Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

The red swamp crayfish Procambarus clarkii (Girard, 1852) is an alien invasive species as well as a commercially exploited animal. The sterile-male-release technique (SMRT) using infertile but sexually active males has been an effective candidate measure to control this invasive crayfish. Additionally, the limited supply of juveniles due to females’ spawning seasonality hinders the further development of the P. clarkii aquaculture industry. Information on its reproductive biology, such mating strategies and factors affecting offspring production, is crucial for developing an effective SMRT and aquaculture systems for P. clarkii. We review the reproductive biology of this species in terms of 1) sexual dimorphism and reproductive status, 2) sex recognition, mating, and mate preferences, and 3) egg production, embryonic development, and hatching. Intra- and intersexual dimorphisms of chelae are evident in P. clarkii, and a reproductive morphotype (form I) with larger chelae and a non-reproductive morphotype (form II) with smaller chelae are detected in both females and males, allowing us to easily determine the reproductive status of both sexes. The crayfish exhibits mutual mate choice (i.e., preference for larger mates), and small-sized males reproductive potential is low. Female fitness (i.e., number of offspring) generally depends on their body size. Female brood care appears to promote early embryo development before the egg-nauplius stage. Further study is required to identify the maternal factors affecting early embryonic development, which may improve measures for controlling invasive populations and enhancing aquaculture productivity.

DOI： 10.1093/jcbiol/ruad063

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DOI： 10.3825/ece.21-00032

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DOI： 10.1007/s11355-022-00531-9

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 農業農村工学会  

<p>We conducted field surveys to clarify distribution of the wintering Nagoya Daruma Pond Frog (<i>Pelophylax porosus brevipodus</i>) and the environmental factors affecting wintering site of this species in a rice paddy field and an adjacent fallow paddy field in Kurashiki, Okayama Prefecture, western Japan, where the species inhabits at a high density. The majority of the wintering individuals (34 out of 35) were found in the fallow paddy field. A GLM was fitted using presence and absence of this species as the objective variable, whereas cover rate, plant height, soil pH, volumetric water content, gravimetric water content, degree of saturation, porosity, and topsoil hardness as the explanatory variables. The best model selected based on AIC consisted of soil hardness, cover rate, and the quadratic term of plant height, in which the negative effect of soil hardness was significant. The results insist on the importance of soil hardness and the presence of plants on the topsoil when creating wintering habitat for this frog species in rice paddy fields.</p>

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J-GLOBAL

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Authorship：Lead author,　Corresponding author   Language：Japanese  

DOI： 10.5179/benthos.71.90

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：Ecology and Civil Engineering Society  

Rhodeus atremius suigensis is an endangered bitterling species designated as a Nationally Endangered Species of Wild Fauna and Flora by the Ministry of Environment of Japan. In order to create preferable microhabitats for the threatened bitterling in agricultural channels, environmental factors affecting its occurrence need to be identified. The present study investigated environmental preference of the fish inhabiting an agricultural channel in southern Okayama Prefecture, western Japan, through monthly surveys of fishes and physical environments between June 2014 and May 2015. The effects of physical environmental factors on the occurrence of the bitterling were analyzed using generalized linear models （GLM） with binomial probability distribution or generalized estimating equations （GEE）, seasons separately. The best models yielded by model selection based on AIC or QICu revealed seasonal changes in the key environmental factors for the occurrence of the bitterling. The variables with positive effects on the bitterling occurrence included submerged macrophyte coverage during the spring and the summer to autumn period and presence of submerged structures and above-water cover during the winter. Water velocity had a negative effect on the occurrence during the spring and the summer to autumn periods. At the same time, mean hydraulic environment at the locations with the bitterling occurrence was consistent throughout the study period, with water velocity less than 11.5 cm/s （3.4 cm/s on average） and water depth ranging 20-50 cm （37.7 cm on average）. The findings insist on the importance of the above mentioned lentic environment, in addition to covering materials represented by submerged structures and above-water cover, when creating preferable microhabitats for the bitterling in agricultural channels.

DOI： 10.3825/ece.19.117

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Ecology and Civil Engineering Society  

