Barometric pressure, swim bladders and how fish sense the world
Course pack: Pressure-and-conditions log. Coach Willy, our virtual AI coach, can explain each step, set you a practice task and check your understanding.
Who it's for
You've done the basics and want to tighten things up. Aimed at pike, perch, zander, carp.
Where and when
Done on the bank. Best in: all.
What you'll work through
- 1Swim bladders: physostomes, physoclists and barotrauma
- 2What air pressure really does (and doesn't)
- 3Lateral line, hearing and murky-water lures
- 4Build a conditions plan you can test
Step 1: Swim bladders: physostomes, physoclists and barotrauma
Alright mate, let's get stuck into barometric pressure, swim bladders and how fish sense the world. I'll walk you through what to look for, what to try and how to tell whether it helped. We'll start with swim bladders: physostomes, physoclists and barotrauma, then work through a proper practice job at each step. Take it at your own pace and keep a few notes so you've got a useful plan for next time.
By the end of this step
Have a go at: swim bladders: physostomes, physoclists and barotrauma.
Willy’s take
Right, let's sort out the barometer myths with proper fish anatomy. Most of our fish have a swim bladder, a gas-filled bag that helps them float at the depth they want without effort. How they control the gas in it splits fish into two groups.
Physostome fish, like carp, pike, roach, bream and trout, have a tube linking the swim bladder to the gut. They can gulp air at the surface or burp gas out fairly quickly. Physoclist fish, like perch and zander, have no tube.
They have to move gas in and out through the blood using a special gland and a network of tiny blood vessels, which is much slower.
Why does that matter? Because perch and zander can't adjust fast to big depth changes. Reel one up quickly from deep water and its swim bladder can over-expand. That's called barotrauma, and you might see bulging eyes, a swollen belly or a fish that can't stay upright.
Bring deep perch and zander up slowly, keep them in the water, and return them quickly. If a fish can't stay down, ask the fishery for advice.
So the anatomy is real and important. But here's the honest bit: how much the weather's air pressure affects feeding is far less clear. That's what the next step is all about.
On the bank
Worked example
Imagine this: you're fishing for perch in 12 metres of water off a reservoir boat. You wind one up fast and its eyes are bulging and it floats belly up. Your mate who brings his fish up slowly has no problem.
Your turn: Swim bladders: physostomes, physoclists and barotrauma
- 1
Write down the depth you're fishing and the species you expect
- 2
If fishing deep for perch or zander, practise a slow, steady retrieve
That's the free sample — this is where it stops
The full step keeps going with the rest of the practice job, common mistakes and fixes, a check-your-understanding quiz and your Pressure-and-conditions log. Then 3 more steps, each with its own task, and Coach Willy on hand to talk it through.
Start this course free ↓
You've read the free sample
Start this course free
Free members choose one available course per calendar month. Joining doesn't use your choice — you pick when you're ready.
Join free to start this course