Showing papers in "Ichthyological Research in 2017"
TL;DR: All anaesthetics showed similar efficacy and blood parameters were normalized within 24 to 48 h, as confirmed by the lack of an adrenergic response of RBC in vitro.
Abstract: Fish anaesthesia is used to minimize handling stress and damage during harvesting, transportation, and surgical procedures. Through depression of cardiovascular and respiratory functions, it causes significant changes in blood gases and pH. Here, we present the effects of benzocaine (100 mg l−1), MS-222 (100 mg l−1), and Aqui-S (30 mg l−1) on blood gases and haematological parameters of commercial-sized (≈1 kg) striped catfish (Pangasianodon hypophthalmus) and the time course of recovery. Blood was taken through a dorsal aorta catheter immediately after catheterization, and regularly during the following 72 h recovery in aerated water. All anaesthetics caused increases in PCO2 and lactate resulting in a decrease in pHe, closely mirrored by RBC pHi, as well as a marked rise in Hct, associated with elevated [cortisol] and [glucose] and increased RBC counts but no change in RBC volume, as confirmed by the lack of an adrenergic response of RBC in vitro. All anaesthetics showed similar efficacy and blood parameters were normalized within 24 to 48 h.
20 citations
TL;DR: Lagocephalus gloveri Abe and Tabeta 1983 is shown to be a junior synonym of Tetrodon cheesemanii Clarke 1897 based on examination of morphological characters and DNA analysis of specimens collected from the western North Pacific, Australia and New Zealand.
Abstract: Lagocephalus gloveri Abe and Tabeta 1983 is shown to be a junior synonym of Tetrodon cheesemanii Clarke 1897 based on examination of morphological characters and DNA analysis of specimens collected from the western North Pacific, Australia and New Zealand. Lagocephalus cheesemanii is distinguished from other species of Lagocephalus by the following combination of characters: spinules on the back in a rhomboidal patch extending from the region between the nasal organ to the posterior part of the pectoral fin; caudal fin double emarginate with middle rays posteriorly produced; dorsal-fin rays 11–15; anal-fin rays 11–14; pectoral-fin rays 15–18; vertebrae 8+11=19; dorsal half of the body dark brown to brownish black; caudal fin dark brown to black with dorsal and ventral white tips. A neotype of L. cheesemanii is designated.
16 citations
TL;DR: The diet evenness index and Costello graphic analysis indicate that the burrowing fish Parapocryptes serperaster is a generalist feeder and feeds mainly on detritus, followed by diatoms, and could obtain food from the bottom and the water column.
Abstract: Diet composition and feeding habits of the burrowing fish Parapocryptes serperaster were investigated on different fish sizes across dry and wet seasons in the Mekong Delta, Vietnam The gut length was positively related to fish length; the gut length was 157 ± 030 times the total length, which is in the range for omnivore (1–3) Detritus, algae and copepods were the main food items in the foregut The diet composition showed seasonal and intraspecific variations in all fish sizes The diet diversity varied with fish size and the dry-wet season pattern, and small fish had a higher diet diversity than large fish The diet evenness index and Costello graphic analysis indicate that this goby is a generalist feeder and feeds mainly on detritus, followed by diatoms, and could obtain food from the bottom and the water column The feeding intensity of P serperaster was higher in the wet season than in the dry season, but was not significantly affected by fish size The P serperaster fed on Navicula spp in the wet season, but on Nitzschia spp in the dry season The understanding of food and feeding habits of P serperaster contributes to our knowledge on feeding adaptation of small-bodied bottom-dwelling gobies to the mud flat habitats in tropical monsoonal regions
15 citations
TL;DR: The lateral line system and its innervation were examined in a generalized perch-like species, Lateolabrax japonicus, and compared with those in two species of Apogonidae characterized by proliferated superficial neuromasts (SNs) on the head, trunk lateral line scales and caudal fin.
Abstract: The lateral line system and its innervation were examined in a generalized perch-like species, Lateolabrax japonicus (Percoidei incertae sedis), and compared with those in two species of Apogonidae (Fowleria variegata in Apogonichthyini and Ostorhinchus doederleini in Ostorhinchini) characterized by proliferated superficial neuromasts (SNs) on the head, trunk lateral line scales and caudal fin. The total number of SNs differed greatly between the two groups, being 271 in the former, and 2,403 and 4,088 in the latter. The mandibular ramus (MDR) was extensively ramified in the head of the apogonids, with three additional branches that were absent in L. japonicus, innervating 1,117 SNs in F. variegata and 1,928 in O. doederleini. In the apogonids, the additional anterodorsal branch of the MDR coursed parallel to the buccal ramus anteriorly (on the interorbital space) and to the supratemporal ramus posteriorly (on the temporal region). The two parallel portions supplied numerous SN rows forming a characteristic crosshatch pattern, the branch and two rami distributing to transverse and longitudinal rows, respectively. In the two groups, the trunk lateral line scales each housed a canal neuromast (CN; partly replaced by an SN in F. variegata). In addition, one to four (in L. japonicus) and three to 55 (in the apogonids) SNs occurred on each lateral line scale, the pattern of SN innervation being identical in having two types of branches; one innervated a CN and SNs, and the other SN(s) only. The latter type extended only to a limited number of scales in L. japonicus, but to nearly all or all scales in the apogonids. Compared with F. variegata, branches of the respective types were more finely ramified with greater number of SNs in O. doederleini.
15 citations
TL;DR: Round goby Neogobius melanostomus, initially originating from the Ponto-Caspian region, has become one of the most successful invasive species in the Northern Hemisphere and has proved to have impact on native fish populations in several invaded regions.