We focused on artificial spawning beds for a conservation method of endangered bitterling fish inhabiting agricultural channels. To clarify any preference for host mussel species by bitterling fish, we conducted a field experiment to set artificial spawning beds in an agricultural channel in southern Okayama, western Japan, between March and August 2014. We set nine artificial spawning beds (50 cm×36 cm×8 cm) each with a single species of three mussel species (Unio douglasiae nipponensis, Pronodularia japanensis and Lanceolaria grayana cuspidata) made of rectangular plastic trays at the experimental site. After three weeks, we retrieved the mussels from the spawning beds and then individually reared them in aquaria in the laboratory to observe the number and the species of bitterling juveniles that emerged from each host mussel. The total number of juveniles that emerged from the host mussels was 679( 420 from U. douglasiae nipponensis and 259 from P. japanensis
no individuals from L. grayana cuspidata). We identified four bitterling species including three endangered native Tanakia limbata, Tanakia lanceolata and Acheilognathus rhombeus, as well as the invasive Rhodeus ocellatus ocellatus, but the number of A. rhombeus was only 9 because this fish is an autumn-spawning species and thus spawned before the experiment (i.e., in 2013). Rhodeus ocellatus ocellatus spawned U. douglasiae nipponensis and P. japanensis, but T. limbata and T. lanceolata utilized only P. japanensis as host mussels, indicating that host mussel preference differed among the three bitterling species. In this study, an endangered species Rhodeus atremius suigensis, inhabiting the experimental channel, designated as a Nationally Endangered Species of Wild Fauna and Flora by the Ministry of Environment of Japan did not utilize the spawning beds. We need to clarify the preference for mussel species and appropriate artificial spawning beds for R. atremius suigensis.

DOI： 10.3825/ece.20.33

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Ecology and Civil Engineering Society  

To clarify movement patterns of freshwater fish inhabiting restoration areas in agricultural channels in relation to effectiveness for fish conservation, we conducted fish samplings at five study stations with different types of restoration method (wooden raft walkway, fish nursery blocks, and deep water) in an agricultural channel (areas that did not dry-up even in the non-irrigation period) southern Okayama, western Japan in July and October 2014 and January, July, October and December 2015. In the samplings, we carried out mark recapture investigations on six fish species (Carassius sp., Tanakia limbata, Acheilognathus rhombeus, Candidia sieboldii, Misgurnus anguillicaudatus and Odontobutis obscura) to evaluate the habitat utilization and seasonal movement within the restoration areas. In the restoration areas, we recaptured 133 marked fish individuals including all six species during the investigation period. Of the fish, 114 and 19 individuals were recaptured at the same and different study stations where the fish were released, respectively, indicating that many fish individuals continuously inhabit the same restoration area. These results indicate that the restoration areas can provide suitable habitats for fish in this study channel.

DOI： 10.3825/ece.20.213

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Authorship：Corresponding author   Language：Japanese   Publisher：The Japanese Society of Irrigation, Drainage and Rural Engineering  

Freshwater fishes inhabiting agricultural channels change their distribution area according to the life history stages, and the fish habitat can change among seasons (i.e., reproductive season, growing season and wintering season, etc.). Thus, to evaluate the effectivity of the restoration methods for fish, we have to understand the seasonal difference of habitat preference by fish and then reflect the knowledge to restoration methods in agricultural channel improvements. In this study, we conducted fish samplings in restoration areas, as well as non-restoration areas, of an agricultural channel, to clarify the difference of habitat preference by fish between the active and wintering seasons. The results of multiple regression analysis indicate that important environmental factors for fish habitats are different between the active and wintering seasons and that the factors are the water depth diversity, average water velocity and minimum water velocity in the active season and are the maximum water depth, average water velocity and rate of vegetation in the wintering season. These results indicate that fish inhabitation areas in the agricultural channel are different between the active and wintering seasons. To create restoration areas for fish habitats in agricultural channel improvements, we need to consider the difference of the habitat preference by fish between the active and wintering seasons.

DOI： 10.11408/jsidre.85.II_61

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society for Aquaculture Research, Nishimura Toushadou Ltd.  

The aquarium fish Youkihi-medaka is a mutant of Minami-medaka (Oryzias latipes) characterized by its scarlet body color. Comparative analysis between Youkihi-medaka and Hi-medaka was performed on the following: scale chromatophores, quantifying carotenoids within the body, and changes to the body color due to feed containing carotenoids. Chromatophores in the scales of both Youkihi-medaka and Hi-medaka were primarily yellow, and none was black. However, pigment granules within the yellow chromatophores of Youkihi-medaka appear reddish orange in contrast to the pale yellow of Hi-medaka. Analysis by HPLC revealed that the quantities of the carotenoids, astaxanthin, zeaxanthin, and lutein were found to be higher in Youkihi-medaka than in Hi-medaka. Astaxanthin, in particular, exhibited a concentration 10 times greater in Youkihi-medaka than in Hi-medaka. When astaxanthin was added to the feed, the hue value of the dorsum of the head in both Youkihi-medaka and Hi-medaka decreased significantly. These results show that the scarlet body color of Youkihi-medaka is related to abundant carotenoids and that the redness is further intensified by the intake of carotenoids.

