Biology Reference
In-Depth Information
22.1.3.2
Integrated Multi-Trophic Aquaculture (IMTA)
Extensive polyculture pond systems with organisms of several species in the same
water body have traditionally been applied in Asian countries and were based on
trial and error. Only since the 1970s, a more systematic approach has resulted in the
development of integrated intensive land-based mariculture systems (Ryther et al.
1979
). The aim of IMTA is the creation of a manageable small ecosystem with
several species of different trophic levels combined in one system in the right
proportions, each utilizing waste products or the biomass generated by another
member of the system. All of the individual components must be marketable since
the commercial viability is an important factor of any such IMTA design (Chopin
et al.
2008
). If the benefits for the environment were accounted for, the value of
IMTA production systems would be highly increased and political support for the
development of these structures would mirror this.
Neori et al. (
2004
,
2007
) argued that seaweed-based integrated aquaculture
systems will most probably facilitate the expansion and sustainability of the
worldwide aquaculture industry. Nevertheless, the major aim of global aquaculture
enterprises is the production of fish, shrimp, or shellfish protein. With the dwindling
of wild resources through overfishing there is an ever growing demand for those
products. At the same time the demand for certain seaweeds for human consump-
tion or animal feed or else for algal ingredients (mainly phycocolloids) has to be
met and is already a large market, worth 22.4 billion US$ in the year 2008
(FAO
2010b
).
Since the culture of fed species like fish or shrimp inevitably results in eutrophi-
cation of the adjacent waters (Stead and Laird
2002
; Fei
2004
; Sanderson et al.
2006
; Troell et al.
1999
,
2003
), a bioremedial complementary culture design makes
sense for environmentally protective reasons. Simultaneously the biomass of care-
fully chosen extractive and marketable species could at least partly counterbalance
the considerable costs for fish or shrimp feed (Neori et al.
2004
; Abreu et al.
2009
).
Moreover, there are oligotrophic seawater conditions, like in Israel or Australia,
that do not allow the growth of algae and it makes sense to try intelligent new
aquaculture approaches under these circumstances (Schuenhoff et al.
2003
;
Butterworth
2010
; Neori et al.
2004
).
An encompassing review of the multiple IMTA activities is found in Barrington
et al. (
2009
) for temperate and Troell (
2009
) for tropical regions of the world.
Potential candidates for integrated systems are not only the hitherto monocultured
and expensively fed fish and crustaceans, filter-feeding bivalve or herbivore
mollusks (
Haliotis
), and more than 20 species of seaweeds but also echinoderms
and polychaetes. Presently existing IMTA systems usually contain no more than
three components at different trophic levels. One is fed fish or shrimp, one
extracting organic bound nutrient particles, either feed leftovers or feces, and one,
seaweeds, extracting the effluents utilizing inorganic nitrogen and phosphate for
growth. In a Sustainable Ecological Aquaculture effort Cascadia SEAfood even
integrates sablefish with two species of bivalves, kelp, and sea urchins that feed on
