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Sportfish Evaluation And Management

 

By Kenneth Williams

Balanced Sportfish Ponds

A balanced pond can be described as containing a combination of fish that is self-sustaining and support a range of fish size classes. A balanced pond provides anglers with a consistent catch of harvestable sized fish over a number of years. Balanced ponds are not natural. They can only be maintained by pond owner management. In natural situations, many small but reproductively active fish are more commonly observed than the fewer but larger fish found in the balanced pond. Largemouth bass and bluegill sunfish are the most common species used to produce balanced fish populations in sportfishing ponds. This article will describe characteristics of balanced and unbalanced bass / bluegill ponds. It will describe stocking and management strategies for new or renovated ponds, and methods to assess and correct unbalanced fish populations in ponds that are already stocked with fish.

Carrying capacity

Carry capacity is the total pounds of fish a particular pond can sustainably support over time. Carrying capacity is determined by pond fertility, water clarity, aquatic plant growth, fish species present, growing season length and level of management. In Oklahoma, it varies from as little as less than 50 lb per surface acre in small, muddy livestock tanks to more than 1,000 lb per surface acre in ponds receiving regular feeding and management. Average carrying capacity in fertile Oklahoma ponds is about 300 lb per surface acre. It may be increased to 500 lb per surface acre or more with active management.

Carrying capacity can consist of any combination and size of fish. For example: The fish population of a pond with a carrying capacity of 300 lb could consist entirely of 3 inch "stunted" crappie; or better for the angler, 100 lb of largemouth bass ranging in size from 4-24 inches and 200 lb of bluegill sunfish half of which are 6+ in. in length.

Pond balance is achieved by manipulating fish populations such that carrying capacity is divided among a range of size classes including many fish large enough to provide consistent angling enjoyment over time.

Pond fertilization

Although addition of fertilizer will improve fish production and carrying capacity in some ponds, most ponds already contain excessive amounts nutrients. Excess fertility is the cause of green, phytoplankton rich water and contributes to overabundant growth of aquatic vegetation. Excess fertility also increases the possibility of low dissolved oxygen fish kills. Before adding fertilizer to a pond, contact a fisheries extension specialist or state fisheries biologist for consultation and verification that fertilizer applications will benefit your pond.

Stocking new or renovated ponds

Balance is relatively easy to achieve in a new or renovated pond that is devoid of fish. However,

before stocking fish, correct or repair any pond related problems including aquatic vegetation control, erosion control, leaks and consistently turbid or muddy water. (See related LU fact sheets for more information.) Also install a screen across the emergency spillway before stocking any new or renovated pond. (See LU fact sheet "Spillway Screen Construction" for details.)

Stocking small ponds

A balanced bass / bluegill population is difficult to maintain in ponds smaller than about ˝ surface acre. Ponds smaller than ˝ acre are best suited for stocking channel catfish only, hybrid bluegill only or a combination of both species (see table 1.).

Table. 1. Stocking rates per acre for channel catfish and hybrid bluegill at 3 levels of pond management.

Species

No Feed

Fathead Minnows

(2-3 lb/ac)

Fed Pond

3 days/week

Channel

Catfish

50-100

100-200

500-700

Hybrid Bluegill

100

250

750

*Catfish

and

Hybrid

Bluegill

50 catfish

100 HBG

75-100 catfish

200

HBG

250 catfish

500 HBG

 

* Any combination is possible, however it is important not to exceed 1,000 lb/ac total fish weight in the pond.

Restock channel catfish and hybrid bluegill when approximately half of the fish have been harvested.

Supplemental stocking with fathead minnows and/or feeding will greatly improve production in these ponds. (See LU fact sheet "Home Food Fish Production in Ponds" for details.)

Stocking ponds larger than 1/2 acre

In ponds larger than about ˝ acre, stock 500 bluegill fingerlings per acre and if desired, 100 channel catfish fingerlings per acre in the fall. Blue catfish can be substituted for channel catfish, however, blue catfish fingerlings can be difficult to find and are more expensive than the commonly available channel catfish. Blue catfish also become very large and piscivorus and do not take feed as well as channel catfish. Stock 100 largemouth bass fingerlings per acre the following spring, late April through June.

