Factors Affecting Distribution of Freshwater Shrimps and Prawns in the Hiwasa River, Southern Central Japan

CRUSTACEAN RESEARCH, NO. 41: 27–46, 2012

Factors affecting distribution of freshwater shrimps and prawns in the Hiwasa River, southern central Japan

Minoru Saito, Tadashi Yamashiro, Tatsuo Hamano and Kazuyoshi Nakata

Abstract.—Distribution of freshwater serving as major food items for some of the shrimps and prawns and its relationship larger predatory fishes (Maeda & Tachihara, with environmental factors were studied in 2004; Baumgartner, 2007). Crabs facilitate the Hiwasa River, Tokushima Prefecture, leaf litter and woody debris break down southern central Japan, to provide information through ingestion (Kobayashi, 2009). needed for conserving or propagating them Freshwater decapods may even be considered more effectively. Eleven species of decapod as umbrella species, since they often have crustaceans consisting of three palaemonids, similar habitat and diet preferences as six atyids, and two crabs were collected, of diadromous fishes and gastropods found in which eight species were diadromous. Results of the same region, in addition to life history canonical correspondence analysis showed that traits. substrate coarseness in addition to conventional Most of the freshwater shrimps found longitudinal variables largely affects overall in Japan are diadromous (Shokita, 1979; decapod distribution. Differences in distribution patterns among amphidromous species were Hamano et al., 2000), i.e. migrating between mainly explained by riverbank vegetation river and sea for breeding (McDowall, 2007). coverage and the two aforementioned variables. Abundances of diadromous shrimps are In contrast, distribution of a non–diadromous primarily determined by the accessibility atyid, Neocaridina denticulata, was suggested to of riverine habitat from the sea where be determined by relative ease for them to resist they undergo larval development (Miya & flood in that habitat, rather than by longitudinal Hamano, 1988; Greathouse et al., 2006) factors. These results insist on importance of and availability of preferred habitat for each coarse boulder bed and riverbank vegetation as species in the river (Iwata et al., 2003). Cross shrimp and prawn habitats at reach scale. The river structures including dams and weirs range of Caridina typus within a river differed have altered distribution of crustaceans, but between the Japanese Archipelago and the the negative impacts of these structures can Ryukyu Archipelago, and may be explained by be lessened with effective use of fishways limited low–temperature tolerance of this species. (e.g. Hamano et al., 2008). Incorporating these results and life history Fauna and distribution patterns under traits of the collected species, we propose a new natural condition are the fundamental classification system of distribution patterns for information to push forward conservation freshwater decapods on the Japanese Archipelago. programs of decapod crustaceans. In Japan, distribution patterns of atyid shrimps within rivers have been well documented in the Introduction context of longitudinal distribution (e.g. Decapod crustaceans are major Shokita, 1979). Differences in distribution components of unstable insular streams patterns among species were attributed to in tropical and temperate zones. Atyid topography of rivers and differences in shrimps facilitate recovery from flooding by migrating capabilities among them (Shokita, removing particulate organic matters that 1979; Suzuki et al., 1993; Usami et al., enhances algal growth (March & Pringle, 2008). These studies succeeded in describing 2002). Palaemonids as well as atyids are who lives where, especially the upper limit SHRIMP DISTRIBUTION IN SOUTHeRN CeNTRAL JAPAN 29 28 28 et al. M. Saito

Fig. 1. Map of the Hiwasa River System and the locations of the sampling stations. Arrows indicate the confluences of major tributaries and the main stream. O: Okugata River, K: Kitagawachidani River, Y: Yamagawachidani River.

