RELEASE THE KRAKENS! – The highly fecund Octopus

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The marine environment is home to a group of very advanced molluscs called Cephalopods which literally means ‘head foot’. Historically, sailors lived in complete terror of one such species, the Kraken, which was known for attacking sail ships in unchartered waters. In German, Krake means Octopus and co-incidentally, the images drawn of the beast from those times, more closely resemble the Octopus from all the other Cephalopods.

Gibraltar is home to at least two species of Octopus, Octopus vulgaris (the common) and Eledone cirrhosa (the horned octopus) with the former being found most abundantly. Of all of the invertebrates, the Octopus boasts the accolade of being the most intelligent and this was recognised in legislation when they were added to the protected list within the Animals (Scientific Procedures) Act 1986 in the UK.

Locally, their ecological importance has also been recognised with the introduction of protection being bestowed upon them during their breeding season. This has been an important move by the Department of the Environment and Climate Change in protecting our wildlife; it is also a move which should extend further to some other species and here are a few thoughts on why.

A species fecundity is its reproductive potential. Species with a high fecundity produce a high number of young but built in is the expectation of a very high mortality rate. By contrast, low fecundity animals have a very high offspring survival chance as they invest time and energy into a low number of individuals. Consequently, fecundity can be used as a proxy to assess a species potential sensitivity to over-exploitation. Highly fecund species tend to have greater tolerance to over-exploitation than low fecund ones. Octopus are highly fecund, producing hundreds of eggs per brood.

In this instance, the legislation is helping to prevent over exploitation by giving the animals a chance to secure breeding and hatching, before fishing can recommence. The logic is undeniable and is good news for ecologists and fishermen alike.

Up to now then, everything is good. But nature can have a way of throwing a spanner in the works. Octopus mating is a very dangerous affair as most species are sexually dimorphic, with the female being the larger of the two. Therefore, like with black widow spiders, male octopus have to breed by getting close enough to deposit a spermatophore under the female’s mantle without being eaten; sexual cannibalism is bad news for breeding. Males often have to sacrifice an arm to the females to ensure they escape the encounter. This loss of males has a pronounced effect on the male/female ratio.

Females, on the other hand, will sit by the eggs and protect them from any possible predators. She diligently and tenderly forms currents over the eggs as good water flow increases the chance of them hatching. During this time, she will not eat anything at all. This is regardless of whether an opportunity to feed comes her way. It is not known why they do this but females frequently starve to death during this period. Either way, her sacrifice ensures that the next generation get the best start possible.

Sexual cannibalism and hunger strikes do come at a cost though; within the family of Octopus, the consequence of mating or its produce, generally means that most individuals will only mate once, on average, over a lifetime. This is the key to why this fecund species is still sensitive to overfishing but also exposes why the new protection may not be enough. The tacit assumptions being that breeding is always successful and that at least two offspring survive to adulthood and breed. In any event, this would only ensure a maintenance of the number of individuals within the population if recruitment from other areas is ignored.

But it is a very positive step for the survival of these animals and should not be overlooked. As with most good environmental protection laws, often a hunting window works better than a breeding one. This strategy has already been applied to tuna fishing locally and the benefits of applying this to Octopus should be obvious.

Finally, hunting windows themselves may not be enough without ensuring that the Octopus prey items are in abundance to help full population growth. All the environmental legislation in the world will not stop a man in the desert from dying without access to some water! Therefore, the health of the ecosystem as a whole will be an important consideration and this work is urgently required locally to establish where we are presently.

So much like in the ancient Greek myths of Perseus – I am with Zeus in saying “Release the Krakens!”

 

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Otto the Octopus

Octopuses are highly intelligent animals with personality, memories and emotions. They are considered the best escape artists of the marine world.

One such octopus lived in a German aquarium but since there was not many visitors during winter, Otto was bored.

From time to time, he would decide to completely redecorate his tank, to suit his taste better, by throwing around its contents. Sometimes, he just threw stones at the glass. At other times, he entertained himself by juggling hermit crabs living with him…

One morning, the lights in the aquarium wouldn’t come on, there was a short-circuit. This happened the next morning and the next… For three days, the employees were trying to figure out what was happening until one night, Otto was spotted climbing to the rim of his tank and carefully squirting a jet of water at the 2000 Watt spot light above to turn it off.

The director of the aquarium said Otto was constantly craving attention and always came up with new stunts keeping the team on their toes.

Pretty cool animals these octopuses are!