Study on behavioral characteristics of wild and hatchery-reared red tilefish

Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society InfrastructureDecember 13-15, 2004, Imperial Tara Hotel, Bangkok, ThailandThe diel activity of red tilefish Branchiostegus japonicus was studied using two different methods : analysis of biotelemetry records and video observation. We have acquired the biotelemetry tracking records of the red tilefish which were released in Maizuru Bay and tracked from January 2003 to February 2004. The records ware compared to the time of sunrise and sunset, the duration of sunshine, and the lunar cycle, which may influence on light conditions. Whilst the fish showed diel activity, the fish changed their behaviors along with the time of sunrise and sunset; the fish probably moved out of their burrows in the daytime and retreated into the burrows at night. We could not find a clear relationship between the behavior and the other two factors. In the laboratory, the behavior of one hatchery-reared individual was recorded by video for five days in the experimental tank where the light condition changed periodically over 24 hours. The fish was more active in the light periods (550 lx) compared to in the dark periods (0 lx). Since the results from the two methods probably compliment one another, further experiments using the two methods will reveal the detailed behavior of red tilefish

THE ULTRASONIC TRACKING OF MEKONG GIANT CATFISH PANGASLANODON GIGAS IN MEKONG RIVER

Southeast Asia Sea Turtle Associative ResearchBangkok, Thailand, 16-19 December 2002The Mekong giant catfish Pangasianodon gigas is endemic to the Mekong River, measuring up to 3 m in length and weighing in excess of 300 kg. The number of the wild catfish in the Mekong River has decreased due to the development of the Mekong River these days. Therefore, ecological researches are urgently needed to conserve the catfish. However, there was no method to monitor the movement of the catfish continuously in the Mekong River. The objective of this study was to test a feasibility of coded ultrasonic tracking system to monitor the contineous movement of the catfish in such a large river, the Mekong River. We released ten cultured catfish in the Mekong River. The catfish tended to move downstream or stayed around the release point just after the release. Four of ten catfish moved upstream for 60 km in 2-3 days although one fish moved downstream for 40 km. This tracking system that we tested could be a feasible system to monitor the continuous movement of the catfish in such a large river, the Mekong River

Growth rates, relative growth and a potential aging method using vertebral centra in Silurus biwaensis(Siluriformes: Siluridae)

Relative growth and relationship between age and growth in Silurus biwaensis were examined on the basis of the body size data of the catfish collected from Lake Biwa and the reared catfish which were hatched from artificially inseminated eggs. Although it had been reported that the proportion of head length to body length increased with growth in S. biwaensis, such a relationship was not found for 218 catfish that were examined in this study. On the other hand, the proportion of head length to head width significantly decreased with SL in females. This result indicated that the narrow head shape peculiar to S. biwaensis becomes slightly squarer in bigger females. The three catfish reared from the hatching grew to 196-410mm SL for 2.7 years (73-152mm/yr). This growth rate was in contrast with that of a tagged adult male, which grew only 50mm from 460mm SL to 510mm SL in the lake for two years (25mm/yr). These results suggested that the growth of the adults might extremely slow down after the fast growth at the immature stage. This study also reported that the number of transparent zones in vertebral centra of S. biwaensis increased with growth. The vertebral centrum may possibly be utilized as an age indicator for this species and the other kinds of Silurid

A validation of abstracted dive profiles relayed via the Argos satellite system: a case study of a loggerhead turtle

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

Striped catfish (Pangasianodon hypophthalmus) exploit food sources across anaerobic decomposition- and primary photosynthetic production-based food chains

