Monday, June 29, 2009
Learn How to care for your fish aquarium"s filter.
Having an aquarium in your house or your office can be a good conversation starter. With the proper marine aquarium you can feature some of the most exotic pets that individuals will ever have a chance. I have been fortunate enough to have looked at some fish tanks that are so that they have a mixture of small sharks, starfish, shrimp, and many other types of fish.The only thing that can detract from how exquisite and special these tanks are is how dirty they can become. The larger the aquarium the more upkeep it calls for. Your fish cannot live in an environment that is constantly dirty and no one cares to look at that. In order to keep things clean you have to purchase a filter that will take out the waste and bacterium from the water inside of the aquarium.Filters can only do so much until they are totally full and do not have the capability to maintain anymore waste. So how are you able to clean an aquarium filter? This answer depends solely on the type of filter that you are employing.Numerous people will utilize chemical filters - which works to take away coloration and odors from the aquarium water. The easiest way to spot when to clean a chemical filter is when the color of the water is starting to darken and when there is a overwhelming scent coming from the direction of the tank. It may be a solid month before this stops working the way it should.Mechanical filters employ sponges and pads. The more fish that are in the tank the greater amount of waste there is. This means you will have to take out these sponges and clean them. It is better to rinse off the sponges twice a month with the fish tank water. This serves to make sure that the good bacterium is not altogether removed from the tank.
Saturday, June 27, 2009
Want to catch more Fish?-think like fish.
Yes, you can leave your fish catching success to chance, but if you want to catch more fish, you must learn how to think like the fish you are trying to catch. Consistent success and fishing enjoyment is more than just baiting up your hook, casting it out and waiting for the fish to bite. This one basic premise will improve your fish catching ability and will set you apart from the fishing novices. How do you think the fishing pros are able to consistently catch fish when other fishermen do nothing but drown their bait? They use the same fishing tackle, rods and reels, fishing lures and live bait as everyone else, but they always catch more fish.
You will catch more fish!
That little teaser should have caught your attention. However, learning how to put this technique into practice takes time, patience and persistence.
Let us start at the beginning. How do you learn to think like a fish? For starters, pick one of your favorite target fish species and begin to learn everything you can about that fish. It is important to understand things like, how it feeds, how it moves around each day, what are its migratory and breeding patterns, what kind of habitat it prefers, what type of fish or food source it feeds on, just to name a few. Also important to understand is how the current, tides and moon phases effect your target fish species' activities and habits.
One way to start learning how to catch more fish, is to learn how to find your target fish species under any circumstances. Visit your local fishing tackle and bait stores. Get to know these people, because often they will have a broad knowledge of the fishing in that area. They can be a great source of fishing knowledge and how-to tips of not only learning where to fish, but also the why and how of locating fish. Instead of just asking them where the best fishing spots are, also ask questions about your targeted fish species. Try to learn what makes the fish tick, and what are it basics habits and tendencies. You will be amazed at how willing most of these folks are to share their expertise, especially if you are returning the favor and patronizing their store.
The next thing to do is to go fishing. Prepare yourself ahead of time with the proper fishing tackle, lures, bait and a notepad. Start in an area known to hold your targeted fish, and make notes about the current conditions; including, the date, time, wind direction and speed, temperature, tidal flow, water conditions and any other specific notes you feel like making. The most important thing is to start thinking like the fish you want to catch. Ask yourself, where would you be hiding and moving to. For example, if it is a real hot summer day, and the current is slack, and a low tide, the fish may not be up on the shallow flats. They may be looking for cooler water, so they may have moved to some deeper pot holes, or slid off a ridge or shallow bank and eased into deeper waters. Keep looking and when you find the fish, make more notes. The old saying that practice makes perfect is certainly true when it comes to catching more fish consistently.
To help you along, learn your local fishing waters and fishing grounds. Locate the 'fishy' areas and mark them on your GPS unit. If you do not have a GPS, then buy a nautical chart, or fishing chart. Locate shoreline points, eddys, potholes, sandbars, oyster bars, rock piles and submerged structures, and over time you will learn which places to go to depending upon the current conditions you are faced with, and that will make all the difference in your fishing world.
Learning how to think like a fish will make you a more complete and competent fisherman and angler, and will make your fishing outings with friends and family a lot more enjoyable
You will catch more fish!
That little teaser should have caught your attention. However, learning how to put this technique into practice takes time, patience and persistence.
Let us start at the beginning. How do you learn to think like a fish? For starters, pick one of your favorite target fish species and begin to learn everything you can about that fish. It is important to understand things like, how it feeds, how it moves around each day, what are its migratory and breeding patterns, what kind of habitat it prefers, what type of fish or food source it feeds on, just to name a few. Also important to understand is how the current, tides and moon phases effect your target fish species' activities and habits.
One way to start learning how to catch more fish, is to learn how to find your target fish species under any circumstances. Visit your local fishing tackle and bait stores. Get to know these people, because often they will have a broad knowledge of the fishing in that area. They can be a great source of fishing knowledge and how-to tips of not only learning where to fish, but also the why and how of locating fish. Instead of just asking them where the best fishing spots are, also ask questions about your targeted fish species. Try to learn what makes the fish tick, and what are it basics habits and tendencies. You will be amazed at how willing most of these folks are to share their expertise, especially if you are returning the favor and patronizing their store.
The next thing to do is to go fishing. Prepare yourself ahead of time with the proper fishing tackle, lures, bait and a notepad. Start in an area known to hold your targeted fish, and make notes about the current conditions; including, the date, time, wind direction and speed, temperature, tidal flow, water conditions and any other specific notes you feel like making. The most important thing is to start thinking like the fish you want to catch. Ask yourself, where would you be hiding and moving to. For example, if it is a real hot summer day, and the current is slack, and a low tide, the fish may not be up on the shallow flats. They may be looking for cooler water, so they may have moved to some deeper pot holes, or slid off a ridge or shallow bank and eased into deeper waters. Keep looking and when you find the fish, make more notes. The old saying that practice makes perfect is certainly true when it comes to catching more fish consistently.
To help you along, learn your local fishing waters and fishing grounds. Locate the 'fishy' areas and mark them on your GPS unit. If you do not have a GPS, then buy a nautical chart, or fishing chart. Locate shoreline points, eddys, potholes, sandbars, oyster bars, rock piles and submerged structures, and over time you will learn which places to go to depending upon the current conditions you are faced with, and that will make all the difference in your fishing world.
Learning how to think like a fish will make you a more complete and competent fisherman and angler, and will make your fishing outings with friends and family a lot more enjoyable
A fish farmers guide to understanding water quality.
Introduction
Importance of Water Quality in Aquaculture
Fish totally depends on water fo survival, and performs all their functions inside water.because fishes are totally dependent upon water to breathe, feed and grow, excrete wastes, maintain a salt balance, and propagate, understanding the physical and chemical qualities of water is important to successful aquaculture and fish rearing.The success of any aquaculture work, totally depends on water.
Physical qualities of Water
Water can hold big amounts of heat with a relatively small change in temperature. This heat capacity has far reaching implications. It permits a body of water to act as a buffer against wide fluctuations in temperature. The larger the body of water, the slower the rate of temperature change. Aquatic organisms take on the temperature of their environment and cannot accept suden changes in temperature. Water has very unique density qualities. Water, however, gets denser as it cools until it reaches a temperature of approximately 39ºF. As it cools below this point, it becomes lighter until it freezes (32ºF). As ice develops,water increases in volume by 11 percent. The increase in volume allows ice to float rather than sink, a characteristic that prevents ponds from freezing solid.