Restock channel catfish every 2-4 years as needed. Stock catfish at least 10 in. or larger to avoid bass predation.

Fish harvest

Bluegill and channel catfish can be harvested as they reach acceptable size. No bass should be harvested for 3 years following initial stocking. A no harvest period allows bass to spawn several times and produce an abundance of young in different year classes.

After 3 years, begin to harvest 25-50, 12 inch or smaller bass per acre per year. Harvest of small bass improves growth of larger ones. Do not harvest 12-18 inch bass. Return them to the pond. Protected bass prevent over harvest, insure adequate reproduction of young bass and help control the bluegill population. Bass larger than 18 inches can be harvested or returned to the pond as desired. These fish are a relatively small part of the bass population and will not affect pond balance.

Additional or alternative species

Florida strain largemouth bass

Florida-strain largemouth bass grow a little larger than our native northern largemouth bass. However, unless you are planning to raise trophy bass, the growth difference does not justify the additional cost or other disadvantages of this fish. Florida-strain bass are susceptible to winter kill in Oklahoma during hard cold snaps making Microptreus salmoides - largemouth bass their long term survival in the pond doubtful. They also are more difficult to catch which reduces fishing enjoyment for many anglers. Stock Florida or hybrid bass at the same rate recommended for native largemouth bass.

Florida-strain northern largemouth crosses are available that combine increased growth and more cold tolerance, however, their expense rarely justifies their slim growth advantage over native largemouth bass for most pond owners.

Coppernose bluegill

Coppernose bluegill is a southern strain of the common bluegill. It can be stocked separately or in combination with native bluegill at the same stocking rates given for bluegill. Coppernose bluegill grow faster during the first year of growth than our native bluegill. Thereafter, growth rates are about the same. Early increased growth rates gives coppernose bluegill a size advantage that they are able to maintain through life. Coppernose bluegill have the disadvantage of being harder to catch and souther strains are susceptible to winterkill in Oklahoma.

Hybrid striped bass

 

Hybrid striped bass are a cross between the striped bass and the white bass. Hybrid striped bass can provide the angler looking for new species with some exciting fishing experiences. These fish readily accept fish food and grow well in ponds reaching weights of 5 lb+. It is an excellent, strong and aggressive sportfish. There are two major disadvantages with this species. Fingerlings for stocking can be difficult to locate and transport. Also hybrid striped bass are easily stressed and go into shock when removed from the water. Catch and release fishing is not possible because most hybrid striped bass die soon after being caught.

Stocking rates have not been intensively evaluated, however, most ponds can support 50-100 hybrid striped bass per acre if fish are fed occasionally. Hybrid striped bass do compete with largemouth bass for forage fish.

Redear sunfish

Redear sunfish are often stocked alone or in combination with bluegill in many ponds. Redear, also known as "shell crackers" eat snails. Snails are a secondary host of black and yellow grubs found under the skin and in the flesh of fish. Stocking redear sunfish in ponds with grub infestations can help control these parasites and reduce the number of grubs found in food fish.

Redear sunfish are stocked at the same rate as bluegill or they can be stocked in combination with bluegill. Stock a number of bluegill and redear sunfish equal to the total number of bluegill (usually 500) normally stocked in the pond.

Fathead minnows

Fathead minnows provide an addition food source for channel catfish, largemouth bass and bluegill. Growth rates of most fish can be improved with addition of 3 lb of fathead minnows per surface acre. Stock fathead minnows in April or May, 1-2 months before 

stocking largemouth bass to allow time for adult fish to spawn at least one time. Fathead minnows will continue to spawn several times over the summer. Eggs are deposited on the undersides of branches, aquatic vegetation, stones or other submersed material. Old pallets or small cedar trees placed at the edges of the pond in 1-2 feet of water provide excellent spawning and refuge sites for fathead minnows.

