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Articles and BlogsCopyright © 2012 Fisheries Technology Associates, Inc. All rights reserved. Copying and distributing or reprinting for purposes of resale without expressed permission of the author is prohibited. January '12, Fish Farming News--Predictions do come true, aquaculture can come to the rescueby
Bill Manci About one year ago, I wrote a column about U.S. aquaculture’s current state of affairs. The U.S. was running a huge trade deficit in seafood, and we still do. But some important shifts have occurred over the past twelve months. From my perspective we have reached a tipping point of sorts. One that could—could—mean the world for U.S. aquaculture. A December, 2011, news report decried the supply of seafood in China relative to demand. “It is becoming more and more difficult to procure seafood,” says a Chinese wholesaler. The report goes on to say, “In China, it has been said that fish spring from the sea, but now depletion of fishery resources because of overfishing is taking on a touch of real possibility…The prices of seafood have been soaring wildly due to the mounting difficulty in obtaining fish in the seafood market.” In last year’s column, I talked about a fundamental shift in world economics. We were experiencing then, and still are, an economic slowdown in the U.S. that put a lid on wages and many prices. On the other hand, places like China and India are still booming—leading to increasing wages, standards of living, and prices. What does that mean for us? As I predicted, the playing field is leveling. In other words, cheap labor abroad, relative to the U.S., is becoming harder and harder to find. Globalization of markets is a great equalizer. Low production costs in one part of the world inevitably will give way (if markets are not fiddled with, open and free, and left to their own devices) to higher wages and costs at that location, which provides opportunity for everyone else to compete more effectively for the same business and sales. The rest of the world is “catching up” to the U.S. in terms of wages and costs. This move is not complete, but the handwriting is on the wall. Who would have even contemplated five or ten years ago that, for example, textile manufacturing might return to North Carolina? It is now a real possibility (so say pundits on CNBC), as is the opportunity for U.S. aquaculture producers to seriously consider selling products to the seafood-starved Chinese. In all likelihood, the higher-priced and higher-value items will find their way to China first. Cobia, amberjack, yellowtail, barramundi, grouper, trout, salmon, hybrid striped bass, and many others are all good candidates. Two Hong Kong-based businessmen are setting up shop in Maine to export at least 1 million pounds of lobster to China every year. These are all wild-caught, of course. But it gives you a sense of the possible. Another prediction: The future demand for seafood from China will be so great, that U.S. producers will finally be in a position to justify larger investments of capital and operating costs in off-shore cage systems, and freshwater recirculating aquaculture systems (RAS). In a real sense, our economic woes are making this possible. It is now time to seize the opportunity and turn the tables on, what has been, a Chinese-export juggernaut. Those days are ending, and hopefully we can see clear from a regulatory perspective to finally unleash the potential for aquaculture here in America (hello all politicians!). We are on the brink of an economic opportunity that we must not miss.
Copyright © 2011 Fisheries Technology Associates, Inc. All rights reserved. Copying and distributing or reprinting for purposes of resale without expressed permission of the author is prohibited. September '11, Fish Farming News--Romantic notion of eating wild fish must endby
Bill Manci I read the recent article in Time magazine (18 July 2011) by Bryan Walsh about aquaculture and its relationship to human nutrition and wild fish populations. Aquaculture was, AGAIN, inaccurately painted in an awkward light—as sort of a necessary evil. The author waxed poetic about people setting out into the wild and braving the elements, and about how fish are the last wild food. I certainly do not begrudge commercial fishermen their living. This romantic view of fishing is quaint and appealing. Let’s face it. As people, we have been hunting and gathering for as long as we have been around. In a real sense, it’s part of our DNA. So, I easily understand the sentiment. Now, let’s fast-forward to today, and today’s reality. Our world contains 7 billion people. We insist on making more. When Paul Erlich wrote The Population Bomb in 1968, his timing was a little off (only regional starvation during the 1970’s and ‘80’s) and we have managed the situation a bit better than he predicted (not much). But as a visionary, he didn’t do too bad a job. I have no problem with fishing as a recreational pastime. In most cases, this is a once-in-awhile event that results in incidental fish consumption. Indeed, catch-and-release fishing is becoming an increasingly popular way for us to satisfy our passion for hunting, and at the same time return the quarry relatively unharmed to the water for us to pursue another day. But I am sick to death of hearing how much better wild fish are than aquacultured fish. The facts do not support this notion and it’s simply not true. As an analogy, we are all told by health officials to be careful who we associate with as a partner. Use precautions, or even exercise abstinence. Given this context, I am amazed at people’s attitudes about fish that we hunt. In the same breath, we are told to eat more wild fish. Where have these fish been?! What have they been exposed too?! Pesticides? Heavy metals? Medical waste and other pollution? We simply do not know, or we find through analysis that these fish are indeed tainted. The romantic notion that we must eat wild fish must end. We do not know the quality of these fish, and the oceans simply cannot satisfy the large and growing demand. Fishing for the purposes of feeding the human population is unsustainable. End of story! According to most recent UNFAO statistics, total world annual consumption of all fish and shellfish is 142 million metric tons. The wild supply amounts to 90 million metric tons, with no sign of increasing anytime soon. The contribution from aquaculture is 52 million metric tons and growing rapidly. This is why aquaculture was invented—just like terrestrial agriculture. We no longer have to scour the oceans for sustenance, nor should we. We cannot afford to capture and consume every fish in the ocean simply because we can. In the end, we will still be hungry and the oceans will be empty. Eating wild fish can be dangerous, and I can cite hundreds of examples. When fish are raised in aquaculture systems, we are in much more control of the situation. We can provide feeds that are free of toxins and pollutants. In many cases, we can control the quality of the water in which the fish reside. The result is a product that is traceable, and its producers are accountable. Leave the wild fish for our child and their child to enjoy, and to continue their part as important links in our ecological continuum.