Far from being a "universal solvent," as it is sometimes called, water dissolves more substances than any other liquid. Over 50 percent of the known chemical elements have been found in natural waters, and it is probable that traces of most others can be found in lakes, streams, estuaries, or oceans.
Water Balance in Fish
The elimination of most nitrogen waste products in land animals is performed through the kidneys. In contrast, fish rely heavily on their gills for this function, excreting primarily ammonia. A fish's gills are permeable to water and salts. In the ocean the salinity of water is more concentrated than that of the fish's body fluids. In this environment water is drawn out, but salts tend to diffuse inward. Hence, marine fishes drink large amounts of sea water and excrete small amounts of highly salt-concentrated urine .
In fresh-water fish, water regulation is the reverse of marine species. Salt is constantly being lost through the gills, and large amounts of water enter through the fish's skin and gills This is because the salt concentration in a fish (approximately 0.5 percent) is higher than the salt concentration of the water in which it lives. Because the fish's body is contantly struggling to prevent the “diffusion” of water into its body, large amounts of water are excreted by the kidneys. As a result, the salt concentration of the urine is very low. By understanding the need to maintain a water balance in freshwater fish, one can understand why using salt during transport is beneficial to fish.
Saltwater fish drink large amounts of water and excrete small amounts of concentrated urine Freshwater fish do not drink water, but excrete large amounts of dilute urine.
Sources of Water
Water is always a limiting factor in commercial fish farming. Many of the negative chemical and environmental factors associated with most operations have their origins in the source of water selected.Quality and quantity of water availanle, determines final site selection . The most common sources of water used for aquaculture are wells, springs, rivers and lakes, groundwater, and municipal water. Of the sources mentioned, wells and springs are considered to consistently be of high quality.
Water Quantity
The beginning aquaculturist/fish farmer usually underestimates the quantity of water required for commercial production. It is generally accepted that a minimum rate of 13 gallons per minute (gpm) is required for each surface acre of ponds. With this in mind, a 100- acre fish farm will need to have wells capable of producing 1,300 gpm of water. Such large volumes are required to replace water lost to evaporation and leakage. In addition, the farmer may have several ponds to fill quickly during the spawning season. In raceway culture, it is advisable to have a minimum flow rate of 500 gpm. Even water recirculating systems that recycle water require large quantities of water. If a 100,000 gallon capacity water recirculating operation exchanges 10 percent of the water daily, it will require 10,000 gallons of water per day. The availability of subsurface groundwater in Indiana and Illinois varies widely, ranging from as little as 10 gpm or less to over 2,000 gpm from properly constructed, large diameter wells. With the exception of the aquifers located along major river drainages (usually high yields), potential yields are divided into three distinct regions:
Northern Indiana and Illinois are good to excellent and, exclusive of some areas near northwestern Indiana, yields from 200-2,000 gpm can be expected.
In the central portion of Indiana and Illinois, groundwater conditions range from fair to good.
Well yields from 100-400 gpm are typical for many large-diameter wells. Many areas of southern Indiana and Illinois lack ground-water; generally, less than 10 gpm are available from properly constructed wells. In these areas, the major sources of groundwater are present in the sand and gravel deposits of the river valley aquifers.
These yield potentials do not indicate that an unlimited number of wells can be developed in given location. Detailed studies, including exploratory drilling and test pumping, should be conducted to adequately evaluate the groundwater resource in any given area. The resultant change in the water table is produced by spheres of influence from nearby wells.
Water's Physical Factors
Temperature
After oxygen, water temperature may be the single most important factor affecting the welfare of fish. Fish are cold-blooded organisms and assume approximately the same temperature as their surroundings. The temperature of the water affects the activity, behavior, feeding, growth, and reproduction of all fishes. Metabolic rates in fish double for each 18ºF rise in temperature. Fish are generally categorized into warmwater, coolwater, and coldwater species based on optimal growth temperatures
Channel catfish and tilapia are examples of warmwater species. Their temperature range for growth is between 75-90ºF. A temperature of 85ºF for catfish and 87ºF for tilapia is considered optimum.
Walleye, and yellow perch are examples of coolwater species. Ranges for optimum growth fall between 60º and 85ºF. Temperatures in the upper end of this range are considered best for maximum growth for most coolwater species.
Coldwater species include all species of salmon and trout. The most commonly cultured coldwater species in the Midwest is rainbow trout, whose optimal temperature range for growth is 48-65ºF.
Ideally, species selection should be based in part on the temperature of the water supply. Any attempt to match a fish with less than ideal temperatures will involve energy expenditures for heating or cooling. This added expense will subsequently increase production costs.
Temperature also determines the amount of dissolved gases (oxygen, carbon dioxide, nitrogen, etc.) in the water. The cooler the water the more soluble the gas. Temperature plays a major role in the physical process called thermal stratification As mentioned earlier, water has a high-heat capacity and unique density qualities. Water has its maximum density at 39.2ºF. In spring, water temperatures are nearly equal at all pond depths. As a result, nutrients, dissolved gases, and fish wastes are evenly mixed throughout the pond. As the days become warmer, the surface water becomes warmer and lighter while the cooler-denser water forms a layer underneath. Circulation of the colder bottom water is prevented because of the different densities between the two layers of water. Dissolved oxygen levels decrease in the bottom layer since photosynthesis and contact with the air is reduced. The already low oxygen levels are further reduced through decomposition of waste products, which settle to the pond bottom. Localized dissolved oxygen depletion poses a very real problem to the fish farmer.
In spring, temperatures and dissolved oxygen are uniform throughout the pond. During the summer, stratification may occur and create an upper layer of water with high-dissolved oxygen and lower layer with low-dissolved oxygen. After a rain or when a phytoplankton die-off occurs the water may turnover.
Summer stratification is a greater problem for fish raised in deeper farm ponds. Stratification may last for several weeks. This condition may develop into a major fish kill when sudden summer rains occur. These rains will cool the warmer upper layer of water enough to allow it to mix with the oxygen poor layer below. Decomposing materials in the oxygen-poor layer are again mixed evenly throughout the pond, resulting in an overall reduction in the dissolved oxygen level. Fish previously able to avoid the oxygen depleted layer are now susceptible to low-dissolved oxygen syndrome and possibly death.
Ice is another physical factor directly related to temperature. Normally, ice cover does not impede photosynthesis. Fish consume less oxygen at colder temperatures, greatly reducing the overall oxygen demand. But fish can still suffer from low-dissolved oxygen under snow covered ice. Under extended ice cover, other gases (carbon dioxide, hydrogen sulfide, methane, etc.) can build up to dangerously high levels. Mechanical aeration is probably the most reliable way of preventing an ice buildup by keeping large areas of the pond free of ice.
Suspended Solids
Suspended solids is a term usually associated with plankton, fish wastes, uneaten fish feeds, or clay particles suspended in the water. Suspended solids are large particles which usually settle out of standing water through time. Large clay particles are an exception. Clay particles (which will be discussed again) are kept in suspension because of the negative electrical charges associated with them.
Plankton
Turbidity caused by phytoplankton (microscopic plants) and zooplankton (microscopic animals) is not directly harmful to fish. Phytoplankton (green algae) not only produces oxygen, but also provides a food source for zooplankton and filter feeding fish/shellfish. Phytoplankton also uses ammonia produced by fish as a nutrient source. Zooplankton is a very important food source for fry and fingerlings such as hybrid striped bass and yellow perch. However, excessive amounts of algae can lead to increased rates of respiration during the night thereby consuming extra oxygen. Excessive phytoplankton buildups or "blooms" which subsequently die will also consumes extra oxygen. Any wide swings between day and night oxygen levels can lead to dangerously low oxygen concentrations.
