Polygamous is a mating system in which an individual of one sex has multiple partners during the breeding system but individuals of the opposite sex have only one partner. Evolutionarily, these systems are purported to have an increased chance of passing on “good genes” from individuals that compete for the ability to mate with multiple partners. This mating system can occur with one male and many females (see polygyny) or one female and multiple males (see polyandry).
Promiscuous is a mating system where both sexes have multiple partners during the breeding system. In fishes, this is the most common mating system. Breeders make
little or no mate choice and spawn with multiple partners, either sequentially or at the same time.
Breeding aggregations of promiscuous spawners can make some fish species particularly vulnerable to fishing. The fish generally assemble according to environmental cues (e.g., temperature, moon phase) that are known to fishermen. Overfishing on spawning aggregations can be particularly devastating to fish populations because the high fecundity (fertility) individuals are readily removed from the population. The Nassau grouper (Epinephelus
striatus), for example, once supported an important Caribbean fishery but is currently endangered because of overfishing on these spawning aggregations.
Polygyny is a polygamous mating system where a male has multiple female partners during the breeding season. This is the more common form of polygamy.
Polygynous males, like slimy sculpins (Cottus cognatus), setup territories and are visited by multiple females. Other polygynous males, like some African cichlids (such as Mchenga eucinostomus), form leks, where they congregate and perform breeding displays to attract female passers-by. And still other polygynous males, like wrasses (Labridae), form harems where a large male protects a number of females with which he, alone, can mate. See polygamous;