First record of Pseudocaranx chilensis (Carangidae) from the continental coast of north-central Chile

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First record of Pseudocaranx chilensis (Carangidae) from the continental coast of north-central Chile

by

Philippe Béarez

^*

(1) & César Villaroel (2)

Cybium 2018, 42(3): 303-305.

Ichthyological note

Received: 25 Dec. 2017 Accepted: 13 May 2018 Editor: R. Causse

Résumé. – Nouveau signalement de Pseudocaranx chilensis (Carangidae) sur les côtes continentales du nord du Chili.

la carangue chilienne Pseudocaranx chilensis est une espèce côtière des îles océaniques situées au large du Chili. elle est consi- dérée comme étant endémique des îles Juan Fernández et Desven- turadas. Cette note présente le premier signalement de cette espèce autour de l’île Chañaral, située à proximité du continent sur la côte centre-nord du Chili, ce qui constitue une extension de sa distribution géographique d’environ 850 km vers l’est. l’observation sous- marine de plusieurs individus errants pourrait résulter d’une migra- tion de larves de ce poisson depuis les îles Juan Fernández.

Key words. – Southeastern Pacific – New record – Chile – Chañar- al island – Pseudocaranx chilensis – Vagrant.

The family Carangidae is poorly represented along the Pacif- ic coast of continental Chile. Under “normal” conditions, i.e. non el Niño / la Niña years, only three species of carangids occur in the mainland Chilean waters: Trachinotus paitensis Cuvier, 1832;

Trachurus murphyi Nichols, 1920; and Seriola lalandi Valenci- ennes, 1833. The first is a tropical eastern Pacific species, some- times caught in northern Chile, south to antofagasta (Medina et al., 2004). The second is distributed from ecuador to Chile and constitutes a major fishery resource. In Chile, it can be found from Arica (18°20’S) to Chiloé island (42°S) (arcos et al., 2001). The third species is mostly caught off northern Chile (between Iquique and Coquimbo, 20°-30°S) during the austral spring and summer sea- sons. The last two species are transpacific and are also found near the oceanic islands belonging to insular Chile and west across to New Zealand (Pequeño and Sáez, 2000). The connectivity of their populations is probably maintained across the southern Pacific (see Vásquez et al., 2013; Martinez-Takeshita et al., 2015).

The Juan Fernández trevally, Pseudocaranx chilensis (Guichenot, 1848), is considered endemic to the Desventuradas and Juan Fernández Islands, from where it was described (Fig. 1). It is a coastal pelagic species commonly caught off the islands, where it constitutes a prize catch due to its large size of up to 65 cm total length (Dyer and Westneat, 2010).

Here we report the sighting of a group of 6 to 8 individuals Pseudocaranx chilensis off Chañaral island (29°02’S-71°35’W); a small island located about 6 km off the mainland coast of north- central Chile.

Results and disCussion

The Pseudocaranx chilensis individuals (Fig. 2) were observed off the northeastern part of the island on the 19^th april 2015. a group of 6 to 8 fish were swimming in shallow water 2 to 6 m deep.

They were probably still juveniles or subadults since their approxi- mate size were around 20 cm total length. Little biological informa- tion is available for P. chilensis, but size at first maturity (L50) for Pseudocaranx dentex (Bloch & Schneider, 1801) in the azores is

(1) Archéozoologie, archéobotanique : sociétés, pratiques et environnements (UMR 7209). Sorbonne Université, MNHN, CNRS, Muséum national d’Histoire naturelle, 55 rue Buffon, 75005 Paris, France.

(2) explorasub, Chañaral, Chile. [cvillarroel@explorasub.cl]

* Corresponding author [bearez@mnhn.fr]

Figure 1. – Original drawing of Pseudocaranx chilensis from the descrip-

tion of Guichenot (1848). Figure 2. – individual Pseudocaranx chilensis swimming over the kelp bed at Chañaral island (depth ~ 5 m).

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First record of Pseudocaranx chilensis from coastal north-central Chile Béarez& Villaroel

304 Cybium 2018, 42(3)

as follows (Afonso et al., 2008): male L50 = 27.8 cm fork length, female L50 = 30.0 cm fork length.