Copyright © 2011 Fisheries Technology Associates, Inc. All rights reserved. Copying and distributing or reprinting for purposes of resale without expressed permission of the author is prohibited. July '11, Fish Farming News--Aquaculture receives good news about environmental impactby
Bill Manci I received some very good news recently—news that really did not surprise me, but news that provided a sense of satisfaction that I have sought for a long time. Those of us in aquaculture have always understood the many ways in which aquaculture can help us bridge the gap between food demand and availability. We are also aware of the production efficiencies and environmental benefits that aquaculture offers over other types of agricultural production, and the role aquaculture plays in saving and preserving wild populations of fish. A new report by WorldFish Center and Conservation International confirms what we all have known for many decades. While the report, entitled “Blue Frontiers: Managing the Environmental Costs of Aquaculture,” addresses a multitude of issues related to aquaculture, three overriding themes emerge: (1) the environmental impact of aquaculture varies greatly between region or country of production, species, and production system, (2) aquaculture is more efficient and less damaging to the environment than terrestrial agriculture such as beef and pork production, and (3) fish and shellfish are and will be some of the most important sources of protein for growing urban populations in many parts of the world, particularly China and India. The growth in demand for fish and seafood is the key issue here. We now derive the majority of our fisheries products from aquaculture, which on average has grown at a rate of 8.4 percent since 1970. Without aquaculture, we would have stripped the oceans bare long ago, and the need for even more supply grows by the day. Recommendations within the report include: (1) a research focus on carp production in Asia, which is least efficient and disproportionately contributes negatively to the environment, (2) an educational focus on production systems in developing nations to improve efficiencies, (3) continuing efforts to reduce dependence on fishmeal and fish oil in aquaculture diets, (4) urge governments to promote aquaculture over other types of livestock production, (5) urge governments to promote aquaculture as a form of food security, (6) minimize energy consumption in aquaculture production, (7) locate production facilities away from mangroves, seagrass, and wooded forests and other ecosystems that sequester atmospheric carbon dioxide, and (8) encourage regulatory frameworks that support technological innovation, support the capture of environmental costs within aquaculture processes, and support monitoring and compliance. These are all important and worthwhile recommendations. They also imply that aquaculture development is a governmental responsibility. I suppose it is. But I prefer to think of it as a willingness on the part of governments to partner with the private sector. Rather than standing in the way with punitive and often overreaching regulations, governments must appreciate more fully the value of aquaculture and the imperative to encourage aquaculture development within the private sector. Certainly, aquaculture should not be left to grow in a haphazard fashion. Instead, regulatory frameworks should be transformed into a structure that takes into account environmental considerations, rational societal sensibilities (not hype or sensationalism), and reasoned and thoughtful planning for our future needs. The maturation of aquaculture over the decades is self-evident. Certification of production facilities and their products by third parties is now the norm. The aquaculture industry fully understands its role and responsibilities, and has taken adequate steps to ensure environmental sustainability as a punch list item in its siting and production protocols. Maybe the pot shots taken at us by groups purporting to be advocates for the environment will finally stop. That’s my eternal optimism shining through, but the reality is that changes in attitude toward aquaculture by naysayers will come only over a period of time. However, the report presented by WorldFish Center goes a long way to vindication for aquaculture.
Copyright © 2011 Fisheries Technology Associates, Inc. All rights reserved. Copying and distributing or reprinting for purposes of resale without expressed permission of the author is prohibited. May '11, Fish Farming News--Institute of Aquaculture is worth savingby
Bill Manci As we all know, the world economic crisis unleashed in 2008 is still with us. Governments all over the world are grappling with its effects, and in many if not most cases, are faced with massive financial deficits. I learned in March that the Institute of Aquaculture (IoA) at the University of Stirling, Scotland, is in fear of being financially and operationally gutted. The proposed budget would dismiss 36 Institute positions and, as stated in a recent letter requesting help, “would undermine IoA as the largest integrated centre for aquaculture research and teaching in Europe and severely damage its international position.” I will take the IoA staff at their word when they say there are other ways to achieve cuts and minimize the damage that so many layoffs would create. I also take as a given that, as the staff claims, budget cuts were developed with no tangible consultation from IoA. The situation in Scotland is so bad that an international request for help was issued. Who would argue that food is not one of our most basic needs—air, water, food, shelter, medical care? Additionally, there is no doubt in anyone’s mind that aquaculture is contributing and will increasingly contribute to the security of world food supplies. While I understand the “meat axe” mentality given current budget crises all over the world, it is these times in particular that we must pause as a society and be sure we do not throw the baby out with the bath water. It is human nature to resist difficult change. When times are good, budgets expand. As time passes, those benefitting from those expansions may begin to feel entitled. Certainly, no one invites the kind of cuts proposed at IoA, entitled or not. Some may argue that research of any kind should be the domain of the private sector. I do not necessarily disagree, but I also know that some research cannot be reasonably borne by private enterprise. Some research is undeniably needed for the greater good, but cannot be justified within the economic framework of most or any companies. Many types of medical and agricultural research are shining examples. This is where organizations like IoA must step in and fill a void. I have a sneaking suspicion that short-term political expediency is at least partially to blame for the situation at IoA. I suspect that decision-makers at the University of Stirling are operating under the false assumption that IoA is an easy target—that political cover is their overriding concern. They conclude that emasculating a research institute will generate the least amount of backlash and negative feedback. While political expediency may be easier for some, it often creates unforeseen (and even more tragic and nonsensical—foreseen) future consequences. In essence, it makes no sense to jeopardize our ability to feed ourselves when it is unnecessary and unwise relative to its importance in anyone’s reasonable list of priorities. Political courage is a rare commodity these days. I suggest it is time to exercise some, and do the right thing. The right thing here is to reconsider the meat axe, sit down with the IoA staff, and develop a budget that grants greater consideration of long-term consequences. As of this writing, the fate of IoA is unclear. Let’s hope that wisdom prevails and IoA is spared a fate that will most certainly mean a drastic reduction in our ability to guide our societal ship to greater security.
