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COMMERCIAL FISHERIES
NEWSLINE COMMERCIAL FISHERIES NEWSLINE Abstract: Advisory/extension newsletter for keeping Great Lakes commercial fishing and aquaculture industries informed of relevant regulations, events, opportunities and workshops. -------------------------------------------------------------------------------------------------- WORKSHOP -"MARKETING PARTNERSHIPS: EXPANDING COMMERCIAL FISH MARKETS AND INCREASING PROFITABILITY OF COMMERCIAL FISH BUSINESSES" June 8, 1995 This upcoming workshop will focus on three areas:
Several panel discussions will occur during the workshop and will include representatives of dockside and wholesaler buyers; processors, retailers, restaurants, and institutions; fishermen; government agency representatives from the Michigan Department of Agriculture and National Marine Fisheries Service; and Michigan State University and Sea Grant. The workshop fee will be $10 and will include lunch and coffee breaks. For more information please contact Sea Grant Agents Ron Kinnunen (906/228-4830) or Jim Lucas (906/635-6368); or Bill Scarbrough at (906) 644-2541. -------------------------------------------------------------------------------------------------- The National Training Branch, the education arm of the U.S. Department of Commerce's Seafood inspection program, would like to announce three 2-day HACCP workshops to be held in: Minneapolis MN May 23-24, 1995 HACCP, or Hazard Analysis Critical Control Point, is a systematic approach ensuring the quality and safety of food products. Developed for the space program, the HACCP approach identifies each step during production where quality or safety hazards may occur. Under the HACCP system, after hazards have been identified, systems are then put in place to control hazards and document them; this documentation provides an easy-to-follow paper trail if a problem occurs. This program demonstrates how HACCP can be used to come into compliance with existing and evolving federal and international regulations as well as how HACCP can be used as an overall total systems management technique. Participants are taught basic HACCP principles and, importantly, leave with methods they can use to develop and implement a custom HACCP plan for their own facility. The NMFS (National Marine Fisheries Service) training program meets all the FDA's requirements for safety, wholesomeness and economic integrity and includes a few extra quality assurance techniques. The NMFS program also offers certification and preapproval of HACCP plans. HACCP is not as complicated as it seems at first glance. Everyone in the plan can easily learn and must understand the basic principles that make it work. A few key personnel can, with training, write the plan. It is important to learn as much as possible at the start to make the transit ion to HACCP easier. Most seafood producers who use the system say HACCP saves money through greater efficiency and reduced shrink. To register or receive more information on attending one of these workshops, please contact Judy Sprague (Training Specialist-NMFS) at (207) 596-0947 or Karla Ruzicka (Assistant Chief-NMFS) at (508) 281-9216. -------------------------------------------------------------------------------------------------- Although it is difficult to reach a definitive conclusion on the impacts that ruffe will have on aquatic ecosystems in North America, there is legitimate cause for concern. Ruffe have the potential for significant impacts on warmwater and coolwater fish communities. As ruffe have increased sharply in Duluth Harbor, the populations of yellow perch, emerald shiner, spottail shiner, and trout-perch have all declined. Although this decline cannot be demonstrated to be caused by the ruffe, it is possible that competition for food with ruffe is at least partially responsible for the declines seen in these indigenous fish populations. If this is the case, then there may also be implications for indigenous predators such as walleye that depend on these smaller species as prey. Indigenous predators in Duluth Harbor are not feeding heavily on the introduced ruffe despite their abundance. The possibility also exists that ruffe may prey on eggs of lake whitefish and other coregonine fishes in the Great Lakes, although this has yet to be demonstrated. Laboratory studies have shown that ruffe will prey on the eggs of European whitefish species, and introduced ruffe have been shown to feed on the eggs of the powan (a Eurasian whitefish) in Loch Lomond, Scotland. Ruffe were a significant predator of powan eggs, and their predation on eggs would likely become an important influence on the recruitment of powan. Recruitment problems in whitefish in Russia have also been attributed to egg predation by introduced ruffe. Although lake whitefish and other coregonines spawn in the fall when water temperatures are low, the ability of ruffe to feed at low temperatures may allow them to prey on lake whitefish eggs. Also, lake whitefish eggs take 4 to 5 months to hatch and are consequently available to ruffe for a long period of time. Predicting the ecological impacts of ruffe on aquatic ecosystems in North America is extremely difficult. It is not known if ruffe will pose a threat to lake whitefish populations; however, this potential exists based on EuropEan experience. It is also not known if trends observed in Duluth Harbor were caused