offers a good illustrative example to demonstrate the importance of larval pelagic (open sea) duration in a species’ distribution. The Banggai cardinalfish is naturally found in a small Indonesian island group just two-thirds the size of Connecticut.45 It features a stunning combination of black stripes on a white base color, with white-speckled black pelvic, anal, and caudal fins. Unlike the pajama cardinal, the Banggai has a unique approach to brooding. The male holds just forty to fifty large eggs in his mouth, significantly fewer than other cardinals that can brood thousands of much smaller eggs. He broods these for nineteen to twenty days before they hatch, when he retains them for an additional ten days in his mouth.46 During this extended period of paternal care, the young grow into well-developed, miniature versions of their parents.
Banggai cardinalfish. Lembeh Strait, Sulawesi, Indonesia.
I once spent a dive observing and photographing a brooding male, but was most intrigued by watching the inquisitive fry jostling for the best vantage point to watch me from inside their father’s mouth. Because of their advanced development, the Banggai skip the pelagic oceangoing stage of development, and, after gaining their freedom, immediately form a small school around a protective home such as a sea urchin, where they shelter among the long spines. The babies are then immediately committed to the reef; as a result the species hasn’t naturally spread beyond the confines of the Banggai Islands, which are surrounded by deep, unpassable water.
I have been privileged to see the striking Banggai cardinalfish on several occasions, but I have never been to the Banggai Islands. In the mid-1990s there was huge demand for these fish in the aquarium trade. They were heavily collected, and in 2000 a small group was discovered in Lembeh Strait, a popular diving location separating the northeast Indonesian islands of Lembeh and Sulawesi. These Banggai cardinalfish are believed to have escaped and naturalized from an aquarium trade consignment. In Lembeh Strait their numbers have since increased exponentially and their population is now abundant. Several years later, most likely released by enterprising scuba professionals, they appeared in northwest Bali, and, in 2017, the first individuals were taken and released near Ambon Island, a diving area in central Indonesia. Without their natural predators, the non-native Banggai’s populations have exploded, with potential impacts on native species. It is hard to know the long-term implications of this influx, but you don’t have to look hard to find examples of widespread devastation by other invasive organisms. Ironically, the natural populations of these fish in the Banggai Islands have continued to suffer; they have reportedly been reduced by 90 percent through removal for the aquarium trade, and have been listed as endangered and continue to decline in numbers.
Recently released juvenile Banggai cardinalfish shelter among the spines of an urchin. Lembeh Strait, Sulawesi, Indonesia.
The final major explanation for high biodiversity in the Coral Triangle is that the geographic ranges of many species from the Indian and Pacific Oceans overlap within the Asian archipelago, causing higher diversity where they coexist. While the true source of the Coral Triangle’s high diversity can possibly be attributed to a convergence of several factors, it mostly boils down to the huge variety of habitat types the islands offer. Varied habitats beget varied organisms.
In Our Hands
We know that the world’s highest marine biodiversity is in the Coral Triangle, but this wasn’t always the case. Major tectonic events over the past fifty million years have shifted the location of the hotspot at least three times over that period.47 Southwest Europe was once the location of the world’s richest reefs. While natural processes like tectonic events can impact the survival of coral reefs and their inhabitants, human activity currently threatens to enact unprecedented changes on the ecosystems.
Male Banggai cardinalfish mouth brooding his fry. Lembeh Strait, Sulawesi, Indonesia.
Given its amazingly high biodiversity, the Coral Triangle’s conservation is a global priority. Even today dozens of new fishes, crustaceans, corals, and echinoderms are being discovered on the region’s coral reefs—each vital to the mechanics and well-being of their environment. New species can emerge in the most unexpected places. Some have been hiding in plain sight; others have offered only the briefest glimpses into their lives. We have so much more to learn. If we want to meet undiscovered organisms before we lose the chance forever, we must conserve reefs around the world.
26 Fredrik Moberg and Carl Folke, “Ecological Goods and Services of Coral Reef Ecosystems,” Ecological Economics 29, 2 (1999): 215–233.
27 Rebecca Fisher et al., “Species Richness on Coral Reefs and the Pursuit of Convergent Global Estimates,” Current Biology 25, 4 (2015): 500–505.
28 Alasdair D. McIntyre, ed., Life in the World’s Oceans: Diversity, Distribution and Abundance (Blackwell Publishing, 2010): 65–74.
29 Renema, Willem, ed., Biogeography, Time and Place: Distributions, Barriers and Islands 29 (Springer Science and Business Media, 2007): 117–178.
30 Gerald Allen, “Conservation Hotspots of Biodiversity and Endemism for Indo‐Pacific Coral Reef Fishes,” Aquatic Conservation: Marine and Freshwater Ecosystems 18, 5 (2008): 541–556.
31 J. Veron et al., “Delineating the Coral Triangle,” Galaxea, Journal of Coral Reef Studies 11, 2 (2009): 91–100.
32 A. Green and P. Mous, “Delineating the Coral Triangle, its Ecoregions and Functional Seascapes,” Version 5.0. TNC Coral Triangle Program Report 1, 08 (2008).
33 J. Veron et al., “Delineating the Coral Triangle,” Galaxea, Journal of Coral Reef Studies 11, 2 (2009): 91–100.
34 J. Veron et al., “Delineating the Coral Triangle,” Galaxea, Journal of Coral Reef Studies 11, 2 (2009): 91–100.
35 Hedley Grantham et al., “A Comparison of Zoning Analyses to Inform the Planning of a Marine Protected Area Network in Raja Ampat, Indonesia,” Marine Policy 38 (2013): 184–194.
36 Gerald Allen and Mark Erdmann, “Reef Fishes of the Bird’s Head Peninsula, West Papua, Indonesia,” Check List 5, 3 (2009): 587–628.
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