Black soldier fly larvae, an alternative for Aquaculture

Black soldier fly larvae, an alternative for Aquaculture

1 Jason Wu, [email protected]

An Evaluation of Black soldier fly (Hermetia illucens) larvae as an alternative protein and fat source for the aquaculture industry using a Barramundi (Lates calcarifer) model

Faculty of Veterinary Science University of Sydney

2013



Table of Content

Abstract ...................................................................................................................................... 3

1. Introduction ........................................................................................................................... 3

2. The importance of fish meal and fish oil ............................................................................... 5

2.1. Is fish meal and fish oil use sustainable? ........................................................................ 7

3. Alternatives to fish meal and fish oil ..................................................................................... 9

3.1. Plant alternatives .......................................................................................................... 10

3.2. Animal alternatives ....................................................................................................... 11

4. Nutritional needs of Barramundi (Lates calcarifer) ............................................................. 12

4.1. Protein requirements .................................................................................................... 12

4.2. Energy requirements .................................................................................................... 13

4.3. Digestive capacity of Barramundi ................................................................................. 14

4.4. Barramundi as a model for alternatives to fish meal and fish oil ................................. 15

5. Insect meals, an alternative to fish meal and fish oil .......................................................... 16

5.1. Black soldier fly (Hermetia illucens) larvae as a bioconversion tool ............................. 17

5.2. Potential function of Black soldier fly larvae within aquaculture ................................ 18

6. Conclusion ............................................................................................................................ 20

7. References ........................................................................................................................... 21



Abstract

Current trends in aquaculture production and predicted growth of the aquaculture industry

make fish meal and fish oil use economically and environmentally unsustainable. There is a

need to find alternatives to fish meal and fish oil that are more sustainable without negatively

impacting on productivity. Through a Barramundi model, representative of the high value

carnivorous species commonly produced, the effectiveness of substituting alternatives for

fish meal and fish oil within diets can be determined. Insects are part of the natural diet for

Barramundi making insect meals a logical alternative. Preliminary results show that insect

meals may be an economically and environmentally more sustainable option than fish meal

and fish oil. In particular, Black soldier fly larvae can convert around 58% of the dry matter

within an organic source into high quality animal feedstuff. Most studies have looked at Black

soldier fly larvae as either important for bioconversion or as an alternative feedstuff.

Understanding how the two uses may interact will help to determine the usefulness of Black

soldier fly larvae as a replacement for fish meal and fish oil. The aim of my research is to

address this gap in the literature, determining the nutritional content of Black soldier fly

larvae used as a bioconversion tool for poultry manure.

Keywords: aquaculture, barramundi, black soldier fly, fish meal, fish oil, nutrition

1. Introduction

Global aquaculture production has been steadily increasing since the 1970s and is expected

to exceed the capture fisheries output of 90 million tons of food fish (FAO, 2006). This increase

in supply has been due mainly to a steady increase in demand arising from an increasing global

population and consumption per capita (Diana, 2009). Like terrestrial farming, intensive



aquaculture production is completely dependent on the external supply of nutrients. For

finfish production systems, this means using either industrially produced feeds, farm made

feeds or natural food organisms (Le Franois, 2010). With the current 8.7% p.a. increase in

global aquaculture production, the acquisition and production of feed must therefore also

grow by a similar rate to ensure growth of the sector is not hindered. As with other farming

enterprises, feed represents a large proportion of expenditure, and current farming practices

mean that the main limiting factor in terms of feed is the use of fish meal and fish oil (Tacon

and Metian, 2008).

Fish meal and fish oil represent a crucial part of current industrially produced diets, with

approximately 20 million tonnes of total marine catches going into the production of fish meal

and fish oil (Natale et al., 2013). This is equivalent to 36% of the total output originating from

capture fisheries. However, total output from capture fisheries have not increased since the

1980s (FAO, 2006) and this means that current fish farming practices involving the use of fish

meal and fish oil must be optimised if the sector is to continue its rate of growth. Optimisation

of fish meal and fish oil use may be done through assessing alternatives with suitable models.

