Shark feeding impact on corals research
Shark feeding is a controversial topic among conservationists, scientist and animal lovers. In some places it even created a bad impact on the animal and on the environment such as the famous whale shark feeding operations in Oslob, Philippines. But what if shark feeding and attracting sharks to the same reef every day could actually have a positive impact on the reef biodiversity and on the coral growth?
This is the question Juliette is currently studying in Kuata on Yakawe reef with the French lab CRIOBE and the University of EPHE.
How did we come with this questioning?
The “Awakening Shark Dive” at Yakawe Reef by Barefoot Kuata Resort in Fiji started eight years ago. When the activity started, the substrate of the 5 m flat reef from the shark dive site was mainly composed of sand, rubble and naked rocks with very few hard corals. Two years after starting the shark feeding activity, hard coral recruits (baby corals) were documented growing on the substrate alongside bigger colonies from different species. Today, in 2023, the reef is not only composed of a diversity of healthy hard coral adult colonies species and growth forms (table, columnar corals, digitate, encrusting, massive) offering habitat to several reef fishes but also of anemones, soft corals, octopuses, reef sharks and many more marine life. No other activity than the shark dive happened in this reef, meaning no restauration or coral planting was done.
What is interesting and caught our attention, is that exploration of other 5 m depth sites of Yakawe reef a few hundred meters away from the shark feeding site revealed a lower hard coral cover and colony sizes as well as a lower amount of fishes!
How can shark feeding have a positive impact on coral growth?
Sharks and fish release excrement in the water, in other words, they pee and poo. Corals are composed of tiny animals that use nutrients present in the water column to grow and survive. These excrements turn out to be nutrients for the corals to assimilate.
The daily presence of bull sharks at the shark dive site that releases extra nutrients in the water might then bring an extra push for corals’ growth than in other places of Yakawe. But sharks are not the only ones attracted by the feeding, a diversity of fishes also come and release nutrients, creating a healthy environment for the corals to grow.
How will I study it?
My work is now to implement a methodology and scientific protocol to understand the effect of the controversial shark provisioning activity on hard corals, and more particularly their growth. Since we arrive after the event, I will use a transplantation method to monitor and analyse the growth of corals transplants in three different sites (the shark dive and two control sites). I will also conduct underwater surveys of the substrate, fish population and invertebrate population to study the reef biodiversity. Hopefully, we manage to collect shark poo as well to analyse it and check its presence on top of the corals.
This outcome was not expected at all when this activity started, sharks were the only interest. It is quite interesting to evaluate and understand the mechanisms behind it!