New steps in bio-logging science

Among a variety of remote observation systems for the study of marine creatures, data loggers emerged in the 1990\u27s, following mechanical depth recorders (TDRs). Digital data loggers have played a critical role in studies on marine animal behaviour, ecology and physiology. Today, this field is called bio-logging science. Digitalization has allowed further miniaturization of logger systems, which is particularly important to this science so that the effect of device attachment to animals is minimized. At the same time digital techniques have enabled us to develop multi-sensor loggers, which has enhanced integration of information on many aspects of marine animal lives. Using advanced systems we are now able to determine when feeding occurs during dives, elucidate stroking patterns, 3-dimensional dive paths and even prey distribution along the dive path. This article traces the history of development of both mechanical and digital loggers developed at and used by the researchers of the National Institute of Polar Research, Japan

Preliminary report of swimming behavior and the response to temperature of lacustrine masu salmon, Oncorhynchus masou Brevoort, monitored by data logger during the spawning migration in Lake Toya

Swimming depth and ambient water temperature of male masu salmon (Oncorhynchus masou Brevoort) during the spawning migration in Lake Toya was examined using a micro data logger. Soon after release, the fish swam along the coast and mean swimming depth and water temperature were 14.2±7.96m and 13.8±3.80℃. Then, the fish swam into a stream where mean swimming depth and water temperature were 1.6±3.28m and 18.3±1.58℃. The fish returned to the lake again where mean swimming depth and water temperature were 33.4±14.1m and 5.5±1.45℃. Finally, the fish swam into a stream again and stopped any vertical movements. The results show that the fish swam in coastal waters at a higher water temperature despite the likely higher energy expenditure and swam in deep, cooler water to recover between two upstream migration attempts. We hypothesize that temperature is not an important parameter for upstream migration and probably navigational mechanisms and hormonal motivation for spawning have affeted ambient temperature selection in lacustrine masu salmon during the spawning migration

Population changes of Ad_lie and emperor penguins along the Prince Olav Coast and on the Riiser-Larsen Peninsula

The trends of penguin populations are thought to be reliable indicators of ecosystem changes in the Southern Ocean. There are seven Ad_lie penguin colonies and one emperor penguin colony along the Prince Olav Coast and one emperor penguin colony on the Riiser-Larsen Peninsula. We compiled and analyzed the available data collected by airborne and ground census between 1971 and 2000 in order to determine the breeding status of penguins in this area. Ad_lie penguin populations increased at two colonies; no apparent trends were observed at other colonies. Emperor penguin populations were high in the mid-1990s and suddenly decreased in 2000. Populations need to be carefully monitored in the coming years

Analysis of diving behavior of Adelie penguins using acceleration data logger

Acceleration data loggers were attached to five adult Adelie penguins at Hukuro Cove, Lutzow-Holm Bay in austral summer 1997/1998. The loggers recorded time series data of speed, depth, surging acceleration and swaying acceleration in flush memories inside. From time series analyses, the frequency of 2- to 3-Hz was found in the surging acceleration during descent in a straight line. The cycle seemed to correspond to wingbeat frequency of the Adelie penguin. The relation between wingbeat frequency and diving depth was that the frequency ranged from 1.5-Hz to 3.0-Hz when the penguins dive in water shallower than 30-m and was over 2.5-Hz in water deeper than 50-m. The acceleration data logger is a powerful tool to estimate kinematic parameters of free-range marine animals

Meteorological factors affecting the number of Weddell seals hauling-out on the ice during the molting season at Syowa Station, East Antarctica

Weddell seals show a clear diurnal haul-out pattern, while there have been few studies focusing on the influence of weather conditions. The present study investigates the relationship between the number of seals which haul-out on the fast ice and meteorological factors such as: air temperature, wind speed, humidity and irradiance in Syowa Station, East Antarctica. The number of seals was inversely related to wind speed (P -8.3 °C), indicating that some other factors might influence the seal\u27s decision to stay in the water

Preliminary study on heartbeats and swimming behavior of free-ranging fish, red sea bream Pagrus major, measured with newly developed micro data-logger

To estimate the physiological condition or metabolic rate simultaneously with swimming behavior, we recorded a continuous electrocardiogram (ECG) in freely swimming fish, red sea bream Pagrus major, in a net pen during a 24h period. Swimming speed, swimming depth, and the bioelectric potential of the heart in the test fish were recorded with a micro data-logger. It is difficult to eliminate electric noise while recording ECGs of actively swimming fish. In the present experiment, we attached electrodes to two points on the ventral surface and successfully obtained data. Two types of micro data-loggers (one for recording ECG and another for swimming speed and depth) were attached to the dorsal side of the fish. The red sea bream swam slowly ( <1 total length/s) and stayed deeper in the net pen during most of the day, except for frequent burst of speed and vertical movements around dawn. An analysis of heartbeat variability, showed that high-frequency components, representing vagal (parasympathetic) nerve activity, rose only around midnight

Preliminary report of new method for ECG measurement of exercising birds

To measure the heart rate of diving seabirds, we tested a new method of attaching electrodes and a miniaturized ECG logger with high memory capacity (2 Mbytes) and high frequent sampling (5ms). A needle type electrode was inserted into subcutaneous tissue of Adelie penguins, and an electrode was implanted under the sternum of hens. Both electrodes were connected to a logger attached to the back of the bird. The mean±SD of heart rate of penguins for 3 h and of hens for 1 h during a resting period were 74.9±15.4 bpm and 245.3±12.1 bpm, respectively. The ECG showed electric noise during exercising periods. However, as R peaks were countable in those periods, it was possible to calculate the heart rate during exercising periods from the interval between R peaks. Though the implantation method needs some recovery time for birds after surgery before the ECG measurement, the method reduces the electric noise caused by the locomotor muscle and electrode movement and is suitable to measure the ECG of free-ranging seabirds during dives

Oxygen minimum zone: An important oceanographic habitat for deep-diving northern elephant seals, Mirounga angustirostris.

Little is known about the foraging behavior of top predators in the deep mesopelagic ocean. Elephant seals dive to the deep biota-poor oxygen minimum zone (OMZ) (&gt;800&nbsp;m depth) despite high diving costs in terms of energy and time, but how they successfully forage in the OMZ remains largely unknown. Assessment of their feeding rate is the key to understanding their foraging behavior, but this has been challenging. Here, we assessed the feeding rate of 14 female northern elephant seals determined by jaw motion events (JME) and dive cycle time to examine how feeding rates varied with dive depth, particularly in the OMZ. We also obtained video footage from seal-mounted videos to understand their feeding in the OMZ. While the diel vertical migration pattern was apparent for most depths of the JME, some very deep dives, beyond the normal diel depth ranges, occurred episodically during daylight hours. The midmesopelagic zone was the main foraging zone for all seals. Larger seals tended to show smaller numbers of JME and lower feeding rates than smaller seals during migration, suggesting that larger seals tended to feed on larger prey to satisfy their metabolic needs. Larger seals also dived frequently to the deep OMZ, possibly because of a greater diving ability than smaller seals, suggesting their dependency on food in the deeper depth zones. Video observations showed that seals encountered the rarely reported ragfish (Icosteus aenigmaticus) in the depths of the OMZ, which failed to show an escape response from the seals, suggesting that low oxygen concentrations might reduce prey mobility. Less mobile prey in OMZ would enhance the efficiency of foraging in this zone, especially for large seals that can dive deeper and longer. We suggest that the OMZ plays an important role in structuring the mesopelagic ecosystem and for the survival and evolution of elephant seals