Date:August 19th 8:00am
Happy Tuesday, everyone! Today's fish of the day is the sixgill sawshark!
The sixgill sawshark, also known by scientific name Pilotrema warreni, is a rare subtropical shark. Found in and around the Western Indian ocean close to the upper continental shelf of Southern Africa. Their range particularly stretches around South Africa to Madagascar. Found from a depth of 15-500 meters, although pups are found closer to the surface, as well as birthing mothers, and they will descend deeper into the water column as they age.This shark was once believed to be the only fish in the genus PIlotrema, which can be split into pleion, meaning more, and trema, meaning hole. Defined by their 6 gill slits, making them, for many years, the only shark outside of the Hexanchiformes sharks to possess more than 5 gills. At least, until 2020 when another 2 species in the genus were found; Anna's sixgill sawshark, and Kaja's sixgill sawshark respectively.
Like most sharks, the sixgill sawshark is a carnivore, with a diet made up primarily of small fish, although they're not opposed to the occasional crustacean, or squid. Equipped with electro sensors along the head, as well as barbels that extend down the head and rostrum, making these sharks particularly sensitive to the location of food sources. Once prey is located, these sharks will use the rostrum or "saw" to slice at, stun, and incapacitate prey. This method allows these sharks to get rather large for their family, with female sharks growing to 136cm maximum, and males reaching 112cm. However, despite being large for their family, these are still rather small sharks for the area, and they must remain vigilant, as tiger, and bull sharks have been seen catching and consuming the sixgill.
Little is known about sawshark reproduction, beyond that they are ovoviviparous, and have 5-7 young per litter. 7-17 eggs are developed each pregnancy, but only a few will survive the womb, or the birth. Current data implies that these sharks breed annually, although there is no information as to courtship, we are aware that mothers will ascend to 5-50meters to give birth, where the pups will already be a whopping 35cm. These pups are then abandoned and left to age, descending as they grow, and hunting for larger fish. Maturity will occur at a size of 83cm for male sixgill, whereas females must reach 110cm, often taking multiple years. After this there is no information about their longevity, although it is suspected they likely live around 5-7 years, similar to other sharks in their family.
That's the sixgill sawshark, everybody! have a wonderful day!
Sources
“Plitrema Warreni.” Worms - World Register of Marine Species - Pliotrema Warreni Regan, 1906, www.marinespecies.org/aphia.php?p=taxdetails&id=217372.
Six-Gill Sawshark | Pliotrema Warreni | Shark Database, www.sharkwater.com/shark-database/sharks/six-gill-sawshark/.
“Sixgill Sawsharks ~ Marinebio Conservation Society.” MarineBio Conservation Society, 21 May 2025, www.marinebio.org/species/sixgill-sawsharks/pliotrema-warreni/
“Pliotrema Warreni Summary Page.” FishBase, www.fishbase.se/summary/Pliotrema-warreni.