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April 2002

Article

 


The Coelacanth and the Comores: 
challenging the myth 

Robin Stobbs

A coelacanth filmed at Jesser Canyon by Trimix divers Pieter Venter and his team. Image copyright Pieter VenterAn over-arching quest in JLB Smith's life was the hunt for "for the home of the coelacanth". (Smith, 1956. p.51). A few quotes from Smith's book at the beginning of this article shows the progression of his notion that the Comores was home to the coelacanth. Since that time the idea that the Comores was home to the coelacanth has largely remained unchallenged until now. 

 

The "second" coelacanth known to science caught off the Comores. Pic courtesy R. Stobbs"Even though the discovery of this second coelacanth at the Comores (sic!), and the information gleaned by Hunt, appeared to pin-point that area as the home of those animals, it was clear that they could scarcely be abundant there. Although it was true that this Comoran coelacanth had been found in the type of environment which satisfied every condition I had deduced and predicted, I knew only too well that a coelacanth in any place does not necessarily mean that it is at home." …"At the same time, however, the evidence that coelacanths were caught occasionally indicated that if their true home was not at the Comores themselves, it would not be so far off this time, and there was all the more likelihood that this might be found more easily. The field of search would certainly be greatly narrowed down." (Smith, 1956. p. 193)

"Two in the same place. It must be their home, so that my enduring aim had been achieved, and most of my burden would now fall on the French." … "Now that one home of the coelacanth had been found…" (Smith, 1956. p. 221)

"… my heart was filled with fierce deep content, for I had shed the worry and responsibility of the coelacanth; one of the greatest ambitions of my life, to find the home of the coelacanth, had been fulfilled." (Smith, 1956. p. 226)

In writing this JLB Smith inadvertently created one of the largest myths to have blighted the 'coelacanth story'. From this time on almost every author writing about the coelacanth has referred to the Comoro Islands as the creature's home (see also Fricke, Leskovitz, etc). Without ever having proved to be the case, the Comoros were accepted by scientist and layman to be the home of the fish and the Comoros coelacanth population the 'core' population.

Balon et al, 1988. "……… a second coelacanth was caught, this time at its true home, the Comoro Islands."

Hissmann et al, 1988. "Three specimens caught at other locations ……… were probably strays from the Comores."

Bruton et al. 1992. "The Mozambique specimen could, however, be a stray that was carried from the Comoros on the south-flowing Mozambique current."

Schilewen et al. 1993. "This result (DNA sequence) strongly suggests that the Mozambique and Comorean (sic!) coelacanths belong to the same population. If a separate population of coelacanths exists at the East African coast, we would have expected substantially different fingerprint patterns……. Thus, mitochondrial as well as nuclear markers indicate that the Mozambique coelacanth originated in the Comorean population. An alternative explanation would be that there is an African coastal population in continuous genetic contact with the Comores. But this seems very unlikely."

Thomson (1991) examined the question critically, and in detail, yet still arrived at the conclusion that "the living coelacanth may well be a true relict species, existing in any numbers at all only on the Comores, but that if it does exist elsewhere, it would be in the form of stragglers from Comoran populations ….."

Bruton, 1989. "Fricke and Plante (1988) have predicted that further coelacanth populations will not be found in the western Indian Ocean as no suitable habitats exist other than in the Comoros, but I am more hopeful."

Leskovitz, in his website wrote, "Coelacanths are appearing where least expected! In September 2001, a fisherman caught a coelacanth at Malindi, Kenya. The fish was then brought to Mombasa. This is the first confirmed find north of the Comoros Islands, and is not easily explained by ocean currents." The presumption is that the fish was probably a resident but the author is very wrong in assuming that the north-flowing Somali Current could not have transported a coelacanth to Kenya from further south - even the Comoros.

Others were more positive. Erdmann (in Weinberg, 1999) is quoted as saying, "it is conceivable that there are more coelacanths, in different locations across the globe. It seems highly unlikely that the living coelacanth exists only in two small, highly disjunct populations."

But, this is all an accident of history - and a caution to scientists: beware of jumping to conclusions based on only a few facts.

For almost 40 years following the capture of the 1952 Domoni fish, popularly known as the "second coelacanth", all known coelacanths were caught off the Comoro Islands of Grand Comoro and Anjouan and it looked indeed as though it was only off these islands that the living coelacanth, Latimeria chalumnae, was to be found.

Click on map below to see confirmed and unconfirmed coelacanth localities off African coast.

Enter here to see the full map showing coelacanth localities. Map by Robin Stobbs.But, that was until a large specimen was netted by a prawn trawler off Pebane in central Mozambique in 1991; before one was caught up in a deep-set gill net near Toliara in Madagascar (with three further specimens subsequently coming from the same locality); before a number of coelacanths were seen by Trimix divers off Sodwana in northern KwaZulu-Natal in 2000 and 2001; before another specimen was netted in a trawl net off Malindi in 2001 (and before two specimens of a probably different species, Latimeria menadoensis, were caught 10 000 kilometres away in northern Sulawesi in 1997 and 1998).

