Southern Banded Guitarfish

Zapteryx xyster is a guitarfish of tropical waters in the eastern Pacific, for which a range from Mexico to Peru is cited ^[1]. In northern Peru it has been seen in very shallow water, 1 to 6 m deep, resting buried in the sand ^[2]. It is caught incidentally by fisheries, and little is known about its biology ^[1].

It is described as a tropical-water species with a range cited from Mexico to Peru ^[1]. In the Colombian Pacific it was caught at 30 to 45 m depth during shrimp-trawl hauls ^[1]. In the Gulf of Tehuantepec, Mexico, adults move into shallower water, 25 to 37 m, to reproduce ^[3].

At Los Órganos, in the Piura region, a survey in 2016, 2017 and 2019 recorded it at 1 to 6 m depth, in a mixed habitat of fine sand, rocks, a reef built by the polychaete Phragmatopoma, and Caulerpa or Ulva vegetation ^[2]. In the months sampled, sea surface temperature ran from 19 °C in August, the cold season, to 26 °C in January, the warm one ^[2]. The authors note that earlier trawl studies did not sample shallower than 18 or 19 m, so their data, taken closer inshore, offer unique information ^[2].

In the Colombian Pacific, 55 specimens measured 27 to 66 cm total length, with an estimated asymptotic length of 69.8 cm and a sex ratio of 1:1 ^[1]. The length-weight relationship was isometric (b = 2.85) ^[1]. That study found no gravid female, and overlapping sizes between maturity stages prevented inferring a minimum size at reproduction ^[1].

In the Gulf of Tehuantepec, between January 2008 and December 2009, 451 specimens were measured: males matured at 44 cm total length and females at 48 cm ^[3]. Each female cycle lasted 2 years, with yolk deposition and gestation following one another; litters were 5 to 8 embryos (mean of 6), and births took place in April and May, at a mean length of 17.3 cm at birth ^[3].

In Costa Rica, between 2010 and 2011, the female cycle had a reproductive peak in June and July, and most neonates and gravid females appeared in December and January ^[4]. Gestation there was estimated at 4 to 6 months ^[4]. In northern Peru, a 54 cm female taken to an aquarium gave birth to 6 pups ^[2].

In Costa Rica, 235 stomachs were analysed, collected between March 2010 and December 2011; shrimps were the most important prey (52.3% of the prey-specific index of relative importance), followed by bony fishes (27.2%) ^[5]. Juveniles ate mostly small shrimps of the genus Solenocera, and adults shifted to larger prey ^[5].

In the Colombian Pacific, shrimps of the family Penaeidae were the main food (index of relative importance of 1126), followed by perciform fishes (667), the stomatopod Squilla panamensis (560) and tonguefishes of the family Cynoglossidae (300) ^[1]. Given that variety of prey, the authors consider that it could be classed as a generalist ^[1].

Results on its daily rhythm differ. In Colombia, 92.7% of the specimens were caught at night, between 20:00 and 03:00 h ^[1]. In Costa Rica, by contrast, the amount of food in stomachs rose between 04:00 and 12:00 h, which contradicted the hypothesis of greater night-time activity ^[5]. At Los Órganos, all records showed it inactive and partly or fully buried in the sand in the morning ^[2].

The species is listed as Vulnerable (VU) on the IUCN Red List, according to version 2022-2 as cited by researchers working in northern Peru ^[2]. These authors note that Zapteryx xyster is one of four vulnerable species, out of five they recorded, caught by artisanal fishing or the industrial trawl fishery, with limited or no management plans ^[2].

In the Colombian Pacific the catch rate was 0.679 individuals per hour of trawling and the density 0.02 individuals per km², low figures that the authors attribute possibly to the heavy fishing effort in the area ^[1]. In Mexico, the authors of the Tehuantepec study conclude that fishing gear taking the animals by chance while they court and mate puts the species' survival at risk ^[3]. For Costa Rica, reducing fishing pressure in June and July, when mating occurs, and in December and January, when pups are born, is recommended ^[4].

In Colombia it has no commercial value, but it is caught incidentally in artisanal and industrial fishing ^[1]. In Costa Rica it occurs in the bycatch of shrimp trawling, and juveniles overlap spatially with the areas of that fishery ^[5]. In Peru, the literature places it among the species caught by artisanal fishing or industrial trawling ^[2].

The only published in-water observation of the species in Peru that we have been able to review comes from Los Órganos, in Piura. Between 2016 and 2019, 20 sampling trips were made there using surface diving at 1 to 6 m depth between 7:00 and 12:00 h, and 22 specimens were recorded, mostly adult females, resting and buried in the sand ^[2]. The authors describe these records as preliminary and propose studying whether the area serves as a gestation ground ^[2].