 Kent Coast Sea Fishing Compendium |
Amino Acid Attractants |
Food detection by fish
The primary modes of feed detection by fish are through olfaction (smell) or sight, but the taste of the item is the key factor in determining whether the item is swallowed or rejected. The current scientific consensus is that gustation is more important as a close-range chemosensory system, while olfaction is probably more effective at greater distances. There appears to be a well defined and species-specific tuning of the taste receptors of fish for the particular cues present in their feed items. In general, carnivores show the greatest positive response to alkaline and neutral substances such as the amino acids glycine, alanine, proline, arginine, taurine, valine, and betaine. The pattern is reasonable considering the chemical characteristics of the feed items the fish would seek in the natural environment. The presence of certain compounds can also act as feeding deterrents e.g. Trimethylamine or its oxidation products which are produced in decaying fish flesh cause a decrease in feed consumption in turbot and chinook salmon.
Amino acids
Proteins are composed of a number of building blocks known as amino acids. Different proteins are formed from around 23 known amino acids. Fish are incapable of synthesizing 10 amino acids totally or in sufficient quantities to meet their needs - these are referred to as essential amino acids and must be present in their original, pure form in any diet. The non-essential amino acids can be either synthesized from their basic raw materials (carbon, oxygen, hydrogen and nitrogen) or interconverted from other amino acids. There are also two uncommon amino acids - selenocysteine and pyrrolysine - found in a limited number of proteins.
| Essential Amino Acids | Non-essential Amino Acids |
|---|---|
| Arginine | Alanine |
| Histidine | Asparagine |
| Isoleucine | Aspartic Acid |
| Leucine | Cystine |
| Lysine | Glutamic Acid |
| Methionine | Glutamine |
| Phenylaline | Glycine |
| Threonine | Proline |
| Trytophan | Serine |
| Valine | Taurine |
| Tyrosine |
Combination of amino acids with their respective tastes is a key determinant for the taste of food. Relationships between amino acids and taste have been explored since the discovery of glutamate as an Umami ingredient. Umami, or "savouriness", is one of the five basic tastes together with sweet, sour, bitter, and salty. Determination of amino acids contained in foods reveals that the taste we perceive largely depends on the kinds and amounts of the amino acids.
The taste of snow crab consists of just a few kinds of amino acids, nucleic acids, and minerals (see table below). Each of them plays a role of its own. For example, arginine, though a bitter amino acid, brings out a seafood-like flavour, and the Umami of glutamate makes the crab taste like a crab.
The taste of sea urchin mainly consists of 5 amino acids (see table below). If you mix these five amino acids in the same proportions as in a living sea urchin, the taste of sea urchin can be excellently reproduced. Methionine, a very bitter amino acid, is the key ingredient for the taste of sea urchin. Without methionine, sea urchins taste like shrimps or crabs.
A lion first eats the pancreas, small intestines, and liver of its prey. These organs are delicious because they are richer in amino acids than muscle. Two or three days after the lion has left, other animals such as the hyena come to eat the muscle portions of the prey. Around that time, the meat tastes much better since muscle proteins and ATP (Adenosine triphosphate) are increasingly degraded to amino acids and nucleotides (such as inosinate and guanylate). It is also said that raw fish does not taste good when it is too fresh. The reason is the same. Umami of fish reaches its peak about 12 to 24 hours after killing because of increases in amino acid and nucleotide content.
Fish feeding stimulants
Glycine and alanine are the two most frequently cited fish feeding stimulants, being reported, respectively, in 28 (80%) and 26 (74%) of the 35 common fish species studied. Further, both glycine and alanine are stimulants in 22 species. In addition to glycine and alanine, four other substances, proline (37%), arginine (37%), betaine (34%), and histidine (23%) (each referred to as a "most frequently sited stimulant" - "MFCS") are feeding stimulants in greater than 20% of these common species. Histidine is the only MFCS represented among the six major extract components of teleost fish (20,000 species including herring, cod, mullet, dory, flatfish, bass, mackerel, whiting and wrasse). This amino acid is implicated in intracellular pH regulation in fish and does not occur as a major component in any of the invertebrate extracts.
Other MFCSs occur at very low concentrations in the fish extracts. Creatine, the dominant component in fish extracts, has never been reported as a feeding stimulant, although it acts as a feeding deterrent in the jack mackerel (Trachurus japonicus).
