in the preferred embodiment poison bait pellets , one of which is shown in fig1 are created . the core 1 of the pellet contains the toxicant either in its solid form or , in the case of liquid toxicants , absorbed into a solid matrix , preferably common fish food . the preferred cores are commercially available feed pellets which are easily soaked in a liquid toxicant . the core may also be coated with a water resistant gel layer 2 to prevent leaching of the toxic formulation into the aqueous environment . coating may be performed by spraying or immersion or other well known methods . encapsulating or coating is well know in the art of extrusion processing where an annular concentric orifice delivers a coating to an extruded column from an enclosed central orifice . spraying or immersion are known methods . another well known method of providing water resistance is to add an hydrophobic material to the mix , e . g . a fat or oil . encapsulating the entire core is a fish - food layer 3 that may be simple fish - food but is preferably an attractant selective for the target species . the buoyancy of the poison bait pellet may be used to control its vertical displacement in the aqueous environment . lateral , as well as vertical , displacement may be controlled by feed retention devices such as 4 of fig2 . many fish feeders are commercially available . extrusion processes are known for introducing air bubbles to control specific gravity or buoyancy . in my preferred embodiment , the toxicant used was rotenone . rotenone has many advantages as a piscicide : ( 1 ) at the level of proposed use , it does not threaten mammalian species , ( 3 ) it is a natural extract of cube and derris roots and craca ? vogelii and degrades in the environment , ( 4 ) it has long been approved by the e . p . a . for fish control and , ( 5 ) it is water - insoluble , hence leaching into the aqueous environment from the bait core is virtually undetectable . negative or positive buoyancy of the poison bait pellet is controlled by the feed pellet used for the core . commercially available feed pellets that are produced by a heat extrusion process have air bubbles trapped inside them which cause the poison bait pellet to float . feed pellets made by other processes usually sink . a floating form of poison fish bait can be produced with a conventional pelleting machine . normally a pelleting machine produces feed pellets by compacting the feed . this process produces a feed pellet negatively buoyant in water . to overcome this problem , i have developed a technique that incorporates dry ice in the production of the feed . mixed with the feed , the dry ice will be trapped in the pellet as it is produced . the trapped dry ice will rapidly warm and sublimate to co2 gas , leaving microcavities in the pellet . this space of trapped air will increase the buoyancy of the pellet and allow it to float . dry ice is added at a rate of 2 - 5 % of the total feed weight . fig2 shows a feed retention device 4 floating in an aqueous environment and retaining positively buoyant poison bait pellets 5 . also shown is a feeder 6 having a timer - actuated dispenser mechanism 8 . the feeder i use is actually a commercially available turkey feeder which i have modified by adding floats 7 . at regular pre - set intervals , the dispenser mechanism 8 releases a fixed quantity of the poison bait pellets into the retention area . one of rotenone &# 39 ; s greatest advantages is its commercial availability . cube root extract having 30 - 50 percent active rotenone is readily available . in my formulations i use a rotenone resin that is produced by prentiss drug and chemical co ., inc . of floral park , n . y . and is reported to be 47 percent active rotenone . therefore , a formulation having 6 percent rotenone resin by weight will have 2 . 8 percent active rotenone by weight . finely powdered rotenone resins , when administered orally , will kill fish in the dosage range of 50 - 100 mg of resin per kilogram of fish body weight . raw powder cube root is effective in the range of 40 - 80 mg / kg . when combined with a synergist , the toxicity of rotenone is nearly doubled . preferred synergists are 2 -( 2 - ethoxyethoxy ) ethyl 3 , 4 -( methylenexioxy ) phenyl acetal of acetaldehyde , which goes by the generic name of sesamex ; 1 , 2 -( methylenedioxy )- 4 - 2 -( octylsulfinyl ) propyl ! benzene , also known as sulfoxide ; alpha - 2 - butox - yethoxy )- ethoxy !- 4 , 5 -( methylenedioxy )- 2 - propyltoluene , also known as piperonyl butoxide ; dipropyl 5 , 6 , 7 , 8 - tetrahydro - 7 - methylnaphtho 2 , 3 - d !- 1 , 3 - dioxole - 5 , 6 - dicarboxylate , also known as n - propyl isome ; 3 - alkyl - 6 - carbethoxy - 5 -( 3 , 4 - methylenedioxyphenyl ) 2 - cyclohexen - 1 - one mixed with 3 - alkyl - 5 -( 3 , 4 - methylenedioxphenyl )- 2 - cyclohexen - 1 - one , also known as piperonyl cyclonene ; and b - diethylaminoethyl diphenylpropyl acetate hcl , also known as skf - 525a . i have discovered that the killing effectiveness of rotenone is greatly increased when combined with a synergist and an adsorption agent or agents . surfactants are effective adsorption agents in that they break down the surface tension of membranes on the lining of the fish &# 39 ; s stomach and allow for greater penetration of the toxic rotenone . surfactants useful for this purpose include sorbitan derivatives , cyclodextrin , simethicone , sodium lauryl sulphate , and dioctyl sodium sulfosuccinate . also , though conventional wisdom teaches that rotenone is incompatible with alkali , i have discovered that small amounts of base ned as metal hydroxides , alkali buffer