# Lessons for Coastal Applications of IMTA as a Way towards Sustainable Development: A Review
## 5 Economic Value and Financial Viability of Coastal IMTA  
### Species-Specific IMTA  
Sea cucumber (_Cucumaria frondosa_) aquaculture has grown in popularity in a context of rising demand and declining wild fisheries, aided by technological advance in the production of sea cucumbers [96; 97]. As detritus feeders that consume organic matter in the sediment, and as key surface sediment processors, sea cucumbers are interesting for IMTA [88; 91]. Various species have shown potential when cultivated in the water column underneath fish cages [88], in cages with sea urchins [98], in abalone tanks [99], and in hanging scallop lantern nets [36]. The integration of sea cucumbers into existing aquaculture facilities could deliver significant economic and environmental benefits if appropriate culture methods are taken and if the sustainable development of the industry is supported by supporting legislative frameworks [100]. A number of studies indicate that when cultivated with salmon, shellfish (e.g., oysters and mussels) show significantly increased growth rates [86; 101; 102]. Regulatory services from bivalves in IMTA are also considerable [103]. If current trends continue [24], opportunities for developing novel IMTA configurations with a central role for bivalves are likely to be developed in China. Seaweed has a big market as food, phycocolloids, feed supplements, agrichemicals, nutraceuticals, and pharmaceuticals, with a value of USD 6.4B from sales of nearly 23.8 million tons in 2012 alone [104; 105]. Diversifying the culture system and implementing fish/shrimp in combination with extractive algae implies not only ecological but economic gains [21]. In 2013, China consumed 193,705 tons of its domestic sea cucumber production, while only a few hundred tons were exported. _A. japonicus_ is a highly valued species in certain parts of Asia that is traded worldwide. Using a mass balance framework [106], it was found that a ton of salmon produces about 50 kg of nitrogen, which is released into the environment in the salmon production cycle, providing nutrients for ten tons of seaweed or five tons of mussels [107]. If we define productivity not in terms of per unit of feed (biotic depletion), but in terms of per unit of fish meal or fish oil from wild fish stocks, the recycling of otherwise wasted nitrogen into the marine proteins and lipids needed to feed fish offers opportunities to increase productivity in a way that may be economically meaningful to the farmer. Such reintegration of nitrogen into fish feed offers opportunities to increase productivity [19]. The 10 tons of algae produced per ton of fish can generate 164 kg of protein and 9 kg of marine lipids [108], and these components could be recycled as fish feed [19]. While this reduces the impact of aquaculture on the environment, it also offers so far underexplored potential for increasing the economic viability of aquaculture enterprises [19]. Using a discounted cash flow method financial returns were projected for: (i) conventional Atlantic salmon monoculture; (ii) Atlantic salmon IMTA with _Mytilius edulis_ (blue mussel) and IMTA with _Saccharina latissimi_ (kelp); and (iii) blue mussel, kelp, Atlantic salmon, and green sea urchin (_Strongylocentrotus droebachiensis_) as a benthic component below the net pens. The three-species IMTA was found to be significantly more profitable than the Atlantic salmon monoculture and the four-species IMTA. The four-species IMTA produced lower NPV than salmon monoculture, unless IMTA salmon and mussels were priced 10% higher. When a 10% price premium for IMTA salmon and mussels was included, both the three- and four-species generated a significantly higher NPV than salmon monoculture [37; 109]. Given that the studies below indicate that price premiums on IMTA products have a bright future, it is plausible to regard the NPV projections with a 10% price premium as more reliable.