Abstract Understanding the mechanism by which non‐native fish species integrate into native communities is crucial for evaluating the possibility of their establishment success. The genus Pangasianodon, comprising Pangasianodon gigas and Pangasianodon hypophthalmus, has been introduced into reservoirs, which are non‐native habitats, for fishery stock enhancement. P. gigas and P. hypophthalmus often successfully establish and co‐occur in several Thai reservoirs, but there is little information on differences in food resource use between the two species. To investigate the trophic niche width of P. gigas and P. hypophthalmus in a Thai reservoir, we conducted stable carbon and nitrogen ratio (δ¹³C and δ¹⁵N) analyses. We examined the degree of individual specialization in both species using the δ¹³C and δ¹⁵N values of muscle and liver tissues, which provides long‐ and short‐term diet information. The isotopic niches did not overlap between P. gigas and P. hypophthalmus. The δ¹⁵N value of P. gigas was significantly higher than that of P. hypophthalmus, whereas the δ¹³C value did not significantly differ between the two species. The isotopic niche sizes were larger in P. hypophthalmus than in P. gigas. Individual specialization was observed in P. hypophthalmus but not in P. gigas, indicating that intraspecific variation in food resource use was larger in P. hypophthalmus compared to P. gigas. These findings suggest that trophic niche partitioning was one of the factors facilitating the establishment success of P. gigas and P. hypophthalmus in a reservoir, but the establishment process may differ between the two species.

Abstract A simple method for measuring bioelectric signals of fish in seawater is expected for managing the health of farmed fish and clarifying the ecophysiology of natural fish. We previously proposed a simple and unique method for measuring bioelectric signals of fish by inserting only one special internal electrode (which can be isolated from seawater) into the fish’s body and by sinking an external electrode in seawater (for utilizing the conductivity of seawater). However, the proposed method could not obtain fish electrocardiograms (ECGs) with reliable R-waves in the same manner as the conventional method. In this study, we thus experimentally investigated whether the R-waves of ECGs could be observed by optimizing the insertion position of the internal electrode into the fish’s body. The results of the experiment show that for four species of fish (each slightly longer than 10 cm) with different body shapes, reliable R-waves could be observed by inserting the internal electrode near the heart. We also investigated the possibility of simultaneously measuring ECGs of multiple fish by the proposed method. The results of the investigation show that the fish ECGs with R-waves of three fish could be observed simultaneously even when one single common external electrode replaced multiple external electrodes. This result indicates the advantage of the proposed method in reducing the total number of bioelectrodes compared to the conventional method for ECG measurements of multiple fish.

Abstract Dietary information from aquatic organisms is instrumental in predicting biological interactions and understanding ecosystem functionality. In freshwater habitats, generalist fish species can access a diverse array of food sources from multiple food chains. These may include primary photosynthetic production and detritus derived from both oxic and anoxic decomposition. However, the exploitation of anoxic decomposition products by fish remains insufficiently explored. This study examines feeding habits of striped catfish (Pangasianodon hypophthalmus) at both adult and juvenile stages within a tropical reservoir, using stable carbon, nitrogen, and sulfur isotope ratios (δ¹³C, δ¹⁵N, and δ³⁴S, respectively) and fatty acid (FA) analyses. The adult catfish exhibited higher δ¹⁵N values compared to primary consumers that feed on primary photosynthetic producers, which suggests ingestion of food sources originating from primary photosynthetic production-based food chains. On the other hand, juvenile catfish demonstrated lower δ¹⁵N values than primary consumers, correlating with low δ³⁴S value and large proportions of bacterial FA but contained small proportions of polyunsaturated FA. This implies that juveniles utilize food sources from both anoxic decomposition and primary photosynthetic production-based food chains. Our results indicate that food chains based on anoxic decomposition can indeed contribute to the dietary sources of tropical fish species.

Abstract Satellite telemetry devices can record movement data of animals along with the environmental data. Such data are relayed remotely via satellite systems, but are constrained by the limited bandwidth availability. A satellite relay data logger (SRDL) that can abstract dive profiles and compress the data for transmission using a broken stick model (BSM) has been widely used in studies on dive behavior and physiology of marine animals. However, there is still uncertainty in the abstracted dive profiles. Here, we aimed to evaluate the certainty of abstracted dive profiles (via satellite communication) in terms of dive performance (dive depth, duration, and dive type) by comparing it with the actual dive data (from the retrieved tag) in a loggerhead turtle deployed with the SRDL throughout a 1.4-year foraging period. There was no significant difference in the maximum dive depth between the retrieved and satellite transmission data; however, there was a slight but significant difference in the dive duration. The dives from both datasets were classified into five types. Inconsistent dive classifications occurred in 1.7% of the data. There was no significant difference in the proportion of time spent diving between the retrieved and satellite transmission data for each type during the common recording period. In monthly scale comparisons, however, a significant difference was detected when the amount of data via satellite transmission was the smallest. Our results demonstrated that the dive data abstracted using BSM almost reconstructed the actual dive profiles with certainty in a loggerhead turtle, although slight inconsistencies were observed.

The Mekong giant catfish (MGC), Pangasianodon gigas, is one of the world's largest catfish species. Endemic to the Mekong River system, the MGC is critically endangered. Six MGC were transported from Thailand to the Gifu World Freshwater Aquarium (GWFA) in Japan in May 2004. The MGC have not been measured since they were introduced to the GWFA due to the challenges associated with their large size. Traditional methods, such as anesthesia and net-capture, could harm the fish, potentially reducing the population further. However, understanding the ecology of the species is essential to conservation efforts. Seasonal feeding rhythms and long-term fasting were previously observed in captive MGCs. To investigate the effect of long-term fasting on MGC growth, total length measurements are necessary. In this study, we applied a noncontact method to estimate the total length via image analysis. We shot a stereo-video of free-swimming MGC in the aquarium tank using two digital video cameras and analyzed the 3D images using the direct linear transformation method. We successfully estimated the total length of each MGC individual without contacting the fish. This accurate estimation method is versatile, simple, and useful in aquarium breeding and is also recommended from the viewpoint of animal welfare because it is a noninvasive method of measurement.

