Department of Fisheries Science and Technology, Yosu National University Challanam, KOREA

djhwang@yosu.ac.kr

　

"Hydroacoustics", a fishing device used in the Korean fisheries science field, started in 1960. The National Fisheries University of Pusan began researching how to estimate biomass through acoustics in 1980. At that time, their fundamental experiments were on determining "target strength", or the characteristics of the individual fish and frequency. More recently, however, the research on fisheries acoustics was carried out at two institutes and six universities in Korea. Most of the research on estimation of fisheries resource using the scientific echosounder was conducted at the NFRDI (National Fisheries and Development Institute) and KORDI (Korea Ocean Research and Development Institute). The NFRDI by means of trawl and hydroacoustic surveys investigated coastal and offshore resources, the Polar Research Center of KORDI used acoustics to research the Utilization of Antarctic Marine Living Resources, and the six universities conducted more comprehensive research. Pukyong National University, for example, studied the accurate measurement of target strength, investigated the demersal fisheries resources of the East China Sea, developed the underwater telemetry system to monitor the behavior of fish, designed broadband ultrasonic transducers for fish species identification and fish tracking with a split beam echosounder and so on. Yosu National University studied the measurement of target strength for commercial fish (such as anchovy and mackerel), investigated bottom trawl, conducted an acoustic survey of the Yellow and East China Sea, and sought to improve bottom detection of demersal fish. Cheju National University, Gyeongsang National University. Kunsan National University and Gangwon Provincial University all studied the measurement of target strength of common fish and investigated the fisheries resources in coastal areas. This is an overview of the present state of research of fisheries resource using "hydroacoustics" in Korea.

　

　

¹Graduate School of Fisheries Sciences, Hokkaido University Hakodate, JAPAN

kawabe@fish.hokudai.ac.jp

　

²National Institute of Polar Research Itabashi, Tokyo, JAPAN

　

During recent years, the study of the migration of fishes, and that of flatfish, has been made possible by the development of new technologies resulting principally from miniaturization of electronic devices. Determination of the location and depth of flatfish has been possible using acoustic telemetry, and provided useful data about the swimming behaviour and orientation in the open sea. However, to be able to measure energetic cost of the migration, it is important to know, not only where the fish are, but also the activity of the fish on its route. We describe a new motion detector ('acceleration data logger'), based on the measurement of acceleration, which we used on Japanese flounder Paralichthys olivaceus which resolves activity to within every seconds, stores information of behaviour and additionally provides information the time allocation of free-ranging flatfish. To show the potential of this new technique, we compare the behaviour of Japanese flounder during swimming periods in daytime and nighttime.

　

The acceleration profiles for specific types of behaviour were categorized during a calibration experiment conducted four captive flounder in the aquarium. Flounder equipped with an acceleration data logger recorded using a video camera, and were compared by visual analysis of videotapes. Field study was conducted off the coast of Tsugaru channel in the southern part of Hokkaido, Japan.

　

Laboratory experiments indicated that the acceleration data logger is effective in accurately tailbeat activity of free-swimming flatfish. Owing to acceleration profiles, we could determine four behavior patterns as 'active' (beating and burying) or 'inactive' (gliding and lying on the bottom) in flatfish. Two flounder attached on the acceleration data logger were retrieved. The proportion of time spent gliding during swimming periods was greater for flounders in nighttime (23.3%) than for those in daytime (14.5%), whereas the proportion of time spent beating was greater for flounders in daytime (88.6%) than for those in nighttime (76.8%). Acceleration data logger appears to be a useful and reliable device for accurately recording the tail beat of freely swimming flatfish and for estimating the activity of flatfish.

　

　

National Institute of Polar Research Itabashi, Tokyo, JAPAN

naito@nipr.ac.jp

　

Nowadays, although our knowledge on the marine animals is generally increasing, their living feature in the sea is still unknown hidden by huge mass of water. Our limited knowledge on their life makes it difficult to understand their ecological role in the sea and environmental effect on them. However we still do not have proper tools to precisely monitor animal migration movement or foraging behavior for example. Thus study on the free-living animals in the sea is a new challenge in the 21^st century. To study the life in the sea, we investigated the method of research that is able to detect, measure and record simultaneously their behavior, ecology and physiology and their surrounding environment. We applied the techniques of data logging system by attaching miniaturized data logger, so called as micro data-logger, on the animal body. We have developed several types of micro data-loggers which are able to measure swim depth, ambient temperature, swim speed, light level, 2 axis of acceleration, 3 axis of geomagnetic field, ECG and visual image. The size was ranged from 15×45 mm to 20×1110 mm. Using these micro data loggers we conducted the field experiments and successfully obtained data from fish, sea turtles, marine birds and marine mammals.

　

　

National Research Institute of Fisheries Engineering, Fisheries Research Agency Kashima, JAPAN

ksawada@fra.affrc.go.jp

　

Fish length information is important from the viewpoint of fish stock survey and also from that of commercial fishing. Fish behavior is one of the clues to species identification. Echo trace analysis combined with the split-beam method can be a powerful tool that can analyze a fish length and such behavior as swimming velocity of an individual fish. We developed a compact-sized split-beam echo sounding system which includes a software package to estimate length and behavior of an individual fish. After the evaluation in an indoor tank, this system was deployed at sea to compare the estimated fish length and the actual one. The echo sounding system had been tethered from an anchored ship during experiments. Fish sampling by hook and line was conducted to confirm the fish species and its length distribution. Recorded data was once stored in a system and up linked to the computer on the ship through an Ethernet cable. Fish length distribution and fish swimming speed were estimated using the echo trace analysis method. From the fishing results, 79% of the total catch was either Japanese mackerel (Scomber japonicus) or horse mackerel (Trachurus japonicus) with average fork length (FL) of 27.9 centimeters. Estimated fish length distribution coincides well with the distribution obtained from the fish sampling. Estimated swimming speed was 0-1.2 m/s and corresponds to 0-4.3 times as long as the average FL per second. These results show the validity of the echo trace analysis method.

　

　

¹University of Victoria, Department of Electrical and Computer Engineering Victoria, B.C., CANADA

adam@ece.uvic.ca

　

²Pacific Biological Station Nanaimo, B.C., CANADA

　

A typical echosounder used in fisheries applications consists of a single narrow beam transducer that is mounted on the hull of a vessel. Acoustic pulses (pings) are transmitted at a fixed rate and the echoes from various targets in the water column and from the bottom are conveniently displayed as an echogram. Its horizontal axis maps time or distance steamed while its vertical axis displays depth. Color is used to indicate the intensity of the received echo after suitable corrections. The echogram provides information on single or multiple targets in the water column such as individual fish or fish schools and on the bottom.

　

Vessel heave, roll, pitch and yaw have adverse effects on the echogram. Heave will appear as a vertical offset on the features shown in the echogram, and roll and pitch will affect the intensity. The degree of these distortions depends on vessel speed and motions, target structure and trajectory, ping rate and beam-pattern.

　

We will evaluate these effects for different scenarios that are taken from actual measurements of vessel motion. This is accomplished by synthesizing echograms for different situations. Methods to minimize these effects will be discussed. In particular we will model a new non-uniform vertical transmission approach that attempts to minimize the effects of roll and pitch by synchronizing transmission with near vertical transducer orientations.