Ichthyological Research最新文献

A review of the validity of morphological traits defining the scorpionfish genus Parascorpaena Bleeker 1876 resulted in the re-identification of Parascorpaena bandanensis (Bleeker 1851) as Sebastapistes strongia (Cuvier 1829), reducing the number of valid species of Parascorpaena from nine to eight. A modified definition of Parascorpaena, based on morphological characters observed among the valid species, includes: usually complete lateral line, continuing onto the caudal-fin base; second to fifth or sixth pectoral-fin rays branched; usually two or three suborbital spines; body covered with cycloid scales; lower jaw slightly shorter than upper jaw; palatine teeth present; villiform teeth on upper jaw; distinct posterior lacrimal ridge instead of a developed spine; simple anterior and posterior lacrimal spines without additional spinous points; and a posterior lacrimal spine (PLS) oriented strongly forward, with smaller specimens exhibiting ventral orientation with anterior curvature, and those smaller than 20 mm standard length with the PLS oriented postero-ventrally. A concatenated phylogenetic tree constructed using mitochondrial cytochrome oxidase I (COI), 16S ribosomal ribonucleic acid (16S rRNA), and recombination activating gene 1 (RAG1) markers, demonstrated the monophyletic nature of Parascorpaena. In addition, molecular analysis placed Parascorpaena closer to a group represented by Sebastapistes mauritiana (Cuvier 1829) within the paraphyletic Sebastapistes Gill in Streets 1877.

Neotrygon yakkoei (Dasyatidae), a new species of bluespotted maskray from Japan, previously confused with Neotrygon kuhlii (Müller and Henle 1841) or Neotrygon orientalis Last, White and Séret 2016, is described on the basis of 35 specimens [146.4–425.2 mm disc width (DW)] from Japan. The new species is characterized by the following characteristics: greenish brown body in fresh with a single dark mask-like marking between eyes (often indistinct); fewer spots (mean 20.4 spots); small pale blue spots [its diameter 1.2–3.4% (mean 2.6%) of DW] surrounded by dark brown outer rings when fresh; and longer head length 35.9–43.4% (mean 39.1%) of DW. Molecular analysis based on 576 bp of partial COI mitochondrial gene also supports that N. yakkoei is a distinct species from all other congeners, except for Neotrygon vali Borsa 2017, which lacked genetic data. The new species is currently known only from Japan: Hokkaido (Japan Sea and Pacific sides), Wakasa Bay (Japan Sea), the Izu and Ogasawara islands, the Pacific coast of Japan from Sagami Bay to southern Kyushu, and the Osumi, Amami, Okinawa, and Yaeyama islands.

This study used histological techniques to investigate sexual patterns in the freckled hawkfish Paracirrhites forsteri, which has a mating system intermediate between harem and male-territory-visiting polygamy. Males on reefs in the area of Kuchierabu-jima Island tended to be larger than females, and one hermaphrodite with ovarian cavities was observed at a size intermediate between most males and females. These findings indicate a protogynous sexual pattern in the studied population. However, some males were smaller than females, with the smallest individual collected being a male. Furthermore, most individuals with a body size smaller than that typical of females exhibited bisexual gonads. These new findings suggest that prematurational sex change occurs in this species, whereby some males derive directly through sexual differentiation as juveniles. Our study represents the first report suggesting diandry in the Cirrhitidae.

This study investigated the reproductive behavior of the Kidako moray Gymnothorax kidako in Tateyama, Chiba, Japan and Enoshima Aquarium. Field observations on reproductive behavior were conducted for 19 pairs from 24 July to 23 August 2017, at depths from 13 m to 18 m. Among these pairs, two instances were observed where the male gripped the female’s snout in its mouth and rushed toward the water surface at 20:45 and 20:40. At Enoshima Aquarium on 8 August 2022, a male and a female spawned at 20:06 following similar behavior. These findings suggest that rushing is a pre-spawning behavior. Among the 19 pairs observed, males [80–100 cm in total length (TL)] were consistently larger than females (70–90 cm TL). However, a pair was interrupted when a small male, approximately 50 cm TL, rushed by gripping the female’s snout. This suggests that smaller males unable to establish pairs may participate in reproduction through sneaking.

