In situ target strength of walleye pollock Theragra chalcogramma (Pallas)
		and arabesque greenling Pleurogrammus azonus Jordan et Metz

	Tomonori Kaneta*1, Hiroya Miyake*1, Masami Mizuno*1, Hideo Yoshida*2,
	Ryotaro Ishida*2, Masashi Natsume*3, Kohji Iida*4, and Tohru Mukai*4

*1:Hokkaido Wakkanai Fisheries Experimental Station, Horai, Wakkanai, Hokkaido 097, Japan
*2:Hokkaido Central Fisheries Experimental Station, Yoichi, Hokkaido 046, Japan
*3:Hokkaido Hakodate Fisheries Experimental Station, Yunokawa, Hakodate, Hokkaido 042, Japan
*4:Hokkaido University, Minato, Hakodate, Hokkaido 041, Japan

	In situ target strengths (TS) of walleye pollock and arabesque greenling
were measured using a split beam scientific echo sounder (EK500, 38kHz).
Surveys were conducted in October 1996 and in May 1997 in the area off the
western coast of Hokkaido, Japan. Fishes on echograms were caught through
trawling or angling in order to identify species and to know the
relationship between TS and their body length.
	Results showed the mode of in situ TS distribution of walleye pollock was
-32dB, and the mode of the body length distribution was 39cm. The
normalized target strength, "A", in the formula of TS=20LogL(cm)+A was
calculated, and A=-63.8dB was obtained. On the other hand, the mode of in
situ TS distribution of arabesque greenling showed -47dB, and the mode of
the body length distribution was 29cm, then the normalized TS, A=-76.2dB
was obtained. 
	Comparing these two value of "A", the TS of walleye pollock was obviously
higher than that of arabesque greenling. That's because walleye pollock has
an air bladder but arabesque greenling doesn't have it