About Myxus elongatus Günther, 1861
Myxus elongatus, commonly called the sand grey mullet, is a mullet species that shares the general body characteristics of other mullets. It has a terminal mouth with thick lips, two dorsal fins, and a lunate homocercal caudal fin, meaning its upper and lower caudal fin lobes are equal in length. It lacks a lateral line organ, the structure most fish use to detect changes in their surrounding environment. Its cycloid scales, which have a smooth outer edge, are thin, flexible, and overlapping. The body has a mixed silver and grey color scheme, and the species is easily identifiable by its bright yellow eyes. It has a bony skeleton and a streamlined body shape that supports the body undulations needed for fast swimming. As constant swimmers, sand grey mullets require large amounts of oxygen. They get oxygen through gills (instead of lungs), which have a large surface area thanks to the many grooves in their gill tissue. Water passes over the gills, and oxygen is absorbed as water is pushed out through the pharynx during exhalation. Blood flows in the opposite direction of water moving over the gills, a countercurrent exchange that lets the fish remove the maximum possible amount of oxygen from the water. Sand grey mullets use a swim bladder to adjust buoyancy: they change the volume of gas inside the bladder to maintain a constant overall bladder volume at different depths. When cooked, this species is known for its texture and strong fish flavor. Sand grey mullets reach full mature size and reproductive maturity at 2 to 3 years of age. Growth differs between sexes: females are typically longer, averaging 255 mm (10.0 in), while males average 230 mm (9.1 in) in length. The maximum recorded total length for the species is 900 mm (35 in). The sand grey mullet is found in temperate regions of Australia, where it inhabits fresh waters and estuarine areas at depths between 1 and 10 m (0 to 30 ft). It is a wild fish that travels in structured schools: fish swim together in a group with no obvious leader, maintain consistent distance between one another, and start and stop moving at the same time. This schooling behavior is thought to reduce individual risk of predation by confusing predators, lowering the probability that any single fish will be eaten. The sand grey mullet is targeted by both commercial and recreational fishing, for its meat and for use as bait. Fishing rules for this species are not strict, and only regulate the acceptable mesh size of fishing nets. Spawning occurs from November to March, with a peak spawning season from January to March that varies based on the fish's location. The shape and color of the species' reproductive organs change depending on their developmental stage. As fish mature, their reproductive organs become thinner. While many ray-finned fish species are hermaphroditic, it is unknown whether this is the case for sand grey mullets. Sand grey mullets only spawn in ocean waters, releasing eggs directly into the water column, and provide little to no parental care for eggs. Most individuals die during the early stages of life, but once fully developed, the species has a low mortality rate.