Abstract: Round goby Neogobius melanostomus, initially originating from the Ponto-Caspian region, has become one of the most successful invasive species in the Northern Hemisphere. During the last three decades, this invasive fish has established numerous populations both in Eurasia and North America (reviewed in Kornis et al. 2012). In Europe, this species has invaded lakes, large rivers and also various marine environments. In Northern America, round goby has started to spread from lakes to several estuaries, marshes and smaller tributaries (Poos et al. 2010; Kornis et al. 2012). High tolerance to various environmental factors, short generation time, opportunistic diet preferences and aggressive behaviour allows this species to colonize different biotopes (Corkum et al. 2004; Johnson et al. 2005; Brown and Stepien 2008; Kornis et al. 2014). Rapid invasion of round goby has proved to have impact on native fish populations in several invaded regions. Declines in abundance of some benthic fishes as stone loach Barbatula barbatula, bullhead Cottus gobio and white-finned gudgeon Romanogobio albipinnatus have been suggested in European freshwaters (Jurajda et al. 2005). In the Baltic Sea, the expansion of round goby has been suggested to affect flounder Platichthys flesus, eelpout Zoarces viviparus and native gobies (Balážová-L’avrincı́ková and Kovác 2007; Karlson et al. 2007). In North America, several percid and cottid species compete with round goby for food, territory and spawning grounds (Jude et al. 1995; Janssen and Jude 2001). Round goby invasion to the Baltic Sea was confirmed in 1990, when several fish were caught from Puck Bay in Poland (Skóra and Stolarski 1993). In the Estonian coastal sea, round goby was found in 2002, from Pärnu Bay in the Gulf of Riga (Shpilev and Ojaveer 2003). However, first rapidly growing population occurred during the mid-2000s in Muuga Bay near Tallinn, in the southern coast of the Gulf of Finland (Ojaveer 2006). During the 2010s, round goby dispersed widely along the southern coast of Gulf of Finland and became particularly abundant in several small bays east of Tallinn. Since 2011, the round gobies were found from six salmonid spawning streams along the North Estonian coast (Fig. 1). Fishes were caught during the national annual salmonid parr density survey, using backpack electrofishing gear. Study sites (two or three per stream) were located in rapid sections situated on the lower reaches of the streams which are accessible to anadromous salmonids. All sites were fished twice and the interval between sampling runs was at least 30 minutes. The abundance of salmonids and all other fish species were recorded, all caught fish were measured to the nearest mm (total length), kept in water buckets and released afterwards (except round gobies). Based on the maximum summer water temperatures, streams were classified as cool (13.1–17.0 C; three locations) or temperate (17.1–21.0 C; three locations) (Järvekülg 2001). The length of the streams varied between 25 and 85 km, catchment areas between 84–479 km and mean discharges in lower reaches between 0.5–4.0 m/s (Loopmann 1979) [Electronic Supplementary Material (ESM) Table S1]. All the studied sites were located in freshwater, and distances along a stream from the sea varied from 0.5 to 2.6 km. In three streams, where round Electronic supplementary material The online version of this article (doi:10.1007/s10228-016-0537-4) contains supplementary material, which is available to authorized users.
15 citations
TL;DR: Despite the morphological similarity between the two species, an obvious genetic difference was observed between D. hemprichi and D. brachypterus.
Abstract: A taxonomic review of the Dendrochirus brachypterus complex resulted in the recognition of five species, including Dendrochirus barberi (Steindachner 1900), Dendrochirus bellus (Jordan and Hubbs 1925), Dendrochirus brachypterus (Cuvier in Cuvier and Valenciennes 1829), Dendrochirus hemprichi sp. nov. and Dendrochirus tuamotuensis Matsunuma and Motomura 2013. The complex is defined as having usually 9 dorsal-fin soft rays, usually 5 anal-fin soft rays, 17–20 (rarely 20) pectoral-fin rays, no ocellated spots on the soft-rayed portion of the dorsal fin and usually 2 (sometimes none) barbels on the snout tip. Dendrochirus barberi, known from the Hawaiian Islands and Johnston Atoll, is characterized by usually 18 pectoral-fin rays, a relatively high number of scale rows in the longitudinal series (modally 51 vs. 39–49 in other species) and mottled markings on the pectoral fin in large specimens. Dendrochirus bellus, restricted to the northwestern Pacific Ocean from the South China Sea north to southern Japan, is characterized by usually 17 pectoral-fin rays, a relatively low number of scale rows in the longitudinal series (modally 38 vs. 44–51 in other species), and the absence of skin flaps on the orbit surface and uppermost preopercular spine base. Dendrochirus tuamotuensis, recorded only from the Tuamotu Archipelago, is characterized by 19 pectoral-fin rays, the posterior margin of the pectoral fin strongly notched, and a relatively shallow and narrow head and body. Dendrochirus hemprichi sp. nov. is distributed in the western Indian Ocean, including the Red Sea. Although previously confused with a closely related congener (D. brachypterus, known from the northern and eastern Indian Ocean and western Pacific), D. hemprichi can be distinguished from the former by having fewer scale rows between the last dorsal-fin spine base and lateral line, and between the sixth dorsal-fin spine base and lateral line [4–7 (5) in D. hemprichi vs. 5–7 (6) in D. brachypterus, in both cases], a slightly greater interorbital width at the mid-orbit [5.5–10.7 (mean 7.8) % SL vs. 4.5–8.9 (6.8) % of SL] and at preocular spine base [4.4–9.1 (6.6) % SL vs. 3.5–7.8 (5.7) % of SL], and slightly shorter posteriormost (usually 13th) dorsal-fin spine length [11.8–19.9 (15.3) % SL vs. 13.3–21.3 (17.2) % of SL]. Moreover, D. hemprichi tends to have relatively more spinous points on the head spines and ridges, compared with D. brachypterus. Notwithstanding the morphological similarity between the two species, an obvious genetic difference was observed between D. hemprichi and D. brachypterus. Dendrochirus chloreus Jenkins 1903 and Dendrochirus hudsoni Jordan and Evermann 1903 were synonymized under Pterois barberi, as in some previous studies. Scorpaena koenigii Bloch 1789 was regarded as conspecific with D. brachypterus, which it predated. However, the former name should be suppressed under Reversal of Precedence.