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

<Session 1: Fish Telemetry I>Positioning of largemouth bass in Lake Biwa, Japan

19–22 May 2016 Kyoto, JapanLake Biwa is one of the world's few ancient lakes and is Japan's largest freshwater lake. Over 50 species offish live in the lake including 15 endemic species/subspecies. Largemouth bass (Micropterus salmoides) were introduced into the lake in the 1970's and have drastically increased their number at the expense of the native species. Professional fishermen in the lake are making every effort to exterminate the aliens using set nets, gill nets and electric shocker boats. For an efficient catch, positions of largemouth bass were examined using VPS (Vemco Positioning System). Bass were equipped with a coded ultrasonic transmitter with depth and temperature sensors. Receivers installed to construct a polygon calculated the position of bass using the delay of signal detections among receivers. From November to December, as home ranges of bass were narrow and bass stayed in shallow waters, electric shocker should be effective. In January, as core areas were narrow and bass stayed in deep waters, active fishing, such as seiners might be effective. In February, as home ranges were wide and bass moved frequently, passive fishing, such as gill nets seemed to be effective

Hatchery-reared Mekong giant catfish utilized deep areas in the Mae peum reservoir, northern Thailand

December 15-17, 2007, Royal Phuket City Hotel, Phuket, ThailandThe juvenile and young hatchery-reared Mekong giant catfish Pangasianodon gigas have been released into the reservoirs throughout Thailand. For the sustainable reservoir fishery of the giant catfish, new science-based fishery management measures are expected in Thailand, such as the establishment of protected areas. Therefore, the habitat use of the hatchery-reared giant catfish has been investigated in the Mae peum reservoir from 2003 to 2005. Our results suggest that the hatchery-reared fish primarily utilized deep areas in the reservoir. The deep areas which the fish primarily utilized may be suitable as protected areas in the reservoir

Study on feeding habits of Mekong giant catfish in Mae peum Reservoir, Thailand

Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society InfrastructureDecember 13-15, 2004, Imperial Tara Hotel, Bangkok, ThailandIn order to recapture Mekong giant catfish, we developed an automatic fish recapture system (AFR system). The AFR system causes the free-ranging fish to float at the scheduled time. We have conducted experiments on Mekong giant catfish in the Mae peum reservoir, Thailand. We used 7 cultivated young catfish, whose total length ranged from 76.5 cm to 86.5 cm. After we attached the AFR system to the catfish, we released them into the reservoir in August (one catfish), October (three catfish) and December (three catfish) of 2004. The AFR systems were scheduled to cause the catfish to float after four to eight days. The recovery percentage of both the catfish and the AFR systems was 43 %. The recovery percentage of only the AFR systems was 29 %. The percentage of loss of all the catfish and the AFR systems was 29 %. We also examined the stomach contents of the catfish with a microscope and found some zooplankton and phytoplankton. The total number of the zooplankton in the stomach contents in October was 1288 individuals and the most, and those in August and December were 33 and 34 individuals respectively and least

A review of the Mekong giant catfish tracking project (MCTP) from 2002 to 2004

Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society InfrastructureDecember 13-14, 2005, Siam City Hotel, Bangkok, ThailandFor the conservation and successful stock enhancement of the endangered species Mekong giant catfish Pangasianodon gigas, an understanding of its movement patterns and behavior is indispensable. The Mekong giant catfish tracking project (MCTP) has been begun to measure the movements of hatchery-reared Mekong giant catfish using acoustic telemetry and bio-logging technology in the Mae peum reservoir and Mekong River. Research in the Mae peum reservoir demonstrated that fish showed distinctive diel vertical movement and the swimming depth was limited by the thermocline or dissolved oxygen stratification. Fish also displayed diel horizontal movement between inshore at night and offshore areas during the day. Researchers in the Mekong River presented the first records of upstream and downstream movement of Mekong giant catfish for up to 97 days. Fish swam upstream at a speed of 16.2 km d-1 and downstream at a speed of 7.2 km d-1 during a day. These results will contribute to plans for the species conservation and the effective stock enhancement in reservoirs and fish ponds

Vertical Movements of a Mekong Giant Catfish (Pangasianodon gigas) in Mae Peum Reservoir, Northern Thailand, Monitored by a Multi-Sensor Micro Data Logger

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 falling to 10% saturation at depths lower than 4 m. This specific DO stratification was found to limit the vertical movement of the catfish