by ruffe and will be manifested in other areas where ruffe spread. It is likely that such a rapid increase in population size has indeed had some impact on the native fish community. It is safe to assume that the spread and establishment of ruffe will have some detrimental impacts to aquatic ecosystems of North America and our native biodiversity. The degree of these impacts is unknown, but given the nature of the resource at risk and the potential for ecological and economic harm, the spread of ruffe should be viewed as a serious threat. -------------------------------------------------------------------------------------------------- Because of the concern that ruffe may be collected during the commercial and personal harvest of minnows, the waters of Lake Superior and its tributaries for 1/2 mile above their mouth have been closed to the taking of minnows effective April 1, 1995. These recommended actions are intended to slow the eastward expansion of ruffe in the Great Lakes, prevent their introduction to inland waters and hopefully contain them in the western end of Lake Superior. The Director of the Michigan Department of Natural Resources also ordered that for a period of five years no person shall take, attempt to take, possess or transport Eurasian ruffe (Gymnocephalus cernuus). This order took effect April 1, 1995 and shall remain effective through March 31, 2000. Measures other than bait bucket control currently being applied or considered to control ruffe in Lake Superior include ballast water management, chemical control and predator fish population enhancement. All Great Lakes States, Ontario, the U.S. Fish and Wildlife Service, the National Biological Service, the Great Lakes Shipping Industry, the U.S. and Canadian Coast Guards, and the Native American tribal governments are involved with developing this control strategy. Areas scheduled for chemical control near the Michigan-Wisconsin border on Lake Superior include Saxon Harbor and Oronto Creek, Wisconsin, which are just inside the Wisconsin line. This is a very small site planned for treatment with rotenone in 1995. It is also planned this year to treat Black River Harbor, Michigan, with TFM. Ruffe treatment will require spraying the backwaters inside the breakwall. Experimental treatments for ruffe control are also planned for the Brule and Iron Rivers in Wisconsin. -------------------------------------------------------------------------------------------------- At the recent Great Lakes Fishery Commission meetings fishery biologists from the National Biological Service Great Lakes Center in Ann Arbor, Michigan and Ashland, Wisconsin presented the following forage fish stock reports for the upper Great Lakes. LAKE SUPERIOR Lake herring biomass index values fluctuated considerably from area to area and year to year. Those dynamics occurred mainly as the result of varying strengths of recruiting year classes. Catches in spring 1994 trawl tows were dominated by the 1988-1990 year classes. The three most recently formed year classes (1991- 1993) were weak, and the 1993 year class was the weakest recorded during the 17 years of assessment. The mean biomass for U.S. waters fish was 73% larger in 1992-1994 than the 17-year mean. Mean lengths at ages 4-6 were significantly different among geographic areas in Lake Superior. At all ages, fish in Wisconsin waters were larger than fish in Ontario waters, and fish in Ontario waters were larger than fish in Michigan waters. Too few lake herring were collected in Minnesota waters to compute growth statistics. The total annual mortality indices appeared to be somewhat lower for fish from Wisconsin waters than for fish from Michigan and Ontario waters. Again, too few lake herring were collected from Minnesota to compute mortality statistics for comparisons with those for fish from other areas. The mean strength of rainbow smelt year classes produced in 1988- 1993 was slightly above the 17-year average. However, large ( 200 mm) fish were still relatively rare in 1994 except in western Ontario waters. Because total annual mortality rates have not declined from the high levels measured from the early 1980s to the present, we expect no substantial increase in numbers of large rainbow smelt next year. Rainbow smelt biomass was near the 17-year low in 1994 within all jurisdictions except for western Ontario waters. During the last five years, rainbow smelt biomass has remained steady or declined slightly within each state and in eastern Ontario, whereas biomass in western Ontario has fluctuated annually without a trend. Growth of rainbow smelt was slower in western Ontario waters than in the remainder of the lake. Mean lengths at ages 2-4 in 1992 were significantly smaller for western Ontario fish than the mean lengths for fish collected from all other areas combined. LAKE HURON Catches of alewives increased four-fold in 1994 with a corresponding increase in the biomass estimate to 60,100 t in 1994 compared to 18,690 t in 1993. Although this increase was substantial, it was not clear if the later sampling time affected the catches. Catches of bloaters in the 21-m trawl in 1994 at the four standard survey depths between 46- and 73-m were similar to those in 1993. The biomass of bloaters in U.S. waters was estimated at 40,400 t in 1994. The 1994 bloater year class, based on catches of young-of-the-year, appeared to be very small and a decline in lakewide bloater