Zoos and aquariums can be very controversial. There are some that love them whilst others hate them. Many feel aquariums are an important educational tool that help to engage the public and raise awareness. On the other hand, animal rights activists argue that they are cruel, inhumane and exploitative of sentient creatures that should be free to roam wild in their natural habitat. Many sharks on display in aquariums are indeed wild-caught animals that have been relocated into captivity, which raises a serious ethical dilemma. But do captive sharks ever get re-released into the wild? Can they survive it? And if they can, could aquariums hold the key to restocking wild populations of significantly endangered sharks?
A Gilded Cage?
Many sharks and rays that are on display in aquariums have come from the wild, but this does not mean that they then spend the rest of their lives in captivity. In fact, sharks rarely spend their whole lives in aquariums! This is especially true for the larger species or those that live offshore, which are often rereleased into their natural habitats once they can no longer be kept healthy and happy in captivity (Buckley et al, 2020; Jewell et al, 2023).
There has been some concern that, not only is it ethically questionable to capture wild animals in this way, but that their removal from wild populations could have serious implications for endangered species (Lee et al, 2015; Buckley et al, 2020).
For example, sawfishes (Family Pristidae) are amongst the most threatened animals on our planet today, yet they are commonly displayed in aquaria. Could extracting them from the wild mean their populations decline even further? (Lee et al, 2015; Buckley et al, 2020).
A Tool for Good
On the other side of the debate are those who feel that aquariums are vital tools for education and public engagement. Whilst in the past aquariums were somewhat of an entertainment destination, today they have transformed into educational and research centres. A lot of very important scientific studies are conducted in aquariums. Housing endangered animals (like the aforementioned sawfishes) raises public awareness and piques their interest in little-known species (Falk et al, 2007; Jewell et al, 2023).
"Aquariums are enhancing public understanding of wildlife & the conservation of the places animals live"
In fact, several scientific studies have actually proven that people who visit ethical zoos and aquariums learn a lot about ecology and animal welfare. It is now well established that these institutions provide people a deeper understanding of conservation issues, and even drive them to feel such a strong connection to nature that they are more likely to personally take action to assist in the protection of endangered species (Falk et al, 2007).
What's more, accredited aquariums play an important role in politics. Through their advocacy and out-reach work, aquariums engage a diverse array of stakeholders - from the public to NGOs to the government - which can be pivotal in driving conservation legislation forwards (Grassman et al, 2017).
"Aquariums keeping sharks are in a unique position to influence local, regional, & international attitudes & policies by acting as both educational & research facilities"
So they may have educational value and contribute to driving conservation legislation forwards, but can aquariums actually assist in restocking dwindling populations of endangered species?
There have been some very high-profile examples where releasing captive marine animals back into the wild has done very badly... in one incident a California sealion (Zalophus californianus) was eaten by a shark moments after it was freed! In another case, a king penguin died mere days after its release (Aptenodytes patagonicus). In fact, deaths are common when attempting to release captive animals. Some die during the move itself and others weeks or even months later, because the stress of the relocation procedure was simply too much for them (Jewell et al, 2023).
However, there have been several occurrences of captive sharks being been rereleased into the wild. Raggedtooth sharks (Carcharias taurus) have been freed from the Two Oceans Aquarium in Cape Town, for instance, and a juvenile great white (Carcharodon carcharias) from the Monterey Bay aquarium, in the United States (Smale et al, 2012; Weng et al, 2012).
In Western Australia, a large tiger shark (Galeocerdo cuvier) was successfully released after two years in captivity in the Ocean Park Aquarium. Scientists monitored this shark closely after it's release via an electronic tag that they had fitted to its fin. They noticed that the captive shark behaved slightly differently to wild sharks after it was freed - not diving in the same way and performing many tight turns rather than swimming in a straight line. The experts concluded it was moving in a similar manner to how it would have when it was housed in a tank, as it had not yet adapted to its new, more spacious environment (Jewell et al, 2023).
Similarly, in Australia captive largetooth sawfish (Pristis pristis) have been successfully rewilded with only subtle behavioural abnormalities. Like the tiger shark, subsequent monitoring showed that freed sawfish occupied smaller areas, were more sedate, and moved a little more slowly and less frequently compared to wild sawfish. Yet, their successful reintroduction into the wild (at least to some degree) offset the damage of their original extraction from the population (Grassman et al, 2017; Buckley et al, 2020).
"[Sharks] can survive aquarium release after years of captivity & they appear to behave similarly to wild-caught [sharks]"
Similarly, captive spotted wobbegongs (Orectolobus maculatus) have been successfully reintroduced to the wild in Syndey harbour. In this case, the sharks assimilated very well. Whilst the experts did note some differences in their seasonality compared to wild wobbegongs, they confirmed that their residency patterns and movements were similar to that of their wild counterparts. The scientists even confirmed the survival of one animal two years after its release, confirming that, despite their time in the captivity, the wobbegongs were capable of living amongst wild sharks, and foraged and evaded predators well (Lee et al, 2015).
So now that we know that sharks from aquariums can survive being re-released into the wild, there is hope that these institutions could become involved in breeding programs for endangered fishes; breeding sharks and rays in captivity, and then releasing them into the wild. As this technique would ensure a very high rate of survival to adulthood compared to wild-bred sharks, this could hold the key to boosting populations of seriously declining species (Lee et al, 2015; Buckley et al, 2020).
This may propel aquariums into an entirely new sphere of influence, whereby they are playing a much less abstract, and more significant and direct role in the conservation of endangered species. Let's hope they can do it! (Lee et al, 2015; Buckley et al, 2020).
"The release of captive-bred [sharks & rays] has the potential to be a valuable conservation tool"
Buckley KA, Crook DA, Einoder LD, Pillans RD, Smith LD & Kyne PM (2020). Movement behaviours and survival of largetooth sawfish, Pristis pristis, released from a public aquarium. Aquatic Conservation: Marine and Freshwater Ecosystems, 30, 2351– 2369. Access online.
Falk JH, Reinhard EM, Vernon CL, Bronnenkant K, Heimlich JE & Deans NL (2007). Why zoos and aquariums matter: Assessing the impact of a visit to a zoo or aquarium. Access online.
Grassmann M, McNeil B & Wharton J (2017). Sharks in captivity: The role of husbandry, breeding, education, and citizen science in shark conservation. Advances in Marine Biology, 78, 89– 119. Access online.
Jewell OJ, D'Antonio B, Blane S, Gosden E, Taylor MD, Calich HJ ... & Sequeira AM (2023). Back to the wild: movements of a juvenile tiger shark released from a public aquarium. Journal of Fish Biology. Access online.
Lee KA, Huveneers C, Peddemors V, Boomer A & Harcourt RG (2015). Born to be free? Assessing the viability of releasing captive-bred wobbegongs to restock depleted populations. Frontiers in Marine Science, 2, 18. Access online.
Smale MJ, Booth AJ, Farquhar MR, Meÿer MR & Rochat L (2012). Migration and habitat use of formerly captive and wild raggedtooth sharks (Carcharias taurus) on the southeast coast of South Africa. Marine Biology Research, 8, 115– 128. Access online.
Weng KC, O'Sullivan JB, Lowe CG, Winkler CE, Blasius ME, Loke-Smith KA … Ezcurra JM (2012). Back to the wild: Release of juvenile white sharks from the Monterey Bay aquarium. In M. L. Domeier (Ed.), Global Perspectives on the Biology and Life History of the White Shark (pp. 419–445). CRC Press.