Vannamei shrimp (Litopenaeus vannamei) has emerged as a leading fishery commodity in the aquaculture sector, particularly in Indonesia. The high market demand for this shrimp, both domestically and internationally, drives the need for increased and sustainable farming practices. In this context, the success of vannamei shrimp farming heavily relies on a deep understanding of the various stages of cultivation, especially the broodstock spawning process, which marks the beginning of the quality shrimp production cycle. Proper spawning not only ensures the production of healthy larvae (shrimp seeds) but also minimizes the risk of production failure.
One of the keys to successful vannamei shrimp spawning lies in careful and meticulous management of its various supporting aspects. Preparation, including water quality, spawning container conditions, and broodstock management, are critical factors that must be considered. Each spawning stage requires specific procedures to ensure optimal results, such as ensuring the water used is free of pathogens and ensuring that the female broodstock has reached perfect gonad maturity.
Furthermore, successful spawning doesn't solely focus on biological factors; it also requires the implementation of appropriate technology. The use of water filtration systems, container sterilization, and optimal feed management are examples of technology-based approaches to support vannamei shrimp hatchery activities. This article will discuss the vannamei shrimp broodstock spawning process, from reproductive anatomy to essential steps in ensuring hatchery success.
The selection process for vannamei shrimp broodstock to produce superior, high-quality, and traceable broodstock: BPIU2K Karangasem
The female vannamei shrimp's reproductive organs
The female vannamei shrimp's reproductive organs have a fairly complex structure and consist of several essential components, namely a pair of ovaries, oviducts, genital openings, and thelycum. The ovaries function as the site of egg or oocyte production and development. The oviducts act as channels connecting the ovaries to the genital openings, where eggs are released during the spawning process. Meanwhile, the thelycum is an external organ that plays a role in the fertilization process. All of these components work harmoniously to support the female shrimp's reproductive cycle, from egg formation to the release of eggs ready for fertilization.
The process of egg formation in vannamei shrimp begins with the production of oogonia, which are egg stem cells, occurring through mitosis in the germinal epithelium of the ovary. The formed oogonia then undergo meiosis to differentiate into oocytes, which are the early stage of mature eggs. These oocytes are then surrounded by follicle cells that function as protectors and also as a medium to absorb essential nutrients from the mother's body, especially yolk material derived from the mother's blood. This process is a crucial part of oocyte development towards maturity.
The yolk absorbed by the oocytes is vital in supporting embryo development after fertilization occurs. This material contains nutrients that will be utilized by the embryo during the early stages of development, before the embryo can independently seek food sources from the environment. Therefore, the quality and quantity of yolk absorbed by the oocytes significantly influence the success of embryo development until hatching.
Spawning preparation
Water preparation
Good water quality is crucial for the success of vannamei shrimp hatcheries. Diseases caused by bacteria, fungi, and parasites often originate from the water used. Therefore, water filtration systems, ozonization, and ultraviolet irradiation are essential components to prevent disease spread in hatcheries. Proper water management can also reduce the need for medications and antibiotics.
The first step in water preparation involves obtaining clean seawater, which is pumped into a sedimentation tank to allow solid particles like mud to settle. The settled water is then passed through sand and carbon filters, which help remove small particles and unpleasant odors. Next, the water is sterilized using chlorine, thiosulfate, and ethylenediaminetetraacetic acid (EDTA).
Chlorine is used to kill harmful microorganisms such as bacteria and fungi. A chlorine dose of 12 ppm is applied with aeration for four hours. Afterward, chlorine is neutralized with 4.8 ppm of thiosulfate, followed by two hours of aeration. EDTA is then added at a dose of 8 ppm to bind heavy metals that could be toxic to the cultured organisms. After this process, the water is transferred to storage tanks and is ready for use.
The use of chlorine-containing dolomite for water preparation: Banglele Indonesia
Tank and egg hatchery preparation
Sterilizing spawning and hatching tanks is a crucial step in ensuring the success of a vannamei shrimp hatchery. This process aims to eliminate pathogenic microorganisms, such as bacteria, fungi, and parasites, that can harm both broodstock and larvae.
The sterilization process begins by rinsing all tank surfaces with freshwater, which is effective in killing marine pathogens that cannot survive in non-saline environments. The rinse is applied thoroughly, including in hard-to-reach corners, to ensure no pathogens remain.
After the freshwater rinse, the tank walls are scrubbed with a coarse sponge and detergent to remove dirt and ensure all pathogens and organic material are cleared. The coarse sponge aids in scrubbing, while the detergent dissolves any grease or organic residues. After cleaning, the tanks are rinsed with freshwater to remove any detergent traces and then dried before use. Drying is essential, as moisture can promote microorganism growth.
Broodstock preparation
For vannamei shrimp spawning, typically 200 pairs of broodstock are prepared, consisting of 200 males and 200 females. Male and female broodstock are separated to ensure optimal gonad development in females.
Before spawning, female broodstock often undergoes ablation, which involves removing part of the eyestalk to accelerate gonad maturation. This technique has been proven effective in speeding up the production of hormones necessary for egg development, thus shortening the spawning cycle.
The ablation process of vannamei shrimp broodstock to accelerate gonadal maturation: BPIU2K Karangasem
In addition to ablation, proper feed management is another crucial factor in accelerating gonad maturation. The broodstock is fed a combination of fresh and artificial feed. Fresh feed, such as squid and marine worms, provides essential proteins and fats, while specially formulated pellets meet their nutritional needs. This balanced diet is vital for healthy gonad development.
Female broodstock typically reaches gonad maturity within five days after ablation. At this stage, the female is ready for spawning, as indicated by changes in the color of its back, signaling mature eggs. Proper gonad maturation and healthy broodstock conditions are key to successful spawning and high-quality seed production.
Vannamei shrimp spawning process
The spawning process in vannamei shrimp begins when the female broodstock reaches gonadal maturity, which is indicated by a distinct orange coloration on its back. This color signals that the eggs in the ovaries are ready to be released and fertilized. At this stage, the female releases pheromones, chemical signals that serve as biological cues to attract male broodstock. These pheromones stimulate the males, causing them to pursue the females for mating. Mating occurs naturally in the water, where the male shrimp quickly attaches sperm to the female's thelycum (a specialized reproductive structure) through copulation.
Broodstock with mature gonads display a reddish-orange color on their back: BPIU2K Karangasem
Once mating is completed, the male’s sperm remains attached to the female’s thelycum, ready for fertilization. Around 4 to 5 hours after mating, the female releases her eggs into the water, where external fertilization takes place. The eggs are met with the sperm attached to the thelycum, enabling the fertilization process. The success of fertilization and subsequent embryo development heavily depends on environmental conditions, particularly water quality. Fertilized eggs will begin to develop into larvae, progressing through several stages before reaching the post-larval phase, known as "PLs (Postlarvae shrimp)," at which point they are ready to be transferred to the grow-out stage.