Fish wastes
Suspended fish wastes are a serious concern for water recirculating culture systems. Large amounts of suspended and settleable solids are produced during fish production. As a rule, one pound of fish waste is produced for every pound of fish produced. Fish waste particles can be a major source of poor water quality since they may contain up to 70 percent of the nitrogen load in the system. These wastes not only irritate the fish's gills, but can cause several problems to the biological filter. The particulate waste can clog the biological filter, causing the vitrifying bacteria to die from lack of oxygen. Particulate waste can also promote the growth of bacteria that produces--rather than consumes ammonia.
Most clay turbidity problems are the result of exposed soil on the pond levee, exposed watershed, crayfish activity, or feeding of bottom dwelling species such as carp and catfish. Turbidity levels exceeding 20,000 ppm can cause behavioral changes in fish. In natural bodies of water, turbidity values seldom exceed these critical levels. Even "muddy looking" ponds rarely have concentrations greater than 2,000 ppm. Turbidity caused by clay or soil particles, however, can restrict light penetration and limit photosynthesis. Sedimentation of soil particles may also smother fish eggs and destroy beneficial communities of bottom organisms such as bacteria. Removal of clay turbidity can be accomplished by adding materials that attach to the negative charges of the clay particles, forming particles heavy enough to settle to the bottom. Common remedies for clay turbidity are 7-10 square bales of hay per surface acre, or 300-500 pounds of gypsum per surface acre. Gypsum applications may be repeated at two week intervals if ponds do not clear.
Importance of Water Quality in Aquaculture
Fish totally depends on water fo survival, and performs all their functions inside water.because fishes are totally dependent upon water to breathe, feed and grow, excrete wastes, maintain a salt balance, and propagate, understanding the physical and chemical qualities of water is important to successful aquaculture and fish rearing.The success of any aquaculture work, totally depends on water.
Physical qualities of Water
Water can hold big amounts of heat with a relatively small change in temperature. This heat capacity has far reaching implications. It permits a body of water to act as a buffer against wide fluctuations in temperature. The larger the body of water, the slower the rate of temperature change. Aquatic organisms take on the temperature of their environment and cannot accept suden changes in temperature. Water has very unique density qualities. Water, however, gets denser as it cools until it reaches a temperature of approximately 39ºF. As it cools below this point, it becomes lighter until it freezes (32ºF). As ice develops,water increases in volume by 11 percent. The increase in volume allows ice to float rather than sink, a characteristic that prevents ponds from freezing solid.
Far from being a "universal solvent," as it is sometimes called, water dissolves more substances than any other liquid. Over 50 percent of the known chemical elements have been found in natural waters, and it is probable that traces of most others can be found in lakes, streams, estuaries, or oceans.
Water Balance in Fish
The elimination of most nitrogen waste products in land animals is performed through the kidneys. In contrast, fish rely heavily on their gills for this function, excreting primarily ammonia. A fish's gills are permeable to water and salts. In the ocean the salinity of water is more concentrated than that of the fish's body fluids. In this environment water is drawn out, but salts tend to diffuse inward. Hence, marine fishes drink large amounts of sea water and excrete small amounts of highly salt-concentrated urine .
In fresh-water fish, water regulation is the reverse of marine species. Salt is constantly being lost through the gills, and large amounts of water enter through the fish's skin and gills This is because the salt concentration in a fish (approximately 0.5 percent) is higher than the salt concentration of the water in which it lives. Because the fish's body is contantly struggling to prevent the “diffusion” of water into its body, large amounts of water are excreted by the kidneys. As a result, the salt concentration of the urine is very low. By understanding the need to maintain a water balance in freshwater fish, one can understand why using salt during transport is beneficial to fish.
Saltwater fish drink large amounts of water and excrete small amounts of concentrated urine Freshwater fish do not drink water, but excrete large amounts of dilute urine.
Sources of Water
Water is always a limiting factor in commercial fish farming. Many of the negative chemical and environmental factors associated with most operations have their origins in the source of water selected.Quality and quantity of water availanle, determines final site selection . The most common sources of water used for aquaculture are wells, springs, rivers and lakes, groundwater, and municipal water. Of the sources mentioned, wells and springs are considered to consistently be of high quality.
Water Quantity
The beginning aquaculturist/fish farmer usually underestimates the quantity of water required for commercial production. It is generally accepted that a minimum rate of 13 gallons per minute (gpm) is required for each surface acre of ponds. With this in mind, a 100- acre fish farm will need to have wells capable of producing 1,300 gpm of water. Such large volumes are required to replace water lost to evaporation and leakage. In addition, the farmer may have several ponds to fill quickly during the spawning season. In raceway culture, it is advisable to have a minimum flow rate of 500 gpm. Even water recirculating systems that recycle water require large quantities of water. If a 100,000 gallon capacity water recirculating operation exchanges 10 percent of the water daily, it will require 10,000 gallons of water per day. The availability of subsurface groundwater in Indiana and Illinois varies widely, ranging from as little as 10 gpm or less to over 2,000 gpm from properly constructed, large diameter wells. With the exception of the aquifers located along major river drainages (usually high yields), potential yields are divided into three distinct regions:
Northern Indiana and Illinois are good to excellent and, exclusive of some areas near northwestern Indiana, yields from 200-2,000 gpm can be expected.
In the central portion of Indiana and Illinois, groundwater conditions range from fair to good.
Well yields from 100-400 gpm are typical for many large-diameter wells. Many areas of southern Indiana and Illinois lack ground-water; generally, less than 10 gpm are available from properly constructed wells. In these areas, the major sources of groundwater are present in the sand and gravel deposits of the river valley aquifers.
These yield potentials do not indicate that an unlimited number of wells can be developed in given location. Detailed studies, including exploratory drilling and test pumping, should be conducted to adequately evaluate the groundwater resource in any given area. The resultant change in the water table is produced by spheres of influence from nearby wells.
Water's Physical Factors
Temperature
After oxygen, water temperature may be the single most important factor affecting the welfare of fish. Fish are cold-blooded organisms and assume approximately the same temperature as their surroundings. The temperature of the water affects the activity, behavior, feeding, growth, and reproduction of all fishes. Metabolic rates in fish double for each 18ºF rise in temperature. Fish are generally categorized into warmwater, coolwater, and coldwater species based on optimal growth temperatures
Channel catfish and tilapia are examples of warmwater species. Their temperature range for growth is between 75-90ºF. A temperature of 85ºF for catfish and 87ºF for tilapia is considered optimum.
Walleye, and yellow perch are examples of coolwater species. Ranges for optimum growth fall between 60º and 85ºF. Temperatures in the upper end of this range are considered best for maximum growth for most coolwater species.
Coldwater species include all species of salmon and trout. The most commonly cultured coldwater species in the Midwest is rainbow trout, whose optimal temperature range for growth is 48-65ºF.
Ideally, species selection should be based in part on the temperature of the water supply. Any attempt to match a fish with less than ideal temperatures will involve energy expenditures for heating or cooling. This added expense will subsequently increase production costs.
Temperature also determines the amount of dissolved gases (oxygen, carbon dioxide, nitrogen, etc.) in the water. The cooler the water the more soluble the gas. Temperature plays a major role in the physical process called thermal stratification As mentioned earlier, water has a high-heat capacity and unique density qualities. Water has its maximum density at 39.2ºF. In spring, water temperatures are nearly equal at all pond depths. As a result, nutrients, dissolved gases, and fish wastes are evenly mixed throughout the pond. As the days become warmer, the surface water becomes warmer and lighter while the cooler-denser water forms a layer underneath. Circulation of the colder bottom water is prevented because of the different densities between the two layers of water. Dissolved oxygen levels decrease in the bottom layer since photosynthesis and contact with the air is reduced. The already low oxygen levels are further reduced through decomposition of waste products, which settle to the pond bottom. Localized dissolved oxygen depletion poses a very real problem to the fish farmer.