Fish form schools because of many possible reasons. However, the hydrodynamic mechanism whereby the energy efficiency of fish schools is improved still remains unclear. There are limited examples of fish models based on actual swimming movements using simulation, and the movements in existing models are simple. Therefore, in this study, we analyzed the swimming behavior of Biwa salmon (Oncorhynchus sp., a salmonid fish) using image analyses and formulated its swimming motion. Moreover, computational fluid dynamics analysis was carried out using the formulated swimming motion to determine the fluid force acting on the fish body model with real fish swimming motion. The swimming efficiency of the fish model under parallel swimming was obtained from the calculated surrounding fluid force and compared for different neighboring distances. The flow field around the fish model was also examined. The swimming efficiency of two fish models swimming parallelly was improved by approximately 10% when they were separated by a distance of 0.4L, where L is the total length of the model. In addition, the flow field behind the fish body was examined under both inphase and antiphase conditions and at inter-individual distances of 0.8L and 1.2L. The apparent flow speed in the distance range of 0.5-2.0L from the midpoint of the snouts of the two individuals was lower than the swimming speed. The pressure distribution on the fish model showed an elevated pressure at the caudal fin. Interestingly, we obtained an isopleth map similar to that of a caudal peduncle. To avoid a negative thrust, the aft part of the body must be thin, as shown in the isopleth map obtained in this study.

The Mekong giant catfish Pangasianodon gigas is one of the largest freshwater fish, measuring up to 3 m in total length. This study was designed to determine the feeding habits of P. gigas to better understand how the fish achieve their large body size. We compared the relationship between gut length (GL) and total length (TL) among related species in superfamily Bagroidea, order Siluriformes (Pangasianodon hypophthalmus and Hemibagrus nemurus) in the Kaeng Krachan reservoir, Thailand. The mean relative gut length (RGL = GL / TL) of P. gigas was 3.50, showing that they have relatively long guts, with values more similar to those of omnivorous P. hypophthalmus (RGL = 3.70) than to those of carnivorous H. nemurus (RGL = 0.92). In the allometric relationship (i.e., log(10) GL = log(10) a + b log(10) TL), the slope close to 1 for P. gigas (b = 1.07) has been widely observed in carnivores, while P. gigas has a greater intercept of the linear equation than P. hypophthalmus and H. nemurus, resulting in a similar GL of P. gigas to omnivorous P. hypophthalmus at approximately 35 cm in TL. Moreover, GL of P. gigas at 150 to 250 cm in TL showed great variations (RGL = 1.35-6.32). The variation in RGL for P. gigas seemed to result from a poor nutritional state. In conclusion, P. gigas is suggested to feed on indigestible materials such as plants, algae, and sediments, and potentially experience fasting in a reservoir.

メコンオオナマズ種苗の放流後の行動追跡のために，超音波発信機を装着した0歳魚15個体を，タイ国ケンカチャン湖に放流した。湖に設置した20台の受信機により，最長252日間のモニタリングに成功した。放流個体の多くは，約1か月間は湖の広い範囲を遊泳し，その後，中央部やダム近くを遊泳するようになった。2か月以上追跡できた6個体で昼夜どちらかのみ受信される期間があり，水平移動の日周性が確認された。全ての個体が発信機の電池寿命前に受信が途絶える，もしくは移動しなくなり，被食，混獲，発信機の脱落が考えられた。</p>

Biwa salmon Oncorhynchus masou subsp. were tagged with ultrasonic transmitters and released in Lake Biwa, Japan. The temporal and spatial distributions were investigated by using two types of ultrasonic telemetry system, active tracking and passive monitoring. Biwa salmon cruised throughout the north basin horizontally and were distributed from the surface to the bottom vertically in the lake. An individual monitored for over 1 year showed the diurnal patterns of vertical distribution and the seasonal patterns of horizontal distribution. The vertical distribution of the fish during daytime in the stratified period was bimodal, suggesting a feeding strategy targeting both fish near the thermocline and the amphipods near the bottom. During the night, however, the fish maintained a fixed depth range. The fish were distributed over a wider horizontal area in the mixed period than in the stratified period. Three individuals swam in shallower water and experienced higher water temperatures during the spawning season than before moving between offshore and coastal areas.

琵琶湖は日本最大の自然湖であり，多くの固有種が生息している。琵琶湖に生息する60種の魚類のうち12種は固有種で，その中でも特に多いのがコイ科魚類である。琵琶湖に生息するコイ科魚類の1種であるニゴロブナCarassius auratus grandoculisは，水産資源として重要漁獲対象種でありながら，2007年に環境省レッドリストの絶滅危惧種IB類に登録された琵琶湖の固有亜種である(生物多様性情報システムWeb:http://www.biodic.go.jp/rdb/rdb_f.html(絶滅危惧種情報，2012年6月1日))。本種は古来より，琵琶湖周辺の郷土料理である「ふなずし」の原料として，貴重な水産資源とされてきた。ニゴロブナの繁殖期は4月から6月にかけてであり，漁期もその時期と重なる。特に，抱卵した雌は高値で取引されるために漁獲圧が高く，個体数の減少が危惧されている。本種は，内湖や入江のヨシ帯等の浅瀬に産卵を行うことが確認されているが，湖岸の開発により産卵場所が著しく減少している。また，琵琶湖唯一の流出河川である瀬田川の南郷洗堰の水位操作により，梅雨時期の琵琶湖水位は低下し，フナ類の産着卵の干出，産卵の抑制，仔稚魚の生育場所の喪失が報告されている。近年，琵琶湖の水位を管理する国土交通省琵琶湖河川事務所では，コイ科魚類の産卵に配慮した水位調整に取り組んでいるが，フナ類の十分な資源回復には至っていない。さらに，オオクチバスやブルーギル等の外来種による被食の影響もあり，近年漁獲量が激減している。

A fish aggregating device (FAD) called a payao is conventionally installed to catch pelagic species in the Philippines. The waters around the Philippines are important regions for yellowfin tuna stocks because they include spawning grounds and nurseries. To understand the schooling behavior of juvenile yellowfin tuna Thunnus albacares around a payao, 13 juveniles (20.5-24.0 cm fork length) double tagged with ultrasonic transmitters (V7-2L-R256; Vemco Ltd.) and data loggers (DST-micro; Star-Oddi Ltd.) were released around a payao. A self-recording receiver (VR2-DEL; Vemco Ltd.) was attached on the mooring rope of the payao to follow the horizontal movements and data loggers recorded the vertical movements of tagged juveniles. Nine juveniles were recaptured simultaneously by ring net at the same payao after 4-7 days. One juvenile was recaptured by hand line at another payao 12 km away from the tagging site after 6 days. Recaptured juveniles showed a diurnal schooling pattern suggesting different school shape and foraging strategy between daytime and nighttime. Juveniles showed a diurnal horizontal moving pattern, concentrated near the payao during daytime, while they were distributed around the payao at nighttime. The fluctuations of swimming depth were synchronized among fish. Juveniles also showed a diurnal vertical movement pattern in surface mixed layer. They concentrated in a shallow and narrow range (11.2 +/- 8.2 m, mean +/- SD) at nighttime, while they were distributed to a deep and wide range (20.0 +/- 11.8 m) during daytime. The maximum vertical neighbor distance indicated the vertical thickness of the school and showed a peak around noon. Higher vertical movement speed during daytime indicated vertical foraging in a water column, while at nighttime the juveniles might forage horizontally following the diurnal migration patterns of prey in the surface layer.

