Date: July 2nd, 2:40
Today's fish of the day is the slender sunfish!
The slender sunfish, known by the scientific name Ranzania laevis, is the only remaining sunfish in the Ranzania genus. Found worldwide around the tropical and subtropical areas, form a range of 71°North to 55°South. Found from a depth of 1-140 meters, these fish spend all of their time on the epipelagic zone. Despite this, these fish are considered incredibly elusive, finding ways to dodge humans as often as they can, as such most research on these fish comes from stranded fish along the Australian coast. In particular across multiple strandings along the Southern Australian coast. Of which only very few specimens are able to be returned to the ocean from.
Unlike their close relatives, the mola sunfishes, the slender sunfish is incredibly small. Growing only 100cm in length at maximum, as opposed to their cousins, which can grow upwards of 5 meters. This however is to the slender sunfish's benefit, as they are the only fast moving marine sunfish. The other remaining 5 sunfish species are all rather slow moving, consuming only plankton and jellyfish, the slender sunfish however has chosen a far more difficult pathway. Instead consuming squid, which are known for their speed and agility. I can find no information about known predators of the slender sunfish, although their skin is far thinner than that of their relatives, and thus it's likely they're predated on by marine mammals and large sharks.
There is little to no info about the reproduction of the slender sunfish, and no information about lifecycle or lifespan. However, if we assume that the slender sunfish breeds similarly to the common ocean sunfish (Mola mola) then we can assume that they release eggs into the water to be externally fertilized, and become plankton, floating until they mature and hatch into fry. As the slender sunfish ages, it will begin to lose the caudal tail it is born with, slowly fusing into a clavas, which helps them move faster in the water. Marine sunfish are not known for their speed, and for years it was thought that Mola's had no ability to move of their own accord, but were rather being propelled by the water. This misinformation goes hand in hand with the idea that when these sunfish bask at the surface of the water, they are stuck. However, this behavior is done to entice cleanerfish, and seabirds, such that they may remove and eat the skin parasites collected by the sunfish over time. Molas can swim with their anal and dorsal fins, using the pectoral fins as stabilizers. These fish are even able to control the angle and force it produces well swimming! Similar to how bird wings work! Sunfish may also steer themselves with strong jets of water shot from the mouth. Which is possibly why the mouth is fused open permanently by the shape of their hardened beak.
That's the slender sunfish, everybody! I hope you enjoyed learning about them!