By Nuri Max Steinmann.
Sea cucumbers are among the least appealing animals on this planet. They are not only called like a vegetable, they also look like one, so why even care? Besides their great variety of colours and sizes, their importance for marine ecosystems is well documented. But they have also gained a lot of interest for some other features, which do not seem so obvious.
Sea cucumbers are deposit feeders, which means they eat sand and filter the organic material. They function like “vacuum cleaners“, and contribute to the recycling of nutrients, such as ammonium. But they don’t just clean the seafloor, sea cucumbers also contribute to the process of overturning and reworking the sediment layers. That’s good for the sediment, because the exchange at the water-sediment interface leads to higher oxygen supply in deeper sediment layers, which supports the biodiversity of microorganisms.
That’s all well and good, but why would pay someone hundreds of dollars for a dried kilogram of sea cucumber? At the famous seafood markets in Hong Kong or even on Alibaba, the price of dried sea cucumber can range from a few 100$ up to $1000 per kilogram. That’s because sea cucumbers are listed among the most valuable products of the Chinese premium seafood industry, with the dried body wall sold as “bêche-de-mer” or “trepang”. With the growing demand, sea cucumber fisheries have been increasing and are now occurring globally in both tropical and temperate regions. Many sea cucumber species are often found in low-energy habitats and are highly immobile, making them easy to collect and very vulnerable to overexploitation. Therefore, populations of commercially valuable species have declined dramatically, and many regional fisheries have collapsed.
Driven by the ongoing exploitation of wild populations, the cultivation of valuable sea cucumbers species has gained the interest of big aquaculture companies around the world but has also become an important and viable livelihood activity for coastal communities in developing countries, especially in the tropics. The farming of sea cucumbers is thought to not only provide an economic value for local communities, but to also reduce the fishing pressure on wild populations.
A great example is the success story from Zanzibar. In 2011, sea cucumber farming was introduced and is now considered as one of the most promising aquaculture export products in Zanzibar. At the beginning outgrow farming was still depending on wild caught juveniles and therefore unsustainable. In response to this, a sea cucumber hatchery has been established as part of Zanzibar’s mariculture development programme, which is run by the government of Zanzibar in cooperation with the Food and Agriculture Organization of the United Nations (FAO). The main purpose of the hatchery is aiming to provide juvenile production for sea cucumber farming as well as for restocking purposes.
One of the sea cucumber farmers who is benefiting from this, is Haji. He became a sea cucumber farmer in 2013 and now owns four farms, which he is taking care of together with six friends. They hold a total of up to 10,000 sea cucumbers in all four farms, with a market price of 2,500 Tanzanian Shilling per individual (about 1 euro).
Haji is happy with farming sea cucumbers. They are easy to handle, do not require much extra work and provide him and his colleagues a good and stable income. Until recently, he had to use baby sea cucumbers from the wild, which he bought from other fishermen, to grow them in his farms. That was sometimes a problem, because there were not many wild sea cucumbers left and he couldn’t always get enough individuals. Now he can also get fingerlings from the hatchery instead, which helped him to make his business become more stable and sustainable.
A little bonus nerd knowledge to show off when hanging out with your peers
8 reasons why sea cucumbers are simply amazing:
- They have no brain and no heart
- They breath via their anus
- They provide a lovely shelter. Some fish decided to live inside their anus
- They can poop out they guts as a defensive response and just regrow them
- They are the “vacuum cleaners” of the oceans
- They can change sex if they feel like it
- Some species can survive if cut into 2-3 pieces – each piece will grow into a new animal
- They can survive extreme conditions by just shutting down their biological activity until it’s more comfortable again
To learn more about sea cucumbers, a few useful links:
National Geographic: https://www.nationalgeographic.com/animals/invertebrates/group/sea-cucumbers/
FAO, How sea cucumbers are boosting the bioeconomy in Zanzibar: http://www.fao.org/fao-stories/article/en/c/1247576/
Copyright of all pictures in the tet belong to Nuri Max Steinmann.
Copyright of the red sea cucumber picture belongs to Oliver Leyba.