Stenocionops ovatus

Stenocionops ovatus is an eastern Pacific spider crab, originally described as Pericera ovata and now placed in the family Epialtidae ^[1]. The IMARPE catalogue of decapod crustaceans gives its range as Baja California, in Mexico, to Paita, in Peru, plus the Galápagos Islands ^[2].

It lives on sand and mud bottoms and on substrates of coral, shell, algae or sponges, between 15 and 275 m deep ^[2]. Its biology is known mainly from a Gulf of California sample, in which males outnumbered females and females carrying eggs appeared in October and November ^[3].

According to the Peruvian catalogue, the body is dusty pink, with a reddish-brown to dark brown pubescence on the carapace, almost black on the walking legs, and white carapace spines with reddish tones ^[2].

Males are larger than females. In the Gulf of California, females measured 65.6 to 88.5 mm in carapace width and males 63 to 140 mm; in carapace length, females measured 71.5 to 103.4 mm and males 74.2 to 153.1 mm ^[3]. In weight, females ranged from 93.4 to 231.7 g and males from 100 to 1500 g ^[3].

The authors of that study concluded that the species shows sexual dimorphism in size and weight, already recognised before, and recorded a male 140 mm wide, 9.5 mm more than the largest size known until then ^[3]. The Peruvian specimens examined in the catalogue, from Puerto Pizarro, measured 36.8 to 38.55 mm in carapace length for the 4 males and 33.1 to 45.2 mm for the 9 females ^[2].

The Peruvian catalogue gives the distribution as Baja California, in Mexico, to Paita, in Peru, and the Galápagos Islands, in Ecuador ^[2]. Its habitat is sandy and muddy bottoms and substrates of coral, shell, algae or sponges, between 15 and 275 m ^[2].

In the Gulf of California it was caught with monofilament gill nets of 6 inch mesh at 180 m depth, off Isla Danzante, between October 1993 and January 1994 ^[3]. The authors note that this species and another spider crab live in deep water on the continental shelf and are hard to collect, and they cite that Stenocionops ovatus is abundant north of Isla Tiburón, in Sonora ^[3].

In a sample of 433 individuals from the Gulf of California there were 338 males and 95 females, a ratio of 3.5 males per female that differs significantly from 1:1 ^[3].

Females carrying egg masses were present only in October and November, with a frequency of 98.9 % ^[3]. The authors note that an earlier work had recorded breeding of the species in the Gulf of California in April ^[3].

The SeaLifeBase record states that the species has not been evaluated under CITES ^[4].

The Gulf of California specimens studied by Villalejo-Fuerte and colleagues were incidental catches in gill nets ^[3]. These authors regard the malacostracan crustaceans of that region as a potentially important but little studied fishery resource ^[3]. In Peru, the IMARPE catalogue mentions no use of the species ^[2].

The IMARPE catalogue, published in 2012, examined specimens collected in January 1987 near the fishing terminal of Puerto Pizarro, and gives Paita as the southern limit of the range ^[2]. The same catalogue gives a depth of 15 to 275 m, an interval that reaches well below recreational diving depths; none of the sources consulted describes sightings of the species by divers ^[2].