* By Stephen Newman, Ph.D.
When I was in university in the late 1960s and early 1970’s, I was a bit adrift like so many of my peers. A war was raging and many of us had no idea what we could look forward to. I chose a major that the University of Maryland only recently had developed and found myself sitting through ecology courses. Perhaps the biggest message that I took home was that ecosystems are in a delicate balance and their complexities often masked their vulnerabilities. This balance can be all to easily disrupted with significant impacts, many of which may not become apparent until after the fact.
Post graduate school, while developing the first commercial fish vaccines, I began to learn about the then infant salmon farming industry and traveled extensively visiting operations in many countries. Flow through cage and smolt production systems were the norm and RAS was very much in its infancy. With clean water available, many problems were avoided.
In hindsight some, if not most, of the current challenges appeared to occur as a result of a rapidly growing industry that put pressure on the availability of adequate clean water resources. In the early 1990s I started focusing on shrimp farming. As with the salmon farming industry, these were early days and there were few concerns with the negative impacts of discharging wastes into the environment.
However, with more than 8 billion people on the planet today, it is apparent that we cannot continue to dump untreated or inadequately treated waste streams into the environment without seeing negative impacts. The oceans were looked upon as being impossible to damage. Now it is widely recognized this is not reality. Note that there have always been some who saw this well before it became a problem. Yet we persist in using the worlds water resources as a waste receptacle.
Humanity must become environmental stewards if we are not to exceed the carrying capacity of the environment with all of its horrific potential consequences. The evidence suggest that we are already well along this path in some areas. Imagine an ocean without fish or vast areas on land that cannot support agriculture because of polluted ground water.
This is a complex subject, and it is not my intention to offer anything but my perspective on what I see as a serious problem. There are many components to this including greenhouse gases which I will not be addressing specifically, nor will I be addressing the environmental costs of feed production and many other aspects of environmental impacts in aquaculture.
The most egregious offenders against the environment are municipalities that dump raw sewage or partially treated effluents into the local water ways, whether rivers, lakes or the oceans. They use these as dumping grounds while assuming that the vast amount of water is not something we can damage. The evidence is clear.

Eighty percent of the sewage that humans generate is dumped into rivers and oceans without any treatment. It is estimated that more than a billion gallons are dumped into rivers and oceans daily. Pollution is affecting the productivity of areas in close proximity to human population centers. The increase in cyanophyte blooms is a troubling indicator of nutrient overload and is increasing in frequency.
Given the diversity of the global aquacultural industry, accurate figures from aquaculture regarding the quantity of wastes being added to the environment are not available. While there are some NGO’s that cite figures along with impacts, these are not likely accurate reflections of the big picture.
Furthermore, some claim that aquaculture is the reason for destruction of local aquatic environments when, in my opinion and that of many others, the dumping of untreated and inadequately treated sewage is the primary cause of most of the problems. Human sewage is the real culprit.
Environmental stewardship must be a critical component of any farming practice and aquaculture is no exception. Yes, there are examples where localized damage to the environment occurs. One that is cited often is the siting of fish net pens in shallow waters where currents do not flush heavily diluted wastes away from the site.
Possible solutions to this are to use closed systems that remove the waste streams and treat them before discharging them or move the cages to areas that are not shallow and where currents act to flush these materials and dilute them.
In-situ bioremediation can also moderate the impact. Any solution will be an added cost which consumers will have to pay. Will they pay more to know that what they are eating is produced in an environmentally friendly manner? Corporate profit margins seem to be more important than environmental stewardship. Many think that consumers will choose less costly sources of protein.
Most shrimp farming is done in ponds. There are several production paradigms with the most common being dirt ponds where wastes accumulate during the production cycle. Some flush these out via water exchange, and some treat them, at least allowing them to settle, so that the water that they discharge is largely free of particulate wastes.
This does not stop chemicals, antibiotics and other smaller molecular weight material from being dumped. The accumulated solid wastes may be trucked off for addition to landfills or used to shore up berms in the ponds or allowed to accumulate to the point where the discharge ponds are no longer of utility.