One of the greatest challenges for researchers today is understanding climate-change impacts on fish populations, particularly in vulnerable and understudied ecosystems such as the Canadian Arctic. Among other impacts, northern fishes will undergo thermal stress as atmospheric and sea surface temperatures are projected to rise globally. Models that consider how both environmental factors such as temperature and potential species interactions will impact population extirpation and species’ range contraction can help project the future distribution of a species in the face of a warming climate. Here, we investigate the climate-change impacts of rising temperatures and the potential northward distributional shift of brook charr (Salvelinus fontinalis) on Arctic charr (Salvelinus alpinus), Canada’s northernmost freshwater fish species. Specifically, we used a logistic regression model to establish baseline relationships between the current distribution of Arctic charr and the variables, degree-days (a key climate variable), geographical location, and brook charr occurrence. We developed the model applying the expected changes in degree-days to 2050 (25–50% increase from the average of 1976–2005) and 2080 (50–100% increase) while incorporating the historical distribution of Arctic charr to estimate the change in Arctic charr distribution over that time. We found that growing degree-days, longitude, latitude, and brook charr occurrences correctly classified 93% of Arctic charr historical occurrences in Canada. We estimate that in a high-carbon scenario, where degree-days are expected to increase by 50 to 100%, Arctic charr range is projected to decrease by 18% in Canada by 2051–2080 and decrease even further by 3% with the presence of brook charr. The Canadian high Arctic may provide refuge for Arctic charr, likely maintaining temperatures optimal for species persistence. Regardless, management that considers the climate stresses on Arctic charr populations will be important to preserve this highly valued resource that is pivotal for food security and traditional ways of life for northerners.

Oryzias moramoensis, a new species of ricefish (Adrianichthyidae), is described from Moramo Waterfall, Regency of Konawe Selatan, Southeast Sulawesi Province, Indonesia. The new species is a member of the Oryzias woworae species group, which is endemic to southeastern Sulawesi and is distinguished by a bluish sheen on the body in live males. Oryzias moramoensis sp. nov. is distinguished from other species of the Oryzias woworae species group (i.e., Oryzias asinua Parenti, Hadiaty, Lumbantobing and Herder 2013, Oryzias wolasi Parenti, Hadiaty, Lumbantobing and Herder 2013 and Oryzias woworae Parenti and Hadiaty 2010) by the combination of the following characters: 8 transverse scales; head length 26.6%–27.7% of standard length (SL) in males, and 28.0%–28.9% of SL in females; body depth at anal-fin origin 24.3%–28.2% of SL in males, and 23.5%–24.0% of SL in females; scarce or no pigmentation along the ventral and dorsal margins of caudal fin of males after preservation. Principal component analysis based on genome-wide single nucleotide polymorphisms revealed that O. moramoensis is clearly separated from the other three species along the first principal component. We discuss why O. moramoensis is genetically isolated from the other members of the species group despite their close geographic proximity.

Water level fluctuations (WLFs) are generally regarded as the primary factor structuring the fish metacommunities in floodplain lakes, but their effects on fish taxonomic and functional diversity have been limited explored. Here, we asked how fish taxonomic and functional structures vary in response to different WLFs, and how environmental parameters influence fish metacommunity structures among different WLFs. Our results demonstrated significantly higher Richness, Pielou’ evenness, Shannon-Wiener index, functional richness, and functional evenness in high water phase, which was probably due to high fish recruitments originating from floodplain rivers. The high abundance of riverine gudgeons in high water phase confirmed the enhanced fish dispersal processes from rivers to floodplain lakes which were triggered by flood pulses. Compared to the scenario of high-water level, our results demonstrated significantly lower taxonomic and functional diversity during low water phase with more abundant generalist fish species. Such changes were probably triggered by enhanced environmental filtering during the low water phase, since we detected significantly intensified environmental loadings in low water level. Water temperature, conductivity, total nitrogen, and phosphate phosphorus were retained as significant predictors of fish taxonomic and functional structures across different water levels, which suggested that WLFs influenced fish assemblages through physicochemical changes. The present findings highlighted the importance of sustaining natural WLFs as well as seasonal floods in high water for the fish recruitments in floodplain lakes.

Near the southern limit of its Japanese distribution range, the white-spotted charr Salvelinus leucomaenis inhabits headwater tributaries of inlet rivers to Lake Biwa, Shiga Prefecture, although failing to migrate to the lake from those tributaries. Even though lower depths (>30 m) of the north basin of the lake are cold throughout the year, the only salmonid inhabiting the lake is the Biwa salmon Oncorhynchus sp. However, between 2018 and 2021, five white-spotted charr were caught in Lake Biwa, their phenotype being characterized by large whitish spots, reminiscent of the anadromous form off northern Japan. Mitochondrial DNA Cyt b haplotype analysis data supported their origin as hatchery-reared specimens from Samegai Trout Farm (Shiga Prefecture), the latter having sourced white-spotted charr from several Japanese populations, including northern Japan (descending anadromous exists). Such white-spotted charr, upon release from the hatchery, may have migrated to the lake during winter, due to a retained migration instinct.

Underwater cameras were used to record and describe, for the first time, the spawning behaviour of the lake charr (Salvelinus umbla) in an Alpine stream (Oberer Lunzer Seebach, Austria). The results were then compared with other Salvelinus species reported in the literature. Unlike other Salvelinus species, lake charr females do not perform the typical undulating behaviour intended to ventilate and distribute eggs over gravel crevices after the spawning act. This behavioural distinction reveals a different evolutionary history and supports the lake charr being conferred a species status. The Salvelinus species’ unique mode of spawning is discussed within an evolutionary framework.