permaculture

[Jack Rowe <jackrowe@compuserve.com>]

>Jack Rowe wrote:

> In Asia, fish ponds receive much of their necessary phosphorous 
>and calcium from animal, human and bird manures, with 
>animal pens and even latrines placed where effluents reach 
>the shallow, low-trophic (phyto- and zoo-plankton producing) 
>areas of fish ponds. 

>>Lloyd Prentice wrote:

>>I have read that some of these systems are implicated in the 
>>evolution of influenza viruses. Anybody know more?

I suspect, without knowing many specifics, that your point raises a valid
health concern, Lloyd. In fact, influenza might be only one of the
possibilities arising from careless handling of fish raised in direct
contact with human and animal manures. E. coli, cholera, salmonella, etc.
come to mind... thorough cooking would be a necessity in these situations,
as it is with chicken 'manufactured' in the US.

One of my two major points was the desirability of careful use/reuse of all
'waste' products -- which can be seen as either resources or pollution.
When we treat manure as pollution, we pay to have it 'removed' (to where?).
Wastes treated as pollution tend to accumulate and, in fact, begin to act
as pollutants. When we call a waste a resource, we are often able to find
productive uses. The material may be the same in either case, but our
perception by itself can change that material from a liability to a
valuable resource -- or vice versa.

The other point is that, each time we move a step up the trophic/food
ladder, a great deal of energy is used. Food-to-meat conversion factors
tend to be 20% at the best and are usually much lower (fish are very
efficeint at food conversion, happily). We will always get the biggest
'bang for our buck' if we feed at the lowest point on the trophic ladder
that we can. In general terms, feeding high-protein food to catfish (which
are scavengers), for instance, is for this reason not 'economical' when
viewed in holistic or ecological terms. Intensive feeding in aquaculture or
agriculture raises production dramatically, but it does not necessarily
raise cost-effectiveness of an overall operation due to the law of
diminishing returns (land and materials costs, of course, force production
to reach toward the highest compromise between intensive production and
least input, fueling some degree of energetic inefficiency in return for
financial viability).

Feeding at the lowest trophic level is why ponds are most-economically
fertilized with calcium and phosphorous... these are critical elements in
the production of phytoplanktons and zooplanktons, which form the base of
the food 'pyramid' in aquatic systems (economically important herbivorous
fish being fairly uncommon -- unless we call phytoplankton eaters
herbivores). Manures are rich in phosphorous, and often rich in calcium. A
great deal of production can come from feeding manures to the planktons,
whereas few of the animals higher on the trophic ladder will eat manure to
advantage (a valid fact pointed toward by Lloyd). Manures are ubiquitous
and generally more common than natural sources of high-analysis nutritive
minerals.

However, manures are an energetic step up from minerals and are also rich
in nitrogen, which is almost never a limiting factor in fish production and
is often a harmful pollutant causing turbidity and lowering of dissolved
oxygen levels. Perhaps manures are best 'composting' during biogas
(methane) production and then used as fertilizers in terrestrial
applications. Conventional sewage treatment produces biogas... the
difference is that the methane is seen as pollution an is not captured for
use (an electrical generation plant in Stanton, CA uses human sewage to
produce the gas which fires its generators). Manures can in fact be
safely-recylced in a number of ways which use their nutritive value to
postive effect instead of purposely dissipating it at considerable expense.


Producing our needs at the lowest economic, energetic and ecological costs
is the critical next step in aquacultural and agricultural systems (as in
other systems). We'll continue to learn more efficient ways of, as Paula
put it, "...raising fish and plants in a synergistic system... to produce
products we could consume and sell as "safe", while using a more natural
method of fertilization...". In the process, we'll have to explore many
ideas and look at our energy and materials cycles in a new light.
Eventually we will come up with ways to produce our needs without relying
on fossil fuels to power the necessary cycles, and without creating
pollution from materials which could be used productively instead. As one
definition of sustainability puts it, "Sustainability is meeting our needs
without endangering the ability of future generations to meet THEIR needs".
A worthy goal we're all in agreement with. 

Jack Rowe