An overview of Julian Conway McGill's presentation by Matt Holmes, 
Features editor, International Aquafeed

Julian Conway McGill works for consultancy LMC international - a leading independent economic and business consultancy for the agribusiness sector around the world. Dr McGill is the head of south east Asia at LMC and he gave a presentation to the World Nutrition Forum in Cape Town, South Africa called: "Plenty of fish: How will the choice of species being domesticated influence aquafeed demand?"
The growth in beef production has been slower than pork and chicken. This also combines with the perceived health benefits of white meat.
"A less commonly noted though equally remarkable transformation, has been the growth in aquaculture production," says Dr McGill.
"Fish are even more efficient than livestock at converting feed into edible weight. As fish are buoyant, do not expend energy to warm their body and as they excrete nitrogen waste directly through their gills, they are able to channel more energy into weight gain than land animals."
Livestock, by contrast, need to expend energy to stand, maintain their body temperature and convert ammonia into urea among other energy requiring functions.
"Aquaculture therefore has the potential to be a very efficient source of meat", he continues.
"At their most efficient, salmon can achieve a ratio of one-to-one, with each kilogram of feed resulting in a kilogram of additional meat. This makes them 20 times as efficient at converting feed to meat as cattle."

Advantages of aquaculture
One of the challenging aspects of aquaculture is the sheer variety of different species in the sea with over 400 types of fish being successfully farmed as compared with fewer than 10 land animals. Dr McGill explains fish can be split into two broad categories: bulk white fish and luxury fish.
Bulk white fish farming has grown exponentially, thanks to its hardiness compared to higher value fish. These species provide protein at a low price and demand has been increasing with growing population. They have also replaced cheap fish from wild fisheries. The growth in these species has been predominantly driven by rapid production growth in China and South East Asia and is narrowly concentrated into three main groups: carp, catfish and tilapia.
In contrast production of luxury fish such as salmonids, high value white fish and crustaceans is largely driven by exports and demand is increasing with higher incomes. There are marked differences between these three categories.
With salmonids, Atlantic salmon has witnessed a spectacular growth in the last 30 years thanks to a combination of improved farming techniques and greater market appeal compared to other fish. The industry is dominated by a small number of global players, in particular Norway and Chile.
There is a large variety of high value white fish which are farmed, but only two species account for large volumes: seabass/seabream and amberjack. Market growth for both species has traditionally been limited, by their lower versatility compared with salmon. Aquaculture only accounts for a negligible share of total volume with most species still reliant on wild capture. China"s increasing demand for these species may mean production is forecast to expand in the future, says Dr McGill.
The crustacean category mainly consists of shrimp and prawns, which account for around 60 percent of output. Until the mid-2000s, capture accounted for most volumes, however, cultured shrimp has taken over in the last decade. The white leg prawn has come to dominate the market and the situation is likely to continue with white leg shrimp production growing rapidly, particularly in China.
Dr McGill says there are major differences in the extent to which the species have been domesticated.
"The most visible expression of the success of modern aquaculture in the west is salmonid culture, especially trout and Atlantic salmon. Both were formerly scarce and expensive luxuries and now are ubiquitous and comparatively inexpensive", he says.
"The Atlantic salmon industry is expected to continue to grow at fast rates. However, with limited potential for new sites and restrictions on biomass in Norway, production growth will be slower compared with historical rates.
"Chile will grow comparatively quickly as it recovers from the disease outbreak and advantage is taken of unused capacity in production licenses in favourable zones.
"Though many have been heralded as the "next salmon", so far no species of high value of white fish has emerged which can compete with the success of Atlantic salmon.
"By contrast, crustacean production has expanded at the fastest rate of the high value species."
Since 2008 farmed shrimp have accounted for a greater volume than caught shrimp. High demand for imports of shrimp by the US and EU as well as growing consumption in Asia have propelled shrimp production to even greater volumes."
He also adds that the fact that shrimps have multiple crops per year means their growth has been exponential rather than linear.
Dr McGill says the aquafeed is the most significant factor in determining the success of aquaculture. Feed determines the size and speed of growth in fish and influences the operation of the immune system and affects their disease resilience. It can also affect the environmental impact of aquaculture with undigested aquafeed, leading to ammonia leaching and pollution.

The impact of aquafeed
Aquafeed is usually the largest single operating cost in most aquaculture operations. The central challenge facing most species is that they presently require fishmeal produced from the capture of oily fish, such as anchovy and herring. However the capture of oily fish has been falling since the early 1990s. Since its peak in 1994, the annual capture of oily fish has declined from 38 million tonnes to 26 million tonnes a year. This has reduced the availability of fishmeal – a crucial feed ingredient. The solution would appear to be replacing fishmeal with cheaper protein sources such as soybean meal.
"However, persuading fish that vegetable protein sources are in fact as delectable as fishmeal has proven to be a great challenge," says Dr McGill.
Fish do not have a specific requirement for protein and lipid as such, they require amino acids and fatty acids that are constituents of the protein and lipid provided in the diet.
Not all feed ingredients provide these essential amino acids and fatty acids and this needs to be taken into account when formulating aquafeed.
There are over 400 species of fish each with a different feed requirement as opposed to livestock where the number of livestock is fewer than 10. There are a number of other problems which limits the ability to substitute different ingredients. 
The mix of ingredients needs to be digestible and palatable to limit the amount of feed left unwanted in the water and it needs to be pelletable to ensure it is in a form which can be consumed by the fish. Complicating this are the differences in the size of the mouth of different fish and the manner which they catch and devour their feed: tearing, grinding, chewing or sucking their food depending on the species.
The constancy of the pellet has to be such that it does not dissipate in the water.
"As a result the feed requirements of fish cannot be solved through least cost linear programming.
"Instead aquafeed remains more an art than a science, constantly in flux and reliant on experimentation and research," says Dr McGill.
Atlantic salmon is the one species that has achieved a significant reduction in fishmeal without compromising the health and growth of the fish.
"Solving this challenge for shrimp remains a major challenge, but also one that should prove immensely profitable to the successful feed ingredient producers, suppliers and compounders," Dr McGill concludes.

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