Fishing reservoirs: changing water levels, moving fish

At first glance a reservoir looks like any other lake, but there is one important difference: its water level is controlled by people. Flood protection, irrigation, water supply or power generation can bring changes of a metre or more within a few weeks. Anglers who take this into account find fish far more easily than those who treat a reservoir like an ordinary lake.

What types of reservoirs are there?

Broadly speaking, it is worth distinguishing two types:

• Hill reservoirs behind a valley dam: a stream or river valley is closed off by a dam. The water is deeper near the dam and gets gradually shallower towards the inflow, with the old stream bed still running along the bottom.
• Lowland reservoirs: large, shallower on average, often including floodplains, oxbows and channels. The best-known Hungarian example is Tisza-tó (Lake Tisza), created by the Kisköre barrage and the country's largest artificial lake, where the level is managed seasonally and is typically lowered for winter.

In both cases, the underwater landscape was once dry land: roads, field boundaries, tree lines, old channels and pits may survive down below.

The shape of the reservoir bed

On a reservoir, you need to read the former landscape beneath the surface:

• The flooded old channel: the fish's "motorway". It is deeper, water movement is more noticeable, and predators and bigger carp like to move along it.
• The dam area: usually the deepest part. Note that fishing on the dam itself and around structures and sluices is often banned or restricted.
• The inflow: fresh, oxygen-rich water and drifting food. A prime spot in spring and in hot weather, though it can also be silted up and shallow.
• Submerged trees, bushes, rock piles: favourite haunts of zander and perch, but snaggy.
• Bays and shallow plateaus: they warm quickly, and in spring and early summer fish feed and spawn here.

Rising and falling water

On a reservoir, the water regime is the strongest "weather factor":

• When the level rises, fish follow the water onto freshly flooded, food-rich shallows. This is a good time to fish closer in, even near the bank.
• When the level falls, fish retreat to deeper areas, the old channel and its edges. Shallow bays may empty out.
• When the level is stable, the reservoir behaves like a lake and the usual seasonal patterns apply.

It is worth following the reservoir's water level before you set off, and reading the signs on the bank too: a fresh strip of mud, exposed vegetation, a shifted shoreline.

Fish species

Reservoir stocks depend on the catchment and on stocking. Typical species include carp, grass carp, bream-type fish and silver or bighead carp, and among predators zander, pike, catfish, asp and perch. Zander often hold along the old channel and around snags, asp hunt on open water, and pike patrol the shallow, weedy areas.

Methods are just as varied: feeder or boilies for carp along the edge of the old channel, jigs or soft plastics for zander next to submerged snags, and long-casting lures for asp on open water. On large, windy reservoirs the windward bank is often better, since food drifts there, but waves can make bite detection and boating harder.

Reservoir water quality can fluctuate: in nutrient-rich water, algal blooms and then oxygen shortages can develop in summer, and fish are sensitive to this. In such conditions the windy, better-mixed bank, the inflow area or deeper water may be the better choice. If you see dead fish, report it to the manager.

Rules and safety

Most reservoirs are managed by angling clubs or water authorities and have their own regulations. On reservoirs used for drinking water supply, fishing may be banned or heavily restricted. No-fishing zones around the dam and structures, rules on boats and baiting, and nature conservation restrictions are common. In Hungary you need a state fishing licence, a catch log and a ticket for the water; elsewhere follow the national licensing rules. Always check the manager's current fishery rules – size limits and closed seasons can differ from water to water.

Changing levels are also a safety issue: when the water drops, muddy banks can be treacherous, and when it rises, tackle left at the edge can be reached by the water. Wear a life jacket in a boat and watch out for trees and stumps sticking up from below the surface.

Quick checklist

1. Check the current water level and which way it is moving.
2. Map the old channel and the inflow.
3. Look for fish shallower on rising water, deeper on falling water.
4. Check no-fishing zones and the fishery rules.
5. Handle fish gently and take your rubbish home.

Summary

A reservoir is dynamic water: changing levels rearrange where the fish are, and with it the key to success. If you follow the water regime, read the former landscape beneath the surface and stick to the rules, a reservoir has surprises in store all year round. Our map search makes it easy to see which reservoirs and other waters are within reach.