MARINE AND FISHERY SCIENCES 36 (3): XXX-XXX (2023)

https://doi.org/10.47193/mafis.3632023010905

ABSTRACT. This is the first description of diurnal pelagic aggregations of the bottom-dwelling

Argentine red shrimp (Pleoticus muelleri) registered with a broadband scientific echosounder. A

pelagic trawl net and an underwater video camera were used to validate all the information present-

ed in this paper. Shrimp aggregations were characterized by increasing frequency response, more

evident at frequencies greater than 120 kHz. Identification of the acoustic signature of this resource

is of particular interest for the development of new methodologies to complement the traditional

swept area method of estimation.

Key words: Hydroacoustic, frequency response, echosounder.

Primeras descripciones de agregaciones pelágicas diurnas de langostino (Pleoticus muelleri)

utilizando una ecosonda de banda ancha operando frecuencias múltiples

RESUMEN. Reportamos la primera descripción de agregaciones pelágicas diurnas de langostino

(Pleoticus muelleri) utilizando una ecosonda científica de banda ancha. Toda la información presen-

tada en este manuscrito fue validada por medio de una red de arrastre pelágica y una cámara de

video submarina. Las agregaciones de langostino se caracterizaron por poseer una respuesta en fre-

cuencia creciente, siendo más evidente a frecuencias superiores a 120 kHz. La identificación de la

firma acústica de las agregaciones pelágicas de langostino es de particular interés para el desarrollo

de nuevas metodologías que complementen la evaluación tradicional de este recurso, realizada a tra-

vés del método por área de barrida.

Palabras clave: Hidroacústica, frecuencia de respuesta, ecosonda.

The Argentine red shrimp, Pleoticus mulleri (Spence Bate, 1888) (Decapo-

da, Soleoceridae), is a crustacean with a wide latitudinal distribution in the

southwestern Atlantic Ocean, ranging from southern Brazil (23° S) to Santa

Cruz province (50° S), Argentina (de la Garza et al. 2017). The species has a

wide bathymetric distribution, being found from 3 to 190 m deep. It is char-

acterized by a benthic-demersal behavior during the day, hindering the

acoustic detection of the species near the bottom. It is the fishery with the

greatest impact on the Argentine economy due to its life cycle, high repro-

*Correspondence:

cabreira@inidep.edu.ar

Received: 4 April 2023

Accepted: 16 May 2023

ISSN 2683-7595 (print)

ISSN 2683-7951 (online)

https://ojs.inidep.edu.ar

Journal of the Instituto Nacional de

Investigación y Desarrollo Pesquero

(INIDEP)

This work is licensed under a Creative

Commons Attribution-

NonCommercial-ShareAlike 4.0

International License

Marine and

Fishery Sciences

MAFIS

NOTE

First descriptions of diurnal pelagic aggregations of the Argentine red

shrimp (Pleoticus muelleri ) using a broadband echosounder operating at

multiple frequencies

ARIEL G. CABREIRA1, *, GUSTAVO J. MACCHI1, 2 and PAULA MORIONDO DANOVARO1

1Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Paseo Victoria Ocampo Nº 1, B7602HSA - Mar del Plata, Argentina.

2Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Investigaciones Marinas y Costeras (IIMyC),

Rodríguez Peña 4002, B7602GSD - Mar del Plata, Argentina. ORCID Ariel G. Cabreira https://orcid.org/0009-0009-5184-6165,

Gustavo J. Macchi https://orcid.org/0000-0003-1821-5491

ductive potential, resilience, and successful fish-

ing management. It was the largest shrimp export

in 2018, representing more than 60% of the total

income of fishing currencies of the country

(SSPyA 2023).