DOI： 10.11233/aquaculturesci.65.203

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC FISHERIES SCIENCE  

DOI： 10.2331/suisan.16-00018

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Ecology and Civil Engineering Society  

The Japanese mitten crab Eriocheir japonica is an edible species commonly inhabiting rivers throughout the Japanese Archipelago. The present study investigated daytime shelter preference of the crab by a field experiment. The riverine experiment was done in an enclosure that was screened with an agricultural plastic netting. The enclosure was composed of sixteen 1-m2 sections, each section with one of the eight different riverbed substrate types( loose boulders with interstices, embedded boulders, loose cobbles with interstices, embedded cobbles, pebbles, sand, leaf litter, or woody debris
each with two replicates). Sixty-nine adult crabs were released into the enclosure and their hiding substrate types during the daytime were observed on a daily basis starting on the following day for 12 consecutive days. Of the total of 334 observations, 61.0% of the crabs were found in loose boulders with interstices, followed by woody debris (21.2%) and loose cobbles with interstices (12.8%). Significant positive rank correlations were observed between the carapace width of the crabs and the dimensions of the interstices used by these individuals (width: τ = 0.232, height: τ = 0.155, depth: τ = 0.091), indicating that the preferred shelter size by E. japonica changes according to the body size.

DOI： 10.3825/ece.19.1

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Ecology and Civil Engineering Society  

To examine the effectiveness of artificial burrows for eradicating the North American invasive crayfish Procambarus clarkii, we conducted a field experiment of capturing the invasive crayfish in two ponds in the Handayama Botanical Garden, Okayama, Japan, by using artificial burrows of preferred sizes during September to November 2014. We set the artificial burrows, which were made from straight polyvinyl chloride pipes of different sizes, at 15 study stations in the ponds in the late afternoon and then collected them early the following morning. In both ponds, P. clarkii were continuously captured using the artificial burrows during the experimental period and the total number of crayfish captured was 51. Furthermore, two females with 104 and 258 hatchlings, respectively, were captured using the artificial burrows. The body sizes of crayfish captured ranged 8.135.7 mm and 22.7-83. 4 mm in carapace length and total length, respectively, indicating that the artificial burrows of preferred sizes can collect P. clarkii of various sizes. We conclude that the artificial burrows of preferred sizes are effective for capture and subsequent eradication of P. clarkii, including females with hatchlings.

DOI： 10.3825/ece.18.139

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Authorship：Corresponding author   Language：Japanese   Publisher：Ecology and Civil Engineering Society  

We conducted aquarium experiments of artificial burrow preference by the North American invasive crayfish Procambarus clarkii to clarify the artificial burrow sizes for capturing P. clarkii in invaded freshwater areas （e.g., paddy fields, agricultural channels, rivers, lakes, ponds, etc.）. In the aquarium experiments, we observed the preference for internal diameters and lengths of artificial burrows by P. clarkii, which were made from straight polyvinyl chloride pipes. The relationship between the total length （TL）（X, mm） of P. clarkii and the preferred internal diameter （Y, mm） of artificial burrows was described by the significant linear regression: Y＝0.58X＋4.26（ n＝49, P＜0.001）. Among the artificial burrows of different lengths, TL×4 burrows were mainly preferred by P. clarkii. Based on these results, we propose artificial burrow sizes for use to eradicate P. clarkii.

DOI： 10.3825/ece.18.79

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To examine appropriate cage traps and baits for capturing the North American invasive crayfish Procambarus clarkii, we conducted two field experiments (Experiments 1 and 2) in a pond in the Handayama Botanical Garden, Okayama, Japan. In Experiment 1, we set three kinds of cage traps (i.e., conger trap, crab trap, and shrimp trap) with the same artificial bait in the pond in late afternoon and then collected them early on the following morning. In Experiment 2, we set and collected shrimp cage traps separately with three kinds of baits, i.e., artificial bait for freshwater fish (Marukyu Co. Ltd., Saitama, Japan), fish sausage with cheese (Marudai Food Co. Ltd., Osaka, Japan), and frozen crayfish of P. clarkii, using the same pond and protocol as Experiment 1. In Experiment 1, the number of P. clarkii captured was significantly higher in the shrimp cage traps and conger cage traps compared with the crab cage traps. In addition, P clarkii over a wider range of body sizes including small and large crayfish were captured in the shrimp cage traps compared to the two other kinds of traps. In Experiment 2, the artificial bait was most effective to catch P. clarkii compared to the two other kinds of baits. Our results indicate that of the protocols tested the shrimp cage trap with the artificial bait is the most effective for capture and subsequent eradication of invasive P. clarkii.