Copyright © 2011 Fisheries Technology Associates, Inc. All rights reserved. Copying and distributing or reprinting for purposes of resale without expressed permission of the author is prohibited. February '11, Fish Farming News--As the rest of the world “catches up,” U.S. aquaculture will flourishby
Bill Manci Back in 2004, I wrote a column about outsourcing and the fact that more and more of our fish were coming from overseas. Our economy was relatively strong at the time and the high value of the U.S. dollar meant we could buy copious amounts of foreign-made products, including finfish and shellfish. In that column, I wrote “Outsourcing holds down the prices we pay for the aquacultured products we consume. In a commodity-based economy—in other words, in an economy where price drives demand as opposed to quality or brand recognition—the group of producers or region capable of producing a product for the least cost will dominate the marketplace. Usually, price is king. In short, outsourcing keeps more of the consumers’ money in their pockets, and that’s not a bad thing.” Despite the financial crisis of 2008 which brought about severe and ongoing recession in the U.S., the world has not made a complete about-face. We still generate an enormous trade deficit in seafood. But the tide has turned in some very important ways. First, the value of the dollar has fallen significantly. This means that imports become less affordable and exports become more attractive and affordable to foreign markets. Second, average wages paid to U.S. workers have been flat or slightly falling during the last decade. Instead of more disposable income, we have the same or less income and must tighten our financial belts. Third, the standards of living in other nations and the wages they pay their workers have increased substantially. There is more opportunity for foreign markets to demand more of our goods. What we are finally seeing in this increasingly globalized economy is an unfolding process whereby much of the rest of the world is “catching up” to the U.S.—both in terms of standard of living and in terms of income and spending (mandatory and discretionary). In many ways, Americans lament this trend—our era of conspicuous consumption of cheaper foreign goods is narrowing or closing. However, for domestic aquaculture, a window of opportunity may be opening. As foreign wages rise, the cost of foreign-raised finfish and shellfish will rise. This will create a more even playing field for finfish and shellfish produced here in the U.S. A weakening of the U.S. dollar will only enhance this effect as American-produced, aquacultured finfish and shellfish become more affordable to foreign consumers. What’s even more interesting is that the U.S. has been for a long time, and will continue to be, a world center of aquaculture innovation. Despite our economic woes, The U.S. will continue to be the best incubator on earth for new ideas and ways to produce fish more efficiently. The highest quality and highest value aquacultured products will be produced here in the U.S. in highly efficient, relatively compact (i.e., more highly intensive), technically sophisticated, and environmentally friendly facilities. New species and product forms will be our strong suit. Sure, the imported commoditized products will capture their share of the market. However, we will cater to a different and more discriminating and economically affluent and knowledgeable clientele (both here and abroad) at prices that are acceptable to them and allow us to maintain reasonable or even exceptional profitability. I’ve mentioned this before, but more Americans are paying closer attention to the proximity in which their food is produced. They want to feel good about their purchases and they know that Americans will produce fish that are wholesome, healthy, and produced in ways to minimize environmental impacts and so-called carbon footprint. As we all know, our current regulatory system is one of the most stringent in the world. It’s about time that we use it to our advantage. Rather than view our current economic predicament as a liability, we should view it as an asset and be prepared to take advantage of a changing world. I predict that more and more American consumers will look inward and close to home to purchase their finfish and shellfish. The economic crystal ball is in clear focus. We simply have to read it.
Copyright © 2010 Fisheries Technology Associates, Inc. All rights reserved. Copying and distributing or reprinting for purposes of resale without expressed permission of the author is prohibited. November '10, Fish Farming News--The salmon GMO debate highlights opponents’ hypocrisyby
Bill Manci Aqua Bounty Technologies has devoted much time and treasure to the development of an Atlantic salmon (the AquAdvantage® salmon) that grows twice as fast as other Atlantic salmon. Wow! That’s very impressive and also very significant for the aquaculture industry. Bringing fish to market more quickly and more efficiently is exactly the breakthrough that could be a game-changer on many levels for salmon producers. There’s only one hitch. The new salmon is a genetically modified organism or GMO. This means that genes from other fish species have been added to the salmon’s own set of genes to create this extraordinary performance—specifically, genes from Chinook salmon and ocean pout. The modification includes a growth hormone gene from the Chinook and a promoter gene from the ocean pout. Instead of slowing its growth in cold water (which the fish are often exposed to during grow-out), the promoter gene keeps the growth hormone gene “turned on” during the entire life cycle of the modified fish. The debate over genetically modified Atlantic salmon rages on, and I decided it’s time for me to weigh in. Before I continue and by way of full disclosure, I am in no way affiliated or associated with Aqua Bounty, nor will I benefit from their success or failure. Conflicts of interest are ethically and legally hazardous and, at best, unbecoming, and I avoid them like the plague. Opponents of GMO salmon throw a vast array of half-hearted arguments at the issue and hope that some of them stick. They call them “FrankenFish”—much like deformed, hideous monsters—and insist they are a threat to the environment. I wouldn’t be so irritated by all the fuss over GMO salmon if it weren’t for the fact that the hypocrisy of the situation is staggering. The same people who would not dream of eating a GMO salmon don’t give a second thought to eating soybeans, corn, sugar, canola oil, cottonseed oil, or zucchini squash—all of which are produced as GMO to one degree or another. Indeed, 93% of the soybeans we consume in the U.S. and 86% of corn come from GMO plants. We never hear names like “FrankenCob” or read news reports about impending environmental armageddon at the hands of corn and soybean farmers. Where’s the outrage? Why the hypocrisy and inconsistency? In truth, these products as well as GMO salmon are quite safe. Here are the facts, minus the hogwash.
In short, there are no rational arguments against the production of GMO salmon—only knee-jerk comments and irrational fears based on bias, ignorance of the facts, or perceived political incorrectness. Indeed, as of this writing, Maine Senator Olympia Snowe is urging the FDA Commissioner, Dr. Margaret Hamburg, to halt the approval process for Aqua Bounty’s GMO salmon. I have great respect for Senator Snowe and her thoughtfulness, but characterizing the proceeding as inadequate and in need of a new review protocol is unfortunate and wholly unsupported by the facts and the rigors of the existing process. Additionally, her stance is a disservice to the aquaculturists and other constituents of her state who could benefit greatly from this technology. I can only surmise that she hopes to bury the approval process in a mountain of new bureaucratic red tape. The FDA process is proceeding cautiously and with thoughtful participation from experts who can impartially assess risks and benefits and apply existing law. With oversight, safeguards, and precautions, this new technology can be implemented safely and effectively and to the great benefit of the consuming public. Human progress and innovation is often met with skepticism, doubt, and even fear. While these may be “normal” human reactions, we need to put them aside and embrace this new technology until we have sound reasons based in scientific facts to consider alternatives.