Barramundi (Lates calcarifer) represent the quintessential, high value, carnivorous,

intensively produced fish species. They are a significant part of aquaculture production in

Australia (Glencross, 2006). This makes Barramundi a suitable model for determining how to

improve fish meal and fish oil use. Through a Barramundi model, alternatives including plant

derived sources such as soy and lupin meals, rendered animal proteins and insect meals can

be assessed on their feasibility (Williams et al., 2003, Glencross et al., 2011). The use of plant

and animal derived alternatives to fish meal and fish oil have had mixed results (Glencross et

al., 2011). Another alternative that has gained attention more recently is that of insect meals.

Studies investigating the use of insect meals have shown that there is potential for insect



meals to be incorporated into aquaculture diets and reduce the reliance on fish meal and fish

oil (Kroeckel et al., 2012). Of particular interest has been the use of Black soldier fly (Hermetia

illucens) larvae. Preliminary studies showing an ability to replace a large proportion of the fish

meal and fish oil used in Rainbow trout diets (StHilaire et al., 2007b, Sealey et al., 2011).

The aim of this literature review was to discuss the use of fish meal and fish oil in

aquaculture, investigate the need for an alternative protein and fat source for aquaculture

diets, determine the effectiveness of using a Barramundi model on testing possible

alternatives and ultimately establish if Black soldier fly larvae are a suitable alternative to fish

meal and fish oil.

2. The importance of fish meal and fish oil

Fish meal and fish oil production are derived primarily from small pelagic fish species that

are not suitable for human consumption or have a limited market (Tacon and Metian, 2009).

The large use of fish meal and fish oil is due to its ability to provide high grade animal protein

and essential lipids in proportions perfectly suited for growing high value aquaculture species

(Tacon and Metian, 2008). Although the production of these high value species may represent

only a minor sector of net aquaculture production, they represent a disproportionally high

proportion of the market (Welch et al., 2010). Many of these high value species such as

Southern bluefin tuna (Thunnus maccoyii) and Barramundi are exclusively carnivores and this

dictates their nutritional needs (Tacon et al., 2009). In addition, some stages of fish

development, particularly in larval marine fish, require high proportions of fish oil and are

particularly susceptible to nutrient deficiencies (Sargent et al., 1997). Their demands for

essential amino acids must also be more readily met to ensure acceptable growth and survival

rates (Sargent et al., 1997). The need for both fish meal and fish oil becomes clearer when the



natural diets for these high value species are taken into account. In the wild, these fish would

feed primarily on smaller fish, often cannibalising smaller members of the same species

(Welch et al., 2010). In doing so, they are well adapted to digesting and utilising protein with

profiles specific to fish species (Tacon and Metian, 2008). Similarly, energy sources that are

utilised by these fish are reflected in their natural diets. These high value species are not

equipped to utilise carbohydrate sources of energy typically associated with plants (Le

Franois, 2010). Instead, they metabolise energy from lipids and proteins (Webster, 2002).

The main difference between the utilisation of lipids in terrestrial animals and aquatic animals

is that through bioaccumulation, marine sources of lipids are naturally high in

polyunsaturated fatty acids (Masclaux et al., 2012). Carnivorous fish not only rely more

heavily on these lipid sources of energy but also require the polyunsaturated fatty acids found

within these lipids to maintain growth as well as normal bodily functions (Bowyer et al., 2013).

Through public perception and recent scientific breakthroughs in the area of cardiovascular

health, consumption of omega-3 long chain polyunsaturated fatty acids (LC PUFA) has been

linked to human health benefits (Karakatsouli, 2012). These are fatty acids with unsaturated

olefinic groups within their structure (Finley, 2001). Within the group of polyunsaturated fatty

acids, LC PUFA are most readily found within marine sources (Finley, 2001). In being so, the

consumption of fish is now linked to the consumption of essential LC PUFA. This expectation

not only applies to wild caught fish but also products produced through aquaculture. In the

wild, these LC PUFA bio-accumulate up the food chain originating from algae and

heterotrophic protists as well as other microorganisms found in aquatic systems (Masclaux et

al., 2012). High trophic level species such as Barramundi obtain their nutritional requirement

for these LC PUFA via the consumption of smaller fish (Welch et al., 2010). Fish meal and fish

oil are the only natural source of LC PUFA available to aquaculture producers.



