Pointhead Flounder Research Articles

Effects of Temperature on the Gastric Evacuation Rate and Maintenance Ration of Adult Pointhead Flounder Cleisthenes pinetorum

We investigated the gastric evacuation rate (GER) and maintenance ration (MR) for the adult pointhead flounder Cleisthenes pinetorum (77–421 g) at 4°C, 9°C, and 14°C which reflect the bottom, middle, and surface temperatures of their habitat in early summer. GERs were obtained from gravimetric experiments with 34 flounders fed juvenile walleye pollock Gadus chalcogrammus as prey. A 169‐day feeding experiment for 67 pointhead flounders fed krill Thysanoessa inermis was undertaken to measure MR. The effects of a 10°C temperature increase (Q10) on the GER and the MR were 6.55 and 2.04, respectively, indicating that the effect of temperature was greater on GER than on MR. As a result, the differences between the GER and MR, indicating the maximum amount of food ingestible for growth, were 2.8 and 30.7 cal·g−1 day−1 at 4 and 14°C, respectively. The water temperature on the sea floor generally remained at <4°C from winter through summer, but exceeded 10°C in the surface layer of Funka Bay, where pointhead flounders were sampled. Therefore, their growth rate should be considerably limited if they remain in the bottom layer. The unique ecology of this species among the flatfishes of floating from sea floor and feeding at pelagic zones may represent a strategy to compensate for the physiological limitation of growth at low temperatures.

Broadband target strength of arabesque greenling, Pacific sand lance, and pointhead flounder

Abstract Measurement of target strength (TS) is important for estimating the abundance of species using fisheries acoustics. However, most researchers have only used a limited number of representative frequencies for acoustic measurements of fish without a swim bladder (bladderless fish). Here, we measured the broadband TS of three bladderless fish species, arabesque greenling (Pleurogrammus azonus), Pacific sand lance (Ammodytes personatus), and pointhead flounder (Cleisthenes pinetorum), using two broadband echosounders. TS measurements were conducted in a seawater tank over frequency ranges of 45–90 and 80–120 kHz using a tether method. Higher TS and directivity were observed at higher frequencies than at lower frequencies for pointhead flounder and arabesque greenling. However, the TS for Pacific sand lance was relatively flat over the measured frequency spectra. Additionally, the TS of pointhead flounder and Pacific sand lance could be expressed as a function of body length and the TS of arabesque greenling could be expressed as a function of body length and frequency, which could be used in fish species discriminations and size estimations.

On validity of species of the genus Cleisthenes (Pleuronectiformes: Pleuronectidae)

Taxonomy status of genus Cleisthenes was revised several times from the time of its description (Jordan and Starks, 1904) to nowadays. Some species of this genus were even assigned to genus Hippoglossoides. At present, the stumbling block in taxonomy of the genus is: whether the genus is represented by two species (pointhead flounder Cleisthenes herzensteini and pinewood flounder C. pinetorum ) or only one. The problem cannot be easy solved because of many contradictions in previous studies. On the base of retrospective information on taxonomy of these/this species, statistical significance for divergence of some morphological indices is identified by the Kolmogorov-Smirnov criterion of homogeneity, that prevents reduction of diversity for the forms pinetorum and herzensteini to one species. The flounders of genus Cleisthenes dwelling the waters of the Sendai Bay (Miyagi and Fukushima prefectures of Japan) are obviously C. pinetorum , whereas the rest of this genus range is inhabited by C. herzensteini .

In situ broadband acoustic measurements of age-0 walleye pollock and pointhead flounder in Funka Bay, Hokkaido, Japan

