- Chantel Elston
Sharks as an important conservation tool in South Africa
In South Africa we are incredibly lucky to have a rich diversity of life in our oceans – from the cold-water fishery species on the West Coast (for e.g. the red roman and the west coast rock lobster) to the warm-water coral reefs on on the East Coast. Unfortunately, this marine biodiversity is threatened by a number of human-induced impacts, not the least of which is the fishing industry. However, especially in South Africa, we have limited resources to put towards the management and conservation of our marine world. This is where the concept of ‘umbrella’ or ‘flagship’ species may help.
An umbrella species is one that is chosen to make conservation-related decisions because by protecting this one species, you can indirectly protect many other species that co-occur with it. For example, by protecting the habitat that the Amur tiger in Russia relies upon, you also protect the deer and boar that occur in the same area. The advantage is that you only have to have scientific knowledge on the chosen umbrella species, instead of having to study all the species present. However, the caveat is that the occurrence of your umbrella species needs to be related with the occurrence of the other important species (i.e. where your umbrella species lives, so do the other species you are hoping to inadvertently protect).
On the other side of the coin, a flagship species is one that is culturally important and can be used to raise awareness and funds for conservation efforts – think along the lines of the giant panda (a cute, cuddly animal that the world loves and wants to conserve). A species can potentially serve as both an umbrella and a flagship species, if it is culturally and ecologically relevant.
Enter the chondrichthyans of South Africa – our sharks, rays and skates. These are charismatic species (for e.g. the infamous great white shark) and they are abundant across our coastline. If we could show that these chondrichthyans often occur with other species of conservation importance, then we have a winner! An umbrella – flagship species complex to assist in the conservation of our entire South African marine realm!
A new study by Geoffrey Osgood and co-authors sought to do exactly this. They used underwater video footage that they collected in two marine protected areas around Hermanus and Betty’s Bay to see if chondricthyan species commonly occurred with other important species (specifically fish and crustaceans that are commonly caught by commercial and recreational fisheries).
They encountered a total of 18 chondrichthyan species, ranging from small catsharks (e.g. the puffadder shyshark), to large sharks (e.g. bronze whalers and gully sharks), and even some ray species (e.g. the short-tail stingray). They found that, specifically for the catsharks and large sharks, if the abundance of these species increased, then so did the abundance of other important fish and crustacean species. Two species stood out remarkably, the dark shyshark and the broadnose sevengill shark, as they showed the strongest relationships with other fish and crustaceans. Additionally, the puffadder shyshark was connected to the highest number of other species, also highlighting its importance.
This research showed that chondrichthyans, especially the dark and puffadder shysharks and the broadnose sevengill shark, show strong potential as an umbrella species-complex in South Africa. That means, if we protect the habitat that these species rely upon, then we are likely to provide protection for a host of other important marine species, and we can use this information to concentrate our limited resources for conservation efforts.
Reference: Osgood, G. J., McCord, M. E., & Baum, J. K. (2020). Chondrichthyans as an umbrella species-complex for conserving South African biodiversity. African Journal of Marine Science, 42(1), 81-93.