Fish meal and fish oil therefore play a major role not only in maintaining sufficient

aquaculture production but also in ensuring a high quality product as expected by the

consumer. This makes fish meal, and particularly fish oil, invaluable for the industry moving

into the future where understanding the nutritional value of food is becoming ever more

important. As production of aquaculture increases, demand for fish meal and fish oil will also

increase.

2.1. Is fish meal and fish oil use sustainable?

The majority of fish meal and fish oil is created through utilising non-food fish species that

have been harvested through capture fisheries. These non-food fish are primarily made up of

small pelagic forage species with approximately 73%, being in the order Clupeiformes (Tacon

and Metian, 2009). This order comprises species such as Anchovies, Pilchards, Sardines and

Menhaden. The raw materials required to make these products are also sourced from waste

products from large manufacturing companies in the form of fish trimming (Tacon and

Metian, 2009). In 2006, it was estimated that the aquaculture sector consumed 23.8 million

tonnes of these small pelagic fish species sourced from capture fisheries (Tacon and Metian,

2008). The percentage within total capture fisheries output for these species has remained

constant. However, net capture has increased by 8.79 million tonnes from the 24.5 million

tonnes captured in 1970 to be around 33 million tonnes in 2006 (FAO, 2006). Despite the

increase in net capture of these species, fish meal and fish oil production for the use of

aquaculture diets has not increased. Instead there has been increasing competition for this

resource from other animal industries such as pet food, intensive terrestrial animal

production and as whole feed for some aquaculture species (Tacon et al., 2009).

Over the past 30 years, the production of fish meal and fish oil has varied from year to year

(Tacon and Metian, 2008). On an overall basis however, net production of fish meal and fish



oil is similar to the quantities produced in the 1970s (Tacon and Metian, 2008). Total capture

fisheries output has plateaued since 1980 which is reflected in the capture quantity of these

small pelagic fish (Tacon et al., 2009). In contrast, the price of fish meal and fish oil over the

past 30 years have risen significantly. The cost of fish meal increased by 187.5% from

approximately US$400 per tonne to US$1150 per tonne, and by 209% for fish oil, increasing

from US$550 per tonne to US$1700 per tonne since 1983 (Welch et al., 2010). This marked

increase in cost is due to an overall increase in demand. Continued growth of aquaculture

production as well as increased demand from other sectors such as pharmaceuticals and

other livestock industries is the cause of increasing demand (Welch et al., 2010). Aquaculture

production in developing countries are expected to be the worst impacted (El-Sayed, 1999,

Tacon et al., 2009, Welch et al., 2010).

These general trends suggest that the current practice of using fish meal and fish oil in

aquaculture is environmentally and economically unsustainable. Aquaculture as an industry

has recognised this reliance on a finite resource and the use of fish meal and fish oil has

dropped throughout the sector. From 1995 to 2007, fish meal and fish oil use dropped by 47%

and 36% respectively within Salmonoid feed and 40% and 54% respectively within marine fish

feed (Tacon and Metian, 2008). Although the percentage used in diets per kilogram is falling,

the overall net use of fish meal has not changed (FAO, 2006). As producers aim to limit their

use of the product on a percentage basis, the growth of the sector means there will always

be a substantial reliance on fish meal for aquaculture production as a whole unless suitable

alternatives can be found. For this to be possible, it is important not only to identify

acceptable alternatives but more so, to identify a suitable model by which these alternatives

can be assessed.



