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The devil is coming: Feeding behavior of juvenile Munk’s devil rays

(Mobula munkiana) in very shallow waters of Punta Descartes, Costa Rica

Nathalie Porsiel1; https://orcid.org/0000-0002-3030-8300

Sebastián Hernández2,3; https://orcid.org/0000-0002-2908-6050

Damien Cordier4; https://orcid.org/0000-0002-4583-3212

Maike Heidemeyer*4,5; https://orcid.org/0000-0001-7547-5631

1. University of Hamburg, Institute of Hydrobiology ad Fisheries Sciences, Hamburg, Germany;

Nathalie.Porsiel@posteo.de

2. Sala de Colecciones Biológicas, Facultad de Ciencias del Mar, Universidad Católica del Norte, Antofagasta, Chile;

pintarroja@gmail.com

3. Molecular Biology Lab, Center for International Programs, Universidad Veritas, San José, Costa Rica.

4. Asociación para la Conservación Integral de Recursos Naturales Equipo Tora Carey, El Jobo, La Cruz, Guanacaste,

Costa Rica; tempatalkite@hotmail.ca

5. Centro de Investigación en Ciencias del Mar y Limnología (CIMAR), Universidad de Costa Rica, San José, Costa

Rica; maike.heidemeyer@ucr.ac.cr (*Correspondence)

Received 30-I-2021. Corrected 28-IV-2021. Accepted 15-VI-2021.

ABSTRACT

Introduction: Identifying critical habitats for vulnerable elasmobranch species is crucial for effective conser-

vation measures. The Munk’s devil ray (Mobula munkiana) is endemic to the Eastern Pacific, but yet little is

known about its biology, ecology, and habitat use. As filter feeders, it is assumed that this species concentrates

at high-productive upwelling regions, such as the Costa Rican Dome. Like many elasmobranchs, its populations

are highly depleted and require urgent information to inform better conservation measures.

Objective: The study was conducted to gain information on a unique behavior observed in juvenile M. munki-

ana, so further information can be provided on early life stages of this vulnerable species.

Methods: From June to September 2017 and in August 2018, the feeding behavior of juvenile Mobula munki-

ana was observed in two shallow bays located at Punta Descartes, North Pacific Costa Rica. Individuals were

captured using a non-lethal method to obtain data on size, weight, and sex distribution. Plankton samples (n =

100) were taken at both bays throughout the months to infer diet composition.

Results: Munk’s devil rays showed a repetitive swimming movement parallel to the beach, feeding exclusively

in the shallow breaking zone of the low tide waves at depth <50cm. A total of 12 M. munkiana (11 live and

one found dead) indicated a juvenile feeding aggregation ranging from 490 – 610mm in disk width and 1400 –

2300gr in weight. The sex ratio (males to females) was 3:1. Zooplankton of the order Mysidacae was found in

the highest abundance in the breaking zone.

Conclusions: The specific behavior and seasonal occurrence of juvenile Munk’s devil rays in this area seem

to be driven by prey abundance. More research is needed to conclude the presence of reproductive adults at

deeper depths and the year-round habitat use of Punta Descartes. The area is threatened by unsustainable devel-

opment and requires realistic management strategies to guarantee the survival of vulnerable species and their

critical habitats.

Key words: Mobula munkiana; juvenile; Munk’s devil ray; migration; prey abundance; feeding.

Porsiel, N., Hernández, S., Cordier, D., & Heidemeyer, M.

(2021).The devil is coming: Feeding behavior of juvenile

Munk’s devil rays (Mobula munkiana) in very shallow

waters of Punta Descartes, Costa Rica. Revista de

Biología Tropical, 69(Suppl. 2), S256-S266. https://doi.