biomass is anticipated in 1995 or 1996 due to the persistent lack of recruitment in recent years. Adult rainbow smelt catches increased slightly in 1994 and the biomass was estimated at 15,520 t. Catches of young-of-the-year rainbow smelt were very large and the 1994 year class may be the largest we have seen in recent years. Catches of juvenile lake whitefish were about 50% larger this year than in 1993. Catches of slimy sculpins and ninespine sticklebacks were similar to 1993 and deepwater sculpins and trout-perch increased in abundance. LAKE MICHIGAN Relative abundances of "adult" bloaters, smelt and alewives all decreased in 1994 for the second year in a row. Slimy sculpins were slightly more abundant in 1994, but abundance of deepwater sculpins was the lowest since 1974. Predation from a greatly expanded burbot population may be implicated in the low deepwater sculpin abundance. Reproduction of yellow perch was very poor for the fourth year; only one was taken lakewide in 1991 and none in 1992-1994. Recruitment apparently has been declining in the bloater based on decreasing abundance and biomass and a gradual increase in the modal lengths of adults. The extremely low abundance indices of YOY bloaters may have been exaggerated, however, by earlier sampling in the 1990's. Estimated total biomass of prey fish available to bottom trawls in 1994 was 265 thousand metric tons (t), compared to 322 thousand t in 1993, and consisted of 73.0% bloaters, 6.6% alewives, 2.9% rainbow smelt, and 17.4% sculpins. The question is asked, in closing, whether reported effects of exotic invertebrates on food web dynamics and bioenergetics of prey fish may be depressing prey fish recruitment, as measured by these surveys. -------------------------------------------------------------------------------------------------- A program for the reestablishment of bloater and deepwater sculpin populations in Lake Ontario is currently under development for consideration by the Ontario Ministry of Natural Resources and the New York State Department of Environmental Conservation. The program will include identification of regulatory and policy requirements, disease considerations, technical feasibility, and a potential time frame. Reestablishment of these native species may be possible now that Lake Ontario alewife populations have declined. --------------------------------------------------------------------------------------------------
Trap nets have been promoted as an efficient means for harvesting lake whitefish in the Great Lakes while limiting mortality to ther (non-target) species. All state-licensed fisheries for lake whitefish in Michigan waters of Lake Superior use trap nets. During 1983-1989, these fisheries were sampled annually by Richard Schorfhaar and James Peck of the Michigan Department of Natural Resources to estimate catch and mortality of non-target species. The samples represented 9% of the total trap-net effort by these fisheries. Non-target fishes killed annually by state-licensed trap nets in Michigan waters of Lake Superior, with mean annual catch in parentheses, were estimated as: 131 (19,721) sublegal lake whitefish, 414 (11,341) lake trout, 26 (37) coho salmon, 6 (15) chinook salmon, 6 (11) rainbow trout, 12 (55) brown trout, 41 (143) lake herring, 39 (67) round whitefish, and 0 (48) lake sturgeon. All dead fish were gilled in the pot portion of trap nets. The only non-fish species observed in trap nets was the common loon. The estimated annual catch of common loon was 263, with 86% of these caught in trap-net hearts. The mortality rate for loons in trap nets was 100%. No modifications of trap nets or fishing restrictions were recommended to reduce catch and mortality of non-target fishes in Lake Superior. However, it was recommended that mesh size in the top of the hearts be increased to 14-in stretch mesh to reduce catch and mortality of common loons. -------------------------------------------------------------------------------------------------- A recent presentation by Charles Pistis, Sea Grant Extension Agent, to the Council of Great Lakes Governors Special Fish Advisory Panel suggests that fish contaminant exposure rates may be overstated. With the decline of Great Lakes fishery, the charter boat industry has declined - from 1,000 boats in 1986 to 543 today. Preliminary data from a 1994 Great Lakes Charter Boat Survey by the Great Lakes Sea Grant Network indicates that 70% of respondents ranked lack of fish as the worst problem for the charter fishing industry, 42% ranked fisheries management first, and 38% ranked fish consumption advisories first. Pistis discussed a data set collected by the MDNR Fisheries Division for the period 1985 to 1992, which indicated that the Lake Michigan fishery has declined substantially since 1986. He indicated that, as a consequence, calculations of exposures, number of meals consumed, types of species consumed need to also change and be reflective of current conditions. It is important that the Panel have the most recent data when looking at estimates of exposure. He calculated consumption from creel census data, which was obtained by counting actual fish caught, rather than using data obtained by asking people how much fish they thought they had eaten during a given period of time. Assuming that the edible portion is 40% of the poundage caught, he calculated that fish consumption is about 2.3 g/day; much lower than estimates