The earliest fish were jawless a feature still retained by some of today’s aquatic vertebrates like the hagfish and lampreys Fish having true jaws the acanthodians did not evolve for another 40 to 50 million years and it is from them that the present-day fish have arisen with numerous extinctions along the way Among these extinctions are the acanthodians themselves which disappeared after about 150 million years Another group the antiarchs had a shorter history surviving for about 70 million years having first emerged 400 million years ago The fossil record is incomplete of course so some of our interpretations have to be based on partial information Nonetheless the record is sufficiently wide ranging and representative for some major conclusions to be drawn For instance we can say that bichirs family Polypteridae have been around for 135 million years or so Likewise lungfish families Ceratodontidae and Lepidosirenidae have long histories stretching back to Devonian times 400 to 350 million years Most famous of all these so-called living fossils is the coelacanth pp 8 9 the first genuine remains of which occur in Devonian rocks and the last in 70 million-year-old sediments After that time no more fossil coelacanths are found so the line was assumed to have become 1 extinct Then in 1938 a living specimen was raised by fishermen off the Comoro Islands in the Indian Ocean Others have followed over the years leading to increased knowledge of this fascinating fish which appears to have undergone no major changes when compared to the youngest of the known fossils Why are Fish at Risk Few places on our planet appear to be free of human influences although sometimes they do not cause problems for the continued survival of a particular species In fact there are instances of both animals and plants that actually benefit from such situations Sparrows and European blackbirds are just two of many species that might not be as numerous as they are today if they did not live in close proximity to humans and human-influenced environments Broadly speaking though human influences often place species under greater pressure than they would normally experience Fish also have to cope with the consequences of habitat alteration as other animals do In the case of migratory species like salmon sturgeon pp 12 13 and others dams reservoirs river channelization and other changes can present insurmountable hurdles as the fish try to reach their spawning grounds upriver In the worst cases local populations or even species can be driven to extinction as a result Hunters prey and scavengers existed in prehistoric times just as they do today Here a large Glyptolepis 1 hunts a shoal of small Paleospondylis 2 while two Pterichthyodes 3 scavenge along the bottom 6 2 3
WHAT IS A FISH cichlids pp 16 17 gold sawfin goodeid and Lake Wanam rainbowfish Overfishing is also a major factor affecting abundance with some species being placed under such survival pressures that only drastic action including but not restricted to total or partial bans can hope to save them from extinction Species as diverse as tuna cod and shark all fall within this category but there are many many more The Situation Today The IUCN 2000 Red List concluded that there was evidence of an extremely serious deterioration especially in the status of riverine species An increase of 18 species on the Red List from 1996 to 2000 did not at first sight appear too drastic see table However betwen 2000 and 2010 there was a dramatic increase in the number of endangered species in part because of the problems faced by freshwater fish More than 35 percent of North American freshwater species for example are now threatened And the IUCN’s forecast in 2000 that It is highly probable that increased attention to these species by the Species Survival Commission over the next three years will confirm a worldwide global crisis in freshwater fish was confirmed Even allowing for the possibility that some of the increases may be the result of more accurate recording than in the past we are still facing a grave situation we need to do all that we can to reverse the trend Numbers of Threatened Species of Fish Critically Endangered Endangered Vulnerable TOTAL 1996 157 134 443 734 2000 156 144 452 752 2010 376 400 1,075 1,851 From 2000 to 2010 see above there was an increase of 1,099 threatened species of fish 7 Rainbow trout killed by an oil seepage into the water Pollution of the waters poses serious threats to the survival of fish species around the world In many other instances it is not changes in the quality of the water or the migratory routes that pose the greatest risks but the restricted distribution of the species concerned When this restriction is extreme as is the case for the devil’s hole pupfish and bandula barb pp 30 31 for instance the threat is so serious that stringent measures are required to ensure the survival of the species Ironically one of the biggest threats that some fish have to face is posed by other fish There are countless instances of fish being introduced into habitats outside their own natural range It may be done to cater to a demand for sport or angling species as in the case of trout or as a means of providing a new source of animal protein for local communities as in the case of the Nile perch introduction into Lake Victoria or even to combat disease as in the case of the mosquito fish which has been widely introduced for biological control of malarial mosquitoes In many of these cases the introduced exotic species places the native species under threat It could be through direct predation on adults or young or eggs competition for space competition for food or spawning sites or quite simply through having a higher reproductive rate than the endemic species There are several examples of fish that face such situations such as mojarra caracolera Lake Victoria
