#pristiformes

LARGETOOTH SAWFISH ESCAPE LOCAL EXTINCTION IN PERU

The Largetooth Sawfish (Pristis pristis), was for a long time considered extirpated from Peru. But things seem to be different today. Peruvian researchers recently reported the capture of two individuals from the north coast of Peru, indicating that this species is still extant in Peruvian waters. 

Largetooth sawfish is found worldwide in tropical and subtropical coastal regions, but also enters freshwater. It has declined drastically and is considered critically endangered. Gillnets are still a major threat for the species as both specimens were incidentally captured with this gear.

In Peru, the last year that sawfishes were observed was 1999. An the recent captured both individuals were adult-sized and their encounters occurred during the austral summer, which could indicate a seasonal presence in those waters. The three reports of sawfish are from the same area, the distribution of this species in Peru would seem to extend from the Ecuadorian border to Cabo Blanco in North Perú.

Researchers  highlight the need to identify and protect critical habitats that could contribute to sawfish conservation, awareness, and legal protection of this species in Peru.

Photo by Nigel Downing

WHAT IS THE FATE OF AMPUTEE SAWFISH?

The sawfishes (Pristiformes) are the most threatened shark or ray family,  which is largely due to overfishing. Their saws (a large, tooth-lined rostrum) make them particularly susceptible to net entanglement. Individuals may suffer mortality during entanglement, or be euthanised or de-sawed prior to net removal. In October 2011, Australian researchers captured an "amputee" A critically endangered green sawfish (Pristis zijsron) with a recently removed rostrum. They fitted the individual with an acoustic tag with depth and temperature sensors, and tracked its movements over a 75-day period.

The central, lighter colored section visible in the wound is the medial canal; thus, this cut exposes the brain cavity to the environment. Photo credit: David Morgan.

Compared to healthy individuals, the amputee individual had the lowest site fidelity and was more frequently detected at water depths less than 20cm. Previous findings suggest that sawfishes with damaged or removed rostrums have lower life expectancies, and these data might help explain why.

The observed differences in movement patterns and habitat use of the amputee compared to the other sawfish may reflect modifications in foraging behavior imposed by the removal of the rostrum. The amputee sawfish may have ranged more widely in order to source “easy prey”. This wide home-ranging behavior may have been a function of reduced capacity for this individual to defend itself from competitors and predators 

The conservation value of these unique species needs to be actively promoted, and the cruelty of taking rostra as trophies should be afforded the same attention as other endangered species that are similarly poached for their body parts—for example, rhinoceroses and elephants—especially because available evidence suggests that sawfish die a lingering death after rostrum removal.  

Largetooth sawfish - Pristis microdon