org/10.15517/rbt.v69iS2.48744

https://doi.org/10.15517/rbt.v69iS2.48744

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Mobulids are pelagic planktivorous and

globally distributed in warm subtropical to

tropical waters (Notarbartolo di Sciara et al.,

2017). They belong to the single genus Mobu-

la, that currently recognizes two manta (and a

putative species in the Atlantic) and nine devil

ray species (Hosegood et al., 2020; White et

al., 2018). While manta rays are the largest rays

(and among the largest fishes) in the world,

devil or mobula rays are much smaller but

resemble their larger sister species in both mor-

phology and biology. For instance, all mobulids

exhibit long-term gestation periods and low

annual reproductive output, and are extremely

long-lived (Couturier et al., 2012). However,

while manta rays have been reported to under-

take extensive migrations of several hundred

kilometres both horizontally (Germanov &

Marshall, 2014) and vertically (Braun et al.,

2015), little is known about the movement pat-

terns of devil rays. A study of Croll et al., 2012

showed less vertical migration in a devil ray

species. Tagged individuals of Mobula mobu-

lar (japanica) in the Eastern Tropical Pacific

stayed close to the surface, while their primary

prey shows diel migration of from more than

100 meters to the surface (higher depths at day-

time to surface at night-time).

The occurrence of mobulids at distinct

locations and/or habitats has been attributed

to both an interplay of environmental condi-

tions, such as productivity, temperature, and

food availability (Lezama-Ochoa et al., 2019;

Rohner et al., 2014) and biological require-

ments, like mating and availability of clean-

ing stations (Alves de Mendonça et al., 2020;

Jaine et al. 2012). In the Eastern Pacific, the

occurrence of devil rays is connected to higher

oceanic productivity, such as the upwelling

systems along the coast of Baja California Pen-

insula, Galapagos Islands, and Peru, and the

oceanic upwellings of the Costa Rican Dome

(Lezama-Ochoa et al., 2019). Different dietary

studies from stomach contents and stable iso-

tope analysis suggest that most mobulid species

are predominantly planktivorous and, except

for M. munkiana, overlap in their trophic

preference of euphausiids as principal prey

(Notarbartolo di Sciara, 1988; Sampson et al.,

2010; Stewart et al., 2017).

Mobula munkiana, also known as Munk’s

devil ray, attains the smallest size as mature

adults in the genus Mobula (Notarbartolo

di Sciara, 1987). This species is endemic to

the Eastern Tropical Pacific, distributed from

Baja California Peninsula, Mexico, to Peru,

including the Galapagos Islands of Ecuador

(Marshall et al., 2019). Like some of its sister

species, M. munkiana is often observed in large

schools composed of thousands of individuals,

particularly when mysid (Mysidium sp.) and

euphausiid (Nyctiphanes simplex) shrimps are

most abundant (Notarbartolo di Sciara, 1988;

Palacios et al., 2021). Similarly, their large

aggregations have also been attributed to mat-

ing behaviors (Stewart et al., 2018). In the Gulf

of California, Mexico, females are known to

segregate from males upon reaching sexual

maturity (López, 2009; Notarbartolo-di-Sciara,

1988), and a recent study suggests a further

ontogenetic segregation of neonate, juvenile,

and adult habitats (Palacios et al. 2021). Addi-

tionally, the last study found that juvenile

residence was more related to warmer water

temperatures than zooplankton abundance.

The northwest coast of Costa Rica is

directly influenced by the oceanic upwelling

system described as the Costa Rican Dome

(Fernández-Álamo & Färber-Lorda, 2006;

Fiedler, 2002). Around Punta Descartes, the

countries northernmost peninsula on its Pacific

coast, this phenomenon is particularly evident

during January – April, when sea temperatures

reach as low as 15 degrees (Cortés et al., 2014).

During this period, coastal productivity peaks

and, in consequence, triggers high zooplankton

abundance during most of the year (Fernández-

Álamo & Färber-Lorda, 2006; Fiedler 2002).

Punta Descartes has been classified as an area

of major conservation relevance because of its

extremely high coastal-marine biodiversity and

lack of protected areas (Alvarado et al., 2011).

Nonetheless, to date, there is little informa-

tion available on the abundance of ecologi-

cally important species, especially those that

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require enhanced conservation measures and

that inhabit this area.