of distribution, and how much, but additional use of two atyid shrimps in French Polynesia Fig. 2. Profile of the Hiwasa River System; a: Hiwasa and Yamagawachidani Rivers; b: Kitagawachidani and information is needed in order to identify using an ordination method. Although ranges Okugata Rivers. Dots represent the sampling stations. Arrows indicate the confluences of major tributaries and the type of habitat best suited for each species of Atyoida pilipes (Newport, 1847) and main stream. Y: Yamagawachidani River, O: Okugata River. K: Kitagawachidani River. of crustacean. For example, Caridina Caridina weberi De Man, 1892 overlapped multidentata Stimmpson, 1860 has high substantially in the studied rivers, they used climbing capability and is abundant in the habitat with different velocity. As shown upper reaches (e.g. Shokita, 1979; Hamano in Richards et al. (1993) and Fossati et al. central Japan, using a multivariate analysis. main stream, Hiwasa River, and three et al., 1995). However, it is still unclear why (2002), ordination techniques are effective Distribution pattern of each species and trend major tributaries, Kitagawachidani, the shrimp prefer upper reach habitat over tools to summarize complex relationships in of body size distribution among reaches Yamagawachidani and Okugata Rivers, lower reach habitat. Lack of such information community with key environmental factors. were compared with other regions in Japan. and flows into the Pacific Ocean at Hiwasa, is one of the major obstacles in identifying Its application to freshwater crustacean For future use in their conservation and Minami Town, Tokushima Prefecture (Fig. the environment essential for conserving community in Japan would yield beneficial habitat restoration programs, we categorized 1; 33°44’ N, 134°32’ e). We chose Hiwasa endangered species or propagating species information for identifying important habitat distribution patterns of freshwater decapod River System as the study site because natural valuable for fisheries. of each crustacean species in a river system crustaceans in rivers on the Japanese distribution patterns of freshwater decapod Aquatic organisms could be protected and for roughly estimating their probable Archipelago that are under influence of the crustaceans are well preserved there, owing more effectively, if we manage to answer this ranges prior to anthropogenic alterations of warm Kuroshio Current. to limited human alterations of river channel question by identifying factors determining channel or watershed. or riparian zone, and absence of carnivorous alien fishes (Hamano et al., 2000). Profile distribution pattern and fundamental criteria We investigated relationship between Materials and Methods for their habitat (Katoh & Takeuchi, 1991; environmental factors and distribution of of the 16.7 km main stream and the three Richards et al., 1993). Fossati et al. (2002) freshwater shrimps and prawns in the Hiwasa Sampling location major tributaries resemble logarithmic curves compared distribution patterns and habitat River, Tokushima Prefecture, southern Hiwasa River System consists of the (Fig. 2) and tidally influenced area extends SHRIMP DISTRIBUTION IN SOUTHeRN CeNTRAL JAPAN 31 30 30 et al. about 2.4 km from the river mouth bothM. Sinaito using a digital camera (Lumix DMC– by Hayashi (1999; 2000a–d; 2007) and the following six categories of modified the main stream and the Kitagawachidani FT1, Panasonic, Tokyo). Bait traps were Miyake (1983). Here, freshwater decapod Wentworth scale (Cummins, 1962): smooth River. A 4–m high mobile barrage is set in set accordingly to Nakata et al. (2011), as crustaceans are defined as the species whose bedrock or sand (<4 mm), gravel (5–16 mm), the Okugata River 1.2 km upstream of the follows. One crab trap (21×46×62 cm) and main habitats of matured individuals are in pebble (17–64 mm), cobble (65–256 mm), river mouth as a precaution measure against one prawn trap (24×24×36 cm), were set the freshwater area. Species found only in boulder (257 mm<), irregular bedrock. After high tide. Water quality is oligosaprobic with in each station. each trap was baited with the tidally influenced area were excluded. assigning numbers 1–6 to each of the above annual average of BOD being 0.5 mg/L at Pacific saury Cololabis saira and stuffed in Recently recruited shrimps were excluded categories, mean and standard deviation were Nagata located in the lower reach of the main a stainless cage to keep the bait from being from individual counts for multivariate calculated to express substrate coarseness stream (environmental Management Bureau, eaten by aquatic organisms soon after setting analyses, since they are undertaking upstream and heterogeneity, respectively, following Ministry of environment, 2011), which the trap. Sliced PVC pipes (caliber: 4 cm) migration following settlement and may not Bain et al. (1985). Discharge (m3/s) was enables this location to be a source for tap were attached to the entrances of prawn traps be regular inhabitants of that location. Recent calculated by multiplying cross–sectional water of Minami Town. Land uses around the to keep out Japanese mitten crabs Eriocheir recruits were distinguished from adults area by mean water velocity. Biological lower reaches are mainly residential area and japonica De Haan, 1885, which inhibits based on the smallest sizes of over–wintered variables, riverbank vegetation cover (%) rice paddies. Rest of the watershed is mostly catch of other crustaceans. Traps were set individuals in July or August described or and canopy cover above river channel (%), covered with planted coniferous forest of in the evening and retrieved the following shown in literatures (Shokita, 1979; Hamano were measured visually at 10% interval the Japanese cedar Cryptomeria japonica or day by noon. Submerged vegetation and & Hayashi, 1992; Hamano et al., 2000; when collecting crustaceans. Beside these the Hinoki cypress Chamaecyparis obtusa root masses along riverbanks were scooped Yamahira et al., 2007; Soomro et al., 2011), as variables, surface water temperature (°C) was and secondary evergreen oak forest. Cross– with a hand net (entrance: 28×33 cm, follows. Paratya compressa (De Haan 1844): measured using digital thermometer (National river structures including weirs and ground mesh size: 5 mm) for 10 minutes in each 20 mm TL, Caridina leucosticta Stimpson, BH–725, Matsushita electric Industrial Co. sills are set in the river system but with the station during the daytime. In boulder beds, 1860: 17 mm, C. typus H. Milne edwards, ltd., Tokyo) near a riverbank. exception of erosion control dams in the shrimps and prawns were chased into the 1837: 12 mm, C. multidentata: 22 mm, C. upper reaches of the main stream, all are hand net fixed near riverbank, using feet. serratirostris De Man, 1892: 8 mm. Carapace Data analysis less than 1 m in height. Watanabe & Kano Underwater video recording was used in the lengths in literatures were converted to TL Relationship between distribution of (2009) reported that weirs less than 1 m in present study because our preliminary study using measurement data in Hamano et al. crustaceans and environmental variables height did not affect distribution of decapod revealed that hand net scooping performs (2000). exception to the distinguishing rule was analyzed by canonical correspondence crustaceans in Miyazaki Prefecture, western poorly in collecting larger Palaemonidae was Neocaridina denticulata (De Haan, analysis (CCA, ter Braak, 1986). CCA is a Japan. We assumed that these small cross– prawns, especially in boulder bed (Saito et 1844), a non–diadromous species whose multivariate analysis based on an assumption river structures in the Hiwasa River did not al., unpublished data). Shrimps and prawns range within river does not change drastically that the species’ response to environment affect distribution of adult crustaceans. were searched for 10 minutes by flipping throughout its life history. gradient is unimodal (ter Braak, 1986; ter Thirty sampling stations were established over cobbles and boulders in each sampling Braak & Verdonschot, 1995). CCA relates in the Hiwasa River System, of which station during the daytime while recording. A Environmental variables the response directly to the measured 14, 10, five, and one were in the Hiwasa, ruler was placed near the spotted individuals eleven environmental variables were environmental variables (direct gradient Kitagawachidani, Yamagawachidani, and to measure their body sizes later on. taken for each sampling station to assess analysis) and shows relationship between Okugata Rivers, respectively (Fig. 1). each Large individuals were identified to their role in determining crustacean species, sites, and environmental variables station was labeled with the capital letter species, sexed from outlook of chelae and distribution within rivers. Distance from visually and simultaneously on the same of the river names, followed by a number abdomen, and measured to the nearest 0.1 river mouth (km), altitude (m), and ordination plane (ter Braak, 1986). Because given in the ascending order from the lower mm using a digital caliper (CD67–S15PS, gradient (‰) were obtained from 1/25000 of these properties, CCA is currently among reaches within that river. Lower most stations Mitsutoyo, Tokyo) on site, and released topographic maps published by Geospatial one of the most commonly used analyses for (H01, K01) in the main stream and the back into the sampling station of collection. Information Authority of Japan. Other revealing species–environment relationship Kitagawachidani River were situated in the Small individuals were brought back to physical environmental variables including in community ecology. tidally influenced area. erosion control dams the laboratory frozen, and identified and depth (cm), width (m), velocity (cm/s), and Detrended correspondence analysis exceeding 5 m in height were set in the main measured in the same manner. Individuals substrate coarseness and heterogeneity were (DCA) was run to confirm that the variables stream H12 and above. recorded on video were identified, sexed, recorded simultaneously with crustacean accounting for major environmental and measured to the nearest 5 mm. each collection. Velocity was measured with gradients were used in CCA. DCA and CCA Longitudinal distribution of decapod crusta- movie was viewed twice to prevent missing propeller type water current meter (VR–201, were performed using PC=ORD version ceans or double–counting crustaceans. Body Kenek, Tokyo) for five times at 60% depth 6 (mjm software design, Gleneden Beach, Decapod crustaceans were collected at parts measured were total length (TL, from at each of the five equidistant points set USA). For the abundance data, catches of all the 30 sampling stations in the Hiwasa River the tip of rostrum to the end of telson) across the river channel, and averaged over three sampling gears were pooled together System between 15 July and 4 August 2010. for palaemonids and atyids, and carapace 25 values. Substrate was quantified by for each species at each sampling station, Samples were collected using a combination width (widest part of carapace) for crabs. point intercept method using a quadrat with and log transformed (ln x+1) to improve of three methods: bait trapping, hand net Specimens were identified accordingly 36 measuring points. At each measuring normality. Species accounting for less scooping, and underwater movie recording to Hamano et al. (2000), supplemented point, substrate was classified into one of than 1% of the total catch were not used, SHRIMP DISTRIBUTION IN SOUTHeRN CeNTRAL JAPAN 31 30 et al. 31 about 2.4 km from the river mouth bothM. Sinaito using a digital camera (Lumix DMC– by Hayashi (1999; 2000a–d; 2007) and the following six categories of modified the main stream and the Kitagawachidani FT1, Panasonic, Tokyo). Bait traps were Miyake (1983). Here, freshwater decapod Wentworth scale (Cummins, 1962): smooth River. A 4–m high mobile barrage is set in set accordingly to Nakata et al. (2011), as crustaceans are defined as the species whose bedrock or sand (<4 mm), gravel (5–16 mm), the Okugata River 1.2 km upstream of the follows. One crab trap (21×46×62 cm) and main habitats of matured individuals are in pebble (17–64 mm), cobble (65–256 mm), river mouth as a precaution measure against one prawn trap (24×24×36 cm), were set the freshwater area. Species found only in boulder (257 mm<), irregular bedrock. After high tide. Water quality is oligosaprobic with in each station. each trap was baited with the tidally influenced area were excluded. assigning numbers 1–6 to each of the above annual average of BOD being 0.5 mg/L at Pacific saury Cololabis saira and stuffed in Recently recruited shrimps were excluded categories, mean and standard deviation were Nagata located in the lower reach of the main a stainless cage to keep the bait from being from individual counts for multivariate calculated to express substrate coarseness stream (environmental Management Bureau, eaten by aquatic organisms soon after setting analyses, since they are undertaking upstream and heterogeneity, respectively, following Ministry of environment, 2011), which the trap. Sliced PVC pipes (caliber: 4 cm) migration following settlement and may not Bain et al. (1985). Discharge (m3/s) was enables this location to be a source for tap were attached to the entrances of prawn traps be regular inhabitants of that location. Recent calculated by multiplying cross–sectional water of Minami Town. Land uses around the to keep out Japanese mitten crabs Eriocheir recruits were distinguished from adults area by mean water velocity. Biological lower reaches are mainly residential area and japonica De Haan, 1885, which inhibits based on the smallest sizes of over–wintered variables, riverbank vegetation cover (%) rice paddies. Rest of the watershed is mostly catch of other crustaceans. Traps were set individuals in July or August described or and canopy cover above river channel (%), covered with planted coniferous forest of in the evening and retrieved the following shown in literatures (Shokita, 1979; Hamano were measured visually at 10% interval the Japanese cedar Cryptomeria japonica or day by noon. Submerged vegetation and & Hayashi, 1992; Hamano et al., 2000; when collecting crustaceans. Beside these the Hinoki cypress Chamaecyparis obtusa root masses along riverbanks were scooped Yamahira et al., 2007; Soomro et al., 2011), as variables, surface water temperature (°C) was and secondary evergreen oak forest. Cross– with a hand net (entrance: 28×33 cm, follows. Paratya compressa (De Haan 1844): measured using digital thermometer (National river structures including weirs and ground mesh size: 5 mm) for 10 minutes in each 20 mm TL, Caridina leucosticta Stimpson, BH–725, Matsushita electric Industrial Co. sills are set in the river system but with the station during the daytime. In boulder beds, 1860: 17 mm, C. typus H. Milne edwards, ltd., Tokyo) near a riverbank. exception of erosion control dams in the shrimps and prawns were chased into the 1837: 12 mm, C. multidentata: 22 mm, C. upper reaches of the main stream, all are hand net fixed near riverbank, using feet. serratirostris De Man, 1892: 8 mm. Carapace Data analysis less than 1 m in height. Watanabe & Kano Underwater video recording was used in the lengths in literatures were converted to TL Relationship between distribution of (2009) reported that weirs less than 1 m in present study because our preliminary study using measurement data in Hamano et al. crustaceans and environmental variables height did not affect distribution of decapod revealed that hand net scooping performs (2000). exception to the distinguishing rule was analyzed by canonical correspondence crustaceans in Miyazaki Prefecture, western poorly in collecting larger Palaemonidae was Neocaridina denticulata (De Haan, analysis (CCA, ter Braak, 1986). CCA is a Japan. We assumed that these small cross– prawns, especially in boulder bed (Saito et 1844), a non–diadromous species whose multivariate analysis based on an assumption river structures in the Hiwasa River did not al., unpublished data). Shrimps and prawns range within river does not change drastically that the species’ response to environment affect distribution of adult crustaceans. were searched for 10 minutes by flipping throughout its life history. gradient is unimodal (ter Braak, 1986; ter Thirty sampling stations were established over cobbles and boulders in each sampling Braak & Verdonschot, 1995). CCA relates in the Hiwasa River System, of which station during the daytime while recording. A Environmental variables the response directly to the measured 14, 10, five, and one were in the Hiwasa, ruler was placed near the spotted individuals eleven environmental variables were environmental variables (direct gradient Kitagawachidani, Yamagawachidani, and to measure their body sizes later on. taken for each sampling station to assess analysis) and shows relationship between Okugata Rivers, respectively (Fig. 1). each Large individuals were identified to their role in determining crustacean species, sites, and environmental variables station was labeled with the capital letter species, sexed from outlook of chelae and distribution within rivers. Distance from visually and simultaneously on the same of the river names, followed by a number abdomen, and measured to the nearest 0.1 river mouth (km), altitude (m), and ordination plane (ter Braak, 1986). Because given in the ascending order from the lower mm using a digital caliper (CD67–S15PS, gradient (‰) were obtained from 1/25000 of these properties, CCA is currently among reaches within that river. Lower most stations Mitsutoyo, Tokyo) on site, and released topographic maps published by Geospatial one of the most commonly used analyses for (H01, K01) in the main stream and the back into the sampling station of collection. Information Authority of Japan. Other revealing species–environment relationship Kitagawachidani River were situated in the Small individuals were brought back to physical environmental variables including in community ecology. tidally influenced area. erosion control dams the laboratory frozen, and identified and depth (cm), width (m), velocity (cm/s), and Detrended correspondence analysis exceeding 5 m in height were set in the main measured in the same manner. Individuals substrate coarseness and heterogeneity were (DCA) was run to confirm that the variables stream H12 and above. recorded on video were identified, sexed, recorded simultaneously with crustacean accounting for major environmental and measured to the nearest 5 mm. each collection. Velocity was measured with gradients were used in CCA. DCA and CCA Longitudinal distribution of decapod crusta- movie was viewed twice to prevent missing propeller type water current meter (VR–201, were performed using PC=ORD version ceans or double–counting crustaceans. Body Kenek, Tokyo) for five times at 60% depth 6 (mjm software design, Gleneden Beach, Decapod crustaceans were collected at parts measured were total length (TL, from at each of the five equidistant points set USA). For the abundance data, catches of all the 30 sampling stations in the Hiwasa River the tip of rostrum to the end of telson) across the river channel, and averaged over three sampling gears were pooled together System between 15 July and 4 August 2010. for palaemonids and atyids, and carapace 25 values. Substrate was quantified by for each species at each sampling station, Samples were collected using a combination width (widest part of carapace) for crabs. point intercept method using a quadrat with and log transformed (ln x+1) to improve of three methods: bait trapping, hand net Specimens were identified accordingly 36 measuring points. At each measuring normality. Species accounting for less scooping, and underwater movie recording to Hamano et al. (2000), supplemented point, substrate was classified into one of than 1% of the total catch were not used, SHRIMP DISTRIBUTION IN SOUTHeRN CeNTRAL JAPAN 33 32 32 et al.

