Video Observation System Research Articles

“BLIMP-CAM”: Aerial Video Observations of Marine Animals

Conducting behavioral observations of obligate marine animals such as cetaceans and sirenians is challenging. These animals usually spend prolonged periods beneath the surface of the water out of view of a boat-based or land-based observer. Observations from high vantage points can overcome some of these difficulties by allowing the observer to look down through the water and view subsurface behaviors. I developed a “blimp-cam”: a video camera mounted on a small ovoid-shape, helium-filled aerostat (blimp). This new style of blimp had a number of advantages over previous systems that have used the traditional zeppelin style, including being smaller, cheaper and easier to operate. The “blimp-cam” was flown at a height of 50 m, providing an overhead view of dugongs at water depths of up to 4 m and distances up to 200 m. I used the “blimp-cam” to obtain information on dugong behavior. I assess the advantages of this new style of aerial video observation system, its limitations and potential applications in the marine environment.

Response of dugongs to boat traffic: The risk of disturbance and displacement

Disturbance from boats has been documented for many species of marine mammals, especially cetaceans, but has never been quantified for dugongs. Dugongs depend on seagrass for food. This food mostly occurs in shallow coastal areas where boat traffic is high. Thus there is potential for boats to alienate dugongs from critical habitat areas. Using an overhead video observation system (‘blimp-cam’), we observed the behaviour of focal dugongs during controlled boat pass experiments and while no boats were present. The percentage of time focal dugongs spent feeding and travelling was unaffected by boat presence, the number of boat passes and whether a pass included a stop and restart (pass continuity). The duration, distance and direction of a focal dugong's subsurface behaviour were unaffected by number, continuity or distance of boat passes. However, focal dugongs were less likely to continue feeding if the boat passed within 50 m, than if the boat passed at a greater distance. Mass movements of dugong feeding herds in response to experimental and opportunistically observed boats were timed on 42 occasions but only lasted an average of 122 s. These movements occurred in response to boats passing at a range of speeds, and at distances of less than 50 m to over 500 m. The levels of boat traffic we observed may reduce dugongs' feeding time budget by a maximum of 0.8–6%. Thus at present boats appear unlikely to be having a substantive effect on the energy intake of dugong populations at our study site on the Moreton Banks near Brisbane, Australia. However, boat traffic is likely to increase in this fast growing region, raising concern about the future impact of boats on this and other dugong populations.

Measurement of Bioturbation Rate in Tube-Building Maldanid Worms (Polychaeta: Maldanidae) with a Video Observation System

Measurement of Bioturbation Rate in Tube-Building Maldanid Worms (Polychaeta: Maldanidae) with a Video Observation System

ヒラメ人工種苗放流技術の開発に関する基礎的研究 Ｖ ヒラメ天然稚魚の摂食行動および被食に及ぼす飢餓の影響

Feeding behavior of wild Japanese flounder juvenile with progress in starvation was examined to determine whether starvation could increase vulnerability of wild flounder to predation. Laboratory experiments were conducted using a video observation system to analyze feeding behavior of juvenile flounder such as time of swimming to water column, swimming course and number of attacks in a feeding behavior under starvation up to 7 days. Experiments showed that longer starved juveniles spent a longer time in the water column and returned farther from the initial position. The number of attacks in a feeding behavior increased in a few days after onset of starvation. Fed juvenile flounders were not preyed upon by 1-or 2-year-old flounders, while 3 to 7 days starved juveniles were preyed upon in the laboratory experiment. These findings suggest that wild juvenile flounder change feeding behavior toward more vulnerability to predators with progress in starvation primarily due to longer exposure in the water column and frequent changes of landing position. These changes in feeding behavior found in the laboratory suggest that high mortality of juveniles would occur associated with seasonal reduction in prey mysid abundance in their nursery ground.