Fish & Aquaculture

INTRODUCTION TO AQUACULTURE

The practise of farming aquatic organisms such as fish, shellfish and aquatic plants is known as aquaculture. In recent years, the decline of wild fish stocks, combined with an ever increasing population has highlighted the shortfalls of capture fisheries and has resulted in massive growth of the aquaculture industry at 11% per year. In 2008, the global human consumption of fish and shellfish was 52.5 million tonnes, worth US$98.4 billion.  Such is the demand for healthy sources of protein (in particular omega 3 fatty acids) that it is now estimated aquaculture accounts for half of that fish and shellfish consumed by humans globally. In some countries such as China, this figure is much higher- with over 80% of fish for human consumption coming from farmed sources.

The concept of aquaculture is simple; to produce your chosen species with minimum input and in minimum time. To do this you must understand the influences that affect the growth of the organism. This principle is shown below:

All of these influences can be managed in some way and it the effective management of these which leads to successful aquaculture:

 

 HISTORY OF AQUACULTURE

Aquaculture is by no means a recent concept. Across the globe, pockets of aquatic production have been going on for literally thousands of years. Indigenous people from Australia may have grown eels in large volcanic floodplains as early as 6000BC as the main part of their diet. It has been well documented that in Far Eastern countries, growing various eels and carps in paddy fields along with rice began around 2500BC. Europe also has a long history of aquaculture, with the Romans and early Christian monasteries growing fish in ponds thousands of years ago.

During the industrial revolution, improvements in transport meant fresh fish could be supplied from the coast to inland areas relatively inexpensively, making aquaculture less popular. However, that same industrial revolution has now led to overfishing of wild stocks and a global population boom- which demands more fish. Over the last 50 years, this has made aquaculture a truly global industry, growing faster than any other food sector.

Growth of the aquaculture industry in such a short time has inevitably led to questions of sustainability. There is widespread acceptance that aquaculture will be relied on more as the global population continues to grow, therefore to provide in the future it must, and is, moving towards sustainability.

Examples of sustainable practices include: 

  • Culturing ‘Vegetarian’ fish
    Fish lower in the food chain (carp, tilapia and catfish) can be fed a vegetable based diet in contrast to higher level species (salmon, tuna, cod) which must be fed a diet high in fish protein. 
  • Improvements in feeding efficiency
    Improving the composition of feeds (by reducing the amount of fish meal), selective breeding of fish more efficient in converting food into flesh, and improvements in feeding techniques to reduce waste. 
  • Closing the lifecycle of species in captivity
    So there is no need to gather new stock from the wild
  • Supporting local communities
    Protecting natural ecosystems and improving the social and economic prospects of local people
  • Reducing or eliminating waste output
    Integrated farming systems such as aquaponics, moving away from only farming one species at a site to an ecosystem based approach to production. Waste products from one species can be used to produce another. In this way various species from different levels in the food chain can be grown together. This can result in zero waste emissions, many different crops at harvest and crops that are harvestable at different times.

 FISH WELFARE

The Farm Animal Welfare Council (part of the DEFRA) was set up to ensure that any animal kept by man is at the very least protected from unnecessary suffering. A list of provisions that should be made for farmed animals to ensure both their physical and mental fitness was laid out in the form of Five Freedoms to be adhered to. The Five Freedoms have been widely used in marketing and have been the foundation of much legislation concerned with animal welfare both in and outside the UK. Although developed for terrestrial farms, these rules also apply to aquaculture as shown below: 

  • Freedom from Hunger and Thirst – by ready access to fresh water and a diet to maintain full health and vigour. Specially formulated diets are continually being improved or developed for each species being cultured. This tailor makes the diet to the nutritional needs of each animal.
  • Freedom from Discomfort – by providing an appropriate environment including shelter and a comfortable resting area. This is particularly important in aquatic species as there are so many water quality parameters to be adhered to and these are different depending on the species being cultured. During transportation of live fish are particularly susceptible to stress and must be kept in secure dark containers kept at constant lower temperatures, with lots of aeration/oxygenation and a method for carbon dioxide gas removal.
  • Freedom from Pain, Injury or Disease – by prevention or rapid diagnosis and treatment. Disease spreads much faster in the aquatic environment. It is more difficult to spot problems that individuals may have in the aquatic environment. If many fish are kept together in one tank, it is harder to spot skin lesions that may be present in some of the population and therefore treat the fish before it spreads to the rest of the tank. Treating health problems often involves treating the whole tank/water instead of the individual. During harvest on commercial salmon farms, fish are stunned with electrocution before the gills are cut, ensuring the animal is not in ‘pain’ or stressed.
  • Freedom to Express Normal Behaviour - by providing sufficient space, proper facilities and company of the animal’s own kind. Generally, fish like sticking together. Optimal stocking densities are designed to ensure the animal has enough space/water but also is not stressed at being in low densities. Larger fish are kept in larger tanks and fish which only like to live or breed on certain substrate (gravel, sand, weed, etc) are provided with the appropriate substrate.
  • Freedom from Fear and Distress – by ensuring conditions and treatment which avoid mental suffering. Dark tanks with smooth edges are used particularly during egg and larval production to reduce stress. Grading of the fish ensures canabalistic species (such as barramundi will not eat and injure each other.

FISH FOR AQUAPONICS

A large variety of aquatic species both cold and warm water; have been successfully cultured in aquaponic systems, including tilapia (Oreochromis spp), rainbow trout (Oncorhynchus mykiss), African catfish (Clarias gariepinus) (Arctic char (Salvelinus alpinus), barramundi (Lates calcarifer), European perch (Perca fluviatilis) , yellow perch (Perca flavescens) common and koi carp (Cyprinus spp), goldfish (Carassius auratus) and crustaceans such as red claw crayfish (Cherax quadricarinatus) and giant freshwater prawn (Macrobrachium rosenbergii). Tilapia, particularly O.niloticus is the most common fish cultured in aquaponics by far. Its tolerance of fluctuating water conditions and crowding, omnivorous diet and resistance to disease lends itself well to aquaponic conditions.

Click on the fish species below to find more information on culture conditions:

Nile Tilapia                        Common carp

 

Barramundi                       Yellow Perch

 

Rainbow Trout                    European Perch

 

African Catfish                 Giant Freshwater Prawn

 

Arctic Char

 

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