Evaluating Established Ponds

Established ponds can remain in balance and provide excellent angling opportunity for many years with proper pond management. However, neglect and the vagaries of nature often can change pond balance and reduce fishing quality (See LU fact sheet "Challenges To Sustaining Balanced, Quality Fishing Ponds"). Pond and fish population characteristics need periodic evaluation to prevent and correct problems that reduce angling potential of the pond.

Assessing pond characteristics

Physical characteristics of the pond greatly affect fish populations. Assess characteristics of established ponds before determining fish management options. Important characteristics to note are:

Aquatic vegetation

Pond turbidity

Chemical characteristics of the water

Aquatic vegetation

Aquatic vegetation is often a problem in many ponds and has a significant impact on fish populations. Most clear ponds should have 15-20 percent of surface area covered in aquatic vegetation.

Excessive vegetation provides too much cover for forage fish such as bluegill sunfish. Largemouth bass are unable to find enough bluegill to eat in dense weed growth and consequently, do not grow well. Bass may look thin. Bluegill populations can expand resulting in large numbers of very small fish. The numerous bluegill can overwhelm nesting bass and eat most of the bass eggs. Young bass recruitment in the pond can be very low. Over time the pond becomes populated with large numbers of stunted bluegill and a few large bass.

Ponds stocked with excessive numbers of grass carp may have no aquatic vegetation. There is little or no cover for forage fish in these ponds. Bass grow rapidly at first because prey are easy to find. However, not enough forage fish survive to reproduce and maintain a stable population. Bluegill numbers decline and forage fish available to bass are reduced. Bass become thin and often stunted. (See LU fact sheet " Controlling Aquatic Vegetation With Grass Carp" for more information on weed control.)

Turbidity

Muddy ponds also affect fish growth. Largemouth bass, bluegill and other sportfish are sight feeders. Turbid water reduces their ability to find food. Turbid water also limits total pond production. Muddy water reduces light penetration necessary for plankton production. Plankton, microscopic plants and animals, form the base of the aquatic food chain. Small plankton populations result in smaller populations of all living creatures in the pond. Fish production in turbid ponds can be less than 50 lb per surface acre. Fish in muddy ponds are often thin and stunted unless the pond has been fed regularly. It is best to stock and feed only channel catfish in turbid ponds can not be cleared. (See LU fact sheet "Clearing Muddy Ponds" for detailed information.)

Chemical characteristics

In ponds with established fish populations it can be assumed that chemical characteristics of the water are within safe bounds. However, chemical composition of the water may not be optimal for fish production. Testing pond pH, alkalinity, hardness and salinity provides information useful to pond management.

Alkalinity

Alkalinity values are important to know. Alkalinity is a measure of the amount of carbonate in the water. Carbonate buffers pH and other chemical changes in the water much like an antacid tablet. When carbonate level is low (less than 20 mg/l) pH values can become very high (above pH 9) on sunny afternoons when aquatic plants are abundant. High pH levels can stress fish. Carbonate also is used during photosynthesis. When levels are low, production throughout the food chain is reduced resulting in fewer pounds of fish. Alkalinity level also must be known before algal herbicides containing copper compounds can be used safely.

Low alkalinity levels can be increased with addition of agricultural lime applied at a rate of 2,000 lb / surface acre. Scatter lime from a boat over as much of the pond as is possible.

pH

Testing pH indicates the acid or base level of the water. Pond water should have a morning ph of about 6.5 - 7.5. During periods of abundant sunshine and warm temperatures, afternoon pH can rise as high as 9-10 in ponds containing large amounts of aquatic vegetation. Values for pH below 6.5 can reduce or stop fish reproduction, ph values below 4.5 is lethal to many fish species. Values for pH are related to alkalinity. Extreme pH levels usually can be neutralized with addition of agricultural lime as indicated above. Very low pH levels may be indicate the possibility of acid mine runoff entering the pond or other abnormal situation.

Hardness

Hardness measures the amount of calcium and magnesium in the water. These minerals are needed for proper fish egg development and as necessary elements in many natural fish food organisms. Values between 50 - 400 mg/l are optimal.