3. Alternatives to fish meal and fish oil

Currently there are two possible courses of action if dependency on fish meal and fish oil is

to decrease within aquaculture production. The first option is to produce only herbivorous

species which naturally would have a lower reliance on both fish meal and fish oil, and the

second option is to find alternative sources of plant or animal protein and energy that can

replace fish meal and fish oil (Welch et al., 2010).

Most of finfish aquaculture production currently revolves around the use of omnivores and

carnivores such as Carp and Cyprinids (Welch et al., 2010). These species represent the major

output for aquaculture production, and require adequate protein and energy levels that

would normally be found in other fish in their natural habitats. Production of lower value

omnivorous species such as the Tilapia (Oreochromis spp.) represent a significant portion of

production in developing countries (Tacon and Metian, 2008). Aquaculture production in

these countries provides a high value protein source for relatively low cost, helping to improve

economic growth as well as the overall standard of living (Tacon et al., 2009). Historically,

these products have been consumed over many generations and are part of the national diet.

Moving exclusively to the production of herbivorous species would set back these production

systems and it may not be economically or socially viable (Tacon et al., 2009). This makes

finding and developing an alternative to fish meal and fish oil the major goal for the industry

moving into the future.

The search for alternatives of fish meal and fish oil has generally been directed at plant or

animal derived sources. Plant and animal derived alternatives for fish meal have been shown

to work in preliminary studies even being able to replace a large majority of fish meal for

species including Turbot (Psetta maxima) (Regost et al., 1999), Rainbow trout (Oncorhynchus

mykiss) (Cabral et al., 2011), Cobia (Rachycentron canadum) (Saadiah et al., 2011),



Barramundi (Lates calcarifer) (Glencross et al., 2011), Atlantic salmon (Salmo salar) (Espe et

al., 2006)and European seabass (Dicentrarchus labrax) (Kaushik et al., 2004). In each of these

cases however, poor intake was directly related to poor performance suggesting that for each

species, there is threshold need for fish meal at least to maintain palatability of the pellet.

3.1. Plant alternatives

Plant protein sources are used extensively throughout terrestrial farming practices (El-

Sayed, 1999). The potential for plant alternatives to replace proportions of fish meal has been

readily shown but the lack of polyunsaturated fatty acids within plant alternatives makes

them unsuitable as a fish oil replacement (Turchini et al., 2009). Of the possible plant

alternatives for fish meal, soy bean meal has been shown as having the biggest potential

(Boonyaratpalin et al., 1998, Zhou et al., 2005). Soy bean meal has a protein profile

comparable to fish meal, lacking only in methionine and lysine levels (Blaufuss and Trushenski,

2012). The major issue with the use of soy bean meal as an alternative to fish meal are the

antinutrients that may limit the digestibility within finfish species (Rackis, 1974). Usage of

soybean meal would require the prior removal of these antinutrients if production

comparable to fish meal is to be achieved (Zhou et al., 2005). In addition to these antinutrient

factors, Boonyaratpalin et al. (1998) trialled soy bean meal alternatives through a Barramundi

model and established that there was a threshold level at which soy bean meal could be used

as a replacement before palatability of the pellet suffered. Although plant sources of protein

and energy are widely used throughout terrestrial farming, the nutritional needs and digestive

capabilities - especially of carnivorous fish - limit the potential of any plant alternatives for

fish meal and fish oil.



3.2. Animal alternatives

Animal by-products such as poultry by-product and abattoir by-product, in the form of meat

and bone meal, are potentially cost effective replacements for fish meal (Williams et al.,

2003). The inclusion of meat and bone within aquaculture diets has given mixed results (Ai et

al., 2006). Replacing fish meal with a mix of poultry meal and soy bean meal was inversely

related to weight gain of Australian snapper (Pagrus auratus) (Quartararo et al., 1998) but

within Seabream (Sparus aurata), high levels of poultry meal inclusion did not negatively

affect growth (Nengas et al., 1999). These contradictory results demonstrate the

inconsistency with the production of animal alternatives (Booth et al., 2012). Animal

alternatives can vary greatly in nutritional content (Hernndez et al., 2008). Additionally, the

use of meat meals may not be viable for developing countries, where meat and bone meal

production is seasonal, causing a large fluctuation in cost (Sathe, 1968). The high variability

of animal alternatives for fish meal also apply for animal alternatives to fish oil. Animal fat

composition is dependent on diet, species and age (Turchini et al., 2009). Due to current

rendering practices involving the input from several sources, the resulting animal by-product

is inconsistent (Turchini et al., 2009).

