Cost-effective IMTA: a comparison of the production efficiencies of mussels and seaweed

Abstract

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Going beyond the search for solutions: understanding trade-offs in European integrated multi-trophic aquaculture development

“…In terms of sequestering 10% (as a nominal value) of the nitrogen from a 1000 t salmon farm, this would require approximately 10 to 13 ha of seaweed cultivation. These values are roughly in line with lower estimates for the space required to sequester 10% of the dissolved nitrogen from Danish fish farms (Holdt & Edwards 2014). Using these values and Bostock et al's (2010) estimates of space required for salmon production, 1 ha of salmon production would require between 17 and 23 ha of seaweed to sequester 10% of the nitrogen output.…”

“…Using these values and Bostock et al's (2010) estimates of space required for salmon production, 1 ha of salmon production would require between 17 and 23 ha of seaweed to sequester 10% of the nitrogen output. However, in their study, Holdt & Edwards (2014) argue that mussel cultivation is approximately 220% more efficient than seaweed cultivation per unit area (Holdt & Edwards 2014).…”

“…This increase in productivity happens firstly because there is an increase in production from the lower trophic species that are grown alongside the fin-fish and secondly because there is good evidence to suggest that these lower trophic species are able to utilise the nutrient from the fin-fish and are more productive when grown alongside fed aquaculture (Lander et al 2012, Sanderson et al 2012, Irisarri et al 2015, although this experience has not been universal (Cheshuk et al 2003), indicating that the integration may require some tuning. Using a mass balance approach, the production of 1 tonne (t) of salmon releases approximately 50 kg of nitrogen into the environment (Wang et al 2012), which could support the growth of 10 t of seaweed or 5 t of mussels over the course of the production cycle of the salmon (Holdt & Edwards 2014). In the case of seaweed, this equates to a 1000% increase in biomass (wet weight relative to the fish pro-duction) produced and an increase in protein production by 166% (based on the N content of fish being 3%; Wang et al 2014).…”

“…Currently, there is no legislative or regulatory requirement for a fin-fish producer to implement IMTA in Europe, despite legislation in Demark to reduce the environmental emission of fish farms, which is prompting IMTA development (Holdt & Edwards 2014). However, to operate effectively within a community and to expand, an industry requires a social licence to operate, going beyond what is just required for strict compliance with the regulation or law (Gunningham et al 2004).…”

Evaluation of IMTA-produced seaweeds (Gracilaria, Porphyra, and Ulva) as dietary ingredients in Nile tilapia, Oreochromis niloticus L., juveniles. Effects on growth performance and gut histology

“…The IMTA-produced seaweeds can represent multiple advantages for the aquaculture sector acting as nutrient biofilters, providing a possible mechanism for fish farmers to reduce the nitrogen loads from the cultivation effluents and being valuable additional crops (that use nutrients and other by-products from fish production) with commercial interest and with improved protein content (Holdt and Edwards 2014). Values are means±standard deviation (n=3).…”