FREQUENTLY ASKED QUESTIONS
What is a gillnet and how is it used?
Gill nets are walls of netting which may be set at or below the surface, on the seabed, or at any depth in between. Gill netting is probably the oldest form of net fishing, having been in use for thousands of years. True gill nets catch fish that attempt to swim through the net, which are caught if they are of a size large enough to allow the head to pass through the meshes but not the rest of the body. The fish then becomes entangled by the gills as it attempts to back out of the net. The mesh size used depends upon the species and size range being targeted.
What is a cod-end?
The cod-end is the back portion of a trawl net resembling a bag and is responsible for retaining the fish caught during trawling. The mesh size of the cod-end determines the selectivity of the net or what sized fish are retained during fishing. Fisheries managers regulate the minimum mesh size of the cod-end mesh to reduce or eliminate the catch of undersized fish.
Is trawl fishing bad for the environment?
Trawl fishing, or dragging, has undergone many changes in the last quarter century. Negative impacts to the environment may include damage to bottom dwelling (benthic) animals and plants, and the waste of animals that are either unmarketable or illegal to retain. However, modern gear, materials, practices and management have gone a long way in reducing the catch of unwanted species and the environmental damage caused by trawl fishing. For example, larger mesh sizes and improved net shapes allow many more fish to escape the trawl before they are brought to the surface, and designs exist specifically to touch the bottom much less than they have in the past. Overall, trawling has benefited strongly in recent years from fishermen and scientists working together, to reduce the negative impacts of fishing, while still providing the market with quality seafood in a responsible and profitable manner.
What is a dredge and what do fishermen catch with them?
Dredging is used for harvesting bivalve molluscs such as oysters, clams and scallops from the seabed. A dredge is a metal framed basket with a bottom of connected iron rings or wire netting called a chain belly. The lower edge of the frame has a raking bar, with or without teeth, depending upon the species targeted. The catch is lifted off the seabed or out of the sea by the raking (or teeth) bar and passes back into the basket or bag. Depending on the size of the boat and the depth of water fished the number of dredges or ‘bags’ may vary from a single dredge towed behind the vessel to from 5 to 10 or more dredges per side. Dredges are generally attached to a towing bar and one is operated from each side of the vessel simultaneously.
What is purse seining?
This is the general name given to the method of encircling a school of fish with a large wall of net. The net is then drawn together underneath the fish (pursed) so that they are completely surrounded. It is one of the most high volume methods of fishing and aims to capture large, dense shoals of mobile fish such as tuna, mackerel and herring.
What is a demersal otter trawl?
The demersal or bottom trawl is a large, usually cone-shaped net, which is towed across the seabed. The forward part of the net – the ‘wings’ – is kept open laterally by otter boards or doors. Fish are herded between the boards and along the spreader wires or sweeps, into the mouth of the trawl where they swim until exhausted. They then drift back through the funnel of the net, along the extension or lengthening piece and into the cod-end, where they are retained.
What is a fishing pot or creel and what is it used for?
Pots (or creels) are small baited traps which can be set out and retrieved by the operating vessel. They are widely used on continental shelves in all parts of the world for the capture of many species of crustaceans (lobster, crab and shrimp) and fish, together with octopus and shellfish such as whelks. Potting is a highly selective method of fishing, since the catch is brought up alive, and sorting takes place immediately, allowing unwanted animals to be returned to the sea.
What is long-lining and what do fishermen use it to catch?
Long-lining is one of the most fuel-efficient catching methods. This method is used to capture both demersal and pelagic fishes including swordfish and tuna. It involves setting out a length of line, possibly as much as 50-100 km long, to which short lengths of line, or snoods, carrying baited hooks are attached at intervals. The lines may be set vertically in the water column, or horizontally along the bottom. The size of fish and the species caught is determined by hook size and the type of bait used.
What is a hydraulic dredge and what is it used for?
Hydraulic dredges either use jets of water to disturb the ground in front of a towed dredge to capture bivalves, like clams, oysters or scallops, or use a pump to suck bottom sediments on board ship where bivalves are screened out and the spoil is discharged back to sea.
What is a beam trawl?
