Blotched stingray

Urotrygon chilensis is a small ray of the family Urotrygonidae, in the order Myliobatiformes ^[1]. It lives on shallow coastal sandy bottoms, mostly between 10 and 60 m deep ^[2], and ranges from the Gulf of California to Chile ^[3]. The checklist of chondrichthyans of the Peruvian sea includes it ^[4]. It is not the target of a directed fishery, but it is often caught in trawls and bottom gillnets ^[3], and its global category on the IUCN Red List is Near Threatened ^[5].

It is a ray with a roughly rhomboid disc that is wider than long, with straight front edges and rounded side and rear edges that cover half of the pelvic fins ^[3]. The eyes and spiracles are the same size, spines run along the body to the tail, and the tail is longer than the disc ^[3]. Like most rays of its family, it has a well-developed tail fin and one or more long, venomous spines on the tail ^[3].

It is small. In the southern Gulf of California, among 606 specimens, females measured 11.4 to 51.6 cm in total length and males 11.2 to 41.3 cm ^[6]. In the central and southern Mexican Pacific, 423 specimens measured 6.3 to 47.3 cm ^[3].

6 species of the genus Urotrygon have been recorded in Peru, and the country's chondrichthyan checklist includes this one on the basis of the 2001 catalogue by Chirichigno and Cornejo ^[4].

It ranges from the Gulf of California to Chile ^[3], and the updated checklist of chondrichthyans of the Peruvian sea includes it ^[4]. The specimens studied in the southern Gulf of California came from shrimp trawls and from small-scale gillnet fishing, at depths of 3 to 41 m ^[6].

It lives mostly on shallow coastal sandy bottoms, between 10 and 60 m ^[2]. The round rays of its family are mostly benthic and inhabit soft bottoms of estuaries and bays, in tropical and temperate waters ^[3].

It is an aplacental live-bearing ray whose embryos receive food from the mother during gestation (matrotrophic development) ^[2]. In the southern Gulf of California, the size at which half of the individuals were mature was 27.5 cm in females and 25.3 cm in males, and females reached a larger size than males ^[6].

Gestation was estimated at 6 months, and the presence of pregnant females, the size of oocytes and embryos and the smallest young across the year point to 2 reproductive periods a year; pups are born at 11.2 to 15.6 cm in total length ^[6]. Mean fecundity was 2.14 embryos per female and the maximum was 6, in a female of 51.6 cm ^[6]. These figures, the size at maturity and the reproductive cycle differ between regions of the Mexican Pacific, which suggests separate populations ^[6].

In the southeastern Mexican Pacific, the ages of 696 specimens were read from vertebral sections: females were 0 to 14 years old and males 0 to 12, and growth bands form once a year ^[2]. The authors conclude that it is a slow-growing species with a relatively short life compared with other elasmobranchs ^[2].

In the Mexican Pacific, 423 stomachs examined yielded 15 prey groups, mostly crustaceans, followed by fishes and molluscs ^[3]. In Sinaloa, small burrowing crustaceans dominated: peracarids with 38.4 % and cladocerans with 29.3 % of the index of relative importance, followed by polychaetes with 22.7 % ^[3]. In Michoacán and Guerrero, by contrast, penaeid shrimps made up about 60 % of the index (64.6 % and 58.3 %), again followed by polychaetes ^[3].

Of the stomachs, 58.6 % were empty ^[3]. Its trophic position estimated from stomach contents was 3.51 in the north and 3.56 in the south, and the authors describe it as a specialist predator that changes prey according to what is available, a mesopredator of soft bottoms ^[3].

Its global category on the IUCN Red List is Near Threatened ^[5].

There is no directed fishery for this ray, but it is caught incidentally in trawls and bottom gillnets ^[3]. In the Mexican Pacific it is an abundant bycatch of the shrimp trawl fishery and is almost always discarded because it has no commercial value, so there are no landing records ^[6]. The authors note that its abundance does not appear to be affected despite the catches, perhaps because of an r-type life strategy ^[6].

It has no commercial value in the Mexican Pacific, where it is discarded, although that country's small-scale fishery has turned toward batoids since shark catches fell ^[6],[3].