In spring, temperatures and dissolved oxygen are uniform throughout the pond. During the summer, stratification may occur and create an upper layer of water with high-dissolved oxygen and lower layer with low-dissolved oxygen. After a rain or when a phytoplankton die-off occurs the water may turnover.
Summer stratification is a greater problem for fish raised in deeper farm ponds. Stratification may last for several weeks. This condition may develop into a major fish kill when sudden summer rains occur. These rains will cool the warmer upper layer of water enough to allow it to mix with the oxygen poor layer below. Decomposing materials in the oxygen-poor layer are again mixed evenly throughout the pond, resulting in an overall reduction in the dissolved oxygen level. Fish previously able to avoid the oxygen depleted layer are now susceptible to low-dissolved oxygen syndrome and possibly death.
Ice is another physical factor directly related to temperature. Normally, ice cover does not impede photosynthesis. Fish consume less oxygen at colder temperatures, greatly reducing the overall oxygen demand. But fish can still suffer from low-dissolved oxygen under snow covered ice. Under extended ice cover, other gases (carbon dioxide, hydrogen sulfide, methane, etc.) can build up to dangerously high levels. Mechanical aeration is probably the most reliable way of preventing an ice buildup by keeping large areas of the pond free of ice.
Suspended Solids
Suspended solids is a term usually associated with plankton, fish wastes, uneaten fish feeds, or clay particles suspended in the water. Suspended solids are large particles which usually settle out of standing water through time. Large clay particles are an exception. Clay particles (which will be discussed again) are kept in suspension because of the negative electrical charges associated with them.
Plankton
Turbidity caused by phytoplankton (microscopic plants) and zooplankton (microscopic animals) is not directly harmful to fish. Phytoplankton (green algae) not only produces oxygen, but also provides a food source for zooplankton and filter feeding fish/shellfish. Phytoplankton also uses ammonia produced by fish as a nutrient source. Zooplankton is a very important food source for fry and fingerlings such as hybrid striped bass and yellow perch. However, excessive amounts of algae can lead to increased rates of respiration during the night thereby consuming extra oxygen. Excessive phytoplankton buildups or "blooms" which subsequently die will also consumes extra oxygen. Any wide swings between day and night oxygen levels can lead to dangerously low oxygen concentrations.
Fish wastes
Suspended fish wastes are a serious concern for water recirculating culture systems. Large amounts of suspended and settleable solids are produced during fish production. As a rule, one pound of fish waste is produced for every pound of fish produced. Fish waste particles can be a major source of poor water quality since they may contain up to 70 percent of the nitrogen load in the system. These wastes not only irritate the fish's gills, but can cause several problems to the biological filter. The particulate waste can clog the biological filter, causing the vitrifying bacteria to die from lack of oxygen. Particulate waste can also promote the growth of bacteria that produces--rather than consumes ammonia.
Most clay turbidity problems are the result of exposed soil on the pond levee, exposed watershed, crayfish activity, or feeding of bottom dwelling species such as carp and catfish. Turbidity levels exceeding 20,000 ppm can cause behavioral changes in fish. In natural bodies of water, turbidity values seldom exceed these critical levels. Even "muddy looking" ponds rarely have concentrations greater than 2,000 ppm. Turbidity caused by clay or soil particles, however, can restrict light penetration and limit photosynthesis. Sedimentation of soil particles may also smother fish eggs and destroy beneficial communities of bottom organisms such as bacteria. Removal of clay turbidity can be accomplished by adding materials that attach to the negative charges of the clay particles, forming particles heavy enough to settle to the bottom. Common remedies for clay turbidity are 7-10 square bales of hay per surface acre, or 300-500 pounds of gypsum per surface acre. Gypsum applications may be repeated at two week intervals if ponds do not clear.
Friday, June 26, 2009
Site selection and water quality in cage culture.
Not all ponds and quarries are suitable for cage culture of fish. Many failures in cage production have occurred because of poor site selection. Before attempting cage culture make sure the body of water chosen will support the increased biological demand placed upon it.
Site Criteria
Many different sites may be adapted to cage culture. Potential sites include lakes, reservoirs, ponds, quarries, rivers, and streams. Each state may have specific laws governing the use of “public waters.” These laws may restrict private individuals from engaging in fish farming in public waters or may require permits for use of public waters. Check with the Department of Natural Resources, Department of Fish and Wildlife, or with the Cooperative Extension Service’s fisheries (or aquaculture) specialist in your state before using public waters for cage culture. Many ponds and quarries are not suitable for culturing fish in cages. The following are criteria that should be considered before attempting cage culture in an existing pond or quarry.
The surface area should be at least one half acre and preferably an acre or larger (but should not include weed infested areas of the pond).
The pond should be at least 6 feet deep over a sizable area, and most of the pond should be more than 3 feet deep.
The pond must have good water quality and should be located where prevailing winds blow across it.
The pond should not have direct access by livestock or large numbers of livestock in the watershed.
The pond should not have a highly erodible watershed or one that allows the accumulation of large amounts of organic debris.
The water level of the pond should not fluctuate greatly (2 to 3 feet) during the summer.
The pond should not have chronic problems with aquatic weeds, surface scums, over populations of wild fish, or oxygen depletion problems.
The pond should have an all weather access road.
Pond Problems
Problems frequently arise when small ponds (less than one acre) are used for cage culture. Those problems usually center around water quality deterioration, low oxygen, ammonia or nitrite buildup, and excessive algal blooms. These problems may also occur in ponds larger than one acre but Centerare not as common. Adequate depth of the pond (6 feet or greater) is important for keeping the fish wastes away from the cage, maintaining adequate circulation through the cage, and for reducing the chance of weed encroachment around the cage. Very deep ponds are more likely to experience low dissolved oxygen problems in the summer. The characteristics of the pond’s watershed can be critical to successful cage culture. Livestock with direct access to the pond, or located in large numbers within the watershed, may cause water quality problems. Livestock wastes can overfertilize the pond leading to severe algal blooms, water quality deterioration, and eventually disaster. This is particularly true of small ponds (less than 5 acres). Livestock should be fenced out of the pond and not allowed to use the immediate pond watershed as a loafing area. As shorelines are trampled, erosion increases and ponds age prematurely. Even ponds frequented by livestock in previous years may contain large amounts of organic matter.
Highly erodible watersheds may cause turbidity/silting problems which can irritate the gills of fish and cause reduced dissolved oxygen concentrations. Watersheds where large amounts of organic matter wash into the pond can result in oxygen depletions due to rapid bacterial decomposition of the detritus. Ponds that have a greater watershed than is needed to fill and maintain the water level can also have problems. Excessively large watersheds can cause rapid temperature changes, turnovers, and associated oxygen depletions due to water exchanges after heavy rains.
Ponds that have chronic problems such as severe weed infestations, surface scums, fish kills, stunted wild fish populations, and severe water level changes during the summer are not good candidates for cage culture. These problems must be brought under control first. It may be necessary to treat chemically for weeds or to stock grass carp (check state regulations), remove wild fish, and/or renovate (rebuild) the pond. Finally, an all-weather access road to the pond is essential to the maintenance, health, and survival of the caged fish. A day or more without access to the pond could lead to a catastrophe.
