A fisherman’s tale
On December 23, 1938, Hendrik Goosen, the captain of the trawler Nerine, returned to the harbour at East London, South Africa, after a trawl between the Chalumna and Ncera Rivers. As he frequently did, he telephoned his friend, Marjorie Courtenay-Latimer, curator at East London’s small museum, to see if she wanted to look over the contents of the catch for anything interesting, and told her of the strange fish he had set aside for her.
Correspondence in the archives of the South African Institute for Aquatic Biodiversity, formerly the JLB Smith Institute of Ichthyology, show that Goosen went to great lengths to avoid any damage to this fish and ordered his crew to set it aside for the East London Museum. Goosen later told how the fish was steely blue when first seen, but by the time the ‘Nerine’ entered East London harbour many hours later, the fish had become dark grey.
Fossils come to life
Failing to find a description of the creature in any of her books, she attempted to contact her friend, Professor James Leonard Brierley Smith, but he was away for Christmas. Unable to preserve the fish, she reluctantly sent it to a taxidermist. When Smith returned, he immediately recognized it as a coelacanth, known only from fossils.
Smith named the fish Latimeria chalumnae in honour of Marjorie Courtenay-Latimer and the waters in which it was found. The two discoverers received immediate recognition, and the fish became known as a “living fossil”. The 1938 coelacanth is still on display in the East London, South Africa, museum.
Over the years Coelacanths were discovered in the Comores, Mozambique and Madagascar. A second species was discovered in Indonesia in 1997.
Captured on film
On October 28th 2000, Pieter Venter, Peter Timm and Etienne le Roux were near the end of an eight-minute initial exploratory dive to 104 m in the Jesser Canyon at Sodwana Bay, in the St Lucia Marine Reserve on the north coast of South Africa. As they were about to ascend, Pieter Venter saw a large, pinkish eye reflecting the beam of his underwater light.
He approached, and underneath an overhang he saw a fish about two metres long. After a few seconds he realised, much to his surprise, that the pale blue fish with its unusual lobed fins was a coelacanth. He summoned Peter Timm, and they saw two more coelacanths.
Timm, who was concerned with their ascent, was unable to confirm the sighting. But later, on the surface, Venter convinced him that these fish were coelacanths, and the divers then decided to arrange an expedition to do additional dives with a video camera to record the presence of this species.
A subsequent dive to confirm the identity of these fish and film them was successful. After searching caves along the wall of the canyon for 12 minutes, three coelacanths were sighted and filmed with the video camera at a depth of 108 m.
The largest fish was between 1.6 and 1.8m in length, and the other two coelacanths were about 1.5 and 1.0m. The water temperatures at the bottom for the October and November dives were 17C and 18C respectively.
380 million years in the making
The fossil record of coelacanths, comprising some 120 species arrayed in about 47 genera and three or four families, extends from the Middle Devonian (380 million years ago) to the end of the Cretaceous (70 million years ago), when the coelacanths were thought to have died out, along with the dinosaurs and many other fossil groups.
The first fossil coelacanth was described in 1836. The genus name Coelacanthus (meaning “hollow spine”) refers to the hollow neural and haemal spines of the vertebrae that connect to the tubular pterygiophores supporting the dorsal and ventral caudal fin.
Female coelacanths give birth to live young, called “pups”, in groups of between five and 25 fry at a time. The pups are capable of surviving on their own immediately after birth.
Their reproductive behaviours are not well known, but it is believed that they are not sexually mature until after 20 years of age. Gestation time is estimated to be 13 to 15 months. Based on growth rings in their ear bones (otoliths), scientists infer that individual coelacanths may live as long as 80 to 100 years.
Coelacanths live as deep as 700 m below sea level, but are more commonly found at depths of 90 to 200m.
Article by Gwynne Howels, KZN Wildlife