The thermodynamics of the biomass flow and secondary production indicates that the transfer efficiency of carbon in the sea webs may approach to 15 per cent; however, many other authors (in Christensen and Pauly 1993; Pauly and Christensen 1995) adopted the value of 10 per cent. All of the consumers depend from the chemical energy to subsist; this energy is synthesized by the primary producers and transferred to other trophic levels trough consumption by herbivores and then passed to several levels of animals through predation.

Zooplankton, the free-living animals suspended at the water column, are the kind or organisms which make use of the primary production. The main component of this food webs is the group of copepods. Apart o being composed mostly by herbivores, zooplankton also contains many predators of first order, like jelly fish and other crustaceans as larval stages of benthic organisms spending in most cases, from a few days to several months suspended in the water column as predators of micro zooplankton, then being recruited to the benthic communities as they grow.

Caloric value of organisms indicates very uniform qualities through the food web, being higher in those animals storing lipids in their bodies. In sugars and proteins, the caloric value is 4,100 cal g-1, whilst in lipids this value amounts to 9,300 cal g-1, but when these substances are not totally oxidized, the calories available are nearly 90% of their total caloric values. A high production of biomass from the primary producers would be uptaken by the herbivores and transferred to upper levels of the food web. This means that a high primary production will imply high biomass of consumers in proportion following the rule of 10 per cent; this is, for each ton of top predators, there will be 10 mt of predators of first order, and 100 mt of herbivores. The biomass of the carnivores ranges between 0.5 and 2 g C m-2 and follows the 10% rule respecting to the lower level. The biomass of primary producers, mainly phytoplankton, may be lower than the herbivores because of their high turnover rate. It is pertinent to mention that upwelling zones of the sea, like in Peru on the west coast of America and West Africa, significant amounts of nutrients are flowing up from the deep sea enriching the surface waters in the photic zone and stimulating the primary productivity. In these zones, the process of evolution has allowed the organization of short food chains, where the sardine and anchovies take advantage exploiting much of this production, allowing the growth of large schools which are exploited by human beings, with levels of exploitation of more than 12 Million mt, as occurred in Peru in the early seventies.

2. The fisheries infrequent, to become abundant and reducing the biodiversity; this seems to be the case of squids and jellyfishes. This process determines an increase of the primary production/biomass ratio in the ecosystem. The most productive ecosystems are those associated to upwelling, where the fast growing predators with short life spans, plankton feeders determining the existence of short food chains, allow the existence of very productive fisheries as in the case of anchovy and sardine fisheries. In other natural communities, where the ecosystem usually imposes high environmental stability, top predators usually are animals with long life span in relatively long food chains; in this case, the potential biomass production is low, because the evolutionary forces are oriented towards the density dependent processes, leading to the organization of ecosystems with high biodiversity as occurs in coral reefs. In this kind of communities, the surplus production is almost nule, because the production/consumption ratio approaches zero, severely reducing the capacity of commercial exploitation.