Environmental Engineering Reference
In-Depth Information
quantities of the piscicide of choice. Annual worldwide supply of natural piscicides
like rotenone is limited by its availability involving the harvest of source crops.
The Strawberry Reservoir rotenone application (20.6 t) in Utah, USA, in 1990
was estimated to consume roughly one-third of worldwide rotenone production
in that year and roughly four times the typical annual fi sheries usage in the USA
(McClay 2000). However, the recent decision by the European Union (EU) to ban
rotenone use in plant protection products (EU 2008) is likely to increase its avail-
ability for alternate uses, especially if other countries follow the European decision
in an attempt to reduce agricultural pesticide use and insecticide resistance. A var-
iety of piscicides have been used to remove pest fi sh in order to enhance or recover
the biodiversity values of a water body, to reduce or eliminate fi sh biomass in fi sh
and non-fi sh aquaculture ponds, or to reduce pest fi sh impacts in larger freshwater
systems.
Four chemicals (rotenone, antimycin, saponins, 3-trifl uoromethyl-4-
nitrophenol) have been extensively used for such purposes but at least 40 sub-
stances have been used on a more limited scale (Lennon
et al
. 1971) or investigated
as potential piscicides (Clearwater
et al
. 2008). h e key requirement for such
chemicals is that they show strong selectivity towards fi sh but limited toxicity to
other sectors of the biota in order to limit collateral ecosystem harm. In developed
nations with robust legislation controlling the environmental use and application
of toxic substances, pesticides typically must undergo a rigorous set of risk assess-
ment procedures to qualify for registration, and then only for specifi ed use or activ-
ity. In other circumstances, certain pure compounds or chemical mixtures may be
authorized for piscicidal applications but may require specifi c, experimental, one-
off , legislative approval by a local authorizing authority. h is is usually described
as 'off label' usage. National pesticide registration therefore sometimes alleviates
the requirement for a protracted environmental impact assessment for each appli-
cation. Formulations of fi sh control chemicals may vary depending on the tar-
get species or target environment (shallow versus deep lakes, static versus fl owing
water) and specifi c products or formulations are usually registered with national
pesticide registration authorities. Rotenone is currently registered in several coun-
tries although allowed formulations may vary. For instance, powdered rotenone
has recently been assessed by the Environmental Risk Management Authority and
subsequently registered by the Agricultural and Veterinary Medicines Authority
in New Zealand for piscicidal use but liquid formulations and rotenone carp baits
have not. In the USA, antimycin, niclosamide, and 3-trifl uoromethyl-4-nitro-
phenol (TFM) are also registered for use in controlling noxious fi sh. Numerous
authors report problems with the dependability of supply of some fi sh control
chemicals and the consistency of the products.
An important consideration in treating both static and fl owing waters is to max-
imally dewater the system. h is reduces the surface area for treatment and the
volume of water to be treated, thus reducing the quantity of chemical required. It
also dewaters structurally complex littoral habitats such as reed beds, root masses,
undercut banks, and rocky shorelines that may be di cult to treat and which
