Genetic Diversity and Population Structure of the Mottled Spinefoot Siganus fuscescens in Vietnamese Waters

10/09/2026

The rabbitfish family Siganidae is one of the most common groups of herbivorous fishes on coral reefs, in mangrove forests and on seagrass and seaweed beds across the Indo-Pacific and the eastern Mediterranean. The family Siganidae comprises a single genus, Siganus, with 29 recorded species. As herbivores, members of the rabbitfish family help remove algal biomass on coral reefs, creating clean substrates for coral larvae to settle on. They therefore play an important role in controlling algal growth and contribute to maintaining the health of coral reef ecosystems.

Among the species of the family Siganidae, the mottled spinefoot Siganus fuscescens (Houttuyn, 1782) has the widest distribution range. Thanks to this broad distribution, the mottled spinefoot is an ideal subject for studying the influence of ecological factors (environmental gradients) and geographical distance on genetic variation within populations. In Viet Nam, the mottled spinefoot is commonly found on coral reefs as well as in lagoons and coastal estuaries.
The mottled spinefoot is an economically important and highly sought-after species. Overexploitation has caused its populations to decline, affecting both fishery resources and the health of coral reefs. This situation calls for research into the genetic diversity of the mottled spinefoot to provide a basis for the sustainable management of rabbitfish resources in Viet Nam. A research team led by Assoc. Prof. Dr. Nguyen Van Quan and Dr. Do Dinh Thinh, together with colleagues at the Haiphong Branch of Institute of Oceanography (Institute of Oceanography), carried out a study on the genetic diversity and population structure of the mottled spinefoot in Vietnamese waters. In the study, 152 specimens of the mottled spinefoot were collected from six populations, namely Nghi Son, Cua Gianh, Lap An, Son Cha, Ly Son and Phu Quoc (Figure 1). Analysis of the mitochondrial control region identified 35 haplotypes, with the highest numbers of genotypes found in the Cua Gianh, Son Cha and Ly Son areas. The results also showed that the populations had high haplotype diversity (0.706-0.870) and low nucleotide diversity (0.004-0.09). The analysis further indicated that the expansion of rabbitfish populations in Vietnamese waters took place approximately 23,000-62,000 years ago, during interglacial periods.

This study makes an important contribution to understanding the genetic diversity of the mottled spinefoot in the Indian Ocean - Western Pacific region. The research findings have been published in the journal Environmental Biology of Fishes under the title “Genetic diversity and population structure of the mottled spinefoot Siganus fuscescens in Vietnam”.

Figure 1. Map of the sampling sites for the mottled spinefoot in this study. Abbreviations: NS (Nghi Son), CG (Cua Gianh), LA (Lap An), SC (Son Cha), LS (Ly Son) and PQ (Phu Quoc)

Figure 2. Haplotype network of the rabbitfish genotypes in this study. Abbreviations: NS (Nghi Son), CG (Cua Gianh), LA (Lap An), SC (Son Cha), LS (Ly Son) and PQ (Phu Quoc)

Figure 3. Results of the PCoA analysis based on DNA data of the mottled spinefoot populations. Abbreviations: NS (Nghi Son), CG (Cua Gianh), LA (Lap An), SC (Son Cha), LS (Ly Son) and PQ (Phu Quoc)

Figure 4. Specimen of the mottled spinefoot Siganus fuscescens (Houttuyn, 1782)

Figure 5. DNA extraction from rabbitfish samples at the Key Laboratory for Marine Biodiversity and Environment (Haiphong Branch of the Institute of Oceanography)

Translated by Quoc Khanh
Link to Vietnamese version

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