In Indonesia’s freshwater aquaculture—and increasingly in markets worldwide—Pangasius catfish have emerged as a leading commodity. Rising market demand, a flavor widely enjoyed by consumers, and relatively stable prices make Pangasius cultivation a promising venture for farmers. It is no surprise, then, that Pangasius farming is attracting both novice and large-scale producers.

However, beneath Pangasius’s commercial potential lies a crucial factor: the quality of the broodstock. High-quality fry (seed fish) can only come from parent fish that are robust, disease-free, and have fully mature gonads (reproductive organs). Selecting the right broodstock is therefore a vital first step in ensuring that the breeding process produces strong, healthy offspring with rapid growth.

Why broodstock selection is important?

Choosing the right broodstock is the foundation of a successful breeding program. Superior broodstock produce eggs with high fertility and sperm with strong fertilizing power. As a result, their offspring inherit good genetic quality and strong resilience. Studies have shown that hatching success from eggs of healthy broodstock can exceed 80%, whereas it can fall below 50% when the broodstock are of poor quality.

By contrast, mistakes in selecting broodstock can have serious consequences. Fry from parents of unknown or poor condition tend to grow slowly, be more susceptible to disease, and vary widely in size. Even more concerning, repeatedly using the same broodstock without proper genetic management can lead to inbreeding. Inbreeding is dangerous because it dramatically reduces the genetic quality of the fish from one generation to the next.

Unfortunately, many farmers still rely on traditional spawning methods without regard to these basic breeding principles. Most focus on the number of parent fish rather than their quality. Indonesia’s Directorate General of Aquaculture (DJPB) reports that about 35% of Pangasius farmers in major breeding centers continue to use older broodstock of unverified quality. The result is often inconsistent fry quality, lower survival rates, and higher production costs.

Characteristics of good pangasius broodstock

Generally, good Pangasius broodstock share certain key traits. These include:

• Healthy and robust: They should appear vigorous and free of physical deformities or disease.
• Rapid growth and vigor: Broodstock should grow quickly and display active, strong behavior.
• Proper age and size: Mature fish (typically older than 2.5 years and at least 3 kg in weight) tend to produce the best gametes.
• Good nutrition and physiology: A balanced diet and overall good health support fully developed gonads.
• Full, rounded abdomen: A well-filled belly often indicates that the ovaries or testes are developing properly.

Spawning-ready female pangasius catfish

Mature female broodstock exhibit distinct physical signs that indicate they are ready to spawn. Their bodies tend to be relatively short and broad, with a noticeably distended belly toward the tail end. Running a hand along the abdomen, one feels that it is soft and smooth—a sign that the ovaries are full of eggs ready for release. The female’s genital area also appears slightly swollen and dark red, and the skin around the belly becomes thinner and more elastic.

Mature female pangasius broodstock: BPBAT Sungai Gelam

An ideal female for spawning is typically older than 2.5 years and weighs at least 3 kilograms (about 6.6 pounds). Field data from the Directorate General of Aquaculture suggest that well-conditioned females above 3 kg can produce between 80,000 and 120,000 eggs each. With proper handling, these eggs can achieve hatching rates above 80%.

Another readiness test is the egg-stripping method. By gently pressing near the genital opening, a farmer can strip out eggs. Spawning-ready eggs come out uniformly, are round, and appear mature. Uniform egg size is important because it leads to fry that are similar in size, making it easier to manage the young fish as they grow at the same rate.

In hatchery practice, eggs from the female are often collected using a catheter or cannula and then examined to confirm maturity. Pangasius eggs ready for spawning are typically about 1.0–1.2 millimeters in diameter, have a cloudy appearance, are consistent in size, and contain a centrally positioned yolk nucleus. Eggs meeting these criteria have high fertilization success, which in turn supports the production of high-quality fry.

Male broodstock ready to spawn

In broodstock selection, male pangasius often present a more streamlined profile than females, their bellies relatively flat and elongated. A key external indicator of a mature male’s readiness is a swollen, pinkish-red urogenital area. Farmers typically verify this by gently massaging the abdomen near the genital opening; if the male is ripe, a thick white creamy fluid – sperm – will emerge. Veterinarian guidelines note that mature males at spawn time release copious milky sperm, whereas immature ones yield little or none. In practical terms, this thick, viscous sperm suggests a high concentration of motile cells, which maximizes fertilization potential. Under ideal conditions, a single vigorous male can produce enough sperm to fertilize the eggs of one or even two females in a spawning event.