We investigated the usefulness of acceleration loggers in aquaculture by examining net-cage use and metabolic rates in red sea bream, Pagrus major. First, the fish's metabolic rate (mg O-2 kg(-1) min(-1)) was measured with the logger in a swim tunnel at designated water velocities. We found that metabolic rate could be expressed by using a linear regression model of the activity rate index (unitless min(-1)) derived from acceleration data. Using this equation, the field metabolic rates of three fish in a net cage were monitored and were estimated at 14.1-15.0 kcal kg(-1) day(-1). The results suggested that 15-19% of energy from satiation feeding ration was consumed for metabolism and activity in the net cage. The loggers showed orderly net-cage use by the fish. Tagged individuals used the whole cage from surface to bottom, but individual fish that preferred the surface area rarely used the bottom, and vice versa. Metabolic rate increased significantly with distance of the fish from their preferred depths. The logger provided information on the physiological and behavioral responses of fish in a given breeding system, and its use should contribute to the design of practical aquaculture systems.

To understand how early juvenile yellowfin tuna use the habitat and environment provided by fish aggregating devices (FADs), fish (19-31 cm FL) implanted with ultrasonic transmitters into their abdominal cavities were released in a network of payaos in Panay Gulf, the Philippines. Self-recording receivers were attached to the anchor ropes of the payaos to detect the presence of the fish. Some aspects of the behavior of juveniles were similar to those reported in adults. One juvenile showed a diurnal vertical swimming pattern, swam within a limited shallow range during the nighttime, and dived to deeper waters during the daytime. Two juveniles performed deep dives over 100 m during payao-to-payao excursion. Three juveniles showed a diurnal horizontal swimming pattern that was synchronized. In contrast, juveniles stayed <6 days in the network, shorter than adults. No juveniles returned to the same payao after an interruption of over 24 h. It is suggested that juveniles in this area are just starting to migrate and are temporarily staying around a payao for a few days to forage before continuing their migration.

Seasonal habitat use by nigorobuna Carassius auratus grandoculis Temminck et Schlegel and gengoroubuna Carassius cuvieri (Temminck et Schlegel) in Lake Biwa was investigated using acoustic telemetry. Twenty-three nigorobuna and 11 gengoroubuna specimens caught using set-nets in the lake's south basin were surgically fitted with acoustic transmitters and then released. Signals from the fishes were recorded by 23 receivers installed around the lake. Between April and June 2007, the first spawning season after release, signals were received from all tagged fishes. Thereafter, until the second spawning season, signals were collected from 26 and 45% of released nigorobuna and gengoroubuna individuals, respectively. Seasonal habitat preferences for these species were studied by distance-based analysis. The analysis revealed that nigorobuna tended to stay near their spawning area in the south basin of the lake throughout the year, whilst gengoroubuna tended to show a seasonal migration pattern between the north and south basins. After the spawning season, the latter species migrated to the north basin where it remained until the next spawning season, when it returned to the south basin. This is the first report of seasonal migration of nigorobuna and gengoroubuna in Lake Biwa.

To elucidate the effects of hydrographic conditions on the migration and distribution of diamond squid (Thysanoteuthis rhombus) in the Sea of Japan, two numerical experiments were conducted using a Lagrangian particle-tracking model. First, Lagrangian simulations with different horizontal swimming speeds were conducted in the area off the San-in coast, the southwest Sea of Japan. The comparison results of simulations and experimental tagging records from 2003 suggest that horizontal movement of diamond squid over a few days is influenced by individual swimming, but long-term migration over more than about 10 days is dependent on the ambient current field. Secondly, further Lagrangian simulations with biological processes, forced by different hydrographic conditions in 2003-2005, were conducted. Temporal variations in distributions and sizes calculated by the model corresponded approximately to those of catch data. A large number of particles simulating squid were distributed over the nearshore region from the San-in coast to the Noto Peninsula during September-November every year. Differences in the migration route and distribution of particles among years were closely related to differences in hydrographic conditions such as the position of the main stream of the Tsushima Warm Current. Prediction of the catch off the San-in coast might be improved by considering hydrographic conditions in the southwest Sea of Japan.

The horizontal and vertical movements of eight immature hatchery-reared (F2) Mekong giant catfish Pangasianodon gigas were monitored using acoustic telemetry in the Mae Peum reservoir, Thailand, from September to December 2005. All tagged fish were successfully monitored throughout the study period. All fish moved throughout the reservoir for approximately 1 month after release. Subsequently, their utilized areas became small, and the fish utilized deep areas of the reservoir. The fish displayed diel spatial movement patterns between deep areas in the day and shallow areas in the night. The vertical movements of the fish were related to the environment declination such as existence of hypoxic water and thermocline. Our results suggest that the establishment of a protected area in addition to conventional fisheries regulations may sustain the fish population in this reservoir. © 2008 The Japanese Society of Fisheries Science.

