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Longfinned Eel
Geelbek-paling
Anguilla mossambica

Family : ANGUILLIDAE


Description

The breeding habits are similiar to those of the Madagascar Mottled Eel ( maromorata ), the two species are also often confused.

The colouring of this species is completely different from that of the other long finned eels in the Park, they are olive brown to dark grey depending of the water colouring of their habitat, the clearer the water - the darker the eel. Larger specimens will have a dark metallic bronze sometimes black colour with an iridescent silvery white belly.

The dorsal fin originates about halfway between the pectoral fins and the anus.

These are smaller eels with females reaching 5 kg in mass and males only 750 g.

Biology and Ecology

The larger specimens of this species live a sedentary life, seldomnly moving far from the crevices or hiding place covered by vegetation in a deep pool, younger specimens take up residence in tiny streams and smaller pools in seasonal rivers, provided there is enough shelter.water temperature is important as well as access to the Indian Ocean.

They are carniverous and feed on midge and mayfly larvae, dragonfly nymphs, worms, crabs frogs and fish, dead or alive.

In clear water, an eel may often be observed laying motionless with it's tail resting on the bottom and anterior end of the body raised in a slight curve. The fish remains quiescent except for the rythmic opening and closing of its mouth as it breathes by pumping water through it's gills. Should any prey pass within catching distance, it will instantly lunge wth blinding speed.

An eels life approaches it's end when sexual maturity is reached. Maturation is accomplished by changes in appearance, the colour changes to a more silvery and an increased eye size and gonads and in the final stage, atrophy ( deterioration ) of the digestive system. The migration then begins to the spawning area in the depths of the ocean, from which the adults never return.

Distribution

They are fairly common all along the east coast as far north as Kenya and have been found as far south as the Cape.

The Longfin Eel frequents all perennial and also many of the pools of the seasonal rivers of the Park and is the most common representive of this family

Threats

Water polution caused by domestic, agricultural, industrial and mining waste deposited into the feeder systems, changing the water to a low pH (acidic). Obstruction e.g. walls and weirs built in rivers without ladders prevent these species from moving upstream into suitable habitat.

Bulldog
Oopbek - snawelvis / Boelhondvis
Marcusennius macrolepidotus

Family : MORMORYDAE


Description
The colouring of this peculiar and interesting species varies in accordance with the type of habitat and the turbidity of the water.The usual colour is a dark chocolate brown or bronze and othe times golden/olive brown with dark brown mottling, the clearer the water - the darker the Bulldogfish.

They reach a maximum length of 300 mm. and reach a mass og 500 g.

The Bulldog is an elongated fish with a protruding chin, the dorsal and anal fins are set far back. The anal fin of the male is has a kink at the base while that of the female is concave.

Biology and Ecology
This is a shoaling species which frequents sheltered well-vegetated preferably running water.

They feed mainly at night on insects, crustaceans and algae from bottom sediments.

They breed mainly in summer, and annual migrations have been observed, propably for spawning purposes.

Distribution

It is widely distributed over all tropical parts and frequents the perennial rivers of the Park as well as a permanent pool in the seasonal Nwasontsontso river.

Threats

Water polution caused by domestic, agricultural, industrial and mining waste deposited into the feeder systems, changing the water to a low pH (acidic).

Churchill
Silwer snawelvis
Petrocphalus catostoma

Family : MORMORYDAE

Description

One of our smaller mormoryrid species. The body is deep and compressed without any protruberances on the chin. The head is markedly rounded, with the mouth ventral with one row of bicuspid teeth in each jaw, 12 to 16 in the upper and 16 to 20 in the lower. Nostrils are set close together. They are attractively coloured with a shining silvery flanks and bluish sheen on the back. With a lighter silvery or golden ventral surface.

The male is has a kink at the base of the anal fin which funnels the milt while spawning, while that of the female is straight.

They reach a maximum length of 150 mm.

Biology and Ecology

This ubiquitous species frequents the deeper rocky pools away from swift currents. They are well adapted to surviving in stagnant waters and are found in the vegetated pools of the seasonal rivers, where they occur in shoals.

They feed mainly on the bottom dwelling larvae of insects as well as free moving insects and small crustaceans.