Measurements of the broadband acoustic backscattering from fish should improve acoustic discrimination between species. The pulse compression processing of broadband systems can be used to measure acoustic backscattering with high range resolution and improve signal-to-noise ratio. This may increase opportunities for in situ target strength (TS) measurements, the preferred method of collecting TS data. To evaluate the availability of TS spectra for acoustic discrimination, three Simrad EK80 wideband transceivers and split-beam transducers of 70, 120, and 200 kHz were used to collect in situ frequency responses of TS from age-0 juvenile walleye pollock and pointhead flounder, a swimbladderless flat-fish, distributed in and around Funka Bay, Hokkaido, Japan. The single echoes were extracted from backscattering data, and the TS spectra of the two species were obtained. However, processing of the broadband acoustic data is under discussion. To ensure the reliability of our data, the TS spectra of standard targets were also calculated. The measured TS spectra of the standard targets were close to the theoretical TS spectra. The individual TS spectra of two species included complex frequency response; however, the mean TS spectrum was relatively stable. The different characteristics of the frequency responses observed for the two species were in good agreement with reported observations. The results available for the acoustic discrimination were similar to the multi-frequency method, which uses two or more single frequencies. The raw TS spectra should aid in not only discriminating between species but also Q3 estimating the size of the fish.

Acoustic discrimination between juvenile walleye pollock and pointhead flounder

When using acoustic methods to investigate fish biomass, it is important to distinguish the target species from other organisms. Previous limitations to acoustic information in surveys meant it was not possible to discriminate juvenile walleye pollock from their predator, pointhead flounder, in Funka Bay, Japan, possibly leading to overestimates in population size. Thus, here, an acoustic method was developed to distinguish the two species based on relative frequency response. This method was used to survey juvenile walleye pollock to evaluate capture potential around Funka Bay, Japan, where pointhead flounder is reportedly its most abundant predator. Volume backscattering strength of pointhead flounder was highest at 200 kHz, while that of juvenile walleye pollock was highest at 38 kHz. Therefore, the relative frequency response at 38 kHz and 200 kHz was successfully used to distinguish between the two species. This method could be more extensively applied to other species in other aquatic environments globally.

Acoustic characteristics of three bladderless fishes

The acoustic characteristics of bladderless fishes were examined by measuring the target strength (TS) of three species, pointhead flounder (flat-shaped), Arabesque greenling (spindle-shaped) and sandeel (cylinder-shaped). TS measurements were collected in a seawater tank (10 × 6 × 5 m) using the EK80 echo sounder (Simrad, Norway) and ES70-7C transducer (Simrad) over a frequency range of 45–90 kHz with a tether method. After TS measurement of the whole fish, we separated the flesh from the body (for pointhead flounder and arabesque greenling) and measured the TS of the head and bones. Pitch angle characteristics were measured from a head-down orientation (−30 deg) to a head-up orientation (30 deg), and TS was processed using Echoview 9 software (Echoview, Australia). TS patterns were examined with respect to orientation using the distorted-wave Born approximation model. The standard length, width, and height of fish were inputted into the model. The three bladderless fishes tested have different body shapes, meaning different areas are exposed to sound waves at the same body length. Therefore, the relationship between TS and the cross-section of the dorsal aspect of bladderless fish is discussed. [Work supported by the Sasakawa Scientific Research Grant from The Japan Science Society.]

Study on acoustic characteristics of pointhead flounder Cleisthenes pinetorum and juvenile walleye pollock Gadus chalcogrammus

In this study, the acoustic differences between the pointhead flounder and the juvenile walleye pollock were examined using a quantitative echo-sounder around the Funka Bay, Japan and the acoustic characteristics of the pointhead flounder have been surveyed. Acoustics data of the fish were monitored using a Simrad EK60 (38, 120, 200 kHz) split-beam echo sounder in the field. The target strength (TS) and swimming angle of free swimming pointhead flounders were measured in a seawater tank (length: 10 m, width: 5 m, and height: 6 m). As the result, pointhead flounder schools presented a patch shaped echo on the echograms, whereas the distribution patterns of the juvenile walleye pollock schools were layered. The volume backscattering strength (SV) of the target schools extracted from the echograms showed that the pointhead flounder presented a higher SV at high frequency. In contrast, the juvenile walleye pollock showed higher SV at a low frequency. For pointhead flounder, the distribution of pitch angle was measured both by camera and echo-sounder at the experiments in the tank and shown the same distribution pattern. The TS of pointhead flounder is large bigger than other bladderless fish.

