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- Title
Target strength of skipjack tuna (Katsuwanus pelamis) associated with fish aggregating devices (FADs).
- Authors
Boyra, Guillermo; Moreno, Gala; Sobradillo, Bea; Pérez-Arjona, Isabel; Sancristobal, Igor; Demer, David A; Ratilal, Handling editor: Purnima
- Abstract
This paper presents measures of target strength (T S ; d B r e 1 m 2) and models of T S vs. fork length (L ; cm), i.e. T S = 20 l o g L + b 20, for skipjack tuna associated with fish aggregating devices (FADs) in the Central Pacific Ocean. Measurements were made using 38-, 120-, and 200-kHz split-beam echosounders on a purse-seine workboat during fishing operations. To mitigate potential bias due to unresolved targets, T S measurements were rejected if they were not simultaneously detected with multiple echosounder frequencies in approximately the same location. The filtered TS and concomitantly sampled L data were used to estimate b 20 = −76, −71, and −70.5 dB for 38, 120, and 200 kHz, respectively, using the method of least squares. For comparison, quasi-independent estimates of TS and b 20 were calculated from acoustic echo-integration and catch data representing entire aggregations around the FADs. The results differed by ≤1 dB for all three frequencies. The sensitivities of these results to variations in fish morphology and behaviour were explored using a simulation of T S for fish without swimbladders. The utility of the results on acoustic properties of skipjack tuna and next research steps to achieve selective fishing at FADs are discussed.
- Subjects
SKIPJACK tuna fisheries; ECHO sounding in fishing; ECHO sounders; FISH morphology; DATA analysis
- Publication
ICES Journal of Marine Science / Journal du Conseil, 2018, Vol 75, Issue 5, p1790
- ISSN
1054-3139
- Publication type
Article
- DOI
10.1093/icesjms/fsy041