As a whole, plant and animal derived sources of protein have shown good ability to replace

portions of fish meal in some diets. However, the accessibility of these protein sources is

limited in developing countries where a large proportion of aquaculture production is

occurring where most fish meal alternatives would instead be incorporated into human

consumption (Sathe, 1968). In addition to this, rendered animal alternatives are inconsistent,

having variable nutritional value from batch to batch. An alternative for fish meal and fish oil

must not only be cost effective but also reliably meet the nutritional demands.



Insect meals have recently gained momentum as a possible source of protein and energy,

representing a cheap and potentially controllable alternative. In particular, Black soldier fly

larvae have been trialled in Rainbow trout and Turbot diets with promising results , (StHilaire

et al., 2007b, Sealey et al., 2011, Kroeckel et al., 2012). Insect meals have also been shown to

allow for enriching through dietary intake and may possibly allow for enrichment of

polyunsaturated fatty acid levels. Preliminary results show the potential of Black soldier fly

larvae but there is a lack of knowledge with respect to how such an insect meal would work

within current commercial production systems. Developing a model through a suitable

species such as Barramundi will help to improve our understanding.

4. Nutritional needs of Barramundi (Lates calcarifer)

Barramundi, also known as Asian sea bass, is a carnivorous species belonging to the Family

Centropomidae (Glencross, 2006). They are distributed throughout tropical and subtropical

waters of the Pacific and Indian ocean and are widely cultured throughout South-East Asia

and Australia (Glencross et al., 2011). Barramundi are catadromous, starting the first few

years of life inland within freshwater rivers and lakes before migrating to the sea for sexual

maturation and spawning (Webster, 2002). In their natural environment, Barramundi are

exposed varying levels of salinity as well as water quality. Being adaptable to such wide water

parameters makes Barramundi an ideal fish for culture.

4.1. Protein requirements

As an exclusively carnivorous fish, Barramundi are accustomed to digesting high quality

protein and utilising non-carbohydrate forms of energy (Webster, 2002). The protein

requirements for Barramundi have been examined in several studies and were found to be

typical of other high trophic level carnivores (Glencross, 2006). These studies showed that



Barramundi require between 450 550g/kg-1 of crude protein within their diets depending

on age, location and stage in the production cycle (Glencross, 2006). This level of crude

protein represents only an estimation of the total amount of amino acids required to optimise

growth. Within the protein that makes up around 45 - 55% of the diet, there must be

adequate amounts of essential amino acids, amino acids which cannot be produced within

the fish (Webster, 2002). It is hypothesised that the main limiting amino acids for Barramundi

are lysine , methionine, threonine, and tryptophanthe, which are the same as for other fish

but has yet to be proven (Glencross, 2006). The relative success of plant and animal derived

alternatives for fish meal in terms of growth suggest that the essential amino acid

requirements can be met through feedstuffs other than fish meal (Li et al., 2009). From these

studies however, it was shown that when performance suffered due to the use of an

alternative of fish meal being used, it was due to a lower feed intake (Welch et al., 2010). This

suggests that there may be issues with palatability when using alternatives and could be due

to a nonessential amino acid that may be more prevalent in fish meal than with alternatives

(Eusebio and Coloso, 2000).

