IJsselmeer

The food chain of the IJsselmeer

Reading this water starts on the bottom. Much of the hard substrate is carpeted with zebra mussels; they filter the water clearer and form the base of the food web. On the mussel-rich stretches our data turns up tench, rudd and pike strikingly often. Over the barer, deeper sand the picture shifts: here it is about mysid shrimp, and pikeperch tend to sit with them. One small fish gives away the health of the whole system — when the smelt do well, predators and birds profit alike.

The water plants of the IJsselmeer

Below the surface, water plants decide where life gathers. Stoneworts belong to clear, clean water — where they stand, visibility is usually good. Pondweed grows here too, a classic submerged plant that gives young fish cover — and where young fish shelter, the predators come to hunt.

Invertebrates and prey

The engine of the food web sits on and in the bottom. Midge larvae are one of its most important food sources — almost every bottom fish grazes on them. Freshwater shrimp go hand in hand with smelt here, and where the smelt are, the predators follow. On the harder patches, pea mussels lie among the zebra mussels; together they filter the water and keep the bottom alive.

Microlife at the base

At the base of it all sits the microscopic life. Diatoms — tiny algae with a skeleton of glass — capture the sunlight and feed the whole chain above them; in our data they run together with species like pike and twaite shad. In warm, nutrient-rich water blue-green algae can take over, which shows up in the algae pressure on this water. Small life, big consequences.

Pikeperch

Pikeperch is the signature predator of the IJsselmeer and loves the transitions: channel edges, deeper holes and the flanks of sandbanks. Coloured, wind-churned water works in its favour — then it hunts by day too. Vertical fishing or trolling along those channel edges is the classic approach; from the bank, groynes on a rising level are the pick.

Perch

Perch shoal up and hunt small stuff — smelt and young coarse fish. Look for them around structure: groynes, rip-rap, the tips of sandbanks and the mussel-rich bottom where their prey sits. Where the wind packs baitfish together, the perch gather with them. Small shads and vertical jigging do well along the harder ground.

Pike

Pike avoid the bare open water and seek the sheltered, structure-rich edges: harbour mouths, shallow weeded banks and the drop from sandbank to deeper water. When an onshore wind pins baitfish against the bank, pike wait in the calm behind it. Big shads and jerkbaits along those edges — the IJsselmeer produces genuine metre-plus fish.

Carp

Carp are often overlooked on the IJsselmeer, but there is fish of serious size here. You can skip the bare open water: your chances sit in harbours, sheltered corners behind groynes and along shallow, faster-warming banks. An onshore wind that piles food against your bank can make the session.

Eel

Eel is a night hunter that tucks away by day among rip-rap, in harbours and along the softer bottom. Fish at dusk and after dark with a bottom rig close to that structure. The IJsselmeer has always been strong eel water, but the species is under heavy pressure: eel has a closed season from 1 September to 30 November, and given the stock you're best releasing what you catch anyway.

Bream

Bream — with roach and silver bream alongside — move in huge shoals over the flat bottom, feeding on bottom life around the mussel beds. They are mobile: where the wind colours the water and stirs up food, the shoal gathers. Feeder tactics or a weighted bottom rig on the channel-to-plateau transitions work best.

Notable species

The most remarkable story is the return of migratory fish. The North Sea houting — a whitefish that shuttles between fresh and salt — is present here again after years away, which says something about restored fish migration along the Afsluitdijk.