EFFECT OF DEPTH-DEPENDENT TARGET STRENGTH ON BIOMASS ESTIMATION OF JAPANESE ANCHOVY

Authors

Hiroto Murase, The Institute of Cetacean Research, 4-5 Toyomi-cho, Chuo-ku, Tokyo 104- 0055, Japan.Follow
Atsushi Kawabata, National Research Institute of Fisheries Science, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan.
Hiroshi Kubota, National Research Institute of Fisheries Science, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan.
Masayasu Nakagami, Hachinohe Branch, Tohoku National Fisheries Research Institute, 25-259 Shimo-mekurakubo, Hachinohe-shi, Aomori 031-0841, Japan.
Kazuo Amakasu, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato, Tokyo 108-8477, Japan.
Koki Abe, National Research Institute of Fisheries Engineering, 7620-7 Hasaki, Kamisu, Ibaraki 314-0408, Japan.
Kazushi Miyashita, Field Science Center for the Northern Biosphere, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan.
Yoshioki Oozeki, The Institute of Cetacean Research, 4-5 Toyomi-cho, Chuo-ku, Tokyo 104- 0055, Japan.

Abstract

Effect of the depth-dependent target strength (TS) on biomass estimation of Japanese ahcovy was examined by using following four TS models: (1) TS = 20logLt-71.9, (2) TS = 20logLt-72.5, (3) TS = 20logLt-(20/3)log(1+z/10)-67.6 and (4) TS = 20logLt-(20/3)log(1+z/10)-64.7, where Lt and z represent total length (cm) and depth (m), respectively. (1) and (2) have been used in conventional fisheries resources surveys; (3) and (4) take account of depth-dependent TS. Because (1)-(3) were based on in-situ measurement, pitch angles of individuals used in the models were not known. Pitch angle is assumed 0° (±10° std) in (4). Biomass estimated by (3) was 82% and 73% of (1) and (2), respectively. Biomass estimated by (3) was 195% of (4). The results indicated that the effect of the pitch angle on the biomass estimation could be large even if the effect of the depth-dependent TS was taken account. Mean distribution depth can be used as a value for z.

Recommended Citation

Murase, Hiroto; Kawabata, Atsushi; Kubota, Hiroshi; Nakagami, Masayasu; Amakasu, Kazuo; Abe, Koki; Miyashita, Kazushi; and Oozeki, Yoshioki (2011) "EFFECT OF DEPTH-DEPENDENT TARGET STRENGTH ON BIOMASS ESTIMATION OF JAPANESE ANCHOVY," Journal of Marine Science and Technology: Vol. 19: Iss. 3, Article 5.
DOI: 10.51400/2709-6998.2191
Available at: https://jmstt.ntou.edu.tw/journal/vol19/iss3/5