Quantitative estimation of the predation of marine ranched striped jack <Emphasis Type="Italic">Pseudocaranx dentex</Emphasis> by herons |
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| Authors: | Harunao Nibe Naoki Suzuki Kazutaka Sakiyama Shinsuke Morioka Atsushi Ohno |
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| Institution: | (1) Kagoshima Prefecture Fisheries Promotion Division, Kagoshima Kagoshima, 890-8577, Japan;(2) Department of Ocean Sciences, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan;(3) Stock Enhancement and Management Division, National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, Onomichi Hiroshima, 722-0061, Japan;(4) Fisheries Division, Japan International Research Center for Agricultural Sciences, Tsukuba Ibaraki, 305-8686, Japan;(5) INTEM Consulting Inc., Shinjyuku, Tokyo 160-0023, Japan; |
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| Abstract: | The Goto station of the Japan Sea-Farming Association conducted marine ranching experiments with striped jack Pseudocaranx dentex from 1988 to 1999 in the Goto Islands, Nagasaki, Japan. Marine ranching is a stocking method where released fish are fed
for some period after release in order to decrease initial mortality from starvation. Ranched fish were fed for 0, 90, and
15 days after stocking in 1997, 1998, and 1999, respectively. During the experiment, herons (grey heron Ardea cinerea, black-crowned night heron Nycticorax nycticorax, and great egret Egretta alba) were often observed preying on released fish in the ranching area. The present study estimated the number of fish preyed
upon by herons during observation periods in 1997, 1998, and 1999 from the number of herons that flew into the ranching area
and the predation rate on ranched fish by herons. The former was counted during sightings. The latter was estimated from the
sighting observations and heron regurgitations. The number of herons that flew into the ranching area increased with the feeding
period. The numbers of fish lost to predation by herons in 1997, 1998, and 1999 were estimated to be 0, 5,741, and 829, respectively. |
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