solutions such as carbonates , phosphates , acetates , borates and phthalates , or other antacids increase the effectiveness of rotenone by neutralizing the digestive acids of the target fish , thereby retarding acid hydrolysis of the toxin and aiding in the absorption ! of the toxin through the stomach lining . chelating agents have also proven successful in increasing adsorption . hydrophobic materials , such as oils , are also effective in increasing adsorption . i group all such compounds as absorption agents . effective absorption agents are sodium hydroxide , aluminum hydroxide , sodium carbonate , sodium bicarbonate , potassium hydroxide , edta ( ethylenediaminetetracetic acid ), codliver oil , mineral oils , vegetable oils and the surfactants previously mentioned . the ph of a drug or toxicant is important in determining the absorption of a toxic agent . rotenone must enter the body of the fish to kill . research has shown that rotenone will only enter the body of the fish through the gills when used as an emulsified product . to enter the body of the fish , it must be lipid soluble or , in other words , it must be soluble in the tissues of the fish . for rotenone to be lipid soluble , it must be in a non - ionic state . the ionic state of the rotenone molecule like any other is effected by the acid or base content of the environment in which it is located . so the ph of the solution is very important . conventional wisdom and 50 years of field testing show that rotenone is more effective at neutral ph values . this is because rotenone remains in the don - ionic state at neutral ph values and is , therefore , more lipid soluble . my work on rotenone as a stomach poison has shown that rotenone &# 39 ; s solubility in the gastrointestinal tract is enhanced by buffering the ph of the feed at a high ph of 8 - 10 . what this high ph buffering does is counteract the low or acidic ph of the fish stomach . this results in a more neutral ph of the gastrointestinal tract and increases the lipid solubility of the molecule and decreases the amount of rotenone needed to kill the fish . sorbitan is in a class of compound known as surfactants . surfactants decrease the surface tension of membranes and increase absorption . there are tens of thousands of surfactants that can be used . i have listed the ones that have been tested . edta is a chelating agent that binds to divalent cations . pharmacological references indicate that it functions to increase the permeability of cell membranes . by increasing the permeability of the membranes , it will act as an absorptive agent . cyclodextrine is a cyclic form of dextrin that is used as an absorptive agent . the structure of the cyclodextrine ring allows for the formation of micelles with the rotenone molecule . a micelle formed is absorbed through the stomach lining of the fish better than the rotenone molecule alone . once in the bloodstream of the fish , the micelle is easily broken and the rotenone is released to have its toxic action . the cyclodextin is also a formulation aid in that it prevents rotenone from recrystallizing in the feed , therefore , keeping the size of the rotenone particles as small as possible and increasing absorption . rotenone - cyclodextrin micelles are made by dissolving the rotenone in ethanol . the cyclodextrin is dissolved in warm water . the two liquid portions are put together in formula weight ratios that range from 3 - 1 to 1 - 1 rotenone to cyclodextrin . this is part of the entire rotenone solution that the feed is soaked in to produce the poison fish food . a typical formulation for a 300 mg core would be as follows : ______________________________________cube root resin 22 mg ( 10 mg active rotenone ) synergist 2 mgadsorption agent 7 mg______________________________________ of course , in formulations having more active rotenone , the amounts of synergist and adsorption agent are increased proportionally . these substances are dissolved in an organic solvent ( ethanol , methanol , isopropanol , acetone , or ether ) and soaked into or sprayed on commercially available feed pellets . the feed pellets are then coated with an attractant layer to form the poison bait pellet . suitable binders include gelatine , agar , kelgin ™, algin potato starch , konjack flower , gum karaya , gum guar , and cellulose gum . such binders , oils or fats may also serve to coat the pellet for water resistance , particularly if a water soluble poison is employed . kelgin ® is a trademark of merckh & amp ; co . of rahway , n . j ., a hydrophillic colloid of algin compounds extracted from brown algae . another method of creating the bait is to introduce a rotenone formulation directly into a heat extrusion process . i have determined that rotenone can withstand exposure to temperatures of 150 ° c . for more than one hour without significant degradation . this will allow for the production of floating poison fish bait with a conventional feed extruder . the heat extrusion process of floating feed production operates at a temperature range of 100 °- 129 ° c . in this type of processing , the rotenone formulation would be mixed in with the rest of the feed ingredients before the feed pellet is heat extruded to produce a floating pellet . an antioxidant is added to aid in the preservation of the rotenone - laced feed . the preferred antioxidant is ethoxyquin ( 1 , 2 - dihydro - 6 - ethoxy - 2 , 2 , 4 - trimethylquinoline ) that is approved for fish feed at a rate of 150 mg / kg of feed . the size and location of the poison bait pellets , as well as the preferred minimum quantity of active rotenone per kilogram of fish body weight , are summarized as follows : ______________________________________targetspecies poison bait aqueous minimumrotenone / kg pellet size location active______________________________________common carp 2 - 5 cm . surface 20 mg ./ kg . grass carp 2 - 5 cm . surface 10 mg ./ kg . blue gill 0 . 