14 citations
TL;DR: To conserve the native genetic diversity of the medaka species complex, further introduction of himedaka should be prevented by educating the public about the current status and risks of introducing non-native medaka varieties into the wild.
Abstract: We revealed the range and current status of genetic disturbances in wild medaka populations (Oryzias latipes species complex) using two DNA markers (cytb gene and b-marker). Genetic disturbances were detected in many wild populations throughout Japan and were primarily caused by artificial introduction of the commercial medaka variety, himedaka. We identified native medaka populations without introgressions, which may be significant conservation targets. To conserve the native genetic diversity of the medaka species complex, further introduction of himedaka should be prevented by educating the public about the current status and risks of introducing non-native medaka varieties into the wild.
11 citations
TL;DR: Investigation of the age-based demography of the orange-striped emperor from commercial samples in the Commonwealth of the Northern Mariana Islands suggests the species spawns every lunar cycle throughout the year with spawning activity potentially increasing around the new moon.
Abstract: The present study investigated the age-based demography of the orange-striped emperor, Lethrinus obsoletus, from commercial samples in the Commonwealth of the Northern Mariana Islands (CNMI), spanning a 24-month market sampling period. Information on growth, life span, mortality, and reproduction was derived through analysis of sectioned sagittal otoliths and gonad material. The species had a moderate longevity of 13 years while females and males reached 50% sexual maturity at 3.8 years (22.9 cm fork length) and 2.8 years (19.9 cm fork length), respectively. Histological examination of gonads and sex-specific age frequency distributions suggest the sexual ontogeny of the species conforms to juvenile hermaphroditism, whereby sexual transition from female to male occurred prior to maturation. No annual spawning periods were identified, but the ubiquitous presence of post-ovulatory follicles in females and spermatogenic material in males coupled with a consistent lunar trend in gonadosomatic index patterns suggests the species spawns every lunar cycle throughout the year with spawning activity potentially increasing around the new moon. Ratios of natural to fishing mortality indicate a moderate level of exploitation (0.37); however, a large portion of harvested females had not reached reproductive maturity, suggesting that formal assessments of stock status are warranted to ensure the sustainable harvest of the species in CNMI.
11 citations
TL;DR: Results directly indicated premeiotic endomitosis as a mechanism underlying the formation of unreduced eggs in allopolyploid females of Cobitis.
Abstract: Diploid and triploid hybrid females of Cobitis as a rule produce unreduced eggs which mainly develop gynogenetically, but some of the eggs incorporate sperm genome and develop into triploids and tetraploids, respectively. Here, we observed for the first time the meiotic chromosomes in the germinal vesicles (GVs) of mature oocytes of three diploid C. taenia (2n = 48) and 20 allopolyploid females of Cobitis (18 triploid 3n = 74 and 2 tetraploid 4n = 99). The majority of GVs in diploid, triploid and tetraploid females contained 24, 74 and 96 or 99 bivalents, respectively. These results directly indicated premeiotic endomitosis as a mechanism underlying the formation of unreduced eggs in allopolyploid females of Cobitis.
10 citations
TL;DR: A phylogenetic analysis of a group of morphologically similar and phylogenetically related ponyfishes (Perciformes: Leiognathidae) establishes the Equulites elongatus species group comprising three valid species as discussed by the authors.
Abstract: Taxonomic analysis of a group of morphologically similar and phylogenetically related ponyfishes (Perciformes: Leiognathidae) establishes the Equulites elongatus species group comprising three valid species: Equulites aethopos sp. nov., currently known only from southern Red Sea; Equulites elongatus (Gunther 1874), known from northern Australia, Indonesia and Myanmar; and Equulites popei (Whitley 1932), known from Japan, Philippines, Malaysia (Sabah), Thailand (Gulf of Thailand), Oman, the Red Sea, and Mozambique. Although E. popei has previously been regarded as a junior synonym of E. elongatus, the present mitochondrial DNA analysis revealed that these two nominal species are different and that they constitute a monophyletic group separate from other species of Equulites. The E. elongatus species group can be defined by the following of characters: slender body (20–30% in standard length), deeply incised posterior margin of the adipose eyelid, and ventral surface of breast completely scaly. Equulites aethopos sp. nov. differs from the other two species in having smaller eyes (eye diameter 53–68% of postorbital head length vs. 78–137%) and tips of neural and hemal spines of the fourth preural centrum distinctly expanding (vs. slightly expanding). Equulites elongatus is distinguished from E. popei by: scales above and below the lateral line 5–9 and 9–14, respectively (vs. 8–13 and 12–19), anus anteriorly located (distance from the pelvic-fin insertion to the center of anus 30–42% of the distance from the pelvic-fin insertion to the anal-fin origin vs. 35–50%), and more numerous dorsolateral dark marks (1–9 ring marks and 0–14 dark spots smaller than a half of pupil diameter vs. 0–2 and 0–5).
