Hobart, Australia
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Lu H.-J.,National Taiwan Ocean University | Kang M.,Myriax Software Pty Ltd | Huang H.-H.,National Taiwan Ocean University | Lai C.-C.,Taiwan Fishery Research Institute | Wu L.-J.,Taiwan Fishery Research Institute
Fisheries Science | Year: 2011

To provide target strength (TS) information for estimating the body length of yellowfin tuna Thunnus albacares and its abundance around fish aggregating devices, TS was measured ex situ and in situ. In the ex situ TS measurements, two cameras synchronized with a 200 kHz echosounder were used to obtain the precise orientation of the yellowfin tuna under free swimming conditions. The ex situ TS (dB re 1 m 2)-fork length (FL, cm) regression was: TS = 27.06 log (FL) - 85.04. Ex situ TS was found to reach its maximum in the tilt angle range of -15° to -20° after excluding TS samples with insignificant correlation to the tilt angle. The angle between the vertebra and the swim bladder was approximately 25° according to X-ray images, supporting the above tilt range. The relationship between the swim bladder volume (V SB, ml) and the fork length was: V SB = 0.000213 FL 3. The results from the in situ TS measurements indicated that the tilt angle was highly concentrated between -10° and 15°. The results from a calculation using the ex situ TS-FL equation with the fork length from biological sampling agreed strongly with the average in situ TS. © 2011 The Japanese Society of Fisheries Science.

Kanga M.,Myriax Software Pty Ltd | Nakamura T.,National Fisheries University | Hamano A.,National Fisheries University
New Zealand Journal of Marine and Freshwater Research | Year: 2012

We demonstrated a tool for visualising multi-dimensional datasets, using an example of fish schools around artificial reefs off the coast of Shimonoseki, Yamaguchi prefecture, Japan. The datasets included acoustic surveys of fish schools, water temperature data, descriptions of the artificial reefs, sediment data, and bathymetry and coastal line data. These datasets were integrated into geographic information system software, which can be used to describe the relationship between water temperature and fish schools; fish schools associated with reefs; and the status of the artificial reefs on the classified seabed. This new tool provides a better understanding of the distribution of fish schools based on their spatial location in context with environmental information around artificial reefs. © 2012 The Royal Society of New Zealand.

Kang M.,Myriax Software Pty. Ltd. | Nakamura T.,National Fisheries University | Hamano A.,National Fisheries University
ICES Journal of Marine Science | Year: 2011

A methodology is introduced for understanding fish-school characteristics around artificial reefs and for obtaining the quantitative relationship between geospatial datasets related to artificial-reef environments using a new geographic information system application. To describe the characteristics of fish schools (energetic, positional, morphological characteristics and dB difference range), acoustic data from two artificial reefs located off the coast of Shimonoseki, Yamaguchi prefecture, Japan, were used. To demonstrate the methodology of the geospatial analysis, diverse datasets on artificial reefs, such as fish-school characteristics, marine-environmental information from a conductivity, temperature, and depth sensor, information on artificial reefs, seabed geographic information, and sediment information around the reefs, were utilized. The habitat preference of fish schools was demonstrated quantitatively. The acoustic density of fish schools is described with respect to the closest distance from reefs and the preferred reef depths, the relationship between fish schools and environmental information was visualized in three dimensions, and the current condition of the reefs and their connection to seabed type is represented. This geospatial method of analysis can provide a better way of comprehensively understanding the circumstances around artificial-reef environments. © 2011 International Council for the Exploration of the Sea.

Tan X.,Pearl River Fishery Research Institute | Kang M.,Myriax Software Pty Ltd | Tao J.,Chinese Academy of Sciences | Li X.,Pearl River Fishery Research Institute | Huang D.,Chinese Academy of Sciences
Fisheries Science | Year: 2011

Hydroacoustic surveys were conducted to understand the relationship between fish density, spatial distribution, and behavior upstream and downstream of the Changzhou Dam on the Pearl River, China, and the condition (open/closed) of the spillways. When the spillways were open on 24 June 2010, numerous fish were observed to be densely distributed in the forebay upstream of the dam, with an average fish density was 0.22 fish m-3. When the spillways were closed on 25 June 2010, the fish upstream of the dam dispersed, and the average fish density decreased to 0.007 fish m-3. Prior to operating the spillways on 24 May 2010, the average fish density downstream of the dam was 0.28 fish m-3; in comparison, on 26 June, immediately following closure of the spillways, the average fish density downstream of the dam was 0. 08 fish m-3. Fish were more active on June 24 than on 25 June: they swam faster and their positions in the water column varied greatly. On 26 June, fish did not to swim as freely in the water column as those measured on 24 May. Based on these observations, we conclude that a large number of fish are able to swim to the upstream side of the dam while the spillways are open. © 2011 The Japanese Society of Fisheries Science.

Dunlop E.S.,Ontario Ministry of Natural Resources | Milne S.W.,Milne Technologies | Ridgway M.S.,Ontario Ministry of Natural Resources | Condiotty J.,Kongsberg Simrad United States | Higginbottom I.,Myriax Software Pty Ltd
Transactions of the American Fisheries Society | Year: 2010

Multibeam echo sounder systems allow the in situ observation of swimming and foraging behavior and give insights into the ecology of fish at the individual level. In Lake Opeongo, Ontario, 16 adult lake trout Salvelinus namaycush were surgically implanted with ultrasonic tags, released, and studied by means of mobile fisheries acoustics. The transmitted pulses from the ultrasonic tags could be detected and displayed within the multibeam echogram in real time. Tagged lake trout were relocated on 131 occasions over 12 d, for a total of 11.7 h of echogram observations. From these events we observed and quantified the spatial relationships of individual lake trout to other fish targets, schools of cisco Coregonus artedi, and the surrounding habitat. We found that all but one tagged lake trout spent at least a portion of their time close to the lake's bottom, but interestingly, many made rapid vertical swimming movements into the water column. These burst vertical movements were sometimes targeted at schools of cisco, such attacks always occurring from below the schools. During such interactions, the lake trout showed distinct peaks in swimming speed when they were between 2.4 and 6.4 m from the schools; we interpret this as the range of their reactive distance in the field. Some of the lake trout were also found to travel alongside of or to actively swim toward other fish targets, whereas others were more solitary. This type of information, made possible by the integration of fisheries acoustics and biotelemetry technology, gives us a fuller understanding of the ecology of aquatic predators and their prey and provides the direct measurements needed to quantify the bioenergetics of lake trout in their natural environment. © Copyright by the American Fisheries Society 2010.

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