currently being used as a basis for fish advisories. For instance, West's 1993 research, based on a survey of 7,000 anglers, calculated a consumption rate of 14.5 g/day. Pistis also discussed another estimate by Smith (1995 unpublished manuscript) which used lake trout to demonstrate a discrepancy between the amount of fish the lakes can produce and the amounts being used to calculate exposures, saying that the lakes cannot produce enough to produce those exposures. -------------------------------------------------------------------------------------------------- Test results show average contaminant levels in two 1836 Treaty water fish species - whitefish and lake trout - are within federal and state consumption guidelines, providing further evidence of successful regulations reducing the discharge of toxic substances into the Great Lakes according to Tribal authorities. The Inter-Tribal Fisheries and Assessment Program (ITFAP), based in Sault Ste. Marie, Michigan, annually monitors fish species from 1836 Treaty-ceded waters of southeastern Lake Superior, and northern Lakes Michigan and Huron. Lake trout and whitefish were collected from the Naubinway area of Lake Michigan in 1994. Chemical testing was performed by Canada's Department of Fisheries and Oceans. The fish ranged in size from 17 to 27 inches. "This year's test results showed that Lake Michigan whitefish were well below Michigan's fish consumption guidelines, good news for everyone that likes to eat whitefish," says Amy Owen, Environmental Scientist for ITFAP. "It's encouraging to see further evidence that contaminant levels appear to be stabilized or decreasing across the Great Lakes." ITFAP also tested whitefish and lake trout from the St. Ignace area of Lake Huron in 1993 and the Whitefish Bay area of Lake Superior in 1992. Fish contaminant levels varied only slightly between the upper Lakes, with Superior the lowest, followed by Huron and Michigan. "Average contaminant levels in Treaty waters fish are below established guidelines for all three lakes," stressed Tom Gorenflo, ITFAP Program Director. "We believe increased regulations restricting the discharge of toxic substances into the Great Lakes has led to this success, and expect the trend of declining contaminants to continue." For more information, contact Amy Owen at (906) 632-0072. -------------------------------------------------------------------------------------------------- A revised edition of Eating Great Lakes Fish has been published by Michigan Sea Grant. This publication has updated trimming and cooking methods of fish to reduce contaminants. Research at Michigan State University shows that trimming and cooking can reduce contaminants in some fish by as much as 81%. Furthermore, the researchers found that only two of the 227 skin-on boneless fillets analyzed had amounts exceeding 1994 FDA action levels for any of the 13 contaminants studied. The vast majority of the fish studied had contaminant concentrations below the current level of concern even before they were processed. To receive a copy, please contact your nearest District Extension Sea Grant Agent. -------------------------------------------------------------------------------------------------- A publishing error was recently found in a recently released Michigan Sea Grant publication entitled Freshwater Fish Preservation - North Central Regional Publication 498, November 1994. This publication was distributed at the Michigan Fish Producers Association Annual Meeting and at the Michigan Aquaculture Association Annual Conference. There is an error on page 4 of this publication and it needs to be replaced with a new page. If you happened to pick up a copy of this publication and would like a corrected version, please contact your nearest District Extension Sea Grant Agent. -------------------------------------------------------------------------------------------------- The National Marine Fisheries Service has developed a fax on demand service to provide members of the seafood industry with up-to-date seafood industry market information (e.g., weekly trade leads, daily Fulton Market fresh fish prices, daily Boston Auction prices and other seafood market information). To use the service, you will need to place your call from a fax machine phone. Dial (301) 713-1415. At the mailbox prompt, enter 200 followed by the # (pound) key. Then select item 1 followed by the # (pound) key for a menu of available faxes. A fax message will automatically be sent to the fax machine that you are dialing from. Other than your long distance telephone charge for the call, the service is free. Note, some fax machines may not be compatible with this service. For more information on the Fishery Market News Fax Service, contact Bill Utley at (301) 713-2328. -------------------------------------------------------------------------------------------------- Just another day in the life of a Sea Grant Agent - Jim Lucas shared this episode which recently occurred. A friend once commented that Michigan State Extension has information on everything, just ask them! If they do not have it, they will know where to locate just about everything under the sun. This pompous attitude got me into trouble last week with the following conversation. I received a message that said to return a call about missiles. Since Michigan Sea Grant was one of the first agencies to put time and effort into the public information