Copyright © 2010 Fisheries Technology Associates, Inc. All rights reserved. Copying and distributing or reprinting for purposes of resale without expressed permission of the author is prohibited. August '10, Fish Farming News--Aquaculture taking the correct steps to repair imageby
Bill Manci We do a great job of raising fish. However, our prowess in public relations is, shall we say, somewhat lacking. There aren’t too many segments of the economy where so-called negative marketing is as alive and well. This is where you actively discourage the purchase and consumption of a product. With the exceptions of the political arena, drug use and drunk driving (e.g., the “Meth...not even once” campaign), and Mac versus PC, negative marketing is a fairly new phenomenon. Aquaculture has been thrown into this strange and eclectic mix by professed environmentalists. These are the people who want us to eat wild salmon, to the exclusion of farmed salmon, until all the wild salmon are gone. I guess we won’t have to worry about the wild salmon at that point. OK, I’ll stop the sarcasm...for now. Despite our good intentions, we are pummeled almost continuously in the media, including print, broadcast, and blogosphere. Much to its credit, the aquaculture industry is now responding more vigorously. There used to be a head-in-the-sand approach or attitude about aquaculture’s perceived environmental missteps. But not anymore. I say “perceived” because, for the most part, these were perceptions or bald-faced falsehoods. Aquaculture has always been about environmental responsibility, and never claimed to be perfect. But, perception often is reality. Those warts and imperfections have since become a bane of our existence. After several decades being labeled as an “infant,” and then blamed for pollution, genetic chaos, and proliferation of disease—much like the teenager with the messy room and lifestyle—aquaculture has emerged as a more responsible and savvy adult, and less as an easy target. A plethora of groups have now come forth to satisfy the public’s craving for third-party certification and verification of production standards, product quality, and long-term environmental sustainability. There is now a race between a whole gaggle of organizations to take the lead in prestige and authority relative to facility and product certification. Who will become the Good Housekeeping or Underwriters Laboratories of aquaculture? In our haste to satisfy the critics, we’ve almost gone too far. We run the risk of confusing the public with all of the new certifiers who are now emerging. Indeed, there tends to be significant disparity in standards from one organization to another. For example, what passes as organic by one group is not categorized similarly by another. Granted, some of this disparity is a result of inconsistent laws or regulations between countries. But sometimes the organizations appear to be engaged in a game of one-upmanship, in an appeal to the most strident members of their interest group or client base. Undoubtedly, there will be a shake-out and much of this activity will calm down over time. Only a select few of these certifiers will be accepted by the public and the most credible and trustworthy will thrive. Quite frankly, I understand the rush to the lead. There is a lot at stake—income in particular. The certifiers who emerge as the preeminent organizations will collect the lion’s share of the work and dollars. It’s the new growth segment within our industry. Mark my words. As fish producers (live or processed) and regardless of the species you raise (freshwater or saltwater), you will eventually feel compelled by your customers to accept oversight and certification by one or more of these groups. Without a doubt, your customers will demand it, and you will be unable—either practically or literally—to sell fish without it. Certification will cost money. So, until the shake-out is complete, choose a certifier carefully. In the future, you can use the certifier to your advantage. Think of them as “your people.” That’s their value. If there’s a problem with your product or it’s being questioned, your certifier will be on the hook to help you solve it or respond. If you follow their standards, you can simply say “talk to my people.”
Copyright © 2010 Fisheries Technology Associates, Inc. All rights reserved. Copying and distributing or reprinting for purposes of resale without expressed permission of the author is prohibited. May '10, Fish Farming News--Fish oil replacement: palm oil may not be the answerby
Bill Manci Some soul-searching may be required as we look for new and better ways to replace fish oil in fish feeds. Recent research from Malaysia makes me a bit nervous, and more than a bit concerned about our priorities. I read an article that suggests using palm oil as a substitute for fish oil in fish diets. The rationale for this change is four-pronged. First, fish oil supplies are finite and increasingly expensive as overall demand grows. We must therefore find substitutes and alternatives that are more sustainable and economically viable. Second, palm oil supply is relatively abundant, and its production is supported by a vast and growing infrastructure. More palm oil is produced in the world than soybean oil! Third, palm oil is much more chemically stable over time than fish oil. At 30 weeks, frozen tilapia fillets were dramatically less rancid and—not surprisingly—tasted better than fillets from fish oil-fed tilapia. Finally, palm oil appears to work well technically as a replacement for fish oil. The Malaysian research suggests that palm-based feeds produce tilapia just as quickly and efficiently. The pluses here are very attractive, particularly for fillets that are frozen for up to 30 weeks. As frozen fish fillets age, fats within the fillets oxidize and become rancid—a serious problem in taste and nutrition. As much as 96 percent of this oxidation can be eliminated by using palm oil as a replacement. All of this would be great, expect for one “small” point. Unlike fish oil, palm oil is a very poor source of heart-healthy omega-3 fatty acids and an abundant source of artery-clogging saturated fatty acids. To be specific, tilapia fed a palm oil diet contain less than a third of the omega-3s as compared to fish oil-fed tilapia, and significantly higher levels of saturated fats. Here is my concern. We are already beaten up-side the head repeatedly by our detractors who claim that aquacultured fish are less nutritious than wild-caught alternatives (never mind their environmental arguments!). Do we really want to add fuel to that fire by degrading the nutritional quality of our fish by replacing fish oil with palm oil? NO! Our critics will have a field day! I can see it now. They write, “Not only have these conscienceless aquaculturists reduced the omega-3 content, but they have dramatically increased the saturated fat content too!” There is a socio-economic consideration here as well. I am convinced that fish producers whose sole purpose is to produce the least expensive and most freezer-stable fish fillets possible will adopt this new nutritional approach. When this happens, their products will be cheap to buy and therefore most attractive to those people in the lowest economic strata of our society. Do you see where I’m heading with this? We will be accused of profiteering, and exploiting the most economically disadvantaged of our society through products that are not only less nutritious, but actually degrade their health. Do we want the nutritional equivalent of a McDonald’s label? I don’t think so. At the same time, those consumers who can afford higher quality will continue to buy fresh fish fillets only. In all likelihood, the producers of these never-frozen fillets will avoid the palm oil diets (unless they want to practice business suicide) and produce nutritionally superior fillets by using healthier fish oil alternatives. Let’s not give aquaculture naysayers more fodder for their cannons! Let’s not be accused of socio-economic injustice. Instead, let’s focus on fish oil alternatives that avoid these pitfalls. We already know that fish oil alternatives based on marine algae and select terrestrial plants will provide many of the technical and economic benefits without the downside. They are on the market today and available to feed manufacturers. In the meantime, I challenge the research community to develop better shelf-life solutions. Unless there is a magic remedy for high levels of saturated fats and low omega-3s in palm oil, we must avoid the temptation and its use. Clearly, this is a case where the benefits do not outweigh the costs.
