Raiding the Mesopelagic !

For as long as human beings have lived on the continents of the earth they have used the oceans as a source of food.  Each century more efficient fishing boats have ventured further out to sea and in recent years the fish taken have exceeded the ability of the remainder to rehabilitate.   We are fast decimating fish species to feed populations now numbering billions.

We only fish waters to a depth lit by the sun.  Below two hundred metres it is a dark world and for a long time we thought it was devoid of all life, until the invention of the bathyscope with it's lights and cameras revealed a world teeming with living creatures.  Its called the Mesopelagic and it is home to ten billion tonnes of animals, including finger sized fish with gaping maws and rows of needle sharp teeth, Dragonfish which illuminate prey with infra red spotlights unseen by their victims, and trillions of  sea squirts a few millimetres across which inflate gelatinous homes on their backs.   It is estimated that a mere one percent of this treasure would double the landed catch of all the world fishing boats.

Most of this would not appeal to the human palate, but just as we land creatures learned to farm to produce our food, now the bounty of the sea is undergoing a similar experience.  We are creating fish farms in the sheltered shallows.  Arrays of nets contain an area of water and it is stocked with fingerlings.  Their density exceeds the food supply - and they need ground nutriments to quickly grow to commercial size.   The fish farm industry is already eyeing the potential and Norway has issued 46 new licenses for vessels to fish there.   The industry now refers to the Mesopelagic as " the big apple "  !

The more we learn about the Mesopelagic the more critical it becomes.  It is possibly the worlds biggest carbon sump.  These trillions of small animals are in perpetual motion, rising and falling in depth as they rise to the surface to feed at night and return to the protection of darkness to hide them from their enemies as the light returns.  Nature is not wasteful.  Some die during each cycle and the waste they generate and those dead bodies fall to the bottom as what we call " ocean snow ".  It becomes a food source for a whole range of even more diminutive life forms.

This huge mass of living creatures captures an estimated twelve billion tonnes of carbon while it is at the near surface feeding and takes it back to a lower depth each year where it remains in storage.   We interrupt that cycle at our peril.  Unless this carbon is taken below the reach of natural sunlight it will disperse into the air above and accelerate global warming.

Fish farming seems to be a fast expanding nascent industry.  There will be a new source of income for the worlds fishing fleets, scooping up this unsightly marine product to be ground into a paste or a powder for the base product that is fast becoming the reliable food source of our fish supply.   We have a degree of control over what happens in our coastal waters, but the high seas are borderless and many nations ignore international control measures.   It is highly unlikely that any rationing measure to keep the quantity taken under control will be honoured.

We can estimate the annual fish harvest by what appears in the markets, but this new source of fishing wealth will be best taken during the hours of darkness, when it is near the surface and the end product will bear no resemblance to a product from the sea.  Unless we are very lucky, raiding the Mesopelagic may one day result in lifeless oceans !