Abstract
Pacific herring (Clupea pallasii Valenciennes, 1847) is a commercially important species that inhabits the coastal waters of the North Pacific from Korea to California, USA. This study analyzed the target strength (TS; dB re 1 m2) of Pacific herring individuals (n = 14, total length (LT) = 21.3–32.3 cm) at 38 and 120 kHz using ex-situ measurements and the Kirchhoff-ray mode (KRM) model. The least-squares regressions of the TS–LT relationship for the ex-situ measurements were TS38kHz = 20 log10(LT) − 70.10 (r = 0.17) and TS120kHz = 20 log10(LT) − 70.59 (r = 0.10). The least-squares regressions for the KRM model were TS38kHz = 20 log10(LT) − 68.39 (r = 0.40) and TS120kHz = 20 log10(LT) − 69.74 (r = 0.49). The b20 value of the KRM model was 1.71 dB higher than that of the ex-situ measurement at 38 kHz but similar at 120 kHz. These results provide basic data to evaluate the distribution and abundance of Pacific herring using fisheries’ acoustic technology.
Highlights
This study presents the relationship between target strength (TS) and total length LT of Pacific herring as a calculations must incorporate both experimental and theoretical methods [18]
The TS of fish is greatly affected by the size of the swim bladder; the relationship between Pacific herring LT and the swim bladder equivalent radius was investigated (Figure 4)
The swim bladder equivalent radius decreased as gonad somatic index (GSI) increased, but the correlation was non-significant
Summary
The distribution patterns showed that herrings characteristically form dense, round, or tall pelagic schools. The schools are typically small in size during summer and form a consistent, dense layer associated with the bottom in submarine gullies during winter [4]. It is an economically important fishery resource, especially in the northern latitudes of Korea and Japan [5,6]. The maximum catch of Pacific herring in South Korea in 2008 was approximately 45,000 tons, but this decreased to 25,000 tons in 2011 [7]. Records indicate fluctuations in herring catchment and variability in fishery productivity; a reasonable approach to manage and evaluate the status of the stock of Pacific herring is required for the sustainable use of this resource
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