Salinity

Salinity measures the level of salt (sodium and potassium chloride) in water. Ponds sited near abandon oil wells may have measurable salinity levels. During periods of prolonged rains the water table can rise and force salt water released by past drilling activity to the surface. Salt water forced to the surface can flow overland and accumulate in down stream ponds. Salinity can reach levels lethal to fish and other aquatic organisms. (See LU fact sheet "Water Quality in Sportfish Ponds" for more information.)

Assessing fish populations

In old ponds or established ponds already stocked with fish, an assessment is needed to determine the nature of the fish population. A fish population assessment consists of observation, angling and seining and will provide the pond manager with the following information:

Species of fish present in the pond

Year classes of each species

Relative abundance of each species

Fish condition

Information gained from the fish assessment can be used to determine pond balance and will indicate strategies needed to meet pond owner management objectives.

Observation

Begin the pond assessment by observing shoreline activity. Many fish can be seen in clear shallow water. Note species observed and sizes of fish. Young fish can be found at the edge of weed beds, larger fish also can be seen swimming nearby. Where weed cover is absent, small fish seek protection from predators against the shoreline in water too shallow for larger fish. Observation can indicate the presence or absence of young fish and give the pond manager an idea of their abundance. This technique is limited to relatively clear water and is of little use in muddy ponds.

Angling

Angling is the best method for assessing adult fish populations and the most enjoyable. Appropriate angling techniques can sample fish as small as 3-4 inches and as large as the biggest fish in the pond. Angling does not provide much information on abundance and species of young fish.

Assess largemouth bass populations by fishing with a range of lure sizes, 1-6 inches over the entire pond. Fish each lure size for about the same length of time. Record length and weight of each fish caught and the man hours of angling required to produce the catch.

Note the condition of fish caught. Thin fish with sunken or concave bellies and large heads are in poor condition. Healthy fish in good condition are plump and well muscled with convex, rounded bellys.

Assess bluegill using small lures or live bait and light line. Catch about 100 bluegill and record length and weight of each fish and time required to catch them.

Assess channel catfish populations by fishing with catfish baits during the evening, night or early morning hours. Record length, weight and number of fish caught per hour of fishing.

Record any other species and note numbers of these fish caught.

Seine assessment

The final portion of the pond assessment requires use of a 15 ft minnow seine. Make 3 or more seine hauls along the shallow shoreline of the pond. Note species of fish caught in the net and their abundance. An exact count is not 

necessary. Note different size classes of fish. Several size classes indicate a number of successful spawns have occurred in the pond.

Putting it all together

Information gathered from observation, angling and shoreline seine samples will provide the pond manager with a reasonably accurate fish population estimate. Management strategies to bring an established pond into balance are developed using the fish population estimate in combination with the physical assessment of the pond. Common assessment results and management options are listed in the table below.

Assessment results: - balanced fish population

Bluegill are present in several sizes from 1 in. or less to 8 in.+ in length. About 1/2 of the bluegill caught by angling are 6 in. or larger. Bass are represented by several year classes. Most bass are caught by angling and are 12-16 in. long, some may be smaller or larger. Bass and bluegill are in good condition. Channel catfish, if present are in good condition. Few or no other species are present. Bass catch rate for a competent angler, during good fishing conditions should be at least 2 fish per hour.

Assessment interpretation:

Bass are present in sufficient numbers to prevent excessive bluegill reproduction. Bluegill are available to bass in numbers that can support a healthy, sustaining, multi-age class bass population.

Management options:

No action is necessary to correct balance. Maintain pond balance by harvesting 25-50 bass, 12 in. long or less each year. Return 12-18 in. bass to the pond. Harvest bass larger than 18 in. as desired. However, if 12-18 in. bass appear to be losing body condition and becoming thin, remove 10-20 large bass from the pond annually until condition of 12-18 in. bass improves. Keep consistent pond records of catch to detect changes in fish population that may need correction. Harvest bluegill and catfish as desired.