concerning that rare species are overweighedM. Saito had steeper gradient in the upper reaches in these analyses (Minchin, 1987). Since compared to its major tributaries (Fig. 2, detrending process in DCA destroys original Table 1). Riverbank vegetation occurred axes in correspondence analysis, eigenvalues mainly in the lower reaches but it did are not indicative parameters for relative occur sporadically in the upper reaches, importance of the DCA axes (Palmer, 1993). especially in the Kitagawachidani and the Instead, correlation coefficients between Yamagawachidani Rivers. Canopy cover was relative euclidean distance in the original generally dense in the upper reaches. species space and euclidean distance in the ordination space were used. To prevent Longitudinal distribution of decapod crusta- multicollinearity problem, either one of ceans the environmental variables with variance A total of 1048 decapod crustaceans inflation factor exceeding 20 was dropped representing four families, seven genera, from further analyses. Variables with low and eleven species were collected in the interest correlation (<0.4) with the first two present study (Figs. 3, 4), of which eight CCA axes were dropped as well. Altitude species, Macrobrachium japonicum (De and substrate heterogeneity were dropped Haan, 1849), M. formosense Bate, 1868, P. in the due process. Weighted average scores compressa, C. leucosticta, C. multidentata, were used for site scores because they are C. serratirostris, C. typus, and E. japonica, less affected by noise in the measured values were diadromous. Longitudinal distribution of the environmental variables (McCune & varied species to species. Macrobrachium Grace, 2002). Axes were scaled to optimize japonicum was collected in lower to middle plots of species. Validity of the first axis was reaches excluding tidally influenced area, tested using Monte Carlo permutation test and was most abundant in the lower reaches (999 iterations), with p<0.05 being valid. of freshwater area, e.g. H03 (Fig. 3a). Macrobrachium formosense also occurred in lower to middle reaches but the prawn Results was abundant only in the tidally influenced area. Palaemon paucidens De Haan, 1849 Environment of the sampling stations occurred in the middle reaches at H05 and environments of the sampling stations H06. There exist two distinct groups (at least are summarized in Table 1. Hiwasa River at subspecies level) in P.paucidens (Hayashi,

Table 1. Physical and biological environments of the sampling stations in the Hiwasa River System St. No. Dis RM Slope Depth Width Velocity Discharge Temp. Sub. Mn. Sub. SD Vege Canopy (km) (‰) (cm) (m) (m/s) (m3/s) (°C) (%) (%) H01 1.9 1.4 63.4 29.8 25.8 3.481 22.2 3.3 0.72 50.0 0.0 H02–03 3.5 1.4 50.8 27.4 48.6 4.146 20.5 3.1 0.93 50.0 0.0 H04–05 5.9 5.7 44.7 32.5 37.0 3.989 21.1 3.2 1.14 10.0 20.0 H06–09 9.8 11.7 45.3 19.4 27.0 1.474 20.2 4.3 0.73 0.0 25.0 H10–12 15.5 42.6 31.1 9.4 25.0 0.588 19.9 4.5 0.62 3.3 83.3 H13–14 20.1 44.4 27.3 7.2 36.7 0.505 18.0 4.2 0.67 0.0 100.0 K01 1.9 1.9 73.6 25.3 11.8 1.672 20.4 3.0 0.86 30.0 20.0 K02–04 4.0 2.6 55.4 10.7 17.1 0.791 20.0 3.4 0.90 6.7 16.7 K05–07 10.3 10.4 75.3 6.6 15.4 0.387 23.9 3.7 0.92 6.7 36.7 K08–10 14.1 17.8 22.9 4.2 11.3 0.059 22.5 3.6 0.88 6.7 66.7 O01 2.8 2.3 17.0 7.6 4.1 0.042 20.4 1.6 0.95 0.0 0.0 Fig. 3. Distribution of palaemonid prawns (a) and atyid shrimps (b) in the Hiwasa River System. Y01–02 9.4 8.6 81.2 10.5 10.2 0.425 21.7 3.7 0.83 10.0 55.0 Y03–05 11.1 14.9 31.4 4.2 18.9 0.163 20.2 4.0 0.79 13.3 76.7 Dis. RM: distance from the river mouth, Sub. Mn: substrate coarseness, Sub. SD: substrate heterogeneit SHRIMP DISTRIBUTION IN SOUTHeRN CeNTRAL JAPAN 35 34 34 et al. M. Saito (Kendall tau rank correlation, τ=–0.12, d.f.=119, p>0.05; Fig. 5). Population of some lower–reach stations (H03, K02) consisted only of larger individuals. In the lower reaches, females were abundant, tended to be larger (τ=–0.19, d.f.=110, p<0.05), and higher in percentage of ovigerous individuals (Fig. 5). In M. formosense, males collected H04 and above consisted only of larger individuals (80.6±0.7 mm TL, mean±SD) unlike those of H01–H03 (68.7±19.4 mm). No female M. formosense were collected in the former region. Total length of P. compressa increased with increasing distance from the river mouth, irrespective of inclusion (τ=0.59, d.f.=427, p<0.0001) or exclusion (τ=0.15, df=184, p<0.01) of recent recruits (Fig. 6). Similar trend was seen in C. leucosticta (K01: 20.87±6.8 mm TL, K02: 26.1±4.4 mm, K03–08: 29.1±1.7 mm; all: τ=0.32, d.f.=125, p<0.0001, adults: τ=0.20, d.f.=107, p<0.05) but the maximum TL was almost the same throughout its range (K01: 32.7 mm, Fig. 4. Distribution of crabs in the Hiwasa River System. K02: 34.7 mm, K03–08: 31.5 mm). Caridina Fig. 5. Size frequency distributions of Macrobrachium serratirostris collected in the brackish water japonicum at each sampling stations in the Hiwasa River. Open, solid, grey and cross hatched bras indicate stations (15.9±3.1 mm) were larger than those juvenile, male (left), female, and ovigerous female of the freshwater stations (13.9±2.1 mm; t– (right) individuals, respectively. Number of ovigerous 2007). Based on its large body size, small multidentata was found in the middle and test, t=3.38, d.f.=69, p<0.01) and the former females in parentheses. egg diameter and gradient of the river, P. upper reaches, and was abundant in the consisted of higher percentage of ovigerous paucidens collected in the Hiwasa River is upper reaches of both the main stream and female (65.1% vs. 8.0%). Size composition most likely the B–type that is usually found two long tributaries, Kitagawachidani and of C. typus is shown in Fig. 7, majority of in lower to middle reaches of rivers. Since Yamagawachidani Rivers. Neocaridina which was collected in K02. Body sizes of the total number of individuals collected denticulata, the sole non–diadromous atyid C. multidentata did not show correlation to concurrently was merely two, this species species found in the Hiwasa River System, was excluded from any further investigation. was collected in the upper reaches of the Atyid shrimps were found in almost long tributaries and O01. No other decapod entire stretch of the river system but were crustaceans were collected in O01. absent in the farthest upper reach stations in Two species of crabs were collected in the Table 2. Summary of DCA and CCA the main stream (Fig. 3b). Distribution of C. present study (Fig. 4). Eriocheir japonica was Axes 1 2 3 Total inertia leucosticta, C. typus, and C. serratirostris found in almost all of the sampling stations, DCA: was generally limited to the lower reaches but did not occur in tidally influenced area or eigenvalue 0.539 0.144 0.056 with a few exceptions of C. leucosticta. upper most stations of the main stream. The r2 values for variance explained* 0.658 0.117 0.026 While C. leucosticta and C. serratirostris species was abundant in the middle reaches. were most abundant in the tidally influenced Geothelphusa dehaani (White, 1847) was CCA: area, C. typus was absent there and appeared collected in the upper reaches of both the eigenvalues 0.438 0.221 0.107 1.719 in high density in the lowest part of main stream and the long tributaries, and was Pearson correlation species-environment 0.903 0.786 0.608 freshwater area i.e. K02. Paratya compressa most abundant in the farthest upper reach Cumulative % variance explained in species data 25.5 38.3 44.6 was widely distributed in the atyids’ range, station of the main stream, H14. r2 values for variance explained* 0.534 0.176 0.027 and was abundant in the middle reaches Significance of the first axis p<0.001 and scarce in the tidally influenced area or Size distribution along stream upper reaches of the main stream. Caridina Body sizes of male M. japonicum was *: Correlation coefficient between relative euclidean distance in the original species space and euclidean distance not correlated to the distance from the sea in the ordination space. SHRIMP DISTRIBUTION IN SOUTHeRN CeNTRAL JAPAN 35 34 et al. 35 M. Saito (Kendall tau rank correlation, τ=–0.12, d.f.=119, p>0.05; Fig. 5). Population of some lower–reach stations (H03, K02) consisted only of larger individuals. In the lower reaches, females were abundant, tended to be larger (τ=–0.19, d.f.=110, p<0.05), and higher in percentage of ovigerous individuals (Fig. 5). In M. formosense, males collected H04 and above consisted only of larger individuals (80.6±0.7 mm TL, mean±SD) unlike those of H01–H03 (68.7±19.4 mm). No female M. formosense were collected in the former region. Total length of P. compressa increased with increasing distance from the river mouth, irrespective of inclusion (τ=0.59, d.f.=427, p<0.0001) or exclusion (τ=0.15, df=184, p<0.01) of recent recruits (Fig. 6). Similar trend was seen in C. leucosticta (K01: 20.87±6.8 mm TL, K02: 26.1±4.4 mm, K03–08: 29.1±1.7 mm; all: τ=0.32, d.f.=125, p<0.0001, adults: τ=0.20, d.f.=107, p<0.05) but the maximum TL was almost the same throughout its range (K01: 32.7 mm, Fig. 4. Distribution of crabs in the Hiwasa River System. K02: 34.7 mm, K03–08: 31.5 mm). Caridina Fig. 5. Size frequency distributions of Macrobrachium serratirostris collected in the brackish water japonicum at each sampling stations in the Hiwasa River. Open, solid, grey and cross hatched bras indicate stations (15.9±3.1 mm) were larger than those juvenile, male (left), female, and ovigerous female of the freshwater stations (13.9±2.1 mm; t– (right) individuals, respectively. Number of ovigerous 2007). Based on its large body size, small multidentata was found in the middle and test, t=3.38, d.f.=69, p<0.01) and the former females in parentheses. egg diameter and gradient of the river, P. upper reaches, and was abundant in the consisted of higher percentage of ovigerous paucidens collected in the Hiwasa River is upper reaches of both the main stream and female (65.1% vs. 8.0%). Size composition most likely the B–type that is usually found two long tributaries, Kitagawachidani and of C. typus is shown in Fig. 7, majority of in lower to middle reaches of rivers. Since Yamagawachidani Rivers. Neocaridina which was collected in K02. Body sizes of the total number of individuals collected denticulata, the sole non–diadromous atyid C. multidentata did not show correlation to concurrently was merely two, this species species found in the Hiwasa River System, was excluded from any further investigation. was collected in the upper reaches of the Atyid shrimps were found in almost long tributaries and O01. No other decapod entire stretch of the river system but were crustaceans were collected in O01. absent in the farthest upper reach stations in Two species of crabs were collected in the Table 2. Summary of DCA and CCA the main stream (Fig. 3b). Distribution of C. present study (Fig. 4). Eriocheir japonica was Axes 1 2 3 Total inertia leucosticta, C. typus, and C. serratirostris found in almost all of the sampling stations, DCA: was generally limited to the lower reaches but did not occur in tidally influenced area or eigenvalue 0.539 0.144 0.056 with a few exceptions of C. leucosticta. upper most stations of the main stream. The r2 values for variance explained* 0.658 0.117 0.026 While C. leucosticta and C. serratirostris species was abundant in the middle reaches. were most abundant in the tidally influenced Geothelphusa dehaani (White, 1847) was CCA: area, C. typus was absent there and appeared collected in the upper reaches of both the eigenvalues 0.438 0.221 0.107 1.719 in high density in the lowest part of main stream and the long tributaries, and was Pearson correlation species-environment 0.903 0.786 0.608 freshwater area i.e. K02. Paratya compressa most abundant in the farthest upper reach Cumulative % variance explained in species data 25.5 38.3 44.6 was widely distributed in the atyids’ range, station of the main stream, H14. r2 values for variance explained* 0.534 0.176 0.027 and was abundant in the middle reaches Significance of the first axis p<0.001 and scarce in the tidally influenced area or Size distribution along stream upper reaches of the main stream. Caridina Body sizes of male M. japonicum was *: Correlation coefficient between relative euclidean distance in the original species space and euclidean distance not correlated to the distance from the sea in the ordination space. SHRIMP DISTRIBUTION IN SOUTHeRN CeNTRAL JAPAN 37 36 36 et al. M. Saito

Fig. 7. Size frequency distribution of Caridina typus collected in the Hiwasa River System. Open and solid bars indicate non-ovigerous and ovigerous individuals, respectively.

