Nesting and post-nesting studies of loggerhead turtles (Caretta caretta) at Omaezaki, Japan

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, ThailandNesting biology, measurement of body size and mitochondrial (mt) DNA haplotypes of loggerhead turtle, Caretta caretta at Omaezaki Beach, Japan were investigated by collecting data and samples during night observations from 6 July to 6 August 2004. In addition, seven post-nesting females, which nested during this observation period, were tracked by satellite telemetry. A total of 33 females were identified in this observation period. Seven females nested twice, with a mean inter-nesting interval of 18.0 days. Even though our observations did not cover the entire nesting beach and period, the frequency of nesting was estimated at three, using a calculation based on the total number of nests at this beach in this nesting season. The range of straight carapace length (SCL) was from 65.8 to 91.6 cm, and the mean (±SD) size was 81.5±5.83 cm. The SCL of females at Omaezaki Beach is significantly lower than at other nesting sites in Japan based on calculation of 90% confidence intervals for mean SCLs. Two haplotypes were detected among 33 females using mitochondrial (mt) DNA analysis. Composition of these two haplotypes of nesting females at Omaezaki Beach was similar to nesting females at other nesting beaches in Japan. Post-nesting feeding grounds of seven loggerhead turtles released from Omaezaki consist of two areas, the northwestern North Pacific and the East China Sea. It is confirmed that nesting females at Omaezaki Beach were from the two groups using the different post-nesting feeding grounds and these two groups can be distinguished by their body size criterion of 85 cm. If different factors impact females in each feeding ground, monitoring the number of females and the composition of body size can be useful in assessing the impact to females

Computational investigation of prolonged airborne dispersion of novel coronavirus-laden droplets

We have performed highly accurate numerical simulations to investigate prolonged dispersion of novel coronavirus-laden droplets in classroom air. Approximately 10,900 virus-laden droplets were released into the air by a teacher coughing and tracked for 90 min by numerical simulations. The teacher was standing in front of multiple students in a classroom. To estimate viral transmission to the students, we considered the features of the novel coronavirus, such as the virus half-life. The simulation results revealed that there was a high risk of prolonged airborne transmission of virus-laden droplets when the outlet flow of the classroom ventilation was low (i.e., 4.3 and 8.6 cm/s). The rates of remaining airborne virus-laden droplets produced by the teacher coughing were 40% and 15% after 45 and 90 min, respectively. The results revealed that students can avoid exposure to the virus-laden droplets by keeping a large distance from the teacher (5.5 m), which is more than two times farther than the currently suggested social distancing rules. The results of this study provide guidelines to set a new protection plan in the classroom to prevent airborne transmission of virus-laden droplets to students

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

Assessment of mitigation measures to reduce interactions between sea turtles and longline fishery

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, ThailandSea turtles have been receiving negative impacts from both human activities and natural factors. Interactions with commercial fisheries are one of the anthropogenic factors affecting sea turtle populations. A variety of mitigation measures have been developed and tested to reduce incidental mortality of sea turtles in longline fishery. We review potential technical measures to alleviate longline-sea turtle interactions and show some preliminary results from our field and laboratory experiments. Fishing gear modifications aim at reducing hooking rates of sea turtles by changing fishing hooks and baits or by the use of additional devices. Results of our field experiments showed that the use of circle hooks altered hooking position and reduced deep hooking of sea turtles. Fish baits showed lower catch rates of sea turtles than squid baits, because sea turtles were more likely to swallow the whole squid bait due to tough and flexible muscle texture of squids. Fishing practice modifications aim at avoiding the overlap between fishing operations and sea turtles either spatially or temporally. In the oceanic area, sea turtles spend most of their time within the shallow surface layer (<40m). Deep-setting longline is effective to avoid incidental capture of sea turtles. Sea turtles have habitat preference for warm water, and migratory species seem to have distinct routes for long-distance migration. Biotelemetry studies play a important role because they provide baseline information on habitat utilization, diving profile, activity pattern, and migratory paths of sea turtles Careful handling and live release is another way to reduce post-hooking mortality of sea turtles because many sea turtles captured in shallow longline are retrieved alive. Several instruments have been developed to haul sea turtles onboard and to remove fishing hooks and lines. Results of our captive experiments indicated that hooked sea turtles survived for a prolonged period and discharged fishing hooks out of the body. Since these mitigation techniques affect the fishing efficiency of target species, we should also assess the economic feasibility of each method to establish a practical way of solution

MANAGEMENT OF LONGLINE FISHERY TO MITIGATE INTERACTIONS WITH ECOLOGICALLY RELATED SPECIES

Southeast Asia Sea Turtle Associative ResearchBangkok, Thailand, 16-19 December 2002Longline fishery has been regarded as an environmentally friendly fishing method. However, recently, there is a growing concern over the impact of longline fishing on untargeted marine species. Sharks are often claimed to be susceptible to heavy fishing pressure judging from their large body size and low fecundity. But our analysis of fishing data indicated that catch rates of pelagic shark species showed no signs of decrease and that their stocks were in sound condition. Further stock assessment of sharks and management of longline fishery are important to solve the shark problem. Large scavenging seabirds, mostly albatrosses and petrels, are incidentally taken in tuna longline fishery at the sea surface near fishing vessels. Since introduction of mitigation measures to the limited risky zone around the operating fishing vessels can effectively reduce incidental catches of seabirds, Japan has been making efforts to develop mitigation measures and to promote their prevalent use. Sea turtles are also taken incidentally in longline fishery and the impacts of incidental catch have been claimed as a cause of decline in some populations. However, comprehensive management of marine and terrestrial environment is indispensable for the conservation of sea turtles because various factors are affecting them other than fisheries. Japan made a proposal to implement a plan of action for the conservation of sea turtles at FAO-COFI in 2001. Although the proposal was not accepted, research and development have been initiated in Japan for the solution of sea turtle issue. Since information is still deficient for many sea turtle populations in Asia, international co-operation of Asian countries for research and management is very important for the sustainable co-existence of sea turtles and human activitie

Quantitative estimation of the ecosystem services supporting the growth of Japanese chum salmon

Chum salmon (Oncorhynchus keta) are distributed widely in the subarctic North Pacific. The Japanese stock is maintained by artificial release procedures. Chum salmon, including the Japanese stock, provide important ecosystem services for humans that are related to provisioning, culture and support. These ecosystem services are supported by the supply of prey and habitat that the fish use. We regard the supply of prey and habitat as supporting services for salmon. We developed a procedure to estimate supporting services quantitatively, based on the prey biomass consumed by individual salmon, by coupling a bioenergetics model and a lower trophic level ecosystem model. Using this procedure, we estimated the prey biomass consumed by a cohort of Japanese chum salmon released in a single year. The phytoplankton biomass indirectly consumed by a cohort was also estimated and considered to be the primary production supporting the fish. The Japanese chum salmon cohort was estimated to consume ca. 4.2-4.7 x 10(9) kg wet weight of zooplankton, of which more than half is eaten in the Bering Sea. The Japanese chum salmon cohort is supported by an estimated primary production of 2.0-2.2 x 10(9) kg C, which amounts to 0.17%-0.19% of primary production in the areas and periods through which the fish migrate. We also attempted to calculate the monetary value of supporting services for the growth of Japanese chum salmon