One of the important technological concepts that was developed in the Hawaiian Islands is that of the fishpond. From the 14th to the 19th centuries, these sites served as aquariums for the raising of selected fish. From its inception until the 1900's, the fishpond progressed little in design and function. Its rudimentary nature was a function of both technology and religion. Because of the open ditches, sluice grates, and permeable walls, neither the types nor the quantity of juvenile fish entering or leaving could be controlled. In addition, religious beliefs prevented experimenting with fertilization to increase yield. Although seemingly inefficient, the native aquacultural system was not intended to produce a great amount of fish but rather to yield selected fish on call. Fishponds became symbols of the chiefly right to conspicuous consumption and to ownership of the land and its resources. They were manifestations of the chief's political power and his ability to control and tap his resources. As soon as the native aristocracy changed to a Western-style kingdom, the fishpond's function changed, until, by the 1930' s, the majority were simply archeological remains-mounds and walls of rock along a river or shore.