Studies on triploid oysters in Australia - XII. Gonad discolouration and meat condition of diploid and triploid Sydney rock oysters (Saccostrea commercialis) in five estuaries in New South Wales, Australia

The relative performance, in terms of meat condition, of triploid compared to diploid Sydney rock oysters varied among five widely distributed sites i n New South Wales (NSW). Over the final year on leases, ploidy, month and t he ploidy x month interaction had a significant effect on meat condition at all sites except for ploidy at the southern, Lake Pambula site. From March to December (autumn to the first month of summer), triploid condition indi ces were higher, or not significantly different from those of diploids at a ll sites. Condition indices of triploids were higher than those of diploids from May to November/December at four of the five sites. A higher conditio n index (CI) of triploids became apparent later in the sampling period for the Lake Pambula site in comparison to the remaining four sites. Triploid S ydney rock oysters were susceptible to brown discolouration of the gonad su rface. Discolouration occurred in localised areas of the gonad and was not correlated to CI except for triploids at Lake Pambula, As discolouration wa s less noticeable during cooler months of the year, thus, coinciding with t he generally superior condition of triploids relative to diploids during wi nter and spring, triploids remain a viable winter crop for farmers througho ut NSW. (C) 1999 Elsevier Science B.V. All rights reserved.