Sockeye salmon are red, which is the usual color of females. Even small changes in wavelength, saturation, and brightness can affect preference. Both sexually naïve males and experienced males showed the same preferences, which illustrates that preference for a red hue may be innate. Some traits that lead to reproductive success, such as body size and sexual dimorphism can affect one’s survival. This leads to opposing pressures of natural selection and sexual selection. Larger males are favored, unless the risk of predation is very high. Sockeye salmon that die prematurely from predation are typically the larger ones in a population. This shows
Paradise fish less aggressive than the wild type, but also less hardy, having more trouble with low temperatures. Paradise fish The paradise fish, "'paradise-fish"', paradisefish, or paradise gourami ("Macropodus opercularis") is a species of gourami found in most types of fresh water in East Asia, ranging from the Korean Peninsula to northern Vietnam. This species can reach a standard length of , though most are only about . Paradise gouramis were one of the first ornamental fish available to western aquarium keepers, having been imported 1869 to France by the French aquarium fish importer Pierre Carbonnier in Paris. The paradise fish is