They breed in rainy summer seasons.

Distribution

It is widely distributed over all tropical parts and frequents the pools of the perennial rivers of the Park.

Threats

Water polution caused by domestic, agricultural, industrial and mining waste deposited into the feeder systems, changing the water to a low pH (acidic).

Spot-tailed Robber
Kolstert-rower
Alestes imberi

Family : CHARACIDAE

Description

The body is compressed and reasonably deepened, with large scales and yellowish fins.Two series of sharp teeth in jaws. It has two characteristic black pathes, one behind the gill cover and the other on the caudal peduncle.

They reach a maximum length of 180 mm the females the bigger of the species.

This beautiful little fish is often mistaken for a juvenile Tigerfish - an easily distinguishing method is that it has a smaller mouth with tiny
teeth.

Biology and Ecology

Being the favourite prey of the Tiger Fish, they are seldomnly found in the deeper waters of the perennial rivers, however often frequent the shallows and backwashes of such rivers as well as the pools of the seasonal rivers where they often occur in larger numbers.

This rapacious shoaling fish with a wide spread diet feeds waterlily seeds, small fish and insects, filamentous algae, copepods and almost anything else available.

They reach sexual maturity at the length of 100 mm spawning takes place in summer and a 140 mm in length female has been found to produce 14 000 and larger females have produced up to 30 000 eggs. They are known to undertake spawning migrations, when they move out of the rivers when they overflow their banks.

Their flesh is very oily as that of all the members of the CHARACIDAE family.

Distribution

It is widely distributed over all tropical parts and inhabits all the perennial and many of the seasonal rivers of the Park.

Threats

Water polution caused by domestic, agricultural, industrial and mining waste deposited into the feeder systems, changing the water to a low pH (acidic)

Silver Robber
Silwer Rower.
Micralestes acutidens
Family : CHARACIDAE

Description

This small elongated robber has a silvery stripe on the body and usually a black tip to the dorsak fin. Caudal fins vary from yellow to orange and the other fins have a yellow/orange tinge.

They reach a maximum length of 80 mm the females the larger of the species.

This beautiful little fish is also often mistaken for a juvenile Tigerfish - an easily distinguishing method is that it has a smaller mouth with tiny
teeth and the silvery stripe on the body.

Biology and Ecology
These pugnacious and hardy little fish often occur in immense shoals in their chosen habitat, even seriously competing with other species for food and lebensraum.this little fish is also of the favourite prey of the Tiger Fish.

They frequent the clearer waters and avoid muddy areas of streams and dams.

This omnivorous shoaling fish feeds mainly on insects and other aquatic animal life.

They reach sexual maturity at the length of 60 to 70 mm, spawning takes place in summer after the rains They are known to undertake spawning migrations, when they move out of the rivers when they overflow their banks.

Their flesh is very oily as that of all the members of the CHARACIDAE family.

Distribution

It is widely distributed over all tropical parts and inhabits all the perennial and many of the seasonal rivers of the Park.

Threats

Water polution caused by domestic, agricultural, industrial and mining waste deposited into the feeder systems, changing the water to a low pH (acidic)

Three-Spot Barb
Driekol-ghielemientjie
Barbus trimaculatus

Famiily : CYPRINIDAE

Description

This elegant silvery or golden colouredfish, with three dark spots, minnow sized fish attains a length of 155 mm. The mouth is terminal with two pairs of well developed barbels. The dorsal, caudal and anal fins may develop into olive in colour. The supporting spine of the dorsal fin is smooth. The males turni into a beautiful bright golden colour in the breeding season.

Biology and Ecology

These handsome little fish prefer clear deep water with vegetation. They feed mainly on aquatic insects e.g. midges, mayflies and caddisflies in their midge stage of development. Flying ants and small land insects dropping into their habitat are also taken.

Sexual maturity is reached at the length of 75 mm. After the first rains in early summer, they move upstream and spawning takes place, a female may produce up to 8000 eggs.

This species is one of the main prey species of the larger predator fish and other predators of the waters of their habitat.

Distribution

Widespread throughout tropical Africa southwards towards the Umvoti and Orange Rivers.

They are found in all rivers and streams of the Kruger National Park.