In molluscan extracts, four MFCSs - betaine, glycine, alanine, and proline - are represented among the top six extract components. Crustacean extracts also have four MFCSs - glycine, betaine, arginine, and proline - among their top six components. The popularity of molluscs and crustaceans as baits and feed additives and as seafoods for human consumption, is very likely related to their high concentrations of the most frequently cited feeding stimulants.
These six MFCSs are not the only known feeding stimulants. Some substances present in very low concentrations in food or baits are either major stimulants of fish species or, as is more often the case, make significant contributions to the activity of mixtures e.g. in the jack mackerel (Trachurus japonicus) tryptophan, a minor constituent of krill extract, was the only one of 20 amino acids in the extract that was a feeding stimulant.
| Effective amino acid stimuli from behavioural experiments with various fish species | |
|---|---|
| Species | Effective Feeding Stimuli |
| Sea bream (Chrysophrys major) | alanine, arginine, glutamine, glycine, proline, serine and valine |
| Herring (Clupea harengus) | alanine, aspartic acid, glutamic acid, glycine, methionine and proline |
| Cod (Gadus morhua) | alanine, arginine, glycine and proline |
| Flounder (Pseudopleuronectes americanus) | aspartic acid, betaine, GABA (gamma-Aminobutyric acid) and serine |
| Sole (Solea solea) | betaine |
Compounds
Compounds which stimulate feeding in carnivorous fish are betaine, amino acids of various kinds and inosine (a nucleoside and an important feed stimulant by itself or in combination with certain amino acids e.g. inosine and inosine-5-monophosphate have been reported as specific feeding stimulants for turbot (Scophthalmus maximus) fry). Such compounds differ between fish species and amino acids are more effective when compounded in correct combinations and concentrations as too much of one, or too little of another, can be ineffective and may even repel fish. Amino acids serine and glycine produce strong feeding stimulants in fish even at very low concentrations but alanine, arginine, taurine, aspartic acid, and cystine, produce only very low level feeding responses. Mixtures of amino acids generally produce stronger responses than individual compounds, showing that no single substance is the perfect attractant. Although glycine seems to be the basis of feeding stimulus for cod and whiting (a) it is still less attractive than natural lugworm and (b) other substances are certainly involved. In general, fresh natural bait will be better than any artificial mixture of amino acids. Until the science improves, the solution is to continue using fresh bait of the kind preferred and expected by the species you are targeting e.g. wrasse much prefer crab to fish baits.
| Species | Effective Feeding Stimuli |
|---|---|
| Sole (Solea solea) | alanine, betaine and glycine |
| Plaice (Pleuronectes platessa) | alanine, glycine, proline and taurine |
| Cod (Gadus morhua) | alanine, arginine and glycine |
| Black bream (Spondyliosoma cantharus) and Grey Mullet (Chelon labrosus) | aspartic acid, glutamic acid, lysine and serine |
| Whiting (Merlangius merlangus) | alanine and glycine |
Bait and groundbait application
Experiment by combining one or more of these six amino acids - alanine, arginine, betaine, glycine, histidine and proline - in soluble gelatine caps which can be presented in a swim feeder on their own and\or mixed with other suitable ground bait and attractants such as pilchard oil and cod liver oil capsules. These additives are olfactory (sense of smell) feeding stimulants which target a specific class of chemoreceptor site at the fishes' olfactory membranes inducing an involuntary feeding response from a broad cross-section of fish species.
Betaine hydrochloride is a fish attractant and feeding stimulant and can be added to bait mixes which have been formulated to attract the targeted fish species. Betaine hydrochloride is merely glycine betaine with a chloride counterion and, being a byproduct of the sugar industry, is usually the first crystallised form obtained after extraction from sugar beets. This substance is often called "glycine betaine" to distinguish it from other betaines.
Cod liver oil capsules are a clean way of enhancing bait but, absent any emulsifier, may only be effective during the warmer months. These capsules can be pierced on one of the hooks making up the treble on the wire trace. The capsules slowly release oil as the gelatine capsule dissolves in the water and, should a fish take the bait before the capsule has dissolved, the hook will easily strike through the capsule.
Products such as the Marukyu Power Isome (pronounced "e-sow-may") are enhanced with attractants and amino acids that attract fish because, as in the case of the Marukyu Power Isome, they look, smell, feel and taste like ragworm.
