Boletín de la Sociedad Zoológica del Uruguay, 2023

Vol. 32 (1): e32.1.4

ISSN 2393-6940

https://journal.szu.org.uy

DOI: https://doi.org/10.26462/32.1.4

ABSTRACT

In this article, the capture of two pregnant females of the

Brazilian Guitarfish, Pseudobatos horkelii, is recorded.

Although the species is Critically Endangered and it

capture is prohibited, the illegal catches occur

nevertheless.

Key words: Chondrichthyes, Pseudobatidae, fishes,

predatory fishing.

RESUMEN

En este artículo se registra la captura de

dos hembras gestantes de la raya viola, Pseudobatos

horkelii. Aunque la especie está en Peligro Crítico de

extinción y su pesca está prohibida, las capturas

continúan ocurriendo de forma ilegal.

Palabras clave: Condrictios, Elasmobranquios,

peces, pesca depredadora.

The Family Rhinobatidae comprises six genera

with 45 species (Nelson, 2016), one of these species is

the guitarfish Pseudobatos horkelii (Muller and Henle,

1841), which can be found from the coast of the state of

Bahia in Brazil, to Uruguay and Argentina (Compagno,

1999; Menni and Stehmann, 2000). In general, this

species inhabits benthic environments of the

continental shelf, on sandy or muddy bottoms and

occurs throughout the year, being a resident species

(Vooren, 1997). The southern shelf is the only area

within its geographic distribution with a high abundance

Registro de hembras gestantes de Pseudobatos

horkelii (Muller & Henle, 1841), una raya guitarra en

peligro crítico aguas afuera del Atlántico

Sudoccidental.

of this species (Vooren and Klippel, 2005).

Pseudobatos horkelii is a yolk sac viviparous species

(Lessa et al., 1986; Wourms, 1988), i.e., the embryo

develops mainly through the yolk available in the

mature oocyte, but other nutritional sources have

recently been discovered (Wosnick et al., 2022). On the

continental shelf of southern Brazil, the reproductive

cycle is synchronized at the population level, so that

adult females give birth at the same time of the year.

The time of birth corresponds to the months of

February and March, when females are able to

copulate soon after giving birth, and a new pregnancy

occurs (Vooren and Klippel, 2005).

Pseudobatos horkelii is globally classified by the

International Union for Conservation of Nature (Pollom

et al., 2020) as "Critically Endangered" (CR), the same

status for the Brazilian regional assessment. According

to the Ministry of Environment (MMA), the capture of P.

horkelii is prohibited by National Legislation (Law nº

10.683) in the States of Rio de Janeiro, São Paulo,

Paraná, Santa Catarina, and Rio Grande do Sul

(IBAMA, 2004), though some studies show these

catches using molecular approaches (De Franco et al.,

2012; Alvarenga et al., 2021). Even so, either by

accidental or illegal capture, individuals continue to be

captured. Thus, it is of utmost importance to create,

implement, and maintain projects resulting from

networked partnerships between the academic

community and environmental protection agencies,

which aim at the conservation of this and other

endangered species. The extension project ICB/FURG

in partnership with the Environmental Patrol of the

Military Brigade (PATRAM) - PROPESP registration

number EXT109 - "Implementation of the regulations

prohibiting fishing and landing of endangered species

of Chondrichthyes in the State of Rio Grande do Sul",

represents a collaboration to formalize the production

Bol. Soc. Zool. Uruguay (2ª época). 2022. ISSN 2393-6940Vol. 32 (1): e32.1.4

RECORD OF PREGNANT FEMALES OF Pseudobatos horkelii (MULLER & HENLE, 1841), A CRITICALLY

ENDANGERED GUITARFISH OFF SW ATLANTIC

Yan Gowert* y Maria Cristina Oddone

yangowert@furg.br

Fecha de recepción: 19 de enero de 2023

Fecha de aceptación: 30 de mayo de 2023

Universidade Federal do Rio Grande, Instituto de Ciências Biológicas, Setor de Morfologia/Pesquisa em

Chondrichthyes, Av. Itália, Km 8 s/n, Campus Carreiros, 96203-900 Rio Grande, RS, Brasil

*Corresponding author:

Yan Gowert* y Maria Cristina Oddone

of technical reports of species identification to detect

the capture of endangered species. The objective of

this work is to record an illegal and intentional fishing

event where there was a massive capture of pregnant

females of P. horkelii, in the South of Rio Grande do Sul,

in Southern Brazil, SW Atlantic.

The seizure occurred on 12/22/2018 in the city of

São José do Norte (32º 00' 53" S and 52º 02' 30" W)

(Fig. 1), the number of specimens of P. horkelii found

was 2,134, totaling approximately 10,000 kg. The

fishing gear was a bottom trawl, which was pulled

manually from a motor boat. Once landed, the

Fig. 1. Map of the study area, Mar Grosso beach in the municipality of São José do Norte, Rio Grande do Sul, Brazil, where

the capture of about 10 tons of Pseudobatos horkelii was carried out on 12/22/2018.