Fig. 9. DCA biplot of the species (●) and the sampling stations (∆). M fo: Macrobrachium formosense, M ja: M. japonicum, C se: Caridina serratirostris, C le: C. leucostica, C ty: C. typus, P co: Paratya compressa, C mu: C. multidentata, N de: Neocaridina denticulata, E ja: Eriocheir japonica, G de: Geothelphusa dehaani.

Fig. 7. Size frequency distribution of Caridina typus collected in the Hiwasa River System. Open and solid bars indicate non-ovigerous and ovigerous individuals, respectively.

river mouth, both in male (τ=0.46, d.f.=74, axis correlated positively with distance from p<0.0001) and female (τ=0.63, d.f.=47, the river mouth, gradient, and canopy cover p<0.0001; Fig. 8). No such relationship was and negatively with discharge (Table 3). observed for G. dehaani(τ=–0.17, d.f.=16, The second axis correlated positively with p>0.05). substrate coarseness but not evidently so with the remaining variables. Fig. 8. Relationship between carapace width and Ordination distance from the sea in male (above) and female Results of CCA generally agreed with that (below) Eriocheir japonica. In DCA, distribution of decapod of DCA, and the correlation coefficient values crustaceans was explained mainly by the of the first two axes were identical in the two first two axes (Table 2). Species found in analyses (Figs. 9, 10, Table 2), indicating that the lower reaches such as C. serratirostris major environmental gradients influencing and M. formosense were placed on the the upstream distance from the sea (τ=0.10, distribution of the crustaceans were included right side of the firs axis. Macrobracium in CCA. The first two axes of CCA explained d.f.=108, p>0.05). For N. denticulata, some japonicum and Paratya compressa were in smaller individuals were collected in O01 38.3% of the variance in species’ distribution the central region and G. dehaani was on and the Monte Carlo permutation test showed (19.8±7.1mm) unlike in Yamagawachidani the left end of the axis (Fig. 9). Along the Fig. 6. Size frequency distributions of Paratya significance (p<0.001) of the first axis (Table River and upper reaches of Kitagawachidani second axis, N. denticulata was ordinated at compressa at each sampling stations in the Hiwasa River (26.5±2.3 mm). 2). A species’ plot in the ordination plane River. Open and solid bars indicate non-ovigerous the top, shrimps found in lower and middle Carapace width of E. japonica increased shows average habitat of that species. Species and ovigerous individuals, respectively. Number of reaches in the middle and E. japonica and abundant in the lower reaches such as C. ovigerous individuals in parentheses. in relation to the increasing distance from the C. multidentata was at the bottom. The first SHRIMP DISTRIBUTION IN SOUTHeRN CeNTRAL JAPAN 39 38 38 et al. M. Saito with substrate coarseness and velocity. Discussion Canonical coefficients show unique contribution of each environmental variable Factors determining overall distribution to the axis when other variables are held Results of CCA showed that longitudinal constant. Based on the canonical coefficient factors e.g. distance from the river mouth values, the first axis is predominantly and gradient primarily determine distribution explainable by distance from the river mouth, of freshwater crustaceans (Fig. 10, Table 4) while the second axis is mainly constructed and these results are in congruence with the by substrate coarseness, followed by gradient concept of longitudinal distribution proposed and riverbank vegetation. by Shokita (1979). In addition, the present In CCA, environmental variables are study revealed that substrate coarseness represented with vectors. effect of these and riverbank vegetation coverage serve variables on distribution of a species can as indicators for crustacean distribution. be interpreted by dropping a perpendicular Although these two variables co–vary with line from the species plot to the variable’s distance from the river mouth, they have vector that is extended imaginarily to the unique contributions to the crustacean both directions. The distance between this distribution, which can be inferable from intersection and the origin indicates the the canonical coefficient values. The results relative strength of the variable’s effect when of the present study indicate that leaving compared to that of the other species. The riverbank vegetation intact, as well as direction of a vector shows the direction maintaining boulder transport from the upper at which the environment variable affects reaches to the lower reaches, is an effective the species’ distribution the most. Species way to conserve daytime habitat of the abundant in the lower reaches differed in shrimps and the prawns. their preference of riverbank vegetation; M. Limiting factors for shrimp distribution formosense showed weaker association to Two species of shrimps, C. leucosticta, riverbank vegetation compared to the three C. serratirostris, and prawn, M. formosense, atyid species (Fig. 10). Shrimps abundant in were abundant in the brackish water area of the middle reaches such as M. japonicum and the Hiwasa River System (Fig. 3). Of the P. compressa were generally associated with three, M. formosense was the only species coarse substrate but N. denticulata preferred continuously distributed between lower smaller substrate. reaches and middle reaches. Wider range of M. formosense can be explained by the

Table 3. Correlation (tau) between the environmental Table 4. Interset correlation and canonical coefficients variables and the first two axes of DCA of the environmental variables with the first two Fig. 10. CCA biplot of the species (●) and the sampling stations (∆). Species’ abbreviations are as in figure 9. The env. Variables* Axis 1 Axis 2 canonical axes of CCA abbreviations for the environmental variables are as follows. Vege: riverbank vegetation coverage, Disc: discharge, Interset Correlation Canonical coefficient Velo: velocity, Sub Mn: substrate coarseness, Dis RM: distance from the river mouth, Cano: canopy coverage. Sub Mn -0.228 -0.533 Axes 1 2 1 2 Dis RM -0.654 -0.598 Sub Mn -0.538 -0.407 0.080 -0.887 Slope -0.595 -0.590 Dis RM -0.859 0.104 -1.024 -0.076 Depth 0.544 0.258 Slope -0.553 0.084 0.076 0.433 serratirostris and M. formosense were on the the bottom. The first axis was associated Width 0.452 0.286 right side, P. compressa, M. japonicum and N. with longitudinal variables and showed Depth 0.394 -0.160 0.087 -0.306 Velocity 0.147 -0.129 Width 0.425 -0.279 0.190 -0.138 denticulata in the center, and G. dehaani was strong negative correlation, –0.859, with Discharge 0.502 0.207 on the left side of the ordination biplot (Fig. distance from the river mouth, and moderate Velo 0.025 -0.329 -0.251 -0.212 Vegetation 0.218 0.356 Disc 0.415 -0.310 -0.179 -0.398 10). Along the second axis, N. denticulata correlation with gradient, canopy, riverbank Canopy -0.507 -0.467 was at the top, whereas M. japonicum, vegetation, and substrate coarseness (Table Vege 0.471 0.151 0.258 0.375 *environmental variables; Sub Mn: substrate Cano -0.579 0.265 0.084 0.224 P. compressa, and E. japonica were at 4). The second axis correlated negatively coarseness, Dis RM: distance from the river mout SHRIMP DISTRIBUTION IN SOUTHeRN CeNTRAL JAPAN 39 38 et al. 39 M. Saito with substrate coarseness and velocity. Discussion Canonical coefficients show unique contribution of each environmental variable Factors determining overall distribution to the axis when other variables are held Results of CCA showed that longitudinal constant. Based on the canonical coefficient factors e.g. distance from the river mouth values, the first axis is predominantly and gradient primarily determine distribution explainable by distance from the river mouth, of freshwater crustaceans (Fig. 10, Table 4) while the second axis is mainly constructed and these results are in congruence with the by substrate coarseness, followed by gradient concept of longitudinal distribution proposed and riverbank vegetation. by Shokita (1979). In addition, the present In CCA, environmental variables are study revealed that substrate coarseness represented with vectors. effect of these and riverbank vegetation coverage serve variables on distribution of a species can as indicators for crustacean distribution. be interpreted by dropping a perpendicular Although these two variables co–vary with line from the species plot to the variable’s distance from the river mouth, they have vector that is extended imaginarily to the unique contributions to the crustacean both directions. The distance between this distribution, which can be inferable from intersection and the origin indicates the the canonical coefficient values. The results relative strength of the variable’s effect when of the present study indicate that leaving compared to that of the other species. The riverbank vegetation intact, as well as direction of a vector shows the direction maintaining boulder transport from the upper at which the environment variable affects reaches to the lower reaches, is an effective the species’ distribution the most. Species way to conserve daytime habitat of the abundant in the lower reaches differed in shrimps and the prawns. their preference of riverbank vegetation; M. Limiting factors for shrimp distribution formosense showed weaker association to Two species of shrimps, C. leucosticta, riverbank vegetation compared to the three C. serratirostris, and prawn, M. formosense, atyid species (Fig. 10). Shrimps abundant in were abundant in the brackish water area of the middle reaches such as M. japonicum and the Hiwasa River System (Fig. 3). Of the P. compressa were generally associated with three, M. formosense was the only species coarse substrate but N. denticulata preferred continuously distributed between lower smaller substrate. reaches and middle reaches. Wider range of M. formosense can be explained by the