Target strength measurements of pointhead flounder, Cleisthenes pinetorum, a flatfish without a bladder

There are only a few acoustic surveys of the bladderless fish. As is known by all, Atlantic mackerel was surveyed these years by echo-sounder and showed the high target strength at high frequency. In northern Japan, an interesting fish attracted the attention these years which called pointhead flounder, Cleisthenes pinetorum, without a bladder. It is a flatfish but captures prey in the middle water column. And the body shape is not the normal spindle-shaped, but a flat shape, which may cause different acoustic characteristics with Atlantic mackerel. We did the surveys in Funka Bay, northern Japan and keep the samples to the tank to measure the acoustic characteristics of live flounder. The acoustic characteristics of pointhead flounder measured both using the tether method (38, 120 kHz) and free swimming method (120 kHz). During the measurements of free swimming method, we also observed the swimming actions of pointhead flounder and calculated the swimming angle at the same time. We also discussed the characteristics of TS of the swimming angle.There are only a few acoustic surveys of the bladderless fish. As is known by all, Atlantic mackerel was surveyed these years by echo-sounder and showed the high target strength at high frequency. In northern Japan, an interesting fish attracted the attention these years which called pointhead flounder, Cleisthenes pinetorum, without a bladder. It is a flatfish but captures prey in the middle water column. And the body shape is not the normal spindle-shaped, but a flat shape, which may cause different acoustic characteristics with Atlantic mackerel. We did the surveys in Funka Bay, northern Japan and keep the samples to the tank to measure the acoustic characteristics of live flounder. The acoustic characteristics of pointhead flounder measured both using the tether method (38, 120 kHz) and free swimming method (120 kHz). During the measurements of free swimming method, we also observed the swimming actions of pointhead flounder and calculated the swimming angle at the same time. We also discussed the cha...

Reconfirmation of age and growth of the pointhead flounder, Hippoglossoides pinetorum in the coastal waters of the East Sea off Gyeongbuk

Reconfirmation of age and growth of the pointhead flounder, Hippoglossoides pinetorum in the coastal waters of the East Sea off Gyeongbuk

Individual variations in fatty acid composition and concentration as indicators of the nutritional condition of wild pointhead flounder larvae

We investigated the fatty acid compositions and concentrations of wild marine fish larvae with a highly accurate method because our knowledge of them has been seriously limited compared with cultured larvae. This study presents estimates of the fatty-acid-based nutritional condition of individual larvae in the field. Because the pointhead flounder Cleisthenes pinetorum displays relatively high stock size fluctuations, we investigated the developmental change in the fatty acid compositions of the body trunk, head, and eye and the annual fluctuations in the fatty acid concentrations in the trunk. We show that the process of fatty acid accumulation is not uniform across body parts and that the trunk is a better indicator of larval nutritional status than other parts because there is less time lag. Starved larvae with simultaneously high docosahexaenomic acid ratios and low total fatty acid concentrations, as observed in laboratory experiments, are rare in the wild. Thus, starved larvae must be removed rapidly by predators before they can experience a relatively long period of starvation in the wild. Fatty acid accumulation was greater in the larvae of the 2005 year class than in those of the 2006 year class in their first feeding stage, according to the optimal model derived with generalized linear model. A previous study indicated that the 2005 year class showed stronger recruitment than the 2006 year class. We conclude that the fatty acid analysis of wild larvae is a useful index of their nutritional status and mortality, especially in the first feeding stage.

Comparison of catches and species composition for flounders caught using gillnets, gillnets with supporting lines, and trammel nets