Water Quality
Water quality management is a key ingredient in a successful fish operation. Most periods of poor growth, disease and parasite outbreaks, and fish kills can be traced to water quality problems. Water quality management is undoubtedly one of the most difficult problems facing the fish farmer. Water quality problems are even more difficult to predict and to manage. A more thorough discussion of water quality problems and equipment needs can be found in other Extension aquaculture publications.
Oxygen
Oxygen stress is the most frequently encountered water quality problem in cage culture of fish. The concentration and availability of dissolved oxygen (DO) are important to the health and survival of fish in cage.
Critical dissolved oxygen levels will vary depending on species being reared and with interactions with other water quality parameters; e.g., carbon dioxide, ammonia, and nitrite. In general, warm water species such as catfish and tilapia need a dissolved oxygen concentration of 4 mg/l DO (or ppm) or greater to maintain good health and feed conversion. Healthy warm water fish can tolerate 1 mg/l DO for short periods of time but will die if exposure is prolonged. Prolonged exposure to 1.5 mg/l DO causes tissue damage, and any prolonged exposure to low dissolved oxygen levels will halt growth and increase the incidence of secondary diseases, apparently by reducing the fishes’ ability to resist infection. Many parasites, diseases, and chemical agents can damage the gill filaments affecting oxygen transport across the gills. This can cause the fish to behave as though the dissolved oxygen concentration is low, when in reality the cause is a disease problem.
The concentration of dissolved oxygen in any body of water varies over time and is affected by physical, biological, and chemical factors. Physical controllers of dissolved oxygen are temperature, atmospheric pressure, and salinity. As temperature and salinity increase, and as atmospheric pressure decreases, the solubility of oxygen will decrease. Temperature is an important physical controller of dissolved oxygen. As water temperature increases 10°F the amount of oxygen that will dissolve in water decreases by approximately 10 percent. The physical transfer of oxygen between the atmosphere and water occurs across the water surface when dissolved oxygen concentrations are above or below saturation. The rate of this transfer is regulated by turbulence across the water surface.
Biological factors that affect dissolved oxygen are plant photosynthesis (both phytoplanktonic and macrophytic) and plant and animal respiration (fish, invertebrates, bacteria, etc.). Most of the oxygen in aquaculture ponds is produced by plant photosynthesis during sunlight hours. Planktonic algae (phytoplankton) usually produce the bulk of this oxygen. High densities of aquatic macrophytes (rooted underwater plants) usually reduce phytoplankton growth and water circulation and, therefore, can cause dissolved oxygen problems in cage production ponds.
Plant and animal respiration are the most important oxygen reducing processes in aquaculture ponds. Fish must compete with all other living organisms for the ponds’ available dissolved oxygen. This is particularly acute at night when plants in the pond are also consuming oxygen through the process of respiration. In most aquaculture ponds nighttime phytoplankton respiration is the major consumer of oxygen. Respiration rates are temperature driven in cold-blooded animals (i.e., fish) and plants, increasing oxygen consumption with rising temperatures. Total plant and fish biomass is also usually greatest during warm weather and high light intensity conditions. For all of these reasons, summer nights, with high water temperatures and respiration and low wind turbulence, bring most oxygen problems.
In cage culture situations, low dissolved oxygen is particularly acute because the fish are crowded into such small areas. Most fish kills, disease outbreaks, and poor growth in cage situations are directly or indirectly due to low dissolved oxygen.
Turnovers and plankton die-offs are two other situations in which dissolved oxygen levels may fall below critical levels. Turnovers occur during cold rains, heavy winds, and prolonged cold spells in summer. These conditions cause the upper oxygenated layer of water to mix with the cold oxygen- depleted layer of water on the bottom of the pond. The mixing of the two layers reduces the total dissolved oxygen in the whole pond to critical levels due to both dilution and chemical reduction. Turnovers can be particularly common in deep ponds with large watersheds.
Plankton die-offs can occur as a natural consequence of algal population dynamics due to seasonal changes in temperature, pH, light intensity, nutrients, diseases, parasites, toxins, or other factors which are not clearly understood. Plankton die-offs can also occur as a consequence of nighttime low dissolved oxygen. In this case, the density and biomass of the plankton become so great that a critical dissolved oxygen concentration is reached in the pond due to nighttime respiration demands. The plankton dies from lack of oxygen along with the fish.
Dissolved oxygen management is one of the most critical management techniques that must be learned by a fish farmer. Dissolved oxygen management includes both biological and mechanical manipulation. Biological manipulation can include fertilization and submerged aquatic plant control to maintain a healthy phytoplankton bloom. Mechanical manipulation through aeration may help maintain adequate dissolved oxygen concentrations and may save fish during chronic low DOs, turnovers, and plankton die-offs.
Temperature.
Temperature is the single most important physical factor controlling the life of a cold-blooded animal. Temperature is critical in growth, reproduction and sometimes survival. Each species of fish has an optimum temperature range for growth, as well as upper and lower lethal temperatures. Below the optimum temperature feed consumption and feed conversion decline until a temperature is reached at which growth ceases and feed consumption is limited to a maintenance ration. Below this temperature is a lower lethal temperature at which death occurs. Above the optimum temperature feed consumption increases while feed conversion declines.
pH (acidity)
pH is a measure of the relative acidity of the water. The pH in a pond fluctuates daily due to uptake and release of CO2 during photosynthesis and respiration. The pH is lowest at or near dawn and highest at mid-afternoon. The desirable range of early morning pH for fish production is from 6.5 to 9. The acid death point is a pH of approximately 4 and the alkaline death point is approximately pH 11. When the pH is outside the desirable range, fish growth is slowed, reproduction reduced, and susceptibility to disease increased. Ponds with acidic bottom muds and soft water usually are not productive fish ponds. Lime can be added to these ponds to increase the pH and alkalinity (total concentration of bases). Limed ponds have fewer pH, dissolved oxygen, and other related problems. A total alkalinity of 20 mg/l is considered the minimum concentration for a pond used in fish production.
Ammonia and Nitrite
Ammonia is the primary nitrogenous waste produced by fish from protein digestion. Mammals produce urea, which is a complex of ammonia and carbon. Any nitrogenous waste from manure runoff into the pond, inorganic fertilizer, plant decomposition, and/or uneaten feed is transformed into ammonia by bacteria in the pond. Bacteria of the genus Nitrosomonas convert ammonia into nitrite. Both ammonia and nitrite are toxic to fish. The level of ammonia toxicity depends on the species of fish, water temperature, and pH. The level of nitrite toxicity depends on the species of fish and the chloride ion concentration in the pond water. Sublethal levels of ammonia are known to cause gill and tissue damage, poor growth, and increased susceptibility to disease.
Nitrite at sublethal levels reduces oxygen transport into the fish, resulting in poor feed conversion, reduced growth, and increased susceptibility to disease. At stocking densities normally recommended for cage culture, neither ammonia or nitrite toxicity problems should be encountered. In ponds where higher density cage culture is attempted, where livestock manure can wash into the pond during rains, or where a plankton die-off has occurred, the level of ammonia (and laternitrite) may pose problems.
Turbidity(visibility)
Turbidity is the degree to which light penetrates the water. Light penetration is blocked by suspended soil, organic material , and the plankton (floating or suspended microscopic plants and animals) of the pond. Turbidity caused by suspended soil and detritus (muddy color) may reduce photosynthesis and, therefore, oxygen production. Ponds which always have a moderate amount of suspended clay (i.e., muddy) may actually prevent wild fluctuations in oxygen levels. Large quantities of suspended soil particles washed into a pond during heavy rains, however, may cause irritation and clogging of the gills which can lead to secondary diseases. In general, high concentrations of suspended soil or detritus in a pond are not desirable.