about zebra mussels, we have become a clearing house for this information and foremost authorities in our fine state. I assumed the person really wanted to talk about mussels, not missiles, and preceded to call back in my confident extension education voice. On my return call I answered the person that Michigan Sea Grant has been tracking the location of mussels for about five years now and could you please give me the location of these pests. I was told the Hammond Bay region of Lake Huron and I opened my zebra mussel map and agreed with them that they have been found in that region for about five years. The caller then asked what I can do about them? I explained that once these horrible things are introduced into a body of water there is little that can be done about them, and they have spread throughout the entire Great Lakes. The caller was alarmed that missiles had been dropped throughout the Lakes and who was responsible for this type of behavior. I answered with my knowledgeable Extension Educator confident voice that once the mussels were introduced they breed and moved into additional habitat, carried by the currents, and that they stick to the bottom of boats and ships and can even be found in our inland lakes and the Mississippi River System. At this moment the caller realized that I did not know what I wastalking about and asked me to spell missile for him. So I did "M-U-S-S-E-L." All I heard was a loud laugh and they preceded to tell me they were talking about missiles, as in bombs. The person on the other line had to excuse themselves, I think they either spilled their coffee or choked on their donut from laughing so hard. After the person composed themself and I was humbled into listening better, they called back and faxed some information to me on missiles found on the bottom of Hammond Bay, Lake Huron. I am glad they could not see the embarrassed look on my face. It seems that commercial fishermen have found more than one missile-like device on the bottom of Hammond Bay. One fisherman became concerned over the safety of these devices and called Lt. Maizer of the U.S. Coast Guard to investigate. What Lt. Maizer found was a practice round that only contained plaster. While it may seem very harmless, it is possible the next identical missile with plaster may still contain a propellent. Bringing the device out of the depths of the lake may activate it, not a happy thought. If a fisherman, boater or diver finds one of these practice rounds, it is best not to handle them and contact your local Sheriff Department. They will know the best way to handle these devices. The Chippewa-Ottawa Treaty Fisheries Management Authority has provided me with an 8 1/2" x 11" copy of a placard to display. If anyone would like a copy, please contact Jim Lucas at (906) 635- 6368. -------------------------------------------------------------------------------------------------- If you operate a vessel 26 ft. or longer on the Great Lakes, oceans, or tributaries, your boat must display a placard with the following statement: "The discharge of all garbage into the Great Lakes or their connecting or tributary waters is prohibited." The statement is the outcome of Annex V of the MARPOL Treaty, an international law for a cleaner, safer marine environment that is intended to reduce the discharge of garbage from ships. The placard serves to inform those on board boats of pollution laws and penalties. The rule stipulating the use of the placard was in effect in 1991, but enforcement was delayed while some of the language in the statement was being clarified. -------------------------------------------------------------------------------------------------- A cooperative agreement between the United States Fish and Wildlife Service (USFWS) and the Keweenaw Bay Indian Community (KBIC) Baraga County, Michigan, was signed which will support a broodstock isolation facility and enhance fish restoration in the Great Lakes. This cooperative project will include the operation of a broodstock isolation facility at the Keweenaw Bay Indian Fish Hatchery and the production of lake trout at the Iron River National Fish Hatchery to support KBIC priorities. This agreement will foster the continued integration of fish health and fish genetics into the USFWS captive broodstock program. The USFWS will initiate this cooperative program in September of 1995. The success of this program is dependant on the ability to capture and spawn mature fish of native wild stocks and transport fertilized eggs to the Keweenaw Bay Indian Fish Hatchery. The USFWS is seeking input to identify the stocks that should be included in the isolation facility and cooperation to capture sexually mature adults. Please direct your comments through Dale Bast (715) 372-8510, manager of the Iron River National Fish Hatchery. The final selection of wild stocks will occur after input from Lake Superior, Lake Huron, and Lake Michigan Technical Committees (July and August 1995). Participation and support is critical to the successful implementation of this agreement. -------------------------------------------------------------------------------------------------- The North Central Regional Aquaculture Center (NCRAC) will hold workshops on Sunfish Aquaculture (May 22, 1995), Tilapia Aquaculture (May 23, 1995), and Aquaculture Wastes and Effluents (May 24, 1995) in Rosemont, Illinois. Individuals who have an interest in the subjects of these