Copper pyrithione (CuPT) is an antifouling agent used in paints for vessel hulls as an alternative to TBT. Environmental concentrations of CuPT for 2008. when the AFS treaty will take effect, were estimated using the chemical fate model. In the effects assessment of CuPT. 0.25 μgL^-1 (the 96-h NOEC(No Observed Effect Concentration)of CuPT on Skeletonema costatum) was selected as the critical toxic concentration of CuPT. Risk was determined based on whether the Margin of Exposure (MOE) was equal to or less than an uncertainty factor (UF) of 100. In the case of 3.66% content of CuPT in antifouling paints. MOE at each port or navigation route was equal to or less than the UF value of 100, indicating a significant ecological risk. Similarly, in the case of 1.45% content of CuPT, the MOE at each port
was also equal to or less than the UF. However, the MOE was more than the UF in areas other than ports, indicating that risk is not significant and can be ignored. We also investigated the effectiveness of replacing TBT with alternative agents by comparing the ecological risk of TBT and CuPT. The abnormal calcification of the giant Pacific oyster was selected as the assessment endpoint. A concentration of 0.001 μgL^-1 was used as the NOEC (No Observed Effect Concentration) for TBT with a UF of 1.For CuPT 11 μgL^-1 (96-h EC50) was selected as the critical toxic concentration and a UF value of 10 was selected by the extrapolation of laboratory toxicity data to the field. The MOE of TBT was equal to or less than 1 in the entire Bay (except at the mouth) throughout the year, indicating a high or significant risk of abnormal calcification. The MOE of CuPT was more than 10 in the whole Bay. indicating no risk to the giant Pacific oyster. Our results indicate that ecological risk will be reduced as the TBT in antifouling paints is replaced with CuPT.
We have developed a prototype model that can estimate the concentration of hazardous substance coplanar polychlorinated biphenyls (co-PCBs) in marine organisms and used it to estimate the concentration that target species of a basic and specific food chain had accumulated in Tokyo Bay. This model based on three models: a 3D-hydrodynamic model (Horiguchi et al. 2001). an ecological model (Taguchi et al, 1999) and a chemical fate model (Kobayashi. 2004). The model could reproduce, both temporally and spatially, the actual concentrations of co-PCBs found in fish, of Tokyo Bay.
We compared the depth of horizontal rhizomes of small seagrass species to the depth of dugong feeding trails in seagrass meadows on the southeast coast of Talibong Island. Trang Province. Thailand, from 27 to 30 October 2005. The horizontal rhizomes of Halophila ovalis were within the depth range that was almost completely grazed by dugongs. Halophila ovalis populations in seagrass meadows appear to be maintained by their fast rate of growth. On the other hand, the horizontal rhizomes of Thalassia hemprichii. which has a slower growth rate, were deeper than the dugong grazing depth, thus reducing grazing pressure on T. hemprichii.
It is necessary to develop a numerical model that can be used to assess the toxic impact of decomposition products of chemicals in the marine environment To this end, we developed a chemical fate model for the decomposition products of Tributyltin (TBT) that has been used primarily as an antifouling agent incorporated into antifouling paints for vessel hulls. We used the model to calculate the concentrations of decomposition products of TBT in Tokyo Bay.
The model is based on an existing chemical fate model, which we modified to predict the fate of TBT. Dibutyltin (DBT) and Monobutyltin (MBT). Degradation of each butyltin accumulated in the sediment was a function of temperature of the bottom water. The process of release from sediment was modeled using a partition coefficient for each butyltin. The model was run to reproduce the seasonal variation of TBT, DBT and MBT during the period from January 1971 to December 2004. The model results compared well with field measurements collected in 2004. But. there was a significant discrepancy in the DBT concentration.
Dugong (Dugong dugon) were surveyed using simultaneous visual and acoustical methods in January 2008 in Thailand water. A research boat monitored chirp and trill sounds produced by dugongs using a towed stereo hydrophone array system. Two teams of experienced visual observers conducted standard visual observation on the same boat. Comparing with two independent observations, detection probability of acoustic and visual monitoring could be calculated using Petersen method. The acoustic and visual detection probabilities were 8.7% and 9.3% . respectively.. The detection probability of acoustic monitoring raised up to 18.4% when conspecific chirp call was transmitted from an underwater speaker with the source level at 150 dB rms re luPa. In the mean time, the detection probability of visual observation was calculated as 13.2%. Vocal hot spots with many detection of calls were recognized. Dugong is one of the most difficult marine mammal species to observe visually by ship based survey. Passive acoustic monitoring will aid for the survey since it had similar detection performance with the experienced visual observers. Playback is suggested to increase the detection probability that is beneficial for future field surveys using passive acoustic method to make sure the attendance of dugong in focal area.