To compare the catches made using gillnets, trammel nets, and gillnets with supporting lines, several experiments were conducted with commercial vessels near Uljin and Pohang in Eastern Korea between July 2010 and May 2011. Two sets of 13 different nets were used, including 5 panels of gillnets and trammel nets each with stretched mesh sizes of 7.6, 9.1, 10.6, 12.1, and 13.6 cm and 3 panels of gillnets with a mesh size of 9.1 cm with supporting lines with different line spacing. The outer (stretched) mesh size of the trammel nets measured 51.5 cm. The target fishes of the fishing nets were various types of flounders. The catch rate of flounders was 50.7% of the total catch in weight. The total catch for all nets was 443.8 kg. The predominant species was pointhead flounder (Cleisthenes pinetorum). The total catch by trammel nets was 1.4 times that of the comparable gillnets. But more pointhead flounder were caught by gillnets than by trammel nets, though there was no significant difference. Fishermen catching the pointhead flounder in Korea said that there was no need to use trammel net to catch it; this was an unexpected finding compared to the findings of other flounder fisheries. The amounts of roughscale sole, brown sole, and blackfin flounder caught by trammel nets were greater than those caught by gillnets. The mean lengths (standard deviation) of blackfin flounder, pointhead flounder, brown sole, and roughscale sole were 21.0 (4.57), 22.9 (3.40), 24.7 (4.90), and 28.3 (5.43) cm, respectively; there were significant differences in mean length (p < 0.00001). Therefore, in order to catch flounder efficiently, the fishing nets and mesh size should be chosen according to the target species. One advantage of using supporting lines is that it prevents breakage by strengthening the material especially when utilized on a rough bottom. Catch by using gillnet with supporting lines was not greater than that by using trammel net for the conservation of fisheries resources.

그물실의 물성에 따른 동해안 가자미 자망어업의 어획 특성

Physical characteristics of net filament were investigated to test the fishing capacity of gill nets due to the flexibility difference between nylon and biodegradable nets (PBS 95%+PBAT 5% and PBS 80%+PBAT 20%). In addition, a total of 16 fishing experiments were conducted in the coastal waters of Jeongja, Ulsan, from August 10 to October 20, 2011 and from September 11 to November 3, 2012. The test results showed that nylon net filament exhibited more flexibility than biodegradable net filament when they were wet. Accordingly, the longer submerged time, the more fishing capacity the nylon gill nets demonstrated in comparison with the biodegradable gill nets. A total of 16 species were caught in 2011 with the nylon gill nets (1,323 fishes, weighing 342,885g) and the biodegradable gill nets (958 fishes, weighing 236,857g). 15 species were caught in 2012 with the nylon gill nets (1,582 fishes, weighing 448,360g) and the biodegradable gill nets (1,431 fishes, weighing 406,590g). Thus catch weights and the number of fish caught produced by the nylon nets were 1.45 times and 1.38 times higher than those of the biodegradable nets produced in 2011, and 1.1 times and 1.11 times higher in 2012. A test on the target species, pointhead flounder (Cleisthenes pinetorum) has similar results. The flexibility of a net was proved to be related to the fishing capacity, and as a result, it is concluded that the higher flexibility, the higher fishing capacity.

Isolation and characterization of twenty novel microsatellite markers of Pointhead flounder (Cleisthenes herzensteini)

The Pointhead flounder (Cleisthenes herzensteini), a severely overexploited and endangered flatfish in the Japanese Archipelago, Bohai Sea, Yellow Sea and East China Sea, is in urgent need of conservation and management measures. In this study, a total of 20 polymorphic microsatellite markers were derived from C. herzensteini. The genotyping of 30 wild-caught individuals showed observed and expected heterozygosities ranging from 0.1724 to 1.0000 and 0.5850 to 0.9226, respectively. The average allele number was 9.5 per locus (range 5–14). These polymorphic microsatellite loci would be useful for investigating genetic diversity of C. herzensteini.

Population genetic structure of the point-head flounder, Cleisthenes herzensteini, in the Northwestern Pacific

Intraspecific phylogenies can provide useful insights into how populations have been shaped by historical and contemporary processes. To determine the population genetic structure and the demographic and colonization history of Cleisthenes herzensteini in the Northwestern Pacific, one hundred and twenty-one individuals were sampled from six localities along the coastal regions of Japan and the Yellow Sea of China. Mitochondrial DNA variation was analyzed using DNA sequence data from the 5' end of control region. High levels of haplotype diversity (>0.96) were found for all populations, indicating a high level of genetic diversity. No pattern of isolation by distance was detected among the population differentiation throughout the examined range. Analyses of molecular variance (AMOVA) and the conventional population statistic Fst revealed no significant population genetic structure among populations. According to the exact test of differentiation among populations, the null hypothesis that C. herzensteini within the examined range constituted a non-differential mtDNA gene pool was accepted. The demographic history of C. herzensteini was examined using neutrality test and mismatch distribution analyses and results indicated Pleistocene population expansion (about 94-376kya) in the species, which was consistent with the inference result of nested clade phylogeographical analysis (NCPA) showing contiguous range expansion for C. herzensteini. The lack of phylogeographical structure for the species may reflect a recent range expansion after the glacial maximum and insufficient time to attain migration-drift equilibrium.