10 citations
TL;DR: It is demonstrated that invasive rainbow trout Oncorhynchus mykiss immigrated to and extremely aggregated in small tributaries during the winter, which can be utilized for effective population control.
Abstract: Because of their high economic and recreational value, salmonids have been extensively introduced worldwide and are responsible for significant impacts on native ecosystems. However, effective methods for controlling or eradicating introduced populations of salmonids are still limited, particularly in large river systems. Here, we demonstrated that invasive rainbow trout Oncorhynchus mykiss immigrated to and extremely aggregated in small tributaries during the winter, which can be utilized for effective population control. Seasonal census was conducted in 10 small tributaries of the Otofuke River in the Tokachi River basin, central Hokkaido, Japan. Winter abundance was 8–125 times higher than summer abundance in four of the tributaries where water velocities were low. Relatively large individuals (200–350 mm) aggregated in several pools at an unusually high density (>2–3 individuals/m2 or 170–440 individuals per pool). Females were common in the small tributaries in the winter, but not in the summer. Therefore, removal of invasive rainbow trout may be best practised in such small tributaries during early winter. Because many stream fishes overwinter in specific, often limited, habitats, more attention should be paid to such winter habits in the effective management of non-native fish species.
TL;DR: A taxonomic review of the genus Banjos revealed that a population from the southeastern Indian Ocean, including Indonesia and western Australia, is regarded as a distinct subspecies, distinguishable from B. b.
Abstract: A taxonomic review of the genus Banjos (Perciformes: Banjosidae), previously restricted to a single species, Banjos banjos (Richardson 1846), recorded from the northwestern Pacific Ocean from the South China Sea north to Japan, as well as Lombok (Indonesia), New Caledonia and Australia, resulted in the recognition of three species, including B. banjos (northwestern Pacific Ocean, Indonesia and western Australia), Banjos aculeatus sp. nov. (eastern Australia) and Banjos peregrinus sp. nov. [northern Australia (Timor Sea)]. Records of B. banjos from New Caledonia probably also represent B. aculeatus, which is clearly distinct from other congeners in having a relatively long, strongly serrated spine at the posteroventral angle of the preopercle and an entirely dusky membrane on the spinous dorsal fin in juveniles < ca. 70 mm SL, in addition to slightly longer first and second dorsal-fin spines. Banjos peregrinus is characterized by a relatively greater head length, orbit diameter, postorbital length and pre-pelvic-fin length, as well as poorly developed serration of the exposed margin of the cleithrum. Within B. banjos, a population from the southeastern Indian Ocean, including Indonesia and western Australia, is regarded as a distinct subspecies (Banjos banjos brevispinis ssp. nov.), distinguishable from B. b. banjos from the northwestern Pacific Ocean by a relatively narrow least interorbital width, and shorter second and eighth dorsal-fin spines. Ontogenetic morphological changes within the genus and the status of the holotype of Anoplus banjos Richardson 1846 are discussed in detail.
TL;DR: Shitamitsu et al. as mentioned in this paper performed histological analysis on the gonads of two creediid fishes, L. fasciatus and L. nitidus, to confirm functional hermaphroditism.
Abstract: Fishes of the family Creediidae occur mainly on the sandy bottom of tropical and temperate shallow waters in IndoWest Pacific Ocean. Eight genera and 18 valid species are known (Fricke and Golani 2012; Nelson et al. 2016). For ecological information, Leis (1982) and Reader et al. (2000) describe egg and larval development of Limnichthys fasciatus and Limnichthys nitidus, respectively. Cozzi and Clark (1995) report darting behavior, exhibited by L. nitidus as quick movements out and back in the sand, suggesting that it was an escape behavior when they were disturbed. Biological information on the reproduction of Creediidae has been very limited. Langston (2004) histologically studied the sexuality of 10 species of creediids and showed that Crystallodytes cookei and L. nitidus, identified as Limnichthys donaldsoni in the original paper, which is a junior synonym of L. nitidus (see Yoshino et al. 1999; Shimada 2013), are regarded as protandry (sex change from male to female) by histological observation of gonads and size distributions of both sexes (female [ male). In addition to these two species, Chalixodytes tauensis, Crystallodytes pauciradiatus and L. fasciatus have gonads comprising ovarian and testicular parts divided by connective tissue in functional males, whereas those of females consist of only the ovarian part. Sadovy de Mitcheson and Liu (2008) indicate that functional hermaphroditism is confirmed in 27 families of teleost fishes in their review on hermaphrodite fishes. However, Creediidae is not included among these families; namely, hermaphroditism of Creediidae has been overlooked for a long time. To provide evidential data of functional hermaphroditism, we made histological observations on gonads of the two creediid fishes L. fasciatus and L. nitidus. Forty-two specimens of L. fasciatus were collected by a hand net using SCUBA at Banda Beach, Tateyama, Chiba, Japan (34 580 N, 139 460 E) on 13 April (n = 1), 14–15 May (n = 7), 17 June (n = 9), 18–16 July (n = 13) and 18–21 August (n = 12), 2013. The fish were brought to the laboratory, anesthetized in 100 ppm MS-222, measured for standard length (SL) to the nearest 0.1 mm with a digital caliper, fixed in Bouin’s solution for 24 hours, and then preserved in 70 % ethanol. The abdominal parts of the specimens were embedded in paraffin, sectioned to 5 lm, and stained with hematoxylin and eosin. We also examined gonads of seven L. nitidus specimens deposited at the National Science Museum, Tokyo: NSMT–P 71438 (n = 4, 16.0–20.5 mm SL, collected at Ambon Isl., Indonesia on 5 December 1998) and NSMT–P 77532 (n = 3, 14.9–26.8 mm SL, Okinoshima Isl., Kochi, Japan on 24 July 2007). We dissected and extracted the abdominal organs containing the gonads and prepared the tissues following the methods outlined above. The gonads of 21 specimens of L. fasciatus comprised both testis and ovary (Fig. 1a), which were apparently divided by connective tissue. The oocytes of all 21 hermaphroditic specimens were immature, while the testicular parts of seven specimens collected in July and August were & Toshiaki Shitamitsu shitamitsu@affrc.go.jp
TL;DR: Analysis based on generalized linear models identified two specific partners for each goby and suggested that Apocryptodon punctatus frequently coexisted with partners and showed similar habitats, suggesting that this goby might be an obligate mutualist.
