Foods & cuts · Rainbow trout
Whole trout
A whole round fish, gutted, cooked over direct heat until the flesh is opaque and lifts from the bone. The skin is structural — it is what holds the fish together on a grate.
What it is
- Form
- Whole fish
- Typical weight
- 250–400 g
- Typical thickness
- 35–50 mm
- Cut
- Not a cut of anything
Why it behaves as it does
A whole fish is a closed cavity, so heat arrives from both faces and travels through skin on each side. The doneness test the FSA gives for fish generally — opaque and separating easily with a fork — is easier to apply here than on a fillet, because the flesh either lifts cleanly from the backbone or it does not. BBQHQ holds no retrieved duration for whole trout and does not borrow the salmon fillet's, because a fillet is an open slab cooking from one face and that is a different problem.
When is it done?
Food-safety endpoint
Food Standards Agency
In the UK, fish is cooked when the flesh has turned opaque — no longer transparent — and separates easily with a fork.
The rule and its source
In the UK, fish is cooked when the flesh has turned opaque and separates easily with a fork. The regulator gives no temperature for fish.
Well established
Food Standards Agency — States this directly
“fish flesh should turn opaque (no longer transparent) and separates easily with a fork”
- How it was measured:
- A visual and textural test, not a thermometer reading. The same document gives 70 °C for 2 minutes as the general combination for food, and does not apply a figure to fish.
- Where it applies:
- England, Wales and Northern Ireland.
About this source · Original · retrieved 2026-08-16
Texture endpoint — how you actually know
Flesh lifting cleanly from the backbone
The flesh at the thickest point behind the head has lost its translucency and lifts away from the bone in one piece rather than clinging to it. On a whole fish this is a better test than the fork-flake, because the part that finishes last is the part against the spine and the only way to see it is to look there.
Where this comes from
Fish is timed by thickness rather than by weight. Clemson gives ten minutes per inch at 450 °F in an oven, with five minutes added in foil or sauce and double for frozen fish; Weber gives 8–10 minutes per inch on a grill. Doneness is a physical signal — the flesh just begins to flake and loses its translucency.
Well supported
Clemson Cooperative Extension — States this directly
“bake for 10 minutes per inch thickness of the fish, turning the fish halfway through the cooking time”
- Method:
- Stated for baking at 450 °F, NOT for grilling. The oven is the assumed appliance.
- How it was measured:
- Measured at the thickest point, after stuffing or rolling if either applies.
- Add 5 minutes if cooked in foil or in a sauce; double to 20 minutes per inch for fish cooked from frozen.
About this source · Original · retrieved 2026-08-13
Weber-Stephen Products LLC — States this directly
“General rule for grilling fish: 4 to 5 minutes per ½ inch thickness; 8 to 10 minutes per 1 inch thickness.”
- Form:
- Expressed per unit of thickness rather than per portion.
- Close to but not identical with Clemson's 10-minutes-per-inch rule, which assumes a 450 °F oven rather than a grill.
About this source · Original · retrieved 2026-08-13
Clemson Cooperative Extension — States this directly
“Fish is cooked when its meat just begins to flake easily when tested with a fork and it loses its translucent or raw appearance.”
- Form:
- A physical signal rather than a temperature — the shape a texture endpoint takes.
About this source · Original · retrieved 2026-08-13
How long it takes
Whole trout, indirect heat
Estimated cooking window
13 min–24 min
Moderate confidence
Why this is a range, not a number
- Thickness varies between pieces
- Weight varies within the range this covers
- Cookers hold temperature imperfectly
- How often the lid comes off
Cook to the endpoint, not to the clock. The window tells you when to start checking.
What this rests on
BBQHQ publishes a window for this cook.
- Observations
- 1
- Documents
- 1
- Publishers timing this cook
- 1
Clemson Cooperative Extension
Why confidence is not higher
- The window is BBQHQ's arithmetic on a source's per-unit rate, not a window the source published.
- Several documents, but all from one publisher.
- At least one source does not state the cooker temperature.
How the sources were combined
ONE PUBLISHER, AND IT IS THE ONE THAT SEPARATES WHOLE FISH FROM FILLETS. Clemson gives whole fish 10-12 minutes per inch of thickness, cooked COVERED, turning halfway — a different instruction from the same page's fillet guidance, which is why this profile is indirect and the cod profile is not. Weber and ASMI both publish fish rates and neither distinguishes the form, so neither can corroborate a figure that is specifically about whole fish; citing them here would convert a silence into agreement. The window is BBQHQ's arithmetic on Clemson's rate across a 35-50 mm envelope, measured at the thickest part of the fish behind the head.
What makes the window as wide as it is
- Thickness varies between pieces
- Weight varies within the range this covers
- Cookers hold temperature imperfectly
- How often the lid comes off
When it goes wrong
- It came out dry
- The fish came out dry — 2 distinguishable causes.
- It stuck to the grate
- Food sticking to the grate — 2 distinguishable causes.
- It fell apart
- Fish falling apart on the grill — 2 distinguishable causes.
Afterwards
Cooling, keeping and reheating what is left is general guidance for barbecue leftovers. Neither UK authority publishes anything specific to whole trout, and BBQHQ does not invent a distinction they do not make.