Fe ature a rtic le
Controlled reproduction and domestication in aquaculture The current state of the art
Part I
by Mart in Bilio Consultant for Ecology and Living Aquatic Resources Management e-mail: martin.bilio@t-online.de
Introduction
Antecedents
Objectives and scope
My awareness of the importance of the prerequisites of domestication in aquaculture goes back to 1984 when, visiting Taiwan, I made a key experience of my aquaculture career: I got an immediate insight into the need for continuously controlled reproduction of a cultured organism in order to secure the long-term success of its farming.
There is considerable uncertainty about the meaning of the term “domestication” in aquaculture. While the process of domestication of the majority of terrestrial animals and plants has benefited from thousands of years of trial and error first and deliberate selection of promising traits later, only a very low number of aquatic organisms has benefited from such a vast experience. When in the second half of the last century hunger rose to worldwide concern, the unexploited potential of aquatic protein production finally began to attract public attention. Increasing efforts were made to tap this source and “aquaculture” was introduced as a twin term to agriculture. Terrestrial animal husbandry and crop cultivation can be sustained as long as adequate living conditions can be created and controlled. Continuous control of reproduction is no concern. With many of the aquatic organisms currently subjected to culture conditions, control of reproduction is still problematic and their production dependent on supplies of seed or broodstock from the wild. Such dependence sets limits to the sustainability of culture production. Long-term sustainability can only be guaranteed when continuous controlled reproduction is achieved and, with this, the major prerequisite of domestication fulfilled (see below). Continuous controlled reproduction – and, based upon this, domestication - thus assumes the character of an overriding indicator of the sustainability of aquaculture development. Knowing the progress of domestication can thus give valuable insight into the status and prospects of aquaculture. It is for this reason that the present attempt is being made to put the pertinent information together and interpret and evaluate the outcome. Table 1 is the central part of this paper and conceived in a way that it can easily be updated and evaluated anew.
Taxonomic and geographic range While finfishes, crustaceans and bivalves are considered in the present paper, gastropods (with the exception of abalones), amphibians, reptiles, exclusively ornamental fishes, and aquatic plants are not. Worldwide coverage was intended since the culture of a number of species is attempted in different parts of the world. It is probable, however, that some relevant species are absent from Table 1 due to lack of available information.
Aquaculture in Taiwan was at that time known for successfully growing eel and penaeid shrimp. The major problem with the shrimp was very low survival of the offspring (juveniles, F1 generation) produced in the National Aquaculture Research Institute, showing that too little was known about the conditions necessary for gonad maturation. It was, therefore, contemplated to release a great number of juveniles obtained through controlled reproduction of wild breeders (the P generation) into an area where fishing would be banned for a while in order to give the released shrimp (F1) time to mature. After the ban, a high price would be paid for each egg-bearing female encountered in the catches, in order to obtain material for further research on controlled reproduction. Although I do not know whether this idea was realised, the discussion let me understand how important it is to know how to raise offspring not only from wild, but also from cultured parents. Obviously, only this could make sure that the production was at least biologically sustainable. From then on I have used every opportunity, during my extensive travelling for development cooperation purposes, to question the biological sustainability of the production of new species through aquaculture. This endeavour has finally led to the present paper.
Gathering of information Most of the information contained in this paper was obtained by e-mail correspondence and through personal discussion. It was hoped that this approach could provide the most recent information available, including the possibility to check in immediate discussions common understanding of terms and the reliability and adequate interpretation of facts. Unfortunately, my e-mail requests for species-related pertinent information did not always get the response that I had hoped for. This may have been due to otherwise already heavy work load. It is also possible that precise knowledge about domestication is not
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