Marine fishes are cultured less often than freshwater species. Those living in estuarine environments are more often reared than are those requiring true oceanic conditions. Mullet are common in semitropical and tropical environments. They may be spawned to use hormones, and the fry can be reared on zooplankton. However, controlled spawning is a difficult technique to use, so fry are normally collected rather than produced in a hatchery. The fingerlings are often raised in brackish ponds with other harvestable species. The yellowtail is an important crop in Japan. Juveniles are collected in the spring and initially reared in net cages being fed fish and shrimp. For grow out they are moved to larger cages and fed trash fish and pellets. Pompano, a relative of the yellowtail, has also been considered for culture. They can be induced to mature in the laboratory and spawn with hormone treatments; young pompano can also be collected with little trouble. Small pompano are easily reared, but large-scale production of harvestable size fish has been hampered, largely because a cheap and acceptable feed has not been developed. The flatfish that have been of the greatest importance to the aquaculture community are the sole, plaice, turbot, and halibut. Spawning flatfish has been relatively simple. Larvae are fed a diet of zoo- plankton after they metamorphose to bottom fish, they may be fed fish and lusks, and are developed. Flatfish may be grown out in ponds or floating cages with hard flat bottoms Milkfish are commonly cultured in the Pacific. Fry be collected, the fish may spawn naturally in cages or tanks, or spawning can be induced with hormone treatments. The larvae feed largely on zoo-phytoplankton, but later growth is supported by larger fora (especially cyanobacteria) growing in fertilized ponds. Salmon eggs hatch in freshwater. The young fish develop and go through a smoltification that allows them to enter the oceans and grow to adults. At maturity they will return to freshwater streams to spawn. Most culturists artificially fertilize salmon eggs and hatch them like trout eggs. For all salmon, except chum and pink, the fish are held for one to two years until the smolt are ready to enter the marine environment. There are two popular methods of grow out: the salmon can be released to the sea and collected in several years when they return to spawn, or the salmon can be grown out in floating pens. Striped bass are collected during the spawning season, injected with hormones, and shipped to hatcheries. The bass may be stripped, or they may be allowed to spawn naturally. The eggs are placed in hatching containers; the fry may either be kept initially in tanks and troughs, or they may be placed in very fine net cages in ponds. After further development, the striped bass are released into fertilized ponds to grow to fingerlings. The fingerlings may be used for restocking, or they may be grown out in tanks, ponds, or cages.