Abstract: We collected two gobies, Apocryptodon punctatus and Acentrogobius sp. A, and four alpheid shrimps from an estuary in southern Japan, to identify the symbiotic shrimps with gobies and to understand their partner specificity and dependency. Analysis based on generalized linear models identified two specific partners for each goby. A. punctatus frequently coexisted with partners and showed similar habitats, suggesting that this goby might be an obligate mutualist. Acentrogobius sp. A had lower rates of coexistence and appeared in habitats different from one of its partners, suggesting that this goby might be a facultative mutualist.
TL;DR: Examination of the holotypes of two nominal species, Encrasicholina heteroloba and E. devisi, was revealed to represent a single species, E. pseudoheteroloba, which is in fact a valid species in its own right and is elevated accordingly.
Abstract: Examination of the holotypes of two nominal species, Encrasicholina heteroloba (Ruppell 1837) and E. devisi (Whitley 1940), both previously recognized as valid species, was revealed to represent a single species. Accordingly, E. heteroloba is regarded as a senior synonym of E. devisi. Encrasicholina pseudoheteroloba (Hardenberg 1933), previously regarded as a junior synonym of E. heteroloba, is in fact a valid species in its own right and is therefore elevated accordingly. Encrasicholina heteroloba is distinguished from its congeners by a long upper jaw (posterior tip extending beyond the posterior margin of the preopercle), three unbranched rays in the dorsal and anal fins, and a shorter relative head length (24.9–28.9 % of standard length). Encrasicholina pseudoheteroloba differs from its congeners in having a long upper jaw (posterior tip extending beyond the posterior margin of the preopercle) and two unbranched rays in the dorsal and anal fins. A neotype is designated for E. pseudoheteroloba.
TL;DR: It is suggested that Lake Uchiumi, where the physical environment is characterized by lower temperature and salinity than in Sumiyo Bay, would be suitable as a nursery ground for this fish, especially for earlier developmental-staged larvae.
Abstract: We examined monthly occurrence patterns and feeding habits of larvae and juveniles of the critically endangered Ryukyu-ayu Plecoglossus altivelis ryukyuensis in the lower reach of the Kawauchi River, Amami-oshima Island, southern Japan, for two successive years. The study area was classified into a brackish lake (Lake Uchiumi) and a coastal zone (Sumiyo Bay) based on monthly variations in water temperature and salinity. Larvae and juveniles occurred from December to April in the first year and from January to February in the second year, respectively. Smaller-sized and earlier developmental-staged P. altivelis ryukyuensis individuals tended to emerge in larger numbers in Lake Uchiumi than in Sumiyo Bay. The present data suggest that Lake Uchiumi, where the physical environment is characterized by lower temperature and salinity than in Sumiyo Bay, would be suitable as a nursery ground for this fish, especially for earlier developmental-staged larvae. No individuals ≥25.0 mm body length, which is the size at which they begin their upstream migration, occurred in Lake Uchiumi or Sumiyo Bay in April or May, when upstream migration is assumed to reach a peak based on previous studies, in either year. The peak of upstream migration, therefore, may have occurred several months earlier in the years covered in this study due to higher water temperature than in typical years. To assess the feeding habits of this fish, the gut contents were observed. In both areas, copepods were abundant in P. altivelis ryukyuensis diet with calanoids and Oithona spp. being the most abundant. The diet composition differed between Lake Uchiumi and Sumiyo Bay and clearer ontogenetic variation in the composition of the diet was observed in Lake Uchiumi. Small individuals fed on tintinnid ciliates, but the proportion of these organisms in the diet gradually decreased with growth. Large individuals fed exclusively on harpacticoid copepods and insects including demersal species. Overall, larval and juvenile P. altivelis ryukyuensis exhibited a generalist feeding habit that tended to increase with growth. It is indispensable to adequately manage the environmental conditions in the lower reach of the Kawauchi River, especially Lake Uchiumi, to conserve P. altivelis ryukyuensis population.
TL;DR: Results clearly indicate sexual dimorphism in fin size and dichromatism in P. titteya, which suggests that this species has a high potential use as a model for studying sexual selection.
Abstract: We documented sexual dimorphism and dichromatism in the cyprinid fish Puntius titteya. We observed no sexual difference in body size, although males had longer fins than females. Male body coloration was redder and exhibited a higher saturation than that of females. However, in females, coloration in the cheek (around the gill cover) was near red and exhibited high saturation compared to coloration of the abdomen. These results clearly indicate sexual dimorphism in fin size and dichromatism in P. titteya, which suggests that this species has a high potential use as a model for studying sexual selection.
TL;DR: Morphometric and pigmentation characters of larvae from the two estuaries differed, suggesting that Lateolabrax of northern Vietnam are diversified and consist of at least two different breeding stocks.