Comparison of the color vision and spectral sensitivity of three flatfish species of different ecotypes, and application to selective fishing methods

In this study, we determined the color vision and spectral sensitivity of pointhead flounder, slime flounder, and red halibut by recording electrophysiological S-potentials from isolated retinas; this basic data was collected to aid the selection of appropriate colors and effective wavelengths for selective fishing gear for sustainable fisheries. Four kinds of L-response and one C-response were recorded in the pointhead flounder and red halibut. Two kinds of L-response were recorded in the slime flounder. The occurrence of a C-response indicates the possession of color vision. The C-responses show that the pointhead flounder has superior distinction from blue to yellow, and red halibut has superior distinction from blue and green to red. The most frequently recorded L-responses indicate high spectral sensitivity at 544 nm in pointhead flounder and 518 nm in slime flounder and red halibut. All recorded L- and C-responses indicate sensitivity to ultraviolet wavelengths.

Comparison of visual acuity and visual axis of three flatfish species with different ecotypes

The visual acuity, visual axis and visual accommodation of pointhead flounder, slime flounder, and red halibut were determined to obtain basic knowledge for developing appropriate fishing gear and fishing methods for sustainable fisheries. Each of these species has a different ecotype in terms of habitat, depth and prey species. Thus, it was hypothesized that they may differ in terms of visual acuity, visual axis and visual accommodation. Few studies have compared these characters in flatfishes from different ecotypes. We used histological methods to determine visual acuity (i.e. cone cell density) and visual axis (i.e. cone cell distribution) in each of these species. The maximum visual acuity was 0.127 in pointhead flounder (total length, TL 344 mm), 0.092 in slime flounder (TL 372 mm) and 0.109 in red halibut (TL 336 mm). Based on the cone cell distribution in the retina, the visual axis was upward and forward in pointhead flounder, forward and downward in slime flounder, and downward in red halibut. Finally, the mean angle of lens movement was −2° in pointhead flounder, −13° in slime flounder and −32° in red halibut. This measurement of lens movement indicated that the average near-point distance was 0.87× TL in pointhead flounder, 0.65 × TL in slime flounder and 1.02 × TL in red halibut. At similar TL (336–355 mm), the visual acuity of these species differs depending on the direction in which they are looking.

The late 1980s regime shift in the ecosystem of Tsushima warm current in the Japan/East Sea: Evidence from historical data and possible mechanisms

A climatic regime shift, an abrupt change from cooling to warming in the Japan/East Sea (JES), particularly in the Tsushima warm current (TWC) region, occurred in the late 1980s. The ecosystem of the JES responded strongly to the changing thermal regime. Many, but not all biological components of the ecosystem, spanning from plankton to predatory fishes, and including both warm-water pelagic and cold-water demersal species responded to this late 1980s climatic regime shift in the JES. Diatom abundance (cell number) in spring from a monitoring line located in the central part of JES showed decadal variations with a step change from positive to negative anomalies in 1991. Zooplankton biomass in spring and autumn was high in the 1970s, declined during the 1980s, and returned to higher, but quite variable levels during the 1990s. Japanese sardine catch increased after 1974 to its peak level in 1989 and then declined dramatically to 1974 levels by 1997 with step changes in 1979 and 1994. Conversely, catches of other small pelagic species such as Japanese anchovy and common squid, and several higher-trophic fishes, such as yellowtail and tunas increased markedly in the 1990s compared to the early-mid 1980s. Step changes were detected in these pelagic species during 1989–1992. Catch of demersal species (crab, pink shrimp, Pacific cod and walleye pollock) were high during most of the 1970–1980s, but declined at various times in the late 1980s to generally low catches in the 1990s. Detailed analysis of the demersal fish assemblage composition, abundance and distribution indicated a shift in the late 1980s with several years lag in the time of change. Cold-water species (e.g., walleye pollock, Pacific cod) decreased in abundance and the regions in which their abundances remained high became greatly reduced in extent. Conversely, warm-water species (e.g., pointhead flounder, shotted halibut) increased in abundance and/or extended their spatial range (as indicated by trawl catch) during the warm 1990s. A principal component analysis for pelagic and demersal fish assemblages, suggested decadal variation patterns with a step change during 1986–1988. Abundance changes were identified not only in the plankton, but also in small pelagic fishes, and in predatory fishes. These changes were reflected in fish community indicators, and suggest an ecosystem regime shift occurred in the TWC region as a result of the late 1980s climatic regime shift. A hypothesis on the ecological response process to the late 1980s climatic regime shift was proposed.

