Brazilian Guitarfish

Fascinating facts about the Brazilian Guitarfish

• In February, newborn Brazilian guitarfish emerge at about 29 cm long after growing from just 1 cm the previous December, showing a rapid three-month surge that packs a full year’s growth into a single season. This burst highlights how tightly timed their life cycle is to the warm inner shelf waters.
• Females don’t reach reproductive age until roughly four years old, and each pregnancy yields only four to twelve pups, far fewer than most coastal fish. Such low output makes any loss of mature females a direct hit to the species’ future.
• Although the species can reach a total length of 138 cm, most adults hover around 60 cm, meaning the giants are rare sightings on the continental shelf. Their size distribution underscores how fishing pressure has trimmed the population’s biggest members.
• From 1975 to 1984, landings at Rio Grande jumped from 842 to 1 804 tonnes, but by 2002 catches had collapsed to just 157 tonnes, a drop of over 90 % in less than two decades. The steep decline signals how quickly overfishing can push a once abundant fish toward the brink.
• The inner continental shelf serves as a nursery where both pregnant females and juveniles fall prey to pair-trawling and beach seine nets, concentrating the most vulnerable life stages in the same hotspot. This overlap explains why the species is now listed as critically endangered and why protecting those nursery grounds is vital.

At a glance

About the Brazilian Guitarfish

The Brazilian guitarfish, Pseudobatos horkelii, glides along Brazil’s continental shelf in a uniform olive-grey or brown cloak, its dorsal surface broken only by a dark snout patch and long nostrils. Adults typically reach about 60 cm, though some stretch to 138 cm, their crowns flattened or gently convex, giving them the unmistakable guitar-shaped silhouette that defines the Rhinobatidae family. These viviparous rays spend their early months hidden in the warm, shallow waters of the inner shelf, where the females nurture their embryos first from yolk sacs then from uterine secretions, producing litters of four to twelve pups that emerge in February at roughly 29 cm. After birth, the juveniles linger in these nursery grounds, only to be scattered outward as the adults disperse later in the year, a seasonal rhythm that aligns mating in March with the inner-shelf’s productive pulse. A surprising twist in their biology is the exclusive partnership with the parasitic flatworm Acanthobothrium goleketen, a “Good Luck” worm found nowhere else, hinting at a tightly woven ecological web that hinges on the guitarfish’s very presence. When the breeding season wanes, the fish migrate across the inner shelf, becoming vulnerable to pair-trawling, beach seines, and otter-trawls that target both pregnant females and juveniles. Their low fecundity, four-year maturation and modest litter sizes, means each loss reverberates through the population, a stark contrast to the abundant bounty once harvested along southern Brazil’s coast. The once-thriving catches that peaked at 1 804 tonnes in Rio Grande by 1984 have collapsed to a fraction of that, underscoring how overfishing has reshaped the species’ fate.

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