In this type of trawl the mouth or opening of the net is kept open by a beam which is mounted at each end on guides or skids which travel along the seabed. The trawls are adapted and made more effective by attaching tickler chains (for sand or mud) or heavy chain matting (for rough, rocky ground) depending on the type of ground being fished. These drag along the seabed in front of the net, disturbing the fish in the path of the trawl, causing them to rise from the seabed into the oncoming net. Electrified ticklers, which are less damaging to the seabed, have been developed but used only experimentally.
What is a pelagic trawl?
When trawling takes place in the water column or in mid-water between the seabed and the surface, it is referred to as mid-water or pelagic trawling. Pelagic trawls target fish swimming, usually in shoals, in the water column i.e. pelagic species. These include seabass, mackerel, pollack, herring and sardines for example. Their effectiveness relies on traversing a considerable volume of water, and consequently nets are larger than bottom trawls and require a large vertical and horizontal mouth opening to provide net stability and capture large shoals of fish. The length of time the net is towed through the water is shorter than in bottom trawling in order to capture the shoals of fish the net passes through. To handle the large amounts of fish, pumps are used to transfer the catch from the cod-end to the boat.
What are the levels of mercury in different fish?
Measured levels of mercury in fish range from 0.09 parts per million to more than 0.5 parts per million. To view the levels of mercury in different fish, go to one or both of these sources: • the FDA Mercury Levels in Commercial Fish and Shellfish • the Natural Resources Defense Council Mercury Contamination in Fish Note that the exact amounts of mercury vary a bit by how fat and old the particular fish is and the level of mercury in the waters where it was raised.
Do all fish have mercury in them?
No, only those fish that live in water contaminated with mercury contain mercury in their flesh. For Americans, the most common source of mercury exposure is tuna fish. Other fish such as swordfish or shark can contain more mercury, but Americans eat more tuna, thus it poses a greater health threat. The fish highest in omega-3s and low in mercury include: anchovies, salmon, herring, mackerel, and sardines. For more information, go to the Natural Resources Defense Council Mercury Contamination in Fish site.
How has mercury contamination of fish happened and why is it important?
Fish is a great source of low-calorie protein for everyone’s diet. Some fish, though, are contaminated with high levels of methylmercury and other harmful chemicals. These chemicals can contribute to health hazards in people who may eat large amounts of contaminated fish.
Mercury is a naturally occurring element found in the air, water and soil. Mercury has also contaminated the environment mainly because of coal burning power plants. Mercury found in the power plant air pollution may contaminate the air, water and soil when it is spread by the wind and weather. When mercury contaminates water, like in a lake, it is changed into a more harmful chemical called methylmercury. Fish that live in water contaminated with methylmercury often become contaminated with mercury making them unsafe to eat.
The most common way people are exposed to methylmercury is by eating contaminated fish or shellfish. Scientific studies have shown that by eating large quantities of contaminated fish or eating contaminated fish too often, chemicals in these fish can build up in the human body. These chemicals can harm the immune system, reproductive system, brain functions and increase risks of certain cancers. Infants and children that have a lot of exposure to these chemicals may develop physical, mental or behavioral problems that they would not have had otherwise. This is why children, pregnant women and women who may become pregnant are much more at risk and should limit eating certain species of fish.
Local, state and the federal government agencies publish fish consumption advisories based on scientific data they obtain from monitoring water for contaminated fish. Some advisories are for specific bodies of water – like a lake or river. These advisories suggest which types of fish people should avoid or eat in limited quantities. Many advisories also include information about certain species of fish that are safe for most everyone to eat.
Almost every state in the U.S. has fish consumption advisories for methylmercury. To find information about fish consumption advisories in your state, you can visit the U.S. Environmental Protection Agency’s Fish Advisory website. Here you can learn about which species of fish may be unsafe to eat as well as which species of fish are safe to eat.
FISH SAFETY FAQ’S
How much fish should I eat when I am pregnant or breastfeeding?
The FDA’s data has indicated that the consumption of fish by women who are pregnant or who have just given birth is about 2.97 ounces per week in the U.S. That’s not enough. You should eat up to 12 ounces of fish per week, which may include up to 6 oz. of albacore tuna. None of the fish you eat should be fish that average more than 0.5 parts per million (ppm) of mercury. To find out which fish are not high in mercury (that is, have a mercury level less than 0.5 ppm) click here.
What fish should I avoid when I am breastfeeding?