Mobula munkiana, like all species within

this genus, have experienced severe population

declines mainly due to overexploitation and by-

catch (Couturier et al., 2012; Croll et al., 2016;

Stewart et al., 2018) and is currently classified

as vulnerable based on an assessment by IUCN

(Marshall et al., 2019). In the Eastern Pacific

of Costa Rica, by-catch mortalities are mainly

associated to tuna purse-seine fisheries, often

concentrated at the Costa Rican Dome (Croll et

al. 2016; Lezema-Ochoa et al., 2019). Targeted

fisheries of devil rays mainly occur in Mexico,

Peru, and Ecuador, either for local and regional

use and consumption of its meat or to supply

the Asian medicinal market with its gill plates,

where they are traded at high prices (Couturier

et al., 2012; Croll et al., 2016; O’Malley et al.,

2017). As a member state of relevant interna-

tional treaties, such as the Convention on the

Conservation of Migratory Species of Wild

Animals (CMS), Convention on International

Trade in Endangered Species of Wild Flora and

Fauna (CITES), and the Inter-American Tropi-

cal Tuna Commission (IATTC), both manta

and devil rays are protected under international

and national law. Specifically, the national

decree No. 38027-MAG currently prohibits

any fishery, onboard retention, landing, or com-

mercialization of mobulid rays.

Although M. munkiana has been listed in

the Costa Rican elasmobranchs checklist (Espi-

noza et al., 2018), there are no current studies

that specifically address the ecological require-

ments of this species in Costa Rican waters.

Information addressing this species’ biology,

ecology, and population trends, to enhance

effective conservation measures (Lawson et

al., 2017; Marshall et al., 2019) is urgently

needed. Here we report, for the first time, on

the presence, size, and sex distribution, as well

as feeding behavior of juvenile Munk’s devil

rays in northwest Costa Rica. We associate its

presence in extremely shallow waters with the

zonal distribution of Mysis sp. and detail a

non-lethal sampling method for M. munkiana.

MATERIALS AND METHODS

Study sites: El Jobo (11°02’01.5” N &

85°44’05.4” W) and Rajada (11°01’48.2” N &

85°44’42.6” W) beaches are adjacent bays on

the northernmost peninsula of Punta Descartes,

in Guanacaste province, Northwest Costa Rica

(Fig. 1). Their white sandy bottoms are fringed

by rocky reefs and outcrops that shelter the

bays during most of the year. Both bays are

approximately one kilometre wide. Inside the

bay, at the peak of the rainy season from

June to September, devil rays are commonly

observed in areas of shallow waves close to the

beach, identified by their uniform dark-violet

coloration and surfing fin tips when swimming

close to the surface.

Description of feeding behavior: The

swimming behavior of the devil rays was reg-

istered repeatedly by three observers (authors

NP, DC, and MH) in 13 days (nine at El Jobo

and four at Rajada) between June and Septem-

ber of 2017 and 2018, respectively. Observa-

tions took place either from the beach and

inside the water at variable distances between

one to twenty meters. Videographic evidence

was further collected with a drone at a height

of approximately five meters (DJI Mavic Pro

1). We registered when the rays unfurled their

cephalic lobes, as this behavior characterizes

feeding activity in mobulids (Ari & Correia,

2008; Mulvany & Motta, 2013), as well as their

movements in response to the movements of

the waves.

Devil ray capture: We then used a ten

meter long, 1.2 m high silk nylon minnow

seine net (mesh size ca. one cm), rolled up

and sustained at each end respectively by one

person, to block the rays’ swimming direc-

tion behind the spilling wave break at a depth

of approximately 1 m. Once the rays were in

close proximity, the net was unrolled on the

deeper end to encircle the individual(s) and

closed on both ends. The rays were maintained

inside the net with sufficient swimming ability

and were taken out one by one with a hand net

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for subsequent manipulation. We manipulated

each ray on a floating platform (Fig. S1), and

because devil rays require the water flow to

breathe, data collection was undertaken in two

to three sequential steps. Between those steps,

the rays were moved inside the hand net in the

water. For the entire procedure, a team of four

to five people was required, and completing the

protocol took about five minutes.