Threats

Water polution caused by domestic, agricultural, industrial and mining waste deposited into the feeder systems, changing the water to a low pH (acidic)

Straightfin Barb
Lynvin / moeras-ghielemientjie
Barbus paludinosus

Famiily : CYPRINIDAE

Description

The characteristic feature of this little silvery to silverey grey and sometimes pale golden little fish is the vertical hind margin of the erect dorsal fin which has a long serrated bony spine, this minnow sized fish attains a length of 150 mm. This little fish has a thin lateral stripe.The mouth is terminal with two pairs of short barbels.

Biology and Ecology

These handsome little fish are found in marshes, and also in vegetation clad pools along streams as well as open waters, they prefer quiet waters..They feed mainly on aquatic insects e.g. midge larvae and small crustaceans. Flying ants and small land insects dropping into their habitat are also taken. They will also feed on plant material, particularly diatoms.

Sexual maturity is reached at the length of 50 mm. After the first rains in early summer, spawning takes place, a female may produce up to 2200 eggs.

Distribution

A common species from central and east Africa southwards to te lower Orange River and even southern Nata.

They are not common in the Kruger National Park but are found in the Olifants River.

Threats

Water polution caused by domestic, agricultural, industrial and mining waste deposited into the feeder systems, changing the water to a low pH (acidic)

Banded Orange-finned Barb
Gestreepte oranevlerk/vin-ghielemientjie
Barbus eutaenia

Famiily : CYPRINIDAE

Description

This handsome well coloured and marked little fish is normally dark olive green or brown on the back, becoming yellow and silver on the sides and a silvery-yellow belly with a dark lateral sstripe.The fins are normally pale yellow to bright orange. The dorsal fin spine is serrated. The scales are relatively latge with a few radiate striations.The mouth is terminal with two pairs of well developed barbels.

These beautiful little fish reach a maximum length of 140 mm.

Biology and Ecology

These handsome little fish prefer clear well aerated swiftly flowing streams and rivers.They feed mainly on aquatic insects.

Distribution

Widely distributed from tropical Africa southward to the escarpment streams of the Limpopo and the Incomati systems ie. the Crocodile and the Sabie rivers.

Threats

Water polution caused by domestic, agricultural, industrial and mining waste deposited into the feeder systems, changing the water to a low pH (acidic)

A few more members of the Barb species have been found in the Kruger National Park. All having characteristics similar to of those already mentioned. These little fish form a very important link in the food chain of the waters of the Kruger National Park

Hamilton's Barb.[/b]
[b]Hamilton se saagvin-ghielemientjie.
Barbus afrohamiltoni.

Description

It is named after Stevenson-Hamilton. This fish reaches a length of up tp 210 mm.The fins are serrated and the dorsal spine is well developed. It is silvery coloured with pinkish tinged fins.

Biology and Ecology
This little fish is mainly insectivorious and reaches sexual maturity at the length of 75 mm.

Distribution

It is widespread throughout the Kruger National Park and inhabits the more placid pools,

Rosefin Barb
Roosvin-ghielemientjie
Barbus argenteus

Description

A bright silvery little fish with dark pigmentation on the upper part. The caudal fin is often a rosy red. This little fish reaches a length of 200 mm.

Biology and Ecology

It feeds mainly on insects and reaches sexual maturity at the length of 70 mm.

Distribution

It inhabits well aerated water and prefers the colder upland streams entering the Park from the west and can be regarded as a seasonal migrant. It is seldomnly found below 460 m above sea level.


Longbearded Barb
Langbaard-ghielemientjie
Barbus unitaeniatus

Description

Long slender little silvery coloured with darker olive or bluish grey dorsal surface and a darker lateral striped fish which reaches a length of 125 mm. It sometimes develops thickened lips - depending on the habitat.

Biology and Ecology

It prefers larger areas of water associated with weeds and other aquatic vegetation but is also found in smaller streams. It feeds on aquatic insects and of the surrounding vegetation.

Breeding takes place after the rains in summer.

Distribution

Widespread throughout the Kruger National Park however not many are found in the river systems.

Bow striped Barb
Boogstreep-ghielemientjie
Barbus viviparus the name is misleading as this little fish is not viviparous.

