Recent data on fishmeal and fish-oil supply are presented identifying key producer countries and raw material sources and distinguishing between whole fish and by-products. The conversion of these raw materials into marine ingredients is discussed and global volumes presented. This is followed by a summary of the main countries using these marine ingredients over recent years. Uses of fishmeal and fish-oil by market segment are then presented. From this, a global mass balance of inputs and outputs is derived which allows the calculation of the input-to-output ratios (fish in:fish out; FIFO) for the main aquaculture production types to be made. Current areas of focus by the industry include the need to demonstrate sustainable practice, more strategic use of marine ingredients, greater use of fishery and land-animal by-products as well as vegetable substitutes, and novel sources of essential omega-3 fats, notably the long-chain polyunsaturated fatty acids, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. Implications are drawn for future supply prospects of fishmeal and fish-oil and their future role in aquaculture, agriculture and human health.

11The current range of Scottish salmon feeds is adapted to a differentiated supply of salmon products, 12 including differing omega-3 content, differing content of marine raw materials, etc. The progressive 13 replacement of marine feed ingredients by plant proteins and oils is reducing the content of omega-3 14

SummaryWashed conidia of Perono8pora tabacina Adam germinated poorly or not at all in water alone, but germinated in the presence of riboflavin. The rate of germination of conidia in liquid suspension was enhanced by the presence of carbon and nitrogen sources, phosphate, and calcium and magnesium ions. The effects of 141 metabolites on germination and germ-tube elongation have been tested.A number of analogues of natural metabolites were inhibitory to germination and germ-tube elongation. Extracts and exudates of tobacco leaves did not affect either the amount or rate of germination.Washing by centrifugation increased the percentage of conidia that germinated subsequently and the presence of a germination inhibitor in unwashed conidia is postulated.The optimum temperature for germination of conidia on agar, or in liquid suspension, was in the range 15-20°C. The pH optimum varied with the constitution of the medium; when germinated on 2 % agar a broad optimum was shown at pH's 5·5-8·0, whereas in liquid suspension the optimum was in the pH range 6· 5-8· O.When conidia were tested within 24 hI' from the time of initiation of sporulation, germination was high (85%). After 48 and 72 hI' germination had dropped to 61 and 48% respectively.Washed spores showed no loss of germination capacity when kept for up to 6· 5 hI', but germination was negligible after 18 hr storage.Visible light did not affect germination, but 9000 fLWfcm2 of ultraviolet light reduced it to 2·7%.

The soil-borne fungus Phytophthora cinnamomi Rands is a particularly impor-tant pathogen in Australia because of its consistent association with root-rot disease of a wide variety of exotic and native plant species. It was thought originally to have been introduced from south-east Asia (Crandall and Gravatt 1967), but evidence recently obtained (Pratt, Heather, and Shepherd, unpublished data), suggests that it may be indigenous to eastern Australia and may have been partly instrumental in determining the distribution of certain susceptible species, particularly Eucalyptu8 spp.

Determinations of cardinal temperatures for growth on various media of 50 Australian isolates of Phytophthova cinnamomi showed that growth did not occur outside the range 5-35°C. The range of temperatures at which growth optima occurred varied according to the isolate and medium used and encompassed the whole range of values reported by overseas authors. Growth rates of 361 isolates on corn meal agar at 25°C varied within the range 4.7-10.5 mm/day. There was no correlation between optimum temperature and whether isolates were slow- or fastgrowing or their place of origin. Fast-growing isolates (6-11 mm/day) were obtained from all States, but slower-growing isolates (<6 mm/day) were obtained only from southern and western regions of Australia. Populations from different regions of Australia exhibited different growth rate parameters. The variability of mycelial isolates in culture was studied by examining differences in growth rate among replicated parent, single-zoospore, single-zoosporangium and single terminal-hyphal isolates. Extensive variation was found among first generation single-zoospore progenies of field isolates, with lesser variation among progeny of single zoosporangia, terminal hyphal cultures and second and third generation zoospore derivatives. The origin of this variation is discussed and it is suggested that field isolates are heterokaryotic, since zoospores proved to be predominantly uninucleate. When various Phytophthora species were incubated at temperatures above those at which growth was possible and then returned to 25°C, their subsequent ability to resume growth depended on the particular time-temperature combination used. Considerable variation of response was found among a number of isolates of P. cinnamomi and, following the establishment of single zoospore isolates, the potential variability of field isolates was shown to persist through successive generations of zoospore propagation. It is suggested that a cytoplasmic mechanism of inheritance may be responsible for this variation.