フィリピンのパヤオ(浮魚礁)周辺で,キハダ幼魚の腹腔内に超音波発信機を挿入して放流し,パヤオのアンカーラインに装着した受信機で行動をモニタリングした。キハダ幼魚はパヤオ周辺にとどまり,同時にモニタリングした同サイズのツムブリに比べ,明らかに深い層を遊泳した。夜間は比較的浅く狭い層を遊泳し,昼間は深く広い層を遊泳する日周性や,深夜にパヤオから離れるなど,これまでに報告されているキハダ成魚とよく似た行動を示した。再捕結果から摂餌や移動が確認され,キハダ幼魚のテレメトリーが可能であることが示された。

We tracked eight matured chum salmons (Oncorhynchus keta) using acoustic and radio telemetry to understand their upriver migration around ca. 120 to 180 km site starting from the mouth of the Ishikari River in autumn 2002-2004. This study area was divided into the natural levee area, the gorge area, and the basin area including the past major spawning sites until ca. 1940s. Three tagged fish reached to the basin area, and two fish reached to the natural levee area. The maximum duration of the upstream migration was 17 days, and the maximum migration distance was 56 km. Mean migration speed in the basin area was 6.6 km/day, where the staying behavior was frequently observed, was approximately three times slower than those of the natural levee area (19.5 km/day) and the gorge area (14.8 km/day). The basin area had better conditions of substrates, depth, flow velocity and subsurface flows for O. Keta spawning than the other areas. In addition, groundwater upwelling for egg survival and hatching occurs adequately in the basin area. Their migration patterns reflected geographical differences among three areas. Therefore, the observed slower migration in the basin area was probably due to their pre-spawning behaviors including searching for spawning sites and mates. The faster migration in the natural levee area and gorge areas was due to utilization of these areas as corridors. © 2009, Ecology and Civil Engineering Society. All rights reserved.

The occurrence of common carp, Cyprinus carpio L., and the environmental conditions near a set-net were monitored using acoustic telemetry and a data logger to elucidate the conditions under which carp approached the net. The occurrence of one-tagged fish was analysed using a genetic algorithm (GA); GAs are based on genetic mechanisms and use the natural selection of genotypes to model various explanatory variables to provide a solution. The conditions near the set-net were simulated, including the current profile, wind system, water temperature and rainfall, and the pattern of factors that influenced the occurrence of the tagged fish were assessed using the GA. The occurrence of the tagged carp was related to lower water temperatures. The GA approach selected a significant portion of the truly important factors. Many factors can influence fish behaviour and GAs are an effective method for the analysis of complex biological phenomena.

Twenty-eight immature hatchery-reared Mekong giant catfish Pangasianodon gigas tagged with acoustic transmitters were released in the Mekong River, Thailand from 2002 to 2004. Twenty-four and four fish were tagged with normal transmitters and pressure-sensitive transmitters, respectively. Five to seven automated monitoring receivers were used for monitoring the post-release movements. The tagged catfish could be detected for up to 97 days, the first detection taking place at the release point, where the fish remained for several days. Sixteen tagged fish (57%) were not detected at any later point. These fish may have passed along the opposite (Laos) side of the river without notice because the width of the river was larger than the detection range of the transmitter. The remaining 12 tagged fish (43%) could be detected by the receivers installed, excluding the release point receiver. Of these 12 tagged fish, six showed long-distance (30-80 km) upstream movements and one long-distance (50 km) downstream movement. These seven fish (25%) were detected only during the daytime, suggesting that the Mekong giant catfish is diurnal.

テレメトリーにより琵琶湖南における二ゴロブナの行動解析

The horizontal and vertical movements of eight immature hatchery-reared Mekong giant catfish Pangasianodon gigas were monitored using acoustic telemetry in Mae Peum Reservoir, Thailand between 2003 and 2004. The fish were monitored for between eight days and more than 9 months. All of the fish moved over the entire reservoir within approximately 40 days after release. Subsequently, the home range became small approximately 40 days after release. The fish preferred deep areas in the reservoir. The fish displayed diel horizontal and vertical movement patterns. The fish showed larger-scale horizontal movement during the daytime than at night. The fish repeatedly showed active vertical movement during the day, whilst there was little variation in swimming depth at night. Our results imply that the vertical movements of the fish were related to the environmental condition of the reservoir.

The vertical movements of one Mekong giant catfish Pangasianodon gigas were monitored for 3 days in August 2004 using a depth-temperature micro data logger. The logger was recovered using an innovative time-scheduled release system and located by searching for VHF radio signals. The logger was found approximately 2.2 km away from the release point and provided (n=705,128) depth and temperature data collected over a period of 98 hours following the release. The fish spent more than 99% of its time at less than 3 m below the surface. The maximum swimming depth was 5.6 m. No sharp thermocline was present during the experiment. Temperature did not have any detectable effect on the pattern of vertical movement of the fish. The dissolved oxygen concentration (DO) was stratified, with a concentration of >60% saturation in the first 3 m below the surface failing to 10% saturation at depths lower than 4 m. This specific DO stratification was found to limit the vertical movement of the catfish.

The behavior of wild and hatchery-reared red tilefish Branchiostegus japonicus was analyzed using two different methods: video observation and acoustic telemetry tracking. In the laboratory, digging and swimming activity of seven wild and five hatchery-reared fish were recorded for 2-4 days in an experimental aquarium and related to changes in light intensity. The activity of wild individuals increased with light intensity, while hatchery-reared individuals were active during both day and night. In the field, 18 wild and 9 hatchery-reared fish were released and tracked using an acoustic telemetry system during the winter and the summer in Maizuru Bay, Kyoto (Japan). Seven wild and three hatchery-reared fish settled within 2 km of the release point for 21-200 days whilst 11 wild and 6 hatchery-reared fish were detected in the central part of the bay within 13 days. The settled fish demonstrated a diel pattern of behavior; most of them probably stayed outside their burrows in the daytime but inside their burrows during the nighttime. During the winter wild fish tended to stay near the release site for longer periods than the hatchery-reared fish. However, in summer the hatchery-reared fish tended to remain close to the release site for longer than the wild fish. Based on these two experiments, we suggest that the activity of wild red tilefish respond to changes in low levels of light intensity (0-0.1 mu mol m(-2) s(-1)) at dawn and display a diel behavior. Hatchery-reared fish may differ from wild fish with regard to their behavior, response to water temperature and light conditions.

