Page 40 - IB Sept-Oct 2020

Scaring Nemo

A pair of anemonefish hiding from divers in
tentacles of their host anemone. Picture by Evan
Brown, Auckland University of Technology,
taken during an AUT marine biology fieldtrip
for Pacific Island Ecosystems to the Solomon
Islands.

How do clownfish on coral reefs react to an encounter with humans underwater for few species of anemone,” Trnski explains.
encounters with humans? a limited time due to the small size and “In order to find a suitable host anemone,
Human intervention is putting marine localization of their anemone. the dusky anemonefish can benefit from
ecosystems under increasing pressure. On During their investigations in Vanuatu, fearlessly searching the reef - even if
coral reefs, rising water temperatures, the researchers focused on two species of this behaviour also makes them more
ocean acidification, pollution from plastic clownfish - the Clark’s anemonefish and susceptible to predators. But it is precisely
waste or overfishing threaten the organisms the dusky anemonefish. They wanted to this fearlessness that is also revealed by the
living there - be they fish, sea cucumbers know whether these species changed their fact that they do not flee from humans.
or corals. But how does the direct physical behavior when encountering humans.
presence of humans under water change the Lead author Lena Trnski snorkeled out Courage pays off
behaviour and ecology of animals on coral to the reefs off Efate island and videoed Their observations led the researchers to
reefs? the reactions of clownfish. To simulate conclude that in regions with a high level of
Researchers from AUT’s School of the presence of an observer, she hovered tourism, ‘courageous’ clownfish species such
Science and the Leibniz Centre for Tropical one to three meters above the anemone. as the dusky anemonefish could displace
Marine Research (ZMT) in Bremen However, she was not present during the more fearful species. “Species that retreat
studied the behaviour of anemone fish video recordings recorded as control for into their anemones for protection under
during encounters with humans off the comparison. She noted the behavior of each stress spend a lot of energy and time on this
coast of Vanuatu in the South Pacific. The fish in the anemone at 15-second intervals. A one escape behaviour and are therefore less
team, consisting of marine biologist Dr total of 60 behavioural events were recorded able to engage in foraging or reproduction,”
Armagan Sabetian (AUT), AUT marine for each anemone fish, both in Lena’s says Lilkendey. “Intrepid species have an
biology student Lena Trnski and fish presence and in her absence. advantage over them.”
ecologist Dr Julian Lilkendey (ZMT, came When confronted with human presence, “The resulting displacement process
to some surprising results which have been the two species showed very different would ultimately lead to a loss of species
published in the Journal of Fish Biology. behavioural patterns. “While Clark’s diversity,” Trnski adds.
Anemonefish, also known as clownfish, anemonefish were frightened by encounters “The ecological consequences of
are not only the cute protagonists in the with humans and often hid deep within behavioural changes caused by human
hit movie “Finding Nemo”, they are also the tentacles of the anemone, the dusky presence are still largely unexplored,” says
model organisms for behavioral studies anemonefish reacted less to the presence of Lilkendey. “We suspect that differences in
on fish. Clownfish live in symbiosis with a human,” reports study leader Dr. Julian the behaviour of individual animals could
sea anemones; the anemone offers the fish Lilkendey. “We actually expected that the have an impact on interactions between
protection from attackers in its tentacles dusky anemone fish would also hide from species, such as predator-prey relationships
while the clownfish defends it from invaders Lena or even attempt to chase her away, but or symbioses, which in turn affect
and provide it with nutrition through they usually did not let her disturb them. community structures and the functioning
its food remains and excrements. When Individuals were often up to a metre outside of the entire ecosystem”.
guarding their host anemone, the fish show the tentacles of their anemone.
easily distinguishable behaviours. The close “We suspect that dusky anemonefish Trnski, L., Sabetian, A., Lilkendey, J. (2020)
connection to their fixed-in-place anemone display a rather bolder behaviour in the Scaring Nemo – Contrasting effects of observer
presence on two anemonefish species. Journal of
makes clownfish particularly susceptible to presence of humans, as they are a highly
Fish Biology. https://onlinelibrary.wiley.com/doi/
human presence because they can only avoid specialised species that can only inhabit a full/10.1111/jfb.14492?af=R
40 Islands Business, September/October 2020