The specimens are characterized by the presence of two sepa- rate dorsal fins and by conspicuous scutes on the posterior part of the lateral line; a lateral line with a weak and extended anterior arch, with junction of curved and straight parts of lateral line below the middle (vertical from twelfth to fourteenth soft rays) of the second dorsal fin. The colour of the body is pale yellowish to steely blue dorsally, silvery below; a yellow stripe is present along the sides, wider over the straight part of the lateral line; dusky yellow cau- dal fin, soft dorsal and anal fins; a diffuse black spot on the upper margin of the opercle (see video available at http://sfi-cybium.fr/fr/

first-record-pseudocaranx-chilensis-carangidae-continental-coast- north-central-chile).

Pseudocaranx chilensis is a subtropical to temperate spe- cies that has been described from the Juan Fernández islands (Guichenot, 1848), and until now it has been considered as absent from continental Chile (Pequeño, 1989, 1997). Hence, the young specimens observed at Chañaral island, located only 6 km off the coast, most likely come from the Chilean oceanic islands, either the Desventuradas or Juan Fernández islands (Fig. 3).

The Juan Fernández islands are situated ca 650 km off the coast of Chile, west of Valparaíso. They are composed of three main volcanic islands: Robinson Crusoe (33°40’S-78°50’W), the closest to the mainland, alejandro Selkirk and Santa Clara. The Desventuradas islands are a group of four small islands located ca 900 km off the coast of Chile, east of Caldera. San ambrosio (26°20’S-79°53’W) is the largest and closest island. Both groups of islands are quite far from the mainland, and are located at more or less equal distance from the Chañaral island (29°02’S-71°35’W):

ca 850 km.

The main superficial current in the area is the Humboldt Current that drives cold water from the Antarctic region northward, parallel to the coast, creating a strong biogeographic barrier between these islands and the continent (Thiel et al., 2007; Friedlander et al., 2016). No eastward current exists between the Desventuradas, the Juan Fernández Islands and the mainland, which would allow spe-

cies transportation across the flow of the Humboldt Current. The ichthyofaunas of these islands are comprised of a mixture of subtropical and temperate taxa, more similar to western than eastern South Pacific fauna (Pequeño and Lamilla, 2000; Pérez-Matus et al., 2014; Friedlander et al., 2016). also, both island groups have more affinity and overlap between them than with the continent (Pequeño, 2000; Pequeño and Sáez, 2000), suggesting that these two island groups should be considered as a single biogeographic unit (Dyer and Westneat, 2010).

How the recently observed P. chilensis arrived at Chañaral island is not clear. adults are not long-distance foragers (afonso et al., 2008); therefore, since the observed individuals were still juve- niles or subadults, it seems likely that they arrived through larval transport and grew once settled near the island. Unfortunately, no information is available for the pelagic larval duration for this species and little is known at the genus level.

Where they came from is also not clear; but, it seems that Pseudocaranx chilensis is much more common in the Juan Fern- ández Islands where it represents a good part (20%) of the biomass (Arana, 2000; Ramírez et al., 2013; Friedlander et al., 2016). also, the northeastward drift (Dyer and Westneat, 2010: fig. 2; Andrade et al., 2014) would most likely have transported the fish larvae from the Juan Fernández Islands to Chañaral Island. It is noteworthy to mention here that vagrant Juan Fernández fur seals have been found on the west coast of South America, from southern Peru to southern Chile (osman, 2007).

The observation of Pseudocaranx chilensis likely represents vagrant individuals. However, these vagrants demonstrate that species exchanges are possible between the subtropical oceanic islands and the temperate mainland coast, and could be indicators of a potential future colonisation, by this species, of the mainland coast of Chile. Climate-driven changes are often responsible for geo- graphic range shifts in fish (Stuart-Smith et al., 2016), which could be part of the explanation. Slight changes to marine currents and small sea temperature increases could facilitate the eastward trans- port of larval P. chilensis and the recruitment of juveniles along the mainland coast, if suitable habitats and temperature regimes were encountered. Their survival at Chañaral Island, which seems to be a recent event, might, therefore, be linked to climate change. Since Chañaral island is part of the Humboldt Penguin National reserve, it would be worth monitoring the presence of P. chilensis around the island to observe if a population is about to settle.

acknowledgements. – The authors thank laurie Bouffandeau for her help with the drawing of the map, Jill Cucchi for copy-editing, and an anony- mous reviewer for his comments.

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Figure 3. – Map of north-central Chile showing the oceanic islands and Chañaral Island where Pseudocaranx chilensis was sighted.

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Béarez& Villaroel First record of Pseudocaranx chilensis from coastal north-central Chile

Cybium 2018, 42(3) 305

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