DOI： 10.3825/ece.18.115

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Language：English   Publisher：Carcinological Society of Japan  

Collecting Macrobrachium shrimps for abundance estimation is challenging, especially in high gradient, boulder dominated streams. The recent advent of digital cameras could change the situation by enabling previously under-used snorkel counting to yield verifiable data. The validity and efficiency of underwater movie recording for shrimp census were tested and compared with those of underwater shrimp net collection and sweeping in a field experiment (1–4 adult shrimps/m²). Total length estimates from the video footage were compared with caliper measurements. Detection was not affected by species, sex, or shrimp density. Movie recording and shrimp net collection yielded high and constant detection probability of adult shrimps (0.955 and 0.874), in contrast to sweeping (0.097). The movie recording had higher efficiency than the other two methods. For juveniles, only shrimp net collection was valid as an abundance indicator, with a detection probability of 0.338. Accuracy of total length estimates made from the video footage did not differ between species or sex and was highly correlated with the actual measurements by digital caliper. These results confirm that in adult Macrobrachium shrimps, the movie recording is valid for body size and quantitative abundance estimation, but not in juveniles.

DOI： 10.18353/crustacea.44.0_39

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Authorship：Lead author,　Corresponding author   Language：English   Publisher：JAPANESE ASSOCIATION OF BENTHOLOGY  

In Lake Akan, Hokkaido, northern Japan, the local population of the native and endangered Japanese crayfish Cambaroides japonicus (De Haan, 1841) is extinct, whereas the signal crayfish Pacifastacus leniusculus (Dana, 1852), an invasive species from North America, has become established and rapidly increased. This study provides information about specimens of C. japonicus preserved by Dr. Saburo Hatta from the lake in 1872. The six specimens (two males and four non-ovigerous females) are valuable evidence of C. japonicus formerly inhabiting Lake Akan. The body sizes of the specimens were 24.4–29.5 mm in carapace length and 55.7–67.4 mm in total length, and the estimated age of the largest specimen was ten years, indicating that Lake Akan of that time provided a suitable habitat. Twenty-two ectosymbiotic crayfish worms (Annelida, Clitellata, Branchiobdellida) were found attached to the specimens. Three branchiobdellidan species were identified: Cirrodrilus cirratus Pierantoni, 1905, C. inukaii (Yamaguchi, 1934) and C. megalodentatus (Yamaguchi, 1934). This is the first record of the latter two species from Lake Akan.

DOI： 10.5179/benthos.69.90

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE ASSOCIATION OF BENTHOLOGY  

Official documents and archives suggest that the alien crayfish Pacifastacus leniusculus (Dana, 1852) was introduced into Japan from North America on five occasions from 1926 to 1930, and populations have survived in Hokkaido, Nagano, and Shiga Prefectures. The chemical conditions and biological environment of an established habitat near their original a release point in Akashina, Azumino City, Nagano Prefecture, were surveyed on four occasions in 1998 and 1999. Water quality (pH, DO, BOD) and WT were recorded seasonally at each of eight stations, and crayfish and other aquatic macro-organisms were collected. Some predatory fishes (Oncorhynchus mykiss, Anguilla japonica, and Lepomis macrochirus) that might actively eat juveniles of P. leniusculus were recorded. Individual density of P. leniusculus was relatively low compared to its other habitats in Japan. Only 52 crayfish were collected during this study, on 19 of 32 sampling occasions (eight sites, four times each). The shape of the acumen and the species composition of ectosymbiotic crayfish worms (Annelida: Clitellata: Branchiobdellidae) can be used as tools to trace the origin of introduced of P. leniusculus in Japan. The present crayfish from Nagano Prefecture have a relatively short acumen, different from those of specimens from Shiga and Hokkaido Prefectures. Furthermore, the crayfish worm Xironogiton victoriensis occurs only on crayfish from Akashina, Nagano Prefecture. The dates of introduction of P. leniusculus in Nagano (1926, 1929) also differ from those for Hokkaido (1930) and Shiga Prefecture (1926). These findings suggest that the regional population of P. leniusculus in Nagano has a different origin than those in Shiga and Hokkaido, having originated from crayfish that were introduced independently from North America.

DOI： 10.5179/benthos.66.26

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：BRILL ACADEMIC PUBLISHERS  

Agricultural channels can be important habitats for aquatic species inhabiting agricultural areas. However, water supply in agricultural channels can vary substantially with types of agriculture and irrigation/drainage system, and thereby affect the viability of local populations of aquatic species. In this study, we focused on the amphidromous freshwater atyid shrimp Caridina leucosticta. To clarify whether C. leucosticta utilizes agricultural channels as a habitat in relation to fluctuations in the water supply, we conducted a series of field surveys on the distribution of this shrimp in a rice paddy drainage channel (spring-fed channel) around the Furu River, central Japan, during July and December 2008. Large numbers of C. leucosticta had migrated into that drainage channel. Water from the adjacent rice paddies had disappeared by October, because irrigation was stopped, but the water level in the drainage channel was maintained by a supply of spring water. By mid-November the supply of spring water had almost disappeared, then the channel nearly dried up, and many shrimps were concentrated in an isolated water pool in the channel. Thus, habitat fragmentation of C. leucosticta occurred in terms of water (dis-)continuity. This water pool dried up completely by mid-December. We found many dead individuals of C. leucosticta in the dried-up area of the channel. These rest Its indicate that agricultural channels can be an important temporal habitat for amphidromous freshwater shrimps, but that the drying-up of the channels can lethally affect migrating atyid shrimps.

