Growth And Metabolism
Fish production is affected by the fertility of the soil in the watershed, water clarity and
color, aquatic plant densities and other fish species present in the pond.
Agriculture crops grow better in northern Missouri than in south central
Missouri. This is due to the higher soil fertility in the northern part of the state. For this
reason, ponds in northern Missouri are more likely to support larger crops of fish than
ponds further south.Stocking rates are usually based on the pond/lake's ability to provide
a natural food chain, which is directly related to the fertility of the soil in the drainage
area. The natural food chain in a pond/lake is an important key to a successful fishery.
Life in a pond is a complex, interlocked chain of plants and animals. The food supply for
fish depends upon the presence of sun and available plant nutrients (organic matter and
dissolved minerals). Nutrients stimulate growth of tiny aquatic green plants called
phytoplankton. Phytoplankton serves as a food source for microscopic animal life called
zooplankton, zooplankton then multiply and becomes food for small fish, aquatic insects
and their larvae; they, in turn, are eaten by small fingerling fish, crawfish and other larger
aquatic animals. Small fish, crayfish and insects are eaten by larger fish. Then we eat the
larger fish! Thus, the food chain is completed with continuous links extending from basic
nutrients found in the soil to adult fish and on to us.
Care of the Watershed:
The land that drains into a pond/lake is its watershed. The
ideal watershed ratio is 10 to 15 acres of land for every 1 acre of pond. A pond/lake
owner should strive to keep the watershed in grasses and trees. If this is not possible,
maintain at least a 100 foot wide buffer strip of grass in the drainage area and around the
pond/lake. Grass catches sediment before it enters the water and absorbs excess nutrients,
such as nitrogen and phosphorus, that may wash off fields, pastures or lawns. Although
fish need nutrients to grow, too many may cause aquatic plant and algae problems.
Water clarity and color:
Water clarity (clearness) in a pond/lake is very important
because sight-feeding fish must be able to see what they intend to eat. Water clarity of 2
to 4 feet is ideal. Extremely clear ponds/lakes lack the fertility needed for good fish
growth.Pond/lake water with a slight greenish tint usually produces more fish. The green
color is caused by the presence of suspended phytoplankton concentrations called
blooms.Suspended soil sediments washed into ponds/lakes after heavy rains will change
the color of the water, leaving it muddy looking Color should return to normal within a
few days as settling occurs. Unfortunately some pond/lakes never clear. As a rule of
thumb, if the pond/lake is muddy enough that a light colored object, lowered at least 2 to
3 feet under the water, can not be seen, and this condition is present most of year, the
chances of growing large sight-feeding fish is greatly reduced.
Heavy sediment loads make if difficult for sight-feeding fish to locate food and can stress
fish by irritating their gills. Chronically muddy pond/lakes restrict light penetration,
which limits photosynthesis (production of oxygen), thereby reducing overall pond
productivity. In pond/lakes where clarity is about 18 inches, the answer may be to leave
the pond/lake untreated and stock with channel catfish which do not depend on sight to
obtain their food. Because natural food production will be minimal in such an
environment, it would be advisable to feed the catfish a commercial fish food.
To have a good, well balanced fish population in a pond/lake the muddy water problem
will have to be taken care of. The first step in reducing suspended soil particles in the
water is to locate the source of the problem; soil erosion from bare soil or wave action in
shallow water may be the cause. A 50 - 100 foot wide grass strip around the pond/lake
could be the solution. Livestock watering in the pond/lake and keeping soil particles
suspended could also cause a problem and fencing off the pond may be the answer.
Muddiness due to soil type and water chemistry is the most difficult to correct.
Usually the fine suspended clay particles found in muddy water have a negative charge
which keeps them in suspension. Organic matter usually has a positive charge which
attracts and binds the suspended particles together and helps them settle to the bottom.
A simple test is to collect a sample of water from the pond/lake and place it in a clean
glass one gallon jar. Add two tablespoons of vinegar to the sample. If it clears up
overnight, chances are that treatments with organic matter will probably work.
One such treatment is to place two small square bales of good, dry, green alfalfa or clover
hay, per surface acre of water, in the water along the edge in early Spring or summer.
Anchor the bales in place in shallow water. The treatment will not be effective if all the
hay is placed or blown into one corner of the pond/lake. Reapply the bales at 14 day
intervals until the water clears, but no more than four applications should be made each
year.Cottonseed meal, applied at 75 to 100 pounds per surface acre of water, has also
been used with success. More than one application of cottonseed meal may be necessary
at 14 day intervals until the water clears, but not no more than three applications is
recommended each year.In some cases, the addition of agriculture lime, up to 2 tons per
surface acre, have reduced pond/lake acidity enough to settle the soil particles. Take a
sample of the pond/lakes bottom mud, dry it and have it analyzed to determine the
alkalinity content. Most businesses that sell and spread lime for agriculture purposes have
the ability to test the sample.
