![]() And, while most tilapia species and synthetic strains (see below) have little or no inhibitions about mating outside of their parental lines, many hybrids can only be produced through induced spawning and/or artificial fertilisation. Often, progeny must be evaluated on a cross-by-cross basis to determine how the alleles involved will interact to impact production performance. Sometimes, producing these crosses is easily accomplished, but occasionally a lot of work is involved. In fairness, the distinctions between strains, races and species are often blurred to a point where crossbreeding or hybridisation are essentially indistinguishable. ![]() Nonetheless, some researchers use the term hybrid even when both parental lines are from the same species. In contrast, when distinct stocks, lines or varieties of the same species are crossed, the most appropriate term is crossbreeding, with the resulting offspring referred to as crossbreds. Some examples include crossing striped bass with white bass, channel catfish with blue catfish, or Nile tilapia with blue tilapia. Hybridisation, in the strictest sense, involves the crossing of related species. Hybridisation vs crossbreeding (a fuzzy distinction) As explained in more detail below, sometimes the effort is more trouble than it’s worth, but at times it can result in great gains in productivity. So heterosis is, unfortunately, not something that can be inherited or passed along from generation to generation. Since these interactions depend on specific combinations of alleles, they cease to exist during the formation of eggs and sperm. While utilising heterosis can be an attractive strategy for improving traits that exhibit low heritabilities, any advantage that might be derived is only temporary. Indeed, the utilisation of dominance genetic effects is fundamentally based on combinations at every level – of species, of lines within species, and occasionally even of individuals within a population. Heterosis is based on what we call dominance genetic effects, and these effects result from interactions between the pairs of alleles at all of the genes that influence a characteristic of interest. During the past year or so, a number of interesting new studies focusing on hybridisation and heterosis in aquaculture have been reported.
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