琵琶湖のエリ漁には,漁場に吹く風が漁獲量に影響を与えるという伝承事項が古来から存在する。この伝承事項の発生は,湖面に強い風が吹いた時に湖水の水温が変化し,漁場へのコイの来遊に影響を与えるためと考え,2003年6月〜9月に,琵琶湖南湖のエリ周辺で水温,風系,コイの行動を測定した。本エリで漁獲されたコイ4尾の腹腔内に超音波発信機を装着し,受信機を設置したエリ周辺で放流した。その結果,最大で95日間にわたって供試魚の出現を測定することが出来た。記録計によってエリ周辺の水温2層(2.5m, 4.5m)を15分間隔で測定した。供試魚は水温が25℃以下の間はエリ周辺に出現したが,25℃を超える水温上昇に伴いエリ周辺を離れた。その後,南西あるいは北東の強い風が吹き,急激に水温が25℃前後に低下したあとに供試魚は再び出現した。本研究の結果では夏季におけるコイの行動と急激な水温低下現象との間に一定の関連性が認められた。

日本海のソデイカ立縄漁具は,箱形のブイ,幹縄(loom),錘,および枝糸(8mおよび15m長)を介した2個の擬似餌で構成されている。本研究では,小型水深計を錘部と擬似餌部の計3箇所に装着し,水深や三者の位置関係から挙動を計測した。投入された漁具は,錘,擬似餌部の順で沈降し,最大水深に達するまでの平均沈降速度は40〜51cm/secであった。錘部と擬似餌部は,3.5〜4分間で最深帯に到達した後,安定状態に到った。漁具位置関係(相対角度)は,漁具の沈降中だけでなく,安定状態時でも絶えず変化していた。漁獲水深帯は,海流が弱い条件下では幹縄の全長よりもわずかに小さい程度であったが,海流が強い時には幹縄の全長よりも20〜30m浅く,想定した水深帯で漁獲されていない可能性が示唆された。

Biotelemetry is a powerful technique that provides continuous and simultaneous monitoring of fish behavior in their natural environment. The interaction between fish and fishing gear was monitored by biotelemetry. This paper presented three examples of applying biotelemetry to fish behavior around fishing gear. First, three set receivers were installed on leader net of a set net in Lake Biwa, and largemouth bass implanted with a coded ultrasonic transmitter were released near the set net. After northeasterly winds, southwestward currents, and declines of the ambient water temperature, the fish was away from the set net. Catch efficiency using passive fishing gear is affected by environmental factors. Next, a receiver was installed on an anchor line of a Payao in the Philippines. Three yellowfin tunas and two rainbow runners were implanted with the transmitter and released near the Payao. Almost of the fish remained around the Payao for over 60 hours. One of the aggregative keys of the FADs might be the emergence of prey. Third, when a diamond squid was captured by a jig with a data logger in the Sea of Japan, accelerations and depths were recorded in the logger. The results suggested that the jig lured the squid by moving vertically, vibrating, and changing its posture. Biotelemetry, in collaboration with fishing gear telemetry, is helpful to make clear the capture process of the gear.

The continuous observation of salmon behaviour in some wild environments can be extremely difficult. We recorded spawning behaviour of female chum salmon (Oncorhynchus keta) in the field simultaneously using visual observation and fish-borne data loggers with two-axis accelerometer sensors. Using only acceleration records, behaviours were successfully classified into the eight well-known components of spawning behaviour: swimming, nosing, exploratory digging, nest digging, probing, oviposition, covering and post-spawning digging. To understand how the female chum salmon modulates spawning behaviours in relation to changes in environmental conditions, we compared the behaviours of salmon during normal flow of clear water to those of salmon during the heavy flow of turbid water after a storm. Salmon in the normal flow showed all eight behaviours, whereas salmon in the heavy flow showed only three behaviours: swimming, nosing and exploratory digging. The proportion of time spent on swimming was greater in the heavy flow than in the normal flow (mean of 98.47% vs. 92.84%). Moreover, the proportion of tail beating in swimming was greater in the heavy flow (77.86%) than in the normal flow (15.63%). Our results indicate that the behaviour of female chum salmon was strongly affected by the heavy flow of turbid water after a storm. The recording of accelerations is a promising method for clarifying the spawning behaviour of salmonids in the wild where continuous visual observation is too difficult.

In order to establish techniques for the stock enhancement of red tilefish Branchiostegus japonicus, it is important to understand the behavioral characteristic of both hatchery-reared and wild fish. Four hatchery-reared and six wild fish were released and tracked using acoustic biotelemetry in Maizuru Bay, Kyoto, Japan, from August 2003 to February 2004. Data for the four wild fish released and tracked from January 2003 to May 2003 were also referred to for analysis. The released fish moved around in relatively large areas within about 10 days after the release, and then three hatchery-reared and two wild fish settled and stayed within limited areas. Fish of both origins showed strong site fidelity and diel activity patterns, i.e. they were detectable in the day but not at night, probably due to hiding behavior in their burrows at night. However, some discrepancies between fish of both origins were detected by comparing their track terms and activity patterns in detail. These discrepancies are probably attributable to the differences in environmental conditions that the fish had experienced before release.

For conservation and successful stock enhancement of endangered species, an understanding of the movement patterns and behavior of the target species is indispensable. The Mekong giant catfish, Pangasianodon gigas, is endemic to the Mekong Basin and now is threatened with extinction. Although biotelemetry using acoustic transmitters and receivers is expected to reveal its movement patterns and behavior, the most suitable attachment method for the transmitter to the catfish is unknown. In this study we examined the effects of external attachment and surgical implantation on the survival and growth of the catfish, compared with those in control individuals, in an earthen fish pond for approximately 2 months. No fish died during the experimental period. Furthermore, we found no fungal infections in any fish and no significant differences in growth rate among treatment and control fish. However, all transmitters of externally tagged fish were lost during the experimental period. In contrast, transmitters of some surgically implanted fish remained in the peritoneal cavity. In conclusion, the surgical implantation technique is suitable for long-term monitoring of the catfish.

How fish find their original habitat and natal home remains an unsolved riddle of animal behaviour. Despite extensive efforts to study the homing behaviour of diadromous fish, relatively little attention has been paid to that of non-diadromous marine fish. Among these, most rockfish of the genus Sebastes exhibit homing ability and/or a strong fidelity to their habitats. However, how these rockfish detect the homeward direction has not been clarified. The goal of the present research was to investigate the sensory mechanisms involved in the homing behaviour of the black rockfish Sebastes inermis, using acoustic telemetry. Vision-blocked or olfactory-ablated rockfish were released in natural waters and their homing behaviours compared with those of intact or control individuals. Blind rockfish showed homing from both inside and outside their habitat. The time taken by blind fish to reach their home habitat was not significantly different from that of the control fish. In contrast, most olfactory-ablated fish did not successfully reach their original habitat. Our results indicate that black rockfish predominantly use the olfactory sense in their homing behaviour. (c) 2005 Elsevier B.V. All rights reserved.

