The most valuable catches in the deep sea are the larger individuals. The most common commercial deep-sea fish species and their main geographical provinces are listed here. In many deep-sea species, the most commercial are the older and most fecund members of the population. Fishing often targets these individuals, leading to significant alteration in population structure and reduced reproductive capacity.
An example of such modification was recorded within populations of the roundnose grenadier, Coryphaenoides rupestris. Fished commercially since 1965, catches climbed to a peak of 80 000 tonnes year-1 in 1971 and subsequently declined to 6 000 t y-1 in 1980. It is likely that peak catches removed a significant proportion of the spawning population and by 1980, the recruitment which should have occurred never did, causing the fishery to collapse. The longevity, slow growth and late maturation of many deep-sea fishes amplify the effects of removal, with potentially wide-ranging effects on deep-sea ecosystems, as observed in coastal fisheries. Currently, fishing is removing quantities of fish that exceed the rate of replacement. This has led to reductions in biomass and species richness of fish populations in the deep sea and other marine areas . Ultimately, deep-sea fishing in its current form may be unsustainable.