Journal of Ichthyology最新文献

Abstract

On 21 February 2024, 12 neonate spurdogs (Squaliformes: Squalidae) were captured with a bottom trawl towed over a sandy-muddy bottom at depths of 121–126 m in the eastern sector of the Marmara Sea. Eleven out of 12 spurdogs were identified as Squalus blainville (Risso, 1827), but one of the spurdogs, specimen MD6-24-SquaSp, exhibited several characteristics of both S. blainville and S. megalops. The results of this study suggest two possibilities: (1) either S. blainville shows a significant degree of intraspecific variability, and therefore, there is a highly differentiated variety of S. blainville that may occur in the Marmara Sea, or (2) there is a yet undescribed species belonging to the S. megalops clade that occurs in the region. This uncertainty supports the need for a genetically based taxonomic revision of the species of the genus Squalus in the Marmara Sea.

Abstract

We analyzed the morphology and gonad structure of Variola albimarginata based on nine specimens (TL 28.2–44.5 cm) collected off Kuchierabu-jima Island, southern Japan. Individuals exceeding TL 40 cm were identified as males, with males significantly larger than females (max TL 33.3 cm). The testes of V. albimarginata all exhibited a central lumen, suggesting a remnant of the ovarian cavity. An individual of intermediate size (TL 37.8 cm), positioned between males and females, possessed a bisexual gonad characterized by the presence of primary oocytes, atretic oocytes, and spermatocytes. These findings suggest the possibility that V. albimarginata undergo protogynous sex change in their life history.

Abstract

Riverine hump-nosed whitefish was described as a new species Coregonus fluviatilis by Issatschenko in 1925 based on eight specimens from the middle Yenisei River basin. The further fate of these specimens is still unknown. At the same time, C. fluviatilis has been involved in various confusions related to its taxonomic position, type locality, distribution, diagnostic characters, and the identification of two forms under the same name. In this regard, in this paper, the neotype of C. fluviatilis (ZMMU P-24531) is designated in accordance with the conditions set out in Article 75.3 of the International Code of Zoological Nomenclature.

Abstract

The present study aimed to assess the feeding habits of Sebastes oculatus from the analysis of stomach content and to evaluate the influence of environmental and biological variables on occurrence of prey in stomach. Results showed that S. oculatus feeds mainly on the squat lobster Grimothea gregaria, crustacean megalopa, polychaetes and fish. The main factor that influenced occurrence of prey in stomach was the season and the importance of these prey items varied from season to season. The diet composition of S. oculatus gives clear evidence of its carcinophagous habits. The species feeds mostly on demersal and benthic invertebrates, but also on some pelagic fishes and crustaceans that live on the rocky reef. It allows assuming that S. oculatus is an ambush predator that does not actively search for its prey.

Abstract

Barramundi, or Asian seabass Lates calcarifer, is a commercially important food fish with a wide geographic distribution in the Indo-West Pacific region. Despite its economic significance, particularly in Taiwan, information on the sources of fertilized eggs, fry and stock management practices remains largely unavailable. To ensure sustainable exploitation and effective selective breeding programs, assessing the genetic diversity and population genetic structure of barramundi is crucial. This study investigated the genetic diversity and population genetic structure of three cultured populations (Chiayi A, Chiayi B, and Tainan) and one wild-caught population in Taiwan using mitochondrial DNA cytochrome b and eight microsatellite loci as genetic markers. The analysis of haplotype network revealed that all populations shared an ancestral haplotype, yet each population had its own unique haplotype. Notably, the wild and cultured populations showed the largest genetic distance. However, overall, the genetic distances among all populations were small and similar. This finding suggests potential gene exchange, possibly through broodstock exchange practices between farms. The valuable genetic information obtained from this study holds the potential to improve aquaculture programs through targeted breeding initiatives and inform the development of sustainable management policies for barramundi.