Abstract: Lateolabrax sp. larvae were collected in the Tien Yen and Kalong estuaries of northern Vietnam, the southernmost locality for this genus distribution. Vietnamese Lateolabrax sp. larvae could be distinguished from those of L. japonicus by pigmentation patterns. Their morphological, meristic and pigmentation characters were closer to those of Chinese Lateolabrax than L. japonicus, so Vietnamese Lateolabrax is likely situated as a population of the Chinese one. Morphometric and pigmentation characters of larvae from the two estuaries differed, suggesting that Lateolabrax of northern Vietnam are diversified and consist of at least two different breeding stocks.
TL;DR: Verulux solmaculata sp.
Abstract: Verulux solmaculata sp. nov., a new cardinalfish based on 88 specimens collected from Papua New Guinea and Australia, differs from V. cypselurus, the only other known member of the genus, by the following characters: higher modal numbers of pectoral fin-rays (16 vs. 15 in the latter) and developed gill rakers (14 vs. 13), a broader black band extending over 3–5 (mode 4) rays on each lobe of the caudal fin (vs. 1–3, mode 2), and a black blotch on the caudal-fin base (vs. blotch absent).
TL;DR: The morphology and behavior of larval and early juvenile S. aequifasciatus exhibit adaptations for mucus provisioning, and their thick lips may be advantageous for removing mucus from the bodies of the parent fish.
Abstract: We observed the growth, morphological changes, and behavior of larvae and juveniles of the Amazonian substrate-brooding cichlid discus fish Symphysodon aequifasciatus under laboratory conditions. The mean body length (BL) of newly hatched larvae was 3.4–3.5 mm, and the yolksac extended to approximately 42 % of their BL. Larvae detached from the substrate on day 4 began swimming and immediately displayed biting behavior on the body surface of the parents. Larvae had completely consumed their yolksacs by day 7. They began swimming at an earlier developmental stage compared with other cichlid species. Their thick lips may be advantageous for removing mucus from the bodies of the parent fish. Juveniles actively fed on Artemia spp. by day 30, and the frequency of biting behavior toward the parents decreased between days 20 and 35. Bone ossification was essentially complete in juveniles by day 32. Juveniles reached 16.0 ± 1.1 mm BL by day 35. These results indicate that the morphology and behavior of larval and early juvenile S. aequifasciatus exhibit adaptations for mucus provisioning.
TL;DR: The endemic lentic goby of Lake Biwa in Japan, which has hitherto been designated informally as Rhinogobius sp.
Abstract: The endemic lentic goby of Lake Biwa in Japan, which has hitherto been designated informally as Rhinogobius sp. BW, is formally described as Rhinogobius biwaensis sp. nov. It is distinguished from other members of the genus by the following combination of characters: vertebral count 26 (rarely 27); pectoral fin rays 18–22 (mostly 20–21); longitudinal scales 31–36 (mostly 31–34, mode 32); predorsal scales absent or few; D1 low with non-filamentous spines, all of almost same length except for shorter 1st and 6th (last) spines in both sexes; pelvic fin disk composed of thin membranes, its frenum undeveloped with a low, thin lamella; cheek unmarked; back and sides of body with 5–6 unclear dark saddles and 6–9 dark blotches; D1 lacking blotches but melanized to greater or lesser degree along rays; dorsal edge of pectoral base with one small, dark spot tinged with blue metallic luster; in breeding males, yellow on suboperculum and branchiostegal region and on basal part of anal fin, blue on medial part of under jaw.
TL;DR: The new generic name Nemoossis is proposed for the albulid species Pterothrissus belloci Cadenat 1937, a species endemic to the eastern Atlantic Ocean that differs from other genera in the family Albulidae.
Abstract: The new generic name Nemoossis is proposed for the albulid species Pterothrissus belloci Cadenat 1937, a species endemic to the eastern Atlantic Ocean. Nemoossis differs from other genera in the family Albulidae as follows: longer dorsal-fin base, absence of supraneural bones, dorsal-fin rays [51–57 (mode 52)], vertebrae [total number 88–92 (91)], pored lateral-line scales [79–89 (84)], pre-dorsal-fin scale rows [3–8 (8)], head length [24–32 % (mean 30 %) of SL], pectoral-fin length [16–21 % (19 %) of SL], pre-dorsal-fin length [27–34 % (30 %) of SL], dorsal-fin base length [53–64 % (60 %) of SL], postorbital length [13–16 % (14 %) of SL], and upper caudal-fin length [18–31 % (24 %) of SL]. MNHN 1938-0002, 192 mm SL, is designated as a lectotype for P. belloci, and Bathythrissa dorsalis Gunther 1877 is shown to be a junior synonym of P. gissu.
TL;DR: The data suggest that dorsal and anal fin morphology may serve as a useful phenotype for defining metamorphic climax stages throughout post-embryonic development in C. variegatus.
Abstract: The sheepshead minnow Cyprinodon variegatus has become a favoured model for laboratory studies because of their small size, rapid development, and tolerance of laboratory conditions. Here, we analyse sheepshead minnow post-embryonic development with the goal of providing a generally useful method for staging fish after embryogenesis. Groups of three females and two males were placed in breeding chambers designed for this experiment. More than 100 eggs were collected and maintained in seawater. Embryos were selected under a dissection microscope and placed in incubation dishes (50 per dish) at 26 °C. On day six, embryos hatched and larvae were transferred to 1 L beakers. To define a simplified normalization table for sheepshead minnow development, we measured each fish for its standard length and examined the fish for four externally evident traits: pigmentation pattern, caudal fin morphology, anal fin morphology, and dorsal fin morphology. The four traits were chosen, because they are easily visualized with standard laboratory equipment such as the stereomicroscope and camera. We have provided criteria for staging sheepshead minnows in studies of post-embryonic development. Our data suggest that dorsal and anal fin morphology may serve as a useful phenotype for defining metamorphic climax stages throughout post-embryonic development in C. variegatus. The staging systems we propose should facilitate detailed anatomical and developmental analyses in relation to ecotoxicological studies on potential disruption of the thyroid axis by xenobiotics and endocrine-disrupting compounds.
