Given the Caribbean and Atlantic invasion by the
Indo-Pacific lionfish, dive operators generally consider
it a good idea to huntdown and kill this serious predator
to preserve indigenous creatures. However, what if
those repeated hunts are actually influencing lionfish
behavior, making the species harder to find and kill off?
Research published in the online journal PLOS One in
April suggests just that.
esearchers at Simon Fraser University in British
Columbia compared how lionfish act if they lived in an
area where spear-based culling had occurred to lionfish
living in areas where no such hunts had taken place. The
16 coral reef patches were all in the Bahamas. On eight
of those patches, divers had been culling the lionfish
with three-prong pole spears every three or six months
for two years. On culled reefs, a lower proportion of the
fish were active during the day, and they hid themselves
much more carefully as well. The investigators assigned
a "hiding score" to the fish based on certain behaviors;
half of the lionfish on culled reefs achieved the highest
such score, compared to only 19 percent of those on the
unculled reefs. This suggests, of course, that if a lionfish
survives a cull, it becomes more likely to survive the
next one as well. It is, in a sense, a very rapid form of
natural selection.
Of course, any animal hunted by humans presumably
might alter its behavior to avoid being killed.
However, this study does have implications for how
to control invasives. Culls sometimes set goals of a certain
percentage of the species, but if we intentionally
leave 30 percent of an animal, it may make it that much
harder to get back to 30 percent the next time we give it
a shot. This also backs up those invasive species-control
programs that aim for total annihilation. For example,
the leader of an attempt to kill off the invasive brown
rat in the sub-Antarctic Island of South Georgia said
last year that "killing 99.999 percent is a failure. If we
don't get every last one, we may as well not have gone
there in the first place."
With the lionfish, this study just adds fuel to the idea
that aiming for eradication is likely the best approach.
In one Bahamas study from 2012, an increase in lionfish
abundance coincided with a 65 percent drop in the total
biomass of the 42 types of fish that it eats. It is likely not
possible to completely eradicate the invasive lionfish
from the Atlantic at this point, but plans for individual
culls may have to consider marine life's ability to adapt
in order to keep this problem fish's population down.
"What Doesn't Kill You Makes You Wary? Effect of Repeated
Culling on the Behavior of an Invasive Predator," by IM Cote, ES
Darling, L Malpica-Cruz et al; PLOS One, 9 (4) e94248. DOI:
10.1371/journal.pone.0094248