There are several hundred thousand shrimp farmers globally with most in third world countries. The real money in shrimp farming is in the export market. China, the USA and the EU are the major importers. Most shrimp farmers are not corporations. The farms are small, and the farmers are often not financially secure.
In many instances, it is subsistence farming. Although when a small farmer is successful and has right connections to market a high-quality product, a fortune can be made. Typically, most farmers cannot afford or are simply unwilling to set aside a portion of their farm for ensuring that waste streams are adequately treated before discharge.
Adequate treatment is more than likely going to vary depending on what the country of productions requirements are as well as what the countries that their products end up in are. It may be that the only path requires consolidation. Shrimp (and fish) farming needs to be practiced by corporations with a diverse resource base, often vertically integrated, that can afford to ensure that the waste streams that they generate are properly managed before discharge.
There are several possible approaches. These include using high rates of water exchange to flush out these materials as they accumulate. This however reaches a point where it is simply not viable, typically because of the lack of access to clean water in the quantities needed and the costs associated with moving the water. The wastes are essentially dumped untreated into the environment which makes this an unsuitable approach towards environmental stewardship. In many areas, farms are packed so tightly that one farms influent is another’s effluent.
Biofloc is one tool that is in use. These are suspended particles of organic matter colonized by a wide range of microbes that digest this in situ. They are kept in suspension by aeration. However, the amount of aeration required in many instances to keep the particles in suspension and prevent wastes from accumulating on pond bottoms can be quite high and an undesirable stress on the animals in the ponds who must expend energy fighting currents.
Some companies will keep the biofloc and reuse it while others discharge it in waste streams. Perhaps the best approach, at a cost, is to impound the waste streams and treat them to reduce the organic loads and detoxify chemicals and other compounds of concern to reduce them to “acceptable” levels.

Environmental stewardship is not that complicated. However, determining how best to do it can be and certainly appears to be divisive. Some believe that the solution lies in banning all aquaculture operations in the misguided belief that the environmental impacts are far worse than the reality.
Arguing that pollution from aquaculture is horrifically damaging the environment without considering that the untreated wastes from human activity far outweigh any potential damage from aquaculture strikes me as biased and alarmist. Regardless, all agricultural and aquacultural farming practices should be practicing environmental stewardship. Where to start?
The first place I believe is to accept that it is an essential element of sustainability. If the wastes can be reconditioned in some manner that creates value, this is probably the best solution in the long term. The organic components of these wastes have nutritional value that can be recycled.
One possible example would be drying the material and feeding it to insects that are the source of insect meals, a potential replacement for fish meal. There are of course economic issues that will impact this. Insect meals are not at the price point where they are less costly than fish meal. This is likely to change as a burgeoning human population drives the demand for increases in seafood in their diets which can only be met via aquaculture.
If reuse is not economically viable, then collecting the wastes and treating them with aeration and microbial bioaugmentation to ensure that the nutritive elements that are being dumped are not damaging the receiving waters is a suitable approach.
This entails reducing the amount of pond area available for production, although there is nothing that stops these waste ponds from being used for growing salt tolerant plants or some aquatic animals that are marketable. Ideally, the nature of the treatment should reduce heavy metal levels, pesticides, antibiotics and degrade the feces, molts and other components of the waste stream.
The simple fact is that humanity cannot continue to use the oceans and various other bodies of waters as dumping ground for its wastes. While aquaculture may only contribute a small amount compared to direct human waste streams, environmental stewardship demands that every effort be made to lessen any source.

* Stephen G. Newman has a bachelor’s degree from the University of Maryland in Conservation and Resource Management (ecology) and a Ph.D. from the University of Miami, in Marine Microbiology. He has over 40 years of experience working within a range of topics and approaches on aquaculture such as water quality, animal health, biosecurity with special focus on shrimp and salmonids. He founded Aquaintech in 1996 and continues to be CEO of this company to the present day. It is heavily focused on providing consulting services around the world on microbial technologies and biosecurity issues. sgnewm@aqua-in-tech.com www.aqua-in-tech.com www.bioremediationaquaculture.com www.sustainablegreenaquaculture.com.