Spawning behavior of the European catfish

Vitali Dalke

Spawning behavior of the European catfish: peculiarities, behavior and the role of humans

The European catfish ( Silurus glanis ) is one of the most mysterious and largest freshwater predators. Its reproduction is a fascinating process that combines survival instincts and unique behavioral rituals. In this article, I explore the details of the spawning process, based on observations by ichthyologists and experiences by anglers.

Sexual maturity and spawning time

Catfish reach sexual maturity at the age of 3–4 years, at a body length of 45–70 cm. However, the first spawning attempts of young catfish are often unsuccessful: the eggs may remain unfertilized, and clutch size is small.

The time of spawning varies depending on region and weather conditions:

In southern areas: mid-May.
In temperate latitudes: end of May – June.
In cool spring: delay until July.

The decisive factor is the water temperature of 17–20°C . If the temperature drops, the spawning process is interrupted and only resumes when the temperature stabilizes.

Courtship and pair formation

Before spawning, catfish gather in groups near potential spawning grounds. Males fight aggressively for females. Interestingly, catfish Males are larger than females , which is in contrast to many other fish species. The winning male forms a temporary pair that lasts only for the spawning season.

After choosing a partner, the couple prepares a spawning nest A depression about 1 m in diameter in shallow water (0.5–1 m deep). Typical locations include vegetation, dead wood, or eroded shorelines. The male cleans the bottom with his fins and mouth.

Egg laying and the role of the male

The female lays large, sticky eggs (2–3 mm in diameter) that adhere to the nest floor. The amount depends on the size of the female:

Average: 25,000 eggs per kg of body weight.
Maximum: Up to 500,000 eggs.

After fertilization, the female leaves the nest while the male stays behind to guard the clutch:

Supplies the eggs with oxygen-rich water through tail and fin movements.
Aggressively defends the nest against predators such as other fish, ducks or even humans.

The incubation period is 3–5 days. Lower layers of fish carcasses often die due to a lack of oxygen, which, according to observations, can also lead to the development of albino catfish.

Development of the young animals

After 5 days, larvae hatch and initially remain in the nest for 10–14 days, feeding on the yolk sac. They then mature into juveniles and feed on microorganisms, and later also on crabs, worms, snails, and small fish.

Special features of the young catfish:

Light sensitive – hide under stones, dead wood or artificial structures (pipes, tires).
Form swarms that stay together for up to 2 years.
At two years of age they reach a length of 50–60 cm.

The male guards the brood for about 2 weeks until the young fish become independent.

Human influence and recommendations for anglers

During the spawning season, catfish, especially the guarding males, are very vulnerable. Recommendations for anglers:

Avoid fishing near shore from May to June.
Release captured males – their death endangers the clutch.
Do not disturb spawning grounds with noise or other activities.

After spawning, a An intensive feeding phase that makes catfish vulnerable. But only responsible fishing can safeguard their population.

Conclusion

The spawning behavior of the European catfish is a complex, little-researched process that demonstrates astonishing care for its offspring. Protecting this species requires not only scientific work but also human consideration. Remember: By protecting spawning catfish, you are contributing to the preservation of our waters!

Vitali Dalke