[Coral-List] Centuries of reef protection

[Charles Birkeland]

I feel compelled to call attention to a paper that just came out with a
historical perspective of how the tradition of offshore fishing for tuna
rather than nearshore reef fishes may have enhanced the resilience of the
coral reefs in the Maldives (Yadav et al. 2019. King tuna: Indian Ocean
trade, offshore fishing, and coral reef resilience in the Maldives
archipelago. ICES Journal of Marine Science doi:10.1093/icesjms/fsz170).
Archaeological collections from the first to ninth centuries CE showed that
scombrids were a major food in the Maldives and historical records
indicated that tuna was a major component of international trade around the
Indian Ocean from the Maldives for perhaps a thousand years. It was
fortunate for the resilience of Maldive coral reefs and for the food
security and stable economy of a robust fishery for the people of the
Maldives over many centuries that their culture valued offshore fisheries
rather than reef fishes.

Unfortunately, the globalization of tourism has recently brought a large
influx of several times more people than the native population to the
Maldives and tourists often want to be served exotic reef fishes in
resorts. In contrast to pelagic fishes, reef fishes are a diverse array of
mostly small fishes that have relatively slow population turnover and are
vulnerable to overharvest. The authors of this article recommend that
resorts encourage the consumption of skipjack tuna rather than reef fishes,
building the attractiveness of pelagic fishes from the story of their
strong role in the tradition and culture of the people of Maldives.
Although the tuna have sustained fisheries in the Maldives for perhaps a
couple thousand years, the human population has grown and pollutants that
can accumulate in higher predators have increased to the point that Martin
Hall and Daniel Pauly have recommended focusing more on the smaller
pelagics for usual consumption, considering the larger pelagics as “luxury”
fishes for consumption on special occasions. Yadav et al. (2019) smartly
recommend skipjack, one of the smaller and probably the most sustainable of
the scombrids.

Restaurants in Hawaii switched from reef fishes to pelagic fishes on their
menus when tourism grew after WW II (Van Houton et al. 2013. Front Ecol
Environ 11: 289-290). The small bigeye scad is called “the most popular
fish in Hawaii” (Pacific) and I have been told the Kenchi Bigeye Scad
Seafood Restaurant is one of the most popular tourist restaurants in
Curaçao (Atlantic). I visited Hawaiian fish markets and talked to local
people. Although reef fishes are still in fish markets, the culture favors
pelagic fishes for poke, especially the small nearshore scads. As
recommended by Yadav et al. (2019), the use of tradition and culture in
marketing might be effective in diverting focus from reef fishes to
pelagics.

I worry when those that are trying to extol the value of coral reefs
emphasize that coral reef ecosystems are especially productive, and
therefore are important for fisheries production for the world. It is
certainly true that the gross primary productivity of coral reefs is among
the highest. Scott Nixon’s (1982. Oceanologica Acta SP: 357-371), based on
49 studies at 25 sites, found that the gross primary production of coral
reefs is about 10 times that of other marine systems. But he also found
that the potential surplus net production (fisheries yield) of coral reefs
was only about a tenth of that of pelagic fisheries. This is because of at
least two disparate factors.

First, the diverse, small, and long-lived coral-reef fishes are somewhat
like song birds in the very productive tropical rainforests. Reef fishes
can sustain protein for subsistence of small populations of local native
humans, but like song birds, their life-history traits are not appropriate
for feeding the world by commercial exploitation. It seems to me that the
great productivity of rainforests is celebrated for the biodiversity it
maintains rather than for producing songbirds for world consumption.

Second, although gross primary productivity is great on coral reefs, the
net productivity supporting the diverse biomass of consumers on undisturbed
coral reefs is also so great that nearly all is used, leaving very little
surplus net production. Hatcher (1997 in Life and Death of Coral Reefs)
documents < 1% of gross productivity is surplus; Kinsey (1983 in Barnes
[ed.] Perspectives on Coral Reefs) found that respiration of coral
communities approximately equals gross production; and Polovina’s data
(1984. Coral Reefs 3:1 – 11) indicate reefs may sometimes need some
external input when required net production is greater than gross
production. Of course, there has been a great biomass of coral-reef fishes
taken over the past decades to feed the world’s human population. I suspect
this has substantially reduced upper trophic levels on many reefs which
releases much of the net primary productivity as surplus, but do we really
want to advocate this?

I believe Yadav et al. (2019) is an important documentation of the food
security and stable economy of a robust pelagic fishery for the people of
the Maldives over many centuries and how this culture enhances the
resilience of coral reefs.