Several investigations have been conducted by

the Instituto Nacional de Investigación y Desar-

rollo Pesquero (INIDEP) to evaluate changes

occurring in the shrimp population. Hydroa-

coustic techniques are currently one of the most

widely used tool for estimating species abun-

dance and distribution in the pelagic environ-

ment (Simmonds and MacLennan 2007). In

Argentina, this methodology is basically used for

the estimation of the abundance of important

fishing stocks such as anchovy (Engraulis

anchoita), mackerel (Scomber scolias), Fuegian

sprat (Sprattus fuegensis) and blue whiting

(Micromesistius australis) (Cabreira et al. 2009,

2011; Casarsa et al. 2019). Acoustic techniques

have been used to study a variety of crustaceans,

including krill (Euphausia superba), the most

common and important species in the Antarctic

ecosystem (Madureira et al. 1993; Cox et al.

2010; Valdez et al. 2022). In Argentina, acoustic

techniques were utilized for the study of pelagic

concentrations of Grimothea gregaria (Diez et

al. 2012, 2016).

During an environmental survey carried out on

December 2018 aimed to characterize the frontal

system of Peninsula Valdés (Figure 1), daytime

pelagic concentrations of Argentine red shrimp

were detected by a scientific echosounder operat-

ing multiple frequencies (Macchi 2019). During

the survey, the acoustic acquisition was carried

out continuously (24 h) by using a calibrated

broadband echosounder SIMRAD EK80 operat-

ing six split beam transducers: 18, 38, 70, 120,

200, and 333 kHz. Transmission of pulses were

simultaneous and in a continuous wave (CW). A

pulse duration of 1 ms at maximum power was

established for information acquisition. Two of

the fourteen trawls carried out for validating

echorecords (trawl station 6 and 12) were direct-

2MARINE AND FISHERY SCIENCES 36 (3): XXX-XXX (2023)

Figure 1. Research area and trawls carried out during the survey. Red dots indicate trawls executed to identify acoustic informa-

tion with crustacean characteristics.

W66° 65° 64° 63° 62° 61°

45°

44°

43°

42°

12 13

Bahía Camarones

Rawson

Chubut

ed to identify acoustic information that matched

characteristics of crustaceans (Figure 1). A pelag-

ic net designed on the scale of the large Nichimo

net was used to capture midwater organisms. Net

dimensions were 47 m headline, 7 m vertical

opening, 400 mm wingspans, and 60 mm cod

end. Acoustic telemetry sensors monitored real-

time performance of the fishing gear, allowing

the measurement of the vertical opening of the

net and the position in the water column during

trawling. The catch obtained was separated by

species, weighed and individual shrimp

cephalothorax length (CL) was measured.

Shrimps were classified by sex and maturity stage

using the scale described by Boschi (1989).

Acoustic data were post processed using LSSS

(Large Scale Survey System) applying a mini-

mum threshold of -70 and a maximum of -30 dB.

A frequency response from 38 to 200 kHz was

determined for each area. At depth where aggre-

gations of interest were detected, the low

signal/noise ratio of the 333 kHz frequency led to

discarding it from the multifrequency analysis.

Thanks to good weather conditions and visibility

of the water, an underwater video camera was

installed in the CTD rosette, which also docu-

mented the presence of shrimps in the pelagic

environment.

An acoustic backscatter layer between 20 and

30 m deep (40 m from the bottom) was observed

on December 8 at 4:30 am (7:30 GMT) in the

absence of sunlight. Thus, to identify the

backscattering layer, a trawl sampling was car-

ried out (Figure 2; station 6). The corresponding

catch consisted mainly of 20 kg of shrimp and 2

kg of anchovy. There were two types of acoustic

aggregations differing in morphological and

acoustic frequency response observed at dusk

(Figure 3). The first scattering layer (between 20

and 30 m) presented distinctive characteristics of

diurnal anchovy schools (Cabreira and Madirolas

2007) and decreasing frequency response (typi-

cal of gas bladder fishes) (Figure 3 A). The sec-

ond scattering (between 32 and 42 m) was

formed by small aggregations with an increasing

frequency response, typical of crustacean-like

organisms (elastic shelled organisms with no

gaseous structures) (Figure 3 B). It is important

to highlight that the typical behavior of shrimp

during daytime is the formation of bottom-asso-

ciated aggregations.