Assessment results: - undesirable species

Numerous small bullhead catfish, common carp, bluegill, green sunfish, large golden shiners or crappie. Fish may appear thin and stunted. Few or no bass. Fish not considered a harvestable size by most anglers. Pond may or may not be muddy. Aquatic vegetation may or may not be present.

Assessment interpretation:

The pond was improperly stocked from angler catches, minnow buckets or accidents of nature. Many anglers commonly catch and stock crappie into ponds. Occasionally, good crappie fishing will result for a few years if large numbers of bass are present to control crappie reproduction. More often, crappie spawn tremendous numbers of young that compete with bass and bluegill for food. Food supply for all fish becomes scarce resulting in a pond with thousands of thin, 3 in. long crappie that are not likely to become larger.

Do not stock crappie unless you plan to intensively manage a trophy largemouth bass pond with closely controlled access to prevent bass over harvest.

Common carp and golden shiners most often enter the pond from minnow bucket releases. Carp may be mixed in with lots of wild caught minnows sold at some bait shops. Carp are bottom feeders and are a common cause of pond turbidity. Do not stock common carp.

Golden shiners can grow to a length of 10 in. or more when released into ponds devoid of bass or other predators. Large shiners are sterile and do not reproduce, however in large numbers, they can account for much of the carrying capacity of the pond. Do not stock golden shiners unless a large population of 12 inch or larger bass are present.

Bullhead catfish and green sunfish can enter ponds during heavy rain events. They are either washed downstream from ponds or streams in the watershed or swim upstream during floods, entering the pond through drain pipes or the emergency spillway. Spillway and pipe screens can prevent many of these unwanted fish from entering the pond. Bullhead catfish are particularly tolerant of poor water quality conditions and can survive low oxygen conditions that kill many other species. The bullhead is often the only species of fish found in small muddy livestock ponds. Bullhead catfish 

spawn prolifically, easily outstripping food supplies available in livestock tanks resulting in a large population of stunted fish. Do not stock green sunfish or bullhead catfish.

Other undesirable species

Flathead catfish

Avid catfish anglers occasionally stock flathead catfish into ponds. This is a mistake that can ultimately decimate most other fish species in the pond. Flathead catfish are voracious predators that grow very large and eat great quantities of fish. Most ponds can not support even a small population of flathead. Do not put this fish in your pond.

Gizzard shad

Gizzard shad are sometimes stocked into ponds as additional forage for largemouth bass. Shad reproduce in great numbers and can soon become the predominant species in the pond. Bass predation can not keep gizzard shad populations in check in small ponds. Pond balance will be upset and most other species in the pond will be adversely affected including largemouth bass. Do not stock gizzard shad in ponds smaller than 5-10 acres.

Management options:

Pond renovation using a fish toxicant such as rotenone, granulated swimming pool chlorine or complete pond draining are usually required to remove bullhead catfish and other unwanted species. Renovation also is usually the least expensive option available to control unwanted species. After renovation restock as described for new and renovated ponds above.

Another less effective method used to bring a pond of undesirable species into balance is to stock 50-100, 12 in. or larger bass per acre. Large numbers of big bass will eventually reduce populations of unwanted fish. Do not stock bass until aquatic vegetation has been reduced to 10 percent coverage using grass carp or herbicide; and turbidity problems have been corrected. Begin bass harvest when undesirable species have been reduced or eliminated from the pond. Supplemental stocking with 50-100 bluegill 4 in. or larger will be necessary 1-3 years after stocking largemouth bass. Do not stock bluegill until undesirable fish are reduced in number or eliminated.

Assessment results: - overcrowded bluegill

Many small bluegill, Most bluegill caught by angling are 3-5 in. long. few or no large bluegill, few large bass (15 in. +) few or no small bass (less than 12 in.) Aquatic vegetation may cover large areas of the pond. Bass are in good condition. Channel catfish, if present may be in thin and in poor condition.