Wild red tilefish Branchiostegus japonicus were tracked and/or monitored for up to nearly 3 months in Western Wakasa Bay and Maizuru Bay, Japan, using ultrasonic telemetry to examine their movements and burrow fidelity patterns. In Western Wakasa Bay, it is guessed that fish released in relatively shallow waters, about 30 m deep, actively moved into more suitable deeper habitats after their release. In Maizuru Bay, the fish did not undertake large-scale movements and showed burrow fidelity about 1 month after their release. That is, the fish primarily remained in the burrow, which was constructed in the sea-bottom, during the night and moved outside the burrow during the day. The marked circadian rhythm from Fourier analysis indicated a clear diel movement pattern of the red tilefish.

The Heart rate and the activities of a red sea bream were measured simultaneously in a saltwater pond. The heart rate was measured using an ultrasonic transmitter. The activities including 2 axes acceleration, swimming speed and depth were measured using a data logger. After sunrise, the fish became active and the heart rate showed 8% increase. Applying the relationship between metabolic rate and ambient water temperature obtained in laboratory trials, the oxygen consumption and the out put volume were estimated to have 18 and 10% increase, respectively. The estimated metabolic rate by applying the equation of motion was an overestimate considering the energy efficiency. While the fish dashed and cruised with tail beat frequencies at 3.8 and 1.8 Hz, respectively, the heart rate was stable.

近年普及してきたデジタルビデオカメラ(DV)を用いて,オオクチバスの遊泳行動を簡易的に解析した。回流水槽内で強制的に遊泳させ,遊泳フォームをDVにより撮影した。オオクチバスは1.17±0.16 TL/sec(対全長比速度)以上で一定の尾鰭振動数と振幅で遊泳したが, 1.88±0.24 TL/sec 以上ではBurst-and-coast遊泳を示し, 3.29±0.92 TL/sec 以上では遊泳の持続が不可能であった。大型アクリル水槽内でキンギョを餌として与え,一連の捕食行動を正面と側面に設置した2台のDVで撮影した。最高遊泳速度,加速度はそれぞれ, 5.8 TL/sec, 8.5m/sec^2に達した。低い耐久力と高い瞬発力に特徴付けられる遊泳は,待ち伏せ型であるオオクチバスの捕食戦略を反映している。

To increase catch efficiency, it is necessary to understand the habitat utilization of the target fish around fishing gear. A biotelemetry study using coded ultrasonic transmitters and set receivers was conducted to understand the habitat utilization of largemouth bass around a set net in Lake Biwa, Japan. Three receivers were installed on leader nets of the set net at short intervals by design to understand the fine scale movement of fish. Four fish were implanted with a coded ultrasonic transmitter and released near the set net. Two fish were monitored for over 50 days and showed diurnal habits. Just before the fish left the set net. the main current direction was southwestward and the current velocity was over 5m/sec. In a set net fishery, current profile is an important factor affecting the concentration and dispersion of the target fish.琵琶湖固有の定置網であるエリ周辺で,コード化超音波発信機と設置型受信機を用いてオオクチバスを追跡した。オオクチバス4尾(TL : 34.0～37.0cm)の腹腔内に受信機(Coded V8SCL, VEMCO製)を埋め込み,エリの中心に放流した。エリの垣網に設置型受信機(VR2. VEMCO製)3台を250mと敢えて間隔を狭めて仕置し,詳細な移動を把握した。50日以上追跡した2尾は, 10℃以下の低水温にも関わらず,昼間にエリから遠ざかり,夜間にエリに近づく日周移動を示した。同時にエリ周辺に設置した流向流速計の記録から,5m/sec以上の南西流が卓越した後,個体はエリから遠ざかったことが分かった。受動型漁具である定置網の漁獲には対象魚の移動と周辺の流動環境が密接に関わっていると考えられる。

Japanese sea bass Lateprabrax japonicus, captured in the western shore protection region of Kansai International Airport in Osaka Bay, were released near the place of capture with coded ultrasonic transmitters attached (9 individuals in August 2001 and 11 individuals in November 2001). The behaviors of these fish were monitored with 10 ultrasonic receivers, set along the western seawall (8 receivers) and off-shore (2 receivers). As a result, half of the fish provided continuous signals, whereas the others ceased to send signals immediately after the release. The signals of fish which sent continuous signals also broke off for over one day, suggesting that the sea bass occasionally went beyond the range of the receivers (ca. 350 m). Fish often failed to send signals during the neap tide until the spawning season and drning a cold spell or after an atmospheric depression in the spawning season. We suggest that their off-shore migration is related to tidal and atmospheric changes.

The black rockfish Sebastes inermis is one of the most important fishery species along the coast from southern Hokkaido to Kyushu, Japan and is often found in rocks and Zostera areas. We conducted biotelemetry using coded ultrasonic transmitters to clarify the movement of the black rockfish that inhabited the seawall of the Kansai International Airport. We released 25 black rockfish at two points. One was the airport seawall and the other was side shallows off the Sensyu district. Seventeen black rockfish returned to their capture site after release. We used the V-test to determine whether the direction of movement was random or orientated. The black rockfish moved at random along the seawall within some hours after release (P>0.05). Four hours after release, they moved to their home site intentionally (P<0.0025).

The long-term behaviour of immature yellowtails, Seriola quinqueradiata, was studied using electronic data-recording tags in Sagami Bay, Japan, during the autumn and early winter. Temperature or depth data were continuously recorded for 5-69 days on six yellowtails. The temperature recorded from the 0-year-old yellowtails showed only small variations (< 0.5 degrees C day(-1)) around the SST on the coast, indicating the 0-years stayed in the immediate coastal area with little horizontal movement. The 1-year-old yellowtail showed larger temperature variations that reached 3 degrees C day(-1), which implies distinctly larger horizontal movements than the 0-year-olds. Depth records showed the 0-years stayed around 10 m while the 1-year yellowtail swam in deeper water (mainly 10-30 m) with large variations. The latter often dived to 40 m in the daytime, but shallower than the depth of the thermocline. Both temperature and depth records showed apparent diurnal patterns. Comparing the fish data with environmental conditions, it is suggested that 1-year yellowtails stay close to the coast during the night, move at dawn to feed in the daytime and return at dusk via a frontal zone. In addition, wind stress could change yellowtails' behaviour.