 

It had long been suspected that the 1938 East London fish (popularly, but incorrectly, named the 'first coelacanth') was a stray brought down on the Mozambique Current, and indeed all these other WIO coelacanths could have been distributed in this manner but surely all these western Indian Ocean (WIO) specimens were not simple strays from the Comoros. DNA fingerprint determinations made on some of these fish showed a remarkable homogenicity and it was immediately thought that this was proof enough that they were strays from the Comoros 'core' population. The picture that is touted is one of a diminishing and endangered Comoros coelacanth population shedding unfortunate individuals who are unlucky enough to be detached from their island home and carried around by ocean currents eventually to be deposited elsewhere where they run the risk of capture in trawl nets or deep-set shark gillnets.

Could this be the true picture?

I think not - and for a number of reasons I believe this is all due to an unfortunate series of historical events and a patent disregard by a number of scientists for some important facts.

1. Following Smith's pronouncement that the Comoro Islands were the true home of the living coelacanth all scientific endeavour and research has been directed at these islands and at their coelacanth population in the mistaken belief that this was the only population group. It was inevitable therefore that nobody was looking elsewhere.

2. Only on the Comoro Islands of Grand Comoro and Anjouan, and nowhere else in the Indian Ocean, is the technique of deepwater nighttime handline fishing practiced. Known to the Comorans as mazé this form of fishing was developed to 'target' (in as much as one can target a fish species) the oilfish, Ruvettus pretiosus, known to the Comorans as nessa. Living within a similar depth preference and competing for the same prey species, nessa and gombessa (coelacanth in the Comoran patois) are caught by artisanal fishermen; the former by design, the latter by accident. Since it is mazé fishing that is commonly responsible for the occasional and accidental gombessa catch and since this form of fishing is not practiced elsewhere it is inevitable that coelacanth catch records from the Comoros far outnumber any other locality.

3. Coelacanths are believed to have been extinct for some 60 to 70 million years; Latimeria's closest known fossil relatives, Macropoma from Upper Cretaceous chalks in England and Megalocoelacanthus from the Upper Cretaceous outcrops of central Alabama and Georgia states in the USA both died out some 75 million years ago. The islands of the Comoros are only 0.13 to 5.4 million years old (Grand Comoro and Mayotte, with Anjouan and Moheli 3.5 and 2.75 million years respectively) (Emeric & Duncan, 1982, in Forey 1998) so one is left with the question, "What were coelacanths doing during the 65 million years it took for the volcanoes forming the Comoros to reach the ocean surface?" It is clear that they had to have been living elsewhere. Two pieces of ancient Gondwanaland, Madagascar and the African continent seem the most likely regions for our ancestral coelacanth habitats. Surrounding Madagascar and off the African east coast are ocean currents that might easily explain a widespread distribution throughout the entire WIO with the possible exception of the Mascarene Islands and the Seychelles and the islands to the east of Madagascar.

4. A collection of anecdotal accounts of coelacanths that were observed or caught, and which cannot be verified though every aspect of the accounts points to their authenticity, shows that Latimeria, though possibly nowhere abundant, is probably widely distributed throughout the WIO (see Fig.1).

References on the topic:

Albert, J., 2001. Pers com.

Balon, E.K., M.N. Bruton & H. Fricke, 1988. A fiftieth anniversary reflection on the living coelacanth, Latimeria chalumnae: some new interpretations of its natural history and conservation status. Environmental Biology of Fishes, 23(4): 241-279.

Bruton, M.N., 1989. The living coelacanth fifty years later. Transactions of the Royal Society of South Africa. 47(1): 19-28

Bruton, M.N., A.J.P. Cabral & H. Fricke. 1992. First capture of a coelacanth, Latimeria chalumnae (Pisces, Latimeriidae), off Mozambique. South African Journal of Science 88:225-227, April 1992.

Forey, P., 1998. History of the coelacanth fishes. Chapman and Hall, London.

Hissmann, K., H. Fricke & J. Schauer, 1998. Population monitoring of the coelacanth (Latimeria chalumnae). Conservation Biology, 12(4): 759-765.

Leskovitz, F., 2002. http://members.tripod.com/glenthorne/coelacanth.html

Schilewen, U., H. Fricke, M. Scharti, J.T. Epplen and S. Pääbo. 1993. Which home for coelacanth? Nature 363: 405, 3 June 1993.

Smith, JLB., 1956. Old Fourlegs. Longmans, Green, Readers Union edition. London 1957

Smith, JLB., 1956. The Search beneath the Sea. Henry Holt and Co., New York.

Thomson, K.S., 1991. Living fossil; the story of the coelacanth. W.W. Norton & Co., New York.

Weinberg, S., 1999. A fish caught in time; the search for the coelacanth. Fourth Estate, London.

These being just a selection of the many references to the 'home' question.







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