Table 1. Measured variables with their respective values. Total length (CT), liver weight (LW), digestive tract weight (DTW), follicle

diameter (FD), ovary weight (OW) and total weight (TW). P. horkelii specimens collected on 12/22/2018 at mar grosso beach, in the city of

São José do Norte, Brazil.

Specimens CT (cm) LW (g) DTW (g) FD (cm) OW (g) TW (g)

#1 117.0 181 83 3.5 110.3 5630

#2 113.0 202 80 3.5 L: 17.9; R: 60.4 4780

Bol. Soc. Zool. Uruguay (2ª época). 2022. ISSN 2393-6940Vol. 32 (1): e32.1.4

3Record of pregnant females of Pseudobatos horkelii.

Fig. 2. Moment when part of the Pseudobatos horkelii catch was collected. A total of 2,134

specimens were captured (A). Dorsal view of pregnant female of Pseudobatos horkelii (B).

Ventral view of pregnant female of P. horkelii (C).

Bol. Soc. Zool. Uruguay (2ª época). 2022. ISSN 2393-6940Vol. 32 (1): e32.1.4

Yan Gowert* y Maria Cristina Oddone

specimens were removed from the net and

immediately placed on a track for transport and

marketing moment when the seizure occurred. On

March 1, 2019, PATRAM donated two of the seized

individuals for species identification and biological

sampling. The specimens were taken to the

Morphology II Instituto de Ci ncias

Biológicas, FURG, for further analysis. Taxonomic

identification of individuals followed Vooren and Klippel

(2005). Biological sampling included the record of total

laboratory at the ê

Fig. 3. Ventral view of the abdominal cavity of individual #1 after removal

of the digestive system, ovaries full of mature vitellogenic follicles (A).

Appearance of the gravid uteri after removal of the ovaries (B). Tertiary

membrane of the egg (C). Uterus contents, showing uterine egg yolk

and tertiary membrane. Right (above) and left uterus (below), the

anterior region of the oviduct is oriented to the left, where the oviductal

glands can be seen (E). Embryo removed from one of the uteri, showing

external branchial filaments and without pigmentation (F).

Bol. Soc. Zool. Uruguay (2ª época). 2022. ISSN 2393-6940Vol. 32 (1): e32.1.4

5Record of pregnant females of Pseudobatos horkelii.

length, total weight, liver weight, digestive tract weight,

diameter of pre-ovulatory follicles and ovarian weight

(Table 1). Females were identified as specimens #1

and #2. The total weight of female #1 was 5.63 kg and

female #2 weighed 4.78 kg. Female #1 had three

preovulatory vitellogenic follicles with a diameter of 3.5

cm, in each ovary. The combined weight of the ovaries

was 110.3 g. The individual weight of the ovaries was

not available as the follicles dissolved during extraction

and manipulation; however, the contents were included

in the use of petri dish. In individual, the left ovary was

17.9 g (one vitellogenic follicle 3.5 cm in diameter and

seven smaller 1.0 cm each). The right ovary weighed

60.4 g (three large follicles 3.5 cm in diameter each and

six smaller ones). One embryo was in individual #2,

(Fig. 3, F).

The results found show that the specimens

sampled are adult individuals (Lessa et al., 1986). The

species comes close to the coast with the objective of

reproduction, since the young are born in this region

(Vooren and Klippel, 2005). Thus, exorbitant catches

like this one, demonstrate that P. horkelii, a Critically

Endangered species, continues to be over captured,

even during the reproductive period, in the southern

coast of Brazil, were females migrate in warmer month

for parturition.

seudobatos

but

it was already in a state of decomposition

P horkelii is a viviparous species, and in

comparison to oviparous species, the viviparous

reproduction of those species depending solely on a

yolk sac, and tends to be associated with a more

moderate reproductive rate (Wourms, 1988). The

specificity of the lower reproductive rate of this species

coupled with its dependence on coastal areas for

reproductive purposes, continuously increases the

vulnerability of the local population (Vooren and

Klippel, 2005). In addition, although actual legislation

avoids the capture and landing of this species, illegal

catches are still a fact, as is the case in the present

report.

The guitarfishes have been steadily declining over

time. In 2014, the group was identified as one of the

most susceptible elasmobranch families to fisheries,

along with sawfishes (Dulvy et al., 2014). It is evident

that these fishes are highly vulnerable in shallow

coastal ecosystems, as they are easily accessible to

intensive fishing practices. This could be the primary

reason why the vast majority of guitarfishes

populations are facing severe threats all over their

distribution areas (Moore, 2017).

Once fish populations collapse, potential stock

recovery is a time-consuming process, even if fishing

pressure is reduced (Hutching and Reynolds, 2004).

Furthermore, at a global level, substantial declines in

guitarfishes populations have already been

documented, along with the disappearance of some

species elsewhere (Carlisle et al., 2007; Diop and

Dossa, 2011). The partnership between scientists and

conservation-focused organizations represents a

valuable synergy that combines scientific knowledge,

practical resources, and field efforts to effectively

safeguard critically threatened species as the

guitarfishes.

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Editor de Sección: Marcelo Loureiro

Bol. Soc. Zool. Uruguay (2ª época). 2022. ISSN 2393-6940Vol. 32 (1): e32.1.4