A new sciaenid fish, Johnius sasakii sp. nov. from the East Malaysian coastal waters of Sabah and Sarawak, Borneo is described herein. Johnius sasakii sp. nov. can be separated from the close congeners, Johnius heterolepis and Johnius carouna by having less gill rakers on the lower limb of the first gill arch (mode number 9 vs. 10 for J. heterolepis; 11 for J. carouna). It can be distinguished from J. heterolepis with the higher modal number of gill rakers on the upper limb of first gill arch (5 vs. 4), shorter anal-fin base length (9% vs. 10% of SL) and first anal-fin ray length (10–12% vs. 12–13% of SL) respectively. Furthermore, J. sasakii sp. nov. can be further differentiated from J. carouna by its shorter second anal-fin spine length 7–10% SL (usually 8–10%) vs. 11–14% SL (usually 11–12%) and slightly deeper body depth 25–29% SL (usually 26–28%) vs. 23–28% SL (usually 24–26%). Meanwhile, J. sasakii sp. nov. can be easily differentiated from J. macrorhynus by a present of molariform teeth on inner rows of jaws and stumpy gill rakers. Johnius (Johnius) sasakii sp. nov. can be clearly distinguished from species of the subgenus J. (Johnieops) by the lack of enlarged outer row teeth on upper jaw. A Kimura 2-parameter genetic distance comparison of 450 bp sequences of mitochondrial 16S rRNA and 488 bp nuclear gene S7 showed that J. sasakii sp. nov. are highly differentiated from J. heterolepis (16S: 10.4%, S7: 5.8%), J. carouna (16S:19.3%, S7:8.4%); and J. macrorhynus (16S: 16.7%, S7: 8.1%) respectively. The study highlights that the genetic approach from mtDNA and nDNA can contribute to the confirmation of taxonomic status of sympatric species in genus Johnius.

Given the identification of the new species Johnius taiwanesis, the Johnius genus in Taiwanese water is here reviewed through a collection of field samples, museum specimens, and a review of the Taiwanese scientific literature. Seven valid Johnius species were successfully identified and distinguished based on gill raker length, tip of upper jaw to mouth hinge length, tip of lower jaw to mouth hinge length, and length of second spine of anal fin. Our phylogenetic tree based on cytochrome oxidase subunit I (COI) showed the existence of high interspecific genetic diversity within the genus Johnius forming a monophyletic group. The Johnius species in Taiwan are mainly distributed in a latitude ranging from Xingda (22.4° N) to Hsinchu (24.8° N) with J. taiwanensis, J. distinctus, and J. belangerii representing the most abundant species caught throughout the year. Johnius amblycephalus and J. borneensis were only caught in the summer, while J. trewavasae was rarely caught. In conclusion, we provide a dichotomous key for the genus Johnius in Taiwan waters.

Benthic species, though ecologically important, are vulnerable to genetic loss and population size reduction due to impacts from fishing trawls. An assessment of genetic diversity and population structure is therefore needed to assist in a resource management program. To address this issue, the two-spined yellowtail stargazer (Uranoscopus cognatus) was collected within selected locations in the Indo-West Pacific (IWP). The partial mitochondrial DNA cytochrome c oxidase subunit 1 and the nuclear DNA recombination activating gene 1 were sequenced. Genetic diversity analyses revealed that the populations were moderately to highly diversified (haplotype diversity, H = 0.490–0.900, nucleotide diversity, π = 0.0010–0.0034) except sampling station (ST) 1 and 14. The low diversity level, however was apparent only in the matrilineal marker (H = 0.118–0.216; π = 0.0004–0.0008), possibly due to stochastic factors or anthropogenic stressors. Population structure analyses revealed a retention of ancestral polymorphism that was likely due to incomplete lineage sorting inU. cognatus, and prolonged vicariance by the Indo-Pacific Barrier has partitioned them into separate stock units. Population segregation was also shown by the phenotypic divergence in allopatric populations, regarding the premaxillary protrusion, which is possibly associated with the mechanism for upper jaw movement in biomechanical feeding approaches. The moderate genetic diversity estimated for each region, in addition to past population expansion events, indicated thatU. cognatuswithin the IWP was still healthy and abundant (except in ST1 and 14), and two stock units were identified to be subjected to a specific resource management program.

In terms of sheer abundance, taxonomic diversity, and species richness, Malaysia has one of the most diverse Sciaenidae in the Indo-West Pacific. Up to ten valid species of the sciaenid fish genus Johnius (e.g., J. amblycephalus (Bleeker, 1855), J. belangerii (Cuvier, 1830), J. borneensis (Bleeker, 1850), J. carouna (Cuvier, 1830), J. coitor (Hamilton, 1822), J. heterolepis Bleeker, 1873, J. macrorhynus (Lal Mohan, 1976), J. plagiostoma (Bleeker, 1849), J. sasakii Hanafi et al., 2022 and J. weberi Hardenberg, 1936), and with additional newly recorded species as J. trewavasae Sasaki, 1992, have been recorded to occur in East Malaysia (Borneo Island) coastal waters. The newly recorded species is a close congener to J. heterolepis Sasaki, 1992 and can be well distinguished by several characters and molecular evidence. The goal of this study is to review the taxonomic status of Johnius species in East Malaysia, Borneo Island, by using a literature review, morphological inference and molecular characters. Principal Component Analysis (PCA) successfully discriminates based on second anal spine length and gill raker length within sampled specimens. A phylogenetic tree based on cytochrome oxidase subunit I (COI) showed intraspecific levels of genetic differentiation within Johnius of East Malaysia, which forms a monophyletic group. Moreover, the new record of Johnius trewavasae in East Malaysia represented that the distribution of the subtropical genus Johnius extended to the southernmost part of the tropical region.

Understanding the reproductive biology of fishes is crucial to making accurate and scientifically sound recommendations for fisheries management. The presently reported study is the first to report the reproductive characteristics of the data-deficient and recently described yellowfin snapper, Lutjanus xanthopinnis Iwatsuki, Tanaka et Allen, 2015, collected from the eastern South China Sea, Malaysia. A total of 572 fish specimens were sampled monthly from March 2022 to April 2023 using a gillnet and a trawl net. Subsequently, these specimens were measured and weighed. Their total length (TL) ranged from 15.3 to 26.8 cm (19.25 ± 2.04 cm; mean ± SD). Their body weight (W_B) ranged from 53.5 g to 279.7 g (114.5 ± 40.3 g; mean ± SD). For the reproductive biology study, the following parameters were determined: the sex ratio, gonadosomatic index (GSI), hepatosomatic index (HSI), spawning period, fecundity, condition factor (K), length at maturity, and the gonadal maturity stages. In the sex ratio, males (M) were significantly dominant over females (F) (M:F = 1:0.75) (χ² = 11.18). Consequently, the monthly mean GSI of pooled sex revealed a consistent trend from January to August, indicating spawning seasons with peak periods in March and April. The batch fecundity of 67 mature females (16.0–25.2 cm TL; 64.5– 279.3 g W), was determined to range from 16 405 to 94 357 oocytes. The fecundity increased with gonad weight in contrast to weight and length. The length at first maturity of females and males was 14.53 and 20.56 cm, respectively. Females matured earlier than males. Macroscopic and histological examination of gonads revealed monthly variation in the ratio of gonad stages for males and females. This study offers crucial data on the reproductive biology of L. xanthopinnis, which will help with sustainable fishery management in this area and can be used as a reference for the management of similar fish populations in other regions of the world.

A new species of Larimichthys from Terengganu, east coast of Peninsular Malaysia (Perciformes: Sciaenidae)