also the lower tentacles are much more developed and thicker than the others are. In the mature cuttlefish these are used very much as arms or legs.

The mature cuttlefish should be fed a varied diet to maintain their health and growth rate. Live crabs and prawns can make up the bulk of their diet but dead fish such as whitebait and small sprats will also be accepted. If dead food is ignored, try moving it around on a feeding stick to attract their attention.

At two years old, being at least 18 cm long, a choice should be made and your future breeding pair should be selected.
 
 

Breeding

Select the largest male and female available and put them into an aquarium of at least 48"x15"x18". This will allow plenty of room for continued growth and for the pair to avoid each other. A number of smooth-faced stones with firm stalks attached should also be placed strategically upright in the aquarium in preparation for the female to stick the eggs on.

The male, normally slightly larger than the female, can be easily distinguished by his dark striped appearance when in the vicinity of other cuttlefish or by his generally aggressive behaviour as he insists that other cuttlefish take notice of his mating display. The female can be easily distinguished by her overall plain appearance during the male's display ritual. Mating is easily recognised. The male will approach the female, generally by swimming alongside her, displaying his stripes in deep red brown, and they will come together and grasp each other about the head. Unlike fighting, no ink is ejected by either partner.

Soon after their first mating they will begin to mate four or five times a day. At this stage feeding becomes sporadic and soon after they will stop feeding completely. Evidence of the mating can be seen by the empty pink spermatophores of the male lying in the bottom of the aquarium as well as the damage they cause to each other about the head.

Egg Laying

Within two weeks of the first mating the female will begin to lay her eggs.  Each egg is laid separately, appearing slowly from between her middle tentacles and stuck into position on the stalk, held steady by the stone. This will then be repeated until all the eggs have been laid.

The number of eggs laid will vary, but their total volume will be about half of her body size. Within three or four days all of the eggs will have been laid and both cuttlefish, sometimes almost blind through eye damage, will bury themselves into the gravel as, slowly but surely, their life ebbs away. Although the eggs are generally black it is not unknown for some to be grey or even white, with some being large and others small. Within a week or two those that have not been fertilised will begin to shrivel up.
 

Behaviour

From hatching the young cuttlefish will immediately recognise its own kin and will not attack other hatchlings but stalk and prey upon any other creatures available. Stalking and catching prey is very much a learned behaviour4 and can initially lead the young cuttlefish into many problems. Although the hatchlingswill immediately recognise mysids as food, their first attempts at catching them are very much rushed and clumsy.

Within days they will learn to stalk their prey slowly so as not to frighten it, and to attack it from the side where it presents a larger target, but as these skills are learned, enthusiasm often overtakes their ability to judge distance and many prospective kills are missed by being out of range at the final attack.

Growing Cuttles

As the young cuttlefish grow and become adept at catching mysids, prawns will need to be introduced to satisfy their ever-growing appetites.

 Initially the cuttlefish will attempt to attack almost any size of prawn, including those that it obviously cannot cope with. This can lead to the cuttlefish grasping on to prawns that are stronger swimmers than it is, and being pulled at tentacle length around the aquarium by the indignant prawn. When this happens, the cuttlefish will invariably squirt out ink as it releases the prawn, and the general commotion of the whole event will prompt others to squirt ink in fright.

Hunting

Very much the same learning process happens as each new species of food is introduced, but experience is built on until the mature cuttlefish is a formidable predator.

Observing the speed and skill of the mature cuttlefish capturing a crab5, using its water jet to expose it and turn it around, then darting in to attack the crab, which is often larger than the size of its own head, from the rear to avoid its snapping claws, is a sight to chill.

Not all smaller species are afraid of cuttlefish so the keeper must exercise some care when introducing new food.   The two most common species to be avoided are any of the gobies or blennies, because when cornered they will immediately turn and attack the stalking cuttlefish and disarm it by biting its eyes.

Adult Hunting Observations

As the cuttlefish matures it is noticeable how it develops and uses its tentacles.  The top pair are always held up like periscopes as it stalks its prey, allowing space for the tentacles to shoot out from their pockets; the lower pair develop into a different shape, being used as legs to walk along the bottom or to hold them steady when attacking prey.  The lower tentacles are often held out from the body at right-angles to keep other cuttlefish away, and are prominently used in displaying stripes to prospective mates.

The most fascinating way that the lower tentacles are used is to hold additional food. When a number of large prawns are introduced, mature cuttlefish will often catch one, kill it with a bite, hold it under its lower tentacle and then pursue another prawn. If sufficient food or prawns are not put in to allow plenty of choice, those cuttlefish that are slower will often attempt to steal the prawns held by others in this way, and this can lead to fighting.

