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Having existed for over 500 million years, jellyfish are amongst the oldest animals living on our planet today. More than a thousand different types can be found in the ocean, where they occur from the Arctic to the Antarctic, and from the sea surface to abyssal depths. Since many jellyfish, especially the larger and more conspicuous species, have a seabed-bound polyp stage, they can be particularly common in coastal areas where they interact with fishers and other users of the nearshore waters. This is of concern, because populations of some species are believed to have increased in numbers in some areas of the world following possible human-induced changes to their environment, and that jellyfish may replace important pelagic stocks.

Even though these planktonic marine animals are thought to play a significant role in ocean ecosystems as both predators and prey, our understanding of them either as a potential resource or as a threat to current resources and to biodiversity is poor. In fact, jellyfish have received little in the way of research support to date – especially around Africa.

Chrysaora agulhensis, named because it is mostly found over the Agulhas Bank off South Africa, is one of the new species likely to be discovered from the surveys. © Peter Southwood	Over five tonnes of jellyfish (Chrysaora fulgida) were caught in a single trawl by the Dr Fridtjof Nansen off Namibia in 2017. © Mark J Gibbons

An opportunity to learn more about a poorly understood animal
To update and broaden the understanding of jellyfish in this region, the EAF-Nansen Programme has added a component on jellyfish to its Science Plan, and work is being carried out in collaboration with dedicated jellyfish scientists, such as Professor Mark J Gibbons and research students from the University of the Western Cape (UWC) in South Africa.

"There are a number of very good reasons why jellyfish have been included as a research topic in the EAF-Nansen Programme," said Professor Gibbons. "Firstly, it provides us with an opportunity to learn what types of jellyfish can be found around Africa and in the Indian Ocean: it gives us a chance to document diversity in parts of the world that are still poorly documented. Secondly, we can start to look at how patterns of abundance are linked to the environment, the viability of any potential exploitation and it will also allow us to more fully understand their role in marine food chains through ecosystem modelling."

The work took off in 2017 and continued in 2018, when samples were collected from 98 trawl stations during the research surveys conducted by the EAF-Nansen Programme's Research Vessel (R/V) Dr Fridtjof Nansen. Ultimately, a greater number of collections was made at stations along the west rather than the east coast of Africa, as these cruises had jellyfish scientists onboard.

Early research results reveal species that could be new to science
With samples remaining to be analyzed in detail, the final conclusions of this effort are still pending. However, initial findings reveal that species of Atolla, Aurelia, Cephea, Cyanea, Chrysaora (at least two species), Mawia, Pelagia, Periphylla, Rhizostoma and Rhopilema have been identified, as well as at least one box jelly, or cubozoan. Box jellies represent a health hazard and one of the most venomous marine animals known, the sea wasp (Chironex fleckeri) from North-east Australia, kills a number of people every year. Surveys conducted off both the west and east coasts of Africa have revealed the presence of two species from this same genus, both of which are likely to be new to science. "New species in a number of different genera will be uncovered amongst the samples" explained Professor Gibbons, and added that "collaboration with interested scientists in the region is encouraged".

Most of the jellyfish that have been collected to date have been relatively uncommon, with mesopelagic species of Atolla, enjoying the widest geographical distribution. Off the mouth of the Zambezi River in Mozambique, a very large catch (measuring several tonnes in weight) of a new species of Aurelia was made in water shallower than 30 meters. And in just 10 minutes of trawling in the pelagos off Namibia, the Dr Fridtjof Nansen managed to catch more than 5 tonnes of the jellyfish Chrysaora fulgida. This species is a Benguela endemic and populations are known to have increased there in the last few decades, likely as a result of the overfishing of sardines and anchovies at the end of the 1960s and early 1970s. Professor Gibbons noted that "trying to determine the amount or biomass of jellyfish in an area is fraught with problems, especially if you are using a net to catch them because they get damaged very easily. Working with our colleagues at the Institute of Marine Research (IMR) in Bergen, we have been developing multifrequency hydro-acoustic tools that can be used to do this same task quickly and remotely without the need to sample, and with colleagues at fisheries in South Africa, we are in the process of using these tools off Namibia."

Building capacity for the future of jellyfish research
Capacity development is a large part of the work on jellyfish by the EAF-Nansen Programme, and much of this is being conducted by South African students with support provided by South Africa's National Research Foundation. "Being able to take part in the research surveys by the R/V Dr Fridtjof Nansen has not only provided me, but also my fellow students, with samples and data for our research projects" said Roxy Zunckel, an MSc student at UWC. "I am looking at reproduction in the Benguela compass jellyfish Chrysaora fulgida, and my findings will enable me to test observations made by colleagues in nearshore environments and will give us an insight into the success of this species in the region". Michael Brown, another MSc student at UWC says "I am studying the evolution of Aurelia around Africa and it is just so exciting to see live (or at least fresh) jellyfish come up in the net: it is like trying to solve a fascinating logic puzzle by fitting the theory to the collections".

Roxy Zunckel (middle) with colleagues onboard the Dr Fridtjof Nansen in March/April 2018, sorting the catch in the wet lab. © Mark J Gibbons	"The deck of the Nansen was covered by a new species of moon jelly" said jelly scientist Delphine Thibault. Image taken off the mouth of the Zambezi River, in March 2018. © Delphine Thibault

In order to broaden the capacity-base across the region and to advance the science and to improve understanding of possible fisheries impacts, a regional workshop is being developed to facilitate upcoming jellyfish research for the remaining period of the current phase of the EAF-Nansen Programme (2020-2021). During the sampling collections in 2017-2018, many of the African partner countries expressed an interest in improving the understanding of different aspects of jellyfish in their waters. With this in mind, the workshop is designed to equip interested regional scientists with the tools needed to conduct this type of research and give them an overview of the dataset and samples that have been collected as part of the EAF-Nansen Programme so far.

What's next?
Due to covid-19, the regional capacity-building workshop that was originally planned to take place in Senegal during the first half of 2020 had to be postponed. "When we have a new date, it is my hope that participating countries and interested institutions will allow staff to participate, especially young staff and students, because it will allow Africa to develop its own collaborative network for the future" said Professor Gibbons.

Another product coming up is an identification guide to jellyfish along the western seaboard of Africa. Professor Gibbons, who is supporting this activity, is enthusiastic in his support of this, as "for the first time, there will be a user-friendly guide to the region's jellyfish that can be used by fisheries scientists, school teachers and professors alike, drafted by a team of international experts".

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