Unicorn leatherjacket filefish, Aluterus monoc-

eros (Linnaeus, 1758) distributes in subtropical

and warm temperate zones worldwide (Froese

and Pauly, 2015). In the Atlantic Ocean it is usu-

ally reported from New England (USA) to South-

ern Brazil (32° S), including the Caribbean Sea

(Carvalho-Filho 1999; Figueiredo and Menezes

2000). The species, that feeds mainly on crus-

taceans, sponges, algae and corals, of 750 mm

maximum length reported, is associated to coral

and rocky reefs found up to 150 m depth (Carval-

ho-Filho 1999; Bernardes et al. 2005; Froese and

Pauly 2015). Its presence off Mar del Plata (38°

S) Argentina, was registered only once, over 40

years ago (Cousseau and Bastida 1976). The

objective of this note is to document Aluterus

monoceros southwards geographical extension

from the limit previously reported.

During a fishing operation carried out from

20th through 22nd January 2014, a unicorn leather-

jacket filefish specimen was caught on board of

the “Angela” bottom trawler off Necochea

coastal area (~ 39° 00’ S-58° 40’ W) at 20 m

depth in a rocky-sandy sediment area. The speci-

men was photographed, weighted, measured and

sexed at the laboratory, identified following Berry

and Vogele (1961) and preserved in the ichthy-

ologic collection of the Instituto Nacional de

Investigación y Desarrollo Pesquero (INIDEP)

under number INIDEP 852 (Figure 1). The sea

surface temperature (SST) was determined pro-

cessing Aqua-MODIS 4 km resolution satellite

images from: http//oceancolor.gsfc.nasa.gov

when the fish was caught (Figure 2).

The individual, a 1,212.2 g weight 511 mm total

length (TL) mature male (maturity stage IV) pre-

sented one hard dorsal spine, 49 soft rays in sec-

ond dorsal fin and 47 anal fin rays considered the

species diagnostic characters (Berry and Vogele

1961) and rough, dark brown skin with tiny thorns

MARINE AND FISHERY SCIENCES 32 (1): 43-46 (2019). https://doi.org/10.47193/mafis.3212019061804

NOTE

Aluterus monoceros (ACANTHOPTERYGII, TETRAODONTIFORMES)

SOUTHWARDS DISTRIBUTION RANGE EXTENSION IN ARGENTINE WATERS

ANDRÉS C. MILESSI1, 2, IGNACIO BRUNO1, EZEQUIEL COZZOLINO1and RODRIGO WIFF3

1Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP),

Paseo Victoria Ocampo Nº 1, Escollera Norte, B7602HSA - Mar del Plata, Argentina

e-mail: acmm@inidep.edu.ar

2Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC), Argentina

3Center of Applied Ecology and Sustainability (CAPES), Facultad de Ciencias Biológicas,

Pontificia Universidad Católica de Chile, Santiago, Chile

ABSTRACT. The presence of Aluterus monoceros (Linnaeus, 1758) in Mar del Plata, Argentina (38° S) was regis-

tered over 40 years ago. This new report extends its southernmost distribution limit to 39° S (Necochea: ~ 120 km).

The presence of the species could be associated to the warm subtropical water derived from the Brazilian continental

shelf. The hypothesis was tested with satellite images of the sea surface temperature recorded during the cruise the

specimen was caught.

Key words: Unicorn leatherjacket filefish, geographical distribution, Monacanthidae.

and dark spots. The SST indicated waters warmer

than 22° C related to the advection of oceanic

warm waters to the coast produced by a favourable

wind pattern from the North. Its horizontal distri-

bution showed the presence of warm waters all

over the Argentine shelf during Summer 2014.

The characteristics mentioned agree with the

descriptions of A. monoceros Brazilian specimens

by Berry and Vogele (1961), Carvalho-Filho

(1999), and Figueiredo and Menezes (2000).

The first record of A. monoceros in Argentine

waters published by Cousseau and Bastida (1976)

was based on an individual (508 mm TL) caught

on 27th April 1976 in Mar del Plata (38° S). The

new report extends the species previously known

range in ~ 120 km to the South. Neither the first

record produced in 1976 nor the scarce informa-

tion provided by INIDEP on different surveys

reported further analyses about sex, maturity stage

or weight. The SST result is compatible to the

process that forms the Subtropical Shelf Water

(STSW), a mix between the Plata Plume Water

and Tropical Waters (Moller et al. 2008). Said

oceanographic process is known as warm coastal

drift (Balech 1986; Balech and Ehrlich 2008) and

is common in Argentine waters during austral

Summer and Autumn, when winds coming from

the north and north-east become stronger (Guer-

rero et al. 1997; Martos and Piccolo, 1998). The

STSW flow allows the arrival of subtropical and

tropical fishes to Mar del Plata, Argentina

(Cousseau and Figueroa 1989; Figueroa et al.

1992, 2000; Izzo et al. 2009; Milessi et al. 2012,

2017).

A. monoceros new report constitutes another

piece of information supporting the hypothesis

that the warm coastal drift allows changes in trop-

ical and subtropical fishes distribution that, due to

an increase in water temperature, show a true

southwards expansion (Ortega et al. 2016) . Dur-

ing the last decade high abundance reports of

commonly unusual species such as Epinephelus

marginatus and Hyporthodus niveatus (Irigoyen

et al. 2005; Trobbiani et al. 2014; Milessi et al.

2018) off Argentina and Stellifer rastrifer in

Uruguay (Segura et al. 2008) suggest coloniza-

tion and establishment of new distribution areas.

To assess said hypothesis a time series analysis of

new species is needed. Correlations between new

species records and changes in other environmen-

tal variables may help understand the causes for

the reported distribution expansion. Data about

displacement of subtropical and tropical species

as a result of global warming may contribute new

records (Scenna et al. 2006; Venerus et al. 2007)

supporting the hypothesis that southwards expan-

sion of said species off Mar del Plata is favoured

by the increase of water temperature.

44 MARINE AND FISHERY SCIENCES 32 (1): 43-46 (2019)

5 cm

Figure 1. Aluterus monoceros (Linnaeus, 1758); INIDEP fish collection no. 852. Total length: 511 mm; weight: 1,212.2 g. Photo

by Marcela Tobio.

We are grateful to the “Angela” FV fishermen

(Pablo, Julio, Ariel and Gaby) who caught the

specimen; to M. Tobio for the photographs; to Dr.

A. Carvalho-Filho (Brazil) for providing literature

and to S. Barbini who deposited the fish in the

INIDEP collection. R. Wiff was funded by CON-

ICYT CAPES FB-0002. We also express our grat-

itude to an anonymous referee for the valuable

comments contributed on a previous draft of the

manuscript. INIDEP contribution no. 2072.

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Received: 24 June 2018

Accepted: 28 February 2019

46 MARINE AND FISHERY SCIENCES 32 (1): 43-46 (2019)