Copyright © 2010 Fisheries Technology Associates, Inc. All rights reserved. Copying and distributing or reprinting for purposes of resale without expressed permission of the author is prohibited. January '10, Fish Farming News--Small-scale aquaculture begins to grow “green shoots”by
Bill Manci By its very nature and almost by definition, aquaculture has always been about innovation. It’s been around far less time than terrestrial agriculture so there are more things to try and new ways to approach recently spawned ideas. In the not-too-distant past, small-scale or backyard aquaculture seemed to be ahead of its time. It was talked and written about a lot, but many people (certainly not all) dismissed it as impractical or “on the fringe.” With the advent of the Green Revolution, small-scale aquaculture is rapidly gaining in popularity. For many, it’s becoming less acceptable to buy food from, and patronize, producers halfway around the world. The so-called carbon footprint to transport those goods—the amount of energy required and carbon dioxide emitted in the process—is unacceptably high. Additionally, we are becoming increasingly skeptical that conventional farms can provide us with healthy and high-quality produce. Instead, carbon-conscious consumers want to rely more on locally grown food. In many ways, that’s a worthy goal. They also want to feel good about the food they eat and crave more of a connection and responsibility for its production and quality—hence, the backyard boom. The problem is that most of us live in cities. Local politicians in many locales are getting a message from their constituents that what was once old is new again. More and more people want their food grown locally. As an example, I live in a city—Fort Collins, Colorado—that allows the possession and maintenance of a maximum of six hens (no roosters—too much noise) within the city limits. This allows people to own laying hens for egg production. As the familiar saying goes, some restrictions apply. Some cities are considering or have already granted similar leniency for small-scale aquaculture. A small, backyard greenhouse can be the perfect location for a recirculating aquaculture system and adjacent wastewater-supported plant production. While the feasibility of this concept is very much predicated on a careful case-by-case assessment, the overall practicality is still questionable, just as it was many decades ago. By almost any measure, small production operations are less efficient than larger operations that can take advantage of economies of scale. The real cost of small-scale production is almost always much higher, particularly when labor costs are assessed and included in an objective way. Here is a situation where, I believe, we can have our cake and eat it too. I have become very much an advocate for aquaculture cooperatives. Just as other segments of agriculture have had success with cooperatives, we can have success here too—particularly as the concept might apply to small-scale aquaculture. When small-scale producers band together to form a cooperative, the whole becomes greater than the sum of the parts. Here are a few of the advantages. · Members can receive significant discounts on feed because it is purchased in quantities that would otherwise not be possible. · The cooperative can supply fingerling fish to its members and supply them reliably and at stable and reasonable prices. · The cooperative can act as a clearinghouse for market-size fish and negotiate optimum prices for its members. · Members can focus on production and worry less about supplies of small fish and markets for large fish. · The cooperative can be a source of technical expertise, advice, and other support at reduced cost or no cost. · Members necessarily participate in the profits accumulated by the cooperative, which can be an important additional source of member income. Please do understand that cooperatives are not a panacea. A cooperative is a business and must be run like one, and by people who have the discipline to make it succeed. Specific regulations apply to cooperatives so the relationship must not be entered into lightly. Experienced legal help is required to form a cooperative and manage it correctly. Agricultural cooperatives have worked well for many decades. If small-scale aquaculture and local food production are your cup of tea, consider membership in a cooperative or forming a cooperative to minimize your technical risk and maximize your financial return.
Copyright © 2011 Fisheries Technology Associates, Inc. All rights reserved. Copying and distributing or reprinting for purposes of resale without expressed permission of the author is prohibited. Aquaculture Blog--Water monitoring systems gain acceptance, manufacturers improve reliabilityby
Bill Manci Fish farming is like no other form of agriculture. By law across the U.S., aquaculture falls under the same umbrella as dirt farming and ranching. But the aquaculture environment could not be more different than all terrestrial forms of agriculture. When do corn farmers ever worry about oxygen concentrations around their plants? Never. When do ranchers ponder carbon dioxide levels around their cattle or sheep? Never. When does a 10-degree swing in temperature change the growth profile of their animals or row crops? Relatively rarely. When do all of these environmental factors come into play for fish farmers? Every single day. The production environment is a major reason why aquaculture can be so challenging. From minute to minute, dissolved oxygen concentration can play an enormous role in the well-being of fish and shellfish, and in more severe circumstances can be the difference between life and death. Over the years, fish farmers have come to appreciate the importance of the production environment and its sometimes tenuous nature. Depending on the circumstances, water quality can turn on a dime. A focus of any fish farm manager or employee must be water quality. This job can be time-consuming and labor-intensive, particularly if large numbers of ponds, tanks, or pens are involved. Managing all of the data collected during the regular course of a production cycle can be challenging as well, not to mention how those data are used to make informed decisions on a timely basis. For many years—indeed decades in most cases—a group of companies has recognized the importance of water quality testing and monitoring, and has made it their goal to streamline the process and deliver accurate and reliable results in a cost-effective manner. With other smaller players in tow, a group of seven companies stands out as the worldwide leaders in water testing and monitoring for aquaculture and other similar applications. They are OxyGuard International (Denmark), YSI (Yellow Springs, OH), Aanderaa Data Instruments (Norway), In-Situ (Fort Collins, CO), Hanna Instruments (Woonsocket, RI), Hach Company (Loveland, CO), and Reliant Water Technologies (New Orleans, LA). Almost without exception, each of these companies had their beginnings in other water testing fields such as domestic water supply and wastewater treatment, oil and gas, or some other related field. As aquaculture grew in size and scope, each company understood where aquaculture was headed, and began to develop solutions to the problems encountered by aquaculture producers. Direct testing of water quality factors such as temperature, oxygen, and pH with single, manually operated probes or sondes (multi-sensor probes) spearheaded the development process. Results when using these instruments were available in seconds. This was a significant advancement beyond chemical test kits that were tedious and often required more than 5 minutes to develop results, not to mention the cost of reagent chemicals that were consumed in the process. The first few generations of oxygen probes were based on polarographic membrane technology. Again, the advancements were significant, but not without some drawbacks, including a requirement for water to move past the probe during testing, sometimes unstable