After more than a century of confusion, scientists have identified a new species of grouper fish, the mud grouper (E. randalli), following a detailed investigation that included a trip to a bustling fish market in Vietnam.
Their findings, published on November 25 in the journal Species Diversity, settle a debate over the classification of longtooth groupers and mark an important step in understanding this commercially valuable group of fish.
The debate centered on whether longtooth groupers—predatory fish prized for their culinary value across East Asia—were a single species or two distinct ones.
Early descriptions had categorized the group as two species: E. bruneus, first identified in 1793, and E. moara, described in 1843.
But as time passed, researchers grouped them under a single name, E. bruneus. This decision created confusion, worsened by inaccuracies in scientific diagrams, overlapping local names and subtle variations that were difficult to identify.
To resolve the issue, a team of researchers embarked on a detailed investigation.
They collected grouper specimens from the South China Sea and other regions, including several bought from the Ha Long fish market in Vietnam, a location teeming with marine life.
By analyzing the fish's DNA, studying their physical features and revisiting historical records, the team uncovered subtle but consistent differences between the groupers found in the South China Sea and those from the East China Sea.
These differences revealed that the two populations were, in fact, separate species.
The newly discovered mud grouper was distinct enough to warrant its own classification, while the name E. bruneus was confirmed for the longtooth groupers found further north, in waters off Taiwan, South Korea and Japan.
"The specific name Randalli is named in honor of the distinguished ichthyologist, [the] late Dr. John E. Randall, who passed away in 2020," the authors wrote of the new species in the study.
The two species can be distinguished in several ways, including the number of thinner, more flexible dorsal fins (soft rays) on the fish's back.
The study also highlighted the historical confusion that had persisted in classifying these fish. Past researchers had relied on incomplete or distorted diagrams, which led to misidentifications and incorrect assumptions about their populations.
The name E. moara, previously applied to certain specimens, was ultimately determined to be a synonym for E. bruneus, resolving part of the taxonomic confusion.
Mud groupers are found in the coastal waters of Vietnam, China and southern Taiwan, while the longtooth groupers live in northern regions.
Recognizing these species as separate entities has important implications for fisheries and conservation.
Accurate classification allows for better monitoring of fish populations and ensures that conservation and aquaculture strategies are tailored to the specific needs of each species.
"The use of correct scientific names is highly recommended for appropriate development of stock management, aquaculture, and conservation of the longtooth and mud groupers," the researchers wrote.
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References
Hoshino, K., Senou, H., & Nguyễn, Q. V. (2024). Taxonomic Status of the Commercially Important Grouper, Epinephelus bruneus and E. moara (Osteichthys: Perciformes: Epinephelidae), with the Redescription of E. bruneus and the Description of a New Species. Species Diversity, 29(2), 389–407. https://doi.org/10.12782/specdiv.29.389
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