workshops are invited to attend. Representatives of the regional aquaculture industry are particularly welcome. Individuals interested in the project, but unable to attend, should send an alternate to articulate their interest. The purpose is to identify interested parties who are best qualified to work on project objectives by virtue of a demonstrated record of expertise and access to facilities required in the project. These people will form a Work Group for the purpose of writing a project outline that will be submitted to NCRAC by October 1, 1995 to obtain funding. NCRAC's Board of Directors has allocated funds to be spent on this program over a two-year interval September 1, 1996 to August 31, 1998. The workshop meetings will be chaired by Dr. Ted R. Batterson, Director, NCRAC, Michigan State University. Anyone planning on attending the workshop MUST contact the director's office. This can be either in writing, telephone, or Fax. Dr. Ted Batterson, Director Also NCRAC has requested a call for statements of interest on Alternative Aquaculture Species for the North Central Region. The goal of this project is to ascertain the production and marketing potential for aquatic animals and plants in the North Central Region (NCR) that have either not been the focus of other NCRAC-funded projects (e.g., walleye, yellow perch, hybrid striped bass, rainbow trout) or are not currently being cultured in any significant quantity within the region. Statements of interest must be received by NCRAC no later than JUNE 1, 1995. Facsimile transmission copies are not acceptable. All submissions should be addressed to Dr. Ted Batterson. ------------------------------------------------------------------------------------------------- Patrick Muzzal of the Department of Zoology at Michigan State University has for several years studied the parasites and diseases of fishes, including trout. One area that interests Pat is the parasites and diseases of fish in culture ponds. Pat would like to study the parasites and diseases of brook, brown, and (or) rainbow trout in culture ponds or raceways in 1995. Study will involve the examination of 25 fingerlings in July and 25 in October from the same pond. Broodstock will also be examined. Comparisons will be made between ponds. Ponds will be numbered so location and owner remain anonymous. This study will result in a list of parasites and diseases of fingerlings and broodstock in culture ponds; an analysis of the relationship between fish productivity and parasite loads; and a pond assessment, management use system to determine what type of pond should be used in culture. If you would like more information on this proposed study or
would like to supply trout, please contact: -------------------------------------------------------------------------------------------------- It is well documented that oxygen and then ammonia are the limiting factors for aquaculture production. Ammonia is not as easy to alleviate as oxygen and is produced by fish primarily from the gills and secondarily in the urine. Ammonia is also produced by the decomposition of food and fecal material by bacterial action. Rainbow trout produce about 17 mg of ammonia per kilogram of body weight per hour. A one-pound fish would produce about 185 mg of ammonia per day. For every pound of feed per 100 pounds of fish per day, 0.0289 pounds of ammonia would be produced. A pond or raceway with 5000 pounds of fish would produce about 2.0 pounds of ammonia per day based upon a feeding rate of 1.4 percent. The un-ionized form of ammonia is the most toxic and is dependent upon pH and temperature. The ammonia interferes or effects the hemoglobin in the blood to retain oxygen. There are several ways to reduce or eliminate ammonia from water by filtering. Filtering can be classified into three general categories: (a) mechanical, (b) biological, and (c) chemical. Mechanical filtration is the physical separation of suspended particulate matter from the water. It is accomplished by passing the solution through a suitable media that traps the particles. Examples of mechanical filtration include sand filters (pressure and gravity flow), stationary screens, rotary screens, microstrainers and diatomaceous earth filters. Mechanical filters usually exhibit a high head loss and require more energy to operate than biological filters. Biological filtration is defined as the mineralization of organic nitrogenous compounds by bacterial action. It can be either aerobic or anaerobic. Aerobic biological filtration is called nitrification. Anaerobic biological filtration is called denitrification. Of the biological treatment methods studied for the removal of ammonia, the nitrification process appears to be the most promising. The reasons for this are: (1) high potential removal efficiency, (2) process stability and reliability, (3) easy process control, (4) land area requirement, and (5) moderate costs. Nitrification is the oxidation of ammonia to nitrite and thence to nitrate by autotrophic bacteria, namely Nitrosomonas and Nitrobacter. The Nitrosomonas reaction is the rate-controlling step. The requirement for nitrification is the presence of ammonia, oxygen, nutrients, a low level of organic carbon, and a substrate for the bacterial to attach to. This substrate is called media and is available in various forms. Some of the more commonly used media are: oyster shell and rock, expanded shale, plastic