Catfishing in Midsummer: How to Turn Scientific Knowledge and Real-World Practice into Trophy Catches

When the thermometer relentlessly climbs in July and August and the water temperature exceeds the magical 25 degrees Celsius mark, most predatory fish fall into a summer lethargy. Pike and zander reduce their metabolism to a minimum and remain almost unapproachable in deep water.

But for us catfish anglers, now is the golden hour. The European catfish (Silurus glanis) only reaches its peak performance in these extreme temperatures. To be successful in midsummer, however, we must understand the fish's biology and translate this knowledge into a clear tactic for the fishing waters.

The Catfish in Midsummer – What Does Science Say?

While native fish species suffer significant heat stress at high water temperatures, the catfish, as a warm-loving (eurythermic) species, is an absolute winner in midsummer. Its physiological optimum for metabolism and growth is extremely high – scientific studies put this at 25 to 28 degrees Celsius. Only beyond the 30-degree mark does its organism reach its limits.

Biological and telemetric studies (including by Santos et al., 2024, and Maiditsch & Ladich, 2014) paint a fascinating picture of catfish behavior at peak summer temperatures:

The Thermocline Anomaly (Inverted Vertical Behavior)

Contrary to the widespread belief that catfish exclusively stay in the coolest, deepest holes on hot summer days, radiotelemetric investigations prove the opposite:

During the day in shallow warm water: Catfish specifically use heated surface and shallow water as a "metabolism booster". They often spend the sunny hours in surprisingly shallow, warm zones or just below the water surface in open water (pelagic zone).

At night into the deep: As soon as the sun sets, the pattern completely reverses in midsummer. While in spring the fish move shallow at night, in summer they often migrate to deeper layers after dark or patrol along the thermal stratification (thermocline), as many prey fish also retreat there.

The "Super Hearing" at High Temperatures

It is known that catfish have excellent hearing. However, researchers (Maiditsch & Ladich, 2014) found that their sensory performance correlates directly with water temperature. With a temperature increase from 15 degrees to 25 degrees Celsius, the hearing sensitivity of the catfish increases by over 10 decibels. Especially in the frequency range between 300 Hertz and 4 kilohertz – exactly the range in which struggling prey fish or movements in the water occur – the catfish hears extremely sharply in warm summer water.

Adaptation to Oxygen Deficiency (Hypoxia)

Warm water physically stores significantly less oxygen. If the oxygen concentration in deep, stagnant water in midsummer drops below 5 mg/l, many fish species suffer from shortness of breath. Catfish have a relatively high tolerance to oxygen deficiency, but strategically adapt their behavior: they completely avoid oxygen-free deep zones and specifically seek out areas with strong water movement and currents.

Angling Practice – Tactics, Spots, and Bait Selection

How can these fascinating scientific findings now be translated into concrete catches? Here, biology and years of practical experience on the water come together.

1. The Magic Morning Window for Big Catfish

Most anglers pack up in midsummer as soon as the sun rises. However, my personal experience shows a completely different picture: Especially in very warm water, the truly large catfish bite surprisingly often in the early morning right at sunrise. Sometimes the feeding window even extends further, when the sun is already high in the sky and shining brightly on the water.

Vitali Dalke with a large catfish that bit in the early morning directly in front of his feet on a dead bream on the bottom of a reservoir.

My theory on this:

In the early morning hours, it is coldest, and the shallow water cools down minimally overnight. This slight cooling and the associated oxygen boost magically attract whitefish – they move into the shallows and become active again. The catfish, as a clever predator, simply follows its prey fish and ruthlessly exploits this short, productive time window!

While smaller catfish are often active in the first hours of the night, the true giants utilize precisely this cool transition phase into the day. Those who pack up too early in midsummer often miss the fish of a lifetime! Therefore, leave your rods untouched until late morning.

2. The Secret Weapon in Summer: The Large Dead Baitfish

I have repeatedly found that a large, dead baitfish is often significantly superior to a live bait in midsummer. This has a logical, biological background that directly ties into the summer oxygen deficiency.

Since larger quantities of whitefish regularly die in warm water, the catfish, as an efficient energy saver, adapts to this. It immediately realizes that the riverbed in summer is practically covered with "free food" in the form of freshly deceased fish. By focusing on consuming these dead fish, it saves valuable energy during hunting. A generous, immobile dead baitfish or a fat fillet piece fits perfectly into its prey pattern in summer.

3. Spot Selection Based on the Oxygen Principle

If the water is thermally stratified in midsummer, you need to find the oxygen-rich oases:

In the river: Focus on fast-flowing areas, weirs, turbine outlets, and especially inlets of streams or smaller rivers. Here, the water is constantly enriched with oxygen.

In the lake: Use the wind! The shoreline where the summer wind pushes (onshore wind) transports oxygen-rich surface water downwards. Similarly, extremely dense underwater weed beds are true oxygen factories during the day, where catfish gather.

4. Presentation Day and Night

Utilize the temperature-dependent migratory behavior of the fish for your rig:

During the day: Look for fish in shallow water, dense weed beds, or directly below the surface. Set rigs on weed edges or a pelagic presentation in open water are unbeatable now.

At night: Offer your baits on steep drop-offs that lead to deeper water, presenting them just above the thermocline. Bottom fishing on shallow sandbanks or directly in the bank area often brings bites right at your feet.

Absolute silence: Since the catfish's hearing is at its peak in warm water, absolute quiet at the spot is paramount. Avoid any thudding in the boat or loud steps on the bank. If you use a clonk, use it extremely sparingly – a few precise strikes are enough.

This trophy catfish was caught in midsummer right behind a water lily bed.

THE MIDSUMMER CHEAT SHEET

Sunny day & morning:

-Area: Shallow water, weed beds, near the surface.

-Tactic: Line-tensioning at weed edges, pelagic presentation. Large catfish often use the sunrise phase and the first strong sun rays for aggressive bites!

Mild summer night:

-Area: Steep drop-offs into deeper water, shallow sandbanks, direct bank areas.

-Tactic: Buoy rigs just above the thermocline or bottom fishing in shallow areas.

-Bait tip: A large, fresh dead baitfish.

Oxygen deficiency:

-Area: River and lake.

-Tactic: Fish directly in strong currents, in the backwater of weirs, at stream inlets, or on windward banks.

Conclusion

Midsummer is not a slow period. Anyone who understands that catfish love the warmth, get active again at dawn, and are grateful takers of dead baitfish in warm water will experience golden hours on the waters.

Good luck fishing,

Vitali Dalke