5th January 2017
We're delighted to welcome the first Zebra shark pups (Stegostoma fasciatum) to be conceived and hatched in the UK. After witnessing courtship and copulatory behaviour between our pair in November 2014 we observed laying cues - where the female begins to slowly circle potential lay sites. Our female began laying eggs at the beginning of March 2015, with a total of 29 eggs being produced between March and July. Of these 29 eggs, 18 contained no yolk and 11 were potentially viable.
The egg cases were laid in our 10m multi-taxa Endless Oceans display and were removed as soon as they were found to eliminate any risk of predation. The eggs were moved to an incubation tank behind the scenes so that any development could be carefully monitored. The incubation tank, attached to our Coral propagation system, maintains a consistently high level of water quality and is a very stable system, which is key to successfully incubating the eggs. Females typically lay eggs in 6-8 day intervals for a period of 4-5 months, with incubation taking between 120 and 160 days. The incubation period is dependent on water temperature - the higher the temperature the shorter the incubation.
The eggs were candled fortnightly using a high powered torch to gauge their viability. Of the 11 potentially viable eggs only 6 developed embryos. The eggs continued to be candled every 2 weeks to monitor internal development and the egg cases carefully cleaned to remove any build-up of detritus.
On emergence the newly hatched pups are given a thorough health check and their weight and length is recorded. They begin feeding 1-2 weeks after hatching and are being fed 2-3% of their body weight daily. This is typically spread over 3 feeds as the sharks will not consume a large amount of food in one sitting. Plastic forceps were used to hold a small piece of squid just in front of a juveniles’ mouth and once feeding on a regular basis, new food types are introduced, such as mackerel, prawn and mussel.
The sharks will be weighed and measured weekly to monitor development and feeding is adjusted accordingly. We are pleased to say that so far all 6 juveniles are growing and developing well.