Otolith microchemistry reveals diverse habitat uses and migratory patterns of two Coilia species (Engraulidae) in the Min River Estuary, southern China.

A recent study based on gonad histology revealed that the existence of the spawning grounds for Gray's grenadier anchovy (Coilia grayii) and Osbeck's grenadier anchovy (C. mystus) in the Min River Estuary, the largest in Fujian Province, southern China. Further confirming their natal sources and migratory patterns is essential to understand their life histories. We used otolith microchemistry to assess the origins and habitat uses of 23 C. grayii and 22 C. mystus, collected the Min River Estuary and the adjacent waters. The results showed that C. grayii spawned in both freshwater (n| = 14) and brackish water (n = 9), and C. mystus spawned mainly in brackish water (n| = 20) with minor in freshwater (n| = 1) and marine water (n| = 1). The migratory patterns of C. grayii (four types) and C. mystus (five types) were diverse, mainly exhibiting anadromous and semi-anadromous behaviors. The first migratory behavior of C. grayii and C. mystus occurred within the age of the first year. The findings have significant implications for fishery stock management of the Min River Estuary and its adjacent waters.

Littoral Water in Hong Kong as a Potential Transient Habitat for Juveniles of a Temperate Deepwater Gnomefish, Scombrops boops (Acropomatiformes: Scombropidae).

A total of 40 juveniles belonging to a temperate deepwater gnomefish species, Scombrops boops, were sampled from littoral habitats (2-5 m depth) of eastern Hong Kong waters in April and May 2017 and March 2019. The presence of gnomefish juveniles in subtropical southern China is reported for the first time at a record low latitude of 22°11'-22°21'N. The specimens were identified based on the COI gene sequence. The genetic composition between Japan and Hong Kong gnomefish populations were compared by sequencing the mitochondrial Cytb gene, which showed no genetic differentiation. The juveniles ranged from 3.5-10.1 cm (n = 40) in total length, with 35 individuals caught from Sargassum beds and five from rocky reefs. Our findings highlighted that the littoral habitats in Hong Kong waters, in particular the seasonal Sargassum beds, are important for small juveniles of S. boops.

Complete mitochondrial genome and the phylogenetic position of a new species, Johnius taiwanensis (Perciformes: Sciaenidae) from Chinese waters.

In this study, the complete mitogenome of a new species, Johnius taiwanensis (Chao et al. 2019) was obtained. Its mitogenome is 18,451 bp in length, consisting of 37 genes with the typical gene order and direction of transcription in vertebrates. Gene rearrangement was found in J. taiwanensis. The overall nucleotide composition is: 24.2% A; 18.0% C; 21.1% G, and 36.7% T. Sizes of the 22 tRNA genes range from 66 to 75 bp. Two start codons (ATG and GTG) and three stop codons (TAG, AGA and TAA/TA/T) were detected in 13 protein-coding genes. In the Bayesian tree based on the complete mitogenomes of 26 species (including J. taiwanensis) from the family Sciaenidae, all nodes were strongly supported. The result shows that J. taiwanensis was placed as sister to the Trewavas croaker J. trewavasae of the same genus. The mechanism of gene rearrangement in the genus Johnius merits further investigation.

Johnius taiwanensis, a new species of Sciaenidae from the Taiwan Strait, with a key to Johnius species from Chinese waters.

A new sciaenid fish, Johnius taiwanensis, is described from the southeast coast of mainland China from Zhejiang to Guangdong, Hong Kong, and west coast of Taiwan. Johnius taiwanensis sp. nov. can be distinguished from other Johnius species by having a grayish dorsal half of body divided by a clear line from a whitish ventral half, and a black spot at the dorsal half of pectoral-fin axil, appearing as a distinct dot at the most dorsal point of the pectoral-fin base. First dorsal fin black tipped, other fins pale to dusky but never darkly pigmented. The species lacks distinctly enlarged teeth on upper and lower jaws. Body scales ctenoid, moderately large, with five or six rows between first dorsal-fin origin and lateral line. It is one of the most abundant sciaenids found in the shallow coastal waters (20 m) of southeast mainland China and the west coast of Taiwan. It has often been misidentified as J. macrorhynus in the region. Phylogenetic analysis from all 27 sciaenid species found in Chinese waters based on the complete COI and 16S rRNA gene sequences confirmed that the genus Johnius is monophyletic and J. taiwanensis is placed as a sister species of J. trewavasae. Acoustic analysis has shown that J. taiwanensis produces a unique sound among fishes in Taiwan coastal waters.

Complete mitochondrial genome and the phylogenetic position of the Pawak croaker Pennahia pawak (Perciformes: Sciaenidae).

In this study, the complete mitogenome of the Pawak croaker Pennahia pawak was first determined. This mitogenome is 16,408 bp in length, and consists of 37 genes with the typical gene order and direction of transcription in vertebrates. The overall nucleotide composition is: 27.7% A, 29.5% C, 15.9% G, and 26.9% T. Sizes of the 22 tRNA genes range from 66 to 75 bp. One start codons (ATG) and two stop codons (AGA and TAA/TA/T) were detected in 13 protein-coding genes. In the Bayesian tree based on the complete mitogenomes of 17 species (including P. pawak) from the family Sciaenidae, all nodes were strongly supported. The phylogenetic results suggested that P. pawak has the closest relationship to the silver croaker P. argentata, a species from the same genus.