Management of aquatic plants:
Rooted aquatic plants are an important component
of a pond/lake's life cycle. They help keep the water oxygenated, provide food, cover and
nesting sites. They reduce shoreline erosion and provide homes and food for a variety of
aquatic insects. These insects and their larvae are important food sources for fish and
other aquatic animals. Fish growth for a variety of species is enhanced when aquatic
vegetation is managed at moderate levels. Ideally, aquatic plants should cover 15 to 20%
of a pond/lake's bottom and surface. Conversely, too many aquatic plants are not good
either. Besides making fishing difficult, excessive vegetation may provide too much
cover for baitfish, which reduces the availability of food for predator fish and could result
in an over population of one or more species of fish. A pond owner has three options for
controlling aquatic vegetation; mechanical, chemical and biological. Mechanical is time
consuming and chemical treatments are usually expensive but both work well for spot
treating in a specific area. Introducing grass carp as a biological control can generally
reduce vegetation throughout the pond/lake. Sometimes the best solution for managing
aquatic vegetation is a combination of two or all three controls. If grass carp are used as
the primary control of vegetation, keep stocking rates conservative to avoid total
eradication of aquatic plants.
Fish species present:
Most stocking strategies require predator fish to keep
reproduction in balance, especially if the stocking objective is to grow large fish.
Largemouth bass is usually the recommended predator fish for stocking in Missouri
pond/lakes. Its reputation as a sport fish is without rival and largemouth bass have the
ability to adapt to a wide range of water parameters.We at Country Fish Farm, LLC
understand everyone has different goals and purposes for stocking fish. We will provide
you with sound management advice and guide you so your stocking objectives will be
met. However, sometimes, its is difficult to blend several stocking objectives into one
pond. For example, it would be difficult to establish a stocking strategy for growing
several species of trophy size predator fish in a 1 acre pond because most will compete
for the same food.
Every water impoundment has a limit of how many pounds of fish
it can produce naturally. This is referred to as the carrying capacity. The carrying
capacity can be altered and depends on the level of management one is willing to apply to
meet specific stocking objectives. The manipulation of fish, the habitat or both is
called management. The lowest level of management is the production of fish based upon
a pond/lake's natural carrying capacity. Production can be increased by supplementing
the food chain, such as feeding a commercial fish feed and/or providing increased oxygen
through aeration for higher demands and so on.
Supplemental feeding to increase growth rates of fish is
highly recommend, especially in the Ozark portions of southern Missouri, where pond
fertility is low. Supplemental feeding not only increases growth rates of fish but also
improves the condition of fish and enhances their reproduction. A feeding program that is
properly managed benefits all fish in a pond/lake, either directly or indirectly by reducing
the consumption of the natural food chain.
Good record keeping means better fishing.
There are approximately 300 - 400
thousand privately owned pond/lakes in Missouri. With this in mind, and recognizing that
governmental budgets are continuously being cut for various reasons, one could expect a
long waiting list to have a pond/lake shocked to determine the status of its fish
population. Research has also indicated that shocking several spots in a water
impoundment to determine the condition of a fish population is not as precise as once
believed. The alternative is maintaining a good record of fish being caught. If you
supply good information about your fish population to us or to a Missouri Department of
Conservation fisheries biologist, he/she will be able to prescribe recommendations to
improve your fish population and provide specific size and harvest limits for your
pond./lake. You can keep track of the species and sizes of fish caught by using the "Good
Record Keeping Means Better Fishing" aquaguide, which is available upon request from
most Missouri Department of Conservation Offices.
Metabolism can be described as the collective term for the chemical processes that
give life. Metabolism uses products called metabolites that include organic food
and inorganic matter such as oxygen. Metabolism is linked to all of the other body
processes by providing energy, or by building and maintaining the structures necessary
for them to function.
There are two types of metabolism. Catabolism (pronounced ca-tab-o-lism) breaks down
the metabolites that produce energy for activity. This process releases energy by breaking
down complex molecules into simpler ones. Catabolism is also known as
destructive metabolism. Anabolism (pronounced a-nab-o-lism) uses metabolites to build
new tissue for healing, growth and reproduction. This process uses energy to construct
complex molecules from simpler ones. Anabolism is also known as
There are many similarities in fish metabolism and energy usage to that of other animals.
Some aspects are unique to animals that spend their lives "under the sea". After all, they
are depended on water for locomotion, respiration, maintaining body temperature and
blood chemistry among other things. Understanding energymetabolism and the factors
that influence it is crucial to stress management and handling of fish.
Energy metabolism that uses oxygen is called aerobic metabolism. Aerobic metabolism is
highly efficient and sustainable. Anaerobic metabolism does not require oxygen and it
quickly depletes energy reserves in the cell. Anaerobic metabolism occurs in situations
that require sudden bursts of energy such as escaping a predator.
