A small fish that vanished from Sri Lanka’s scientific records for nearly 90 years has been found again in the Jaffna Peninsula, giving researchers a rare opportunity to connect a historical record from 1936 with a living population in Northern Sri Lanka. The fish, identified as the Yellow-stripe Goby (Mugilogobius chulae), was recently recorded at Karainagar on the Karaitivu Island during a survey of aquatic habitats in the North. Its discovery is particularly significant because the species was previously known from Sri Lanka only through a record made by the zoologist Paulus Edward Pieris Deraniyagala in 1936. No confirmed modern record had emerged from the country for almost nine decades, leaving the species largely as a name preserved in old scientific literature.
The rediscovery was made by researchers Janamina Bandara, Sahan Randeniya and Aravind Manoj, whose findings have now been published in the Davao Research Journal. Their fieldwork, however, produced more than the return of a species missing from Sri Lanka’s modern records. The same survey also confirmed the presence of the Black-spotted Snubnose Goby (Pseudogobius melanosticta), providing the first verified Northern-most record of the species in Sri Lanka. Together, the two findings extend the known distribution of both Gobies and add new information to the country’s fish fauna, particularly in a part of the island that has historically received less scientific attention than many other regions.
The Yellow-stripe Goby
The discovery of the Yellow-stripe Goby was not immediately recognised as the return of a fish that had been absent from Sri Lanka’s scientific record for so long. During fieldwork in Northern Sri Lanka, the researchers came across two unfamiliar Gobiidae fishes in a small aquatic habitat at Karainagar. The fish could not be confidently identified in the field, so the researchers carried out additional searches in nearby tidal pools with the assistance of local residents. They photographed and collected specimens for more detailed examination. It was only after returning to the laboratory and studying the specimens that the identity of one of the unfamiliar fish became clear: it was the Yellow-stripe Goby.
Three specimens were collected as taxonomic voucher material. They were very small, measuring approximately 14 to 19 millimetres in standard length, and were later deposited in the fin-fish collection of the Fisheries and Aquaculture Department, the Fisheries and Marine Sciences and Technology Faculty, the Ruhuna University. The specimens have now become an important part of the scientific record because they provide modern physical evidence of a species that had previously been represented in Sri Lanka by a historical record dating back to the 1930s. The discovery effectively brought the fish back into the country’s contemporary scientific literature after decades without a confirmed sighting.
Deraniyagala named it Vaimosa valigouva
The story of the Yellow-stripe Goby in Sri Lanka begins almost a century ago. In 1936, Deraniyagala described a fish collected from the Point Pedro area of Jaffna and named it Vaimosa valigouva. At that time, the fish was considered a distinct species. Later taxonomic work established that Vaimosa valigouva was a junior synonym of Mugilogobius chulae, which is the scientific name recognised today. This means that Deraniyagala’s specimen was, in effect, the only historical record of Mugilogobius chulae from Sri Lanka. The original type specimen was deposited at the Natural History Museum in London, England, and a specimen believed to be the paratype was later noted in Sri Lankan Museum material. No further confirmed records followed, and the species gradually disappeared from more recent scientific literature and assessments of Sri Lanka’s fish fauna.
The absence of records did not necessarily mean the Yellow-stripe Goby had disappeared from the island. It could simply have been a case of a species living in habitats that had not been adequately surveyed. That possibility is particularly relevant in Northern Sri Lanka, where biological research was severely restricted for decades because of the civil conflict, security concerns, restricted access and the presence of landmines. Large parts of the Jaffna Peninsula and its surrounding islands therefore received comparatively little systematic scientific attention. The gap was particularly important for aquatic biodiversity, since many small freshwater, brackish-water, tidal and coastal habitats in the North remained poorly investigated. Fish surveys continued in other parts of the country, but, many of the smaller aquatic habitats of the North remained outside regular scientific fieldwork.
More systematic surveys in Northern Sri Lanka have become possible in recent years, creating opportunities for researchers to return to habitats that were difficult to access in the past. The rediscovery of Mugilogobius chulae shows why such work can be important. A species can disappear from scientific records without necessarily disappearing from nature. In this case, almost 90 years passed between Deraniyagala’s record and the modern confirmation of the species in Sri Lanka. The new specimens have therefore provided more than a new entry on a checklist. They have connected a record from 1936 with evidence from the present day and shown that the fish continues to occur in the island’s Northern waters.
There is also an interesting geographical link between the old record and the new discovery. Deraniyagala’s original specimen came from the Point Pedro area, and the newly discovered specimens were found at Karainagar, approximately 20 to 22 kilometres from the historical locality. The modern discovery therefore took place relatively close to the area from which the species first became known to science in Sri Lanka. Mugilogobius chulae is distributed across the eastern Indian Ocean, South-East Asia and the western Pacific, and the Sri Lankan record is considered one of the western-most known occurrences of the species in the Indian Ocean. For Sri Lankan ichthyology, that geographical detail gives the discovery importance beyond the simple confirmation of an old record.
Its markings make it distinctive
The fish itself is small, but its markings make it distinctive once its identifying features are known. The Yellow-stripe Goby has a golden-yellow body, with the underside becoming white. Six black transverse bars run across the side of the body, and there is a distinct pair of black spots near the base of the tail. The first dorsal fin also carries a prominent black marking. The researchers examined further characteristics, including the arrangement of scales and fin rays, body proportions and teeth, to confirm the identification. They also compared the specimens with related species that could potentially be confused with Mugilogobius chulae. The colour pattern was particularly useful, with the six distinct black bars supporting the identification. The researchers believe that the specimens were juveniles because of their small size compared with the reported adult size of the species. In an interesting twist to the rediscovery, the tiny fish that helped solve a mystery nearly nine decades old were themselves very young.