Postspawning Destruction of Male Gametes in Polycyclic and Monocyclic Bony Fishes: Pointhead Flounder, Cleisthenes herzensteini Schmidt (Pleuronectidae) and Chum Salmon, Oncorhynchus keta Walbaum (Salmonidae)

The process of the destruction of nonreleased spermatozoa was studied using TEM in the postspawning gonads of the chum salmon Oncorhynchus keta and the pointhead flounder Cleisthenes herzensteini, as representatives of monocyclic and polycyclic fishes respectively. It was shown that in both species residual sperm cells are destroyed through fragmentation of chromatin and the entire cell. It is supposed that the process of destruction in this case is connected with autolytic disintegration known in some multicellular animals, but never described for Teleostei.

Distribution and movement of larvae, juvenile and young of the pointhead flounder Hippoglossoides pinetorum in Ishikari Bay and vicinity, Hokkaido

SUMMARY: To determine the nursery grounds and process of recruitment to adult stock, pelagic larvae, post-settlement juveniles and young fish of the pointhead flounder Hippoglossoides pinetorum, samples were collected in Ishikari Bay and the Rumoi coast, Hokkaido from 1991 to 1994. Spawning may continue from late May to mid September with the peak between July and August. However, since pelagic larvae were caught only from late July to early September in the present study, it was assumed that the restricted cohort recruited to post-settlement juvenile stage. Newly settled juveniles occurred in Ishikari Bay in September and in the Rumoi coast in late August and were mainly distributed at depths of 30–69 m. The habitat of 1-year-old and older flounder was deeper than that of 0-year-old flounder in autumn. Post-settlement juveniles gradually migrate to shallow areas during winter and their main habitats were at a depth range of 20–30 m in May. Although 1- and 2-year-old flounder were caught in the area of 20–40 m depths in June, few 3-year-old or older flounder were sampled by beam trawl. The same phenomena were recognized from the re-analyzed data of the otter trawl surveys in 1988. The pointhead flounder mainly occurred in the shallow water of the continental shelf until 2 years old and shifted their habitat to deeper areas (the upper area of the continental shelf) by 3 years old in Ishikari Bay and the surrounding area.

Studies of cysteine protease active in an acidic pH range of fish. I. Existence of cysteine proteinase active in an acidic pH range in fish.

The autolytic activity of various fish(16 species) muscle homogenate in an acidic pH range was measured in the presence of leupeptin and/or pepstatin A. The activity between pH 3 and 5 was inhibited by leupeptin as well as by pepstatin A in all fish examined. Especially, the activities of pointhead flounder Cleisthenes herzensteini, frog flounder Pleuronichthys cornutus, horse mackerel Trachurus japonicus and reticulated emperor Lethrinus semicinctus were inhibited chiefly by leupeptin The hemoglobin hydrolyzing activities of the crude extract from many fish muscles and livers in the presence of pepstatin A show the maximum activity at pH 4.0, and the activities of fish (53 species) muscles and livers in the presense of pepstatin A and/or leupeptin were measured at pH 4.0. The activities which was not inhibited by pepstatin A but inhibited by leupeptin were detected in almost all fish muscle and liver, and the activities of Pleuronectiformes (flathead flounder Hip-poglossoides dubius, frog flounder, pointhead flounder and bastard halibut Paralichthys olivaceus) were high. It was considered that the activity was due to the cysteine proteinase differing from cathepsin B or L.