DOI： 10.1163/001121610X521190

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The North American invasive signal crayfish Pacifastacus leniusculus was designated as an 'Invasive Alien Species' by the Ministry of the Environment of Japan and by the Ministry of Agriculture, Forestry and Fisheries of Japan on 1 February 2006. We report the first record of P. leniusculus from the Kanto region (Chiba Prefecture), central Japan. Adult specimens of P. leniusculus were collected from the Tone River basin between September 2009 and January 2010. Ectosymbiotic crayfish worms (Annelida, Clitellata, Branchiobdellidae) were found on the crayfish and all specimens were identified as Sathodrilus attenuatus, which outside of its home range in North America occurs only in the Hokkaido and Fukushima Prefecture populations of P. leniusculus
thus suggesting that P. leniusculus in the Tone River basin was introduced from Hokkaido or Fukushima Prefecture. Signal crayfish is considered a cool water species and has been reported mostly in Hokkaido, northern Japan, but our findings strongly indicate that P. leniusculus has become established in a warm water area in central Japan, where the maximum water temperature is above 30°C in summer. These results indicate that P. leniusculus can inhabit warm water areas as well as cool areas and would be able to extend its distribution over a wide range in Japan. © The Japanese Association of Benthology.

DOI： 10.3800/pbr.5.165

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

Interval between reproductive events is an important factor for iteroparous animals because it determines the number of clutches throughout life. This study examined whether female size, clutch size, shell size and prenuptial molting affected the clutch interval in the hermit crab Pagurus nigrivittatus. Precopulatory guarding pairs of P. nigrivittatus were sampled in the field and kept in the laboratory until the female extruded eggs. The clutch interval of each female was assessed as one of two types of relatively "short" and "long" intervals by checking whether the guarded female had eggs and/or egg cases from the preceding brood or not when the guarding pair was collected. The clutch interval was longer in females with prenuptial molting than those without molting and these females usually grew larger at the prenuptial molt. This suggests that female P. nigrivittatus with a long interval might allocate energy into growth at the expense of the number of clutches during the current reproductive season. The allocation to growth is theoretically predicted to decrease with female size. Gastropod shell size is also known to affect the reproductive activity in hermit crabs. However, female size did not significantly affect the clutch interval in P. nigrivittatus, and the effect of gastropod shell size on clutch interval was not consistent with previous empirical studies. These results may be caused by differences in the gastropod species of shell occupied by the females of P. nigrivittatus.

DOI： 10.1007/s00227-008-0944-9

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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On 1 February 2006, the American signal crayfish Pacifastacus leniusculus together with another American crayfish (Orconectes rusticus), Cherax (native to Australasia) and Astacus (native to Europe) were designated 'invasive alien species' (hereafter termed IAS) by the Ministry of the Environment of Japan. Under the IAS Act, raising, importing, transferring, releasing, sowing and planting live IAS (including eggs, seeds and/or organs) are strictly regulated. Mitigation of ecological impacts and control of IAS are also important components of the IAS Act. Here, we report the current distribution and control status of the signal crayfish in Japan for the purpose of future management planning. Signal crayfish were originally imported from the Columbia River basin in northwestern North America between 1926 and 1930. The official records and anecdotal evidence suggest that signal crayfish had been intentionally or unintentionally introduced into streams or lakes in Hokkaido (the northernmost island of Japan) and Honshu (the main island of Japan). Although some founder populations have since disappeared, signal crayfish have been rapidly expanding their distribution ranges in Hokkaido as well as in Honshu over the last few decades. As of July 2007, the signal crayfish is distributed along the northern, eastern and central parts of Hokkaido as well as in three prefectures (Fukushima, Nagano and Shiga Prefectures) in Honshu. Since the enforcement of the IAS Act, crayfish control has been started in Hokkaido (in four lakes from 2006 and in four further lakes or streams from 2007) using baited traps and/or by hand with the aid of SCUBA equipment. On the other hand, the townspeople of Imazu (Shiga Prefecture) are proposing to protect the signal crayfish in Tankai Reservoir because the population has a unique Japanese name due to its introduction history. We discuss some of the problems and possible future directions concerning crayfish control.

