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MESOPHOTIC CORAL ECOSYSTEMS – A LIFEBOAT FOR CORAL REEFS?
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The international marine aquarium trade involves the
collection, breeding and supply of many shallow and
mesophotic reef fish, corals and other invertebrates for home
and public aquaria. Marine life in the trade is supplied from
40–45 countries (Rhyne et al. 2012). Estimates suggest that
approximately 150 hard coral species and 1,500 fish species
(across 50 families) are actively targeted by the marine
aquarium trade (Wabnitz et al. 2003). Recent research has
highlighted the role of the Philippines and Indonesia as the
dominant global exporters, responsible for 55 per cent and 31
per cent, respectively, of all live fish imports into the United
States for 2005 (Rhyne et al. 2012).
The United States imported approximately 11million fish during
the year 2004–2005 (Rhyne et al. 2012), and the Europeanmarket
is of a similar size (Wood 2001). This suggests a global trade
of over 22 million fish annually. Currently, most monitoring
of the marine aquarium trade is based on the Convention on
International Trade in Endangered Species (CITES) permits or
packing lists for international shipping of live fish.
It is unclear what proportion of the traded marine life
is collected from MCEs. However, there is trade in
mesophotic reef fish species with countries such as Japan,
where there is an enthusiastic market for ‘rare’ mesophotic
fish species. Traded mesophotic species include anthias
(Subfamily: Anthiinae; Figure 6.10), dottybacks (Family:
Pseudochromidae), butterflyfish (Family: Chaetodontidae),
wrasse (Family: Labridae) and pygmy angelfish (Genus:
Centropyge). In particular, within the pygmy angelfish, the
Peppermint angelfish (
Centropyge boylei
) and the Narcosis
angelfish (
Centropyge narcosis
) are highly prized (see case
study). Mesophotic fish are commonly labelled as ‘rare’ by
the marine aquarium trade, but this is likely to reflect their
limited supply due to the difficulties of collection rather than
true ecological rarity. With current collection pressure quite
dispersed over large reef areas, it is unlikely that the marine
aquarium trade is having a large impact at mesophotic
depths. However, populations of many mesophotic reef fish
species lack quantitative assessments, making sustainable
collection quotas hard to set.
As many mesophotic fish species in the aquarium trade have
gas-filled swim bladders which expand and burst if fish are
brought too rapidly to the surface (Munday et al. 2015), careful
planning is required to bring them to the surface without injury.
Traditionally, collectors have carefully punctured the swim
bladder of the fish using a needle on ascent, though this may
result in increased infection risk later. Many collectors still use
‘needling’ to bring collected fish to the surface (Figure 6.11),
although, increasingly collectors are using decompression
stops to allow fish time for gas to move out of the swim bladder
during ascent. Work on Yellow Tang (
Zebrasoma flavescens
)
on Hawaiian shallow reefs found that ‘needling’ to vent excess
gas from the swim bladder reduced immediate mortality post-
dive, but led to elevated serum cortisol (a proxy for fish stress),
whereas the addition of decompression stops led to lower
increases in serum cortisol (Munday et al. 2015).
In terms of scleractinian corals, it is unlikely that many are
being collected from mesophotic depths, as most coral species
in high commercial demand are found in greatest abundance
on shallow reefs or reef slope environments less than 30 m
in depth. With increased availability of advanced diving
technologies, which allow access to greater depths, there could
be an increase in demand for mesophotic species in the future.
6.5.
Marine aquarium trade
Figure 6.10.
Anthias,
Pseudanthias bimaculatus
, collected at 50 m in the Maldives for the marine aquarium trade (photo ElizabethWood).