Passive acoustic biotelemetry for Dugong dugon enabled us to monitor the presence and the position of dugongs by receiving their calls using underwater sound techniques. The principle of the acoustic biotelemetry is to identify the sound source directions of their calls calculated from the time arrival differences between plural hydrophones. This method requires stereo automatic underwater sound monitoring systems. From 2003 to present, we have been developing the stereo underwater recording system. AUSOMS-D (Automatic Underwater Sound Monitoring System for Dugong). AUSOMS-D records underwater sound of frequency band between 20 Hz to 20 kHz by stereo (2ch) hydrophones at sampling frequency of 44.1 kHz with 16 bits resolution for many days. Progresses of AUSOMS-D have been made such as down sizing of the pressure resistant housing, longer recording time and additional scheduling functions. The latest AUSOMS-D is 7 kg in the air weight. It can record up to 15 days continuously with 16 alkaline D cells. AUSOMS-Dwas applied for the survey of dugong in Thailand's water many times.
On the other hand, we have developed a stereo towed hydrophone system. The system is called ”Towed Aquafeeler”. Towed Aquafeeler can receive underwater sound of frequency band between 100 Hz to 20 kHz by 2ch. Recommended tow speed of the system in listing mode is 6 knots or less. Towed Aquafeeler is 11 kg in the air and neutral buoyancy in the water. It was also used for the dugong surveys in Thailand water twice.
A rather small population, Dugong, its the most northern area of occupation has shared Okinawa's main island sea area with fisheries. Under this situation, the dugong protection project has been carried out by the Fisheries Agency from 2001 to 2007. As a way of searching for dugong straying into fixed net. we found an effective way to judge whether it was a dugong or not by comparing properties of dugong with information of moving objects through a multi-beam sonar. For this searching, we used automatic detector software on the computer. To see how accurate the software is. we confirmed it with ROC analysis. The result was that a software that considers posture properties of moving objects is more right than others that do not. Also in 2007. we done empirical test at Kin bay in Okinawa. In the result, we proved a dugong alarm system holding the software could transmit information of moving objects to a land station. As a step toward the practical use of the detection software, we must look at the characteristics of fixed net in the sea area. In addition, in order for the system architecture to coexist between the dugong and the fisheries, we believe that we should build a system that takes into consideration for the fishery operation. That is to say. a system without harmful effects on fisheries catches.
Dugong calls were collected using a towed stereo hydrophone system around Talibong Island and Muk Island in Thailand in January 2008. Standard visual observation was conducted simultaneously to record the dugong distribution. Total of 223 dugong calls and 80 dugongs were detected. Spatial distribution of both of the acoustical and visual detections were analyzed using IA -index. The spatial distribution of the visual detections showed almost uniform distribution and that of the acoustical observations showed concentrated distribution (Iσ =0.85 and 3.18, respectively). The number of snapping noise per minute was less in the areas where dugong calls were observed (P ＜ 0.001). It was suggested that dugongs vocalized selectively in less noisy areas.
The Fishery Agency conducted the investigations and researches on the restoration of tropical sea grass beds, which serves as feeding sites for dugongs. from FY 2001 to FY 2008. as a part of its project aiming at the coexistence of dugongs and the fishery. In addition to the results of the project, such as seedling production and transplanting techniques, the existing knowledge and information on the sea grass beds were collected and complied in a booklet. The former part of the booklet ” A review for the restoration of tropical sea grass beds” summarizes existing knowledge and information on 1) the component species, functions and roles. 2) habitats and environmental conditions. 3) the distribution area and standing stock and 4) dugongs' biology and the relationship with tropical sea grass beds, while the latter part explains 1) restoration techniques of sea grass beds using hand grass planting. 2) seedling production techniques using Thalassia hemprichii, 3) transplanting techniques of artificially produced Thalassia hemprichii and 4) monitoring of created or restored tropical sea grass beds.
Knowledge of feeding ecology which have been studied on reared and wild dugong are described. So far. 15-20 kg (wet wt)/day has been reported as feeding rate of a dugong in Toba aquarium. And, two estimations of feeding rate on wild dugong by author are introduced. Feeding rate of dugong on Halophila ovalis was estimated based on observation of dugong behavior and feeding trails in Khao Bae Na sesagrass bed. Trang, Thailand, and on long term observation of dugong behavior in New Argao seagrass bed. Davao Gulf. Mindanao. Philippines. From these results, it was discussed the possibility that the knowledge of feeding rates have been published was overestimation. Because the estimation have been published was based upon short-term observation. The feeding rate considerably varied seasonally and monthly. Feeding rate per day obviously fluctuated with lunar cycle. Also the rate increased in dry season and decreased in wet season.