Assessment interpretation:

Overcrowded bluegill is a situation commonly observed in heavily fished ponds. To many bass have been removed to effectively control reproduction of bluegill or other species present in the pond. The situation worsens over time because large bluegill populations reduce largemouth bass reproductive success. Most bass nests cannot be defended successfully against large numbers of invading bluegill. Bass eggs are consumed by the bluegill and consequently, young bass are not produced.

High turbidity levels or excessive aquatic vegetation can result in a similar assessment outcome.

Bass are unable to feed on bluegill because they can not see them due to turbidity, they can not find them due to excessive cover provided by aquatic vegetation or there are too many for the bass to eat.

Management options:

Eliminate excess aquatic vegetation and reduce turbidity if necessary before managing fish populations.

Option 1. Remove bluegill, usually with rotenone or another fish toxicant or drain the pond. Restock the pond as described above.

Option 2. In some ponds it is possible to remove sufficient numbers of bluegill with a seine without completely renovating the pond. If some bass are still present, supplement their numbers with 20 -30 bass per acre , 10-12 in. long. Increase bass stocking rate to 50-60 per acre in situations where few or no bass are present. Large bass are expensive to purchase. Pond renovation is usually the least expensive option. Largemouth bass may be caught by angling in other ponds or lakes and stocked into the pond. Always follow state fishing regulations when this pond stocking method is used. Legal daily catch and length limits must be observed.

Assessment results: - overcrowded bass

Many small bass ( 8-12 in.). Few small bluegill, bluegill caught by angling are large (5-10 in.) and in good condition. Very few large bass. Bass may or may not be in poor condition. Few channel catfish present. Most catfish are 9 in. or larger.

Assessment interpretation:

Bass reproduction is high and competition for food is intense. No bass harvest or over fishing large bass commonly creates this situation. Degree of over crowding can be estimated by bass condition. Greater overcrowding results in thinner bass. Trophy bluegill may be produced from this pond.

Management options:

Harvest 30-100, 12 in. or smaller bass per acre per year. Number of bass to harvest depends on severity of overcrowding. Continue to assess bass body condition. Bass condition should improve in 1-2 years. After bass condition and growth rate improve; manage the pond by harvesting 12 in. or smaller bass and returning 12-18 in. bass to the pond. Bass larger than 18 in. can be harvested or returned to the pond without affecting pond balance. Harvest bluegill and catfish if present, as desired.

Assessment results: - balanced population of multiple species

Several species of fish are present. Angling produces a catch of various species of 3-5 in. sunfish, 12 in. or larger bullhead catfish or 8 in. or larger crappie. Largemouth bass 12 in. or larger and bluegill 4 in. or larger also are caught.

Assessment interpretation:

This situation often occurs in older established ponds that receive little fishing pressure. Other species have entered the pond for a variety of reasons; usually during heavy rain and runoff events. Enough bass are present to prevent excessive reproduction from any species in the pond. This balanced situation can quickly change should bass harvest increase or natural environmental stresses reduce the bass population.

Management options:

Follow bass and bluegill management guidelines discussed above under balanced fish populations. Harvest all other species as caught.

Assessment results: - channel catfish only

Most channel catfish caught are about the same size. Some smaller catfish may be present.

Assessment interpretation:

This is a catfish pond. Some spawning may have taken place. The pond is naturally protected from invasion by other species or spillway screens are in place to control pond access.

Management options:

Channel catfish are a desirable single species in many situations; particularly in small turbid ponds. Growth and fish condition are usually very acceptable. Feeding prepared rations greatly improves growth. Improve condition of thin channel catfish by increasing harvest and/or feeding.

Largemouth bass and bluegill can be stocked in existing catfish ponds at rates given for new or renovated ponds if pond size and condition are suitable for these species. However, because 2 lb plus channel catfish are serious predators stock 4 inch or larger bluegill and 10 inch or larger largemouth bass.

To learn more about getting the most benefit from your pond, contact:

Ken Williams Fisheries Extension Specialist for The Langston University Cooperative Extension Program P.O. Box - Langston OK 73050

Phone: (405) 466-3836

email: kwilliams@luresext.edu

 

 

 

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