Data collection: Upon successful capture,

individuals were measured, weighed, sexed,

and tagged. All measurements were recorded

with a flexible measuring tape (± 0.5 cm). The

disc width (WD) was recorded from fin tip to

fin tip, total length (TL) from the center of the

superior mouth opening to the tip of the tail,

and the tail length (TaL) from the base of the

tail to the tip. Weight was taken with an elec-

tronic hanging scale (model H.S., brand UWE,

manufactured in Taiwan) with a capacity of 15

kg ± 0.01 kg. The rays were tagged with 3 cm

long T-bar anchor tags (model FD-94, Floytag,

Seattle, USA) on the right anterior side of the

tail base. We also included one fresh individual

found dead on the 30th of June 2017, on Rajada

beach, in which stomach content was inspect-

ed. Males and females were identified accord-

ing to the presence or absence of claspers.

Size at sexual maturity for this species (López,

2009; Notarbartolo di Sciara, 1988) was used

to infer the life history stage. Thus, males with

WD < 870 mm (Notarbartolo di Sciara, 1988)

and females with WD < 970 mm (López, 2009),

respectively, were classified as juveniles.

Zooplankton surveys: Because of the

overwhelming abundance of mysid shrimps

found in the stomach contents of one dead

devil ray, our surveys focused exclusively on

identifying the abundance of crustacean zoo-

plankton at different depths. On five occasions

between July and September 2017, plankton

surveys were conducted at El Jobo and Rajada

beach. Samples were collected with a 12.7 cm

mouth diameter plankton net (153 μm nylon

Fig. 1. Location of the two study sites on the Descartes Peninsula in northwest Costa Rica: A) El Jobo Beach, B) Rajada

Beach. Bathymetry is indicated in meters below sea level.

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cloth, 10 mesh; brand LaMotte, manufactured

in UK) and a 50 ml tube attached at the cod end

of the net. Samples were taken in the breaking

zone (BZ) of the waves at a depth of 0.5 m and

the shoaling zone (SZ) of 2.5 m depth, respec-

tively, from the surface and the bottom, where

the net was dragged for 10 seconds. On every

sampling day, five plankton tows per zone (BZ

& SZ from surface and bottom) were taken (N

= 100). Samples were inspected under a micro-

scope (10x magnification), morphologically

identified, and individuals counted.

Statistical analysis: Differences between

sexes were evaluated for all morphometric

measurements using conventional t-Student

tests, and the linear relationship of weight and

disk width was assessed with Pearson’s correla-

tion coefficient. Samples taken at Rajada and

El Jobo were grouped into surface, and bottom

plankton samples, respectively, from BZ and

ZZ, and differences in the number of individu-

als counted between zones (BZ/SZ) and depths

(surface/bottom) were assessed using a 2-factor

ANOVA with replications (El Jobo and Rajada

beaches). All analyses were conducted at a sig-

nificance level of P =0.05, using the program R

(R Core Team, 2020).

RESULTS

Feeding behavior: Devil rays were

observed following the breaking waves along

the shallow slopes of El Jobo and Rajada

beaches (Fig. 1A, Fig. 1B). This behavior was

especially conspicuous during low tide and is

generalized as followed (Fig. 2A): Single rays

or small groups of 2 – 10 individuals swim

parallel to the beach in both directions directly

in the surf zone, behind the breaking waves.

They swim in slow to moderate speed close to

the surface often with their pectoral fin tips cut-

ting through the surface of the water. Upon the

surging of a wave, they abruptly turn towards

the beach and follow the wave by rapidly flap-

ping their pectoral fins and notably increasing

Fig. 2. A) Illustration of the generalized swimming behavior of devil rays at shallow depths in response to the movement of

waves at El Jobo and Rajada beaches; B) Close up of unfurled cephalic lobes during the shoaling of the wave, and C) furled

cephalic lobes during non-feeding behavior (see text).