Since photosynthesis can occur only to the depth of light penetration into the pond, plankton turbidity is a measure or index of a healthy phytoplankton bloom (green color) in the pond. A healthy bloom will produce oxygen, reduce undesirable macrophytic plant growth, and reduce fish stress because of reduced visibility. Reduced visibility in ponds used for cage culture reduces stress on the fish caused by reactions to seeing people and possibly other animals in close proximity.
A healthy phytoplankton bloom (green water) is one with a Secchi disc visibility of 15 to 24 inches. Clear ponds with a visibility above 24 inches indicate a need for additional fertilization and possible liming (check with your Extension agent). Visibility of less than 12 inches indicates a plankton bloom which is too dense and may cause low dissolved oxygen problems. Visibility of less than 6 inches is critical. Low visibilities due to intense plankton blooms are usually associated with high feeding levels and may necessitate aeration and a reduction in the daily feed ration.
Site Criteria
Many different sites may be adapted to cage culture. Potential sites include lakes, reservoirs, ponds, quarries, rivers, and streams. Each state may have specific laws governing the use of “public waters.” These laws may restrict private individuals from engaging in fish farming in public waters or may require permits for use of public waters. Check with the Department of Natural Resources, Department of Fish and Wildlife, or with the Cooperative Extension Service’s fisheries (or aquaculture) specialist in your state before using public waters for cage culture. Many ponds and quarries are not suitable for culturing fish in cages. The following are criteria that should be considered before attempting cage culture in an existing pond or quarry.
The surface area should be at least one half acre and preferably an acre or larger (but should not include weed infested areas of the pond).
The pond should be at least 6 feet deep over a sizable area, and most of the pond should be more than 3 feet deep.
The pond must have good water quality and should be located where prevailing winds blow across it.
The pond should not have direct access by livestock or large numbers of livestock in the watershed.
The pond should not have a highly erodible watershed or one that allows the accumulation of large amounts of organic debris.
The water level of the pond should not fluctuate greatly (2 to 3 feet) during the summer.
The pond should not have chronic problems with aquatic weeds, surface scums, over populations of wild fish, or oxygen depletion problems.
The pond should have an all weather access road.
Pond Problems
Problems frequently arise when small ponds (less than one acre) are used for cage culture. Those problems usually center around water quality deterioration, low oxygen, ammonia or nitrite buildup, and excessive algal blooms. These problems may also occur in ponds larger than one acre but Centerare not as common. Adequate depth of the pond (6 feet or greater) is important for keeping the fish wastes away from the cage, maintaining adequate circulation through the cage, and for reducing the chance of weed encroachment around the cage. Very deep ponds are more likely to experience low dissolved oxygen problems in the summer. The characteristics of the pond’s watershed can be critical to successful cage culture. Livestock with direct access to the pond, or located in large numbers within the watershed, may cause water quality problems. Livestock wastes can overfertilize the pond leading to severe algal blooms, water quality deterioration, and eventually disaster. This is particularly true of small ponds (less than 5 acres). Livestock should be fenced out of the pond and not allowed to use the immediate pond watershed as a loafing area. As shorelines are trampled, erosion increases and ponds age prematurely. Even ponds frequented by livestock in previous years may contain large amounts of organic matter.
Highly erodible watersheds may cause turbidity/silting problems which can irritate the gills of fish and cause reduced dissolved oxygen concentrations. Watersheds where large amounts of organic matter wash into the pond can result in oxygen depletions due to rapid bacterial decomposition of the detritus. Ponds that have a greater watershed than is needed to fill and maintain the water level can also have problems. Excessively large watersheds can cause rapid temperature changes, turnovers, and associated oxygen depletions due to water exchanges after heavy rains.
Ponds that have chronic problems such as severe weed infestations, surface scums, fish kills, stunted wild fish populations, and severe water level changes during the summer are not good candidates for cage culture. These problems must be brought under control first. It may be necessary to treat chemically for weeds or to stock grass carp (check state regulations), remove wild fish, and/or renovate (rebuild) the pond. Finally, an all-weather access road to the pond is essential to the maintenance, health, and survival of the caged fish. A day or more without access to the pond could lead to a catastrophe.
Water Quality
Water quality management is a key ingredient in a successful fish operation. Most periods of poor growth, disease and parasite outbreaks, and fish kills can be traced to water quality problems. Water quality management is undoubtedly one of the most difficult problems facing the fish farmer. Water quality problems are even more difficult to predict and to manage. A more thorough discussion of water quality problems and equipment needs can be found in other Extension aquaculture publications.
Oxygen
Oxygen stress is the most frequently encountered water quality problem in cage culture of fish. The concentration and availability of dissolved oxygen (DO) are important to the health and survival of fish in cage.
Critical dissolved oxygen levels will vary depending on species being reared and with interactions with other water quality parameters; e.g., carbon dioxide, ammonia, and nitrite. In general, warm water species such as catfish and tilapia need a dissolved oxygen concentration of 4 mg/l DO (or ppm) or greater to maintain good health and feed conversion. Healthy warm water fish can tolerate 1 mg/l DO for short periods of time but will die if exposure is prolonged. Prolonged exposure to 1.5 mg/l DO causes tissue damage, and any prolonged exposure to low dissolved oxygen levels will halt growth and increase the incidence of secondary diseases, apparently by reducing the fishes’ ability to resist infection. Many parasites, diseases, and chemical agents can damage the gill filaments affecting oxygen transport across the gills. This can cause the fish to behave as though the dissolved oxygen concentration is low, when in reality the cause is a disease problem.
The concentration of dissolved oxygen in any body of water varies over time and is affected by physical, biological, and chemical factors. Physical controllers of dissolved oxygen are temperature, atmospheric pressure, and salinity. As temperature and salinity increase, and as atmospheric pressure decreases, the solubility of oxygen will decrease. Temperature is an important physical controller of dissolved oxygen. As water temperature increases 10°F the amount of oxygen that will dissolve in water decreases by approximately 10 percent. The physical transfer of oxygen between the atmosphere and water occurs across the water surface when dissolved oxygen concentrations are above or below saturation. The rate of this transfer is regulated by turbulence across the water surface.
Biological factors that affect dissolved oxygen are plant photosynthesis (both phytoplanktonic and macrophytic) and plant and animal respiration (fish, invertebrates, bacteria, etc.). Most of the oxygen in aquaculture ponds is produced by plant photosynthesis during sunlight hours. Planktonic algae (phytoplankton) usually produce the bulk of this oxygen. High densities of aquatic macrophytes (rooted underwater plants) usually reduce phytoplankton growth and water circulation and, therefore, can cause dissolved oxygen problems in cage production ponds.
Plant and animal respiration are the most important oxygen reducing processes in aquaculture ponds. Fish must compete with all other living organisms for the ponds’ available dissolved oxygen. This is particularly acute at night when plants in the pond are also consuming oxygen through the process of respiration. In most aquaculture ponds nighttime phytoplankton respiration is the major consumer of oxygen. Respiration rates are temperature driven in cold-blooded animals (i.e., fish) and plants, increasing oxygen consumption with rising temperatures. Total plant and fish biomass is also usually greatest during warm weather and high light intensity conditions. For all of these reasons, summer nights, with high water temperatures and respiration and low wind turbulence, bring most oxygen problems.
In cage culture situations, low dissolved oxygen is particularly acute because the fish are crowded into such small areas. Most fish kills, disease outbreaks, and poor growth in cage situations are directly or indirectly due to low dissolved oxygen.