physical environment in their upstreamM. Saito what Suzuki et al. (1993) and Sato et al. N. denticulata is thought to be determined & Lyons, 1993). This distribution trend migration route. even though all three (1994) reported for Kagoshima Prefecture, in by relative ease for them to resist high flow indicates that the two species are growing species prefer quieter waters, there exists that they are absent in the lower reaches. Sato condition in that habitat, but not by the as they migrate upstream. It was also the noticeable difference in preferable daytime et al. (1994) explained such pattern in the distance from the river mouth or elevation. case for catadromous E. japonica, which habitat between the two atyid and the Manose River by effect of non–point source In case of turbulent medium scale rivers agrees with previous findings by Kobayashi palaemonid species. Caridina serratirostris pesticide pollution from nearby rice paddies like the Hiwasa River System, the upper & Matsuura (1991). The fact that large C. prefer leaf litters and riverbank vegetation, in the lower reaches. However, it is not the reaches with relatively moderate gradient leucosticta was also collected in brackish and often found hiding under boulders case for the Hiwasa River System, since and low discharge are suggested to be the water stations unlike P. compressa suggests (Hamano et al., 2008). Caridina leucosticta closely related amphidromous atyid shrimps best habitat of the shrimp. In fact, range of that some individuals cease upstream is also abundant in riverbank vegetation are found to inhabit there at the highest N. denticulata in the Kitagawachidani River migration and become regular inhabitant (Hamano et al., 2008). On the other hand, densities within the river system. Instead, agrees with that of Rhinogobius flumineus there, as previously reported by Yamahira et M. formosense do not necessarily rely on relative ease for juveniles to stay there under (Saito, unpublished data), a land–locked al. (2007). riverbank vegetation; while juveniles prefer high flow condition seems to be the solution. goby vulnerable to high concentration salt Caridina serratirostris showed different shallow area and vegetation, adults usually Unlike all the other atyids found in the water that has amphidromous congeners. distribution pattern, with larger individuals hide under boulders and occasionally in Hiwasa River, N. denticulata is a non– and ovigerous females aggregated in Habitat use of Macrobrachium prawns vegetation especially during the summer diadromous species that lays large eggs brackish water area, lower end of its range. Distribution patterns of Macrobrachium (Saito, unpublished data). in small number (Hayashi, 2007). They This trend may insist on presence of active prawns in the Hiwasa River System agreed Besides the lower reaches, moderately hatch as post larvae that closely resemble downstream migration by females. However, with previous reports (e.g. Shokita, 1979; flowing area with vegetation occurs in juvenile shrimp in shape (Mizue & Iwamoto, concerning poor upstream migration or Suzuki et al., 1993) in that the range of M. the upper reaches of the Kitagawchidani 1961). Lower reaches seem to be potential flow resisting capability of this species japonicum extends somewhat upper reach and Yamagawachidani Rivers, but habitat for N. denticulata under regular (e.g. Hamano et al. 2008), bulkier females of M. formosense, but with considerable Caridina shrimps are rare in the latter flow condition because of moderate current may simply be less tolerant to high flow overlap. In spite of the overlap, the two area. This phenomenon is not because of flow and abundant emergent or submerged condition than males. Detailed and frequent species seem to be facing little interspecific C. leucosticta’s lack of will to undertake vegetation, structure that the species show survey would be needed to confirm where competition there. Results of CCA have upstream migration. In September and positive stereotaxis to (Niwa & Yokoyama, in river this species mates and if difference identified difference in habitat utilization October, C. leucosticta accounted for nearly 1993). However, this river fluctuates greatly in frequency of ovigerous female among between the two species at macro habitat, half of the roughly three hundred specimens in its flow condition, often inundating reaches is a constantly seen phenomenon in other word, reach scale; while the former collected in H03, but they were seldom entire stretch of riverbank vegetation after over the mating season, insisting on active prefer coarse boulder bed, the latter shows collected in H04 (Saito et al., unpublished heavy rainfall. Concerning that Neocaridina downstream migration by ovigerous females weak association with vegetation. Ohno et data), suggesting that their upstream shrimps are vulnerable to high concentration (e.g. Ohtomi & Nakabayashi, 1999; Bauer & al. (1977) noted that in the Shimanto River, migration is blocked by some physical salt water (e.g. Shokita, 1976), small Delahoussaye, 2008). south western Japan, M. japonicum prefer barrier between these two stations. Nakata juveniles of N. denticulata seem to have little In contrast to P. compressa, females more swiftly flowing area compared to M. et al. (2010) reported that C. leucosticta chance of regaining its position in the lower of M. japonicum were larger in the lower formosense in the daytime, when looked at occurs in high density in the middle reaches reaches of the main stream, once struck with end of their range, with proportion of microhabitat (specific environment within a of Toyokawa River, Aichi Prefecture, central a flooding event. ovigerous individuals being higher there reach) scale. Since coarse boulder bed and Japan, which is roughly 20 km upstream of Okugata River was an exception to such (Fig. 5). Such pattern of distribution in dense riverbank vegetation are indicative the river mouth. This result suggests that trend. There, N. denticulata was abundant at amphidromous palaemonids insists on environments for swift and moderatel flow C. leucosticta is capable of migrating much the station located in proximity to the sea, presence of downstream migration for larval conditions, the present study and Ohno et al. longer distance upstream than what has been less than 3 km from the river mouth (Fig, release (e.g. Ohtomi & Nakabayashi, 1999; (1977) are said to be in agreement, although observed in the present study, if the gradient 3b, Table 1). This is presumably because Bauer & Delahoussaye, 2008). The authors different in its scale. These results suggest is gradual and vegetation continuously cover of the tributary’s moderate flow and low are currently preparing another paper on that the two amphidromous Macrobrachium river bank. Thus, gradient and continuity discharge owing to its short channel length. this topic based on year–round sampling to prawns moderately segregate their habitat of riverbank vegetation in the migration Downstream of O01 is a shallow wetland discuss presence and details of such life– at both of micro and macro scales in the route, rather than sole presence of isolated with dense vegetation cover of emergent history adaptation in this species. similar way, enabling them to coexist in their preferable habitat (riverbank vegetation), are plants. In case of flooding event, washed considerably overlapping range. Inter–regional difference in distribution suggested to be the determinant factors for C. away shrimps inhabiting the Okugata River Distribution patterns of the shrimps leucosticta’s upper limit of distribution. are thought to have higher chance of keeping Size distribution along the stream in the Hiwasa River generally agreed In the Hiwasa River System, N . themselves in brackish water area with low Body sizes of P. compressa and C. with the classification system proposed denticulata was typically found in the upper salt concentration than the juveniles of the leucosticta increased with increasing by Shokita (1979) for the Ryukyus, but it reaches of the large tributaries, where the other rivers in the same system, thanks to this upstream distance from the sea (Fig. 6), a was not true for C. typus (Fig. 3b). In the streams flow calmly (Fig. 3b, Table 1). This wetland. commonly reported trend in amphidromous Ryukyu Archipelago, C. typus was found distribution pattern of the shrimp agrees with Based on these observations, range of species (e.g. Shokita, 1979; Schneider SHRIMP DISTRIBUTION IN SOUTHeRN CeNTRAL JAPAN 41 40 et al. 41 physical environment in their upstreamM. Saito what Suzuki et al. (1993) and Sato et al. N. denticulata is thought to be determined & Lyons, 1993). This distribution trend migration route. even though all three (1994) reported for Kagoshima Prefecture, in by relative ease for them to resist high flow indicates that the two species are growing species prefer quieter waters, there exists that they are absent in the lower reaches. Sato condition in that habitat, but not by the as they migrate upstream. It was also the noticeable difference in preferable daytime et al. (1994) explained such pattern in the distance from the river mouth or elevation. case for catadromous E. japonica, which habitat between the two atyid and the Manose River by effect of non–point source In case of turbulent medium scale rivers agrees with previous findings by Kobayashi palaemonid species. Caridina serratirostris pesticide pollution from nearby rice paddies like the Hiwasa River System, the upper & Matsuura (1991). The fact that large C. prefer leaf litters and riverbank vegetation, in the lower reaches. However, it is not the reaches with relatively moderate gradient leucosticta was also collected in brackish and often found hiding under boulders case for the Hiwasa River System, since and low discharge are suggested to be the water stations unlike P. compressa suggests (Hamano et al., 2008). Caridina leucosticta closely related amphidromous atyid shrimps best habitat of the shrimp. In fact, range of that some individuals cease upstream is also abundant in riverbank vegetation are found to inhabit there at the highest N. denticulata in the Kitagawachidani River migration and become regular inhabitant (Hamano et al., 2008). On the other hand, densities within the river system. Instead, agrees with that of Rhinogobius flumineus there, as previously reported by Yamahira et M. formosense do not necessarily rely on relative ease for juveniles to stay there under (Saito, unpublished data), a land–locked al. (2007). riverbank vegetation; while juveniles prefer high flow condition seems to be the solution. goby vulnerable to high concentration salt Caridina serratirostris showed different shallow area and vegetation, adults usually Unlike all the other atyids found in the water that has amphidromous congeners. distribution pattern, with larger individuals hide under boulders and occasionally in Hiwasa River, N. denticulata is a non– and ovigerous females aggregated in Habitat use of Macrobrachium prawns vegetation especially during the summer diadromous species that lays large eggs brackish water area, lower end of its range. Distribution patterns of Macrobrachium (Saito, unpublished data). in small number (Hayashi, 2007). They This trend may insist on presence of active prawns in the Hiwasa River System agreed Besides the lower reaches, moderately hatch as post larvae that closely resemble downstream migration by females. However, with previous reports (e.g. Shokita, 1979; flowing area with vegetation occurs in juvenile shrimp in shape (Mizue & Iwamoto, concerning poor upstream migration or Suzuki et al., 1993) in that the range of M. the upper reaches of the Kitagawchidani 1961). Lower reaches seem to be potential flow resisting capability of this species japonicum extends somewhat upper reach and Yamagawachidani Rivers, but habitat for N. denticulata under regular (e.g. Hamano et al. 2008), bulkier females of M. formosense, but with considerable Caridina shrimps are rare in the latter flow condition because of moderate current may simply be less tolerant to high flow overlap. In spite of the overlap, the two area. This phenomenon is not because of flow and abundant emergent or submerged condition than males. Detailed and frequent species seem to be facing little interspecific C. leucosticta’s lack of will to undertake vegetation, structure that the species show survey would be needed to confirm where competition there. Results of CCA have upstream migration. In September and positive stereotaxis to (Niwa & Yokoyama, in river this species mates and if difference identified difference in habitat utilization October, C. leucosticta accounted for nearly 1993). However, this river fluctuates greatly in frequency of ovigerous female among between the two species at macro habitat, half of the roughly three hundred specimens in its flow condition, often inundating reaches is a constantly seen phenomenon in other word, reach scale; while the former collected in H03, but they were seldom entire stretch of riverbank vegetation after over the mating season, insisting on active prefer coarse boulder bed, the latter shows collected in H04 (Saito et al., unpublished heavy rainfall. Concerning that Neocaridina downstream migration by ovigerous females weak association with vegetation. Ohno et data), suggesting that their upstream shrimps are vulnerable to high concentration (e.g. Ohtomi & Nakabayashi, 1999; Bauer & al. (1977) noted that in the Shimanto River, migration is blocked by some physical salt water (e.g. Shokita, 1976), small Delahoussaye, 2008). south western Japan, M. japonicum prefer barrier between these two stations. Nakata juveniles of N. denticulata seem to have little In contrast to P. compressa, females more swiftly flowing area compared to M. et al. (2010) reported that C. leucosticta chance of regaining its position in the lower of M. japonicum were larger in the lower formosense in the daytime, when looked at occurs in high density in the middle reaches reaches of the main stream, once struck with end of their range, with proportion of microhabitat (specific environment within a of Toyokawa River, Aichi Prefecture, central a flooding event. ovigerous individuals being higher there reach) scale. Since coarse boulder bed and Japan, which is roughly 20 km upstream of Okugata River was an exception to such (Fig. 5). Such pattern of distribution in dense riverbank vegetation are indicative the river mouth. This result suggests that trend. There, N. denticulata was abundant at amphidromous palaemonids insists on environments for swift and moderatel flow C. leucosticta is capable of migrating much the station located in proximity to the sea, presence of downstream migration for larval conditions, the present study and Ohno et al. longer distance upstream than what has been less than 3 km from the river mouth (Fig, release (e.g. Ohtomi & Nakabayashi, 1999; (1977) are said to be in agreement, although observed in the present study, if the gradient 3b, Table 1). This is presumably because Bauer & Delahoussaye, 2008). The authors different in its scale. These results suggest is gradual and vegetation continuously cover of the tributary’s moderate flow and low are currently preparing another paper on that the two amphidromous Macrobrachium river bank. Thus, gradient and continuity discharge owing to its short channel length. this topic based on year–round sampling to prawns moderately segregate their habitat of riverbank vegetation in the migration Downstream of O01 is a shallow wetland discuss presence and details of such life– at both of micro and macro scales in the route, rather than sole presence of isolated with dense vegetation cover of emergent history adaptation in this species. similar way, enabling them to coexist in their preferable habitat (riverbank vegetation), are plants. In case of flooding event, washed considerably overlapping range. Inter–regional difference in distribution suggested to be the determinant factors for C. away shrimps inhabiting the Okugata River Distribution patterns of the shrimps leucosticta’s upper limit of distribution. are thought to have higher chance of keeping Size distribution along the stream in the Hiwasa River generally agreed In the Hiwasa River System, N . themselves in brackish water area with low Body sizes of P. compressa and C. with the classification system proposed denticulata was typically found in the upper salt concentration than the juveniles of the leucosticta increased with increasing by Shokita (1979) for the Ryukyus, but it reaches of the large tributaries, where the other rivers in the same system, thanks to this upstream distance from the sea (Fig. 6), a was not true for C. typus (Fig. 3b). In the streams flow calmly (Fig. 3b, Table 1). This wetland. commonly reported trend in amphidromous Ryukyu Archipelago, C. typus was found distribution pattern of the shrimp agrees with Based on these observations, range of species (e.g. Shokita, 1979; Schneider SHRIMP DISTRIBUTION IN SOUTHeRN CeNTRAL JAPAN 43 42 42 et al. continuously from the lower reaches toM. the Saito pattern in the Japanese Archipelago, as water temperature is probably constraining reach vegetation dependents: found in upper reaches, irrespective of the sizes of one of the authors (MS) has found that C. over wintering of C. typus in possible upper– moderately flowing area of the lower reaches rivers (Shokita, 1979). This species has typus inhabits at high density in the lower reach habitat of medium scale rivers. and may invade middle reaches if gradient robustly built carapace and legs suitable to middle reaches in a high gradient stream is not steep and there exists continuous for enduring fast flow (Kamita, 1970) that in eastern Wakayama Prefecture, southern Classification of distribution pattern riverbank vegetation along the migration Shokita (1979) classified this species to central Japan, alongside with C. multidentata Distribution patterns of freshwater route. 