A small little silvery fish with olive dorsal surface and a faint lateral stripe with tiny black edging forming the characteristic bow stripe only 65 mm in length. Some golden coloured members of this species have also been found.

Biology and Ecology

It frequents clear slowly flowing water with large masses of green filamentous algae. It feeds on both insect and vegetable matter.

Breeding occurs throughout summer and a tiny female can produce up to 8000 eggs.

Distribution

Is a very common little barb and is presented in all waters througout the Kruger National Park.

Broadstriped Barb
Breedgestreepte ghielemientjie.
Barbus annectens

Description

A small silvery coloured with olive coloured dorsal surface and a dark lateral stripes. The top of the iris is tinged red and there is dark spot at the base of the anal fin. The maximum length is 75 mm.

Biology and Ecology.

It frequents the grass or reed fringed banks of quiet flowing streams as well as the pools of the perrenial and seasonal rivers of the Kruger National Park. Its range seems restricted to the Park and can therefor be regarded as truly endenic to the Park.

Distribution

Widespread throughout all river systems of the Kruger National Park.

EastCoast Barb
Ooskus-ghielemientjie.
Barbus toppini

Description

This smallest of the Barb species - max 40 mm dainty little fish - inhabiting the Park waters. They are olive green coloured along the dorsal areas with golden colouring at the iris, the lower head and gill cover. a black streak extends through the eye to the snout tip. On the body the black streak extends to the caudal fin where it expands into a black patch. The belly and flanks are a very pale gold with almost colourless fins. If barbles are present they are very small and only as one pair.

After a spawning migration after the first rains, breeding takes place.

Distribution

Endenic to the Lowveld and widespread throughout the Kruger National Park.

Beira Barb
Beira-ghielemientjie
Barbus radiatus

Description

The dorsal area of this little fish is olive, the underparts a silvery white, little fish reaching 95 mm in length. The fins are pink or orange tinted fins and the red portion of the eye are typical. A dark lateral stripe extends from the snout to the caudal fin.Thecentres of the scales above the lateral stripe are dotted giving n impression of faint longitudinal lines.

Biology and Ecology

This little fish prefers the well aerated waters of the perennial and seasonal rivers with lots of aquatic vegetation, not in flowing currents. It feeds mainly on vegetable matter.

It is a typically Lowveld species, not found above an altitude of 460 m.

Distribution

Widely distributed and well reprsented in all the river and their sub systems throughout the Park.

Threats
Water polution caused by domestic, agricultural, industrial and mining waste deposited into the feeder systems, changing the water to a low pH (acidic)

Sharptooth/Common-catfish
Gewone/Skerptand-Baber.
Clarias gariepinus

Family : Claridae

Descripion

Well known for it's hardiness, rather than it's good looks. The bony head is large with small eyes and the wide mouth with four pairs of barbels is placed terminal.The turbity of the water has an effect on the colouring, the darker the water, the lighter the colour. The dorsal colour varies from a sandy-yellow to grey to olive with dark greenish brown mottles, even plain silvery specimens have been found, the underside is white.

The pectoral fins have stout serrated spines. Dorsal and anal fins are soft and long and reach to the tail is rounded. During the spawning period the fins may have a slight reddish edge.

This species grows extremely big up to 60 kg and 1.4 m in length, in size second only to the Vundu found in the Zambezi and further north.

Biology and Ecology.

These slow but very strong swimming fish inhabit most freshwaters as well as the brackish upperreaches of estuaries. These big fish have no specific habitat, they seem to prefer the fllood plains, lakes and dams as well as the large slow flowing rivers. They can survive extreme conditions and often are the longest survivors in awkward conditions, where they often work tunnels in the mud.

They will feed on anything ( omnivorous) available, they will catch live prey and also any organic carrion being : fish, birds,frogs, small mammals, reptiles, snails, shrimps, insects, seeds and fruit and . . . . . . . They often shoal and then chase fish into the shallows where they harvest. They are mainly bottom feeders but when the termites are flying, the will rise and share in the feast.

It has been observed that these catfish will even leave the water to feed on available food outside the water. The are extremely sensitive to smell and movement/vibrations in the water and on the surrounding land.