calibration, and membrane replacement on a relatively regular basis within harsh aquaculture environments. Another leap forward in oxygen probe technology was achieved when some developers moved to galvanic electrochemical probes and optical probes. The optical approach eliminated the requirement for water to move past the end of the probe and, in many cases, improved stability of measurements over time. Galvanic electrochemical probes continue to require water movement past the probe for accurate and reliable results, but are very rugged and stable over time and tend to require less maintenance. Today, in the minds of many, optical probes and galvanic electrochemical probes represent state-of-the-art in oxygen measurement. Both hold prominent positions within the industry. Polarographic technology is still in wide use as well, particularly with hand-held devices used for spot checking. For many fish farmers, accurate, reliable, and worry-free automated water quality monitoring—collecting good data over long periods of time, not just spot checks by people—is the Holy Grail of aquaculture, and this was the next challenge for equipment manufacturers. Large aquaculture facilities in particular, or facilities that grow fish at high densities, must monitor and control oxygen on a 24/7 basis, or during key times of the day (e.g., at night in outdoor ponds). Accomplishing this task manually can require personnel dedicated to that task, or large numbers of people with multiple tasks, or both. In either case, employing people can be expensive. Here is where water monitoring systems come into play. When you mate oxygen probes and sondes and other water quality measurement devices with controllers that collect and manage data and automatically activate aeration equipment or alarms at appropriate times, you have a system that, on paper, is a dream come true. Let’s briefly look at what each of the seven leading companies has to offer: OxyGuard International At their founding in Denmark in 1987, catering to the aquaculture industry was a primary objective of this company. OxyGuard offers a line of hand-held measurement instruments for manual data collection, as well as monitoring, controlling, and data logging devices for automated data collection, aerator control, and data storage. The Commander (unlimited number of probes), OxyGuard 8 (8 probes), and OxyGuard Multilog (data logging and display) fill the needs for a wide range of facilities. According to company spokesperson Charlotte Ravnsborg, “The company philosophy is to provide no-nonsense measuring and monitoring equipment—equipment that does exactly what is needed with a minimum of maintenance and bother.” YSI Yellow Springs, Ohio, is the home of YSI and has been for the past 63 years. During that time YSI has played a major role in the water and wastewater industries as well as aquaculture. According to Tim Grooms, Product Manager for YSI, company growth in aquaculture is at or above overall growth of the industry. YSI has a line of hand-held and automated instruments for measurement of oxygen (featuring their optical probe), conductivity, temperature, pH, ORP, salinity and others. The 5200A system is specifically designed to handle all of these parameters and control aerators, feeders, and other equipment such as alarms. The 5400 system expands on that capability to handle up to four sets of probes and other inputs. Aanderaa Data Instruments (AADI) This Norwegian company began catering to the oil and gas and environmental research markets 40 years ago. More recently, they recognized the growth of aquaculture, particularly in Norway, and developed systems specifically designed for those environments. AADI instruments measure and monitor oxygen, water current speed and direction, temperature, and conductivity/salinity. They feature the Oxygen Optode optical sensor for use with their Oxyview Program to measure and record data within multiple aquaculture systems. In-Situ In-Situ is a Colorado company with roots in water and wastewater management since 1976. They entered the aquaculture realm more recently with an innovative product called the Wireless Aquaculture System. This floating buoy device monitors and controls oxygen and aeration equipment, is based on their RDO PRO optical probe oxygen sensor, and wirelessly relays oxygen and temperature data back to a central receiver and aeration controller. The wireless buoy approach is relatively unique in the marketplace, is conceptually elegant, and popular with customers. Hanna Instruments Hanna Instruments is an Italian company with a 25-year operating history in the U.S. They do a lot of business in Europe and focus on the mariculture sector. According to Market Manager Jessica Hoagland, the company offers the rugged and easy-to-use HI8410 Dissolved Oxygen Controller. This device uses a galvanic electrochemical probe, and can be used to activate and deactivate aeration equipment. They also offer their very new HI9829 system, which measures and records (no control capability) a wide variety of data including dissolved oxygen, pH, ORP, salinity, turbidity, temperature, and many others for up to 30 days. Hoagland stressed that their prices are very competitive and, as a privately owned company, take great pride in their customer service. Hach Company Another Colorado company, Hach, has been in the process instrumentation business for more than 60 years. Within the past 10 years, the Hach aquaculture business segment has grown very rapidly—at a rate of 20-30 percent per year or more—as they have moved into aquaculture environmental monitoring and control, and claims to be acquiring market share from some of the competition. According to Jeff Allen, Regional Sales Manager within the U.S. Pacific Northwest, their fourth generation optical oxygen probe is “rock solid,” with no accuracy or reliability issues. Mated to their sc200 and sc1000 controllers and other probes, oxygen as well as other water quality parameters can be measured and monitored. Reliant Water Technologies The Royce 9300 Pond Monitoring System is the flagship aquaculture product of this company. It is based on a galvanic electrochemical oxygen probe and can be used to control aeration equipment or send alarms to computers or cell phones. The company caters primarily to the U.S. catfish industry, but also sells to striped bass facilities, and to shrimp and eel production facilities in Asia, Europe, and South America. Company president Jim Dartez is adamant about his product’s accuracy and reliability, stating his probe sensors will last up to 5 years with proper maintenance, and require calibration as little as once per year. Monitoring and control systems are not for everyone—particularly small operations with already manageable data collection requirements. Larger facilities with mounting labor costs should take a closer look. While claims of accurate and reliable operation by manufacturers are encouraging, only time can convince many aquaculture facility managers and owners that these monitoring systems can deliver their promises. “How do I sleep at night and rely on and trust machines when so many fish and so much money are at stake?” is a question expressed by many facility managers. Most assuredly, these monitoring systems must be maintained according to the manufactures recommended protocols and procedures. No one is saying otherwise. Anyone lulled into thinking these systems will function indefinitely without maintenance or attention will be sadly mistaken. The aquaculture environment is harsh and unforgiving. However, under appropriate and diligent maintenance, a strategy of “supervised automation” (i.e., manpower efficiency, always with an eye to stock safety) can go a long way to substantially reducing labor costs, and increasing economic competitiveness and profitability. As the technology continues to improve, as well as experience by management with the technology, comfort levels and trust will continue to rise. Without a doubt, we will see more of this equipment in place as we move into the future.