DOI： 10.3739/rikusui.68.471

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING  

DOI： 10.1111/j.1444-2906.2007.01420.x

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CRUSTACEAN SOC  

Asymmetry in mutual predation can be important in species replacement between native and invasive species. Mutual predation between the endangered Japanese native crayfish species Cambaroides japonicus and the North American invasive crayfish Pacifastacus leniusculus was studied to assess the potential impact of P. leniusculus on C. japonicus. We made laboratory experiments to examine mutual predation (i) between individuals in pairs of the same and different species and (ii) among a group comprising single and mixed species. We also made field surveys to clarify the frequency of cannibalism of the two species. In laboratory experiments, the frequency of cannibalism was low by both two species, but predation by P. leniusculus on C. japonicus was severe and most P. leniusculus survived both in different species pairs and in mixed species groups. In field surveys, remains of the two crayfish species, which may have been caused by predation by the same species, i.e., cannibalism, were scanty. The results suggest that asymmetry in mutual predation can be an important cause of species replacement of the native C. japonicus by the invasive P. leniusculus in the field.

DOI： 10.1651/S-2652.1

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society for Aquaculture Science  

To clarify the effects of small herbivorous gastropods on the kelp Laminaria religiosa, we examined feeding traces left on the kelp by gastropods, and the morphology of gastropod radula. We conducted laboratory experiments with four species of the small herbivorous gastropods, Chlorostoma lischkei, Omphalius rusticus rusticus, Homalopoma amussitatum and Littorina sitkana, which frequently occur in habitats of L. religiosa in Hokkaido, Japan, to examine feeding traces left on a sheet of kelp gametophytes settled on styrene chambers or glass slides. In the experiments, all gastropod species fed on the kelp gametophytes both on the styrene chamber and the glass slide. We observed species-specific differences in feeding traces among gastropod species that were considered to be because of differences in the species-specific morphology and size of their radula and differences in feeding patterns. We observed similar traces in adult L. religiosa collected from its natural habitat in Esashi, Hokkaido, to those in our laboratory experiments, suggesting that the four gastropod species used in this study feed on the surface of the adult kelp.

DOI： 10.11233/aquaculturesci1953.54.217

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC FISHERIES SCIENCE  

DOI： 10.2331/suisan.72.447

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society for Aquaculture Science  

We made two laboratory experiments with small herbivorous gastropods Omphalius rusticus rusticus and Chlorostoma lischkei that frequently live in the habitats of the kelp Laminaria religiosa in southwest Hokkaido, Japan, to examine the effect of their grazing on L. religiosa at different water temperatures. In an experiment to find if O. rusticus rusticus feeds on a sheet of kelp gametophytes settled on styrene chambers or on glass slides at 5°C, 10°C and 15°C, O. rusticus rusticus fed on the kelp gametophytes even at the lowest water temperature, but food consumption increased as the water temperature increased. In an experiment to find if the two gastropod species feed on juvenile kelp sporophytes at 10°C and 15°C, many individuals of C. lischkei actively fed on juvenile kelp sporophytes at both water temperatures, but most individuals of O. rusticus rusticus showed no preference regardless of water temperature. Our results suggest that the potential impact of gastropod grazing on L. religiosa might differ between these gastropod species and water temperatures.

DOI： 10.11233/aquaculturesci1953.54.375

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：BRILL ACADEMIC PUBLISHERS  

DOI： 10.1163/156854005776759771

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

This is the first report of two North American branchiobdellidans, Sathodrilus attenuatus Holt, 1981, and Xironogiton victoriensis Gelder and Hall, 1990, on the signal crayfish, Pacifastacus leniusculus (Dana, 1852) introduced into Japan from the Columbia River system, northwestern North America. Signal crayfish from 12 localities in eastern and northern Hokkaido, Japan, were examined and each supported S. attenuatus. In addition, an individual of this species was found on preserved material from Ishikawa Prefecture, central Honshu. All of these branchiobdellidans reported in Hokkaido most probably came from the original population of signal crayfish introduced into Lake Mashu, Hokkaido, Japan, in 1930. It is suggested that the use of non-pathogenic branchiobdellidans, when present, provides an easy method for tracing the spread of crayfishes around Japan and could also be applied in other countries and continents. Specimens of X. victoriensis were only found on crayfish in a stream at Akashina in Nagano Prefecture, central Honshu, Japan. Although the signal crayfish appears to be displacing the endemic Japanese crayfish, C. japonicus, no native branchiobdellidans were found on any of the introduced signal crayfish examined.

DOI： 10.1007/s10530-004-8146-y

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society for Aquaculture Science  

To clarify the early ecology of amphidromous freshwater shrimps, larval drift in the freshwater area, larval distribution near the mouth of the river, and juvenile recruitment at the uppermost part of the tidal river area were studied in the Nishida River, western Japan. Juvenile recruitment was investigated by using artificial weed as settlement sites. In the river, zoeae of four shrimp species were collected within a short period after sunset, and all zoeae were in the first zoeal stage. About six million zoeae were estimated to pass downstream into the sea in 1998, but few zoeae were captured in the sea near the mouth of the river. Juveniles of three shrimp species, which have not previously been sampled in the river, were collected at the upper end of estuary. These results suggest that amphidromous freshwater shrimps widely disperse through the open sea and some juveniles migrate to other far rivers.

