The world's rarest fish Part One

There is a subtle clue in the title to this article. Although it would be both interesting and informative to write an article on the world's six rarest fish, it would sadly be impossible. First of all, the figures are just not available. Unlike land mammals, for example, where detailed surveys have been done, and it is possible to say - for example - that the rarest large land animal in the world is the Javan rhinoceros with only about 50 specimens still living on the island of Java. Even in this case for figures are not certain.

There are an unknown number of these animals living on mainland Indo-China. An entire population was discovered in Vietnam about 15 years ago and it is tempting to theorise that the species may not be as endangered as the experts think. Sadly, however, these are merely pipe dreams, and even if there are another 50 specimens in Vietnam, Laos, Malaya and Burma this does not do much to increase the chances for the prognosis of the species in the long term. However, all is not lost. At the beginning of the 20th century it was believed to that there were only about 25 white rhinos left. A hundred years later, and they are the most common rhinoceros species in the world.

With fish, however, the situation is even more uncertain. Many of the rarest fish in the world owe their scarcity to a very small and often fragmented habitat. Therefore, it pains us as journalists to have to admit that the five fishes described in this article are almost certainly not the six rarest fishes in the world. However, they are all critically endangered, and each of them is a fascinating creature, which it would be sad to think it might soon be gone for good.

THE MARYLAND DARTER (Etheostoma sellare)

Surprisingly enough if you want to look for one of the world's rarest fish you don't have to travel to the depths of the ocean or air to some uncharted territory at the ends of the Earth. This little fish lives in a clear, cool creek in Harford County, Maryland, just a few miles from where 1-95 crosses the Susquehanna River. The fish has never been found anywhere else.

It was first discovered in 1912 by two biologists collecting fish in Swan Creek, a fast-flowing stream near Havre de Grace. They named the fish and published their discovery in a scientific journal, whereupon the world promptly forgot all about it. Fifty years later in 1962, a group of graduate students found one near Swan Creek in Gasheys Run. Three years a healthy population was found in Deer Creek, which is where all subsequent records have been made.

The main reason that this fish is so rare is because of its extremely specialised habitat requirements - the riffles (fast-flowing areas, before the flatlands) in that part of a stream where the water tumbles out of the hills onto the relatively flat coastal plain. At one time this tiny species may well have been common in many of the streams that flow into the Chesapeake Bay from the Western Shore, but we are unlikely ever to know because so much of that area has become heavily industrialised and the water table polluted.

The good news is that the Maryland Darter is an "Indicator Organism," a species whose presence or absence indicates the relative health of a natural ecosystem. The continued existence of the Maryland Darter in Deer Creek indicates that this watercourse is still relatively healthy and clean.

THE BALLINA ANGEL-FISH (Chaetodontoplus ballinae )

This beautiful, small angelfish is widely believed to be one of the rarest fish in a the world. However, the question remains - is it indeed rare, or just very little known?

The type specimen was originally caught and described by Gilbert Whitley in 1959, based on a single specimen collected off Ballina in northern New South Wales. Like the Maryland Darter, however, it was 20 years before Ken Graham of the NSW Fisheries Department caught the second specimen - a single animal, again in the waters off NSW. He took a photo of the fresh specimen and sent the photo and the preserved fish to the Australian Museum. Until this year, these were the only two records of this rare fish in the world. However, in May 2003 Mark Norman of the Victoria Museum in Australia led a team on a three-week expedition, which made a number of remarkable new discoveries. These included a new species of spiked dogfish and in one short trawl at around 90m deep near Ball’s Pyramid, - three specimens of the Ballina Angelfish, leading Norman to announce (in an amazingly bullish manner) that "it appears that this species may be quite abundant in this special region."

Again, it seemed that the rarity of this beautiful species is mainly due to its incredibly restricted habitat - the cold, deeper water around coral and rocky reefs in depths between 25-123m. Near Balls Pyramid it was associated with a large, rocky pinnacle encrusted with hard corals. They both have hair main classes threat to its survival has been cited as illegal collecting by the marine aquarium fish trade, where this species would attract high prices due to its rarity and difficulty in collecting.

Maloti Minnow Pseudobarbus quathlambae

The Maloti Minnow is a small fish from the highlands of Lesotho in Africa. Like the Maryland Darter, it can only exist in a high quality environment with very highly oxygenated water. It would actually have been quite a common little fish, but it has been classified a critically endangered fish according to the International Union for the Conservation of Nature and Natural Resources. This is because a large portion of its environment will be seriously impacted by the imminent implementation of the Lesotho Highlands Water Project.

Probably the greatest threat to the continuation of the species will come from the Mohale dam. The ultimate opening of Mohale-Katse tunnel threatens the very existence of the species by exposing it to greater possibility as prey to bigger fish, most notably which have been introduced as both a food and a sporting resource. It is also feared that the increased tourism to the region which is planned by the government of the country will perforce bring with it an intolerable level of environmental degradation which will, sadly, reduce the quality of the water in the region so much that the fish will die out.

Luckily, however, all is not lost for this tiny minnow like species. There are other suitable catchments outside Mohale where the small fish could be translocated as part of the LHDA mitigation and conservation plan. The LHDA will ensure that the translocation is not effected in areas where trout is present. the Government of the country should be commended for such a far-sighted action. it is not often that Third World governments pay much attention to the future of a such a small and seemingly insignificant species were charred - after all - of little or no commercial or touristic value. Let's hope that the conservation programme which has been set into action will spur other governments in the region to do likewise.

It is hard to choose only a small number of species from the dozens that are critically endangered to, or feared to be extinct. In the next article we shall be bring you more stories - some good, and some bad - from around the world telling how some of the world's most unique creatures may not survive beyond our own lifetimes.