The effect of Chattonella exposure on the acid-base status of the yellowtail Seriola quinqueradiata was analyzed to assess the validity of the hypothesized mechanism of fish kill by this plankton species. Based on the finding that gill carbonic anhydrase was inactivated in fish exposed to Chattonella, it was hypothesized that this inactivation resulted in certain physiological disorders such as decreases in blood pH and Po2. None of the acid-base variables measured in this study (arterial blood pH (pHe), red blood cell intracellular pH (pHi), Pco2 (Paco2), and total CO2 of plasma (Taco2p)) varied substantially from their control values after the onset of exposure except for some increases in pHi. It was only the terminal blood samples that demonstrated sharp decreases in pHe and pHi and elevation of Paco2. In contrast, arterial Po2 decreased rapidly after the onset of plankton exposure. Overall these results do not support the above hypothesis.
From March 2005 to March 2006, the presence of the finless porpoise Neophocaena phocaenoides in the Kanmon Strait, Japan was monitored using a stationary acoustic event recording device. A stereo acoustic event recorder (A-tag) recorded biosonar signals as well as sound source directions, which can be used to count the number of echolocating porpoises within a distance of 126 m. During 75 days of effective observation, 37 porpoises were detected acoustically. On average, one individual was detected every two days. Most of the finless porpoises appeared at night, and no porpoises were observed from 12:00 to 18:00 hours. Shipping traffic observed using the same acoustic system showed trends opposite to that of finless porpoise during the daytime. The tidal current did not affect the presence of the animals (up to 5.2 knots). However, porpoises were suggested to swim along the current direction. Finless porpoises appeared to be isolated and used relatively long-range sonar during the observations, suggesting that the porpoises passed through the Kanmon Strait rather than searched for prey.
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