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This webpage contains spoilers for Fish Tycoon, a game from 2004 by Last Day of Work. Revealing the secrets of Isola's ecosystem may spoil the fun. Click to show contents anyways.

Fish Tycoon
🐠gameplay guide🐡

Breeding

Genetics

Every fish holds exactly two genes: a fin gene and a body gene. Each gene has exactly 21 alleles, listed below in the game's internal order.

Index Fin gene Body gene
0 Silky Shark
1 Tiger Catfish
2 Hornet Arrowfish
3 Fanned Snout
4 Pink Fatfish
5 Snubbed Snooper
6 Wasp Goldshark
7 Canary Fire-Arrow
8 Orange Fruitfish
9 Oriental Flashfish
10 Golden Goldbulb
11 Crimson Comet
12 Spined Stickfish
13 Stubby Grouper
14 Speckled Leaffish
15 Razorback Carp
16 Greenfin Beta
17 Great-sail Pigmy
18 Flagged Bananafish
19 Finless Quicksilver
20 Twin-fin Spotanus

Any combination of alleles is possible, so 441 species exist, with seven species considered the Magic Fish of Isola. Obtaining all seven is the goal of Fish Tycoon.

  1. Greenfin Spotanus, the Magic Fish of Fertility
  2. Speckled Leaffish, the Magic Fish of Sustenance
  3. Crimson Comet, the Magic Fish of Curing
  4. Oriental Goldbulb, the Magic Fish of Growth
  5. Orange Snooper, the Magic Fish of Health
  6. Wasp Grouper, the Magic Fish of Mutation
  7. Canary Fire-arrow, The Golden Guppy

When fish reach age 20 (1h40m), they can breed. One fish impregnates another other fish. The latter cannot breed again until it gives birth; the former is able to breed again immediately. The sex of fish is not tracked in Fish Tycoon.

The fin gene of the child is determined as a function of the parents' fin genes. The body gene of the child is determined as a function of the parents' body genes. Two particular parent species will always produce the same species of offspring.

This function is very easy to compute! If $x$ and $y$ are the indeces for the parents' fin genes, then the child's fin gene will be $\lfloor(x+y)/2\rfloor$. This computation is the same for body genes.

Breeding planner

In order to obtain a particular species as efficiently as possible, you should catalog the fish you currently own and determine which offspring can be made. This computation can be performed using a variant of Dijkstra's algorithm.

In the table above, click on a fish to select it as a fish you already have. Then shift click on a fish to compute the fastest way to breed for that fish.