rings, plastic beads, plastic saddles, porcelain saddles, styrofoam beads, and dolomite rock. Chemical filtration is the removal of substances from a solution on a molecular level by adsorption on a porous substrate or by direct chemical oxidation. Examples of chemical filtration include ion exchange where a natural zeolite such as clinoptilolite is used as the resin for the adsorption of ammonia. Clinoptilolite is a sodium-calcium-aluminum silicate that has a very strong preference for ammonium ions and is abundant in the southwestern areas of the United States. Clinoptilolite may be the best filtration available to the fish culturist. The use of clinoptilolite in fish hatcheries began with the adsorption of the ammonia and then regenerating the clinoptilolite with a brine solution. The use of air stripping and pH adjustments was also employed. The economics of air stripping, brine solutions, and pH adjustments was not conducive to hatchery operations. It appeared that only a facility near sea water could use the clinoptilolite filters. Later, probably due to lack of the operators to maintain the systems, the filters were operated as biological filters. This concept was much easier for hatcheries to adopt and showed signs of success. There are several hatcheries that are successfully using clinoptilolite on a production basis to date. Valley City National Fish Hatchery, located in North Dakota, has a 110 gpm system which was designed and built in 1981. The system is currently operating very effectively as a chemical/biological filter. Lahontan National Fish Hatchery is located in Gardnerville, Nevada. Their 5500 gpm system was modified in 1991 to a clinoptilolite system. This system is operating efficiently as a chemical/biological filter. Another facility in Nevada is the Pyramid Lake Indian Tribal Enterprises Hatchery. This 3000 gpm system started operating in 1989 and has shown excellent operating results as a chemical/biological filter. Spring Creek National Fish Hatchery in Washington tested clinoptilolite in 1983 and 1984 for filter media replacement of oyster shell. The clinoptilolite showed excellent results but no action has been taken to change the existing system. Areas that need to be investigated and require further study are:
Source: D.E. Owsley, Annual AFS Meeting - August 19947 -------------------------------------------------------------------------------------------------- For years consumers and experts alike have recognized that the flavor and eating quality of many saltwater fishes differs greatly from freshwater fish, and a significant number of consumers prefer ocean fish. The reasons for the differences in flavors between saltwater and freshwater fish have not been understood until recently because little scientific information on fish flavors was available. However, researchers in the UW-Madison Food Science Department, helped by funding from the UW Sea Grant Institute, have recently made great strides in understanding the basic chemistry of fish and seafood flavors. Working with the UW-Madison Aquaculture Program, researchers have devised and tested initial strategies for improving the flavors of freshwater fish and shellfish by incorporating marine- associated compounds into the diets of trout, crayfish and catfish. Researchers at the UW hypothesized that bromophenols at very low concentrations (parts per billion) might play a role in the presence of the desirable flavors of ocean-caught fish and shellfish. Chemical analyses of samples of freshwater and ocean-caught fish and seafood from around the world revealed that bromophenols were present in all marine species, but were not found in freshwater species. Follow-up taste panels revealed that various combinations of bromophenols in fish and seafood were responsible for the desirable rich, sea-like, briny, and iodine-like flavors of ocean-grown species. Using salmon as a model, researchers showed that a fish's diet was the key factor in whether bromophenols occurred in the fillets. Species of Pacific salmon grown in the Great Lakes lacked the rich sea-like flavor found in prime, actively feeding salmon from the Pacific Ocean, and analysis showed that bromophenols were present only in the ocean salmon. Bromophenols are naturally found in many marine organisms. Bromophenols are biologically synthesized from bromine in sea water and phenolic substances that are present in the organisms. Because organisms that produce bromophenols are low in the food chain, the compounds become distributed throughout marine organisms via diet. The amounts of various bromophenols that are found in ocean fish, and thus the degree of bromophenol or marine-like flavors, depend on the feeding habits of the various fish and shellfish species. Some fish, such as haddock, possess very distinct iodine-like flavors, and some, like ocean perch, exhibit much more subtle marine-like flavors. Aquacultured shrimp and prawns ingest very low concentrations of bromophenols from natural and manufactured feeds, and as a result do not possess a full, rich, flavor. On the other hand, wild Gulf of Mexico shrimp contain substantial amounts of 2,6-dibromophenol, a particularly potent flavor compound. As a result, Gulf shrimp exhibit mild, but distinct iodine-like flavors that are generally prized by consumers. UW-Madison researchers have conducted feeding trials with bromophenols on rainbow trout, freshwater crayfish, and channel catfish