Copyright © 2005 Fisheries Technology Associates, Inc. All rights reserved. Copying and distributing or reprinting for purposes of resale without expressed permission of the author is prohibited. Aquaculture Blog--Worried about eating salmon? Think againby
Bill Manci With all the dire warnings about PCBs and other toxins in farmed and wild salmon, you’d think people would be dropping dead right and left. Instead, people are heeding the message that salmon tastes good and is good for you—especially your heart and the rest of your cardiovascular system. Last year a researcher named Ron Hites and his colleagues published an article in the prestigious journal Science. His research was sponsored by the Pew Charitable Trusts. This article created a media sensation, claiming that farmed-raised salmon contained higher levels of PCBs than their wild counterparts. Indeed, wild salmon are regularly cited as containing high levels of PCBs and other toxins as well. While this entire furor makes for great headlines, the reality of the situation is quite different. Ron Hardy, a Professor at the University of Idaho took a close look at the claims presented in the Hite study and drew some very different conclusions. In a recent article of his own, Hardy noted the following: “My opinion of the study was similar to that of many of its critics. The consensus was that (there) were a number of points that seemed flawed…While there was little concern over the analytical accuracy of the contaminant values…a great deal of concern was expressed over the selection of samples…At the time the samples were purchased, there was no country-of-origin labeling requirement. Purchases were identified by origin based on what the buyer was told by the seller.” Hardy went on to say, “A second, more serious concern was the relatively small sample of wild salmon and the species of wild salmon that constituted the sample.” In other words, all wild salmon are not created equal. They have different food preferences and, as a result, may expose themselves to varying levels of contamination, based on where they eat along the so-called food chain. Additionally, contamination in wild salmon can vary by region. Near-shore salmon, for example those found in Puget Sound, are more contaminated than those in the Pacific Ocean or Gulf of Alaska. The final nail in the coffin of the Hites study comes when we examine our contaminant exposure not only from salmon, but from other food sources as well. Hardy notes, “For example, intake of beef in 2002 was 144 pounds per person in the U.S., compared to 15.6 pounds of fish and shellfish. Salmon intake in 2003 was 2.22 pounds per person…When total annual PCB intake is calculated based upon average consumption of various foods, the comparisons are stunning. Per capita PCB intake from beef is 2401 ppb, compared to 30 ppb for farmed salmon. Milk contributes 716 ppb per capita…if one uses Hite’s values for (farmed) Chilean salmon, for example, per capita PCB intake drops by 50% for farmed salmon. If American doubled their intake of farmed salmon, the contribution of consumption on total yearly PCB intake would still be 40-80 times less than the amount for beef.” Hardy concludes, “No matter how the data are calculated and no matter who’s PCB values for salmon are used, the amount of PCBs contributed to the diet from farmed or most wild salmon is truly insignificant in the context of overall PCB intake of the average American.” Where are the headlines about contaminated and deadly beef or milk? We don’t see them. Clearly, salmon (specifically farmed salmon) have been, quite unfairly, singled out by the Pew Charitable Trusts. This kind of biased and jaundiced approach to science serves no useful purpose, and only undermines public confidence in the scientific method of investigation. The bottom line here is simple: the benefits of eating salmon, farmed or wild, and their beneficial omega-3 fats far outweigh the risks to your health if you don’t consume generous amounts on a regular basis. Those individuals with marginal health (i.e., diabetes, heart disease, stroke, etc.) actually stand to gain the most. You may view Dr. Hardy’s complete article by navigating to: http://www.ftai.com/articles/Farmed%20Salmon%20Contam%20Hardy.pdf
Copyright © 2005 Fisheries Technology Associates, Inc. All rights reserved. Copying and distributing or reprinting for purposes of resale without expressed permission of the author is prohibited. Aquaculture Blog--Aquacultured versus wild fish in a healthy dietby
Bill Manci Aquaculture, the production and husbandry of aquatic plants and animals in controlled environments, also called fish farming, is coming of age. First applied by the Chinese over 2,000 years ago, aquaculture has enjoyed an enormous increase in its practice and acceptance. Since the 1960s when aquaculture was a cottage industry, this agricultural pursuit has grown worldwide from 10 million metric tons of production in 1984 to 38 million metric tons in 1998 (1). During the same time period because of overfishing, many wild fish populations crashed and have few, if any, prospects for full recovery (2). By the year 2030, aquaculture will account for more than 50% of all fisheries products consumed in the world (1). By other agricultural standards such as terrestrial crop production or ranching, commercial aquaculture is still developing. The aquaculture industry has not fully achieved its stated goals to provide products that make the best use of available resources and are as wholesome and nutritionally appropriate for the consumer as possible, but has made great strides toward them (1). As a consumer there are at least five nutritional issues that should be considered before choosing between farmed and wild fish: 1) omega-3 fatty acid content, 2) organic residues such as PCBs and others, 3) heavy metal contamination, 4) synthetic carotenoids, and 5) residual antibiotics. Clearly cost is an important factor for all consumers, and environmental considerations may come into play for others. To date, virtually all studies of farmed versus wild species show a slight reduction in the ratio (which is different than amount per serving) of omega-3 fatty acids to other fatty acids present within fisheries products (3, 4). With that in mind, there is no doubt that farmed fisheries products of all kinds contain generous amounts of omega-3 fatty acids. Indeed, for example, because farmed Atlantic salmon and rainbow trout contain a higher percentage of total fatty acids than their wild counterparts, the farmed varieties actually contain more grams of omega-3 fatty acids per serving (3, 4). Today steps are being taken by shrimp feed and fish feed manufacturers to rectify any perceived or actual disparity between omega-3 levels in farm-raised and wild fish and shellfish. Recent research has shown that late-stage feeding with feeds containing high concentrations of omega-3 or linseed oil allows the receiving muscle tissues to quickly "catch up" (5, 6). The result is a farmed product that, overall, requires less omega-3 in its diet over its lifetime, and an omega-3 concentration in the tissue at harvest that is on par with or higher than wild product (6). This strategy will help to minimize the amount of expensive fish meals and fish oils used by the aquaculture industry, will still provide us with abundant amounts of omega-3 fatty acids in our diet, and spare valuable wild populations of fish and shellfish from unnecessary and destructive over-harvest. Many within the aquaculture industry understand and appreciate this issue, and are taking steps now to correct real and perceived disparities. When sited properly on land or at sea, aquaculture operations provide the kind of relative isolation from contaminants that is often