TL;DR: The dispersal patterns of masu salmon Oncorhynchus masou masou were investigated at among-river and within-river levels in mid-western Hokkaido, Japan and found that there was no bias in dispersal at the among-River level, while anadromous males were more likely to disperse at the within- river level, suggesting that the dispersal pattern may be scale dependent.
Abstract: To evaluate the influences of spatial scale on dispersal, the dispersal patterns of masu salmon Oncorhynchus masou masou were investigated at among-river (ca. <43 km) and within-river levels in mid-western Hokkaido, Japan. A genetic differentiation (F
ST) and assignment test showed that among-river dispersal was much less common (2.9 % of 339 individuals) than within-river dispersal (7.4 % of 190 individuals). We also found that there was no bias in dispersal at the among-river level, while anadromous males were more likely to disperse at the within-river level, suggesting that the dispersal patterns may be scale dependent.
TL;DR: In this paper, a behavioural experiment on larval African catfish Clarias gariepinus in the laboratory was conducted to determine colour vision and colour discrimination in dim light.
Abstract: Many demersal fish species undergo vertical shifts in habitats during ontogeny especially after larval metamorphosis. The visual spectral sensitivity shifts with the habitat, indicating a change in colour vision. Colour vision depends on sufficient ambient light and becomes ineffective at a particular low light intensity. It is not known how fishes see colour in dim light. By means of a behavioural experiment on larval African catfish Clarias gariepinus in the laboratory, we determined colour vision and colour discrimination in dim light. Light-adapted larvae were subjected to classical conditioning to associate a reward feed with a green or a red stimulus placed among 7 shades of grey. The larvae learned this visual task after 70 and 90 trials. A different batch of larvae were trained to discriminate between green and red and then tested for the ability to discriminate between these colours, as the light intensity was reduced. The larvae learned this visual task after 110 trials in bright light and were able to discriminate colours, as light was dimmed until 0.01 lx, the minimal illuminance measurable in this study, and similar to starlight. The retinae of the larvae were found to be light adapted at 0.01 lx; thus indicating cone-based colour vision at this illuminance. For comparison, three human subjects were tested under similar conditions and showed a colour vision threshold at between 1.5 and 0.1 lx. For the larvae of C. gariepinus, the ability of colour discrimination in dim light is probably due to its retinal tapetum, which could increase the sensitivity of cones.
TL;DR: Spawning habitat and description of eggs of Gymnogobius cylindricus and G. macrognathos must be elucidated, because the knowledge of reproduction is especially important for conservation of fishes.
Abstract: Gymnogobius cylindricus and Gymnogobius macrognathos inhabit estuarine waters (Onikura et al. 2014; Ministry of the Environment 2015). Gymnogobius cylindricus is distributed from Aichi Prefecture to Kumamoto Prefecture in western Japan, and G. macrognathos is distributed from Miyagi Prefecture to Miyazaki Prefecture (Ministry of the Environment 2015). The genus Gymnogobius includes 13–16 species found in shallow marine, estuarine, and freshwaters throughout Japan, the Russian Far East, Kuril Islands, Korean Peninsula, and Yellow Sea (Stevenson 2002; Akihito et al. 2013). Therefore, clarification of habitat segregation among species of Gymnogobius is important for revealing the mechanisms of evolution and adaptive radiation in these fishes. In addition, G. cylindricus and G. macrognathos are listed in the Red Data Book edited by the Ministry of the Environment (2015) as ‘‘Endangered’’ and ‘‘Vulnerable’’, respectively. Therefore, the ecological information, such as life history, is necessary to effectively conserve these threatened gobies (Inui and Koyama 2014). In particular, spawning ecology of these species must be elucidated, because the knowledge of reproduction is especially important for conservation of fishes (e.g., Geist and Dauble 1998; Rowe and Hutchings 2003; Inui et al. 2010). Previous studies have reported that several species of Gymnogobius, including G. breunigii, G. scrobiculatus, and G. uchidai, spawned in the inner surface of burrows of upogebiid mud shrimps Upogebia major and callianassid ghost shrimp Nihonotrypaea japonica (Dôtu 1954; 1957; 1961; Inui et al. 2011). It is suggested that G. cylindricus may also spawn in the burrow of U. major similar to other species of Gymnogobius (Onikura et al. 2014), but the spawning nest of this goby has not been found. According to Onikura et al. (2014) and the Ministry of the Environment (2015), G. macrognathos mainly spawns in the burrow of N. japonica, but there are no details, for example, the physical environment of the spawning site and the conditions for the egg clutch of this goby. We found the egg clutch of G. cylindricus and G. macrognathos, and collected samples of these eggs at the mouth of the Kuma River (32 280N, 130 330E) in Kumamoto Prefecture. Spawning habitat and description of eggs of Gymnogobius cylindricus. The egg clutch of G. cylindricus was found on March 8, 2016, by shoveling bottom sediment burrowed by several invertebrates (Fig. 1a, b). This egg clutch was attached to an inner surface of a burrow, and half of the wall was covered with its eggs (Fig. 1b). The eggs were laid in a single layer in the burrow, which was in accord with other species of Gymnogobius (Dôtu 1954; 1957; 1961). Although the male G. cylindricus guarding the egg clutch could not be visually observed, a male [52.84 mm in standard length (SL)], which might have been the parent was collected from under the egg clutch (Fig. 1a). In addition, Upogebia major, Upogebia yokoyai, and Nihonotrypaea japonica were found around the spawning site and are the candidates for the host. The host shrimps could be easily distinguished between upogebiid mud shrimps and callianassid ghost shrimps by the burrow structure and the inner mud lining A. Koyama and R. Inui contributed equally to this work.
