Measure a swim that you can fish repeatedly
On a lake as large as Lac du Bourget, the most useful first measurement is the depth where you can put a float accurately. A short pass just off a shelf can tell you whether a roach is feeding close to the bed, taking bait on the fall or simply absent from that particular lane. A long cast into unmeasured water mixes all three questions together.
The Aix-les-Bains angling association identifies the Rossignoli pontoon as a fishing location on the lake. It is a practical place to start planning a bank session, subject to current access and signs. Use only the permitted position, keep walking and mooring areas clear and leave marked reserves and reed enclosures alone. A public lake does not make every harbour berth or swim available. Have a second permitted bank option so that a crowded pontoon or a wind blowing directly into it does not dictate the whole session.
Know the target and how it feeds
Common roach, Rutilus rutilus, is the gardon of French freshwater guides. It is widely distributed in Europe and uses lakes and slow or sheltered reaches of rivers. Its silver flanks, often reddish eye and fins, and the dorsal fin beginning around the level of the pelvic fins help distinguish it from rudd. Rudd usually have a more upturned mouth and a dorsal fin set farther behind the pelvic fins. Young fish can be hard to separate, and redness alone does not establish the species. Look at the mouth and fin placement together before recording the fish.
Roach eat small invertebrates as well as plant material, algae and detritus. Research in the south-Alpine Lago Maggiore documented a varied diet and changes between seasons, including more zooplankton in summer and a mixture of algae, bottom organisms and detritus in early spring. Those are observations from another lake, not measurements at Bourget. The practical implication is to test both a suspended fall and a bait just off the substrate. A fish turning in midwater may never see a bait anchored to the bottom. A shoal feeding down on a shelf may pass under a bait that takes too long to arrive.
Use the lake surface to pick a first lane
On a cool December outing, a sheltered bank in good daylight is a useful first comparison. A calmer surface makes tiny lifts and sideways movements visible, and a midday visit may be easier to control than a dawn start in cold wind. There is no verified local best hour. When boat wash or a crosswind keeps pushing the float out of the feed area, change the cast and shotting before assuming the fish have stopped feeding.
Plumb at two or three reachable distances with a small clip-on weight. Lower the plummet or cast it gently, adjust the float until the hook is just at the bed and note the setting. A sudden increase in depth over a short distance can mark the foot of a shelf. Fish where you can land and retrieve without crossing posts or cables. If the plummet returns coated in soft sediment, set the hook a little above bottom so it remains visible. Avoid using the plummet as a grapple through weed.
Fix a waggler for a shallow shelf
A 3.6–3.9 m float rod, 2000–2500 spinning reel and 3–5 lb sinking mono are sensible starting choices. Fit a small bottom-attached waggler carrying about 1.5–3 g, locked with appropriate non-toxic shot or float stops. Tie a 20–35 cm hooklength of roughly 2–3 lb fine nylon to the main line using a loop-to-loop connection or a small swivel. Start with a single size 16–20 hook and a small piece of bread flake or one permitted bait larva. Leave the point clear. The ranges are practical starting suggestions, not local tackle requirements.
Set the hook about 10–20 cm above the measured bed. Place most of the shot close to the float to cast cleanly, with a couple of smaller droppers down the line to make the bait settle gradually. Test the balance in the margin and leave enough tip showing to distinguish a real bite from ripple. Feather the cast into the chosen lane. After the float lands, dip the rod tip and wind gently to sink the line between rod and float. That makes the line less likely to tow the bait sideways on the surface.
Watch for a steady disappearance, a sideways glide against the drift or a tip rising when a fish lifts the lowest shot. Make a small, controlled lift rather than a broad strike. Keep the rod bent as the fish comes in and use a landing net from a high bank. If a bite comes before the float has fully settled, count the fall on the next cast and raise the setting slightly. If bites only come once it has settled, test a little lower before feeding more.
Slide the float when the shelf drops away
When the depth is too long for a fixed rig to cast cleanly, tie a soft stop knot to the main line and add a small bead, a sliding waggler, and a concentrated group of shot above the hooklength connection. A float carrying around 3–5 g is a starting point where wind and depth call for it. Keep a 25–40 cm light hooklength and a single size 16–18 hook. Slide the stop to the measured depth, confirm it passes through the guides, and make a smooth lob rather than a snap cast. The grouped shot pulls line through the float until it reaches the stop. A small dropper lower down allows the bait to settle after the main group.
Wait for the float to stand properly. If the tip remains too high, check for bottom contact or a jammed stop before treating it as a lift bite. The sliding rig is good for a deeper clean lane, while the fixed waggler makes it easier to compare a slow fall in shallower water. A short pole with a light float can be an option at a calm near-bank swim with room to ship the pole back. It places the bait precisely but cannot reach a deeper shelf beyond the tip.
| Swim signal | Start with | Change after a blank test |
|---|---|---|
| Shallow measured shelf and calm water | Fixed waggler, spread droppers | Lower the bait a small step |
| Deeper clean water and manageable drift | Sliding float and compact shot group | Check stop depth and bait condition |
| Bites on the fall before float settles | Fixed float with a slower fall | Raise the bait and keep the lane constant |
| Persistent weed or wash | Shorter cast into a clearer lane | Move if the float cannot settle |
Fish one swim, then make a measured change
Imagine the near lane plumbs at two metres and the next cast drops substantially. Start on the near shelf with a 2 g fixed waggler, one bread fragment and the bait just off bottom. Make several casts to the same point. If a fish takes as the bait is falling, spread one small shot and repeat. If the float is quiet but the bait comes back clean, lower it by 10 cm. When a longer cast makes the fixed rig tangle, switch to the slider for the deeper lane. Give that lane enough casts to compare, then return to the first setting if the wind rises. In cold water, avoid throwing in handfuls of feed to repair a depth problem. If feeding is allowed, use a modest amount of suitable bread feed and avoid loose larvae.
Separate wind drift from a feeding response
On the next cast, watch the float against a fixed point across the lake. If it drifts faster than the surface debris after you tighten up, the line is likely towing it. Sink the line and leave a small controlled curve. If the float still moves too fast, make a shorter cast and use a stable waggler with slightly more carrying capacity. Put the extra weight where it helps the cast, rather than putting it all at the hook and changing the fall you meant to test.
When bread comes back intact and the float never settles consistently, measure the depth again before changing bait. If the float does settle and the bread returns compressed, pinch a smaller piece around the shank with the soft part free. That gives you a different test from simply adding more feed. Record the float, hook setting and the stage of the fall that produced any bite before moving.
Rules and release
Check the Préfecture de la Savoie lake order, current annual updates, fishing card and posted reserve boundaries. This plan uses one ordinary single-hook line. The lake has specific fish consumption restrictions, including roach over 10 cm under the published order. Treat this outing as catch and release, and verify the rules before any retention. Use a wet net, keep the fish low and return it promptly.