Life after death: how we hatched live shark pups from dead parents
Six years ago, researchers asked a radical question: could eggcases taken from trawler-caught sharks still hatch live, healthy young?
Back in December 2012, I met up with Greg Nowell, co-founder of Sharklab-Malta, a non-profit NGO founded in 2008. Sharklab collaborates with shark researchers on a global and local scale, with an overall mission to highlight the current plight of sharks in our oceans whilst increasing awareness and education of the public.
Greg was interested in my experience working with neonate small spotted catsharks (Scyliorhinus canicula) and the greater spotted catshark (Scyliorhinus stellaris); in the UK these are usually known as the lesser spotted dogfish and bull huss, respectively. At Macduff Marine Aquarium I’d worked with both species, as well as on the maintenance of viable eggcases, which resulted in successful hatching and rearing of shark pups.
Successfully hatched out bull huss ( Scyliorhinus stellaris) pup ready for release. Photograph: Rasmus Loeth Petersen.
Greg was interested because earlier in 2012 he had started going to the wholesale fish market in Valetta to recover eggcases from dead S. canicula and S. stellaris that had been trawl-captured in the Mediterranean. He had been placing the eggcases in a home aquarium system to see if they were viable and, if so, to observe development.
A study by Ballard et al in 1993 had shown that viable eggcases could be removed from dead S. canicula, but the embryos in used purely to observe development. Greg’s idea was to take this further: allow the sharks to hatch, rear them for a few months to ensure they were feeding well and then release them back into the wild.
In my opinion, this was one of the best, most direct and novel hands-on approaches to shark conservation I had come across. Not only did it result in a positive outcome from the result of direct action but the potential for public engagement for this type of project was huge.
Greg’s preliminary work in 2012 soon expanded with the recruitment of Lydia Koehler as science officer, Pamela Mason as education coordinator and Dave Mason as membership coordinator. All three, plus numerous volunteers, were (and still are) involved in eggcase recovery and retrieval from the fish market. This, combined with the aquaria maintenance and shark husbandry information I supplied, all coincided with the opening of the Malta National Aquarium in October 2013.
A collaboration was soon formed between the aquarium and Sharklab, which meant that optimal hatchery tanks were available on a larger scale. It also meant information about the project could be displayed at a public attraction, thus reaching a larger audience and spreading further awareness about sharks and their conservation.
A 14 to 15-week-old shark embryo. Photograph: Greg Nowell
All of this work has culminated in our recent publication of a paper in the journal of Ocean and Coastal Management, detailing the project. To date, a total of 689 eggcases have been recovered from dead sharks at the market; of these, 278 have developed and hatched out successfully with 237 S. canicula and 41 S. stellaris released back into the wild. A further four S. stellaris were retained by the aquarium for educational display purposes.
All shark releases so far have been public events, with the public and various dive clubs and organisations coming along to wave the sharks off. Dive clubs have even supported the releases by providing equipment such as air tanks for the divers involved. The shark pups can be viewed for a short period of time before they are taken down to depths of around 20 metres in a suitable habitat and released by the volunteer divers.
But how is any of this possible? Well, it’s largely due to the specific species chosen for this approach.
All sharks utilise internal fertilisation, but depending on how long females retain the fertilised eggs, sharks can be divided into two main groups: oviparous (egg-laying) and viviparous (live-bearing). Viviparous species can be further divided into aplacental (yolk-dependent) and placental forms. Some aplacental species such as the sandtiger shark (Carcharias taurus) also utilise embryophagy, whereby the largest embryo will consume the other developing embryos. It’s also worth noting the other amazing strategies sharks are capable of. Certain species, including the bonnethead shark (Sphyrna tiburo), can even undergo automictic parthenogenesis, otherwise known as virgin birth, during which an unfertilised egg merges with another cell from the female to form a foetus.
At any rate, it is the oviparous nature of both S. canicula and S. stellaris that allows for this type of direct conservation action. As long as the eggcases have developed to the point that the yolk is sealed within the case (mating has usually occurred quite some time prior to this) and the animals have not been frozen during transportation to the fish market, then there is the possibility that these eggcases will be viable.
As our paper points out, despite the fact that the number of sharks released has a negligible influence on the stability of the overall wild populations of S. canicula and S. stellaris, it positively impacts shark conservation efforts by attracting public attention and fosters cooperation with relevant stakeholders, including aquariums, dive centres and schools.
Increased knowledge through targeted education and awareness campaigns together with direct engagement such as that achieved by Sharklab is known to lead to an increase in shark conservation support. This is crucial for regions such as the Mediterranean, where there is an ongoing observed decline of elasmobranch stocks. After all, once education and awareness campaigns have public support, this can then be used to drive policy action and market demands to further aid elasmobranch conservation.
This project by Sharklab-Malta is one that can be adopted and adapted for oviparous elasmobranch species worldwide. For example, I have successfully replicated this with S. canicula landed in the North Sea. It is without a doubt valuable for future conservation efforts.
Abdulla, A, 2004. Status and conservation of sharks in the Mediterranean Sea. IUCN Technical Paper 144 (7).
Ballard, WW, Mellinger, J, Lechenault, H, 1993. A series of normal stages for development of Scyliorhinus canicula, the lesser spotted dogfish (Chondrichthyes: Scyliorhinidae). Journal of Experimental Zoology 267 (3), 318–336.
Friedrich, LA, Jefferson, R, Glegg, G, 2014. Public perceptions of sharks: gathering support for shark conservation. Marine Policy 47, 1–7.
Koehler, L., Smith, L.E., Nowell, G., 2018. Recovered and Released – A novel approach to oviparous shark conservation. Ocean and Coastal Management. 154. 178-185.
O’Bryhim, JR, Parsons, ECM, 2015. Increased knowledge about sharks increases public concern about their conservation. Marine Policy 56, 43–47.
Ward-Paige, CA, Keith, DM, Worm, B, Lotze, HK, 2012. Recovery potential and conservation options for elasmobranchs. Journal of Fish Biology. 80 (5), 1844–1869.