Papua is an area that has extraordinary biodiversity. However, not much is known about its biological richness.

Hari Suroto, Archaeological Researcher from the National Research and Innovation Agency [BRIN], explained that during the Pleistocene, approximately 17,000 years ago, sea level conditions were very low. At that time, Australia and Papua were joined as a unique landmass known as the Sahul Land [Sahulland].

The fauna that live in Australia and Papua show similarities, so that this land connection allows fauna from mainland Papua to roam in Australia, and vice versa, from Australia to Papua.

“The similarity of flora and fauna between Papua and Australia can still be observed today. Types of freshwater fish found in southern Papua are also found in northern Australia,” said Hari Suroto, early September 2022.

One example is a freshwater fish called glass fish or nurse fish. This species is known to live in the Digul River and swamps in Boven Digoel District, the Bian River, the Kumbe River and the Maro River, the Mappi River, the Siretz River, the Betz River, the Omanesep River, the Fayit River, the Fai River and the Mamats River.

“This fish is not only found in Boven Digoel, Merauke, Mappi, Asmat, but also found in the Adelaide River, Northern Territory or northern Australia. “Based on research in the Adelaide River, northern Australia, glassfish breed more during the dry season, around May to November,” said Hari.

Weird fish

Hari revealed that the scientific language for glass fish is Kurtus gulliveri castelnau and it is a strange fish. That’s because of its unique shape and character.

The body is flat and tall, like an elongated rhombus. It is called a glass fish because on the right and left sides it is silver.

While male glass fish are called nurse fish because they have a bulge above their heads, similar to a curved rope. While females, do not have it. On the rope, the male glassfish lays and takes care of his eggs.

The unique shape of the head is thought to be an adaptation to an environment with low oxygen and high turbidity. This species is known for its unusual breeding strategy; males carry fertilized eggs on a bony hook protruding on the forehead [supraoccipital]. The diameter of the eggs is 2.1 to 2.5 mm.

“Male glass fish with eggs on their heads, until they hatch, can only be found during the breeding season. The habitats are river estuaries, mangrove swamps, nipa swamps, and slow-moving rivers with high turbidity,” said Hari.

After hatching, the larvae detach from their mother and live on the surface of the water. The larvae have a large yolk sac, forming the dorsal, caudal and anal fins.

The larva then grows to 6.9 mm, characterized by an ax-shaped body that is almost entirely transparent. Large head, relatively small eyes, propercular spines and a prominent, bulging gas sac.

Hari explained, the scientific name Kurtus gulliveri castelnau, is specific to honor Thomas Allen Gulliver, who worked in the Australian postal and telegraph service, living near the Norman River, Carpentaria Bay.

Gulliver collects a number of glassfish specimens he catches in the Norman River. In 1878, a man named Castelnau described the glassfish from a number of specimens collected by Thomas Allen Gulliver, and gave the scientific name Kurtus gulliveri castelnau.

Based on research by Robert Buhdy, Norce Mote, and Edy Melmambessy on the Digoel River in Edera District, Mappi Regency, published in the journal Musamus Fisheri and Marine [October 2018], it is stated that glassfish have a high abundance.

The catches obtained during 2 months of observation by the research team indicated that there were 28 species of fish divided into 8 orders and 20 families. The family that has the highest number of individuals is Ambassidae, the species Parambassis gulliveri; family Kurtidae species Kurtus gulliveri and family Ariidae species Cinetodus crassilabris.

Another study on species abundance was also conducted at the mouth of the Maro River, Karang Indah Village, Merauke, which was conducted by Norce Mote, Sebastianus Ayarau, and Sisca Elviana. The results of the study explained that the species that had the highest relative abundance value was glass fish with a value of 23.08 percent.

In 2021, said Hari, glass fish will also be found in Telaga Wawiyer which is connected to Berau Bay via the Budigi River, Mitimber Village, Mbahamdandara District, Fakfak Regency, West Papua.

This glass fish is the catch of residents who are fishing for nine fish. Glass fish by the people of Mitimber are called giti-giti fish. However, glass fish also have many names, some call glassfish, nurse fish or also called nurseryfish, breakfastfish, humpheads, and incubatorfish.

In Papua itself, the habitat of the glassfish is threatened by illegal gold mining in the upper rivers and illegal logging of trees along the rivers in the pedala