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This chapter presents an ex post impact assessment of the development and dissemination of small-scale integrated aquaculture-agriculture (IAA) technologies in Malawi over more than 15 years by the WorldFish Centre and its national and international partners. The results indicate that the adoption of IAA technology in Malawi has improved total farm productivity by 10%, increased per hectare farm income by 134% and total farm income by 61%, and improved the technical efficiency of farming by almost 40%. In addition, the increased per capita consumption of fresh fish by about 208% and per capita consumption of dried fish by about 21% have resulted in an enhanced consumption of protein-rich foods. IAA has improved the sustainability and environment of the adopters' farms, reduced nitrogen loss by half and improved nitrogen use efficiency. The development and dissemination of IAA technologies in Malawi have also institutionalized the natural resource management approach within the Malawi Department of Fisheries, strengthened local institutions and improved the overall welfare of both producers and consumers. The internal rate of return from research and dissemination of IAA technologies in Malawi is at least 12.2%. This estimated rate of return is a very conservative estimate and does not include many of the positive non-market benefits of IAA technology such as impact on ecosystem health and local institutions.

Aquaculture production techniques based on the culture of low-value herbivorous and/or omnivorous freshwater finfish in inland rural communities, within semi-intensive or extensive farming systems that use moderate to low levels of production inputs, have supplied large quantities of affordable fish for domestic markets and home consumption. Only recently have studies been initiated to assess the contribution of these integrated agriculture-aquaculture (IAA) systems to improved nutrition and food security, both within IAA farm households and in non-IAA households in the community. The effect can be direct, through within-household consumption and dietary improvement, but also indirect, through sale of fish produce and purchase of other food items (often at lower unit value than the sold fish). In the absence of in-depth studies, this contribution presents key elements from recent experiences in Africa and Asia that indicate where benefits from the integration of aquaculture into farming systems for human nutrition and food security can be achieved, and it recommends future avenues for research to provide much-needed information on the contribution of aquaculture to household nutrition and food security.

Mass aggregations of the marine free-living nematode Pontonema vulgare containing thousands to milhons of individuals were observed in the summer half-year (May to Oct) above the surface of sublittoral (mainly 6 to 9 m depth) soft bottoms of the inner Flensburg and Kiel fjords. Sedlments were rich in organic matter, reduced, and black nearly to the surface. Oxygen content of the overlying water was very low (1 to 2 m1 O2 I-'). The aggregations occurred on dead and moribund macrofaunal animals, on beds of rothng Ulva sp. and Zostera manna, and near organic wastes from a trout farm. They marked sharply the transition zone between oxlc sites ( 2 4 m1 0, I-' in summer) inhabited by an intact macrofauna, and anoxlc sites (0 to 0.5 m1 O2 1 -I ln summer) lacking any macrofauna (including P. vulgare). It is concluded that these aggregations above (not withm) the surface of the sediment indicate dramatic mortality of the macrofauna livlng there due to decreasing oxygen content and increasing H,S content. These processes are known to occur especially in organically polluted areas. Previous taxonomic descriptions of P. vulgare are supplemented, and P. balticum (Schultz 1932) is suggested to be synonymous with P. vulgare.

Based on on-farm surveys implemented in the Ganges Delta in Bangladesh and the Mekong Delta in Vietnam, the dynamics of shrimp aquaculture in salinity-influenced coastal areas were analysed. Qualitative data were collected through interviewing both individual and group farmers in 2005 and 2006, as well as key informants and value chain stakeholders, to obtain an overview of the dynamics of salinity-influenced aquaculture in these two deltas. The first phase of the coastal area's agroeconomic evolution is related to the policy and infrastructure in the course of agroeconomic transformation. A second phase is characterized by the spread of shrimp aquaculture (in successive levels of technology), causing these coastal zones to become areas of strategic export product generation. Different factors such as government policy, demography and international market demand drove this evolution in both deltas. In a third phase, the risk associated with shrimp farming because of shrimp virus outbreaks led farmers to diversify or intensify the aquaculture farming system. The evolution of shrimp farming systems in both deltas has been toward greater diversification of aquaculture technologies and is dependent on both natural environmental factors such as saltwater period duration and soil quality, technical factors such as access to drainage and socio-economic factors such as investment capacity and market demand. Comparing the coastal area of Bangladesh and the Mekong Delta in Vietnam, the key factors identified were land ownership, access to knowledge for the improvement of shrimp culture technology and diversification of aquaculture production. The alternating rice-shrimp system (i.e. rice in the rainy season, followed by shrimp in the dry season) and diversified brackishwater polyculture show more stable economic returns in comparison to extensive and intensive shrimp monoculture in both areas. In Bangladesh, water management infrastructure, access to information and the development of information networks were highlighted as key factors necessary for the improvement of brackishwater aquaculture. In Vietnam, the higher level of technology used in coastal aquaculture underlined the need for the development of better management practices to reduce the environmental burden and to evolve towards sustainable production systems.

Three approaches for multivariate analysis of ¢sh growth in aquaculture experiments with Nile tilapia (Oreochromis niloticus niloticus L.) based on the von Bertalan¡y growth curve are presented and compared. The approaches are: an extended Gullandand-Holt (GH) plot, a forced extended GH plot and a multilinear regression analysis for the growth parameter K. All three models provide valuable insight into the major environmental factors in£uencing the daily growth rate and explain 28^46% of the variance of the observed daily growth rate of the used data set. For all three methods, the modelled parameter is sig-ni¢cantly related to the net yield of Nile tilapia and can, therefore, be used for the predictive modelling of management scenarios. The extended GH plot loads the in£uence of environmental parameters upon L 1 , while the forced extended GH plot and Direct ¢tting of K load the in£uence on the growth parameter K. The latter is more in the tradition of aquaculture research. But the forced extended GH plot and Direct ¢tting of K can only be applied if L 1 of the cultured species is known, as the selected L 1 in£uences the variance in the regression variables.

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