Swimbladder Morphology and Target Strength of a Mesopelagic Fish, Maurolicus japonicus

Fujino, Tadanori; Sadayasu, Kazuhiro; Abe, Kouji; Kidokoro, Hideaki; Tian, Yongjun; Yasuma, Hiroki; Miyashita, Kazushi

doi:10.3135/jmasj.36.241

Cited by 10 publications

(14 citation statements)

References 11 publications

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“…The step-wise behavior observed for both situations, i.e., with and without foraging, contrasts suggestions that stepwise relocation in mesopelagic fish represents saltatory search for prey (Kaartvedt et al, 2008). The similar behavior at descent and ascent is probably also unrelated to swim-bladder adjustment (Mehner, 2006;Fujino et al, 2009), as filling the swim-bladder during descent is a considerably slower process than emptying it during ascent (ascent; Strand et al, 2005). Also, some individuals at the fringes of the schools swam without stepping, i.e., without apparent need for swim-bladder adjustment.…”

Section: Discussionmentioning

confidence: 72%

Nighttime Swimming Behavior of a Mesopelagic Fish

2019

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Nocturnal migration of mesopelagic fish into surface waters is well-documented. Yet, although there is increasing evidence of individual-based deviations from average population migrations and of the importance of small-scale individual behavior for predator-prey interactions and energetic cycling, little is known about what mesopelagic animals do when in upper waters. Using high-resolution data from an upwardfacing, moored, split-beam echosounder we analyzed the night-time individual vertical swimming behavior of pearlsides (Maurolicus muelleri) over one winter. The population behavior is characterized by migration to the surface after sunset, "midnight-sinking" and another migration to the surface in the morning, followed by return to the daytime habitat. Focusing on individuals unveiled diverse behavioral patterns during different phases of the migration. After ascending to upper layers at dusk, M. muelleri leaves the surface waters, not by sinking, but by actively swimming in a step-wise pattern characterized by relocations alternated by pauses. Following the descent, vertical swimming is sustained at lower levels. Around midnight, the vertical swimming direction changes from predominantly downward to upward. Several hours before dawn, the fish start ascending toward the surface in a step-wise pattern. During population ascent in the afternoon and descent in the morning, some individuals at the fringes of schools migrate without intermittent pauses. This study documents the feasibility of using submerged, stationary echosounders in unveiling the individual behavior of mesopelagic fish.

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Section: Discussionmentioning

confidence: 72%

Nighttime Swimming Behavior of a Mesopelagic Fish

2019

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“…Few TS estimates have been reported for mesopelagic species using either in situ 31 or ex situ 32 measurements, modelling techniques 33 or a combination of them 34,35 . For mesopelagic fish, resonance at frequencies ≤ 38 kHz is particularly pronounced 13,36 , however, resonance at frequencies up to 60 kHz have also been described for smaller swimbladder sizes of migrating 37 and non-migrating fish 30 .…”

Section: Introductionmentioning

confidence: 99%

“…However, its actual swimbladder volume compensation performance during the trawling process is not clear, hampering the interpretation of the observed swimbladder size at the surface. In fact, when modelling the swimbladder, there is lack of consensus in the literature on whether to consider pearlside as a physostome 13,15,35 (the swimbladder volume obeys Boyle’s law) or as a physoclist 30,33,44,45 species.…”

Section: Introductionmentioning

confidence: 99%

Target Strength and swimbladder morphology of Mueller’s pearlside (Maurolicus muelleri)

Sobradillo

Boyra

Martinez

et al. 2019

Sci Rep

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In the last few years, there has been increasing interest in the commercial exploitation of mesopelagic fish and a trawl-acoustic methodology has been recommended to make estimates of abundance of these resources. This study provides relevant information on the scattering properties of a key mesopelagic fish species in the Bay of Biscay, Mueller’s pearlside (Maurolicus muelleri), necessary to convert the acoustic density into numerical abundance. The target strength (TS) of pearlside was estimated for the first time at five frequencies commonly used in acoustic surveys. A high-density filter was applied to reduce the bias derived from overlapping echoes erroneously assigned to single targets. Its relationship with fish length (b20) was also determined (−65.9 ± 2, −69.2 ± 3, −69.2 ± 2, −69.5 ± 2.5 and −71.5 ± 2.5 dB at 18, 38, 70, 120 and 200 kHz, respectively). Biomass estimates of pearlside in the Bay of Biscay during the four years of study (2014–2017) are given using the 38 kHz frequency. Morphological measurements of the swimbladder were obtained from soft X-ray images and used in the backscattering simulation of a gas-filled ellipsoid. Pearlside is a physoclist species, which means that they can compensate the swimbadder volume against pressure changes. However, the best fit between the model and the experimental data showed that they lose that capacity during the trawling process, when the swimbladder volume is affected by Boyle’s law.

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“…1a). In the present study, we estimated the biomass using target strength [7,[12][13][14], and significant positive correlations between biomass and BI for each species were observed. The biomass of lanternfish and pearlside was 2.26-19.16 times that of small pelagic fish.…”

Section: Discussionmentioning

confidence: 92%

“…Total length of transects was almost the same in this study. We calculated biomass of each species using Sa and target strength (TS) values for clupeid fish [12], jack mackerel, mackerel, and scad [13], lantern fish [7], and pearlside [14]. The species caught by midwater trawls were identified, and each species measured onboard.…”

Section: Methodsmentioning

confidence: 99%