scholarly journals In situ swimming behaviour of individual mesopelagic fish studied by split-beam echo target tracking

2001 ◽  
Vol 58 (1) ◽  
pp. 346-354 ◽  
Author(s):  
T Torgersen
Keyword(s):  
Target Tracking ◽  
Swimming Behaviour ◽  
Mesopelagic Fish

scholarly journals In situ swimming speed and swimming behaviour of fish feeding on the krill Meganyctiphanes norvegica

2005 ◽  
Vol 62 (8) ◽  
pp. 1822-1832 ◽  
Author(s):  
M SR Onsrud ◽  
S Kaartvedt ◽  
M T Breien
Keyword(s):  
Target Tracking ◽  
Water Column ◽  
Swimming Speed ◽  
Original Data ◽  
Clupea Harengus ◽  
Swimming Behaviour ◽  
Fish Feeding ◽  
Sea Bottom ◽  
Acoustic Target

In situ swimming speed and swimming behaviour of dielly migrating planktivorous fish were studied at a 120-m-deep location. Acoustic target tracking was performed using a hull-mounted transducer and submersible transducers located on the sea bottom and free hanging in the water column. The original data displayed a relationship between distance to transducer and swimming speed. A simplistic smoother applied during post-processing, appeared to break this relationship. Target tracking thus provided robust results on in situ swimming behaviour throughout the water column. Swimming speeds of deep-living fish, mainly Norway pout (Trisopterus esmarkii) and whiting (Merlangius merlangus), were highest during the day (speeds centred around 14–16 cm·s–1) and decreased somewhat by night (modes around 10–11 cm·s–1). Fish in the upper 10–30 m swam somewhat faster (speeds ranging from 16 to 24 cm·s–1). Fish in the upper layer at night were mainly Atlantic herring (Clupea harengus), sprat (Sprattus sprattus), and whiting. We ascribe the reduction of swimming speed in deep-living fish at night to a switch from visual feeding during daytime to nonvisual feeding by night. We suggest that shallow-living fish could forage visually even by night. Most tracks were fairly short, but some long tracks unveiled elaborate swimming paths as well as cyclic swimming behaviour.

scholarly journals New cave-dwelling amphipods (Lysianassidae, Hadziidae) from the Dominican Republic (Hispaniola)

1998 ◽  
Vol 68 (1) ◽  
pp. 37-66 ◽  
Author(s):  
Damià Jaume ◽  
H.P. Wagner
Keyword(s):  
Dominican Republic ◽  
Regression Model ◽  
West Indian ◽  
Swimming Behaviour ◽  
Marine Origin ◽  
Fresh Waters ◽  
Anchialine Caves ◽  
The Way

Two new stygobiont amphipods are described from anchialine caves located in the Jaragua region (Pedernales Prov., Dominican Republic, Hispaniola). Ottenwalderia kymbalion gen. et sp. nov. is the first lysianassoid known to have penetrated into completely fresh waters, and the fourth colonizing hypogean habitats. Bahadzia jaraguensis sp. nov. is the second representative of this West Indian thalasso-stygobiont genus to be reported from fresh waters; it exhibits the most troglomorphic aspect (i.e. elongation of first antennae and sixth pereiopods) recorded for the genus. Its diagnosis is complemented with a key to the species of the genus Bahadzia. The in situ swimming behaviour of both taxa is briefly described. It is postulated that both amphipods share a rather recent, Plio-Pleistocene marine origin, having invaded passively the continental waters in the way described by the so-called Regression model.

scholarly journals Mesopelagic flesh shear viscosity estimation from in situ broadband backscattering measurements by a viscous–elastic model inversion

2021 ◽  
Author(s):  
Babak Khodabandeloo ◽  
Mette Dalgaard Agersted ◽  
Thor A Klevjer ◽  
Geir Pedersen ◽  
Webjørn Melle
Keyword(s):  
Shear Viscosity ◽  
Spherical Model ◽  
Biological Information ◽  
Target Strength ◽  
Mesopelagic Fish ◽  
Elastic Model ◽  
Acoustic Measurements ◽  
Model Inversion ◽  
Fish Flesh