Two experiments were executed to investigate the correlation among water temperature, metabolic rate and swimming behavior of red sea bream Pagrus major. In the former experiment, the relationship between oxygen consumption and water temperature was measured in laboratory respirometry trials. The result shelved water temperature (T, degrees C) has the following correlation with oxygen consumption (OC, mg min.(-1) kg(-1)); OC=1.47+0.01x1.22(T), R=0.92. In the latter experiment, a wild adult fish was tracked in the open sea using an ultrasonic transmitter to record the horizontal migration paths, vertical swimming trajectory and ambient water temperature. The fish rested on the bottom during the day. While at night, it swam up and down within the depth range 30 to 80 m. The ambient water temperature ranged from 18.5 to 22.9 degrees C. In the period of resting, the red sea bream was estimated to consume oxygen ranging from 1.91 to 2.55 mg min.(-1) kg(-1), in the open ocean. During the experimental period of 28 days, the fish remained within a shoal and moved only small horizontal distances. Fluctuation of ambient water temperature seemed to have little effect on the swimming behavior of red sea bream.

An acoustic transmitter and two micro data recording tags were used to observe the behavior of yellowtails Seriola quinqueradiata, in Sagami Bay, Japan from 24 October through 19 November. Depth data were continuously recorded for 23 days and temperature data for 27 days with a 20-minute interval. The yellowtails showed an apparent diurnal vertical migration pattern in their movements; they crossed the thermocline actively during the daylight hours, but calmed down and remained in the shallow layer above the thermocline at night. Their movements were changed by environmental temperature variation: 1) After the ambient water temperature rapidly decreased, a change was seen in the average depth and pattern in the vertical movement of the yellowtail. 2) They could move vertically to avoid the warm water from the Kuroshio because no ambient temperature rise and no shallower position were observed when the warm water intruded into the bay from the Kuroshio.

The trackings of Lake Biwa catfish were executed to examine how migratory they were and what habitat they selected in Lake Biwa in 1993, 1995 and 1996 by ultrasonic biotelemetry. Eight individuals were tracked for a maximum of 118 days in the South Basin, and 11 individuals for a maximum of 319 days in the North Basin. In the South Basin experiments, 7 individuals quickly returned to their caught place, and 5 individuals didn't change their settled positions in the South Basin from July to October. In the Shiozuwann Bay experiments, 9 individuals settled around the shallow floor near their spawning ground in the Shiozuwann Bay throughout the year. It was shown that Lake Biwa catfish had settlement characteristics, less migratory, and mainly inhabited in the shallow area near the spawning ground all the year round.

旋網漁具の動態を数値シミュレーション技術を用いて解析するとともに，対象魚類の三次元行動軌跡を構築することにより，カツオ・マグロ類を対象とした旋網漁業の漁獲メカニズムを評価した。メバチ3個体の操業中の行動軌跡を取得した。投網後，個体が旋網に取り巻かれてからは個体の移動ベクトルの方向は鉛直・水平方向に短時間で大きく変動した。漁具の動態解析結果から網裾の最大到達深度は200mに達する一方で個体は100m以浅を遊泳し，網を締め巻き始めてからは遊泳速度は30%減少した。投網後1500秒経過すると，網地目合が縦方向に伸長されるため，メバチの若齢魚は身網の半分以上で通過不可能となることが示唆された。

本研究ではバイオメカニクス(生体力学)研究を通して,クロマグロの遊泳能力と遊泳メカニズムそして本種の遊泳に対する形態機能を解明することを目的としている。3次元形態計測から本種のデジタル形態モデルを作製し,これを用いたCFD(数値流体力学)解析から本種の遊泳時流体力学的特性を明らかにした。成長に伴って魚体の抵抗係数は減少する傾向を示した。本種の遊泳時抵抗はおもに尾鰭の振動振幅の大きさに依存し,振動周波数はほとんど影響しないことがわかった。水平遊泳時の重心回りのモーメント推定から本種は低速遊泳時ではわずかに頭上げの姿勢で遊泳する必要があること,また,エネルギー効率を優先した遊泳では深い角度でグライドし,浅い角度で上昇する遊泳式が有利であることを理論で導いた。この推定結果は遊泳姿勢と尾鰭振動を記録する小型記録計で実海域計測されたフィールドデータによって裏付けられた。負の浮力である本種は自重を支持するために,胸鰭は揚力発生の重要な機能を果たしていると考えられていたが,CFD解析結果からも大きな揚力を発生できる器官であることが確認された。実際の個体で確認するため,磁力を用いて胸鰭の開度を記録する小型記録計を開発し,実海域実験を実施した。低速で遊泳するときには頻繁に胸鰭を大きく拡げ,揚力を獲得していることが明らかとなった。本種幼魚の遊泳時に計測される代謝エネルギーから遊泳時のエネルギー変換効率を見積もるため回流水槽を用いた生体実験を実施した。その結果,本種単位重量当たりの移動エネルギーコストに換算すると平均15000J/kg/kmであった。これに対し,CFDに基づいて,算出された遊泳に必要な仕事(エネルギー)は移動エネルギーコストの2-4%程度でしかなく,幼魚期では代謝エネルギーのほとんどが体温維持に使用されていることが示唆された。

ウミガメ類(オサガメ、アオウミガメ、アカウミガメ、タイマイ、ヒメウミガメ、ケンプヒメウミガメ、ヒラタウミガメ等)の分布は亜熱帯から熱帯域を中心に世界中にひろがり、大規模な摂餌・産卵回遊を行っている。これらウミガメ類全種で生息頭数が減少していると考えられている。アセアン諸国海域においてもその例外ではない。ウミガメ類の生息数の減少は、地球規模での海洋環境の変動などの自然要因に加えて、リゾート開発等に伴う砂浜の減少や灯火による産卵場の減少並びに漁業による混獲など人為的な要因も大きいと考えられている。特にエビ類を対象としたトロール漁業によるウミガメ類の混獲が近年問題とされている。本研究は、H13-15科研費「アセアン諸国海域におけるアオウミガメの大回遊機構解明」で設定していなかった稚ガメの回遊機構を明らかにするために、タイマイの回遊経路を把握した。また、人工的にふ化させて養成した稚ガメと天然海域で育った稚ガメとの行動に違いがあるか否かについて、成長段階毎に放流実験を行って検証した。この結果、ふ化直後に有する沖合へと向かって遊泳する能力が、成長と伴って失われていくこと、ならびに天然海域で育った稚ガメに比べて、人工的に養成された稚ガメは潜水能力には差はないものの、表層で滞在する時間が有意に長いことが分かった。

