Biology Reference
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the fouling organisms on cages, their gonads being offered to seafood gourmets
(Cross 2010 ; Cook and Kelly 2007 ). In the case of an abalone farm in South Africa,
the resulting seaweed crop of Ulva lactuca can partly be used for feeding the
abalone (Nobre et al. 2010 ; Robertson-Andersson et al. 2008 ). Since it is known
that Ulva synthesizes more protein (
40% dw 1 ) with higher ammonia-N in the
water, it turns out to be a valuable feed allowing Haliotis to grow significantly faster
than with Ulva kept in low nitrogen concentrations and containing only 12% protein
(Shpigel et al. 1999 ).
While Ulva spp. with their thin thalli and large surface-to-volume ratio are
perfect inorganic extractors their biomass does not realize a high price. Therefore,
commercially valuable red algae like Porphyra (nori), Gracilaria (as an
agarophyte), and Kappaphycus (as a carrageenophyte) are being tested in IMTA
systems (Chopin et al. 1999 ; Abreu et al. 2009 , 2011 ; McVey et al. 2002 ; Pereira
and Yarish 2010 ; Rawson et al. 2002 ; Robertson-Andersson et al. 2008 ; Lombardi
et al. 2006 ). Depending on the region, particularly those with pronounced seasons,
seaweeds in IMTAs may have to be exchanged for other species in the course of the
year, which requires additional engineering efforts to suit each species'
requirements. There are for example different demands of red algae versus brown
kelps concerning surface area, water flow rates, and nutrient exchange, etc.
Owners of profitable finfish or shrimp cultures are not necessarily concerned
about eutrophication of the environment and have to be convinced that no diseases
are introduced by co-cultured organisms (Troell et al. 2003 ). It needs the owners'
consent to use existing fish or shrimp cultures to establish an IMTA system: In open
sea, but nearshore systems, different components of an IMTA can simply be placed
in each other's vicinity with mutual beneficial effects provided local currents and
other water dynamics allow sufficient exchange between them (Abreu et al. 2009 ;
Sanderson 2009 ; McVey et al. 2002 ; Chopin et al. 2001 ; Troell et al. 1999 ; Petrell
and Alie 1996 ). The alternatives are land-based tank systems or ponds that can be
separated from sea water inflow at periods of toxic algal blooms or oil spills, etc. In
these systems, fish farm effluents are redirected through a series of tanks containing
complementing organisms. The Sea Or Marine Enterprises in Israel integrated
gilthead seabream with Ulva or Gracilaria , with the algae serving as a feed for
commercially valuable abalone (Neori et al. 2004 ). With abalone ( Haliotis midae )
and seaweeds alone, a partial recirculation of the culturing water is feasible
(Robertson-Andersson et al. 2008 ).
To establish a managed small ecosystem, that is adapted to site and region and
that in addition sustains stakeholders and environment, is a very complex task,
impossible to be tackled by individual farmers. Therefore, Canada has launched
a new network CIMTAN ( 2011 ). CIMTAN is directed to collect additional knowl-
edge and intensify interdisciplinary as well as multi-institutional information
exchange between the experts on aquaculture on both coasts of Canada. Research
and development of IMTAs has been conducted in Canada since 2001. The joint
goal is to establish an easily adaptable system of IMTA with a set of nutritionally
interacting species that mimics the natural condition of a diverse ecosystem,
thereby being less vulnerable to e.g., microbial infections or parasite infestation.
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