Environmental and ecological effects of the dam of the high-pressure Bratsk Hydroelectric Power Station (HPS) on the fish population and the probability of fish downstream migration from the Bratsk Reservoir have been studied. It has been revealed that thermal stratification of the water column is a significant factor in the ecological differentiation of the fish population in the upper reaches of high-pressure hydroelectric plants. According to hydroacoustics data, most of the ichthyomass, consisting of “warm-water” representatives of the Percidae (65%) and Cyprinidae (22%) families, is concentrated in the relatively warm layer of the epilimnion. Juvenile fish from 30 to 50 mm in size (up to 70% of the total fish number in this layer) are also concentrated here. In the cold-water hypolimnion, the fish population is represented by large single individuals of whitefish (Coregoninae). The data on distribution of fish in the lower and upper reaches of the dam, fish nutrition patterns, growth rate, and the presence of injuries that occur when fish pass downstream through hydroelectric plant dams are presented. Revealed differences in the growth rate of perches from the upper and lower reaches are associated with their constant inhabiting of water masses with contrasting temperatures. Net catches in the lower reaches over the four seasons of research lack injured individuals. These facts prove the absence of mass downstream passage of fish through the Bratsk HPS dam. Juveniles of cyprinids and perches accumulate in the upper warm layer of 0–10 m, i.e. outside the zone of the intake flow formation, which makes their entrance to intake openings at a depth of more than 20 m hardly possible.

Abstract

The first recorded case of leucism is reported in the Greenland halibut Reinhardtius hippoglossoides from the waters off the northeastern tip of Sakhalin Island. The caught individual, a sexually mature female with a fork length of 83 cm, had depigmentation over almost entire body. The only pigmented parts on the eyed side of the body were pupils, a small spot on the caudal fin, a spot around the pectoral fin, and a border of the gill slit.

Abstract

The results of studying the bathymetric and spatial distribution of the barred snailfish Crystallias matsushimae are presented according to bottom trawl surveys in the Russian waters of the Sea of Japan. The species does not form dense aggregations, although it is not as rare as was previously thought: in bottom trawl catches on the continental slope, the frequency of its occurrence is about 30%. The main areas of the species aggregations are the western part of the Peter the Great Gulf and the deep-water section of the Tatar Strait between the mainland and Sakhalin Island. Despite the relatively wide range of water temperature and depths at which the snailfish was found in catches, the species prefers rather narrow thermal and bathymetric ranges: 0.6–1.5°C and 200–500 m. Mysids, amphipods and decapods dominate in the diet.

Abstract

Scientific monitoring of pelagic fish stocks in 2004–2005 and 2014–2017 provided information on characteristics of sexual maturation of Atlantic chub mackerel Scomber colias in the coastal waters of the Central-Eastern Atlantic. Based on these results we describe ecological and geographical variability of some biological characteristics of the species. Features of sexual maturation of females and males of the mackerel can be described by a logistic equation obtained in the R programming environment. Fork length, at which 50% of individuals aged 1+ are mature, is 18.4 cm for females and 20.0 cm for males; 100% of individuals are mature at age 3+ with a fork length of 32.3 and 30.8 cm for females and males, respectively. A high proportion of spawning chub mackerel individuals in the Central-Eastern Atlantic have been recorded from February to March and from June to July. Chub mackerel in the coastal waters of this region are similar in life cycle characteristics to the populations of the waters off the Canary Islands and the Madeira Archipelago, but differ from the populations of the waters off mainland Portugal, the Azores, South Africa, and the Bay of Biscay in faster sexual maturation and growth rates.

Abstract—

A new species of family Melamphaidae is described from the central part of the Atlantic: Scopeloberyx shakhovskoyi. The species belongs to the oligorakered Scopeloberyx fishes (15–18 rakers on the first gill arch and pectoventral horizontal distance between the vertical lines of lower edge of the pectoral fin and the origin of ventral fin is less than 5% SL). The fish were caught at depths in a range of 700–0 m. Scopeloberyx nigrescens sensu Keene is proposed as synonymous to the new species.