Fighting over food is common if the aquarium is overcrowded, and if measures are not taken to thin them out the smaller and weaker will eventually be killed and eaten by the larger and stronger. It would seem, from my own observations, that aggressive behaviour and stealing is learned and can become the norm with particular cuttlefish. This can be very difficult to stop if those situations that encourage it are continually allowed to develop.

For further information on cuttlefish behaviour it is strongly recommended that prospective keepers take advantage of the vast number of studies undertaken and read at least the books mentioned.

Notes:

1 Cuttlefish are measured along the length of their back from front to rear, this being the length of their shell,
and does not include the head.
 

2 Mysids are a small shrimp-like crustacean with numerous species in the order Mysidacea.
 

3 In scientific circles, crabs are measured across the back of their body shell at the widest point.
4 Invertebrate Zoology, by R. D. Barnes.  4th Edition, Saunders College.  Studies of octopus ability to learn
and recognise shapes.
Animal Behaviour, The Oxford Companion to-, by D. McFarland, Oxford University Press.   Maturation,
description of young cuttlefish catching mysis.
5 Living Marine Molluscs, C. M. Yonge and T. E. Thompson, Collins.   See Cuttlefish, squids and octopods, illustrates colour patterns assumed under particular conditions. ISBN 0 00 219099 0.
The Invertebrates, R.  McNiell Alexander, Cambridge University Press.

The BMLSS also recommend 'The UFAW Handbook on The Care & Management of Cephalopods in the Laboratory' by P. R. Boyle (UFAW 1991). ISBN 0 900767 72 3

Additional Notes:

The prawns in the text are of the genus Palaemon.  Cuttlefish will also feed on shrimps Crangon, which inhabit the sand shallows.

Coral gravel is eschewed because it tends to have sharp edges which can damage the newly hatched Cuttlefish.

British Cephalopoda
Biological Notes
by Andy Horton.

The Cephalopoda are a class of highly evolved molluscs that include the cuttlefishes, squids and octopuses.
The Giant Squid, Architeuthis diux, is probably the largest invertebrate animal on this planet. ‘Probably’, because we do not know what other krakens may inhabit the deepest oceans. The Giant Squid is only known from monsters washed up on the shore, and occasionally on British shores, and from the stomachs of the predatory Sperm Whale, Physeter macrocephalus.

The common Cuttlefish is by far the commonest British species although two other smaller species Sepia elegans and Sepia orbignyana (? validity) have been recorded. Over the sandy shallows a very small cuttle, appropriately known as the Little Cuttlefish, Sepiola atlantica, can be quite commonly caught in shrimp (push) nets (see 04.04.26-27). It only grows to 20 mm compared to 400 mm of the Common Cuttlefish.

Transporting Cuttlefish

At the beginning of April this year Andy Horton and Len Nevell visited Bob Alexander in Weymouth to have a look at his Fish House and to take home some Cuttlefish that were outgrowing their tank. They were about 6 cm long and were feeding readily on prawns so there will not be a problem feeding them. However, I obviously had not taken in his article properly, as I did not anticipate the palaver of transferring Cuttlefish from the aquarium to the large buckets.

It all centred on the Cuttlefishes’ readiness to discharge their ink at the first sign of danger. Gently does it. Bob lifted the Cuttlefish one at a time into the 20 litre (5 gallon) bucket. The Cuttlefish settled on the floor of the bucket. Three were safely transferred and I wondered what all the fuss was about. The fourth went in and immediately squirted ink and the water quickly went black. Then the others started squirting.

A change of water was necessary, but there was still ink in their sacs and it took three water changes before they were settled in clear water at the bottom of the bucket, having apparently discharged all their ink. The ink is meant as a distraction to a potential predator rather than a screen of coloured water to obscure their jet-propelled retreat.

We filled up the bucket with fresh sea water and started our journey back to Sussex. A few hours later I arrived home with a bucket full of black water and the healthy Cuttlefish. Four Cuttlefish were introduced to my aquarium and immediately settled down. After a few days they started squirting ink and the aquarium water turned black. Unfortunately, the aquarium proved to be too small and the protein skimmer could not be made to work properly so the Cuttlefish were released into the sea.
 

Taxonomy
Common Cuttlefish
 
Phylum:  Mollusca 
 Class:  Cephalopoda
 Order:  Sepioidea
 Family:  Sepiidae
 Genus:  Sepia
 Species:  officinalis 



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