EX CR EN EW Coelacanth Latimeria chalumnae Until the late 1930s it was thought that the coelacanth had been extinct for 70 million years Closely related to the ancestors of land vertebrates and so called living fossils the coelacanths alive today are primitive deep sea bony fish The name refers to the fish’s hollow fin spines the Greek koilos means hollow and akantha means spine VU NT LC O in 1938 a fishing boat was trawling at a depth of about 240 feet 70 m off the coast of South Africa near Port Elizabeth when the crew spotted an unusual fish in the catch none of them had ever seen one like it before On returning to port they informed Marjorie Courtenay Latimer curator of the local natural history museum She could not identify it Marjorie Courtenay Latimer measured examined and photographed the fish and then had it stuffed She also wrote to James Leonard Brierly Smith an ichthyologist fish specialist in Grahamstown in South Africa enclosing a sketch DATA PANEL Breeding Livebearer gives birth to living young Up to 20 large eggs each measuring 3 5 in 9 cm in diameter and weighing 10 6 12 4 oz 300 350 g are released from ovaries into oviduct Developing embryos reach a length of at least 12 in 30 cm before birth Life span at least 11 years Related endangered species Sulawesi coelacanth VU Status IUCN CR Coelacanth Latimeria chalumnae Family Latimeriidae World population Unknown Distribution Comoro Islands Indian Ocean between Madagascar and southeastern Africa Sulawesi coelacanth Latimeria menadoensis lives only in oceans around Sulawesi Indonesia Habitat Cold waters in deep ocean at 240 ft 70 m Size Length up to 5 9 ft 1 8 m Weight 210 lb 95 kg Form Primitive fish with limblike pectoral fins Bluish base color with light pinkish white patches Diet Fish 8 The fish measured about 5 feet 1 5 m in length and was mauvish blue with iridescent silver markings Its odd looking fins were perhaps its most unusual feature The caudal tail fin had an extra portion sticking out at the end like an additional fin lobe There were also two dorsal back fins instead of one The paired fins were even more strange in that they had stems that looked like limbs with fin rays fanning out at the edges Fossil Record The rest as they say is history The fish was a coelacanth a primitive marine bony fish of the genus Latimeria Fish of the genus Coelacanthus had been found as fossils in rocks from the end of the Permian period 225 million years ago and at the end of the Jurassic period 136 million years ago The coelacanths were believed to have become extinct about 70 million years ago so the find was a rare creature a living fossil As such it provoked much public interest The modern coelacanth was larger than most fossil fish and had a powerful body Reports of other catches of coelacanths have been recorded in more recent years However none of the TANZANIA COMOROS MADAGASCAR MOZAMBIQUE catches has occurred in South Africa until the latest finds in Sodurana Bay Until the late 1990s the 200 or so finds all came from the waters around Comoros a small group of islands between southeastern Africa and Madagascar in the Indian Ocean However in September 1997 Mark
COELACANTH Erdman a scientist visiting the Indonesian island of Sulawesi saw an unusual looking fish being taken into the local market he immediately identified it as a coelacanth In 1998 a further specimen was found near Sulawesi questioning the long held belief that coelacanths inhabited a limited range in the Indian Ocean Sulawesi is separated from the Comoro Islands by more than 6,000 miles 10,000 km The Sulawesi coelacanths are similar apart from their coloration they are brown with golden flecks Analysis of genetic structures however indicated that the fish is a separate species with a population thought to be fewer than 10,000 mature adults Keeping the Past Alive Although it is not possible to gauge exactly how many coelacanths there are there is no doubt that they are very rare In recognition of its rarity CITES has listed the coelacanth under Appendix I thus making trade in the fish illegal Another protective measure involves the safe release of any specimens accidentally caught by fishermen The coelacanth favors cold waters at depths of about 240 feet 70 m A deep release kit first suggested by Raymond Walner a visitor to one of the coelacanth websites allows specimens to be lowered rapidly in a sack to a depth where the water is sufficiently cold and where the fish can release itself safely So far the method has proved to be the most effective way of returning coelacanths to the wild Coelacanths found today have changed little from their ancestors although they are larger than most fossil fish They have powerful bodies and limblike fins which they use to move themselves around on the sea bottom when they are looking for prey 9