Turnovers and plankton die-offs are two other situations in which dissolved oxygen levels may fall below critical levels. Turnovers occur during cold rains, heavy winds, and prolonged cold spells in summer. These conditions cause the upper oxygenated layer of water to mix with the cold oxygen- depleted layer of water on the bottom of the pond. The mixing of the two layers reduces the total dissolved oxygen in the whole pond to critical levels due to both dilution and chemical reduction. Turnovers can be particularly common in deep ponds with large watersheds.
Plankton die-offs can occur as a natural consequence of algal population dynamics due to seasonal changes in temperature, pH, light intensity, nutrients, diseases, parasites, toxins, or other factors which are not clearly understood. Plankton die-offs can also occur as a consequence of nighttime low dissolved oxygen. In this case, the density and biomass of the plankton become so great that a critical dissolved oxygen concentration is reached in the pond due to nighttime respiration demands. The plankton dies from lack of oxygen along with the fish.
Dissolved oxygen management is one of the most critical management techniques that must be learned by a fish farmer. Dissolved oxygen management includes both biological and mechanical manipulation. Biological manipulation can include fertilization and submerged aquatic plant control to maintain a healthy phytoplankton bloom. Mechanical manipulation through aeration may help maintain adequate dissolved oxygen concentrations and may save fish during chronic low DOs, turnovers, and plankton die-offs.
Temperature.
Temperature is the single most important physical factor controlling the life of a cold-blooded animal. Temperature is critical in growth, reproduction and sometimes survival. Each species of fish has an optimum temperature range for growth, as well as upper and lower lethal temperatures. Below the optimum temperature feed consumption and feed conversion decline until a temperature is reached at which growth ceases and feed consumption is limited to a maintenance ration. Below this temperature is a lower lethal temperature at which death occurs. Above the optimum temperature feed consumption increases while feed conversion declines.
pH (acidity)
pH is a measure of the relative acidity of the water. The pH in a pond fluctuates daily due to uptake and release of CO2 during photosynthesis and respiration. The pH is lowest at or near dawn and highest at mid-afternoon. The desirable range of early morning pH for fish production is from 6.5 to 9. The acid death point is a pH of approximately 4 and the alkaline death point is approximately pH 11. When the pH is outside the desirable range, fish growth is slowed, reproduction reduced, and susceptibility to disease increased. Ponds with acidic bottom muds and soft water usually are not productive fish ponds. Lime can be added to these ponds to increase the pH and alkalinity (total concentration of bases). Limed ponds have fewer pH, dissolved oxygen, and other related problems. A total alkalinity of 20 mg/l is considered the minimum concentration for a pond used in fish production.
Ammonia and Nitrite
Ammonia is the primary nitrogenous waste produced by fish from protein digestion. Mammals produce urea, which is a complex of ammonia and carbon. Any nitrogenous waste from manure runoff into the pond, inorganic fertilizer, plant decomposition, and/or uneaten feed is transformed into ammonia by bacteria in the pond. Bacteria of the genus Nitrosomonas convert ammonia into nitrite. Both ammonia and nitrite are toxic to fish. The level of ammonia toxicity depends on the species of fish, water temperature, and pH. The level of nitrite toxicity depends on the species of fish and the chloride ion concentration in the pond water. Sublethal levels of ammonia are known to cause gill and tissue damage, poor growth, and increased susceptibility to disease.
Nitrite at sublethal levels reduces oxygen transport into the fish, resulting in poor feed conversion, reduced growth, and increased susceptibility to disease. At stocking densities normally recommended for cage culture, neither ammonia or nitrite toxicity problems should be encountered. In ponds where higher density cage culture is attempted, where livestock manure can wash into the pond during rains, or where a plankton die-off has occurred, the level of ammonia (and laternitrite) may pose problems.
Turbidity(visibility)
Turbidity is the degree to which light penetrates the water. Light penetration is blocked by suspended soil, organic material , and the plankton (floating or suspended microscopic plants and animals) of the pond. Turbidity caused by suspended soil and detritus (muddy color) may reduce photosynthesis and, therefore, oxygen production. Ponds which always have a moderate amount of suspended clay (i.e., muddy) may actually prevent wild fluctuations in oxygen levels. Large quantities of suspended soil particles washed into a pond during heavy rains, however, may cause irritation and clogging of the gills which can lead to secondary diseases. In general, high concentrations of suspended soil or detritus in a pond are not desirable.
Since photosynthesis can occur only to the depth of light penetration into the pond, plankton turbidity is a measure or index of a healthy phytoplankton bloom (green color) in the pond. A healthy bloom will produce oxygen, reduce undesirable macrophytic plant growth, and reduce fish stress because of reduced visibility. Reduced visibility in ponds used for cage culture reduces stress on the fish caused by reactions to seeing people and possibly other animals in close proximity.
A healthy phytoplankton bloom (green water) is one with a Secchi disc visibility of 15 to 24 inches. Clear ponds with a visibility above 24 inches indicate a need for additional fertilization and possible liming (check with your Extension agent). Visibility of less than 12 inches indicates a plankton bloom which is too dense and may cause low dissolved oxygen problems. Visibility of less than 6 inches is critical. Low visibilities due to intense plankton blooms are usually associated with high feeding levels and may necessitate aeration and a reduction in the daily feed ration.
The effect of water quality on the growth and welfare of farmed cod.
In intensive production systems with high water temperatures and a varying degree of recirculation, there will be profound changes in several water parameters. We have carried out a series of experiments where cod has been exposed to different levels of nitrogen, oxygen, ammonia and nitrite over long periods.
In one experiment growth in cod fry that were exposed to ammonia levels be tween 0.0006 and 0.18 mg/l was studied. The results show a clear tendency towards reduced growth with increas ing ammonia levels, even though the cod appears to adapt to the high levels and the differences between the groups become smaller over time .
Supersaturation with nitrogen gas is another problem that can cause reduced growth, health and survival. Research indicates, however, that cod fry weighing between 30- 55 gm are relatively tolerant to moderate nitrogen gas saturations up towards 105%. Cod larvae are more sensitive. We found a tendency towards increased mortality in groups that received 105 and 107% nitrogen supersaturation in relation to the control group.
In intensive farming, there can be periods with both undersaturation and supersaturation of oxygen in the production water. Studies indicate that cod weighing between 20-40 gm have a much poorer survival rate, growth and health when they are kept in water with only 46% oxygen saturation compared with cod that are kept at 63 and 76% saturation. We also experienced that long-term, moderate oversaturation (120%) does not have unfavourable effects on survival and weight of cod, but that oxygen levels over 210% may result in acute mortality and signs of gas bubble disease. We also observed slightly increased mortality and a number of fi sh with gas bubbles in the group that received 150% saturation. Our results indicate that cod are sensitive to poor water quality
In one experiment growth in cod fry that were exposed to ammonia levels be tween 0.0006 and 0.18 mg/l was studied. The results show a clear tendency towards reduced growth with increas ing ammonia levels, even though the cod appears to adapt to the high levels and the differences between the groups become smaller over time .
Supersaturation with nitrogen gas is another problem that can cause reduced growth, health and survival. Research indicates, however, that cod fry weighing between 30- 55 gm are relatively tolerant to moderate nitrogen gas saturations up towards 105%. Cod larvae are more sensitive. We found a tendency towards increased mortality in groups that received 105 and 107% nitrogen supersaturation in relation to the control group.
