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Keywords:

  • metabolic rate;
  • morphology;
  • body composition;
  • life span;
  • energy-density

A review of energy use and the life histories of deep-water demersal fishes suggests that there are two primary groups or guilds; those that live dispersed over the sea floor and those that aggregate in association with topographic features like seamounts. Dispersed deep-sea fishes typically have a body plan designed for slow cruising or ‘sit and wait’ predation, and are characterized by very low energy stores and metabolic rates. Scaled for body size, the metabolism of these fishes was comparable to that of bathypelagic fishes. On the other hand, aggregatory deep-water species are characterized by robust morphology and strong locomotory ability to maintain themselves in environments characterized by strong, variable currents. Their flesh has high protein and lipid but low water content. The metabolic rate of orange roughy, an aggregating deep-water species, was substantially higher than that of dispersed deep-water fishes and was comparable to that of haddock, a shelf demersal species. However, although the estimated ration of orange roughy was higher than that of dispersed demersal deep-water species, its growth rate was comparable and its growth efficiency was far lower due to its high metabolic costs. Large deep-water dispersed fish species are characterized by late maturity and an extended reproductive period, but these characteristics are less pronounced than in deep seamount-associated species, which may live in excess of 100 years.