An air breathing organ is situated at the back of the head, which enables it to survive in moist mud and outside water when it moves overland in search for water during dry periods, it will survive as long as it does not dehydrate. They survive in drying pans while thrashing their tails in the mud, deepening it.

Catfish will often in the late afternoon be seen rising to the surface and take a gulp of fresh air with their barbles sticking out and then quietly disappear.

These fish reach sexual maturity within one year the size varying between 150 and 200 mm in length, and breed in summer after the rains, large numbers of mature fish will congregate in the shallows and spawn, a large female can produce 100 000 eggs which she deposits on the vegetation, where they hatch after 25 to 40 hours, the brood feed within 3 days while seeking refuge in the surrounding vegetation. The grow rapidly and reacha length of 200 mm within 12 months. The growth rate of the females slow down after three years, resulting in the males eventually exceeding the females in size.

Catfish form a very important of the food chain to other predator species in and around the waters, Crocodiles, Otters, Tiger Fish, Fish Eagles, Storks and Herons take large numbers of young and medium sized individuals of this species. When the water has receeded and the Catfish are struggling in the mud, Lions, Leopards and Hyaenas have seen to be joining in.

Distribution

This species are widespread and fouund in the tree savannas of tropical Africa, from the Nile to the Orange River in the west and the Umtamvuna River on the East Coast. They are also known to be in Israel, Lebanon and Turkey.

They are common in all the perennial and seasonal waters of the Kruger National Park.

Threats.

These extremely adaptable fish have very few threats but Water polution caused by domestic, agricultural, industrial and mining waste deposited into the feeder systems, changing the water to a low pH (acidic) will eventually take its toll.

Brown Squeaker
Bruin Skreeubaber
Synodontis zambezencis

Family : Mochokidae

Description:

A medium sized squeaker reaching a maximum length of 300 mm, it has three pairs of barbels, a high dorsal and a large adipose fin. The barbles of the lower jaw are branched. The head is bony with the plates projecting backwards. The dorsal and pectoral fins have strong spines, which can be locked in defence, dead crocodiles have been found with a squeaker stuck in its throat. These spines can also inflict a very painful wound when handled and these wounds should be medically treated.

The caudal fin is deeply forked.The turbity of the water has an effect on the colouring, the darker the water, the lighter the colour. The dorsal colour varies from a olive-yellow to brown or grey often with many black spots.The belly is normally pale olive-yellow.

Biology and Ecology.

These fish inhabit freshwaters below 300 metres above sea level, avoiding fast flowing rivers prefering quiet pools, where they occur in large numbers.

This species is bottom feeding and omnivorous, living off seeds, weeds,insects and molluscs.

They breed in early summer after the first floods.

Distribution

This species occur in the rivers of East Africa from the Zambezi down to the Pongolo Rivers. They are found in all the perennial and seasonal rivers of the KNP.

Threats.

Water polution caused by domestic, agricultural, industrial and mining waste deposited into the feeder systems, changing the water to a low pH (acidic) will eventually take its toll

Penant-tailed Catlet
Wimpelstert-suierbekkie
Chiloglanis anoterus

Family : Mochokidae

Description:

This small little catlet with its ventrally flattened haed and prominent ventral mouth with three pairs of barbles reaches a length of 80 to 100 mm. a characteristic of this species is that it's mouth forms a sucker with which it clings to smooth surfaces.

The sucking mouth and pectoral fins assist these little fish in climbing up damp weirs and the rocks of waterfalls.

The dorsal and pectoral fins have strong spines, the mucus covering the fish conatains an irritant as well as an anti coagulate, which can inflict a very painful wound when handled and these wounds should be medically treated.

An adipose fin is present.

The caudal fin of adult males is pointed.

The dorsal colouring is olive-brown with yellow patches, the belly and lips are yellow with pale fins with slightly darkened central portions.

Biology and Ecology.

These little squeaker inhabits the rocky rapids of well aerated headwater streams. They do not survive in stagnant pools, in the drier periods the seek refuge from the hot poorly aereated waters, among crevices and rocky outcrops.

This species is mainly bottom feeding on aquatic larvae.

They reach sexual maturity at the length of 50 mm and breed in early summer after the first floods.