DOI： 10.11233/aquaculturesci1953.53.439

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society for Aquaculture Science  

Structure and artificial baits for shrimp cage traps were studied to develop an effective method to capture freshwater palaemonid shrimps. We examined the effect of (i) artificial weed as shelter within the trap, (ii) the entrance diameter of the trap, and (iii) artificial baits that were developed as useful baits for a crab cage trap in a previous study on the capture efficiency of the shrimp trap. The artificial weed within the shrimp trap had no effect to increase the number of the palaemonid shrimps captured per trap, but the difference of the entrance diameter of the shrimp trap affected the total catch. The capture efficiency of palaemonid shrimps was higher in the shrimp traps with the entrance diameter of 40mm and 50mm compared with 31mm and the crab cage trap. An appropriate diameter of the shrimp trap was considered to be 40mm in terms of preventing the capture of Japanese mitten crab (Eriocheir japonica), which may cause decreases of the catches of the palaemonid shrimps as the crab often damages the shrimp trap. Both artificial bait 1 (formula feed used for eel culture; 100g) and bait 2 (bait 1 (80g) + both diet coated with squid entrail extract (20g) and krill extract (20g) ) were considered to be useful for the trap of the palaemonid shrimps and to be as effective as frozen saury (Cololabis saira) . To efficiently capture palaemonid shrimps we should use the shrimp trap with an entrance diameter of 40mm using bait 1 that is cheaper than bait 2. The results of field experiments at eight rivers, three lakes and one marsh demonstrated that the shrimp trap with the entrance size of 40mm and bait 1 can be effective to capture not only the palaemonid shrimps but other freshwater shrimps and crayfish.

DOI： 10.11233/aquaculturesci1953.53.263

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Ovary formation, egg number and egg size was studied to examine the fecundity of the Japanese crayfish Cambaroides japonicus. From histological observations of ovaries. the ovarian eggs of C japonicus developed as asynchronous oocytes. Many well-grown oocytes were in the ovary after spawning, as well as before spawning. The smallest carapace length of ovigerous females was 15.2 mm. The pleopodal egg number ranged from 22 to 75 and significantly increased with female bode; size. Both egg diameters (2.13-2.50 mm) and weights (0.009-0.017 g) also significantly increased as the female body size increased, but were variable even for die same size crayfish. We conclude that larger females should be used for seed production of C japonicus because of its high fecundity and large eggs. Mature females spawn only once a year in natural habitats. but multiple spawning can be artificially induced within I year because of well-grown oocytes; that remain in the ovary after spawning. Thus, we recommend that an effective technique for artificial induction of multiple spawning be developed from our results. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aquaculture.2004.08.043

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CRUSTACEAN SOC  

The reproduction of the alien crayfish species Pacifastacus leniusculus inhabiting Lake Shikaribetsu, Hokkaido, Japan, was studied from August 2002 to August 2003.. Spawning was for a short period after mating in mid October. The eggs developed to eyed stage in June the following year and hatched in mid July. After remaining with their mother for several weeks, the juveniles became independent between late July and August. The egg numbers attached to pleopods of this crayfish significantly increased with the female body size. The time of spawning in Lake Shikaribetsu was similar to that of this crayfish living in North America and Europe reported by previous studies, but the time of egg hatching was later in Lake Shikaribetsu compared with some populations in North America and Europe. A comparison of our results of the reproduction of P. leniusculus with that of the endangered Japanese endemic crayfish species Cambaroides japouicus reported by previous studies showed that P. leniusculus has a markedly higher reproductive ability than C. japonicus in terns of egg numbers.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We developed a simple, easy method with a microplate to artificially incubate Japanese crayfish (Cambaroides japonicus) eggs for their cultivation. We prepared 6-, 12-, 24-, 48-, and 96-well microplates containing sterile water heated to 5, 10, 15, and 20 degreesC. Fourteen experimental groups for each water temperature were prepared for each of different water volumes (0.125-10 ml) in each well. One embryonic egg was placed in each well. Experiments were also conducted with water collected from the lake where the eggs were harvested from and held at 15 degreesC. In the microplates with sterile water, high proportions of eggs hatched (60-100%) at 15 degreesC in all volumes of water, although the proportions of hatching were low (0-20%) at 5, 10, and 20 degreesC. All eggs died in the experiments that used lake water. We conclude that the 96-well would be the most effective size to hatch crayfish eggs in, because of its convenience. This method using a microplate is simpler and easier compared with methods of previous studies to artificially incubate crayfish eggs, and therefore it might be useful to incubate eggs of other freshwater crayfish species. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aquaculture.2003.08.025

