The ecosystem approach to aquaculture provides the conceptual guideline for spatial planning and management. This publication describes the major steps related to these activities. The rationale for and objectives of each step, the ways (methodologies) to implement it, and the means (tools) that are available to enable a methodology are described in a stepwise fashion. Recommendations to practitioners and policy-makers are provided. A separate policy brief accompanies this paper. The benefits from spatial planning and management are numerous and include higher productivity and returns for investors, and more effective mitigation of environmental, economic and social risks, the details of which are provided in this paper.

Three populations each of Oreochromis aureus and O. niloticus, one each of O. mossambicus and O. urolepis hornorum, and two each of red tilapia derived from hybridization of O. urolepis hornorum females and O. mossambicus males were compared for the electrophoretic mobilities of their enzymes at 27 enzyme loci using horizontal starch gel electrophoresis. Variation was sufficient to differentiate the species but not all of the populations surveyed. Dichotomous keys based on relative electrophoretic mobilities of isozymes were developed for the identification of the species. The primary diagnostic loci were AAT [Aspartate Amino Transferase], EST [Esterase] and SOD [Superoxide Dismutase] in the liver and EST and GPI [Glucose Phosphate Isomerase] in the eye. Red tilapia had a high frequency of alleles from O. mossambicus, followed by O. urolepis hornorum, with low frequencies of O. aureus and O. niloticus.

Samples of the Auburn University populations of bighead carp (Aristichthys nobilis), silver carp (Hypothalmichthys molitrix) and their reciprocal hybrids were surveyed for isozyme varibility at 23 loci. Allelic variation in loci encoding for alcohol dehydrogenase, creatine kinase, lactate dehydrogenase, malate dehydrogenase (NAD-dependent) and superoxide dismutase was found to differentiate the two species. Reciprocal hybrids could not be distinguished electrophoretically. Isozyme banding patterns indicate these hybrids were diploid. These hybrids were fertile, and they produced large numbers of F2 progeny. The bighead carp population had 4% of its loci polymorphic, whereas the silver carp were polymorphic at 17% of their loci. The bighead carp evaluated in this study as well as those in previously reported studies of cultured carp, have a degree of homozygosity that is probably related to the hatchery procedures for propagating these species.

Although Jordan is basically a dry land that appears uninviting to prospective fish farmers, it has limited, but high quality water from run-off in the highlands, wells in the desert, and springs - both cool and geothermal. These sources create locations for profitable fish culture operations. The availability of sites plus Jordan's importation of 7,000 tons of fish products in 1987, makes commercial aquaculture more promising than one would at first suppose.