Healthy male broodfish ready to spawn are typically at least two years old and weigh around 2 kilograms or more. (Smaller, younger males often do not produce sufficient sperm.) Broodstock programs have confirmed that males in the 2–2.5 kg range yield especially high-quality sperm: most of their sperm cells are vigorously motile and capable of effectively fertilizing eggs. In contrast, males below this size often have lower sperm motility and fertility.

Gonad maturity level

Beyond these physical signs, hatchery managers also assess the gonad maturity level (GML) of each broodfish. GML – sometimes called the gonad maturity index (GMI) – is a staging system that describes ovary or testis development from early growth through final ripeness. Knowing the GML helps farmers time the spawning precisely for the best yield of eggs and sperm. In practice, GML can be gauged by cannulation: a thin catheter is gently inserted to sample a few eggs from the female’s ovary, which are then examined under a microscope. This minimally invasive method works well with large-gonad fishes like pangasius, offering a quick snapshot of maturity without sacrificing the fish.

Researchers divide both female and male pangasius broodstock into five maturity stages (Stage I through Stage V), described roughly as follows:

• Stage I: 
  • Female: Ovaries are thread-like and translucent, extending only a little way forward in the body. The surface is smooth and no distinct eggs are visible. 
  • Male: Testes are also thread-like, small and pale, tucked near the body cavity; sperm cells are not yet obvious.
• Stage II: 
  • Female: Ovaries grow larger and take on a deep yellow color, but individual eggs (oocytes) are still not clearly visible. 
  • Male: Testes increase in size and turn milky-white, their shape more defined than at Stage I.
• Stage III: 
  • Female: Ovaries are now yellow and the developing eggs can be seen with the naked eye. 
  • Male: The surface of the testes looks serrated or grainy; it is brighter white and tissue may begin to break apart easily if handled.
• Stage IV: 
  • Female: Ovaries swell further, with yellow eggs filling about half to two-thirds of the body cavity. Intestines are pressed aside. The eggs are mature, distinct, and separate easily. 
  • Male: Testes become dense and fill the body cavity; they remain milky white in color and are full of sperm.
• Stage V: 
  • Female: Ovaries become flaccid with a thick wall, indicating that most eggs have been released; only a few residual eggs remain near the genital opening. 
  • Male: The posterior portion of the testes is somewhat collapsed, though the part near the vent may still contain sperm.

Most experienced hatcheries time spawning when broodstock reach Stage IV. At this point the female’s eggs are fully mature and amber-yellow, ready to be released, while the male’s testes are at peak capacity to produce and release sperm. (In technical terms, Stage IV eggs of pangasius are about 0.9–1.0 mm in diameter, ivory-yellow, and non-sticky – an ideal state for fertilization.) By holding broodfish until Stage IV, farmers ensure that eggs and sperm are both at optimal quality for a strong fertilization success.

Male pangasius broodstock (top) and female pangasius broodstock (bottom): BPBAT Sungai Gelam

Other factors determining gonad quality

Good broodstock nutrition is critical because gonad development demands a great deal of energy and building blocks. During the maturation phase, fish should be fed high-quality diets rich in protein (on the order of 30–35% protein) and supplemented with essential vitamins and minerals. In fact, research shows that feeding pangasius broodfish a diet with about 35% crude protein and a vitamin premix produces the most robust reproductive results. Vitamins E and C in particular are known to support egg and sperm health, and some hatcheries fortify broodstock feed with these nutrients. Essential minerals like calcium and phosphorus are also important; they help strengthen egg membranes and contribute to healthy embryo development. In many breeding centers (especially in South Sumatra), farmers supplement commercial pellets with natural foods – for example, small “trash fish,” snails or other invertebrates – to round out the diet. These additions provide a broader spectrum of nutrients, and anecdotal evidence suggests they can raise egg quality significantly compared to pellets alone.

Equally important is managing the pond environment. Broodstock should be kept in clean water within the optimal temperature and oxygen range. Ideal conditions are roughly 27–30 °C, with dissolved oxygen not falling below about 4 mg/L. Under these conditions pangasius broodfish experience minimal stress, allowing their gonads to mature properly. Pond density must also be kept low (typically around 2–3 fish per square meter) so that the adults are not crowded. Overcrowding can induce stress hormones and retard gonad development. In sum, careful attention to diet, water quality, and stocking density – in addition to age and size – is key to producing high-quality broodstock and maximizing fertilized egg yields.