4.2. Energy requirements

Energy requirements for juvenile Barramundi have been found to be approximately

20kjDE/g-1 (Webster, 2002, Glencross, 2006). Being a carnivorous fish, Barramundi have

limited capacity to process and utilise carbohydrate forms of energy (Le Franois, 2010). The

energy requirements for Barramundi must therefore be met through non-carbohydrate feed

stuffs (Webster, 2002). The majority of the energy within a Barramundi diet must therefore

be delivered in the form of lipids (Turchini et al., 2009). Unlike terrestrial farming however,

lipids also play a secondary role of delivering essential fatty acids crucial for normal growth,

development and nutritional value of the animal products produced (Welch et al., 2010). In



addition to this, high levels of lipids have been found to be useful for protein sparing

(Webster, 2002). If the energy requirements can be met through lipids, the amino acids within

the diet will be utilised for growth and maintenance instead of being broken down as an

energy source (Webster, 2002). Although the ability to provide the nutrient requirements for

Barramundi is theoretically an important aspect of culture, ensuring that these nutrients are

accessible is also important.

4.3. Digestive capacity of Barramundi

The capacity for digestion is heavily reliant on enzyme activity within the gut and will

determine what nutrients can be taken from a specific feedstuff (Smith, 1980). Understanding

which enzymes are present allows adequate determination of how digestible feed stuffs may

be (Sabapathy and Teo, 1993). In this way, if the nutrient within a pelleted feed is determined

to satisfy nutrient requirements, it must then be determined if the nutrient is accessible. This

is explored in Sabapathy and Teo (1993) for Rabbitfish (Siganus canaliculatus) which are

herbivorous and Barramundi (Lates calcarifer) which are carnivores. Through this study, it was

determined that the digestive enzymes present in each species was correlated with their

natural feeding habits. Carbohydrases such as amylase, laminarinase, maltase, sucrase and

tehalase were found in the gut of Rabbitfish whose natural diet consists primarily of marine

algae. In Barramundi, carbohydrases were not only found in lower concentrations but also

had reduced activity. Contrastingly, proteolytic enzymes such as pepsin and aminopeptidase

were found in significantly higher levels. This showed a limited ability to digest starch within

Barramundi, however, amylase activity is not completely void. The limited amylase activity

would help to digest glycogen, which is a form of energy storage utilised by plants. Chitinase

activity is also determined to be much higher in Barramundi than compared to Rabbitfish.



This is important as chitin is used by insects for the binding of protein and shows that insects

do comprise a proportion of natural Barramundi diet (Finke, 2013).

Understanding nutrient requirements and nutrient accessibility for Barramundi allows for

the development of industrially produced feeds. The important aspects to consider with

pellet production is the limited function of amylase and the presence of chitinase. Although

amylase activity is limited, starch can still be partially utilised by Barramundi (Sabapathy and

Teo, 1993). This is important as pellet quality is highly dependent on the presence of

gelatinised carbohydrates making pelleted feed possible and suitable for Barramundi

(Zimonja and Svihus, 2009).

4.4. Barramundi as a model for alternatives to fish meal and fish oil

Within Australia, major input costs associated with rearing Barramundi are the costs of

labour, utilities and feed (up to 40% of on-farm costs) (Williams et al., 2003). As labour and

utility costs have little room for improvement, finding a more cost effective feed is an area of

potential improvement that has been explored thoroughly. Barramundi culture within

Australia utilises high protein, industrially produced diets with fish meal as the main source

of protein (Glencross, 2006). Replacement of fish meal for Barramundi diets has been tested

with alternatives such as meat meal (Williams et al., 2003), soybean meal (Boonyaratpalin et

al., 1998) as well as various plant proteins (Glencross et al., 2011). Williams et al. (2003)

showed that meat meal could potentially be used as a complete replacement for fish meal if

the limiting amino acids, lysine and methionine, were supplemented into the diet.

Boonyaratpalin et al. (1998) concluded that if palatability of soybean products could be

improved, they could replace up to 15% of fish meal within Barramundi grow-out diets. These

studies demonstrate the capacity to replace large proportions of fish meal within Barramundi

diets but also demonstrate the shortfalls with current plant and animal alternatives.



