What is good aquaculture? << back
In aquaculture, there are essentially two stages in the life of the aquatic animal being cultivated: hatchery and grow-out. The hatchery is where animals are bred in controlled (artificial) conditions, hatched and raised.1 What does that mean in practice?
The process of breeding in present day aquaculture begins by identifying desirable animal characteristics/traits in offspring and using those to facilitate the selection of similar characteristics/traits in the mature (parent) animals. The mature (parent) animals are called ‘broodstock’. Choosing the same desirable characteristics or traits over a prolonged period of time in broodstock is called ‘selective breeding’. Selective breeding has been widely used in agriculture (and terrestrial animal husbandry) for centuries to produce many of today’s fruits and vegetables (and domesticated livestock). For example, the wild mustard plant has been selectively bred to produce what we enjoy today as, kohlrabi, kale, broccoli, Brussel sprouts, cabbage and cauliflower!2 Selective breeding of aquatic animals is done in a similar fashion, only doing so in water. In aquaculture, primary considerations taken into account when choosing aquatic broodstock, can include growth-rates, disease resistance, and physical characteristics such as size or meat yield. Once the broodstock with desired characteristics have been chosen they are bred in controlled conditions. Let’s look at 3 examples: Atlantic salmon; shrimp and tilapia.
Atlantic salmon: Eggs from female broodstock are fertilized at the hatchery with milt (which contains sperm) from male broodstock. Eggs and milt are collected through a process called ‘stripping’. ‘Certified aquaculture’ provides strict guidelines to ensure the health and welfare of Atlantic salmon broodstock as they are handled throughout the stripping process. When the fertilized egg hatches (after about 3 months) it is called an alevin, which is nourished by its own egg yolk sac. Alevin grow into salmon fry, which are then able to consume feed. As fry grow they become parr and finally, parr become smolt, which can be transferred to saltwater grow-out facilities. From fertilization to transfer-to-sea spans anywhere from 12-18 months and the entire cycle from hatchery through to harvest takes about 3 years.
Shrimp: There are 3 types of broodstock available for hatcheries: wild-capture, from current shrimp grow-out facilities, or dedicated broodstock rearing facilities. While ‘certified aquaculture’ allows wild-capture broodstock, it must adhere to rigorous standards to ensure they are from sustainable fisheries and are free of transmissible diseases.3 To induce the maturation/spawning of female broodstock, a process known as ‘ablation’ is commonly employed, ‘Certified aquaculture’ provides animal health and welfare guidelines for this practice. Once hatched, shrimp spend about 26-31 days developing at the hatchery before be transferred to grow-out facilities-4 During this time they pass through many developmental stages beginning as fertilized eggs and finishing as post larvae (PL). PLs can take anywhere from an additional 3.5 to 6 months to reach a harvestable size.
Tilapia: Tilapia are asynchronous breeders, which means the ratio of female-to-male broodstock can be as high as 4 females to 1 male. Another unique characteristic of tilapia is fertilized eggs are incubated inside the mouth of the mother fish, thus tilapia are called ‘maternal mouth brooders’. While tilapia can be bred artificially (through stripping), most commonly, male and female broodstock breed in ponds or dedicated breeding tanks. After breeding, the female takes the fertilized eggs in her mouth. These eggs can either be collected by the hatchery and placed in specially designed incubators or allowed to hatch naturally and collected when they reach fry stage. In either case, as fry are collected, they are feed special feed (3-4 weeks) to encourage sex-reversal to assure as high a percentage of male fish as possible. Afterwards, tilapia can spend 2-3 months at a nursery, where they develop into fingerlings, before being transferred to a grow-out facility (5-6 months).5
For responsible aquaculture, the importance of hatcheries providing well-nourished and properly developed, disease-free smolt (Atlantic salmon), PLs (shrimp) or fingerlings (tilapia) is critical. ‘Certified aquaculture’ assists by providing guidance on inputs such as feed, good animal health and welfare practices, and veterinary health plans as well as environmental and social concerns.