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speed while following the maximum amplitude

of the shoaling wave. Some individuals addi-

tionally conduct circular up and down move-

ments. Depending on the depth at which a wave

breaks, some individuals enter waters as shal-

low as 20 cm. Just before the wave break, they

abruptly turn around at a sharp angle and con-

tinue swimming at a slower pace into deeper

waters. Individuals unfurl their cephalic lobes

the moment they start following the shoaling

wave and move towards the beach (Fig. 2B),

which were clearly observed as round white

patches from above the water. Immediately

after they redirect back to deeper waters, these

cephalic lobes are furled back to their cephalic

horns (Fig. 2C).

Devil ray sampling: In a total of 9 surveys

carried out between June and September of

2017 (N = 8) and 2018 (N = 1), 11 M. mun-

kiana were captured at El Jobo beach, with

no successful capture at Rajada. Including

the dead individual from Rajada, our data set

contained 12 individuals, nine (75 %) were

identified as males and three (25 %) as females,

with a male to female sex ratio of 3:1. Because

there was no difference (p > 0.2) in WD nor

weight, males and females were pooled for fur-

ther analysis. WD ranged from 490 to 610 mm

(545 ± 35 mm, mean ± SE) and weight from

1400 to 3100 g (2108 ± 434 g, mean ± SE),

which were highly correlated (r(11) = 0.93, P <

0.000; Fig. 3). TL ranged from 460 to 840mm

(572 ± 98 mm), and TaL from 150 to 445mm

(386 ± 80 mm). All individuals were classified

as juveniles.

Zonal distribution of mysids: The num-

ber of individual mysids differed significantly

among zones and depths (F (3, 39) = 66.73, P <

0.0001), with the highest abundance of crusta-

ceans of the order Mysidacae registered at the

bottom of the BZ followed by the surface of the

BZ (Fig. 4). There was no significant difference

among sites nor dates (P > 0.1).

DISCUSSION

This is the first study that characterizes the

size distribution, sex ratio, and feeding behav-

ior of juvenile M. munkiana in Costa Rica and

Central America. Our findings suggest that

Punta Descartes serves as a juvenile feeding

ground for this vulnerable species during sever-

al months of the year. With a mean WD of 545 ±

35 mm, our sample resembles the average WD

of neonates at the recently described nursing

ground at Ensenada Grande, Baja California

Peninsula, suggested as such by the presence

of the umbilical scar (Palacios et al., 2021).

Although we did not intentionally register this

Fig. 3. Linear relationship of female (in red) and male (in blue) Mobula munkiana (N = 12) disk width (WD; mm) and weight

(g) sampled in Punta Descartes, North Pacific Costa Rica. For reference, WD of estimated size at birth range (Broadhurst et al.

2019; Notarbartolo di Sciara, 1988) is indicated in grey, mean ± SD of neonates and juveniles in green and violet, respectively

(Palacios et al. 2021), and male and female maturity sizes, respectively in blue and red (Notarbartolo di Sciara, 1988).

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scar during our surveys, inspections of photo-

graphs taken from the dead individual suggest

that at least this individual sampled was indeed

a neonate. Size at birth of M. munkiana is yet to

be determined but may range from 350 (Notar-

bartolo di Sciara, 1988) to 423mm WD (Broad-

hurst et al., 2019). Hence, with our smallest

individual captures of 490 mm WD, females

may give birth in the vicinity of these bays.

Pupping season for M. munkiana in Costa Rica

therefore appears similar to reports from Baja

California Peninsula, extending from April to

June (Palacios et al., 2021). Following local

observations and our capture reports, devil rays

are not observed within the bays before May

nor after September, but a more systematized

study is desirable to confirm the boundaries of

the reproductive season for Costa Rica.