Our understanding of the nutrient requirements for Barramundi as well as their digestive

capabilities allows for the identification of alternatives to fish meal. With the digestive

capacity of Barramundi being representative of other carnivorous species (Sabapathy and

Teo, 1993), they are a suitable model for finding an alternative to fish meal and fish oil which

may then be applicable to other high value species. However, establishing alternatives to fish

meal cannot simply be done haphazardly by choosing cheaper feedstuffs which meet the

nutritional requirements on paper. An alternative to fish meal and fish oil must not come at

the cost of production or environmental sustainability. Plant alternatives have been shown to

be cost effective but limiting to productivity, and animal alternatives do not hinder

productivity but accessibility in developing countries is limited. Insect meals have the benefit

of being potentially cost effective whilst being environmentally sustainable and meeting

nutritional requirements (van Huis, 2013).

5. Insect meals, an alternative to fish meal and fish oil

The need for environmentally and economically viable alternatives to fish meal and fish oil

represents the greater need to find alternative protein and energy sources as demand

becomes limited by supply. In recent years, there has been a push for more environmentally

and economically sustainable farming practices to be employed both on terrestrial and

aquaculture enterprises (Tacon and Metian, 2008). Increasingly, the prospect of using insect

meal to replace higher value proteins in animal feed is being studied.

Throughout Western society, the use of insect meal has not been seen as socially acceptable

(van Huis, 2013). In countries where insect consumption is part of the national diet, the use

of insect meal and by-products is more readily adopted (van Huis, 2013). Traditional

terrestrial farming cannot utilise insect meal as readily as aquaculture. The natural adaptation



that allows many omnivorous and carnivorous fish to feed on insects as part of their natural

diet is not present in the majority of terrestrially farmed species. This natural adaptation is

the ability to produce chitinase within the gut. Chitinase aids in the digestion of chitin, which

is a major component of the exoskeletons of insects and limits digestibility (Kroeckel et al.,

2012). The presence of chitinase as well as being a natural food source for some aquatic

animals makes insect meal a logical alternative to fish meal and fish oil.

In addition to being well suited to being an aquaculture feed stuff, insects are utilised for

the bioconversion of organic waste products. Approximately 1.3 billion tonnes of food is

wasted from the food produced each year (Gustavsson et al., 2011). This represents a large

proportion of nutrients produced through agriculture being lost to landfill and broken down

to methane (van Huis, 2013). Utilising this waste for the production of compost has be done

for hundreds of years through the use of earthworms and microorganisms (Wang et al., 2013).

Interest in waste utilization has moved to the Black soldier fly (Hermetia illucens) (Liu et al.,

2008). In this sense, the utilisation of insect meal within aquaculture diets is not only a logical

alternative in terms of natural feed stuffs but also as a management tool for organic sources

of waste.

5.1. Black soldier fly (Hermetia illucens) larvae as a bioconversion tool

Black soldier flies are a non-pest species belong to the Family Stratiomyidae and thrive in a

wide range of environments, spreading through the tropics and subtropics (Diener et al.,

2009). Adult flies are about 20mm in length, easily distinguished by their long antennae

(Gennard, 2012). Mature larvae are also about 20 mm long, flattened and have a dull tan

colour (Mullen and Durden, 2002). The lifecycle of black soldier flies begin with about 500

eggs laid in a cluster which hatch within four days (Mullen and Durden, 2002). Under ideal

conditions of about 270C, the five larval instars last two weeks before the larvae migrate out



of their food substrate for pupation (Gennard, 2012). Pupation occurs over two weeks and

results in the emergence of an adult Black soldier fly with a lifespan of about eight days

(Mullen and Durden, 2002). These adults then spend the rest of their short lifespan finding a

mate and laying eggs (Mullen and Durden, 2002). This means that all of the feed consumed

must be stored leading up to pupation must be at a level that would sustain the adult flies for

their lifespan. Black soldier fly larvae are therefore vigorous eaters and it is this attribute that

makes them a useful bioconversion tool (Li et al., 2011). Furthermore, once the larvae is ready

for pupation, they readily crawl up 450 ramps to move away from the food source and can be

easily harvested by exploiting this natural instinct (Sheppard et al., 1994).