They may be found clinging to the side of rocks slowly removed from the water.

Distribution

This species occur in the rapids of the southern tributaries of the Limpopo River down to the Incomati and Pongolo Rivers. They are quite plentifull in the rapids of the Sabie and Crocodile rivers of the KNP.

Threats.

Due to its dependance on aerated flowing water drought is a real threat.

Water polution caused by domestic, agricultural, industrial and mining waste deposited into the feeder systems, changing the water to a low pH (acidic) will eventually take its toll

Our concerns that we who care for nature have about the threat that polution has on nature, is justified. Here below is an extract of an article on the death of the crocodiles in the Olifants River. Solving the problem is not as simple as it may seem.

I do realise that it was published in January 2009, but it is still relevant and all may not have had access to it :

Crocodile deaths baffle Kruger
2009-01-21 14:33

Related Links
Croc deaths remain a mystery
Dam wall kills Kruger crocs
Croc deaths: Pollution blamed

Johannesburg - When three rotting crocodile carcasses were spotted in a remote corner of the Kruger National Park wildlife reserve, alarm bells started ringing for scientists.

A quickly organised autopsy, and aerial survey, confirmed their worst fears.

The giant reptiles were victims of a killer condition that had hardened their body fat to a rubber-like state, leaving them unable to move and defenceless against exposure, hunger, drowning or being eaten alive.

Since the first cases were found last May, some 170 crocodiles are dead and the true death toll could be double the figure. But a team of experts are still baffled by what triggered the die-off.

"It's almost incredible that we're struggling so much - there's nothing unfortunately that's jumping out at us," said Danie Pienaar, head of scientific services at Kruger Park.

'Heavily strained water resources'

Although the exact catalyst is proving elusive, the experts say the deaths are a telling sign of heavily strained water resources that flow into the park, which is home to Africa's big five: lion, leopard, elephant, buffalo and rhino.

"We don't have a clear idea but the sort of general agreement among all the researchers that it's probably the whole system that has deteriorated over time and been pushed to the brink," said Pienaar.

"There's no problem that crocodiles are going to die out," he added, "but it is just a very clear signal that there is something severely wrong in our river systems. And that we cannot really afford to ignore this anymore."

Kruger is South Africa's flagship wildlife park, drawing 1.3 million tourists a year and covering a landmass roughly half the size of the Netherlands.

Rancid fish

With the 110-year-old park home to some 850 non-plant species, it was feared that the infections could spread.

Known as pansteatitis or "yellow fat disease", the condition is associated with eating rancid fish and has been found in commercial crocodile farms, domestic cats, birds and fresh-water turtles but is not known to affect humans.

The condition attacks fat stores, depleting anti-oxidants and inflaming the fat in a process that scientists believe is very painful.

"There was a big concern that other species could be affected," Jan Myburgh, veterinarian specialising in toxicology, told AFP.

The chief worry was for lions - seen feeding on the dead crocodiles - and other cat species, based on the susceptibility of domestic cats, but no dead or sick felines have been found, he said.

The Nile crocodiles, which average five metres in length and 225kg, are indiscriminate eaters and well-known cannibals.

'Crocodiles are opportunists'

To prevent further infections, park officials burnt the recovered carcasses and shot two hippopotamuses to provide easily-accessible food.

"Crocodiles are opportunists, they are going to try eat any available food source," said Pienaar. "I saw a couple big crocodiles swimming with smaller crocs in their mouths."

"You don't want to get to a stage where crocodiles start dying because that is the top of the food chain predator. By the time they get affected, the whole food chain below them is probably affected," Pienaar added.

While dead crocodiles are no longer being found, the team of experts are still probing the die-off, which was not accompanied by mass fish kills as seen in an earlier flare-up outside park borders but farther along the same river.

The Kruger deaths occurred in a remote gorge which has faced increased siltation from a dam in neighbouring Mozambique, and is fed by one of South Africa's hardest working rivers which supports various heavy industries.

Clues are now being sought by a multi-pronged programme looking at the entire river system to get a better understanding of the cause and effect links around the deaths.

Scientists will also attempt to reproduce the disease in a controlled experiment from mid January to understand more about how it develops in crocodiles.