The Black-spotted Snubnose Goby
The same survey produced another finding of significance. During the examination of the Karainagar habitat, the researchers encountered the Black-spotted Snubnose Goby. The species is distributed across tropical Indo-Pacific waters and is capable of living in freshwater, brackish and marine environments. Its occurrence in Sri Lanka, however, has been poorly documented. Historical records include specimens collected from the Panadura Lagoon and other estuarine environments on the Western coast, but there had been no recent verified record from the Northern part of the island. The Karainagar specimens therefore provide the first confirmed Northern-most record of the species in Sri Lanka, filling another geographical gap in the country’s fish records.
The Black-spotted Snubnose Goby has its own distinctive appearance. Its body is greyish with a yellowish tint and covered in numerous small dark-brown spots, with a series of darker blotches forming a more prominent band along the side. One of its most striking features is a black, tear-shaped marking below the eye. The researchers also observed bright blue pigmentation around the operculum and a distinctive black-and-yellow pattern on the first dorsal fin. These characteristics, together with other morphological features examined during the study, helped establish the identity of the specimens.
Perhaps one of the most interesting details about both findings is the simplicity of the habitat in which they were made. The two species were found in a relatively small and fragmented pool within a tidal-flat environment. The pool was approximately seven to eight metres (m) wide and only 35 to 40 centimetres deep. Its bottom consisted mainly of silty sand and gravel with scattered debris. The water was slightly turbid and had a salinity of approximately 15 parts per thousand, indicating brackish conditions. The researchers recorded a temperature of around 31 degrees Celsius, a pH of 8.5 and dissolved oxygen of 6.5 milligrams per litre. What appeared to be an ordinary shallow pool was therefore supporting a surprisingly interesting fish community.
The Gobies were recorded alongside species including Bhava vittata, Oryzias carnaticus and the introduced Oreochromis niloticus. The researchers’ observations also suggested that tides could influence the occurrence or movements of the Gobies. During the first evening survey, conducted around the high tide, only one Yellow-stripe Goby and around six to seven Black-spotted Snubnose Gobies were observed. The following morning, around the low tide, approximately 15 to 20 Black-spotted Snubnose Gobies were recorded. Only three Yellow-stripe Gobies were observed along a 20-m stretch of the pool.
The findings have once again drawn attention to the biodiversity potential of Northern Sri Lanka. The Jaffna Peninsula and its surrounding islands are often associated with their cultural heritage, dry-zone landscapes, lagoons and coastal environments, but, these landscapes also contain a network of small aquatic habitats that can support fish communities that are easily overlooked. Tidal pools, lagoons, brackish-water areas and other shallow habitats may appear unremarkable, but, they can contain species that are difficult to detect unless researchers specifically examine them. The Yellow-stripe Goby was not rediscovered through a massive expedition covering the entire Peninsula. It was found during fieldwork that included a detailed examination of a relatively small aquatic habitat. That fact alone demonstrates the value of continued field surveys in areas that have not received sustained scientific attention.
For scientists studying biodiversity, records such as these are important because knowing where a species occurs is fundamental to understanding its ecology and distribution. Historical records provide evidence of where species were found in the past, and modern surveys provide evidence of what is present today. Bringing those two sets of information together can help researchers understand geographical distributions, identify gaps in knowledge and determine where further investigation is needed. In the case of the Yellow-stripe Goby, the 1936 record remained an important historical clue for decades. This year’s (2026) discovery has now provided modern evidence connecting that record with a living population. The Northern record of the Black-spotted Snubnose Goby similarly fills an important gap in the known distribution of that species within Sri Lanka.
The researchers have called for further surveys in Northern Sri Lanka and the continued monitoring of freshwater and brackish-water ecosystems. More work is needed to understand the abundance, population structure, habitat requirements and conservation status of the two species. They have also identified molecular-level confirmation of the species identities as a possible direction for future research. Both species are currently listed as of the Least Concern on the International Union for the Conservation of Nature Red List, and neither is listed under the Convention on the International Trade in Endangered Species. The fish studied are also not among the protected fish species listed under Schedule VI of Sri Lanka’s Fauna and Flora Protection Ordinance. These classifications do not remove the need for further study, particularly because small aquatic habitats can be vulnerable to changes in water quality, habitat modification and other environmental pressures.
The rediscovery of the Yellow-stripe Goby therefore carries a significance that extends beyond the fish itself. It shows how gaps in scientific records can sometimes say as much about the history of research as they do about the species being studied. Northern Sri Lanka experienced decades in which access for systematic biological research was difficult, and many habitats were left without regular scientific surveys. As researchers return to these areas, old records can become useful guides for finding species that have not been seen for generations. The 1936 record by Deraniyagala provided precisely such a clue, and almost nine decades later, researchers have been able to confirm that the species is still part of Sri Lanka’s natural environment.
The Northern region contains lagoons, tidal flats, pools, streams, wetlands and other aquatic environments, many of which have received limited long-term study. The rediscovery of a fish that had been absent from the scientific record for nearly 90 years, together with the confirmation of a second Goby farther north than previously verified, suggests that the country’s knowledge of its aquatic biodiversity is still incomplete. Each new survey has the potential to add another piece to that picture.
The writer has an interest in science and biodiversity
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The views and opinions expressed in this column are those of the writer, and do not necessarily reflect those of this publication