On December 12 at 8:20 am (11:20 GMT) it

was decided to conduct an additional identifica-

tion trawl that matched the range of the second

layer (depth close to 30 m) characterized by an

increased frequency response (Figure 4; station

12). After 15 min of trawling, the catch was

mainly composed of shrimp (400 kg). Aggrega-

tions corresponded to the presence of reproduc-

tive concentrations (70% of mature and impreg-

nated females) with modes at 39 and 48 mm CL

(mean 42.38 mm) for males and females, respec-

tively (Figure 5). The presence of adult shrimp

moving in the pelagic stratum at 30 m depth was

CABREIRA ET AL.: MULTIFREQUENCY DESCRIPTIONS OF DIURNAL PELAGIC AGGREGATIONS OF SHRIMP (PLEOTICUS MUELLERI)

Figure 2. Pelagic trawl carried out at night over an acoustic backscatter layer detected between 20 and 30 m deep (echogram

from 120 kHz).

Bottom

Interest acoustic layer

also confirmed by underwater videos (Figure 6).

The acoustic signature of shrimp, showed in this

report, is of particular interest for the develop-

ment of new methodologies that complement the

traditional evaluation of the resource carried out

through the swept area method. The appearance

of pelagic concentrations of the species during

daylight hours has generated a new challenge to

understand its behavior and population dynam-

ics. The availability of more precise and robust

instruments, new methods and protocols for data

collection, and innovative analysis methodolo-

gies are making it possible to exploit the

acoustic differences to characterize different

organisms. This makes this tool more consistent

for reliable identification and contribute to

obtain more precise estimates of the abundance

of fishery resources.

4MARINE AND FISHERY SCIENCES 36 (3): XXX-XXX (2023)

Figure 3. Formation of two types of acoustic aggregations during the dusk differing in morphological aspect, vertical position

in the water column, and variation in acoustic frequency responses. Note that two echograms are the same highlighting

anchovy (A) and shrimp (B).

Shrimp

Bottom

Anchovy

Bottom

Figure 4. Trawl carried out at 30 m depth aimed at validation of echorecording. Catch composed mainly of shrimp (400 kg).

Shrimp

Bottom

ACKNOWLEDGEMENTS

We wish to sincerely thank the crew on board

BIPO ‘Víctor Angelescu’, particularly the fishing

team. The identification of pelagic shrimp aggre-

gation was done additional to the regular fishing

stations. We also thanks to the reviewers for their

valuable comments. INIDEP contribution no 2299.

Author contributions

Ariel G. Cabreira: investigation, conceptual-

ization, formal analysis, methodology, writing-

CABREIRA ET AL.: MULTIFREQUENCY DESCRIPTIONS OF DIURNAL PELAGIC AGGREGATIONS OF SHRIMP (PLEOTICUS MUELLERI)

Figure 5. Cephalothorax length (mm) of Pleoticus muelleri.

30 34 36 38 40 42 44 46 48 50 52 54 56 58 60

Cephalothorax length (mm)

Figure 6. Underwater camera images taken to validate the acquired echorecordings. Left: a side view of a shrimp. Right: ventral

view of shrimp specimens moving in the pelagic stratum at 30 m depth.

original draft, writing-review and editing. Gusta-

vo J. Macchi: investigation, writing-review and

editing. Paula Moriondo Danovaro: investigation,

conceptualization, writing-review and editing.

REFERENCES

BOSCHI EE. 1989. Biología pesquera del langosti-

no del litoral patagónico de Argentina (Pleoti-

cus muelleri). Contrib Inst Nac Invest Desarr

Pesq (Mar del Plata). Nº 646: 1-71.

