Development of more efficient feeding techniques and formulation of feeds that include less fishmeal is expected to lower the amount of fish meal protein needed to produce a given amount of high-valued carnivorous species like shrimps and salmon.
Sustainable Aquaculture Expert
The major aquatic animal protein meals and lipids are, in terms of global production and market availability, for fish and shellfish meals and oils. They can be produced from whole fish, fish remains or other fish by-products. Around 25 percent of fishmeal and fish oil was produced from by-products in 2009, and this amount has been increasing around 1–2 percent per year (FAO, 2012). About 35 percent of world fishmeal production was obtained from fish excesses in 2012 (FAO 2014). Two of the main stocks of anchoveta in the Southeast Pacific, Alaska pollock (Theragrachalcogramma) in the North Pacific and Atlantic herring (Clupea harengus) stocks in both the Northeast and Northwest Atlantic are fully fished. Chub mackerel (Scomberjaponicus) stocks are fully fished in both the Eastern Pacific and the Northwest Pacific; most of the pelagic stocks are considered either fully fished or overfished (FAO, 2014). Overfishing leads to negative ecological consequences and reduces fish production, which further causes negative social and economic consequences.
To reduce the pressure on wild fish stocks, different alternatives are and have been studied for marine raw materials and many of these alternatives have shown to be promising.
Insects tend to have high protein and fiber content, as well as excellent amino acid compositions. Studies have shown insects nurtured on waste can be transformed into protein feed material and used as substitute for fishmeal. Moreover, this does not affect growth rates or palatity, although performance depends on the specific fish and insect species used. Insect meal is presently ten times more expensive than other protein feeds. However, insect meals could become price competitive in the future as there is considerable potential for reducing the price by increasing the scale and efficiency of production.
Microalgae have shown to be promising alternative to the conventional marine originated ingredients in fish feeds; these have though been limited to DHA-producing species. Production of n-3 LC-PUFA by microalgae has mainly focused on species like Schizochytrium, Crypthecodinium and Ulkena that are cultured by fermentation under controlled environment. This production is still in development stage, and production volumes are low and cost is high, far more expensive than for fish oil and meal.
Microalgae will likely become available as a feed ingredient in the future, but for now, they are unlikely to fulfill aquaculture demands for n-3 LC-PUFA, as will alternative marine sources of n-3 LC-PUFA, such as krill and calanoid copepods. Production volumes are expected to be low, and there is a concern over sustainability and that harvesting down the trophic chain may have negative effect on higher trophic species reliant on these zooplanktons.
Schizochytrium limacinum meal can be used as the central lipid source in diets for giant grouper (Epinephelus lanceolatus), containing 40% soy and algal ingredients; it returned similar growth as feed based on fish ingredients. Higher DHA:EPA ratios in fish fillet are found with increased use of S. limacinum meal in the feed. It is suggested that a blend of soybean meal, soy protein concentrate, and S. limacinum can substitute at least 40% of marine protein sources, without significantly affecting fish performance or condition, and it is possible to use it as the main lipid source in feed for E. lanceolatus (García-Ortega et al., 2016).
Norwegian seaweed like P. palmata can be used for production of feed. The combination of beneficial compounds and compounds possessing potential health risks are evident in several of the analyzed species. Both the red alga V. lanosa and the brown alga (A. esculenta) could serve as a good protein sources, but the level of iodine (V. lanosa) and arsenic (A. esculenta) complicate the utilization of the whole plant as algae meal. That will cost extraction of single compounds, such as proteins, minerals and/or fatty acids, for use as ingredients in feed production (Mæhre et al., 2014).
It has been found that an addition of 4 and 8% of brown seaweed meal (from a cultivated system) and green seaweed meal (from natural stocks) in commercial shrimp feed sustained sufficient growth, and survival of juvenile L. vannamei reared in intensive RAS (Cárdenas et al., 2015). Amaya et al. (2007) showed that fishmeal can be completely replaced using vegetable protein sources in practical shrimp feeds without negotiating production and economic outcome of pond reared L. vannamei.
It also has been proved that genetically engineered Camelina (C. sativa) can be a realistic source of n-3 LC-PUFA and could substitute fish oil (FO) in feed and provide sufficient levels of important fatty acids in farmed fish that could sustain their nutritional quality for the human consumers. Betancor et al. (2015), found that, Camelina oil, containing 20% EPA was suitable for feeding Atlantic salmon and sustained the same nutritional quality of the fillet, as fed with high levels of EPA and DPA. Lazzarotto et al. (2015) found that trout (Oncorhynchus mykiss) fed a 100% plant-based diet over a 3-year breeding cycle can produce ova and viable alevins.
Two different commercial types of seaweed meal have been tested for Arctic charr and Tilapia. No negative effects were found on growth and feed utilization. Moreover, Rainbow trout, fed with Blue Mussel meal did not show negative effect in terms of growth, feed utilization or physical parameters and found to be comparable to fishmeal as protein source in feed (Arnason et al., 2015). Blue mussel meal and seaweed meal are interesting and sustainable ingredients in fish feed in the Nordic countries, as these raw materials are locally present and therefore can lower the carbon footprint of fish feed in the area.
The availability of micro algae for use as feed ingredients still needs a way to go before it will be a real alternative as raw material in fish feed production, but the outlook is promising. Development of more efficient feeding techniques and formulation of feeds that include less fishmeal is expected to lower the amount of fish meal protein needed to produce a given amount of high-valued carnivorous species like shrimps and salmon. For more sustainable production, the effort should also be on other species such as carps, tilapia and catfish.