According the EPA/FDA, advice for pregnant and breastfeeding women is that, only four fish should be avoided. These are: shark, king mackerel (not the small mackerel found canned in the supermarket), swordfish and tilefish. Additionally, marlin, a game fish caught off the coast of Mexico, is high in mercury and should probably not be eaten during pregnancy and breastfeeding. The FDA advice covers only commercially caught fish and advises that women consult local advisories regarding recreationally caught fish. To find out which fish are not high in mercury (over 0.5 ppm) click here.
Will cooking make sewage-polluted shellfish safe to eat?
Not entirely. Cooking will kill bacteria that cause some diseases, but it is not known whether certain virus diseases, such as infectious hepatitis, can be prevented by cooking. Red tide toxins are not eliminated by cooking.
Is it safe to eat oysters during the months without R’s
Yes. Fresh oysters properly refrigerated are wholesome and nutritious throughout the year. They spoil rapidly at high temperatures, however. The belief that oysters were unsafe to eat in May through August arose in earlier days when refrigeration was less prevalent than it is today.
How does the consumer know that shellfish are safe to eat?
Clams and oysters in the shell should be alive and the shells should be closed tightly or should close when the mollusks are tapped. The U.S. Public Health Service, in cooperation with the States, has a sanitation control program that covers the labeling and shipment of clams, mussels, and oysters. These shellfish may be harvested only from non-polluted waters and processed for shipment in sanitary plants inspected by State shellfish inspectors. Authorities periodically test water for sewage pollution and ban catches from polluted areas.
How unsafe are shellfish from polluted waters?
They are dangerous to man, causing mild to severe illness, sometimes death. Both sewage and industrial wastes can affect shellfish.
It is possible to purify shellfish from sewage polluted water for safe eating?
Yes. Sewage polluted shellfish transplanted to clean water purify themselves rapidly and become safe to eat.
Do shellfish contain mercury levels dangerous to man’s health?
No. Tests of shellfish to date have shown mercury levels to be below those considered dangerous to humans.
OMEGA 3’S FAQ’S
Fish get omega-3 fatty acids from eating algae, can I too?
Only certain algae make omega-3s, and the type of omega-3s is only DHA. So look for supplements that state the content as algal DHA.
To get the benefits of omega-3s should I stop consuming omega-6s completely?
First, it is important to understand both types of fatty acids are essential and must be obtained in the diet. Some scientists believe that it is important to have a balance of omega-3s and omega-6s in our diets because they have different effects in the body and some of these effects are in opposition. For example omega-3s help reduce inflammation and blood clotting in the body, and most omega-6s tend to promote inflammation and increase blood clotting. Some scientists believe if the ratio of omega-6 to omega-3 is not optimal, these processes will be imbalanced. The American diet is about 10 to 1 in favor of omega-6 fatty acids, which some scientists believe promotes inflammation and contributes to some of our common diseases. However, definitive clinical proof one way or the other is still lacking. So both omega-3s and omega-6s should be consumed in balance. For more information go to Estimating the Likely Impact of Essential Fatty Acids Intake.
Does raw fish and sushi contain the same amount of omega-3s as cooked fish?
Yes. The omega-3s are found in the flesh of the fish, and little loss of omega-3s occurs in cooking. Consumers should be careful with consuming raw fish and sushi due to potential contaminants, and should follow food safety guidelines. Get more information on mercury in fish from the US Environmental Protection Agency.
Will I get more omega-3s if I eat farm-raised or wild fish, like salmon?
Many types of fish are now grown in fish farms. This includes: salmon, trout, tilapia, catfish, and shrimp. Fish that are farm-raised have different levels of omega-3s from those that live in the wild in oceans, lakes, or rivers. This is caused by what the fish are fed. When farm-raised fish are fed plant based diets, their omega-3 levels may be reduced. However, some fish farms use feed that contains fish, and thus maintain the DHA in the fish at a level equivalent to that in the wild fish of that species. There has been some indication that farm-raised fish may contain more contaminants than fish living in the ocean; however, the amounts vary and appear to be minor.
What type of tuna is the best source of omega-3 fatty acids?
Bluefin and White Albacore tunas are the richest sources of EPA and DHA omega-3s.
Which fish have the most omega-3s in them?
Fatty/oily fish contain the most omega-3s. These include: salmon, albacore tuna, mackerel, anchovies, herring, sardines, sea bass, rainbow trout, and pompano.
Do all fish have the same amounts of omega-3s?