not possible in the wild. However, some salmon net-pen operations are exceptions, and may have experienced contamination from an unlikely source—fish feed. Supposedly, in Europe and to a lesser extent in the Americas, feed contaminated with PCBs and other organic compounds was fed to aquacultured salmon and produced unacceptable residues in fish (7)—an issue that has commanded attention. While some express concern, others view the data with skepticism or interpret them much differently (8, 9). In fact, one analysis reexamined the data and determined that the PCB threat is low, and the threat from beef is actually 40-80 times higher than salmon (9). Heavy metals such as mercury and cadmium have been discovered in both aquacultured and wild salmon, with higher or lower concentrations found in aquacultured or wild fish by some researchers than others (10, 11, 12). As a result of the ecological process of bioaccumulation, other large “top-predator” fishes such as wild tuna also tend to harbor elevated levels of mercury (13, 14). Some people wonder about the new labeling seen at fish counters proclaiming “Color Added,” the purpose of this labeling, and the potential effects on human health. While these labels seem to imply that colors or dyes are somehow injected or added directly to fish, this is not the case. Natural carotenoid pigments (astaxanthin and canthaxanthin; similar to vitamin A) are added to fish feeds which impart color to fish flesh. These pigments are extracted from algae, yeast, plants, crustaceans, or synthesized from beta-carotene precursors. Indeed, astaxanthin is the primary carotenoid pigment found in wild salmon. Contrary to some reports designed to cast aquacultured fish as unsafe and unhealthy, uncolored fish flesh is white, not gray, and these pigments are extremely safe at levels normally consumed by people (15). Pollution or other environmental damage is an often-heard complaint about aquaculture (16)—in particular, ocean-based salmon production facilities that discharge metabolic wastes to the environment. These claims are controversial and disputed by others (17). Large salmon net pens systems are arrayed at the surface or anchored below the surface and confine stocks to a defined space. In the past, producers relied solely on currents and dilution to carry fish wastes from the vicinity. Today’s new net-pen technologies incorporate waste recovery, including land application and composting of dewatered, solid wastes. Turning liabilities into assets and “Best Environmental Practice” management strategy are the new philosophies. The same is true for land-based, freshwater operations, where wastewater from fish tanks is directed into plant-producing greenhouses—a process now dubbed aquaponics. Other issues include the use of antibiotics to preserve fish health. Unlike terrestrial cattle production, antibiotics are used only to treat disease outbreaks. Only approved antibiotics are used, and fish stocks are withdrawn from their treatment for specified periods of time before slaughter. Despite withdrawal, some antibiotics may persist in fish tissues (18), or may spill over to nearby environments during the treatment process (19). For these reasons aquaculturists are developing and currently using relatively benign substances that stimulate fish immune systems such as beta-glucans, stabilized forms of vitamin C, probiotic bacteria, and refined management strategies to reduce the use of antibiotics (20). Aquaculture was born out of a desire to stem the tide of overfishing and gain more control over our collective health and nutritional future. Regardless of your choice to eat aquacultured fish or wild fish, your decision involves some associated risk and implications for our world and its environments, particularly with regard to salmon and other predatory species that are widely produced and consumed. If you are concerned about pesticides, heavy metals, or antibiotic residues in your diet, salmon (farmed or wild) may not be the choice for you. There are many alternatives (farmed or wild) that may suit you better. You may avoid large predatory fishes such as salmon and tuna, and opt for herbivorous species or those lower on the so-called ecological food chain such as shrimp, tilapia, and catfish, or top predators produced in land-based systems such as hybrid striped bass and rainbow trout. By most accounts, fish are our best sources of the omega-3 fatty acids DHA and EPA that we require in our diets. Totally eliminating fish from your diet could lead to health consequences that far outweigh the alternatives. References 1. Tidwell
JH, Allan GL. Fish as food: aquaculture's contribution. Ecological and economic
impacts and contributions of fish farming and capture fisheries. EMBO Rep. 2001
Nov;2(11):958-63. 2. United
Nations Food and Agriculture Organization. The state of world fisheries
and aquaculture. 2004. 3. Hardy RW. Farmed fish and omega-3 fatty acids. Aquaculture Magazine. 2003; 29(2):63-65. 4. Cahu C,
Salen P, de Lorgeril M. Farmed and wild fish in the prevention of cardiovascular
diseases: assessing possible differences in lipid nutritional values. Nutr Metab
Cardiovasc Dis. 2004 Feb;14(1):34-41. 5. Bell JG,
Henderson RJ, Tocher DR, Sargent JR. Replacement of dietary fish oil with
increasing levels of linseed oil: modification of flesh fatty acid compositions
in Atlantic salmon (Salmo salar) using a fish oil
finishing diet. Lipids. 2004 Mar;39(3):223-32. 6. Hardy RW. Conflict ahead; can we reduce fish oil use? Aquaculture Magazine. 2003; 29(6):44-48. 7. Hites RA, Foran JA, Carpenter DO, Hamilton MC, Knuth BA, Schwager SJ.Global assessment of organic contaminants in farmed salmon. Science. 2004 Jan 9;303(5655):226-9. 8.
BC Salmon Farmers Association.
Medical, health and
food safety experts advise reading past the headlines in the new news about
farmed salmon. 2004. 9. Hardy RW. Contaminants in salmon: a follow-up. Aquaculture Magazine. 2005; 31(2):43-45. http://www.ftai.com/articles/Farmed%20Salmon%20Contam%20Hardy.pdf 10. Easton MD, Luszniak
D, Von der GE. Preliminary examination of contaminant loadings in farmed
salmon, wild salmon and commercial salmon feed. Chemosphere. 2002
Feb;46(7):1053-74. 11. Knowles TG,
Farrington D, Kestin SC. Mercury in UK imported fish and shellfish and UK-farmed
fish and their products. Food Addit Contam. 2003 Sep;20(9):813-8. 12. Foran JA, Hites RA,
Carpenter DO, Hamilton MC, Mathews-Amos A, Schwager SJ. A survey of metals in
tissues of farmed Atlantic and wild Pacific salmon.
Environ Toxicol Chem. 2004 Sep;23(9):2108-10. 13. Bender M. Canned
tuna riskier than previously suspected. Mercury Policy Project. 2003. 14. U.S. Environmental
Protection Agency. Fish and wildlife advisory news. 2003. 15. Hardy RW. “Color added” labeling and carotenoid pigments in salmon feed. Aquaculture Magazine. 2005; 31(1):25-30. 16. Naylor RL, Goldburg
RJ, Primavera JH, Kautsky N, Beveridge MC, Clay J, Folke C, Lubchenco J, Mooney
H, Troell M. Effect of aquaculture on world fish supplies. Nature. 2000 Jun
29;405(6790):1017-24. 17. Tidwell JH, Allan
GL. Fish as food: aquaculture's contribution. Ecological and economic impacts
and contributions of fish farming and capture fisheries. EMBO Rep. 2001
Nov;2(11):958-63. 18. Lucchetti D,
Fabrizi L, Guandalini E, Podesta E, Marvasi L, Zaghini A, Coni E. Long depletion
time of enrofloxacin in rainbow trout (Oncorhynchus mykiss). Antimicrob Agents
Chemother. 2004 Oct;48(10):3912-7. 19. Rigos G, Nengas I, Alexis M, Troisi GM. Potential drug (oxytetracycline and oxolinic acid) pollution from Mediterranean sparid fish farms. Aquat Toxicol. 2004 Aug 25;69(3):281-8. 20. Gannam AL. Immunostimulants in fish diets. Journal of Applied Aquaculture. 1999; 9(4):53-89.
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