Fishery

Oceanography

The ocean is not a uniform body of water. The physical and chemical properties of the ocean vary greatly from one huge water mass to another.

Furthermore, these deep water masses are not static but move around. There are two major mechanisms which drive these flows:
  • wind stress (the force exerted by the wind on the surface), and
  • thermohaline circulation (density differences due to temperature and salinity variations).
These ocean current flows are measured in large units called Sverdrups. One Sverdrup is 1 million cubic metres of water per second moving past a given line.

The flow of the Amazon is about half a Sverdrup and the combined flow of all the rivers in the world is about one Sverdrup.

Continental boundary currents like the East Australian Current are typically about 5 Sverdrup. The biggest flow in the world is between the southern tip of South America and Antarctica and is 500 Sverdrup.

The ocean is also divided vertically. Unlike the deep ocean, the top layer of the ocean is well mixed, by the wind. The bottom boundary of this "mixed layer" is called the "thermocline", about 50 m deep.

The depth of the thermocline varies from place to place, a trade-off between the tendency to mix due to wind stress and the tendency to stratify due to solar heating.

The mixed layer roughly coincides with the "euphotic zone", the region in which there is enough light for photosynthesis to take place.

For most of the ocean the mixed layer is rather sterile. The water in satellite images is blue, not green, because very little photosynthesis is happening. There are two notable exceptions, where marine ecosystems bloom:
  • Around the margins of continents where river runoff brings nutrients from the land, and
  • At "upwellings", where cold nutrient-rich water is brought into the mixed layer by the action of deep ocean currents.
The purpose of the Nutrient Megapump project is to create artificial upwellings so as to enrich the ocean by bringing nutrients into the euphotic zone in the same way as natural upwellings.

Half of the world’s wild ocean fish depend on natural upwellings occupying only 0.1% of the world’s ocean surface (WR01, WR02).

So we might expect to double the world’s supply of wild fish if we were to triple upwelling flow by adding an extra 0.2% of Nutrient Megapump upwelling area. Oceanic carbon sequestration and export would also be enhanced, as explained in the following section.

This is necessary because world fisheries have greatly declined, catch effort greatly increased. Hence tripling of fish prices at Tokyo's Tsukiji fish market from 2007 to 2010.

Oceanic carbon sequestration and export enhancements would be of higher quality than in continental systems such as plantations. They would be of longer duration, have lower social and environmental impacts, take pressure off many practices, traditional land use and so on.

The approximate dollar value of man-made nutrient flows can be estimated by placing a dollar value on
  • Carbon sequestration and Carbon export,
  • Sustained production tonnages of well-managed pristine, wild fisheries based on natural upwellings. Fortuneately there have been two outstanding examples:

The Namibian Upwelling

The best example is the Benguela upwelling off the coast of Namibia. It was one of the last to be exploited, mid-1960s to 1988, was relatively well managed and recorded by FAO. The flow of this upwelling is approximately 2 Sverdrups, i.e. 2 million tons of deep ocean water comes to the surface every second (Skogen, 2004).

Russians and others, mostly Europeans, took approximately 20 million tons of fish out of the Namibian upwelling during the ~20 year period 1968-88, i.e. at a rate of about 500 kilotons per year per Sverdrup, see "Exploitation, Profile of Catches" (WR04).

If this rate exceeded the fisheries' Maximum Sustainable Yield (MSY) it would not have been by very much, because it went on for over 20 years at a fairly even rate without any catastrophic decline of any catch species’ population (WR05).


The Peruvian Upwelling

One of the world's major upwellings occurs off the coast of Peru and supports a major fishery there. This upwelling of about 15 Sverdrups (WR06), produced approximately 20 million tons of anchovy per annum during non-El Nino years, of which up to 13 million tons pa were taken (WR07 and Idyll, 1973).

Catches of a type of anchovy called anchovetta were above 10 million tons in the late 1960s to 1971 off northern and central Peru. The Peruvian anchovetta population was heavily fished and collapsed during the warming of the 1972 El Niño (WR08). FAO and others worked out an MSY of 10 Megatons per annum for this fishery (WR09 and WR10). Laws (1999) offers a good printed history.

The MSY of the Peru upwelling was thus about 666 kiloton per annum per Sverdrup. This high Peruvian anchovy MSY rate corroborates our 500 kiloton per annum per Sverdrup approximate MSY rate for the wider range of species taken from the Namibian upwelling.

These two fisheries were amongst the last fisheries in the world to be exploited and were near-pristine when those measurements were made. They may have been the world’s only well studied near-pristine fisheries. They are both "Eastern Boundary Current" upwellings.


Dollar Value of Fishery Based on Natural Upwellings

We propose using overall dollar/ton rates from the most upmarket contemporary wholesale fish market, Tokyo's Tsukiji. It is processing over 700,000 tons of fish per year in 2010 for an annual turnover of more than 6 billion dollars (WR11).

The average wholesale price of fish at the world's major fish market is thus $8,572 per ton, more than 3 times the 2007 value. Fish handling costs would not have increased nearly so much, so these would now be a minor fraction of the increased income, much of which would be going into increasing catch effort.

Increased catch effort, more trips and so on, only worsens decline of world ocean fisheries. Our Nutrient Megapump has the opposite effect of reversing decline. We thus propose it as a better way to spend increased income from wild fish sales.

The Namibian catch rate figure of 500,000 tons of fish per year per Sverdrup and the Tokyo average wholesale price of $8,572 per ton give an upwelling value of $4.3 billion per year per Sverdrup.

Now using the estimated yield of a 1 GW hydrothermal bubble pump of 1.7 x 10^-2 Sverdrup. Multiplying $4.3 x 10^9 by 1.7 x 10^-2 gives $8.0 x 10^7 per year.


Conclusion

The annual return in fisheries product from a single 1 GW hydrothermal bubble pump is thus estimated to be $80,000,000. Carbon Credits of possibly greater value would be a further income.

As explained under our VEC Checklist Answers to Questions 37 to 40 (Link on Homepage), the estimated $300 million cost of a 1 Gigawatt Nutrient Megapump could be paid for by the value of such enhanced wild ocean fisheries alone, using 2007 Tsukiji fish values (WR12).

As explained above, this 1/3 of 2010 income represents a surplus value invested at present on increasing catch effort which we argue is better spent on our Nutrient Megapump.

Carbon Credit income is also assured. Carbon Credit values are also increasing as ocean acidification due to CO2 increasingly threatens marine ecosystems.

The HydroThermal Vent (HTV) water natural resource powering the Nutrient Megapump is neither precious nor polluting, unlike the oil of the oceaneering used for our $300 million costing, which is therefore conservative.

Hence apparent profitability of a 1GW Nutrient Megapump. More powerful Megapumps would have greater economies of scale.

The largest HTV found to date is the TAG HTV of 1.7 GW. Only 10% of HTV field regions (MORs) have been explored.



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