Shortnose Guitarfish

Fascinating facts about the Shortnose Guitarfish

• From the sandy coasts of southeastern Brazil down to northeast Argentina, the shortnose guitarfish lives on soft bottoms no deeper than about 50 m, making it a true inshore dweller. Occasionally they wander as far as the Falkland Islands, likely riding Brazil’s summer currents. Their limited depth range ties them closely to coastal habitats that are increasingly squeezed by fisheries.
• Females average 66.1 cm in length while males are slightly shorter at 63.5 cm, yet both sexes reach sexual maturity at roughly the same size, about 42 cm for females and 43.7 cm for males. The larger adult size of females comes from slower growth rather than a higher growth rate. This pattern shows how a modest size difference can mask very different life-history strategies.
• Young guitarfish gobble up amphipods and small worms, but as they grow they swap those for harder prey like isopods, decapods and polychaetes. They even spit out bones and exoskeletons after a meal, a built-in cleaning system. The shift in diet illustrates how a single species can occupy multiple feeding niches as it ages.
• Gestation lasts between 9 and 12 months, after which a female gives birth to up to eight pups each autumn. If a pregnant female is caught, all her embryos abort and most of the mothers later die, turning routine fishing into a hidden reproductive disaster. This sensitivity makes every capture a direct blow to the species’ ability to rebound.
• Unlike many fish, the shortnose guitarfish can breathe while standing still by actively pumping water over its gills, yet it also uses ram ventilation when swimming with its mouth slightly open. Stress triggers rapid breathing, eye retraction for seconds, and in extreme cases spiracles shut completely for minutes. These physiological alarms reveal just how fragile the animal is when forced into nets or handling.

At a glance

About the Shortnose Guitarfish

Gliding just above the soft, sandy seafloor of the southwest Atlantic, the shortnose guitarfish (Zapteryx brevirostris) presents a sleek, heart-shaped disc edged with a broad, obtuse snout. Females average 66.1 cm in length, males slightly smaller at 63.5 cm, and their backs shimmer in shades of brownish-gray to olive, blending seamlessly with the benthic backdrop. These benthic inshore dwellers favor depths to about 50 metres, ranging from the coastal sands of southeastern Brazil, through Uruguay, to northeast Argentina, with occasional wanderings as far south as the Falkland Islands, likely driven by Brazil’s summer currents. Their diet shifts with size: juveniles sift amphipods and tiny clams from the substrate, while larger individuals favor isopods, decapods and polychaetes, even regurgitating meals to discard indigestible shells and bones. A surprising trait is their dual breathing strategy, while many rays must keep moving, the shortnose can pump water through its gills while stationary (active ventilation) and also employ obligate ram ventilation when swimming with a slightly open mouth, a flexibility that supports its sedentary, sand-buried lifestyle. Reproduction is a slow, delicate affair. After a gestation of nine to twelve months, females give birth to up to eight pups in autumn, each newborn emerging onto the sand-like substrate that is crucial for their early survival. Growth is sluggish; females reach sexual maturity at about 42 cm, males at 43.7 cm, and both sexes grow slowly thereafter. Stress responses are stark: when captured, they may hyperventilate, close their spiracles, or even abort embryos, an acute reaction that underscores their vulnerability. Their spiracles not only aid ventilation but also generate weak electric fields that play a role in mating, a subtle yet fascinating facet of their biology.

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