In intensive farming, there can be periods with both undersaturation and supersaturation of oxygen in the production water. Studies indicate that cod weighing between 20-40 gm have a much poorer survival rate, growth and health when they are kept in water with only 46% oxygen saturation compared with cod that are kept at 63 and 76% saturation. We also experienced that long-term, moderate oversaturation (120%) does not have unfavourable effects on survival and weight of cod, but that oxygen levels over 210% may result in acute mortality and signs of gas bubble disease. We also observed slightly increased mortality and a number of fi sh with gas bubbles in the group that received 150% saturation. Our results indicate that cod are sensitive to poor water quality
Friday, June 19, 2009
FISHING TIPS FOR BASS
-Instinctively, bass go for cover when it’s sunny, and scatter when it is cloudy. When the sun is shining, it can be expected that fish will come and bite when the lure is close to cover. This is not true for cloudy days, when they can bite anywhere.
-During autumn, cast your bait down stream. This should yield better results.
-In the Spring, position yourself in shallow waters, cast deep upstream, and use a 1/8 ounce weight.
-The ideal time for bass fishing is in the early hours of the morning, or late in the evening. These are the times when bass are on the feed. However, on cloudy days or in muddy water, bass will come out to feed in mid afternoon.
-Check the surface of the water. If it’s covered with moss, try a scent - which can serve to penetrate through the thick cover.
-There is no need for flashy colors when choosing a jig. Use only the basics, such as brownish black, or blue-ish black.
-Ideally, your worm should be suspended ninety percent of the time.
-For good results, always make sure that your hooks are sharpened. While you’re at it, check your knot on a regular basis; make sure it is tied tightly.
-It is important to learn to shake your bait, instead of dragging it. What this does is make the bass think that it is actually live bait.
-For better setting of the hook, tighten your drag.
-Although it is economical to buy in bulk, worms or tubes bought in large quantities can get smelly, even in open spaces. Keep them sealed in smaller bags, like those you buy for food storage. It is important that largemouth bass bait are stored airtight, to preserve freshness. This way, they can be kept anywhere for long periods of time. Note, our Walking Worms come in small bags of 8.
-Planning is everything. Your bass fishing trip should begin before you even reach the water. Make sure you formulate a plan. After executing that plan for an hour or two, see if it is working, and contemplate moving on to “plan B” if it is not. Pay attention to your instincts.
-Even if you have a favorite place to fish - a “sweet spot”, be sure to try new spots often.
-It is important to study a lake map and think about the season you’re in, and consider weather conditions - each time you go out to fish. Even if you are fishing on a very familiar lake, it is always important to investigate. This way, you may find a great fishing spot that you may have previously missed. A computer or various websites can also help you discern water levels, forecasts, and wind conditions.
-Don’t give up just because a bass short-strikes behind your top water bait, and you don’t connect with it. Simply cast different bait, quickly, and try again.
-Try something smaller if you have been using larger lures and have only been getting a few nips - and non-producing bites. In this sport, bigger doesn’t always mean better.
-When fishing a stump, it is important to think about the root system. This is surprising to some people, but the roots might hold more fish than the main part of the stump itself.
-When going after large fish in a lake, it is best to use strong, sturdy rods. The food in a lake is plentiful and rich, so expect to see fish weighing upwards of twelve pounds each. Lake fish (of the same species) can be many times bigger than those found in ponds and streams.
-It is a known fact that Bass are smarter then many other types of fish. They are going to try to do whatever it takes to rid themselves of that hook, so it is best to be prepared. To keep your catch on the hook, the best thing a fisherman can do is keep the fish in the water. Hold your rod with the tip pointed down, angled towards the water. Bring the fish this way as close to shore as possible, then onto dry land. Once on dry land, it will be easier to concentrate on getting the hook out of the fish’s mouth. The same principle works with boats as well. As soon as you can, scoop him in the net, and bring the fish out of the water and on to the boat.
-Before you release your bass, take a look inside of its mouth. Often, while fighting a lure in its jaw - a fish will try and throw up the contents of its stomach. By looking at this, you might be able to determine what food the fish are actively eating, and then choose a lure that will duplicate that.
-When using light lines or small hooks, make sure that you use a quality reel - one with a smooth drag system to protect again sudden surges by a fighting bass.
- On a regular basis, check your line right above the lure. Rocks, gravel, stumps, and other obstructions can quickly fray your line.
-During autumn, cast your bait down stream. This should yield better results.
-In the Spring, position yourself in shallow waters, cast deep upstream, and use a 1/8 ounce weight.
-The ideal time for bass fishing is in the early hours of the morning, or late in the evening. These are the times when bass are on the feed. However, on cloudy days or in muddy water, bass will come out to feed in mid afternoon.
-Check the surface of the water. If it’s covered with moss, try a scent - which can serve to penetrate through the thick cover.
-There is no need for flashy colors when choosing a jig. Use only the basics, such as brownish black, or blue-ish black.
-Ideally, your worm should be suspended ninety percent of the time.
-For good results, always make sure that your hooks are sharpened. While you’re at it, check your knot on a regular basis; make sure it is tied tightly.
-It is important to learn to shake your bait, instead of dragging it. What this does is make the bass think that it is actually live bait.
-For better setting of the hook, tighten your drag.
-Although it is economical to buy in bulk, worms or tubes bought in large quantities can get smelly, even in open spaces. Keep them sealed in smaller bags, like those you buy for food storage. It is important that largemouth bass bait are stored airtight, to preserve freshness. This way, they can be kept anywhere for long periods of time. Note, our Walking Worms come in small bags of 8.
-Planning is everything. Your bass fishing trip should begin before you even reach the water. Make sure you formulate a plan. After executing that plan for an hour or two, see if it is working, and contemplate moving on to “plan B” if it is not. Pay attention to your instincts.
-Even if you have a favorite place to fish - a “sweet spot”, be sure to try new spots often.
-It is important to study a lake map and think about the season you’re in, and consider weather conditions - each time you go out to fish. Even if you are fishing on a very familiar lake, it is always important to investigate. This way, you may find a great fishing spot that you may have previously missed. A computer or various websites can also help you discern water levels, forecasts, and wind conditions.
-Don’t give up just because a bass short-strikes behind your top water bait, and you don’t connect with it. Simply cast different bait, quickly, and try again.
-Try something smaller if you have been using larger lures and have only been getting a few nips - and non-producing bites. In this sport, bigger doesn’t always mean better.
-When fishing a stump, it is important to think about the root system. This is surprising to some people, but the roots might hold more fish than the main part of the stump itself.
-When going after large fish in a lake, it is best to use strong, sturdy rods. The food in a lake is plentiful and rich, so expect to see fish weighing upwards of twelve pounds each. Lake fish (of the same species) can be many times bigger than those found in ponds and streams.
-It is a known fact that Bass are smarter then many other types of fish. They are going to try to do whatever it takes to rid themselves of that hook, so it is best to be prepared. To keep your catch on the hook, the best thing a fisherman can do is keep the fish in the water. Hold your rod with the tip pointed down, angled towards the water. Bring the fish this way as close to shore as possible, then onto dry land. Once on dry land, it will be easier to concentrate on getting the hook out of the fish’s mouth. The same principle works with boats as well. As soon as you can, scoop him in the net, and bring the fish out of the water and on to the boat.
-Before you release your bass, take a look inside of its mouth. Often, while fighting a lure in its jaw - a fish will try and throw up the contents of its stomach. By looking at this, you might be able to determine what food the fish are actively eating, and then choose a lure that will duplicate that.
-When using light lines or small hooks, make sure that you use a quality reel - one with a smooth drag system to protect again sudden surges by a fighting bass.
- On a regular basis, check your line right above the lure. Rocks, gravel, stumps, and other obstructions can quickly fray your line.
Subscribe to:
Posts (Atom)
