Nearly 0.3% of solar energy incident on the sea surface is fixed by phytoplankton the tiny plant organisms suspended in natural waters, over the 40-60 meters of the upper water column, accounts to 75% of primary productivity of an area of the word oceans near to 3.51014 square meters; the remaining 25% is produced by macro algae. The amount of biomass of all the consumers is based upon primary production by phytoplankton, which range between 0.05 — 0.5 gCm-2d-1, but in some very productive upwelling zones or in some grass beds, it can be as high as 5 gCm-2d-1 (Russell-Hunter 1970; Margalef 1974; Cushing and Walsh 1976). As a result of this photosynthetic process, the carbon gross production of the sea amounts to 15.5 x 1010 mt of Carbon per year, equivalent to a net production of 1.5 x 1010 mt, most of it in shore waters. By having in mind the energetic efficiency, these figures amount to 8 per cent of global aquatic primary production (Pauly and Christensen 1995; Friedland et al. 2012), meaning that there is a maximum limit to fisheries production.

Biological production through the fixation of light is a process interacting with the degradation or dissipation of energy by all organisms; in other words, the persistence of life as we know it, depends on a permanent input of energy, which after being fixed and transformed in chemical energy by the plants, is dissipated constantly by all organisms on Earth. Human beings have been able to simplify the food webs channelizing the production

of a few species which are exploited by man; agriculture systems are a typical example of this process. However, this implies a limit to the maximum potential production of biomass by organisms (Pauly and Christensen 1995; Friedland et al. 2012; Botsford 2012).