Inference of geometrical and behavioural parameters of individual fish from echo-trace-analysis

The volume scattering strength of swim-bladdered fish is very sensitive to fish size, shape, and orientation. However, the appropriate geometrical and behavioral parameters necessary to determine these parameters are not always available. Inadequate knowledge of these parameters limits our ability to correctly estimate lengths and abundances of fish with acoustic technology. A method for extracting geometrical and behavioral parameters of individual fish using a scattering model-based echo-trace-analysis (ETA) is presented. The scattering model used in the ETA is based on the Kirchhoff approximation and a prolate spheroid is used to approximate the shape of the swimbladder. The geometric shape of a resolved echo from an individual fish is used in a least-squares algorithm to infer information about the swimming speed, direction, and orientation of the fish. The acoustic intensity distribution of an individual fish along a resolved echo trace is used in a least-squares algorithm to infer information about the size, aspect ratio, and orientation of the swimbladder. Results from the ETA were more sensitive to variations in vertical swimming speed and orientation of the swimbladder than to variations in horizontal swimming speed and aspect ratio of the swimbladder. The proposed ETA was applied to field data, a 38 kHz echogram of a school of Atlantic cod recorded with a Simrad EK500 echo sounder. The inferred sizes and orientations of a number of the resolved echo traces for individual fish were consistent with available observation data. One of the advantages of the ETA method presented here is that it can be easily extended to a dual beam, a split-beam, or a multi-beam acoustic system.

[1]  C. Clay,et al.  Fundamentals of Acoustical Oceanography , 1997 .

[2]  David N. MacLennan,et al.  Acoustical measurement of fish abundance , 1990 .

[3]  Rolf J. Korneliussen.  Advances in Bergen Echo Integrator , 1993 .

[4]  A. K. Beltestad,et al.  Target-strength estimates of schooling herring and mackerel using the comparison method , 1996 .

[5]  J. Traynor.  Target-strength measurements of walleye pollock (Theragra chalcogramma) and Pacific whiting (Merluccius productus) , 1996 .

[6]  Ole Arve Misund,et al.  Adaptive behaviour of herring schools in the Norwegian Sea as revealed by high-resolution sonar , 1996 .

[7]  R. Bainbridge,et al.  The Speed of Swimming of Fish as Related to Size and to the Frequency and Amplitude of the Tail Beat , 1958 .

[8]  Kohji Iida,et al.  Depth dependence of target strength of live kokanee salmon in accordance with Boyle's law , 1996 .

[9]  L. M. Dickie,et al.  An Analytical Model of Acoustic Fish Reflection for Estimation of Maximum Dorsal Aspect Target Strength , 1991 .

[10]  K. Foote.  Linearity of fisheries acoustics, with addition theorems , 1983 .

[11]  T. Steig,et al.  Monitoring fish movement patterns in a reservoir using horizontally scanning split-beam techniques , 1996 .

[12]  C. Clay.  Composite ray‐mode approximations for backscattered sound from gas‐filled cylinders and swimbladders , 1992 .

[13]  Masahiko Furusawa,et al.  Application of echo-trace analysis to estimation of behaviour and target strength of fish , 1988 .

[14]  John E. Ehrenberg,et al.  Application of dual-beam and split-beam target tracking in fisheries acoustics , 1996 .

[15]  Dezhang Chu,et al.  Review and recommendations for the modelling of acoustic scattering by fluid-like elongated zooplankton: euphausiids and copepods , 2000 .

[16]  G. Rose,et al.  Target-strength studies on Atlantic cod (Gadus morhua) in Newfoundland waters , 1996 .

[17]  K. Foote.  Angular measures of dorsal aspect target strength functions of fish , 1980 .

[18]  M. Barangé,et al.  Empirical determination of in situ target strengths of three loosely aggregated pelagic fish species , 1996 .

[19]  Masahiko Furusawa,et al.  Prolate spheroidal models for predicting general trends of fish target strength , 1988 .

[20]  R. H. Love.  Resonant acoustic scattering by swimbladder‐bearing fisha) , 1978 .

[21]  D. MacLennan,et al.  Interpretation of in situ target-strength data , 1996 .

[22]  C. Feuillade,et al.  A viscous-elastic swimbladder model for describing enhanced-frequency resonance scattering from fish , 1998 .

[23]  P. Whitehead,et al.  Swimbladder form in clupeoid fishes , 1989 .

[24]  Z. Ye.  Low-frequency acoustic scattering by gas-filled prolate spheroids in liquids , 1997 .

[25]  Kenneth G. Foote,et al.  Effect of fish behaviour on echo energy: the need for measurements of orientation distributions , 1980 .

[26]  Target-strength measurements of Pacific hake (Merluccius productus) in Canadian waters using quasi-ideal and conventional beam transducers , 1996 .

[27]  M. Barangé,et al.  Evidence of bias in estimates of target strength obtained with a split-beam echo-sounder , 1995 .

[28]  Kenneth G. Foote,et al.  Rather‐high‐frequency sound scattering by swimbladdered fish , 1985 .

[29]  Manuel Barange,et al.  Potential improvements to current methods of recognizing single targets with a split-beam echo-sounder , 1996 .