1 - 1 cm . bottom or surface 10 mg ./ kg . bullhead 2 - 6 cm . bottom 15 mg ./ kg . sucker 0 . 25 - 1 cm . bottom 10 mg ./ kg . tilapia 1 - 4 cm . surface 20 mg ./ kg . ______________________________________ tests have shown that it is advantageous and desirable to train fish to feed on the bait pellets . fish have a home ranging behavior where different groups of the same species respond to feeders at various locations . in a series of tests targeting sterile triploid grass carp , floating feeders were anchored 20 to 50 meters from the edge of emergent vegetation or shoreline in a lake in water depths of 1 to 3 meters . buoyant pellets were prepared with desirable food and attractant and containing everything except the toxin rotenone . the training pellets were of small nugget size and dispensed twice a day in quantities ranging from 250 to 400 grams . after the feeding response was initiated and stabilized generally requiring a period of 10 to 25 days , 125 to 300 grams of pellets containing active rotenone about 10 milligrams per kilogram bait pellets were dispensed . on the follow day the dead fish were counted using the peterson method ( ricker , w . e . 1975 computation and interpretation of biological statistics of fish populations . bulletin fishery research board of canada 191 , 382p .). recovery rates from 50 to 100 % averaging 84 % were obtained . the formula used in the peterson method is n = m × c / r where n equals the estimated number killed , and m the number marked first day , c equals number of fish collected the second day , and r number of marked fish collected the second day . the marked fish had been previously collected with landing nets , marked with fin clips and returned to the lake . non - target fish found dead during 72 trials total 16 or an average of about 1 fish in every 5 trials . no effects on non - piscine wild life were observed . species present included otter , alligator , florida soft - shell turtle , bald eagle , osprey , anhinga , black vulture , turkey vulture , sandhill crane , great blue heron , common egret , snowy egret , swallow - tale kite , common grackle , and common gallinule . grass carp and common carp both feed on the surface at a fish feeder and are typically the first and largest fish to come to the feeder in a fish population . the size of the floating poison bait pellets in the range of 2 - 5 cm . will restrict other forms of fish from feeding on the bait . both types of carp seem to prefer fish food that contains some type of bread meal . a formulation of fish feed that contains yeast or bread crumbs is a preferred attractant . blue gill frequently become a problem in fisheries when they overpopulate and do not grow to desirable size . to be selective for blue gill , the poison bait pellets are in the 0 . 1 - 1 cm . range so the smaller fish in the blue gill population will eat them . blue gills tend to feed off the bottom of the aqueous environment so a poison bait pellet that sinks is more selective for this species , but this species is also known to feed from the surface on occasion . amino acids and nucleotides can be used as attractive agents for feeds . these amino acids and nucleotides are what tell the fish through its chemo receptors in the mouth that it has a food item it can eat . so by incorporating the specific amino acids and nucleotides in the feed that blue gill know as feed items , it is possible to attract them to the feed . the preferred amino acids are betaine , proline , glycine , and the preferred nucleotides are amp ( adensine monophosphate ) and imp inosine monophosphate . bull head are bottom feeders that rely on their sense of smell to locate food . the attractant of choice is heavy fish oil , fish meal , blood meal , or beef by - products . the poison bait pellets should sink and have a relatively large size of 2 - 6 cm . sucker species are largely bottom feeders that feed on invertebrates . a soft sinking poison bait pellet of small size in a range of 0 . 5 - 1 cm . is preferred and the preferred attractant is round tubifix worms to simulate natural feeding habits . tilapia , like carp , are attracted to yeast and bread crumbs and feed at the surface . however , tilapia prefer pellets in the range of 1 - 4 cm in width . though rotenone is preferred , it is to be understood that my method of controlling fish populations is not limited to this toxin only . other known toxins are juglone , antimycin a and toxaphene , for example . it is also known that various rotenone ( metabolites ) derivatives are toxic . these include 8 &# 39 ;- hydroxyrotenolones i and ii ; 6 &# 39 ;, 7 &# 39 ;- dihydro - 6 &# 39 ;, 7 &# 39 ; dihydroxyrotenolones i and ii ; 6 &# 39 ;, 7 &# 39 ;- dihydro - 6 &# 39 ;, 7 &# 39 ; dihydroxyrotenone ; 8 &# 39 ;- hydroxyrotenone ; and rotenolones i and ii . it is to be understood that there are many variants of the described methods , apparatuses , and formulations and that the scope of the invention is to be limited only to the scope of the claims herein .
a piscicide formulation is combined with fish feed and a target species attractant to form poison oral bait pellets . the pellets are formed to a size and located in the aqueous environment of a fish population in a manner effective in selectively exterminating the target species by ingestion and not by poisoning the aqueous environment .