The Eastern Australian sawshark, Pristiophorus peroniensis, is a sawshark of the familyPristiophoridae, found off southeastern mainland Australia at depths of between 100 and 630 m. It can grow up to 1.36 m in length and lives along the continental shelf and upper slope from southern New South Wales to eastern Victoria, including Bass Strait. Similar to other sawsharks, it is characterized by an elongated, saw-like rostrum, or snout, with teeth that come out sideways and paired barbels. These adaptations aid the Eastern Australian Sawshark in finding and successfully hunting prey on the seafloor. The species was formally described somewhat recently in 2008 after previously being referred to as Pristiophorus sp. A. This species is now considered to be a relative of Pristiophorus cirratus[1]
It is listed as Near Threatened by the IUCN[2] due to its limited range and vulnerability to bycatch in commercial fisheries, although current management measures have helped maintain population stability.
Taxonomy and naming:
The Eastern Australian sawshark (Pristiophorus peroniensis) is a member of the family Pristiophoridae, a group of thin, bottom‑dwelling sharks distinguished by their long, saw‑like rostrum lined with sharp lateral, or sideways, teeth and a pair of sensory barbels on the underside of the snout, which they use to detect bioelectricity.[1]P. peroniensis was formally recognized as a distinct Sawshark species in 2008, having previously been referred to as Pristiophorussp. A before its scientific description. This family dates back to at least the Upper Jurassic based on fossil evidence.[3]
The genus Pristiophorus was established by Müller & Henle in 1837 and currently includes seven recognized species. The name derives from Greek roots. Pristis meaning “saw” and phoros meaning "bearing”" referring to the distinctive toothed snout.[1]
Pristiophorus peroniensis was formally described in a study done by Yearsley in 2008, Last & White after decades of being referred to informally as Pristiophorus sp. A in scientific articles and studies. Its recognition as a distinct species was based on a series of different traits in its morphology, including rostrum length, tooth counts, and barbel position, all were different enough from the common Sawshark (P. cirratus).[3]
Distribution and Habitat
The Eastern Australian sawshark is native to southeastern Australia. Its range extends from New South Wales through Eastern Victoria, dipping into Bass Strait, and possibly into Tasmanian waters. [4]
The species prefers to inhabit depths of 100 meters to 630 meters[5], which is along the continental shelf and upper slope sea region. This makes it a benthic species with the region being notably known for reduced light and temperate water. These habitats are notable for their soft substrates, such as sandy or muddy bottoms which provide cover and hunting ground. Other sawsharks, such as the Common Sawshark, prefer this habitat as they tend to do well in sandy and muddy conditions with cooler temperatures. [6]
Specific seasonal movement patterns for P. peroniensis remain sporadically documented, although related species such as the common sawshark shift depths and swim with fellow sawsharks.
Biology and Ecology
The Sawshark as a species is named after its key feature, its elongated rostrum, or snout, and rostral teeth, making it visibly different from other shark species. Based on anatomical features that match other sawsharks and even sawfish. The top of the body is fully slate gray, and the bottom of the body is fully white. They have two dorsal fins that are similar in size along their body and lack an anal fin.[5]
Sawsharks possess specialized electroreceptors called ampullae of Lorenzini,[7] which are spread out along their rostrum/snout. These electroreceptors are used to detect weak bioelectric signals given off by prey that are buried in the sand/mud. This signal allows the shark to locate food even at depths where there is minimal to no light. The rostral teeth, unlike those of sawfish, are not permanently fixed. They are replaced throughout the shark’s life because they can become worn or damaged. On each side of the snout, there are 19-25 teeth and the barbels are near the tip of the snout.[7]
This continual replacement of teeth is important for species that hunt using side-to-side slashing motions to immobilize their prey. Their flattened bodies, reduced fin height, and camouflaging coloration also help them blend into the sea floor.
Feeding Behavior
Cone beam CT imaging has revealed that Sawsharks ingest prey head-first.[8]The Eastern Australian consumes small fish, mollusks, and crustaceans and are preyed upon by larger sharks. Sometimes Sawsharks will feed in large schools, with groups of schools being separated by age range.[5] Meaning that younger sharks feed together and older sharks feed together, commonly in deeper water.
Age Range
The Australian Fisheries Management Authority states that Southern Sawsharks can live up to 9 years and Common Sawsharks can live up to 15 years, but there is no current data for the Eastern Australian Sawshark.[5]
A challenge with sawsharks is determing the age range of the species. Studies on the common sawshark show that the methods used for other sharks, such as examining growth rings in verterbrae or eye lenses, don't apply to this species. The cartilage in sawsharks calcifies slowly and lacks these clear growth markers. This makes it hard for researchers to determine the age of sawsharks the way they normally do for other species.[8] This gap in research prevents studies that assess population dynamics and effective management strategies for conservation efforts.
Reproductive Biology
When Eastern Australian Sawsharks turn 2 years old they begin to have the ability to reproduce. They are aplacental viviparous, in simpler terms, the embryos can develop inside the mother and use yolk savs for nutrition instead of the placenta. Each pregnancy can produce 5 upward to 20 pups per litter during a live birth after the gestational period, which is 12 months. The pups are typically born during winter months in shallow coastal areas. During birth, pups come out around 31-34 centimeters long with their teeth folded backward as to prevent injury to the mother.[5] These estimates are inferred from studies on related species, such as the common sawshark, with research still needed on size when the eastern australian sawshark reaches maturity, what the reproductive cycle looks like, and the survival rate of pups.
Threats and Conservation Status
On the IUCN Red List, the Eastern Australian sawshark is classified as near threatened.[2] This classification reflects the species restricted range and susceptibility to fishing activities. The primary threat to the species is bycatch in commercial fisheries, especially in trawl and gillnet operations that target fish. Sawsharks are not the intended catch but they are kept for their meat which is sold in Australia.[5] Continued fishing pressure and accidental capture pose persistent risks to population stability.[4]
Conservation Measures
In an effort to mitigate these risks Australia has implemented several fishing management strategies. These include Total Allow Catch (TAC), which limits the amount to 525 tonnes.[4] Regular stock assessment is also done by the Status of Australian Fish Stocks. Current assessments show that sawshark populations are stable under these new management efforts. However, the lack of research on population structure aids the notion that continued monitoring and research must be done to prevent the species from moving to a higher IUCN threat catergory.
Research and Knowledge Gaps
There have been recent advances in understanding sawshark biology however significant gaps remain regarding the reproductive biology, population dynamics, age range, and more of the Eastern Australian Sawshark. Most studies currently done are on the common sawshark, highlighting the need for research specifically for the Eastern Australian sawshark.[8] Addressing these knowledge and research gaps are important in informing ongoing conservation efforts and continued fisheries management as the species is still vulnerable to bycatch in commercial fisheries.
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