No. The levels of omega-3s vary from fish to fish, depending on several factors. One factor is where the fish live; there are differences in omega-3 levels between fresh-water and ocean fish, and between fish from colder and warmer waters. Another difference may occur between fish living in the wild and those living in fish farms because of the food they eat. The types of fish that are higher in omega-3s are generally called “fatty” or “oily” fish, and come from cold water areas. Salmon, anchovies, mackerel, bluefin tuna, sardines, trout, white albacore tuna, sea bass, and pompano are high in omega-3s, particularly EPA and DHA. Generally, wild fish have much more omega-3 than farm-raised fish. More information on the omega-3 content of fish is available from the USDA. Some fish, such as tilapia and catfish, do not have much omega-3s, but have high levels of arachidonic acid, or omega-6 fat. Eating too much arachidonic acid can increase your risk of heart disease because it can cause inflammation and contribute to the buildup of plaques which can block your arteries.
How do wild salmon and farm-raised salmon compare nutritionally?
Nutritionally they are very similar. The specific nutrient content of farm-raised salmon is dependent on feed. However, generally, farm-raised salmon are a little higher in fat, thus a little higher in omega-3 fatty acids. Both are good choices to increase omega-3 fatty acids in the diet. The American Heart Association recommends at least two servings of fish (preferably fatty fish such as salmon) per week.
What are salmon fed in a hatchery?
Vitamin-rich, high-protein diets made up of dried meals from coarse fish, animal meat excess, plant meal and bone meal, or meal from calcium-rich shells.
What are groundfish?
A bottom-dwelling fish, especially a commercially valuable marine species such as flounder or cod. Many of these species are managed as a species complex because they are often taken together by trawlers or longliners.
Is “scrod” an actual fish?
Scrod is a term restaurants and seafood markets use to describe young cod or any of a variety of lower quality whitefish (haddock or pollock for example). Scrod or "schrod" is also served as "catch of the day".
Why do fish at the market sometimes have a strong odor?
For most species, truly fresh fish is almost odorless. Fish begin to smell "fishy" when deterioration sets in, often caused by incorrect storage practices that bring about the release of oxidized fats and acids through bacterial and enzymatic action.
How can I tell if the fish I’m buying is really the fish the seller says it is?
It's important to know what you're buying to get the best value for your money when purchasing seafood. Be wary of unusual bargains - some seafood is seasonal. If there is a considerable difference between the price of a fresh product and what you are accustomed to paying, it could be that it is from the last season's frozen inventory. Buy from a reputable dealer. If the fish you choose looks or smells different from what you expect, discuss it with the fish market manager. Look for firm, shiny flesh that bounces back when touched. If the head is on, the eyes should be clear and bulge and the gills should be bright red. The fish should not smell "fishy" - it should smell like a fresh ocean breeze. Click here for more tips on buying, preparing, and storing seafood.
What is aquaculture?
Aquaculture by definition is a form of agriculture that involves the controlled propagation and cultivation of aquatic plants and animals as well as the processing and marketing of these aquatic products. This industry is rapidly growing with the major fish crops raised in the United States as catfish, trout, salmon, carp, shrimp, striped bass and tilapia.
What are menhaden?
Menhaden are silvery, herring-like fish that travel in large schools along the Atlantic and Gulf of Mexico coasts of the United States. Plankton-eaters, menhaden attain a weight of about three-quarters of a pound. Atlantic Menhaden flesh is oily and considered inedible for humans. The fish are caught by purse-seine nets in shallow water and processed into oil for cosmetics and fish meal for animals, particularly for poultry. Menhaden support the largest fishery by volume and the eighth most profitable fishery in the United States.
What do herring eat?
They subsist on zooplankton. Herring, which populate the oceans in enormous numbers, play an important role in the oceanic food chain in that they are primary converters of plankton. Herring form the food base for many larger species, and enormous quantities are taken commercially for fish meal, human food and bait.
What is the difference between the Atlantic salmon and the Pacific salmon?
The Atlantic Salmon (Salmo salar) is actually one species within the genus Salmo. Pacific salmon are represented by seven different species, see question above, and belong to the genus Oncorhynchus. The seven Pacific salmon species have life histories that are extremely complex and vary widely within and between species. However, all the Pacific salmon die shortly after spawning. Atlantic salmon have a much less variable range of life history strategies across the species and have high post spawning mortality but are capable of surviving and spawning again.