Several studies explore the possibility of bioconversion of agricultural waste into high value

animal protein, useful as feed ingredients. Li et al. (2011) successfully used Black soldier fly

larvae to convert dairy manure into biodiesel and sugar. From this study, 1.24kg of dairy

manure was converted into 15.8g of biodiesel and 54.4g of insect meal using approximately

1200 Black soldier fly larvae. Sheppard et al. (1994) also used Black soldier fly larvae as a

bioconversion tool, converting hen manure to high quality feed stuff. Results from this study

show that Black soldier fly larvae reduce manure dry matter by up to 58%. Additionally, the

nitrogen and phosphorous reduced by up to 75% with the use of Black soldier flies. The result

of this bioconversion is a self-harvesting feed stuff with approximately 40% protein and 30%

fat.

5.2. Potential function of Black soldier fly larvae within aquaculture

The ability of Black soldier fly larvae to convert low value organic waste products into a high

value feedstuff accessible to carnivorous fish may limit the need for fish meal and fish oil in

the aquaculture industry (Sheppard et al., 2002). For aquaculture production systems which

are in close proximity to intensive agricultural production systems, Black soldier fly larvae may



be beneficial to both parties (Sheppard et al., 1994). The larvae may be used to minimise the

costs associated with removing solid organic waste from agriculture production as well as

provide a secondary income for the agricultural property (Li et al., 2011). This secondary

enterprise would be able to supply a useful feedstuff with relatively low cost compared to fish

meal and fish oil (Li et al., 2011).

Enrichment of the Black soldier fly larvae has also been found to be possible (StHilaire et

al., 2007a). This is because nutritional composition of insects is thought to be largely

accounted for by their diets and stage of development (Stanley-Samuelson and Dadd, 1983).

Modification of the nutritional content within Black soldier flies opens the door for value

adding such as lipid enrichment. StHilaire et al. (2007) showed that through feeding fish offal

to Black soldier fly larvae, resulted in larvae that were 30% lipid, of which, 3% consisted of

polyunsaturated fatty acids. This is in contrast to Black soldier fly larvae reared off cow

manure which had 21% total lipids with negligable amounts of long-chain unsaturated fatty

acids (Sheppard et al., 1994). Furthermore, StHilaire et al. (2007) demonstrated that levels

of polyunsaturated fatty acids did not change with increased levels of diet enrichment. This

means that lipid enrichment can be obtained within Black fly larvae with the incorporation of

only minimal input.

With preliminary studies indicating the capacity for Black soldier fly larvae to meet the

nutritional demands of fish and the potential economical and environmental savings, Black

soldier fly larvae may be an alternative for fish meal and fish oil but there is a lack of

knowledge about the relationship between larval diet and if it alters larval nutritional content.

The objective of my research is to determine if rearing Black soldier fly larvae using poultry

manure affects larval composition.



6. Conclusion

The dependency on fish meal and fish oil from wild caught fish stocks, may hinder the

growth and development of aquaculture production. This review established the need for an

alternative protein and fat source for the aquaculture industry which relies heavily on finite

resources in the form of fish meal and fish oil. Investigating such alternatives requires a

suitable model. Barramundi represent the quintessential carnivorous aquaculture species and

this makes them the ideal model for which an alternative, such as insect meal, can be tested.

Black soldier fly larvae present themselves as a potential alternative to fish meal and fish oil

primarily because of the economic and environmental benefits. Additionally, their ease of

harvesting and controllable elasticity, in terms of nutritional content, make them an excellent

candidate for use as an alternative. Investigating the nutritional content of Black soldier fly

larvae meal reared off poultry manure will therefore provide insights as to the viability of this

feed stuff as an alternative within aquaculture production.



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Black soldier fly larvae, an alternative for Aquaculture