“It’s complicated…” is always the beginning of my response when asked about raising and culturing jellyfish.
People are often astounded at all the intricacies of a jellyfish life cycle, and that successfully propagating each of the four unique stages requires caring for four very different creatures during the process. These are the details and complexities that make being a jellyfish specialist frustrating at times, but they are also the challenges that make working with these species so rewarding.
On the surface, in situ populations of jellyfish appear to be increasing, at least for now, so why is ex situ propagation of jellyfish important to zoos and aquariums? First, wild jellyfish blooms are rarely predictable, and collection of the animals is subject to variations in weather, staffing, and transportation.
Whether you are collecting them yourself or have hired someone to do the collecting for you, it can easily become an expensive and fruitless venture—not ideal when working to stock or maintain large exhibits year-round. Next, wild medusae generally have a shorter longevity than those raised in zoos and aquariums. In their natural habitat, jellies grow quickly on an endlessly diverse supply of zooplankton and invest as much energy as possible into reproducing in one season.
In contrast, with a consistent (albeit less diverse) food supply and water temperature, the longevity of medusae may exceed two years when raised in zoos and aquariums. Finally, although there are still costs associated with feeding, housing, and maintaining ex situ cultures, cultivated jellies are much less costly. For example, when compared to collecting wild specimens, the direct monetary expenditure for production and/or the acquisition of surplus animals from another facility is reduced; environmental impacts (i.e., use of fossil fuels and single use plastics for transport) are lowered; and cultivation has no additional staffing expenses, travel costs, and risks that are incurred during collection.
Historically, the specific goals of jellyfish population management have centered around developing and sharing techniques to culture new species, maintaining in-house exhibits and cultures, and sharing surplus with other facilities that may be in need. This cooperative management strategy was best described in 2005 by Michael Howard at Monterey Bay Aquarium in Monterey, Calif., when he referred to it as “Jelly Karma.” During a presentation at the Regional Aquatics Workshop that year, Howard highlighted “the importance of sharing knowledge and surplus animals so as to build one’s Jelly Karma.”
Unlike more well-established or traditional species management programs, little emphasis has been invested in the coordination of tracking and maintaining genetic lineages. While maintaining genetic diversity, eliminating unneeded surpluses, and minimizing pressure on wild populations are just as important in the jellyfish world, fitting our gelatinous cultures into the classic Species Survival Plan® program structure with pedigree-based management of individuals hasn’t seemed like the right solution. However, more recent growth of and familiarity with group management approaches is promising.
Merging the complexities of group management with the intricacies of cultivating jellies will be a significant challenge to establishing a successful and useful jellyfish management program. While jellies may not be experiencing the same pressures as other SSP populations yet, now is the ideal time to start working toward this mission.
First, we can take steps to maintain the highest level of genetic diversity in our cultivated populations. In addition to gaining a better understanding of jellyfish population genetics through scientific research, we can explore options like those piloted by the Aquatic Collection Sustainability Committee’s new larval programs. At the 2021 virtual Association of Zoos and Aquariums Annual Conference, Dr. Barbara Bailey and Hap Fatzinger presented a plan to bring wild fish stock into a few facilities that specialize in rearing, and later distribute the aquarium-hatched offspring to recipient facilities. Applying this model to jellyfish would be quite simple and, at some facilities, is already in practice for the collection of mature gonad tissue and in vitro cultivation of founder polyp colonies. There are potential limits to following the larval programs model that need to be part of the discussion, such as location of and access to wild stock, staff training, and long-term community and facility buy-in.
Next, there are a few SSPs, such as the Lined Seahorse SSP and Lake Victoria Cichlid SSP programs, that can serve as excellent models for programs that track group lineages instead of the traditional individual pedigrees. If a Jellyfish SSP is established in a similar manner, the management committee would need to define which phases of the jellyfish life cycle to track. Medusae groups would be easy to follow, count, and record, but their shorter longevity and large infrastructure requirements could be troublesome to manage efficiently. It may be more logical, and less intense to track polyp colony groups. Colonies, as noted earlier, are easier to produce from wild stock, are longer lived, and require less space. They are also very easy to transport, split, and share with other facilities, making them an ideal candidate for distribution and tracking.
Finally, a living database facilitating real-time exchanges could be a useful tool moving forward. Current directories and census efforts become outdated within weeks of being refreshed, making it difficult to maintain an accurate picture of managed jellyfish populations. The benefits of creating a living database of current zoo and aquarium populations, productive cultures, available surplus, and participating facilities would help mitigate the “boom and bust” nature of the jellyfish lifecycle. An active community interface that would allow aquarists to plan for upcoming exhibit needs would be most beneficial, whether it is producing new medusae for an opening exhibit or finding homes for an expected surplus. How this could be executed and maintained remains to be determined, but advances in online, real-time database technologies, such as ZIMS, are always evolving.
Regardless of which of the three approaches above are implemented, an effective solution to jellyfish population management will merge the existing cooperative efforts of Jelly Karma with the coordinated and formal group management efforts. Organizations across the globe, like the Group Management Initiative, the IUCN’s Conservation Planning Specialist Group, and the AZA and its members are working together to re-think the traditional guidelines and tools of the aquarium and zoo world to support the type of group-based management that jellies, and other aquatic invertebrates, need before conservation and genetic diversity do become critical issues for these species.
Sharyl Crossley is a senior aquarist, Tennessee Aquarium.
Special thanks to Dr. Kathryn M. Rodriguez-Clark of the Smithsonian’s National Zoo and Conservation Biology Institute and Dr. Gina M. Ferrie of Disney's Animal Kingdom for sharing their knowledge and passion of population science and management with me. This article would not have been possible without their insights