Gasterosteus aculeatus, or the three-spined stickleback, is a fish native to most inland coastal waters north of 30 N. However, as they are anadromous they can also be found in freshwater during breeding times. The three-spined stickleback has long been a subject of scientific study for many reasons. It shows great morphological variation throughout its range, which is ideal for questions about evolution and population genetics. Sticklebacks have four color photoreceptor cells in their retina making them tetrachromatic (RGB + UV). The three-spined stickleback has recently become an important organism for research that looks into the genetic changes involved in adapting to new environments.

The genome of a female fish from Bear Paw Lake in Alaska was sequenced by the Broad Institute, using whole-genome shotgun sequencing with a base coverage of approximately 11x. The stickleback genome contains approximately 460 Mb and comprises 22 pairs of chromosomes. The current assembly includes 1,822 unplaced super-contigs, and is predicted to contain 20,787 protein-coding genes.