Meanwhile, the park and the team of experts are prepared for any further outbreak.

"Everybody is on the lookout, if one crocodile dies, we'll know about it immediately," said Myburgh.

- AFP

Now still on the same topic of polution the following is added :

Croc mystery still not solved
2009-06-18 08:37

Crocodile deaths baffle Kruger
Elise Tempelhoff

Vanderbijlpark - Crocodiles have once again started dying in the Olifants River Gorge in the Kruger National Park. Since the end of May a total of 12 carcasses were removed from the gorge.

This comes exactly one year after the mass death of Nile crocodiles (Crocodylus niloticus) during the winter last year when over 160 of these crocs died in the Olifants River due to pansteatitis - an orange hardening of the reptile’s fat.

Prof Henk Bouwman, of the school for environmental sciences and development at the Potchefstroom campus of North-West University, on Wednesday said scientists are incredibly frustrated because they’ve now been working for over a year to try to determine the exact cause of the deaths.

“Unfortunately we don’t have any real answers yet,” he said on Wednesday from the Kruger Park.

Bouwman, along with a team of students, scientists from the Universities of Pretoria and the Free State, as well as researchers from Sanparks, caught fish - the crocodiles’ food - in the river on Wednesday to determine the extent to which the fish were affected.

Thus far, no dead fish have been noticed in the river.

Bouwman said it is clear that the deaths were facilitated by the drop in temperature.

Fat becomes indigestible

He is of the opinion that the crocodiles eat fish in summer, which gives them direct energy. However, as soon as winter arrives, the crocodiles don’t eat and are thus dependent on their fat for energy. But the fat becomes indigestible because it is hardened and thickened.

The crocodile deaths stopped during the summer last year. Furthermore, Bouwman said his students will be taking samples of snails to analyse and try to determine whether they were exposed to poisonous substances which attack the hormones (Endocrine disruptives).

Some scientists feel that the heightening of the Massingir Dam’s wall in Mozambique is one of the reasons for the deaths, since it pushes sediment up into the gorge. The Olifants River Gorge is the crocodiles’ breeding area.

Dr Jan Myburgh of the department of paraclinical sciences of the faculty of veterinary science at Onderstepoort, earlier said the fat reaction in the Kruger Park crocodiles is exactly the same as that which caused the deaths of hundreds over the past few years in the Loskop Dam. There are currently only five crocodiles left in the Loskop Dam.

'Answers keep evading them'

Bouwman said researchers from San Parks are working day and night to try and solve the puzzle, but the answers keep evading them.

Bouwman was on his way to Stockholm, Sweden, to speak about the crocodile deaths at a conference, when he heard of the new batch of crocodile carcasses. He immediately cancelled his trip.

His speech was delivered by someone else. In the meantime, Bouwman has learned that scientists from Norway, Sweden and Denmark are all ready to come and help with the research surrounding the mysterious crocodile deaths.

Due to acidic mine water, mining activities and pesticides and insecticides, the Olifants River is one of the most stressed rivers in the country.

- Beeld

Just a bit more about polution.

Manganese, lead and strontium bioaccumulation in the tissues
of the yellowfish, Barbus marequensis from the lower Olifants
River, Eastern Transvaal

Tharina Seymore*, Hein H du Preez and JHJ van Vuren
Department of Zoology and RATE, Rand Afrikaans University, PO Box 524, Auckland Park 2006, South Africa Abstract

The bioaccumulation of manganese, lead and .strontium in the freshwater fish (Barbus marequensis) from the lower Olifants River.
E. Transvaal. was investigated. The highest concentrations of these metals were detected in the vertebrae and gills. The localities
in the Kruger National Park did not differ significantly fron each other and therefore no clear indication as to where the highest bioaccumulatuion had occurred, could be established. However, the highest manganese and strontium levels occurred in fish Irom the Selali River. Tor the future monitoring of manganese, lead and strontium levels in bony fish, it is suggested that bony tissues (e.g. vertebrae, opercular bone or scales), gills, liver and muscle [issue are used.

