Environmental Engineering Reference
In-Depth Information
13.4 Economics of eradication and control
A cost:benefi t analysis should be part of any consideration to undertake control.
Where clearly defi ned economic costs accrue from persistence and spread of an
invasive fi sh and the costs of eradication or control can be accurately defi ned, then
the cost: benefi t analysis is quite simplistic. However, where impacts do not have
a direct monetary value, such as habitat modifi cation or biodiversity loss, then
the equation is considerably more diffi cult to compute. In an attempt to develop
an objective assessment of the costs and benefi ts of invasive species control where
economic costs may not be defi ned, Choquenot et al . (2004) argued for the appli-
cation of a bioeconomic model that can be applied either to benefi t maximiza-
tion or cost minimization. Such bioeconomic models could be considered in the
establishment of freshwater protected areas as proposed by Saunders et al . (2002).
Freshwater protected areas offer considerable promise given that freshwater catch-
ments may be protected from invasive species by natural biogeographic barriers.
13.5 Marine versus freshwater
By far the most signifi cant adverse impacts have been caused by the introduc-
tion and spread of freshwater fi shes rather than marine. Indeed, all of the eight
fi shes listed among the world's 100 most invasive organisms by the IUCN Invasive
Species Specialist Group are primarily freshwater (Lowe et al . 2000), although
both brown and rainbow trout are facultatively diadromous. Marine fi shes there-
fore represent perhaps the least problematic of the non-indigenous marine species
worldwide. Partly this refl ects a lack of incentive for the introduction of marine
species. Most countries have native marine fi shes that afford suitable opportunities
for sport or commercial harvest. Furthermore, the establishment of marine fi shes
is typically diffi cult given the number of individuals that would need to be released
to establish a viable population. Anadromous salmonid species are one exception
because juveniles can be raised in freshwater. Furthermore, many salmonids are
not obligately anadromous and establish self-sustaining populations in landlocked
waters. Despite this, efforts to establish self-sustaining anadromous salmonid
populations in some countries, involving the release of millions of juveniles from
hatcheries, has been time consuming and expensive.
13.6 Indigenous fi sh as invasive species
The redistribution of a country's indigenous fi sh fauna to areas outside their nat-
ural range can cause signifi cant damage to native fauna and ecosystems. The North
American freshwater fi sh fauna has undergone signifi cant homogenization due to
the introduction of a small number of cosmopolitan species for the enhancement of
food or sport fi sheries. Moreover, the primary cause of this homogenization is indi-
genous species introductions, rather than species extirpation. The most signifi cant
 
 
 
 
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