Proven Sudoku
Cannibalism
Also called Cannibalistic fish, Self-eliminating fish.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
When a square belongs to both halves of the fish at once. It gets counted twice, and the fix is to remove the number from that square itself.
The exact rule, for stronger players
The rule, stated exactly: A fish where an eliminated candidate lies inside a base set. The elimination remains valid and removes a candidate the pattern itself used.
What it removes: Remove the candidate as normal, including from base cells.
Why it works: Base membership does not protect a candidate. If the counting argument excludes it, it goes, even though it participated in the pattern.
Worked examples
None yet. This pattern does not turn up in our daily boards, so there is no real example to show. We would rather wait than draw a fake one.
Learn these first
- Mutant FishA fish where rows, columns and boxes can be mixed freely on both sides.
Related complex fish
- Complex Fish (rank framework)The fish idea, but boxes are allowed to join the rows and columns.
- Endo-FinA spare square that sits inside two parts of the pattern at the same time.
- Finned FishA fish pattern with one extra square hanging off it.
- Franken FishA fish where a box is allowed to join in with the rows and columns.
- Kraken FishA fish that does not quite work.
How often does it come up?
Our rough estimate: rare and counterintuitive, which is why it deserves its own page.