scholarly journals Effects of physical factors on the vertical distribution of larval walleye pollock Theragra chalcogramma under controlled laboratory conditions

1990 ◽  
Vol 63 ◽  
pp. 105-112 ◽  
Author(s):  
BL Olla ◽  
MW Davis
Keyword(s):  
Vertical Distribution ◽  
Walleye Pollock ◽  
Theragra Chalcogramma ◽  
Physical Factors ◽  
Laboratory Conditions ◽  
Walleye Pollock Theragra Chalcogramma ◽  
The Vertical Distribution

scholarly journals The influence of ontogeny, physiology, and behaviour on the target strength of walleye pollock (Theragra chalcogramma)

2003 ◽  
Vol 60 (5) ◽  
pp. 1063-1074 ◽  
Author(s):  
John K Horne
Keyword(s):  
Adult Life ◽  
Dorsal Surface ◽  
Walleye Pollock ◽  
Target Strength ◽  
Theragra Chalcogramma ◽  
Physical Factors ◽  
Biological Factors ◽  
Factors Associated ◽  
Surface Areas ◽  
Walleye Pollock Theragra Chalcogramma

Abstract Variability in echo intensities from aquatic organisms is caused by physical factors associated with the transmission of sound through water, and by biological factors associated with the ontogeny, physiology, and behaviour of targets. Acoustic-based density estimates depend on accurately characterizing reflected or backscattered sound from any species of interest. Digitized lateral and dorsal radiographs of walleye pollock (Theragra chalcogramma) were used to characterize intra-specific variability among young-of-the-year, juvenile, and adult life-history stages. Kirchhoff-ray mode (KRM) models were used to quantify variability in backscatter intensities at 38 and 120 kHz. At these geometric scattering frequencies, swimbladder surface areas influence echo intensities. Dorsal swimbladder surface areas were proportionate to fish lengths and decreased after fish were fed. Corresponding changes in backscatter were not proportionate to the reduction in dorsal surface area. The ratio of dorsal to lateral swimbladder surface areas was consistent among gravid and non-gravid fish. Walleye pollock tilt angles were centred at 90° and did not differ among densities or between light and dark cycles. Target strength–length regressions and KRM-predicted backscatter models closely matched in situ target-strength measurements for walleye pollock in the Bering Sea. Backscatter variability can be minimized through judicious deployment of equipment and equipment-parameter settings, but the relative influence of biological factors on backscatter amplitude has not been determined.

scholarly journals Mechanisms of Sound Production in Walleye Pollock Theragra chalcogramma (Pallas).

1995 ◽  
Vol 61 (2) ◽  
pp. 243-244 ◽  
Author(s):  
Yong-Seok Park ◽  
Yasunori Sakurai ◽  
Kohji Iida ◽  
Tohru Mukai
Keyword(s):  
Sound Production ◽  
Walleye Pollock ◽  
Theragra Chalcogramma ◽  
Walleye Pollock Theragra Chalcogramma
Sign in / Sign up

Export Citation Format

Share Document