Groupers

—Paul Hoetjes—

When people talk about coral reefs, fishermen tend to shrug their shoulders and complain about snagged lines and torn nets. But when you talk about groupers, they suddenly sit up and pay attention. Groupers are among the economically most important fishes of the Coral Reef, because of their popularity as food. Yet without the Coral Reef there would probably be no groupers. Here on Curacao this is a moot point since the groupers are already practically gone while we still have coral reefs that belong to the most varied and best developed of the Caribbean. So where did the groupers go?

Before I try to answer that, let’s first examine the groupers as a group. To start with their English common name "Grouper", this apparently comes from the Tahitian name "Garupa". In Spanish groupers are generally known as "Meros" or "Cunas". Groupers belong to the family of Seabasses or Serranidae, which includes a large number of more or less similarly built fishes that, however, vary greatly in size, ranging from a two inch Fairy Basslet to the huge eight foot Jewfish. Here we will only focus on the groupers, which are generally robust, large mouthed, predatory fishes, often with a projecting lower jaw that leaves them with a pugnacious, ill tempered look.

14 Species

Around Curacao we can expect to encounter up to 14 different species of grouper, though most of them only very rarely. The smaller the species, the more common it still is. The Graysby (Epinephelus cruentatus) and the Coney (E. fulvus) known locally as "Purunchi" and "Purunchi Pretu" respectively—"Purunchi" meaning freckle—do not grow much bigger than about 30cm and are still quite common. Another similar-sized grouper is the Mutton Hamlet. It is quite common, but few people have ever seen it, since it is almost exclusively found off the North Coast where it hides among the ubiquitous sargassum seaweed. The Rock Hind (E. adscensionis) and the Red Hind (E. guttatus), locally known as "Gatu" and "Gatu Korá", reach twice the size of the Purunchis and are also at least twice as rare, though they are still regularly seen and in shallow water.

Bigger is Rarer

All other groupers around our island are rare to very rare and can reach sizes of 80-120cm except of course for the very large and very rare Jewfish that can reach a size of 250cm. Most likely to be seen occasionally (but almost never at a big size) are the Nassau Grouper (E. striatus), Yellowmouth Grouper (Mycter-o-perca interstitialis), Tiger Grouper (M. tigris), Yellowmouth Grouper (M. venenosa), Comb Grouper (M. rubra) and Black Grouper (M. bonaci). The Red Grouper (E. morio), Marbled Grouper (E. inermis) and Jewfish (E. itajara) are known to occur around Curacao, but a sighting is about as rare as seeing a whale-shark: it happens, but you better remember it for the rest of your life since it is not likely to happen to you again. Other species of grouper have as yet never been reported from around Curacao.

Floating Eggs

Groupers are typical coral reef fishes, in that they need the numerous crevices, holes and caves provided by reefs, especially when they are young. They find protection there, and food in the form of the many small animals that share the protection of the labyrinth of the reef. Groupers lay eggs that float to the surface after being fertilized by the sperm released by the male in the water column during mating. The tiny grouper larvae that hatch from these eggs float in the ocean for a period of time, at the mercy of the ocean currents. They then metamorphose into actual little groupers that, when they encounter the right environment at the right moment, swim down to the bottom and hide between the corals or seagrasses. Apparently the larval groupers can cover quite some distance, because first year juvenile groupers have been found hundreds of miles north of where adult groupers occur. These juveniles probably survive in the warmer summer months and then die when the temperature drops.

Sex Change

Adult groupers have a very peculiar (to us) life cycle. When they reach sexual maturity they are female. They mate and produce eggs. After a number of years, when they have reached a certain age or size (or maybe when they finally decide that they have had it with this female thing), they change sex and become male. (This is a one-time only transition, they can not reconsider and change back anymore. Once male, they are stuck with it). The transition size is not clearly defined, in fact there is a broad overlap in male and female size, and so a female can be bigger than a male that has already gone through the sex change process. Apparently the trigger for the transition is not only size or age, but probably has something to do with population pressure and presence or absence of other males.

The advantage of such a life cycle is that the energy consuming task of producing eggs is left to the younger fishes "In the prime of their life" so to speak, while only large fish that have proven their ability to survive can change into males and fertilize the eggs. Thus, it is ensured that the genes of the survival proven fishes are conserved, enhancing the species’ gene pool. This mechanism, called sequential hermaphro-ditism, is fairly common among fishes and is also found in Parrotfishes and Wrasses, Anemonefishes, some Angelfishes and still other fishes in the Indian and Pacific Oceans.

The great disadvantage of course, in a world shared with humankind, lies in the fact that people preferably catch the biggest fishes and thus the males. This is especially serious in areas such as Curacao where spearfishing was allowed. There is no surer way to exterminate all the big groupers.

| Groupers | Scientific Research |