Meryl Williams Science Alert 22 Nov 10;
Aquatic biodiversity provides one of humanity’s most important food resources. Most of the world’s oceans and all inland waters are fished, providing protein and micro-nutrient rich food.
Driven by a growing global population, demand for fish is rising and adding to the pressures on the supply side – overfishing, inefficient aquaculture, climate change, acidification and deoxygenation of oceans, pollution from chemicals and dumping of rubbish, disruptions to nutrient, carbon and water cycles.
The export value of world trade in fish, some US$63 billion in 2003, is more than the combined value of net exports of rice, coffee, sugar and tea. Fishing is also a vital and valuable source of employment and income in both the developed and developing world.
About 30 million fishers make a living directly from the sea and an additional 200 million are dependent on fisheries related activities and industries. Most of these and the one billion people who rely on fish as their main source of animal protein live in developing countries.
Fishing has, over millennia, become a vital part of human life. We take eating fish for granted. For many the popular image of fishing focuses on the people involved, and the dangers in getting fish to the plate, such as in the Discovery Channel documentary series, Deadliest Catch, now shown in 150 countries.
Sustainability debates do not generate such wide spread attention. Yet, a more compelling drama is played out each day in fisheries around the world – the daily struggle of fish workers, many of whom are women, to earn enough to live. Most of the people relying on fishing are labourers on other people’s boats or in processing factories. Few of them have job and resource security and most face declining resources and declining aquatic biodiversity.
Many fisheries are still engaged in a ‘race to fish’ approach, with catches often determined by the size of the boat and illegal fishing practices, rather than sustainable management approaches. These fishers are eager to meet the rising demand for fish in the hope of a better life.
The challenge is two-fold, ensuring that aquatic resources continue to contribute to food security and people’s livelihoods, while not compromising aquatic biodiversity. The successful management of fish production requires an integrated approach and a watchful eye on biodiversity.
Sustainable catches
Although we are tempted to hope that aquaculture can solve the problems of overfishing and save wild fisheries, this is a false hope, no matter how alluring. Instead we must deliver sustainable catches, and productive aquaculture.
Aquaculture is the key to future increased fish production. At most, capture fisheries may hold their own – although a more likely scenario is that catches will be reduced to achieve sustainability.
Today almost half of all fish eaten are farmed. This is a revolution in fish production but also a great challenge from to aquatic biodiversity at genetic, species and ecosystem levels.
The world’s fish catch is biodiverse. Thousands of species are taken, of which approximately 2,000 fish, crustacean, mollusc, echinoderm (marine invertebrates) and aquatic plant species or species groups are reported by name in FAO statistics but 10 million tonnes are landed as unnamed marine fish. More than 5,000 species are probably harvested.
Fishing compromises genetic diversity in several ways. Fishing typically targets one or several species, eventually removing some genetic stocks from the species. Fishing is usually focused on larger fish and when these are removed, a stock’s reproductive capacity is decreased and it is prone to larger fluctuations in abundance.
Preferences for larger, valuable fish species reduce their abundance and promote abundance of other smaller species. Species diversity can be further diminished by incidental killing of non-target species such as marine mammals, sea turtles and sharks. Fishing also reduces the diversity of ecosystems and habitats.
Farming fish also challenges biodiversity and sustainability. Aquaculture utilises and affects species in different ways to fishing. In many cases cultured species are still collected from the wild at some stage in their life cycle because captive breeding has not yet been achieved. Culturing can involve growing out larvae through to fattening juveniles or taking adults for breeding. These unimproved varieties may or may not grow well or even survive capture and growout, thus wasting natural resources.
If local species are not available for culture, then another tactic is to introduce exotic species. Depending on the situation, this may be highly successful – or highly risky because the exotic species can become established invasive species, wrecking other forms of havoc on aquatic biodiversity.
Aquaculture is at a crossroads. It can continue to utilise available species sourced from the world’s waterways and oceans, or it can narrow its focus and domesticate fewer species – but not too few. The first road will place increased pressure on fisheries worldwide, as biodiversity is tapped in an indiscriminate and inefficient way. The second road, while longer and more challenging, is also the more sustainable, as the genetic resources of a smaller number of species are used to build reliable systems for domestication, aiding the preservation of species in the wild.
Taking this second road towards domestication will be highly dependent for success on international agricultural research. Without the steadying hand of research, the choices of species to domesticate may be made for us, as overfishing and inefficient aquaculture reduce biodiversity.
Hit-and-miss
So far, aquaculture has proven to be a hit-and-miss affair. Some species defy all attempts at culturing, others can be grown out after being captured and some can be raised from the larval stage. Presently, FAO reports aquaculture production from 348 different species and species groups. Less than 20 per cent of these species have been domesticated but most of those for which over one million tonnes are produced annually have been domesticated and their breeds improved.
The goal of all future aquaculture activities, and research, must be full domestication of selected species. A careful selection of species must be based on a set of comprehensive criteria. Research must be used to define, test, develop and prove criteria for selecting suitable species.
Suitable species will be those for which the lifecycle can be closed in captivity. Feed must be available and affordable and preferably from non-fish sources. The selected species must have the ability to grow to market size in reasonable time and a tolerance to confinement and handling.
Economically viable culture species require a combination of marketability and profitability. From a food security perspective, some species must be available to smallholder aquaculture producers in the developing world. Achieving this result for smallholders must also cater to issues such as space, environmental management, available finances and assets along with training and education. All of these factors need to be present in species selected for domestication.
The improvement of farm breeds to increase efficiency depends on biodiversity at species and genetic levels. The selection of species must be carried out in conjunction with the preservation of their genetic variability. To do otherwise is to limit the potential for breeding improved fish strains.
With these sorts of challenges in mind, the Australian Centre for International Agricultural Research (ACIAR) has designed and supported fisheries research since 1984. This research has a dual focus – managing wild fisheries through innovative management approaches and better utilisation of existing harvests, in concert with improved aquaculture through the development of productive and sustainable aquatic farming systems.
As an example, the WorldFish Center, in partnership with ACIAR, is applying this dual approach to sea cucumbers, focusing on viable culturing and restocking of depleted resources. This project, active in the Philippines, Vietnam and Australia, builds on past research that developed technologies for culturing 'sandfish' (Holothuria scabra) in hatcheries and for releasing in the wild. In many areas where sea cucumber has been overfished the culture technologies can be used to replenish selected sandfish populations.
In the Philippines restocking of sandfish into marine reserves is building up a critical mass of spawning adults. The research will help to speed stock recovery, generate income and conserve wild breeding stocks.
In another case, ACIAR’ support has helped in defining the basic taxonomy of the four Indo-Pacific mud crab species (Scylla spp) and developing technology for hatchery and nursery production of crablets with improved productivity in growout. Guidelines for the design of pens for farming crabs were developed. When farmers were provided with appropriate crablet species and equipment, the growth of the crablets was rapid, with relative conformity in size and a viable survival rate compared to stocking ponds with wild seedstock.
Despite these successes, aquatic biodiversity faces huge conservation challenges because much of it needs to be conserved in-situ in water bodies threatened by myriad human actions such as dams and land reclamation for ports and cities. The challenge must be addressed on several fronts – sustainable management of wild resources, developing domestication systems for selected species and strategic and integrated policy interventions.
Whichever way we look at sustaining fish production, protecting and wisely using aquatic biodiversity lies at the core and research provides many of the answers.
I gratefully acknowledge the assistance of Warren Page of ACIAR in preparing the presentation for the 2010 Crawford Fund Conference on which this article was based.
