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November | December 2011

Feature title: Algal concentrates in hatchery culture

The International magazine for the aquaculture feed industry

Culture of uni-cellular algae is a pre-requisite for successful operations in hatchery practices for

shrimp, crab and most fish.

Problems with algal culture and inherent disadvantages are described here, with their advantages in many cases being overcome by these disadvantages. The current study describes a novel, industrialised approach to negate these disadvantages and to place hatchery culture methods on a more con-sistent and stable platform.

This strategy was designed and imple-mented by Meriden Animal Health of the UK and is presented in the form of the Phyconmmix range of products.

The important factorsIt is estimated that over 40 species of

uni-cellular algae are in use in the aquacul-ture sector. They are generally recognised as difficult to grow in mass culture, particularly in low light (cloudy) or rainy conditions. The most important factors to consider in algal culture are temperature, salinity, pH, light intensity, photoperiod and nutrient

composition; the major expense in algal culture comes in the nutrient component.

Algae can require up to 17 different trace components in their culture medium.

The cost of production is further increased due to the requirement for specialist technicians. Large-scale culture increases the likelihood of breaches in bio-security, as pathogens can easily be trans-mitted from nearby culture tanks or via inadvertent intro-duction of insects etc.

Generally speaking, only one algal species tends to be cul-tured per single farmed species, therefore nutrient composition becomes a critical factor espe-cially when algae is entering its decline and death phases, and composition can therefore vary widely.

Since single species algae cannot provide all of the nutri-ents required by larval shrimp and fish, careful selection of a range of algal species which cover the spectrum of larval

nutrient requirements would seem a logical progression. Said species of algae can be grown in a sterile, hermetically sealed, bio-secure environment, then harvested at pre-determined times during the log phase of growth to optimize nutrient quality and consistency.

Algal concentratesin hatchery culture by John S Clark PhD, Aquatic Animal Health and Nutrition Technical Consultant, Bangkok, Thailand

30 | InternatIonal AquAFeed | november-December 2011 november-December 2011 | InternatIonal AquAFeed | 31

F: Algal concentrates

IAF11.06.indd 30 04/11/2011 08:42

Such algae can then be concen-trated via centrifuge then packaged and stored prior to use.

Such a system is flexible in terms of algal composition in that formula-tions for fish and shrimp larvae can be tailored to meet the require-ments of the larvae.

These concentrates are easily stored and applied to tanks and can also be used to enhance and enrich living feeds such as rotifers and Artemia nauplii. Its use reduces the need for mass culture tanks which can then be turned over to larval and nursery rearing and also reduces demand on labour time and equipment.

Larval quality is improved and development is accelerated, result-ing in healthier, stronger larvae which can be sold at a premium, thereby improving returns on investment.

Materials and methodsA trial was run comparing live

Chaetoceros with a commercially available algal concentrate (Meridens Phyconmmix

Shrimp ZM) as food sources for larvae of the white shrimp (Litopenaeus vannamei) in Thailand.

There were three control treatments and three test treatments in each study

group, tank size was five tonne and stocking density at nauplius was 200/litre. As well as their conventional feeds the test groups were fed on Shrimp ZM two times/day to Mysis 3 and then three times/day to

"Anectodal evidence

suggests that Zoea 2

Syndrome commonly

experienced in

many hatcheries is

nutritional in origin

but complicated by

secondary invasion

by bacteria or viruses

(Li. Pers. Comm.)"

30 | InternatIonal AquAFeed | november-December 2011 november-December 2011 | InternatIonal AquAFeed | 31

F: Algal concentrates

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10 | InternatIonal AquAFeed | november-December 2011 november-December 2011 | InternatIonal AquAFeed | 11

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than a single species diet and this will aid in the protection of target animals.

The improved water quality using concentrates may simply be a function of improved shrimp larval health lead-ing to improved vigour and appetite; it was noted feed consumption rates were higher but were non-detrimental to the larval environment. In such an environ-ment and with a much more complete, nutritionally balanced dietary regimen, it is not surprising that survival, growth, feed intake and resistance to stress are all significantly improved.

