Dive Pacific 171 Oct- Nov 2019

divenewzealand31206

unprecedented, spurred on by their

(I) venomous defence mechanism,

(II) lack of predatory pressures, (III)

ability to reproduce all year round

(though temperature and food

dependent), (IV) thrive in a variety

of habitats, (V) immunity to certain

fish pathogens, (VI) unique hunting

techniques and (VII) high rates of

survival despite long periods of

food scarcity (8, 26-33).

The invasion led to competition

with native fish (eg groupers)

seeking similar prey on the reef

(34). Researchers across certain

study sites found a 65% average

decline in the biomass of affected

native fish (26) The lionfish diet is

generalist by nature and known

to include many different species

including (35, 36) trumpetfish,

chromis, grouper, parrotfish,

snapper, pufferfish and squirrelfish.

Shrimp identified have

included mantis shrimp and

cleaner shrimp (37, 38). The diet

includes somewhat larger (adult)

species than the lionfish itself and

thus it is likely they are targeting

the juveniles which in turn may

alter the functioning of the food

web and thus the structure of coral

reef ecosystems (38).

Underwater visual censuses

suggest the densities of lionfish

in invaded areas are far greater

than in their natural habitats, up

to 400 fish per hectare (29)! That’s

up to 15× the density of their own

natural habitats!

Control options?

So what options are there to

decrease these invasions and

restore the natural populations?

Larger native fish may learn to

eat the lionfish while preyed-on

smaller native fish may come to

identify lionfish as a threat (39). A

more proactive approach has been

lionfish removal events such as

the Reef Environmental Education

Foundation’s (REEF’s) lionfish

derbies, and promoting lionfish

as a desirable fish to eat, such as

National Oceanic and Atmospheric

Administration’s (NOAA) “Eat

lionfish” campaign. These actions

also provide education about

handling and preparing a potentially

harmful fish which is in fact

completely safe to eat (34).

Developing a market for them

would be cost-effective for

controlling their populations,

alleviate over-exploited native

fish, relieve stress occurring on

the reefs, and provide an opportunity

for small scale commercial

fishing (27). Where a market for

lionfish has been explored it looks

promising, and may be a means to

control this invasive species.

www.dive-pacific.com 39

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