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In situ relations of target strength to fish size for Great Lakes pelagic planktivores

Transactions of the American Fisheries Society

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Abstract

We found mean target strength to be a reliable in situ predictor of fish weight, which allows direct estimation of the pelagic planktivore fish biomass from target strength measurements. Fish were collected by midwater trawling concurrent with target strength measurements (120-kHz frequency) in Lake Michigan. The mean weight of fish caught ranged from 2 to 71 g and mean target strength ranged from -54.9 to -38.0 decibels. Changes in mean target strength explained 73% of the variability in mean weight for combinations of various planktivore species, principally rainbow smelt Osmerus mordax, bloaters Coregonus hoyi, and alewives Alosa pseudoharengus. Bloaters were found to be less acoustically reflective than the other pelagic species, and a linear regression model with a classification variable was used to predict weight from target strength for bloaters and for the other speices. We demonstrated that variations in the backscattering properties of different fish species must be considered to obtain accurate acoustic-based estimates of fish biomass.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
In situ relations of target strength to fish size for Great Lakes pelagic planktivores
Series title:
Transactions of the American Fisheries Society
Volume
126
Issue:
5
Year Published:
1997
Language:
English
Contributing office(s):
Great Lakes Science Center
Description:
p. 786-794
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
786
Last page:
794
Number of Pages:
8