People involved in the aquaculture industry are already familiar with the three primary stages that define fish farming: fingerling, rearing, and fattening. Each of these stages carries unique characteristics and demands specific handling and attention tailored to the needs of the fish at that particular phase. Additionally, nutritional requirements vary significantly depending on the stage of cultivation.
For more effective management of each phase of the fish lifecycle, it's advisable to conduct these steps in separate facilities or in well-defined, controlled environments that provide the ideal conditions for the fish's development. In this blog post, we’ll explore the distinct features of fingerling, rearing, and fattening, along with the appropriate feeding strategies for each phase. We'll also delve into the breeding timelines of some popular species and the factors influencing the duration of these periods.
Fingerling: A Critical Phase Requiring Extraordinary Care
The fingerling stage marks the initial phase of fish development, occurring when they are still quite young. This stage typically takes place in specialized farms to maximize efficiency. At the end of this phase, when they reach the desired size and weight, they are sold to other farms or facilities for the subsequent stages—rearing and fattening.
Prior to reaching the fingerling stage, during the larval phase, newly hatched fish, measuring just millimeters in size, do not require external food since they rely on the energy and nutrients stored in their bodies. Due to their tiny size and fragility, they remain in incubators until they gain the ability to swim independently.
The larval phase varies across species, lasting roughly a week for most tropical fish. Following this period, the fish transition into the post-larval phase, where they are counted and distributed to external hatcheries or intensive fingerling tanks.
The fingerling phase is particularly crucial when it comes to feeding. Given their small size, there are limited food options available to them. On the flip side, their diminutive size also makes them vulnerable to predation by aquatic insects and other small creatures. Unwanted fish species, such as water snakes and birds, can also pose threats. Additionally, fingerlings often compete for food with tadpoles and other small fish.
Thus, fingerlings must primarily consume plankton, which includes microorganisms found in the water column, and benthos, which consists of microorganisms living on the substrate. Certain species like tilapia, however, begin consuming inert food (ration) right after hatching. This type of feeding continues until the fish are capable of feeding on other sources. This method is commonly used for native species such as tambaqui, painted, and golden fish.
Options for Fingerling Production
Different systems can be employed for fingerling production, including semi-intensive, intensive, and extensive setups.
1) Semi-Intensive Fingerling Production
In semi-intensive fingerling production, the most widely practiced system, hatcheries need hydraulic equipment for comprehensive flow control, allowing for more efficient and proper handling. This system requires key components such as total drying, mud removal, predator eradication, liming, and fertilization to boost phytoplankton and zooplankton production.
Water quality must be regularly monitored and adjusted through physical and chemical analysis.
2) Intensive Fingerling Production
Intensive fingerling production represents a relatively modern approach that is still developing in many fish farms. Its primary aim is to establish a closed system that prevents predators from infiltrating. This system is typically lab-driven and, due to its high level of control, is more expensive because it requires constant human intervention.
Nonetheless, the advantage lies in achieving a high survival rate and, consequently, substantial fingerling production.
3) Extensive Fingerling Production
Another system under development is the extensive model. In this setup, family or community hatcheries receive post-larvae animals (a phase prior to fingerlings). The goal here is to manage predator populations both before and during the process.
However, extensive fingerling production can only be practiced with specific post-larvae species and at lower densities, as environmental quality and food organism availability may be limited. Additionally, eradicating predators can be challenging due to the lack of flow control in certain units.
Rearing: Transitioning Fingerlings to Juvenile Fish
Once they reach the ideal size for sale to other fish farms, fingerlings move into the rearing phase, the second stage of fish farming. By the end of this phase, they will have developed into juvenile fish.
This process can happen independently, meaning fish farms specialize in rearing fingerlings until they reach the juvenile stage and then sell them to other farms that will proceed to fatten them. Alternatively, the rearing and fattening phases can occur simultaneously.
When rearing happens independently, fingerlings are bought directly from specialized hatcheries. They are then transferred to the rearing facility, where they remain until they reach the juvenile stage. Finally, they are sent to specialized farms for the final fattening phase.
Fattening: The Final Stage Before Commercialization
At this stage, the fish reach adulthood and are prepared for the consumer market. In some farms, the ideal size to begin the fattening phase is 5 cm, though this can vary based on species traits and seasonal conditions. This size is thought to enhance their ability to consume larger particles, such as farinaceous foods, small insects, and others, while also improving their capacity to evade predators.
The fattening phase focuses on increasing the fish's size until they reach commercial weight, which can exceed 5 kg depending on the species. This phase necessitates larger quantities of food, requiring careful daily feeding adjustments and regular monitoring of production metrics.
Nutritional Needs of Fish
Certain nutrients must be present in fish feed to ensure healthy development and growth throughout all stages of farming, especially during the fattening phase, when the diet is most enhanced. Protein content varies by species and life cycle stage, but regardless of the protein source chosen, the 10 essential amino acids must always be included:
- Methionine
- Arginine
- Threonine
- Tryptophan
- Hisitidine
- Isoleucine
- Lysine
- Leucine
- Valine
- Phenylalanine
Choosing the right protein source for fish feed presents several challenges. For instance, when using plant-based protein sources like soybean meal, the diet often needs supplementation with methionine, as these sources are typically low in this amino acid. Animal-based sources are generally preferred due to their complete amino acid profile. Sources like hydrolyzed chicken protein, which undergoes enzymatic hydrolysis, are easily absorbed and provide bioactive peptides that offer additional non-nutritional benefits, such as enhancing palatability, providing antioxidant effects, and acting as immunostimulants.
Due to their role in growth, higher protein content is generally required in the early stages of a fish's life.
Lipids, in addition to serving as energy sources and carriers of fat-soluble vitamins, also contain essential fatty acids crucial for fish development, such as eicosapentaenoic acid (EPA) and decosahexaenoic acid (DHA). These fats are usually present in proportions ranging from 5 to 30%.
Carbohydrates serve as an energy source. However, unlike mammals, they are not efficiently utilized by most fish species, especially carnivores. Excess carbohydrates are stored as glycogen or fat. In carnivorous diets, they should ideally be present at a maximum of 20% for optimal animal utilization. Omnivorous species can tolerate higher carbohydrate levels.
Water-soluble and fat-soluble vitamins help boost the fish's immune system, and some act as antioxidants. Minerals regulate osmotic balance and contribute to bone formation and integrity.
Production Time: The Unique Aspects of Each Species
While the stages of fish farming are universal, each species exhibits distinct characteristics throughout the process that farmers need to be aware of. Tilapia, for instance, is a freshwater fish renowned for its rapid breeding time, which typically spans 4 to 11 months, influenced by factors such as location, climate, water temperature, and market demand.
Common carp, on the other hand, requires more delicate handling and has a longer average breeding time of about a year. Catfish also has a breeding time of approximately a year, with its reproductive peak occurring within three years. Known for its predatory nature due to its carnivorous diet, catfish also exhibit a voracious appetite, making it challenging for this species to reject any food offered.
Conclusion
The stages of fish farming are clearly defined, each with its own set of characteristics that must be respected to ensure healthy development and optimal growth. To achieve this, farmers must consider production timelines and pay special attention to the fish's diet to ensure all necessary nutrients are included.
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