Anaerobic metabolism is not sustainable. Fish need a continual, sufficient supply of
oxygen to balance energy supply with demand.
Energy intake from food falls into three categories. Gross Energy or GE is the total
energy released by food as measured with a calorimeter. Food can contain a high level of
GE and still not have nutritional value to an animal if that food is not in a form that the
animal can digest and utilize. The Digestible Energy or the DE of food is the amount that
is utilized and digested, minus the portion that ends up in the feces. In fish, some DE is
lost through the urine and across the gill membranes. The remaining energy actually used
by the animal is the Metabolizable Energy or ME.
Removing and/or reducing all sources of stress is essential to how fish utilize their
energy. Stress can disturb the normal physiological equilibrium or homeostasis of the
animal by forcing a reallocation of energy within its system. Any response or adaptation
to stress requires energy that could otherwise be utilized for maintaining normal body
functions such as growth, digestion, disease resistance, healing and reproduction (Barton
& Iwama, 1991).
What does metabolism in fish depend upon?
Nutrition and respiration for metabolites
Osmoregulation to provide a stable working environment
Excretion to remove useless or poisonous waste products
Energy deprivation is the central concern. Sufficient oxygen is required for cellular
energy. Without enough energy to power osmoregulation and other functions fish will
die. This can take the form of delayed mortality syndrome. A lack of sufficient oxygen or
food for fuel does not directly kill the animal; it is the lack of energy and the inability to
regain lost reserves.
Each species of fish should receive foods that immolate their natural diet as closely as
possible. It is the responsibility of the aquarist to research the dietary needs of each
animal prior to purchase. Consider the natural feeding frequency and style. Example: is
the fish a predator, grazer or planktivore?
Water surface agitation and brisk current that varies in direction is important for
maintaining a high oxygen level, removal of toxic waste and good gas exchange in our
Osmoregulation typically consumes 25 to 50% of the total metabolic energy
output in fish (Morgan & Iwama, 1999. Laiz-Carrion, et., al, 2002). Osmoregulatory
dysfunction is an inherent part of stress in fish (Harrell & Moline, 1992. Weirich et., al,
1992). Epinephrine released during the stress response increases blood flow to the gills to
provide for the increased oxygen demands of stress. The elevated blood flow to the gills
causes dilation of gill blood vessels and increased use of vessels that are normally not
used at rest. This increases the surface area of the gills that is available for gas exchange,
but in saltwater fish this also leads to accelerated ion influxes and water
losses. In freshwater fish the reverse occurs, i.e. water influx and ion losses are increased.
This is the phenomenon known as the osmorespiratory compromise (Folmar & Dickhoff,
Four important body functions are closely associated with processes in the gills:
Hydromineral control (osmoregulation)
Removal of nitrogenous waste
Two important byproducts of metabolism are carbon dioxide and ammonia. Along with
excreting wastes via digestive processes, the gills play an essential role in the removal of
useless or poisonous waste products. The gills excrete eighty to ninety percent of
nitrogenous waste. Healthy gills are essential to metabolism for normal gas exchange,
osmoregulatory balance, acid-base balance and the removal of nitrogenous wastes.
What affects the rate of metabolism in fish?
Hormones such as cortisol
Environmental conditions: temperature, salinity, oxygen level
Level of the animals activities
Size of the animal: larger fish have a lower metabolism rate per unit of weight
Age because of growth and reproduction energy costs
Health or condition: repair consumes energy
A high level of cortisol (a stress hormone) in the bloodstream increases metabolism as it
accelerates the energy demand for osmoregulation. It can also disrupt digestive processes
and feeding behaviors of fish.
The amount of oxygen available affects the rate of metabolism. Osmoregulation requires
energy provided primarily by oxygen in aerobic metabolism. Metabolism and oxygen
demand increases as the water temperature rises. At the same time, the oxygen carrying
capacity of water declines as the temperatureincreases. Large temperature changes slow
metabolic recovery and lactic acid removal (Kiefer, Currie & Tufts, 1994).
Age is a factor in metabolism, as young fish require a large portion of energy for growth.
Reproduction consumes a considerable amount of energy as well. Larger specimens will
have a slower metabolism than their smaller counterparts will. Marine fish do require a
saline environment. However, the more saline the environment is the more energy is
required in osmoregulation, thereby increasing the metabolism rate.
Species that are active swimmers consume more energy in locomotion than inactive or
sedentary fish. Keeping the lighting low and providing a sufficient amount of hiding
places can reduce activity. Avoidincreasing the metabolism rate when keeping fish in an
aquarium without a fully matured biological filter. This will help control the amount of
Fish that are ill or injured consume a portion of their energy for healing and immune
function that is not necessary for animals in good condition and health.
Compromises in the mucus/scale/skin barrier are also believed to increase the amount of
energy required in osmoregulation.