Untitled - About the Philippines

Managing aquaculture and its impacts: a guidebook for local governments
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Biological impacts of aquaculture may
include fecal discharge of fish, waste food,
and impacts on genetics and biodiversity.
Aquaculture, like many other human
activities, produces wastes which, if not
managed properly, may negatively affect
the environment. In intensive aquaculture,
increased deposition of organic wastes such
as uneaten food, faeces, and excreta increases
biochemical oxygen demand, nitrates and
phosphates in receiving waters. This may not
necessarily be a problem as natural breakdown
processes or dilution in the receiving waters
can assimilate this, provided that natural
waters are not overloaded. Aquaculture
potentially has several adverse effects on wild
species, including disease transmission, escape,
and capture for broodstock or rearing among
others. Reliance on high protein, fishmealbased
feed for carnivorous species often
requires many pounds of wild fish to produce
one pound of edible aquaculture product.
While the transmission of disease from farmed
to wild stocks is still uncertain, the contagion
from one farm to another is a serious risk.
Box 2. What bad aquaculture practices
result to negative impacts on the
environment?
• Poor siting which may include
conversion of sensitive habitats,
setting up of structures such as
seaweed floats in coral reef areas,
and ponds which require too much
pumping of groundwater. The lack of
appropriate planning and zoning is a
main reason for poor site selection.
• Overcapacity. Refers to the
establishment of structures such as
cages and pens beyond the carrying
capacity of the lake, river, or coastal
area. Too many pens that obstruct
the free flow of water and physical
congestion are tell-tale signs of
overcapacity.
• Overstocking. Similar to
overcapacity but limited to the
confines of a cage or pen or pond
unit. Means that the number of
fish (fry or fingerlings) stocked is
beyond the recommended number.
Overstocking ultimately results to
higher demand for feed, higher
wastage, and increased demand
for oxygen and nutrients from the
water.
Chemical impacts include oxygen • Overfeeding. Either too much
depletion and eutrophication which are caused feed or use of inefficient feeds with
by the production of nutrient-loaded effluents, low-quality binders, i.e., the feed
crumbles and settles to the bottom
presence of antifoulants used in boats and before it is eaten. Usually done to
nets, industrial wastes and medications and
treatments for fish, shellfish, and seaweeds
hasten growth of fish and result in
bigger sizes.
(although minimal chemical used for seaweed
culture) which can harm wildlife and the
environment, and may lead to antibiotic resistance.
Physical impacts range from the aesthetics (poor zoning and proliferation of cages
and pens can be eyesores), to net friction causing poor water exchange, and to the
extremes of altering critical habitats such as wetlands and mangroves. A particularly
serious type of impact due to detritus from fish farms has been identified by Heinig
(2000) to be the presence of lost or discarded nets on the bottom. These nets can
have some potentially beneficial effects, such as providing refugia for mussels and
other benthic epifauna, but in general their presence should be viewed as a negative
impact since once they become buried in the bottom sediments they are almost
impossible to find and remove, and they can interfere with alternate uses of the area
if fish farming is discontinued. The conflict over the use and conversion of natural
resources as well as access to remaining resources and the privatization of public
commons has resulted in serious conflicts and questions pertaining to equitable use
of resources. Massive water use can result in water shortages as well as salt water
intrusion and other hydrological changes or waste disposal issues. The allocation of
space, especially coastal waters, highlights the user conflicts especially aquaculture