The developmental and structural advantages seen in the harvested post-larvae are of considerable interest to grow out farmers. In Plate 1 an examination of the carapace by SEM reveals the carapace to be thin and pliable, and therefore more prone to damage. By contrast, the carapace of animals fed on concentrate appears much denser and stronger, and would therefore be capable of resisting much more handling stress. Such considerations are of vital importance to farmers.

Even in the case of the compound eye, the eye seems incomplete in the controls (Plate 3) and this will of course impact on feeding behavior. It seems in general the concentrate fed animals are more devel-oped than controls (Plate 4) and therefore more suited to the rigours of pond life. Advantages are therefore not restricted to simple survival and growth; there are many subtle advantages that may escape direct attention but become evident on deeper study.

This developmental advantage is also observed in trials with concentrates in the nutrition of larval fish. In a recent study on larval sea bass (Lates calcarifer) apart from the advantages in terms of survival and growth, significant developmental accel-eration was observed in development of dentition (Plate 5), taste bud (Plate 6) and buccal microbial flora (Plate 7).

When factors such as ease of storage, ease of use, nutritional consistency, absence of potential pathogens, reduced labour cost and freeing of tank space are considered alongside the aforementioned performance superiority, the future of algal concentrates as a significant tool in hatchery culture seems secure.

Acknowledgements The author would like to thank all

concerned for their support during the development of the products and those involved in the demonstration of the prod-uct performance.

(see Figure 2) and significantly heavier (see Figure 3) than controls, which results in a significantly more favourable length/weight ratio (see Figure 4).

Similarly, feed utilisation seems superior in that the gut/muscle ratio favours muscle in the test groups (see Figure 5) and this is manifested as an increased Artemia nauplius and flake feed consumption (see Figures 6 and 7).

The final post-larvae are significantly stronger and more resistant to for-malin stress as evinced by survival rates displayed in Figure 8. Scanning Electron Microscope studies show significant differences in exo-skeletal structure and strength (Plates 1 and 2) as well as in development rate of the compound eye (Plates 3 and 4).

Such differences in stress survival and the structural improvement in the animals fed concentrates has significance to the grow-out phase of farming operations.

Finally, cost and return on invest-ment figure prominently in the

vocabulary of any hatchery operator. It can be seen from Table 1 that use of concen-trates does in fact lead to more profitable production of post-larvae and that this, coupled with the many advantages relating to ease of use make algal concentrates very attractive to hatchery operators.

DiscussionAnectodal evidence suggests that Zoea 2

Syndrome commonly experienced in many hatcheries is nutritional in origin but com-plicated by secondary invasion by bacteria or viruses (Li. Pers. Comm.). This study, in which no outbreak was experienced in the test groups, would tend to support that premise. The nutritional profile of a multi-algal species diet will be more complete

PL15 following the manufacturers feeding instructions.

Survival, length, weight, length/weight ratio, gut/muscle ratio, feed consumption, hepatopancreatic Vibrio count, formalin stress test were all recorded during this trial. Scanning Electron Microscope studies of the harvested post-larvae were also conducted.

The accumulated data allowed for a return on investment calculation to be

made between the use of live and concen-trated algae during larval shrimp culture.

ResultsBy Zoea 2 an obvious size difference was

noted (Li, pers. Comm.). At the same time, controls experienced

an outbreak of Zoea 2 Syndrome and a significant mortality occurred. It was note-worthy that water quality in the test tanks was viewed as superior to that observed in live controls. This has been mirrored in other trials (Pota, pers comm.; Somhathai, pers.comm).

Figure 1 shows mean survival in the three concentrate treatments to be sig-nificantly higher than in the live controls. Animals are significantly greater in length

32 | InternatIonal AquAFeed | november-December 2011

F: Feature

november-December 2011 | InternatIonal AquAFeed | 33

IAF11.06.indd 32 04/11/2011 08:42

18 | InternatIonal AquAFeed | november-December 2011

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