TL;DR: A small tributary of the Otofuke River of central Hokkaido, northern Japan dewatered in the summer of 2013, which allowed us to evaluate immigration after the summer draught and suggested that even remnant tributaries may be critical wintering habitats for some juvenile fishes.
Abstract: The winter ecology of stream fishes is still poorly understood, especially in non-salmonid species. A small tributary (<4 m in width, <1 km in length) of the Otofuke River (central Hokkaido, northern Japan) dewatered in the summer of 2013, which allowed us to evaluate immigration after the summer draught. More than 10000 juveniles of Siberian stone loach Barbatula toni, Japanese dace Tribolodon spp., and non-native rainbow trout Oncorhynchus mykiss immigrated to the tributary in the four months following the summer dewatering. This suggests that even remnant tributaries may be critical wintering habitats for some juvenile fishes.
TL;DR: It is suggested that the maintenance of the captive population under the current conditions could lead to extinction of the Itasenpara bitterling in 50 years, and simultaneously increasing the carrying capacity and individual exchange among populations appears to enhance the effective management of captive Itaseni bitterling populations.
Abstract: To conserve endangered species, the maintenance of ex situ captive populations with sustainable genetic diversity is often required, in combination with population viability analysis (PVA). Since 2010, the threatened Itasenpara bitterling Acheilognathus longipinnis lineages in the Kiso region, Japan, have been maintained in ex situ rearing facilities to allow for conservation efforts. In this study, we obtained microsatellite data from DNA extracted from these captive populations to elucidate their genetic diversity and effective population size. The populations of several initial generations indicated a deviation from Hardy–Weinberg equilibrium, probably due to the limited number of extracted founder individuals analyzed. The effective population size of the captive population tended to increase over the course of generations, although the degree of genetic diversity tended to decrease highlighting the concern for the progression of inbreeding. Our prediction based on the PVA suggests that the maintenance of the captive population under the current conditions could lead to extinction of the Itasenpara bitterling in 50 years. In contrast, simultaneously increasing the carrying capacity and individual exchange among populations appears to enhance the effective management of captive Itasenpara bitterling populations.
TL;DR: Genetic characterization was performed in five individuals of wild Amur sturgeon Acipenser schrenckii, and/or its presumed hybrid caught around Hokkaido, using a mitochondrial DNA (mtDNA) marker and two markers of nuclear DNA (nDNA).
Abstract: Genetic characterization was performed in five individuals of wild Amur sturgeon Acipenser schrenckii, and/or its presumed hybrid caught around Hokkaido, using a mitochondrial DNA (mtDNA) marker and two markers of nuclear DNA (nDNA). Genetic analyses indicated that two of the five fish had the mtDNA haplotype of Kaluga, Huso dauricus, whereas the nDNA markers indicated signs for both A. schrenckii and H. dauricus genotypes, referring to a hybrid origin. The other three fish were plausibly pure A. schrenckii. The results indicated the importance of combined usage of mtDNA and nDNA markers for correct species identification in sturgeon.
TL;DR: A new species of grenadier, Coryphaenoides soyoae, is described from two specimens collected from the Shichito-Iojima Ridge and off Fukushima, Honshu, Japan, at depths of 2740–2991 m.
Abstract: A new species of grenadier, Coryphaenoides soyoae, is described from two specimens collected from the Shichito-Iojima Ridge (type locality) and off Fukushima, Honshu, Japan, at depths of 2740–2991 m. The new species belongs to the subgenus Coryphaenoides and is most similar to Coryphaenoides castaneus Shcherbachev and Iwamoto 1995 and Coryphaenoides longicirrhus (Gilbert 1905). It differs from all other congeners in having the following combination of features: pelvic-fin rays 11; snout short, scarcely protruding beyond upper jaw; terminal snout scute absent; scales on lateral angles of snout and head ridges only slightly enlarged and thickened; dorsal contour of head prominently humped over nape; posterior end of upper jaw extending to below hind 1/3 of orbit or beyond; posterior end of rictus not restricted by lip folds; outer gill slit greatly restricted, length 7–8 % of head length (HL); barbel length 11–15 % HL; head bones and body flesh firm; teeth in posteriorly tapering bands on both jaws, with outer premaxillary series enlarged; body scales not deciduous, covered with narrowly divergent rows of needle-like spinules, and the last spinule in each row greatly overlapping posterior scale margin; snout fully scaled dorsally, broadly naked ventrally; interdorsal space slightly less than first dorsal-fin base length; origins of second dorsal and anal fins on about same vertical; height of first dorsal fin 87 % HL; second spinous ray of first dorsal fin serrated along its leading edge; outer pelvic-fin ray greatly prolonged, its tip extending well beyond anal-fin origin; head and body uniformly blackish. In addition, Coryphaenoides rudis Gunther 1878 is recorded for the first time from Japan, based on six specimens collected from Hyuga-nada, Suruga Bay, and the west of Minami-torishima Island (=Marcus Island), at depths of 1100–1481 m. A previous record of this species from Japanese waters was based on a misidentified specimen of a different genus.