What can you do if you find some cuttlefish eggs?

 

Prompted by some wonderful interventions by the sea-loving community (Sussex Underwater Facebook group has some excellent DIY interventions with explanations and images of equipment -  see here) and our staff's experience of raising thousands of cuttlefish in aquaria (Dr. Cooke managed a large marine research aquarium with a cuttlefish hatchery), we provide some relatively simple steps that may ensure stranded cuttlefish survival if you find them washed up on the shore. These are sentient animals that are likely to suffer (although it is debatable at which point these traits become present) and so doing something is arguably better than doing nothing. 

 

Once you set up the basic equipment there are some simple weekly tasks. The equipment can be purchased for less than £20, the only thing you may not have at home already is a means of replenishing oxygen (if you have kept fish in a tank you may even have this). In temperatures between 12 and 18⁰C development can take up to 56 days (two months) from first being laid.

Sadly, published peer-reviewed research shows that washed-up eggs returned to the water are very unlikely to survive, they need either reattaching to the substrate, a very tricky task or keeping the eggs safe until hatching. If the latter appeals to you then keep reading for suggestions.

 

This is not an especially difficult procedure but access to saltwater is vital and ideally, some home aquarium experience would be very helpful. It is much easier if you understand the nature of keeping aquatic animals (nitrogen cycle, oxygen provision, etc)

1) You will need a bucket (white will absorb less heat than black if left in the sun), with seawater, an aerator/air stone, and ideally access to more seawater or a mature saltwater aquarium filter. The bucket size and amount of water depends on the number of eggs. A very rough estimate might be 10 eggs per liter of water – but more water is always better, see below. Remove any seaweed or hitchhiking animals as they will excrete ammonia and risk the health of your eggs, which are in a closed environment.

2) Cuttlefish embryos are able to breathe through the egg outer layer and constantly need oxygen replenishing and the removal of carbon dioxide. The aerator and air stone agitate the water surface allowing more oxygen to dissolve.  Even if you have lots of water, the water needs to be moving to allow new oxygen to reach the outer layer of the eggs. It must not be too vigorous. Constant agitation to the eggs may cause premature hatching: if the yolk is still attached after hatching the baby cuttlefish will not survive, this is poorly understood but nevertheless but appears to be true.

3) As the yolk is used up, the cuttlefish produce ammonia which is toxic. We have detected ammonia build-up in rescued eggs in buckets and this might be a problem. If you have a mature aquarium filter from a marine tank you can use this to break down the harmful ammonia (the eventual product, nitrate, is less of a problem, especially at this stage of their lives). Another way to prevent ammonia from being a problem is changing the water, which dilutes/removes the ammonia. We suggest (but this is by no means the only way), roughly 25% per week when very early in development moving to 50% towards the end. Easy to find and cheap home aquarium test kits will quickly detect any ammonia present.

4) Keeping them outside is probably best, in a cool shaded area, where temperatures are more stable. They can tolerate temperatures up to about 27⁰C, the higher the temperatures the quicker the embryos will develop. Avoid rainwater so perhaps add a translucent plastic lid, but allow some access for air exchange.

5) How do I know the eggs are OK? The eggs will swell as they develop, sometimes so much the eggs become a little translucent and you can see the embryo developing. Some eggs are white or translucent to start with and it is easy to watch the development all the way through. These are laid towards the end of the female's egg-laying phase and perhaps like a printer, run out of ink. If you see anything growing on the eggs they may have died. Sadly, many, especially those towards those at the end of egg-laying, or those that have been exposed for too long in the air, may not be viable no matter what you do. Doing something will be better than nothing though, saving just one is worth the effort.

 

6) What do I do when they hatch? You must get them to the sea within 24 hours, if not ASAP. Cuttlefish babies are voracious eaters and will quickly starve if they are not in their natural environment. If you are OK with catching and supplying live prey, not an easy task at all, they will eat small crustaceans such as mysids, these are ideal in size and nutritional requirements. But the best place for the babies is in the water nearest to where they were found.

Will this work for squid eggs?

 

Good question! Probably! Though squid egg masses have far more 'squidlets' and we suspect the ammonia levels may be far higher than similar masses of cuttlefish eggs as the bunches have many more embryos. Squid begin life as 'paralarvae' (and do a mini metamorphosis into the squid we recognise), they may require specific species of zooplankton to survive which are extremely difficult to provide, and so should not be kept after hatching. We do not recommend keeping hatched squids, like cuttlefish, the best place for them is in the sea.

Bibliography:

Goff, R.L. and Daguzan, J., 1991. Growth and life cycles of the cuttlefish Sepia officinalis L.(Mollusca: Cephalopoda) in South Brittany (France). Bulletin of Marine Science, 49(1-2), pp.341-348.

Grigoriou, P. and Richardson, C.A., 2004. Aspects of the growth of cultured cuttlefish Sepia officinalis (Linnaeus 1758). Aquaculture Research, 35(12), pp.1141-1148.

Guibé, M., Boal, J.G. and Dickel, L., 2010. Early exposure to odors changes later visual prey preferences in cuttlefish.

Jones, N.J.E., Ridgway, I.D. and Richardson, C.A., 2009. Transport of cuttlefish, Sepia officinalis, eggs under dry and damp conditions. Journal of Molluscan Studies, 75(2), pp.192-194.

Nair, K.P., Thomas, P.A., Gopakumar, G., Vincent, S.G. and Omana, T.A., 1985. Some observations on the hatching and post-hatching behaviour of the cuttlefish Sepia pharaonis Ehrenberg. CMFRI Bulletin, 37, pp.157-159.

Sykes, A.V., Gonçalves, R.A. and Andrade, J.P., 2013. Early weaning of cuttlefish (Sepia officinalis, L.) with frozen grass shrimp (Palaemonetes varians) from the first day after hatching. Aquaculture Research, 44(12), pp.1815-1823.

Tonkins, B.M., Tyers, A.M. and Cooke, G.M., 2015. Cuttlefish in captivity: An investigation into housing and husbandry for improving welfare. Applied Animal Behaviour Science, 168, pp.77-83.

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