Broodstock

Broodstock, or broodfish, are a group of mature individuals used in aquaculture for breeding purposes. Broodstock can be a population of animals maintained in captivity as a source of replacement for, or enhancement of, seed and fry numbers. These are generally kept in ponds or tanks in which environmental conditions such as photoperiod, temperature and pH are controlled. Such populations often undergo conditioning to ensure maximum fry output. Broodstock can also be sourced from wild populations where they are harvested and held in maturation tanks before their seed is collected for grow-out to market size or the juveniles returned to the sea to supplement natural populations. This method, however, is subject to environmental conditions and can be unreliable seasonally, or annually. Broodstock management can improve seed quality and number through enhanced gonadal development and fecundity. Broodstock, or broodfish, are a group of mature individuals used in aquaculture for breeding purposes. Broodstock can be a population of animals maintained in captivity as a source of replacement for, or enhancement of, seed and fry numbers. These are generally kept in ponds or tanks in which environmental conditions such as photoperiod, temperature and pH are controlled. Such populations often undergo conditioning to ensure maximum fry output. Broodstock can also be sourced from wild populations where they are harvested and held in maturation tanks before their seed is collected for grow-out to market size or the juveniles returned to the sea to supplement natural populations. This method, however, is subject to environmental conditions and can be unreliable seasonally, or annually. Broodstock management can improve seed quality and number through enhanced gonadal development and fecundity. Broodstock management involves manipulating environmental factors surrounding the broodstock to ensure maximum survival, enhance gonadal development and increase fecundity. Such conditioning is necessary to ensure the sustainability of aquaculture production, and to increase the number and quality of eggs produced and control the timing of maturation and spawning. Management of the technologies for gamete production in captivity is one of the essential step for aquaculture that would ensure the growth to this sector. Unfortunately, most fish when reared in captivity condition, exhibit some degree of reproduction dysfunction. Many species of captive fish are able to reach reproduction maturity in aquaculture conditions and gonadal growth occurs normally. However, some of female species often fail final oocyte maturation stage. Hormonal manipulation and acceleration of final oocyte maturation due to the economics of broodstock management is important. For instance, in Salmoniformes, the need to collect the eggs by stripping is a serious limitation, while the time of ovulation must be predicted with accuracy, as over-ripening may take place in minutes or hours after ovulation Therefore, control of broodstock reproductive is essential for the sustainability of commercial aquaculture production Choosing species to use requires consideration of the biology of the species. This includes their size at maturity, method of reproduction, feeding behaviour and ability to tolerate adverse conditions Farms also consider whether they grow their own broodstock or obtain them from natural populations. Where natural populations are excluded, the farm can be considered a self-sustaining unit independent of external genetic influence. Pond-reared broodstocks are selected, often as immature juveniles, and grown out in suitable conditions to sexual maturity. These animals require stable water characteristics and a well-balanced, species-dependent, protein rich diet. This enhances the germinal tissue for future seed stock as it is formed in juveniles. The pond or tank in which broodfish are held must be a suitable size to hold and condition the broodstock. Dependent on the species involved you need to alter the number of individuals, and often separate the sexes. Sex separation enables the broodstock males and females to be subjected to different conditions where necessary. For example, male and female sturgeons respond to different hormone levels, this also allows more control over eggs and sperm. The characteristics of the water in which the mature broodstocks are held must be manipulated. The aquaculturist must consider the appropriate oxygen concentration, temperature, and pH of the water all of which can be species specific. The feeding regime of broodstocks is species specific and requires consideration of timing and composition of the food. Protein, lipid and fatty acid composition is particularly important. The quantity of food intake can be altered to influence spawning and maturity, for example low rations have been shown to reduce the number of fish reaching maturity while increasing the fecundity of those which do. When fry are desired, spawning can be induced in broodstocks by manipulation of relevant environmental factors. In particular the photoperiod can be altered to imply that it is time to spawn. A shortended photoperiod is known to advance spawning times while a lengthened photoperiod can delay spawning. Artificial light can be used to change the apparent day length and indicate different seasonal features so as to delay spawning. Water temperature can be increased for the same purpose. Following spawning the female broodfish are often stressed and have lost weight. They require extra care and abundant feeding at this time to ensure survival to the next spawning season. Managers can select for reproductive characteristics which influence the egg producing capability of individuals and increase fecundity by providing them with optimal environment and diets. This is further possible in pond-reared populations where traits can be selected for over generations for example, for higher fecundity.