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CRUSTACEAN SOC  

Intra- and inter-specific competition for shelter, in relation to prior residence, sex differences, and body-size effects, was studied in the laboratory to assess the potential impact of the alien crayfish species Pacifastacus leniusculus on the endangered Japanese endemic crayfish species Cambaroides japonicus. The resident was placed in an aquarium, which contained a single shelter of preferred size for both C. japonicus and P. leniusculus. After 24 h, the intruder was introduced into the aquarium. In the experiments using different sex pairs of crayfish of approximately equal size, male residents had a significant prior residence effect against female intruders in both crayfish species in the intraspecific contests. However, residents of P. leniusculus dominated C. japonicus regardless of the sex in interspecific contests. In experiments using male crayfish pairs of different sizes, larger individuals had more successful possessions of the shelter against smaller individuals regardless of crayfish species. The body-size advantage strongly influenced the outcome of the both intra- and inter-specific contests regardless of residents or intruders and overcame the prior residence effect in both species. These results suggest that P. leniusculus is superior to C. japonicus in shelter competition if P. leniusculus invades the habitat of C. japonicus.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC FISHERIES SCIENCE  

The appropriate water velocity in artificial burrows for the Japanese crayfish species Cambaroides japonicus was studied. An experimental system of two artificial burrows (burrows A and B) of the same size was set in a large tank. The velocity of burrow A was 0 cm/s and that of burrow B was varied and set at 0 cm/s, 5 cm/s, 10 cm/s, 20 cm/s and 30 cm/s. The selection of these two burrows by C. japonicus was observed. No animals selected burrow B significantly more than burrow A above 10 cm/s. At 20 cm/s, some crayfishes were swept away and could not return to burrows because of the high water velocity. At 30 cm/s, most animals were swept away. We conclude that the appropriate water velocity for the suitability of artificial burrows and the immediate foraging area adjacent to the burrows should be as low as 5 cm/s.

DOI： 10.1046/j.1444-2906.2003.00627.x

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

Lethal limits of high temperature were studied to clarify the effects on the survival of the endangered Japanese crayfish species Cambaroides japonicus and the alien species Pacifastacus leniusculus. After the acclimation period for 2 weeks at 16degreesC, the temperature was raised at a rate of 1degreesC per week. As a result, the ultimate upper lethal temperatures of C. japonicus and P. leniusculus were 27.0 and 31.1degreesC, respectively, and the lethal temperature for P. leniusculus was significantly higher than for C. japonicus. The natural distributions of these two species are discussed in terms of the temperature tolerance.

DOI： 10.1046/j.1444-2906.2002.00491.x

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC FISHERIES SCIENCE  

Preference for artificial burrows by the endangered Japanese crayfish species Cambaroides japonicus was studied to improve its cultivation. The occupation of artificial burrows, which were made from straight polyvinyl chloride pipes of different internal diameters (Y, mm), by crayfishes of different total lengths (X, mm) was significantly (P <0.001, n=56) described by a linear regression: Y= 0.49X + 3.42 (19.0 less than or equal to X less than or equal to 70.2). Among burrows of different lengths [crayfish total length (TL) x 1, x 2, x 3, and x 4], crayfishes significantly preferred burrows that were greater than TL x 3 (P <0.001, n=588).

DOI： 10.1046/j.1444-2906.2001.00281.x

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

CiNii Article

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publisher：エヌ・ティー・エス  

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Language：Japanese  

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Language：Japanese   Publisher：日本水産資源保護協会  

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Language：Japanese   Publisher：Carcinological Society of Japan  

DOI： 10.18988/cancer.17.0_29

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Language：English  

DOI： 10.2331/suisan.73.664

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Language：Japanese   Publisher：水産大学校  

外来種であるウチダザリガニにとっての好適なサイズの人口巣穴を明らかにすることを目的として実験を実施した。灰色の直管型の塩ビ管を用いて人口巣穴を製作し、内径と長さの異なる巣穴に対する選択実験を行った。実験の結果、巣穴の内径については、全長(X、mm)と好んで選択された内径(Y、mm)の間にY＝0.68X－8.56という関係が認められた。巣穴の長さについては、全長の2倍以上の長さの巣穴が有意に選択される傾向があった。本研究の結果を、絶滅が危惧されているニホンザリガニの好適なサイズの人口巣穴を明らかにした過去の研究例と比較したところ、ウチダザリガニはニホンザリガニよりも隠れ場所には広い空間を必要としないことが示唆された。

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Other Link： http://ypir.lib.yamaguchi-u.ac.jp/fu/metadata/393

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Language：Japanese   Publisher：Carcinological Society of Japan  

DOI： 10.18988/cancer.11.0_15

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Language：Japanese   Presentation type：Poster presentation  

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Audience： General,　Governmental agency

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Audience： Infants,　Schoolchildren,　Junior students

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