Abstract In fisheries acoustics, target strength (TS) is a key parameter in converting acoustic measurements to biological information such as biomass. Modelling is a versatile tool to estimate TS of marine organisms. For swimbladdered fish, flesh shear viscosity is one of the required parameters to correctly calculate TS around the resonance frequency, where the target scatters most strongly. Resonance of mesopelagic swimbladdered fish can occur over a range of frequencies and can be within commonly used frequencies (e.g. 18, 38, or 70 kHz). Since there is little information on flesh shear viscosity of fish, especially for mesopelagic species, their resonance can bias the biological information extracted from acoustic measurements. Here, first, the applicability of using a spherical model to estimate resonant backscattering of a generic swimbladder is investigated. Subsequently, a viscous–elastic spherical gas backscattering model is used to estimate the flesh shear viscosity of swimbladdered mesopelagic fish (most likely Cyclothone spp., Family: Gonostomatidae) from in situ broadband backscattering measurements. Finally, the effects of flesh shear viscosity on the TS of swimbladdered mesopelagic fish at 18, 38 (a widely used channel to study mesopelagic layers), and 70 kHz are examined.

scholarly journals Diel dynamics of dissolved organic matter and heterotrophic prokaryotes reveal enhanced growth at the ocean’s mesopelagic fish layer during daytime

2019 ◽  
Author(s):  
Xosé Anxelu G. Morán ◽  
Francisca C. García ◽  
Anders Røstad ◽  
Luis Silva ◽  
Najwa Al-Otaibi ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Heterotrophic Bacteria ◽  
Mesopelagic Fish ◽  
Diel Cycles ◽  
Organic Carbon Concentration ◽  
Mesopelagic Zone ◽  
Heterotrophic Prokaryotes ◽  
Specific Growth Rates

ABSTRACTContrary to epipelagic waters, where biogeochemical processes closely follow the light and dark periods, little is known about diel cycles in the ocean’s mesopelagic realm. Here, we monitored the dynamics of dissolved organic matter (DOM) and planktonic heterotrophic prokaryotes every 2 h for one day at 0 and 550 m (a depth occupied by vertically migrating fish during light hours) in oligotrophic waters of the central Red Sea. We additionally performed predator-free seawater incubations of samples collected from the same site both at midnight and at noon. Comparable in situ variability in microbial biomass and dissolved organic carbon concentration suggests a diel supply of fresh DOM in both layers. The presence of fish in the mesopelagic zone during daytime promoted a sustained, longer growth of larger prokaryotic cells. The specific growth rates were consistently higher in the noon experiments from both depths (surface: 0.34 vs. 0.18 d−1, mesopelagic: 0.16 vs. 0.09 d−1). Heterotrophic bacteria and archaea in the mesopelagic fish layer were also more efficient at converting DOM into new biomass. These results suggest that the ocean’s twilight zone receives a consistent diurnal supply of labile DOM from diel vertical migrating fishes, enabling an unexpectedly active community of heterotrophic prokaryotes.

scholarly journals Presettlement schooling behaviour of a rocky fish in a shallow area. Is it related to local environmental conditions?

2020 ◽  
Vol 84 (3) ◽  
pp. 243 ◽  
Author(s):  
Pamela Palacios-Fuentes ◽  
Macarena Díaz-Astudillo ◽  
María Antonia Reculé ◽  
F. Patricio Ojeda ◽  
Mauricio F. Landaeta
Keyword(s):  
Wind Stress ◽  
Environmental Conditions ◽  
Fish Larvae ◽  
Seawater Temperature ◽  
Austral Summer ◽  
Swimming Behaviour ◽  
Larval Behaviour ◽  
Rocky Reefs ◽  
Schooling Behaviour

This study evaluates the swimming behaviour of pre-settled fish larvae of the triplefin Helcogrammoides chil­ensis (Tripterygiidae) in relation to local environmental conditions. Larval aggregations were recorded on rocky reefs off central Chile during the austral summer of 2014 and 2016 to describe their swimming behaviour (i.e. solitary, shoaling, schooling) and relate it to in situ water temperature, wind stress, wind speed and turbulence. Shoaling and solitary behaviour were influenced only by wind-induced turbulence in 2014 and by seawater temperature and wind stress in 2016. Schooling behaviour was not influenced by any of the environmental variables. In situ swimming behaviour of fish larvae has been little investigated, and this work proposes a non-invasive in situ methodology for studying fish larval behaviour.

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