2. Lower–middle reach shelter entire–reaches group capable of inhabiting and P. compressa (MS personal observation). decapod crustaceans have been classified in generalists: found in moderately flowing area nearly entire stretch of a stream, alongside This stream has multiple cascades and no the context of longitudinal distribution, which and are capable of using both coarse substrate with such species as M. japonicum. riverbank vegetation along its steepest is based on topographic profile of rivers and and riverbank vegetation as their shelters. On the contrary, in the Japanese section located below middle reach habitat, migration capability of each species (Shokita, 3. Lower–middle reach boulder dependents: Archipelago, distribution patterns of C. typus indicating that C. typus do not necessarily 1979; Suzuki & Sato, 1994; Usami et al., found in rapids and runs, and mainly use differ between small and medium scale rivers. require vegetation to reach headwater 2008). This system effectively explains boulders for their shelter. They may be found In the medium–scaled Hiwasa River System, habitat. Therefore, C. typus is suggested to be general structure and shift in distribution in in upper reaches in small rivers and streams. distribution of C. typus was restricted to the restricted to the lower reaches in the Japanese relation to presence of migration barriers 4. Middle–upper reach boulder dependents: freshwater area of lower reach , and results of Archipelago because of factors other than such as waterfalls, but additional information also found in rapids and rely on boulders CCA indicated that they are associated with migration ability or absence of riverbank is needed when trying to restore habitat of but differs from the previous group in that riverbank vegetation (Figs. 5, 10). Referring vegetation along its migration route. each species. The present study has identified they are capable of invading headwaters to results of Soomro et al. (2011) on the Medium scale rivers on the Japanese that riverbed and riverbank environment, both in small and medium scale rivers. Kikaijima Island, northern Ryukyus, and Archipelago differ from those of the Ryukyu adding on to the conventional longitudinal 5. Upper reach amphibious species: found Shokita (1979), C. typus grow to 12–30 mm Archipelago in wide spread presence of other factors, explain distribution of freshwater in the upper reaches of both moderately and orbital total length (OTL) by July of the year atyids that prefer quiet waters in middle to decapods and importance of coarse boulder rapidly flowing waters and are capable of following settlement and the majority of the upper reaches and low water temperature bed and riverbank vegetation as shrimp utilizing both aquatic and terrestrial habitats. recent recruits are smaller than 12 mm OTL in the winter time. Of the two, former is habitat. Moreover, the present study has 6. Moderate flow vegetation dependents: at that point. Since C. typus has short rostrum probably not a major limiting factor since indicated that the range of non–diadromous found in moderately flowing area in rivers less than 10% of its total length, we assumed C. typus was absent in middle and upper N. denticulata is regulated by distribution where risk of being washed down to the sea that the measurement data in the present reaches of the Hiwasa River despite absence of lentic areas within a river, not necessarily following heavy rain fall is low. They rely on study and Soomro et al. (2011) and Shokita of N. denticulata and scarcity of P. paucidens by the longitudinal factors. Incorporating vegetation and are also found in lentic waters (1979) are comparable. The population of C. (Fig. 3). Similar trend is reported for the these results with life history traits of each such as ponds and lakes. typus collected in the present study (Fig. 7) is Ibii River in the Miyazaki Prefecture by species, we propose a new classification for This classification is provided in hope thought to consist mainly of individuals that Watanabe & Kano (2009), making the latter freshwater decapod distribution in small of being used for general understanding have over–wintered and sexually matured. seem more convincing hypothesis. C. typus to medium scale rivers of the Japanese of habitat requirement of the targeted Thus, short in–river range of this species is a Pan–Pacific species distributed widely in Archipelago that are under influence of the species when trying to conserve or restore is expected to be in relation with riverine Indo–Pacific, and the Japanese Archipelago warm Kuroshio Current (Table 5). Criteria their habitat. This classification named environment, not because recent recruits is located at the northern limit of its range for each category are as follows. 1. Lower “environment dependent classification” were collected in the stations close to the sea. (Hayashi, 2007). Two amphidromous atyids, Suzuki et al. (1993) and Suzuki & P. compressa and C. multidentata commonly Sato (1994) reported similar distribution populate middle and upper reaches in rivers pattern as the present study for Kagoshima on the Japanese Archipelago pouring to the Table 5. Possible classification of distribution patterns for freshwater decapod crustaceans in small to medium Prefecture, southwestern Japan. Watanabe & Kuroshio affected Pacific. Of the two, P. scale rivers of the Japanese Archipelago influenced by the Kuroshio Current Kano (2009) reported that in the Ibii River, compressa is an endemic species to Japan Group Species Lentic/Lotic Shelter† Miyazaki Prefecture, C. typus mainly occurs mainly found along shore of the Kuroshio Lower reach vegetation dependents Caridina leucostica Lentic V in the lower reaches of freshwater area with Current (Shokita, 1979; Hayashi, 2007) with Caridina serratirostris Lentic V/L/B an exception of one individual found in one its mating season starting in March (Hamano Caridina typus Lentic V/B upper reach sampling station, even though the et al., 2008), when most other amphidromous Lower–middle reach shelter generalists Macrobrachium formosense Lentic V/B text concludes that C. typus showed similar shrimps are still inactive. Caridina Lower–middle reach boulder dependents Macrobrachium japonicum Lotic B pattern of distribution as Shokita (1979). multidentata is another pan–Pacific species Paratya compressa Lentic V/B Usami et al. (2008) reported contrasting but is commonly found in upper reaches of Eriocheir japonica Lentic/Lotic B result for Izu Peninsula and Hachijo–jima, the Japanese Archipelago (e.g. Watanabe & Middle–upper reach boulder dependents Caridina multidentata Lotic B Japan, that C. typus inhabits entire stretch of Kano, 2009), where water temperature falls Upper reach amphibious species Geothelphusa dehaani* Lentic/Lotic B high gradient streams. The results of Usami below 5°C in winter time. Thus, both species Lentic water vegetation dependents Neocaridina denticulata* Lentic V et al. (2008) are thought to be depicting are thought to have higher tolerance to low *: Non-diadromous species another aspect of the species’ distribution water temperature. Weaker tolerance to low †: V, vegetation; L, leaf litter; B, boulder. Optimum shelter shown in bold font SHRIMP DISTRIBUTION IN SOUTHeRN CeNTRAL JAPAN 43 42 et al. 43 continuously from the lower reaches toM. the Saito pattern in the Japanese Archipelago, as water temperature is probably constraining reach vegetation dependents: found in upper reaches, irrespective of the sizes of one of the authors (MS) has found that C. over wintering of C. typus in possible upper– moderately flowing area of the lower reaches rivers (Shokita, 1979). This species has typus inhabits at high density in the lower reach habitat of medium scale rivers. and may invade middle reaches if gradient robustly built carapace and legs suitable to middle reaches in a high gradient stream is not steep and there exists continuous for enduring fast flow (Kamita, 1970) that in eastern Wakayama Prefecture, southern Classification of distribution pattern riverbank vegetation along the migration Shokita (1979) classified this species to central Japan, alongside with C. multidentata Distribution patterns of freshwater route. 2. Lower–middle reach shelter entire–reaches group capable of inhabiting and P. compressa (MS personal observation). decapod crustaceans have been classified in generalists: found in moderately flowing area nearly entire stretch of a stream, alongside This stream has multiple cascades and no the context of longitudinal distribution, which and are capable of using both coarse substrate with such species as M. japonicum. riverbank vegetation along its steepest is based on topographic profile of rivers and and riverbank vegetation as their shelters. On the contrary, in the Japanese section located below middle reach habitat, migration capability of each species (Shokita, 3. Lower–middle reach boulder dependents: Archipelago, distribution patterns of C. typus indicating that C. typus do not necessarily 1979; Suzuki & Sato, 1994; Usami et al., found in rapids and runs, and mainly use differ between small and medium scale rivers. require vegetation to reach headwater 2008). This system effectively explains boulders for their shelter. They may be found In the medium–scaled Hiwasa River System, habitat. Therefore, C. typus is suggested to be general structure and shift in distribution in in upper reaches in small rivers and streams. distribution of C. typus was restricted to the restricted to the lower reaches in the Japanese relation to presence of migration barriers 4. Middle–upper reach boulder dependents: freshwater area of lower reach , and results of Archipelago because of factors other than such as waterfalls, but additional information also found in rapids and rely on boulders CCA indicated that they are associated with migration ability or absence of riverbank is needed when trying to restore habitat of but differs from the previous group in that riverbank vegetation (Figs. 5, 10). Referring vegetation along its migration route. each species. The present study has identified they are capable of invading headwaters to results of Soomro et al. (2011) on the Medium scale rivers on the Japanese that riverbed and riverbank environment, both in small and medium scale rivers. Kikaijima Island, northern Ryukyus, and Archipelago differ from those of the Ryukyu adding on to the conventional longitudinal 5. Upper reach amphibious species: found Shokita (1979), C. typus grow to 12–30 mm Archipelago in wide spread presence of other factors, explain distribution of freshwater in the upper reaches of both moderately and orbital total length (OTL) by July of the year atyids that prefer quiet waters in middle to decapods and importance of coarse boulder rapidly flowing waters and are capable of following settlement and the majority of the upper reaches and low water temperature bed and riverbank vegetation as shrimp utilizing both aquatic and terrestrial habitats. recent recruits are smaller than 12 mm OTL in the winter time. Of the two, former is habitat. Moreover, the present study has 6. Moderate flow vegetation dependents: at that point. Since C. typus has short rostrum probably not a major limiting factor since indicated that the range of non–diadromous found in moderately flowing area in rivers less than 10% of its total length, we assumed C. typus was absent in middle and upper N. denticulata is regulated by distribution where risk of being washed down to the sea that the measurement data in the present reaches of the Hiwasa River despite absence of lentic areas within a river, not necessarily following heavy rain fall is low. They rely on study and Soomro et al. (2011) and Shokita of N. denticulata and scarcity of P. paucidens by the longitudinal factors. Incorporating vegetation and are also found in lentic waters (1979) are comparable. The population of C. (Fig. 3). Similar trend is reported for the these results with life history traits of each such as ponds and lakes. typus collected in the present study (Fig. 7) is Ibii River in the Miyazaki Prefecture by species, we propose a new classification for This classification is provided in hope thought to consist mainly of individuals that Watanabe & Kano (2009), making the latter freshwater decapod distribution in small of being used for general understanding have over–wintered and sexually matured. seem more convincing hypothesis. C. typus to medium scale rivers of the Japanese of habitat requirement of the targeted Thus, short in–river range of this species is a Pan–Pacific species distributed widely in Archipelago that are under influence of the species when trying to conserve or restore is expected to be in relation with riverine Indo–Pacific, and the Japanese Archipelago warm Kuroshio Current (Table 5). Criteria their habitat. This classification named environment, not because recent recruits is located at the northern limit of its range for each category are as follows. 1. Lower “environment dependent classification” were collected in the stations close to the sea. (Hayashi, 2007). Two amphidromous atyids, Suzuki et al. (1993) and Suzuki & P. compressa and C. multidentata commonly Sato (1994) reported similar distribution populate middle and upper reaches in rivers pattern as the present study for Kagoshima on the Japanese Archipelago pouring to the Table 5. Possible classification of distribution patterns for freshwater decapod crustaceans in small to medium Prefecture, southwestern Japan. Watanabe & Kuroshio affected Pacific. Of the two, P. scale rivers of the Japanese Archipelago influenced by the Kuroshio Current Kano (2009) reported that in the Ibii River, compressa is an endemic species to Japan Group Species Lentic/Lotic Shelter† Miyazaki Prefecture, C. typus mainly occurs mainly found along shore of the Kuroshio Lower reach vegetation dependents Caridina leucostica Lentic V in the lower reaches of freshwater area with Current (Shokita, 1979; Hayashi, 2007) with Caridina serratirostris Lentic V/L/B an exception of one individual found in one its mating season starting in March (Hamano Caridina typus Lentic V/B upper reach sampling station, even though the et al., 2008), when most other amphidromous Lower–middle reach shelter generalists Macrobrachium formosense Lentic V/B text concludes that C. typus showed similar shrimps are still inactive. Caridina Lower–middle reach boulder dependents Macrobrachium japonicum Lotic B pattern of distribution as Shokita (1979). multidentata is another pan–Pacific species Paratya compressa Lentic V/B Usami et al. (2008) reported contrasting but is commonly found in upper reaches of Eriocheir japonica Lentic/Lotic B result for Izu Peninsula and Hachijo–jima, the Japanese Archipelago (e.g. Watanabe & Middle–upper reach boulder dependents Caridina multidentata Lotic B Japan, that C. typus inhabits entire stretch of Kano, 2009), where water temperature falls Upper reach amphibious species Geothelphusa dehaani* Lentic/Lotic B high gradient streams. The results of Usami below 5°C in winter time. Thus, both species Lentic water vegetation dependents Neocaridina denticulata* Lentic V et al. (2008) are thought to be depicting are thought to have higher tolerance to low *: Non-diadromous species another aspect of the species’ distribution water temperature. Weaker tolerance to low †: V, vegetation; L, leaf litter; B, boulder. Optimum shelter shown in bold font 44 44 et al. of freshwater decapod crustaceanM. Saito was partly supported by grant in aid from distribution has four major advantages the Foundation of River & Watershed over the traditional classification based on environmental Management to TH. longitudinal distribution. First, it describes how range of each species change in relation to size of the river. Second, it classifies Literature cited groups with riverbed and riverbank usage, Bain, M. B., Finn, J. T., & Booke, H. e., 1985. enabling rough prediction for future change Quantifying stream substrate for habitat analysis studies. North American Journal of Fisheries in species composition and distribution Management, 5: 499–500. pattern following environment alterations. Baumgartner, L. J., 2007. Diet and feeding habits of Next, it divides species found in upper predatory fishes upstream and downstream of reaches into separate groups based on their a low–level weir. Journal of Fish Biology, 70: life–history traits. This modification made 879–894. it clear connection with what environment, Cummins, K. W., 1962. An evaluation of some either land or the sea, is important in techniques for the collection and analysis of preserving population of that species. Finally, benthic samples with special emphasis on lotic waters. American Midland Naturalist, 67: 477– it sets non–diadromous N. denticulata apart 504. from longitudinal factors and made it an Bauer, R. T., & Delahoussaye, J., 2008. Life history independent group. This modification made it migrations of the amphidromous river shrimp possible to explain inconsistency in the range Macrobrachium ohione from a continental large of this species from river to river, by focusing river system. Journal of Crustacean Biology, on distribution of moderately flowing areas 28(4): 622–632. within that river. environmental Management Bureau, Ministry of environment, 2011. Results of the FY 2010 In the Hiwasa River System, P. paucidens Water Quality Survey of Public Water Areas. was too rare to evaluate its within river Ministry of environment, Tokyo, 119 pp. (In distribution pattern or macro habitat Japanese) preferences. P. paucidens has been reported Fossati, O., Mosseron, M., & Keith, P., 2002. to prefer moderately flowing area and is Distribution and habitat utilization in two abundant in larger river systems (Hamano atyid shrimps (Crustacea: Decapoda) in rivers et al., 2008). As P. paucidens sometimes do of Nuku–Hiva Island (French Polynesia). not coexist with N. denticulata (Suzuki et al., Hydrobiologia, 472: 197–206. Greathouse, e. A., Pringle, C. M., McDowell, 1993), understanding basic criteria for their W. H., & Holmquist, J. G., 2006. Indirect distribution would be profitable for shrimp effects of dams: consequences of migratory conservation. Future studies focused on non– consumer extirpation in Puerto Rico. ecological diadromous species and species that prefer Applications, 16: 339–352. quiet waters, especially in low gradient river Hamano, T. & Hayashi, K., 1992. ecology of an systems along the coast of the Pacific Ocean, atyid shrimp Caridina japonica (De Man, 1892) would further improve versatility of the migrating to upstream habitats in the Shiwagi rivulet, Tokushima Prefecture. Researches on classification system presented here. Crustacea, 21: 1–13. (In Japanese with english abstract) Acknowledgements Hamano, T., Ito, N., & Yamamoto, K., 2008. Mizube–no–kowaza (enlarged and revised Authors express sincere thanks to Drs. edition). Civil engineering and Construction Shogo Hirai and Koichi Tanaka (University Division, Yamaguchi Prefecture, Yamaguchi, 272 of Tokushima) for their kind assistance in pp. (In Japanese) using GIS software. Thanks go to members Hamano, T., Kamada, M., & Tanabe, T., 2000. of the Laboratory of Regional Bio–Resource Distributions of freshwater decapod crustaceans in Tokushima Prefecture, Japan, with notes on Management (University of Tokushima) for conservation methods for local populations. their field assistance. Constructive comments Bulletin of the Tokushima Prefectural Museum, from two anonymous reviewers and Dr. 10: 1–47. (In Japanese with english abstract) Hiroshi Suzuki (Kagoshima University) Hamano, T., Yoshimi, K., Hayashi, K., Kakimoto, H., helped improve the manuscript. This work and Shokita, S., 1995. experiments on fishways SHRIMP DISTRIBUTION IN SOUTHeRN CeNTRAL JAPAN 45 45