Introduction

Manganese, lead and strontium appear to be metabolised via calcium metabolic pathways (Hammond and Beliles, 1980) and,therefore, accumulate mainly in the skeletal tissues of fish (Paul and Pillai, 1983; Patterson and Settle, 1977;Bagenaletal., 1973).
Manganese is an essential trace element and shows relatively low
toxicity to aquatic biota. Lead is a non-essential metal and is
known to be toxic to aquatic organisms, especially fish (Klein,
1962). The requirement of strontium by fish has not been
established, but appears to be a non-essential metal, for although it
is a bone-seeking element, strontium is not essential for bone
formation (Sauer and Watabe, 1989).
In the natural freshwaters, manganese is rarely found at
concentrations above 1 mg/1 (Hellawell, 1986), while concentrations
of soluble lead are generally less <3ug/l (Forstner and Wittmann,
1979). Strontium values in South African surface waters typically
range from 50 to several hundred ug/l (Kempster, 1994). The forms
in which manganese and lead occur in freshwater are mainly
particulate or complexed forms (Seenayya and Prahalad, 1987;
Moore and Ramamoorthy, 1984), decreasing the bioavailability of
these metals to the fish. As the pH of the water decreases, however,
the ionic state of the metals becomes more prevalent and toxicity
increases (Wang, 1987). Strontium, on the other hand, is found in
water in solution rather than in particulate form (Carraca et
al.,1990) and might, therefore, be more bioavailable to fish for
uptake. Nevertheless, in calcium-rich waters calcium will compete
with strontium in the uptake process, resulting in lower strontium
accumulation by the fish (Phillips and Russo, 1978). Factors such
as the water pH, water hardness, organic materials and other metals
will, therefore, influence the toxicity of these metals, but there also
seems to be a relation between the concentrations of these metals
in the water and the accumulation thereof by freshwater fish
(Bermane, 1969).
The manganese, lead and strontium concentrations in the water
can increase to quite an extent due to the influence of industrial
wastes and mining effluents on the river. The combustion of oil
and gasoline accounts for more than 50% of anthropogenic lead
emissions and therefore atmospheric fall-out is usually the most
important source of lead in freshwaters (Moore and Ramamoorthy,
1984). Fish can be affected sublethally when they are chronically
exposed to lead concentrations ranging between 5 and 5 000 ug/l
inorganic lead (Haux et al., 1986). Two distinctive characteristics
of chronic lead poisoning in fish are black tails, also an early
symptom of spinal deformities (Hodson et al., 1979), and a strong
inhibition of the aminolevulinic acid dehydratase (ALA-D) activity
in erythrocytes (Haux et al., 1986). The 96-h LC50 value of total
lead for freshwater fish varies from 0.5 to 482 mg/lPb, depending
on the water hardness and life stage of the fish (Moore and
Ramamoorthy, 1984; Pickering and Henderson, 1966).
Manganese and strontium can also affect fish adversely at
elevated levels, but limited research has been done in this field.
Sublethal effects can occur at a manganese concentration of 0.278
g/l (Seymore, 1994), while the 96-h LC50 value can vary from
1.723 to 3.230 g/l Mn (Nath and Kumar, 1987). For strontium the
96-h LC50 value for fish has been determined to be greater than
92.8 mg/l Sr (Dwyer et al., 1992). The general order in which the
relevant three metals can affect fish, is therefore: Pb > Mn > Sr.
Associated factors, such as environmental conditions, should,
however, be taken into consideration when assessing the toxicity
of these metals to fish.
The objective of this study was to determine the extent of
bioaccumulation (with respect to site, seasons, years, age, tissues)
of manganese, lead and strontium in the yellow fish, Barbus
marequensis from the lower Olifants River, E. Transvaal. The
data were also used to establish which of the tissues contained the
highest and lowest concentrations of these metals, respectively.
The Olifants River was selected as study area because it is one of
the most important rivers that flows through the Kruger National
Park. Furthermore, anthropogenic activities in the catchment of
this river may effect the quality of the water flowing through the
Kruger National Park.

* To whom all correspondence should be addressed.
Present address: Institute for Water Quality Studies, Private Bag X313,
Pretoria 0001, South Africa
(012) 808-0374; [F](012) 808-0338; e-mail een@dwas-hri.pwv.gov.za
Received 14 July 1994; accepted in revised form 8 November 1994.