Mobula munkiana feeds on zooplanktonic

crustaceans with main food items varying both

spatially and temporally (Coasaca-Céspedes et

al., 2018; Notarbartolo di Sciara, 1988). For

instance, M. munkiana feeds mainly on mysids

that peak during Baja California Peninsula’s

cold upwelling season (Notarbartolo di Sciara,

1988) and in its absence on the euphausiid

Nyctiphanes simplex (Coasaca-Céspedes et al.,

2018). Similar to Baja California Peninsula,

maximum primary productivity along the north

pacific coast of Costa Rica occurs from Decem-

ber to April stimulated by the upwelling Costa

Rican Dome (Fiedler, 2002), but zooplankton

abundance remains high during most months

(Fernández-Álamo & Färber-Lorda, 2006). In

fact, Punta Descartes has the highest zoo-

plankton abundance registered anywhere in the

country (Morales-Ramírez et al., 2018), pro-

viding suitable habitat for mobulids throughout

the year. Although the euphausiid N. simplex

is considered a dominant species in upwelling

areas of the Eastern Tropical Pacific (Brinton,

1979), coastal zooplankton surveys seem to

be dominated by copepods (Morales-Ramírez

et al., 2018; Morales-Ramírez et al., 2021),

raising questions on the feeding habitats of M.

munkiana in this area. Our plankton surveys

conducted at sites where devil rays exhibited

feeding behaviors were exclusively composed

Fig. 4. Mean (± SD) distribution (n individuals / 50 ml)

of mysids collected at the surface (triangles) and bottom

(squares) in the shoaling zone in blue (SZ) and the breaking

zone in yellow (BZ) on five days at El Jobo and Rajada

beaches. Dates with an asterisk (*) indicate days at which

devil rays were observed and/or sampled.

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of mysids, which, together with the stomach

content of the dead individual indicates that

mysids compose the diet of M. munkiana in

Costa Rica during at least a portion of its life

cycle and at least some months of the year.

However, mysids have not been identified in

any zooplankton survey published to date, and

the general lack of knowledge on Costa Rica’s

mysid fauna (Price et al., 2009) provides fur-

ther significance to our finding of mysids at

El Jobo and Rajada beach. It also urges for

more detailed studies on mysids’ interannual

dynamic in both shallow and deeper waters.

The benthic association and segregation

within shallow depths of mysids are known

to occur within and among species (Clutter,

1967), and we observed a significant zona-

tion of mysid abundance within less than 2.5

m depth, with a gradual increase shoreward.

Highest number of individuals were found on

the bottom in the breaking zone of the beach,

directly where juvenile M. munkiana unfurl

their cephalic lobes to feed. Thus, the feeding

action in depths as shallow as 0.2 m is prob-

ably explained by the higher abundance of prey

when compared to deeper waters. In fact, if a

similar dynamic of zooplankton species abun-

dance driven by upwelling and post-upwelling

events as described for Baja California Pen-

insula is true for Costa Rica, mysids are less

abundant in the only months juvenile devil rays

are observed in Punta Descartes. However, the

waves’ action eventually compensates for their

restricted distribution by dispensing them in

the water column, making them available for

filter feeders capable of entering such shal-

low waters. The fact that only juveniles of M.

munkiana were captured furthermore suggests

that the presence of this principal diet item,

albeit restricted to the breaking zone, might

become significant for the initial development

of juveniles.

Nonetheless, it is possible that larger, even

sexually mature, or reproductive individuals

were present in deeper depths of the bays of El

Jobo and Rajada. Palacios et al. (2021) found

a clear segregation of size classes, where neo-

nates and juveniles were exclusively found in

depths of between two and five meters, with

adults present in the same bay at depths greater

than 5 m. During our surveys, we observed

some individuals leaping out of the water at the

bays’ entrance, but a more rigorous sampling

of M. munkiana at different depths should be

conducted to further conclude on the different

life stages present throughout the year. Surpris-

ingly though was the male to female (M:F)

sex ratio of 3:1 we found in Punta Descartes,

whereas elasmobranch nursery areas, including

Ensenada Grande for M. munkiana (Palacios et

al., 2021), are often characterized by a 1:1 sex

ratio (Salomón-Aguilar et al., 2009). Sex ratios

in adult M. munkiana have been reported to

differ slightly in different time periods, either

in favor of males (López, 2009) or females

(Notarbartolo di Sciara, 1988), which in turn is

common for adult life stages of many elasmo-

branchs (Wearmouth & Sims, 2008). Whether

or not our male-skewed sex ratio indicates

juvenile segregation or is an artifact of low

sample size, this should be investigated in the

future. In any case, both El Jobo and Rajada

bays are likely providing refuge during vulner-

able early-life stages, not only by enhancing

growth through prey availability but also by

providing protection from predators, such as

sharks, which are considerable scarce in the

area (Espinoza et al., 2020).