for freshwater amphidromous shrimps. Nippon March, J. G., & Pringle, C. M., 2002. effects of Suisan Gakkaishi, 61: 171–178. (In Japanese freshwater shrimp assemblages on benthic with english abstract) communities along an altitudinal gradient of a Hayashi, K., 1999. Prawns, shrimps and lobsters tropical island stream. Freshwater Biology, 47: from Japan (109). Family Palaemonidae, 377–390. subfamily Palaemoninae — genera Leander McCune, B., & Grace, J. B., 2002. Analysis of and Palaemon 1. Aquabiology, 21: 522–526. (In ecological communities. mjm software designs, Japanese) Gleneden Beach, 300 pp. Hayashi, K., 2000a. Prawns, shrimps and lobsters McDowall, R. M., 2007. On amphidromy, a distinct from Japan (110). Family Palaemonidae, form of diadromy in aquatic organisms. Fish and subfamily Palaemoninae — genus Palaemon 2. Fisheries, 8: 1–13. Aquabiology, 22: 57–62. (In Japanese) Minchin, P. R., 1987. An evaluation of the relative Hayashi, K., 2000b. Prawns, Shrimps and lobsters robustness of techniques for ecological from Japan (112). Family Palaemonidae, ordination. Vegetatio, 69: 89–107. subfamily Palaemoninae — genus Miya, Y., & Hamano, T., 1988. The influence of a Macrobrachium 1. Aquabiology, 22: 240–245. dam having no fishway on the distribution of (In Japanese) decapod crustaceans in the Yukinoura River, Hayashi, K., 2000c. Prawns, shrimps and lobsters Nagasaki, Japan. Nippon Suisan Gakkaishi, 54: from Japan (113). Family Palaemonidae, 429–435. (In Japanese with english abstract) subfamily Palaemoninae — genus Miyake, S., 1983. Japanese crustacean decapods and Macrobrachium 2. Aquabiology, 22: 360–363. stomatopods in color vol. II Brachyura (crabs). (In Japanese) Hoikusha, Osaka, 277 pp. (In Japanese) Hayashi, K., 2000d. Prawns, shrimps and lobsters Mizue, K., & Iwamoto, Y., 1961. On the larval from Japan (114). Family Palaemonidae, development and growth of Neocaridina subfamily Palaemoninae — genus denticulata de Haan. Bulletin of the Faculty of Macrobrachium 3. Aquabiology, 22: 468–472. Fisheries, Nagasaki University, 10: 15–24. (In Japanese) Nakata, K., Amano, K., Denda, M., Miwa, J., Hayashi, K., 2007. Prawns, shrimps and lobsters & Hamano, T., 2010. effects of habitat from Japan II — Caridea I. Seibutsu–kenkyusha, fragmentation on the amphidromous freshwater Tokyo, 306 pp. (In Japanese) shrimp, Caridina leucosticta (Decapoda, Iwata, T., Inoue, M., Nakano, S., Miyasaka, H., Doi, Atyidae) in a rice paddy drainage channel. A., & Covich, A. P., 2003. Shrimp abundance Crustaceana, 83: 1125–1133. and habitat relationships in tropical rain–forest Nakata, K., Hamano, T., Amano, K., Miwa, J., streams, Sarawak, Borneo. Journal of Tropical 2011. ecology and conservation of freshwater ecology, 19: 387–395. shrimps and prawns. Shrimps, Prawns, Crabs, Kamita, T., 1970. Studies on the shrimps, prawns, and Crayfishes—conservation and biology and crawfishes of Japan. Sonoyama Shoten, of freshwater crustaceans—, pp. 148–166, Matsue, 213 pp. (In Japanese with english Seibutsu–kenkyusha, Tokyo. (In Japanese) abstract) Niwa, N., & Yokoyama, T., 1993. Fauna and Katoh, K., & Takeuchi, K., 1991. ecological distribution of decapod crustaceans, with community analysis for the establishment of special reference to Neocaridina denticulata, river environmental management planning. inhabiting the Yumesaki River System, Japan. Journal of the Japanese Institute of Landscape Suisanzoshoku, 41: 519–528. (In Japanese with Architecture, 54: 281–286. (In Japanese with english abstract) english abstract) Ohno, A., Ogasawara, Y., & Yasuda, F., 1977. Kobayashi, S. & Matsuura, S., 1991. Longitudinal Distribution and habitat of the long–armed distribution of the Japanese mitten crab in the freshwater prawns of the genus Macrobrachium Kaminokawa River, Kagoshima. Nippon Suisan in the Shimanto River, Shikoku. Japanese Gakkaishi, 57: 1029–1034 (In Japanese with Journal of ecology, 27: 23–32. (In Japanese with english abstract) english abstract) Kobayashi, S., 2009. Dietary preferences of the Ohtomi, J., & Nakabayashi, N., 1999. Reproductive Japanese mitten crab Eriocheir japonica in a biology of the crane river prawn Macrobrachium river and adjacent seacoast in north Kyushu, formosense Bate in the Yabusa River, southern Japan. Plankton & Benthos Research, 4: 77–87. Kyushu, Japan. Nippon Suisan Gakkaishi, 65: Maeda, K., & Tachihara, K., 2004. Instream 473–479. (In Japanese with english abstract) distributions and feeding habits of two species Palmer, M. W., 1993. Putting things in even of sleeper, eleotris acanthopoma and e. fusca in better order: the advantages of canonical the Teima River, Okinawa Island. Ichthyological correspondence analysis. ecology, 74: 2215– Research, 51: 233–240. 2230. CRUSTACEAN RESEARCH, NO. 41: 47–58, 2012 46 46 et al.

