Environmental Engineering Reference
In-Depth Information
research and development, these techniques will provide rapid and cost-effective
tools for a suite of marine pest species in ballast water and environmental samples.
Hull fouling management
Vessel hull fouling ranks alongside ballast water discharge as a primary pathway
for the spread of AIS worldwide; however, practical management solutions to
address this problem remain elusive. Antifouling coatings are effective at pre-
venting growth on vessels hulls, but effi cacy is limited on vessels that are fre-
quently idle or subject to poor maintenance regimes (Floerl et al . 2005a). When
fouling occurs, vessels are often removed to land for cleaning (dry-docking) or,
perhaps more commonly, have their hulls cleaned in-water (in the case of small
craft or large vessels outside their dry-docking schedule). Many concerns exist
regarding conventional in-water cleaning (e.g. mechanical removal using brushes
and scrapers). Entire organisms and/or viable fragments (e.g. colonial organisms
or algae) may survive and establish, or the physical disturbance associated with
removal may trigger the release of viable gametes and propagules (ANZECC
1996). Several methods are currently under development to reduce biosecurity
risks posed by in-water hull cleaning. Trials have begun on diver-operated rotat-
ing brush systems, which incorporate suction and collection capabilities, that
are able to remove and reclaim ~90% of fouling material from vessels hulls in
situ (Hopkins and Forrest 2008). Encapsulation techniques are also being devel-
oped, whereby vessel hulls are wrapped in plastic in situ in order to eliminate
fouling organisms through the creation of anoxic conditions (Coutts and Forrest
2005; Denny 2007). Mortality can be further accelerated through the addition of
chemical agents to the encapsulated water (Coutts and Forrest 2005).
Pest detection and response
A relatively new strategy for the control of invasive species in aquatic environ-
ments involves the use of semiochemicals. Semiochemical is a generic term for
chemical substance that carries a message (e.g. pheromones, allomones, kairo-
mones). Semiochemicals such as pheromones are responsible for eliciting strong
behavioural responses (e.g. settlement, gamete formation and reproduction)
across a range of marine organisms including polychaetes, decapods, and ech-
inoderms (Bartels-Hardege et al . 1996; Hamel and Mercier 1996; Ingvarsdóttir
et al . 2002; Watson et al . 2003). The role of semiochemicals in host location by
salmonid parasitic sea lice Lepeoptheirus salmonis were investigated as a control
tool for infestations in aquaculture stocks (Ingvarsdóttir et al . 2002). Isolated
chemicals from salmon-conditioned water was shown to be signifi cantly attractive
to sea lice in a slow-release system, and it is hoped these may form the basis for in
situ lures for the control of sea lice in the fi eld. Similar techniques, in combination
with other control measures such as trapping, may prove useful for the control of
other pest species such as crabs and sea stars (Sutton and Hewitt 2004). Further,
compounds such as sex pheromones have also been suggested as manipulating
chemicals for controlling the life history events of marine pest species such as
A . amurensis (McEnnulty et al . 2001).
 
Search WWH ::




Custom Search