絶滅の危機に瀕したメコンオオナマズの保護に資するため,タイ国メコン川において養殖メコンオオナマズにID識別型超音波発信機を装着して放流し,追跡した。2004年7月に,4尾(全長76.5〜82.5cm,体重4.6〜5.7kg)の腹腔内にID識別型超音波発信機(CodedV16,Vemco)を埋め込み,ナコンパノム近郊のメコン川に放流した。ミャンマーとの国境に近い上流のチェンコーンからラオスとの国境に近い下流のコンチアムまでのタイ国内を流れるメコン川全流域に7台の設置型受信記録機(VR1,Vemco)を設置し,放流後の移動を追跡した。放流直後,供試魚は約1週間にわたって放流地点周辺にとどまったが,その後移動を開始し,1尾が1.9日後に40km上流まで,さらに4.7日後に100km上流まで移動した。移動速度は21km/日であったが,それ以上上流に移動することはなかった。さらに詳細な移動状況を把握するために,4尾(全長76.5〜84.0cm,体重4.9〜5.8kg)の腹腔内に水深センサー付超音波発信機(CodedV16P,Vemco)を埋め込み,放流地点の上流40kmと100kmに設置した2台の設置型受信記録機(VR2,Vemco)により移動中の遊泳水深を記録した。40km上流の受信機により約10分間にわたって1尾の遊泳水深が記録され,メコンオオナマズは水深1〜12mの範囲で鉛直移動を伴いながら移動していたことが明らかとなった。昨年度までに得られた結果と併せると,養殖メコンオオナマズは放流後,上流に移動する傾向があり,その移動範囲は最大で約100km,移動速度は約20km/日,移動中に鉛直移動を伴うことが明らかとなった。

世界に生息するウミガメ類は亜熱帯域から熱帯域を中心に、摂餌・産卵回遊を行っている。現在、ウミガメ類の全種において、その生息頭数が減少していると言われている。特に東南アジアにおけるアオウミガメ、タイマイ、オサガメ、ヒメウミガメについては絶滅の危機に瀕しているとされているが、その生態については全く未解明であった。 このため本研究において、これらのウミガメ類の内、特にアオウミガメについてその回遊経路を解明すべく研究を開始した。具体的にはアオウミガメの回遊経路を人工衛星送信機(アルゴス送信機)を甲羅に装着することによって追跡を行った。 平成13年度に12台、平成14年度に12台の合計24台のアルゴス送信機をタイ国のタイ湾側とアンダマン海側、並びにマレーシアのタイ湾側で産卵のために上陸したアオウミガメの雌成体に装着して追跡した。その結果、タイ湾側においては湾奥に位置する産卵場から放流したアオウミガメは大きく次の回遊経路を辿った。1.タイ湾を東へ海岸沿いに回遊し、カンボジアないしはベトナム沿岸へ行く経路。2.タイ湾を東へ沖合を横切り、南シナ海へと辿る経路。3.沿岸を回遊する個体。アンダマン海においては、産卵場であるシミラン諸島フーヨン島からの放流個体の殆どがアンダマン海を横切り、インド領であるアンダマン諸島沿岸へと回遊した。このようにタイ湾およびアンダマン海ではそれぞれ摂餌を行う海域が異なっていることが明らかとなった。これらの海域の個体が遺伝的に隔離されているか、あるいは交流があるのかについて、DNAによる解析を行った。この結果、両者には殆ど差違がないことが分かった。本研究期間中、タイ国を中心にアセアン諸国のウミガメ研究者を招き、SEASTAR2000ワークショップを3回(平成13年度プーケット、平成14年度及び15年度バンコク)開催し、プロシーディングスを出版した。更に本研究の成果を下に平成16年3月、タイ側共同研究者1名に京都大学学位が授与された。

近年のマイクロエレクトロニクスの急速な発展は、海洋生物の行動生態研究に画期的な研究手法を提供することとなった。現在、各種のマイクロデータロガーや超音波テレメトリー並びに人工衛星によるテレメトリーなどによって、海洋生物の遊泳水深、遊泳速度・加速度、経験水温、体内温度等が得られるようになってきている。また、我々の研究によって自由遊泳中の海洋生物の心拍数の計測も可能となった。 本研究においては、これらのセンサーに加えて、地磁気センサーを搭載したデータロガーを開発し、これにより海洋生物の三次元行動を測定しようとするものである。 平成12年度、地磁気センサーと加速度センサーを組み合わせた最初のプロトタイプを製作した。このプロトタイプを平成12年度及び13年度に亘ってタイ国水産局(現海洋沿岸資源局)傘下のウミガメ保護ステーションにある飼育池(約5ヘクタール)で実際のウミガメ(アオウミガメおよびタイマイ)に装着してデータを取得した。この実験によって、このプロトタイプのデータロガーによってウミガメの遊泳方向並びにウミガメの遊泳推進力であるフリッパーの頻度が測定できることが分かった。これらの実験結果を下にプロトタイプの改良を行い平成14年度と15年度に実海域実験をアンダマン海におけるアオウミガメの重要な産卵地であるシミラン諸島フーヨン島において実施した。この結果、当初の目的であるウミガメの実海域における三次元の遊泳行動の再現に成功した。

近年のマイクロエレクトロニクスの急速な発展は、水圏生物の行動生態研究に画期的な研究手法を提供するに至っている。特に、テレメトリーを生物行動に応用したバイオテレメトリーは、装置の小型化および記憶容量の増大ならびに伝送データの高度化が著しい。しかし、水圏においては電波によるデータ転送が困難なことから、従来のテレメトリーは比較的単純なデータのみを対象としていた。本研究では"百聞は一見に如かず"の諺どおり、ビジュアルなデータを水圏生物の行動生態研究に導入するべく、新たなデータロガーを開発するとともに、画像処理技術を応用した効率的な観察研究を実施した。 初年度、白黒画像を撮影できるCCDを搭載したCCDロガーの試作品を開発した。本年度において、CCDをカラーに変更した。大きさは92mm×40mm×28mmで空中重量約200gである。初年度は樹脂製のケースで耐圧400mであったが、本年度において、ケースをチタン製に変更し、耐圧500mを実現した。本CCDロガーをタイ国ウミガメ保護ステーションにおいて飼育されているタイマイに装着し、水中画像を撮影した。 CCDによる画像解析を応用し、サザエならびにアワビの行動を自動解析するシステムを構築した。本システムによって、両種の24時間連続行動測定に成功した。

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