#pristiformes

[todropscience]

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

Reference (Open Access): Mendoza et al, 2017.  The Largetooth Sawfish, Pristis pristis (Linnaeus, 1758), is not extirpated from Peru: new records from Tumbes.  Check List

[todropscience]

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.  

Reference (Open Access): Morgan et al. 2016. What is the fate of amputee sawfish?" Fisheries

[extraordinaryspecies-blog-blog]

Name: Smalltooth sawfish (Pristis pectinata) Phylum: Chordata Class: Chondrichthyes Order: Pristiformes   Family: Pristidae   Region:  It is found in shallow tropical and subtropical waters in coastal parts of the Atlantic, including the Mediterranean. Risk of Extinction: Critically Endangered. More Info: The many teeth of a sawfish’s saw are not actually teeth at all, but rather special types of scales known a dermal denticles.These protruding weapons, combined with the animal’s ability to strike from side to side with great force, provide it with a powerful and efficient defense mechanism. Although the saw is mainly used for feeding purposes, observations of sawfish in captivity sow that they may also be used for self-defense. (photo taken from http://www.flmnh.ufl.edu/fish/education/questions/sawfishbasics.html)

[scientificillustration]

n270_w1150 by BioDivLibrary on Flickr.

[dailyelasmobranch]

Largetooth sawfish - Pristis microdon

Though their bodies resemble that of a shark, sawfish are a family of rays. The largetooth (or freshwater) sawfish is found in the tropical waters of the Indo-West Pacific, inhabiting the sandy or muddy bottoms of shallow coastal waters, estuaries, and even lakes, with some individuals spending their entire lives in freshwater. The rostrum, or "saw", features 12 to 22 large "teeth" on either side - teeth that, unlike those of sharks, are deeply embedded in their cartilaginous sockets - and can be used for digging for benthic invertebrates in the substrate as well as disabling schooling fish. Adults can achieve a maximum size of 21.5 feet. As with all species of sawfish, this species is listed on the IUCN Red List as Critically Endangered. Not only is it particularly prone to entanglement fishing gear and habitat destruction, the saw is valued worldwide as a souvenir or trophy. Extensive mythology surrounds the sawfish throughout its range: They have been regarded as totems and symbols of warfare, with weapons fashioned out of the rostrum and sawfish emblems adorning WWII vessels, and sawfish parts are in high demand in the Asian medicine and shark fin trades.