as the estuary in south-east Queensland, and will then return to the open sea after a while (Pham, 2002). Spawning in the subtropical waters of southern Queensland during late winter and early spring helps the fish expand the amount of habitat accessible to each species, which maximises their potential population sizes. Importance to humans The glassy sprat is not used for commercial or recreational purposes. It is not used as an ornamental fish. Vulnerability Glassy sprats' vulnerability traits include close association with threatened taxa and threatened habitat. They follow a narrow depth range and restricted horizontal distribution, making their habitat particularly vulnerable to human destruction. One of its other vulnerability characteristics is being a bycatch in commercial fisheries. They have been found in the bycatch of the Moreton Bay prawn trawl fishery (Robins-Troeger, 1994) and are one of the species that make up less than 1% of the bycatch in the NSW Ocean Hauling Fishery. Since glassy sprats move between estuaries and utilise the area for food and shelter, particularly during the larvae and juvenile phase, their vulnerability to impacts expands as a few estuaries in the Northern Catchment Management Authority have been categorised as "modified" or "extremely modified." Differences and similarities between glassy sprat and sandy sprat The sandy sprat and the glassy sprat are the two species of the genus Hyperlophus, and similarities and differences are present between the two species. Differences Similarities a. Vulnerability and Distribution Both the sandy sprat and the glassy sprat are found in shallow sandy areas of bays and estuaries. Both have been classified as "Least Concern" by IUCN, and they pose no threat to humans. b. Biology Both the sandy sprat and the glassy sprat have a fairly elongated body. Both of them have a paddle-shaped second supramaxilla, where the lower portion is larger. Both of their eggs are delicate and transparent. In the transforming larvae of both the sandy sprat and the glassy sprat, several small melanophores develop in the anterior portion of the midbrain and on the jaws. Juveniles of both species have many small melanophores over the upper portion of their trunk and tail and along the dorsal fin rays. Their bodies thicken as they get older in both the sandy sprat and the glassy sprat, which gradually obscures the melanophores along the gut and over the swim bladder in transforming larvae. They are not visible in juveniles. References