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1 A ABALONES DAVID R. SCHIEL University of Canterbury, Christchurch, New Zealand Abalones are marine snails that play only a minor role in the functioning of marine communities yet are culturally and commercially important and are iconic species of kelpdominated habitats. They were once tremendously abundant along the shores of much of the temperate zone, with large aggregations piled two or more layers deep along large stretches of rocky sea floor (Fig. ). Abalones were prized for their meat and shells by indigenous communities worldwide , particularly along the coasts of California, Japan, and New Zealand. Their shells are well represented in middens, such as on the Channel Islands off southern California, that date as far back as , years ago. The tough shells, lined with iridescent mother of pearl, were used as ornaments and to fashion practical implements such as bowls, buttons, and fish hooks. In New Zealand Maori culture, abalone shell is extensively incorporated into carvings and ornaments. These historical uses have translated into high demand in modern times to such an extent that most abalone populations are greatly depleted from their historical abundances, with some species even considered to be in danger of extinction. There are now management practices in place worldwide to sustain and extend populations, based on knowledge about their biology and ecology. DISTRIBUTION AND BIOLOGY Abalone is the generic name that refers to the group of single-shelled molluscs of the class Gastropoda, family Haliotidae, and the single genus Haliotis. There are many regional names for Haliotis species, including paua from New Zealand, perlemoen in South Africa, and ormers in Europe. There is no consensus on the number of species of abalone, but estimates range from to around . There are many subspecies, and some co-occurring species form hybrids with gradations of characteristics. The taxonomy of many of these variants is unresolved. Abalones occur from the warm waters of tropical coral reefs through to the cool temperate zone. Their major abundances are along coastlines where kelp beds occur, particularly New Zealand, Australia, South Africa, Korea, Japan, China, the west coast of North America, and the Atlantic coast from Senegal to Spain, France, and the British Isles. An anomalous occurrence is the commercially fished species H. mariae, which is restricted to two areas of the tropical waters of Oman where cool, nutrient-rich, upwelled water sustains a kelp forest. Haliotis is an ancient FIGURE 1 Once-abundant coastal populations of most abalone species are now severely depleted, and dense aggregations are usually confined to small patches in remote places. Shown here, New Zealand abalone (Haliotis iris, locally called “paua”) of about 16 cm in shell length at a remote offshore island in a 5-m depth of water. Photograph by Reyn Naylor, National Institute of Water & Atmospheric Research Ltd, New Zealand. genus, to million years old. One current view, based on DNA analyses of species worldwide, is that it originated in the ancient land mass of the Southern Hemisphere and speciated as the continents drifted into their present positions. There is disparity in sizes of tropical and cold-water species. Tropical species rarely exceed mm in length; large-bodied species occur only in cold-water areas dominated by kelp and other macroalgae, which provide energy-rich food. Many of the commercially important species reach large sizes. For example, H. iris from New Zealand, H. ruber from Australia, H. discus hannai from Japan, and H. midae from South Africa can reach lengths of around mm, and the giant of them all, H. rufescens of California, can grow to more than mm. Different species of abalone occur from the intertidal zone to depths of hundreds of meters. However, their major distribution is in near-shore waters generally less than m in depth. Their sleek hydrodynamic shells make abalones well suited for survival in turbulent waters. Abalones have a relatively simple biology. A muscular foot, which comprises most of the weight of the animal, holds them tenaciously to rock surfaces by means of a contact mucilage and powerful contractions. The foot can raise the shell several centimeters above the substratum , which allows the abalone to trap drift algae as it tumbles along the sea floor. As in other gastropods, food is rasped by a radula, a double-rowed band of spiked chitinous material inside the mouth. Respiration occurs through the gills, which sit just below a series of holes that radiate in an arc along the top of the shell. These holes are also avenues for expelling waste products and...
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