Tuesday, April 3, 2018

04/04/2018: Sustainability in aquaculture – Water conservation may be the key

by Paul B. Brown, Purdue University, Department of Forestry and Natural Resources, West Lafayette, Indiana, USA

Sustainability is a term increasingly used to describe innovation in food production systems in general and aquaculture systems specifically.

The more sustainability is discussed, the more we realise how complex this goal can be. One of the more interesting aspects of the environmental component of sustainability is water, which, by definition, is an important consideration for aquaculture. However, the goal of sustainability demands a broader consideration of water resources than simply providing a medium for fish and shellfish culture.

Population increases and changing food habits are placing significant demand on food production systems. Between now and 2050, increases of 60-100 percent over current food production levels have been projected. The limiting resource in food production will be freshwater. Currently, food production, harvesting, processing, distribution, storage and presentation to consumer demands approximately 70 percent of the total global supply of freshwater.

Using current approaches, there is not enough freshwater to realise increases in food production of 60-100 percent above current levels. Future food production systems will need to consider the demand for freshwater as a critical component of sustainable food production.

At first glance, water and nutrition may not appear related. However, demand for water has been related to the water required to produce feed ingredients. Thus, the dietary formulation and associated water required to produce each ingredient contribute to the water footprint.

The more carnivorous species in aquaculture have the lowest water footprint because dietary formulations contain a high percentage of fishmeal and fishmeal requires relatively little water to produce, process and distribute. Species using high concentrations of fishmeal have water footprints lower than other species. Overall water footprints for mandarin fish and gilthead seabream are 88 and 500 m3/ton of fish produced, respectively (Pahlow et al. 2015, Table 1).

For more omnivorous species, water footprints can be over 2000 m3/t. Commodity feed ingredients (soybean, corn, wheat, canola, groundnut, lupin, cassava, etc.) require significant water resources during their production, processing and distribution cycles and use of those ingredients in diets increases the water footprint of that species. There is significant variability in the water footprint of common feed ingredients. Data in Table 2 are the total global average water footprints for several commonly used ingredients in aquaculture feeds, and not reflective of regional rainfall patterns, irrigation, etc.

However, these data indicate significant changes in water footprint as a function of ingredient usage. Data presented in Table 1 reflect only the dietary water footprint; complete freshwater demands for various species and production systems have not been developed.

Read the full article along with tables and figures, HERE.

Visit the Purdue University website, HERE.

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