CABREIRA AG, MADIROLAS A. 2007. Caracteriza-

ción hidroacústica de los cardúmenes del

stock bonaerense de anchoíta (Engraulis

anchoita). Inf Téc INIDEP Nº 43/2007. 18 p.

CABREIRA AG, MADIROLAS A, BRUNETTI NE.

2011. Acoustic characterization of the Argen-

tinean short-fin squid aggregations. Fish Res.

108: 95-99.

CABREIRA AG, TRIPODE M, MADIROLAS A. 2009.

Artificial neural networks for fish-species

identification. ICES J Mar Sci. 66: 1119-1129.

CASARSA L, DIEZ MJ, MADIROLAS A, CABREIRA

AG, BURATTI CC. 2019. Morphometric

description of schools from two different

stocks of the southernmost sprat Sprattus fue-

gensis. Fish Res. 212: 29-34.

COX MJ, WARREN JD, DEMER DA, CUTTER GR,

BRIERLEY AS. 2010 Three-dimensional obser-

vations of swarms of Antarctic krill (Euphau-

sia superba) made using a multi-beam

echosounder. Deep-Sea Res Part II. 57: 508-

518. DOI: https://doi.org/10.1016/j.dsr2.2009.

10.003

DELAGARZA J, MORIONDO DANOVARO P, FER-

NÁNDEZ M, RAVALLI C, SOUTO V, WAESSLE J.

2017. An overview of the Argentine red

shrimp (Pleoticus muelleri, Decapoda,

Solenoceridae) fishery in Argentina. Biology,

fishing, management and ecological interac-

tions. Mar del Plata: Instituto Nacional de In-

vestigación y Desarrollo Pesquero (INIDEP).

42 p.

DIEZ MJ, CABREIRA AG, MADIROLAS A, LOVRICH

GA. 2016. Hydroacoustical evidence of the

expansion of pelagic swarms of Munida gre-

garia (Decapoda, Munididae) in the Beagle

Channel and the Argentine Patagonian Shelf,

and its relationship with habitat features. J Sea

Res. 114: 1-12. DOI: https://doi.org/10.1016/j.

seares.2016.04.004

DIEZ MJ, PÉREZ-BARROS P, CAROLINA ROMERO

M, SCIOSCIA G, TAPELLA F, CABREIRA AG,

MADIROLAS A, RAYA REY A, LOVRICH GA.

2012. Pelagic swarms and beach strandings of

the squat lobster Munida gregaria (Anomura:

Munididae) in the Beagle Channel, Tierra del

Fuego. Polar Biol. 35: 973-983. DOI: https://

doi.org/10.1007/s00300-011-1144-5

MACCHI G. 2019. Caracterización biológica y

ambiental del área “Frente Valdés” durante

diciembre de 2018. Inf Camp INIDEP Nº

4/2019.

MADUREIRA LSP, WARD P, ATKINSON A. 1993.

Differences in backscattering strength deter-

mined at 120 and 38 kHz for three species of

Antarctic macroplankton. Mar Ecol Prog Ser.

93: 17-24. DOI: https://doi.org/10.3354/meps

093017

SIMMONDS J, MACLENNAN DN. 2007. Fisheries

acoustics: theory and practice. 2nd ed. Wiley-

Blackwell. 252 p.

[SSPyA] SUBSECRETARÍA DE PESCA Y ACUICULTU-

RA. 2003. [accessed 2023 March]. https://www.

magyp.gob.ar/sitio/areas/pesca_maritima/

desembarques.

VALDEZ C, GRADOS D, LACRUZ L, CUADROS G,

CORNEJO R, CASTILLO R. 2022. Acoustic char-

acterization of automatically detected krill

(Euphausia superba) aggregations in the

Bransfield Strait and Elephant Island. Mar

Fish Sci. 35 (3): 315-331.

6MARINE AND FISHERY SCIENCES 36 (3): XXX-XXX (2023)