Are any snails commercially caught for food off the coasts of the United States?
The most commonly eaten snails in this country are the abalone, caught in the waters off California, and various conchs from Atlantic waters.
How many kinds of tuna are there, and which kind makes up the biggest catch?
There are seven commercial and sport-caught tunas, as well as several related species, all of which are members of what is called the scombrid family. Commercially caught tunas consist of albacore, bigeye, blackfin, bluefin, bonito, skipjack, and yellowfin. Yellowfin, taken in the eastern Pacific and tropical Atlantic, makes up the biggest U.S. commercial catch. Albacore, caught in the eastern Pacific, is the true "white-meat" tuna; skipjack, caught throughout the world in tropical and subtropical waters, makes up the second largest U.S. commercial catch; bigeye is caught mostly in tropical waters; blackfin is caught commercially only in the Caribbean and off South America; the very large bluefin (rod-and-reel record, 1,040 pounds) is a highly prized sport catch in the Atlantic and Pacific; and the widely distributed bonito is used largely as pet food.
ENVIRONMENT /SUSTAINABILITY FAQ’S
Is farmed seafood better for the environment than seafood from the wild?
As frustrating as it may seem when you are looking for a "yes" or "no" answer, the real answer is "it depends." Aquaculture, or the farming of fish, is a booming industry and can take the pressure off some depleted wild fish. But not all. For example, farmed catfish and tilapia are increasingly popular with seafood lovers and can be a smart alternative when they're raised in closed-systems where wastes are controlled and there is little chance of the fish escaping. These fish are also fed a vegetable-based diet such as corn and soy-based feed. Other farmed species such as Atlantic salmon can be more problematic. In places like the Pacific, they can escape and threaten native species with diseases. And when some farmed species like salmon are fed large quantities of wild caught fish, we're not really conserving fish. By following the advice of organizations that have transparent methods of rating seafood, you can ensure that you are making choices that help solve the problem.
What’s “sustainable seafood?”
Sustainable seafood is from sources, either fished or farmed, that can maintain or increase production into the long-term without jeopardizing the affected ecosystems.
Some of the key issues that help us to evaluate whether a fishery is sustainable include:
Inherent vulnerability of the species to fishing pressure
Status of the species population
Nature and extent of bycatch
Effect of fishing practices on habitats and ecosystems
Effectiveness of the fishery management
Some of the key issues used to evaluate fish farming include:
Use of marine resources in fish feed
Risk and impacts of escaped farmed fish to wild fish
Risk and impacts of disease and parasite transfer to wild fish
Risk and impacts of pollution and other impacts on habitats and ecosystems
Effectiveness of the fishery management
What about lobsters, crabs, and shrimp – are they affected by PSP?
Lobsters, crabs and shrimp are not filter-feeders - they're crustaceans, and therefore do not accumulate the toxin in their meat, so as a general rule they are not affected by red tide. The one exception is that lobster tomalley can contain the PSP toxin, as well as other pollutants. The tomalley is the "green stuff" found in the lobster's body cavity; it acts something like a liver and filters toxins out from the animal's system. So, lobster meat is fine to eat, but lobster tomalley should NOT be eaten.
How can I tell where the seafoods at the store came from and how they were caught?
We have found that American west coast markets label fish more precisely and extensively than they do on the east coast. So we know it can be done. Still, many markets and restaurants give only the common name for seafoods, and do not specify which ocean the species came from, or how it was caught. Some seafood counters and menus will selectively use labels to promote popular seafoods such as "Alaska salmon" or "New Zealand mussels," but that is the exception. Furthermore, some farmed salmon is being sold as "Atlantic salmon," even if it was an Atlantic species raised in the Pacific. This certainly leaves many questions. The conservation community is working together with members of the seafood industry to find ways to ensure that every fish has a label indicating its species name and place of origin. Until there is more information, don't be dismayed when you go to select seafood. Instead, just ask where the seafood has come from. And if the person at the counter or the waitperson does not know, tell them why you care! It may take time, but the market will follow.
Is it OK to eat shellfish during a Red Tide event?
If you buy your shellfish from a reputable dealer, or harvest your own shellfish from an area that has not been closed to harvest, then you can enjoy all the shellfish you can eat! Most states have extensive monitoring programs to ensure that contaminated shellfish do not enter the market.