Richards, C., Host, G. e., & Arthur, J. W., M.1993. Saito 67: 1167–1179. Identification of predominant environmental ter Braak, C. J. F., & Verdonschot, P. F. M., 1995. Agonistic and mating behavior in relation to chela features factors structuring stream macroinvertebrate Canonical correspondence analysis and related in Hemigrapsus takanoi and H. sinensis (Brachyura, communities within a large agricultural multivariate methods in aquatic ecology. Aquatic catchment. Freshwater Biology, 29: 285–294. Sciences, 57: 255–289. Varunidae) Sato, M., Arai, K., & Ohara, Y., 1994. Distribution Usami, Y., Yokota, K., & Watanabe, S., 2008. of freshwater shrimps, a prawn and a crayfish, Longitudinal distributions of freshwater shrimps and life history of Neocaridina denticulata and prawns (Crustacea, Decapoda, Caridea, denticulata in the System of Manose Rivers in Atyidae and Palaemonidae) in Kanto district. Kagoshima Prefecture, southern Japan. Bulletin Bulletin of the Biogeographical Society of Japan, Aya Miyajima, Yasuo Fukui and Keiji Wada of the Faculty of Science, Kagoshima University, 63: 51–62. (In Japanese with english abstract) 27: 245–262. (In Japanese with english abstract) Watanabe, J., & Kano, Y., 2009. Occurrence and Schneider, D. W. & Lyons, J., 1993. Dynamics of longitudinal distribution of shrimps in Kaeda Abstract.—Relative growth of chelae and in mating, should have larger chelae in upstream migration in two species of tropical and Ibii Rivers, Miyazaki, Japan. Bulletin of the the area of setal patches was investigated for males than in females. Indeed, in most crabs freshwater snails. Journal of North American Faculty of Agriculture, University of Miyazaki, Hemigrapsus takanoi, in which only males have chelae of males grow larger than those Benthological Society, 12: 3–16. 55: 25–35. (In Japanese with english abstract) setal patches on chelae, and for H. sinensis, in of females (Warner, 1970; Kobayashi & Shokita, S., 1976. early life–history of the land– Yamahira, K., Inoue, A., Oishi, S., & Ideguchi, which both sexes have setal patches. Chelae locked atyid shrimp, Caridina denticulata Matsuura, 1993). Conversely, in species K., 2007. Upstream and downstream variation and setal patches increased with body size in ishigakiensis Fujino et Shokita, from the Ryukyu in demography of the amphidromous shrimp which intrasexual agonistic interaction is both species. In H. takanoi, chela size and size Islands. Researches on Crustacea, 7: 1–10. Caridina leucosticta. Japanese Journal of rare or fighting is not biased towards either Shokita, S., 1979. The distribution and speciation Benthology, 62: 9–16. (In Japanese with english increment relative to body size was larger in sex, sexual dimorphism in chela is predicted of the inland water shrimps and prawns from abstract) males than in females. In H. sinensis, chela size to be minimal. Warner (1970) indicated the Ryukyu Islands—II. Bulletin of Science and relative to body size was larger in males than that in Aratus pisoni which have marked engineering Division, University of the Ryukyus, in females, but size increment was not different sexual dimorphism of chela, ritualized 28: 193–278. (In Japanese with english abstract) Addresses: (MS) Graduate School of between the sexes. Sexual dimorphism of chelae agonistic behavior occurred only in males, Soomro, A. N., Suzuki, H., Kitazaki, M., & is more prominent in H. takanoi than in H. Integrated Arts and Sciences, University but for Goniopsis cruentata in which sexual Yamamoto, T., 2011 Reproductive aspects of sinensis. Laboratory observations of intrasexual two atyid shrimp Caridina sakishimensis and of Tokushima, 1–1 Minami–johsanjima, dimorphism of chela is not obvious, ritualized Tokushima, Tokushima Prefecture 770–8502, agonistic interactions revealed that the interaction Caridina typus in head water streams of Kikai– occurred more frequently in H. takanoi than in agonistic behavior occurred similarly in both jima Island, Japan. Journal of Crustacean Japan, (TY & TH) Institute of Socio Arts H. sinensis without any sexual difference in either sexes. Similarly, in two species of porcellanid Biology, 31: 41–49. and Sciences, University of Tokushima, 1–1 species. In agonistic interactions by H. takanoi, crabs, Petrolisthes mitra and P. spinifrons, Suzuki, H., & Sato, M., 1994. Kagoshima nature Minami–johsanjima, Tokushima, Tokushima male–male competition for sexual partners guide—freshwater shrimps, prawns and crabs. Prefecture 770–8502, Japan, (KN) Graduate males mostly used chelae, while females employed their walking legs. By contrast, both sexes of is more frequent in Petrolisthes mitra, which Nishinohon–shimbunsha, Fukuoka, 137 pp. (In School of environmental and Life Science, Japanese) H. sinensis used chelae more frequently than has more marked sexual dimorphism in chela Suzuki, H., Tanigawa, N., Nagatomo, T., & Tsuda, Okayama University, 3–1–1 Tsushima–naka, walking legs in agonistic interactions. In mating than in P. spinifrons (Baeza & Asorely, 2012). e., 1993. Distribution of freshwater caridean North Ward, Okayama, Okayama Prefecture behavior, both species made a copulative posture However, studies showing the relationship shrimps and prawns (Atyidae and Palaemonidae) 700–8530, Japan. without courtship behavior. Males of H. takanoi between sexual dimorphism of chelae and from southern Kyushu and adjacent islands, e–mail: (MS) [email protected], handled females with chelae during mating intrasexual competition are limited. Kagoshima Prefecture, Japan. Crustacean (KN) [email protected]–u.ac.jp behavior, whereas in H. sinensis, chela handling Hemigrapsus takanoi is distributed in Research, 22: 55–64. was infrequent. All the findings suggest the extent Japan (Hokkaido to Kagoshima, Okinawa) ter Braak, C. J. F., 1986. Canonical correspondence analysis: a new eigenvector technique for Received: 7 September 2012. of sexual dimorphism of chela is correlated with and the adjacent waters of Sakhalin Island, multivariate direct gradient analysis. ecology, Accepted: 4 December 2012. sexual difference of chela use in social behavior. Taiwan, Korea, and China. It is usually found under boulders in intertidal areas of inner bays and estuaries under brackish to marine Introduction water condition (Asakura & Watanabe, Chelae of brachyuran crabs are employed 2005). Male chelae are larger than those not only in feeding, but also intra / inter of females (Asakura & Watanabe, 2005; specific agonistic interaction and mating. Mingkid et al., 2006), and only males have Males with larger chelae have an advantage setal patches on the outside and inside of the in agonistic interaction as well as mate chela propodus (Fig. 1) (Sakai, 1976). acquisition (Lee & Seed, 1992; McLain & Hemigrapsus sinensis inhabits oyster and Pratt, 2007; Sneddon et al., 1997; Stein, boulder reefs in the middle of the intertidal 1975). Thus, it is reasonable to expect that zone down to the subtidal zone of mud flats species in which agonistic interaction is under brackish water condition (Japanese intense and males guard or handle females Association of Benthology, 2012). It is