by incorporating both synthetic and naturally occurring bromophenols into pelleted diets at very low levels. The effects of feeding bromophenols occur very rapidly, with only three days prior to harvest being sufficient to achieve results. Feeding bromophenols to trout causes a very distinct lightening of the flesh color away from the grayish-pink tones usually present in non-pigmented trout. This results in a notably white appearance in cooked filets, and it is also sometimes accompanied by a slight softening of the flesh. The fillets of bromophenol-fed trout exhibit a rich, mild, marine-like flavor, and results from taste panels indicate that consumers definitely prefer the bromophenol-modified flavor of trout. Trials that involved feeding bromophenols to freshwater crayfish produced equally dramatic results including slightly whitened flesh and altered flavor. The characteristic crayfish flavor was transformed to a distinct lobster-like or crab-like flavor, depending on types and amounts of bromophenols incorporated into the feed. When catfish were fed bromophenols, the flavor effects were not as dramatic as for trout or crayfish, but some effects were nevertheless measured. It appears that catfish metabolically process bromophenols differently than trout or crayfish, and methods for inducing greater retention of the flavor compounds is necessary to get the desired effects. At the present time, FDA regulations would probably prohibit the use of synthetic bromophenols into aquaculture diets. Accordingly, further research is needed to find or develop a practical source of natural bromophenols for incorporation into these feeds. Natural bromophenols are found in low concentrations in fish meal and seafood processing wastes. It may be possible to develop technology for concentrating the bromophenols in these products to higher levels. Alternatively, organisms such as certain marine sandworms, which contain very high levels of bromophenols, could be harvested or cultured for use in fish feeds. Source: Wisconsin Aquaculture Update, -------------------------------------------------------------------------------------------------- Brian Tobin, Minister of Fisheries and Oceans, released a Federal Aquaculture Development Strategy developed in cooperation with industry and the provinces. The strategy is devised to help Canada realize its potential to become a world leader in aquaculture. The object of the aquaculture strategy is to create an economic and regulatory environment in which aquaculture can prosper, while at the same time continuing to ensure environmental integrity. Canadian aquaculture is at an important juncture. In 1993 Canada ranked 27th in the world and accounted for less than one-third of one percent of global production. Advantages are internationally recognized technical and aquaculture management expertise, state- of-the art facilities for the production of high quality cultured fish and seafood, and a geographical setting that gives easy access to the huge North American and Pacific Rim fish and seafood markets. In short, the industry has terrific potential to expand and generate wealth and jobs, particularly in coastal and rural communities with limited economic alternatives. If aquaculture develops effectively it can create more than 6,000 new jobs in the industry in the next five years. Canadian aquaculture production generates more than $289 million in annual revenue; the supplies and services sector generates an additional $266 million. The industry employs 5,200 Canadians - 2,800 in aquaculture production and 2,400 in supplies and services. The federal strategy is based on partnerships between industry and all levels of government. There have been extensive consultations with stakeholders and this strategy provides a game plan for maximizing the sustainable use of aquatic resources. The strategy recognizes aquaculture development as a priority of the federal government and says it will be given specific policy and developmental considerations. "Government will create a climate in which aquaculture can flourish," the strategy says. However, it also recognizes that aquaculture is a private sector initiative: "The principal responsibility for commercial development will rest with the industry." The Department of Fisheries and Oceans will be the lead federal agency in implementing the strategy. The core implementation teams for the strategy are industry-government Aquaculture Implementation Committees. They will be based in the provinces and territories and will have representation from industry associations, academia, and all relevant federal, provincial and territorial agencies and departments. These committees will work together to identify developmental constraints, and to quickly assemble the expertise, technology and resources needed to produce solutions. The strategy describes the federal role in aquaculture development under several components including research, technology transfer, training and development, regulatory framework, environmental sustainability and interaction, resource allocation and access, product safety and inspection, market intelligence and services, access to financing, communications, performance measurement and improvement, and implementation structure. -------------------------------------------------------------------------------------------------- Please note these addess changes: Ronald Kinnunen John McKinney |