Aquaculture approaches

Recirculating systems can make aquaculture feasible in locations where conditions would otherwise not be conducive to successful operations. Such systems can also be used to reduce transportation costs by making it possible to grow animals near markets. In areas where there are concerns about pollution or the use of exotic species, closed systems provide an alternative approach to more extensive types of operations. 

THE SCIENCE OF ECOLOGY emerged at the turn of the last century and brought with it the experimental approaches that were already central to the study of physiology (1-3). Manipulations of whole aquatic ecosystems— excluding aquaculture, which dates back 2500 years (4)—developed more slowly, mainly because of difficulties associated with increased biotic complexity and physical scale in larger systems. One technique initially used to overcome the problems of complexity, scale, and replicability was creation of controlled microcosms that embodied a more or less natural representation of the whole system (5, 6). 

Although previous research concerning the use of natural compounds as selective cyanobactericides is not very extensive, past and present research indicate that such an approach has merit and should continue to be investigated. The vast majority of natural compounds in nature remain unscreened as to their potential for use as environmentally-safe, selective compounds to help control noxious species of cyanobacteria in freshwater ecosystems. The discovery of such compounds that are cost-effective would be very beneficial to industries such as catfish aquaculture and municipal drinking water systems by reducing their dependence on synthetic compounds (herbicides) to control cyanobacterial blooms. The use of synthetic herbicides carries with it environmental safety concerns and a negative perception by the public. 

As the demand for aquatic products continues to increase and the supply of wild stocks is diminishing, it is important that aquaculture embraces the ecosystem approach to management just as the fisheries sector has done. In Parts 2 and 3 of the book we describe the culture of species that either currently rely upon wild juveniles for their production or have done so until recently. 

WEBB K L and CHU F E (1983) Phytoplankton as a food source for bivalve larvae, in Pruder G D, Langdon C J and Conklin D E (eds), Ib-oceedings of the second international conference on aquaculture nutrition Biochemical and physiological approaches to shellfish nutrition. Baton Ronge, LA Lonisiana State University, 272-291. 

BREUiL G, THiERY R, PEPIN J F and BLANCHETON J p (2003) The Control of nodavirus disease in sea bass Dicentrarchus labrax, from breeder to commercial size Toward a new approach of organic aquaculture, in Lee C-S and O Bryen P J (eds). Biosecurity in Aquaculture Production Systems Exclusion of Pathogens and Other Undesirables. Baton Rouge, LA The World Aquaculture Society, 65-79. 

Several recent studies have demonstrated the importance of understanding the general microbial communities of which aquaculture pathogens are members. For these studies, the culture-based approaches have severe limitations since only 0.01-10 % of bacteria in marine systems can be cultured by conventional techniques (Connon and Giovannini, 2002 Osborne and Smith, 2005). In addition, the appropriateness of the culture media used and culture conditions will affect the fraction of this culturable community that is successfully recovered. For instance, many studies of fish gastrointestinal microbiota have not included anaerobic culture conditions and have therefore missed certain fastidious and obligate anaerobes completely (Nayak,... 

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