This study is the first to report on a feed-

ing ground for juvenile Munk’s devil rays,

highlighting the need for local conservation

strategies for this vulnerable species. Although

the area is yet mostly undeveloped, large-scale

development plans focused on resort-like tour-

ism have already been initiated. For instance,

a 450-suite hotel, operates directly on the

beach and may present potential impacts on

the ecological health of the bay, either directly

or indirectly. Immediate plans include the

construction of similar hotels at Rajada Beach.

Because the beaches nor waters of Punta Des-

cartes are included under any protective cat-

egory of the country’s system of conservation

areas, such as national parks or reserves, the

future of this nursing ground is uncertain and

should be highlighted to enforce sustainable

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management plans according to Costa Rica’s

obligation in the protection of M. munkiana.`

Ethical statement: authors declare that

they all agree with this publication and made

significant contributions; that there is no con-

flict of interest of any kind; and that we fol-

lowed all pertinent ethical and legal procedures

and requirements. All financial sources are

fully and clearly stated in the acknowledge-

ments section. A signed document has been

filed in the journal archives.

See Digital Appendix at: /

Ver Apéndice digital en: revistas.ucr.ac.cr

RESUMEN

El diablo se aproxima: comportamiento de

alimentación de juveniles de mantas diablo

(Mobula munkiana) en aguas poco profundas de

Punta Descartes, Costa Rica

Introducción: La identificación de hábitats críticos para

especies vulnerables de elasmobranquios es crucial para

tomar medidas de conservación efectivas. La manta dia-

blo o raya de Munk (Mobula munkiana) es endémica

del Pacífico Oriental y se sabe poco sobre su biología,

ecología y uso de hábitat. Como filtradores, se asume que

se concentran en regiones de afloramiento con alta produc-

tividad; sus poblaciones se consideran en disminución y

requieren información urgente para fundamentar medidas

de conservación.

Objetivo: El estudio se realizó para obtener información

sobre un comportamiento de alimentación observado en

juveniles de M. munkiana, con el fin de proporcionar más

información sobre las primeras etapas de vida de esta espe-

cie considerada vulnerable a la extinción.

Métodos: De junio a setiembre de 2017 y en agosto de

2018, se observó el comportamiento de alimentación de los

juveniles de M. munkiana en dos bahías poco profundas de

Punta Descartes, en el Pacífico norte de Costa Rica. Los

individuos fueron capturados utilizando un método no letal

para obtener datos sobre el tamaño, peso y sexo. Se toma-

ron 100 muestras de plancton en las bahías para inferir la

composición de la dieta.

Resultados: Las rayas mostraron un comportamiento

de natación repetitivo paralelo a la playa, alimentándose

exclusivamente en la zona de rompimiento de las olas en

marea baja, a menos de 50 cm de profundidad. Un total de

12 rayas M. munkiana (11 vivas y una encontrada muerta)

indicaron una agregación de juveniles para alimentarse.

Los anchos de disco variaron de 490 a 610 mm y el peso

entre 1400 a 2300 g. La proporción sexual (machos:

hembras) fue de 3:1. En la zona donde rompían las olas se

encontró principalmente el orden Mysidaceae.

Conclusiones: El comportamiento específico y la ocu-

rrencia estacional de M. munkiana en la zona de estudio

parecen estar impulsados por la abundancia de presas. Se

necesita más investigación para concluir la presencia de

adultos reproductivos a mayor profundidad y sobre el uso

de hábitat en los alrededores de Punta Descartes durante

todo el año. Esta área se encuentra amenazada por un desa-

rrollo insostenible y requiere estrategias de manejo realis-

tas para garantizar la supervivencia de especies vulnerables

y sus hábitats críticos.

Palabras clave: Mobula munkiana; juveniles; rayas dia-

blo; migración; abundancia de presas; comportamiento de

alimentación.

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