WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2016 43 Even among noted admirers and researchers the appearance of the humble oyster has not always attracted praise: “An oyster,…the exterior is not persuasive” and “such uninviting, and even repulsive things” (Beecher 1862); “scaly, drably colored, encrusted, roughly shaped... among the least aesthetically appealing in the Class Bivalvia” (Carriker 1996). Despite its homely countenance, the exterior appearance of the sometimes maligned oyster is increasingly the subject of attention. It has long been a truism that we eat first with our eyes and that the overall appearance of an oyster, including its shape, can be important to commercial success (Brake et al. 2003). Consumers are attracted by “good looking” oysters (Ruello 2002) and with cultivation has come the opportunity to manipulate the appearance of oysters (Carriker 1996). The size, shape and external appearance of an oyster can be altered through cultchless production or modified handling practices. Further, the advent of oyster breeding programs has demonstrated that shape is in part genetically determined (Ward et al. 2005), which has led to shape characteristics being included among traits for selective breeding (Kube et al. 2011). While consumers are likely to be the ultimate arbiters of oyster “beauty” they will be influenced by what farmers choose to produce and what oyster processors and restaurateurs elect to sell. Although farmers clearly have the final consumer in mind, consumer preference is not the sole driver and other factors are considered. Characteristics of shape can influence stock handling and management. For example, thin oysters can “peg” or catch in the mesh of trays and those with hooked umbos can be difficult to mechanically grade and open. Convexity of valves is an issue. The shape of the left valve can affect packing and presentation for market and some prefer flatter oysters in this regard. Increased convexity in the right valve often produces an oyster with a plump appearance when presented in the half shell. Aesthetics are likely to be species specific, but for the cupped oysters, such as Crassostrea spp., it has been suggested that farmed oysters should have a “tear drop” shape (Heath and Wilson 1999). Simple indices have been developed to describe shape. Galtsoff (1964, adapted from Crozier 1914) used a ratio of the sum of the oyster’s height (APM) and width (sometimes known as depth or thickness) divided by its length (DVM). For Irish Pacific oysters, a ratio of 3 on this scale is considered average with scores above and below this level considered poor and good, respectively (BIM 1996). In two southern states of Australia (Tasmania and South Australia), the Pacific oyster breeding program has highlighted the importance of shape as a characteristic for breeding (Ward et al. 2005) and is currently targeting a ratio of 3:2:1 (height:length:width) as a desirable standard for production (Kube et al. 2011). In New South Wales (NSW), Australia, three oyster species are produced commercially; the most important is the Sydney rock oyster Saccostrea glomerata, followed by the Pacific oyster Crassostrea gigas, and the flat oyster Ostrea angasi (O’Connor and Dove 2009). A breeding program for the Sydney rock oyster has been active since 1990 (Nell 2003) and NSW farmers can access stocks from this program and those of the Australian Seafood Industries’ Pacific oyster breeding program in Tasmania. Both programs actively use shape as criteria for stock selection (Kube et al. 2014). To gain greater insight into those oyster characteristics thought desirable by oyster farmers in NSW, an annual oyster beauty The Most Beautiful Oyster Wayne O’Connor, Michael Dove and Steve McOrrie FIGURE 1. Examples of winning oyster entries: (top) Sydney rock oysters Saccostrea glomerata, (middle) Pacific oysters Crassostrea gigas, and (bottom) flat oysters Ostrea angasi. (CONTINUED ON PAGE 44)
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