Sources of betaine, glycine, alanine, proline, histidine and arginine
| www.myprotein.com | ||
| L-Histidine | 100g | £14.29 |
| Glycine | 250g | £7.99 |
| Beta Alanine | 250g | £10.49 |
| Gelatin caps | 1,000 | £13.79 |
| www.discount-supplements.co.uk | ||
| L-arginine | 60 x 500mg Tabs | £8.95 |
| www.purepellet.co.uk | ||
| Green betaine paste powder | 250g | £1.75 |
| www.hellenia.co.uk | ||
| L-Proline Powder | 500g | £24.50 |
| www.gourmetbait.com | ||
| Pure Betaine HCL | 50g | £2.99 |
"Angling in Salt Water: A Practical Work on Sea Fishing with Rod and Line from the Shore, Piers, Jetties, Rocks and from Boats" (1887) John Bickerdyke at page 46
Ray's Liver
"Obtainable from the trawlers, and perhaps the best-known bait for large bass in or near estuaries and harbours."
"Sea-Fishing on the English Coast" (1891) Frederick George Aflalo at pages 46, 70 & 71
Chapter IV
Baits and Diary
Natural Bait
20, 21. Skate's Liver and Soft Roe of Herring. - These very soft baits require, as a rule, to be lashed to the hook. This should be done with a bit of silk, and not tied so tightly as to cut through the bait.
June
Mr. Perkin refers in his Prize Essay on Sea-Fishing to the wrasse's liver as "worth the lot put together" for bass. This is a mistake. The bait referred to is the liver of the ray, and not the wrasse, a beautiful fish that one would hesitate to describe as "an ugly flat-fish, with a long tail like that of a greyhound, minus the hair."
"Hints and Wrinkles on Sea Fishing" (1894) "Ichthyosaurus" (A. Baines & Frederick George Aflalo) at page 88
Sea Fishing near London
At Margate they use skate's liver for the bass.
"Days of my life on waters fresh and salt, and other papers" (1895) John Bickerdyke at pages 162 & 163
Angling in Salt Water
The bass is, generally speaking, more difficult to catch than the salmon, being extremely wary. He is somewhat nasty in his tastes, and when all other baits fail may occasionally be caught with a piece of dead fish which is strongly tainted.
Skate's liver, a most difficult bait to keep on the hook, he is particularly fond of; and tainted baits, in which may be included the entrails of chickens and rabbits, are especially effective in the neighbourhood of harbours frequented by fishing-boats, where a large amount of none too fresh refuse is thrown into the sea, and acts as ground bait … I was talking over this subject with a very successful bass-fisher in South Wales, who laid down so many conditions which ought to be satisfied before bass could be caught that, if his views had been absolutely correct, these fish would only find their way into the angler's creel about once in a blue moon. In the first place, said he, the water must be a little thickened by wind from the south-west. Then, it must be the period of spring tides; and, in addition, the tide must be rising, not falling, an hour before daybreak. Moreover, nothing could be caught unless it so chanced that the trawlers were bringing some skate, from which liver could be obtained for bait.
Of course these conditions were somewhat local; but, generally speaking, it may be said that the best bass-fishing is during the period of spring tides, when the water is a little coloured; and the angler should be on the warpath at daybreak.
"The Badminton Library: Modern Sea Fishing" (1895) John Bickerdyke at pages 20, 21, 106, 107, 186, 187, 188 & 320
Introductory
I met with this … fisherman … and he told me that if I would be successful with the bass of that particular place, I must wait until I could obtain certain conditions … I could not hope for success unless the trawlers had been catching skate, whose liver I was to use as bait … no one can dispute the statement that skate's liver is a first-rate bait in many places.
Ray's Liver is a noted bass bait in certain places: to wit, the mouths of harbours or the adjoining shore, where a good deal of offal from fishing boats, &c., finds its way into the sea. It is extremely unpleasant stuff to fish with, the more so as it is considered none the worse for being a little "high". A few pounds of it placed in a sack and lowered into the water from the rocks is believed to attract bass, and I have no doubt that is the case. It can be obtained from the trawlers. Ray's Skin in strips is used in the same way as mackerel skin, bass-skin, gurnard-skin, &c.
One of the most collecting ground baits he can use consists of the oily livers of fish, and particularly the entrails of pilchards. These latter, by the way, are excellent baits for many kinds of sea fish, though somewhat difficult to keep on the hook.
At night-time large bass sometimes come right into the harbour among the fishing boats and are occasionally caught, but the bait must be such a one as they would expect in such a place. Something tasty, yet not over-nice. Skate's liver a little "high"; or the inward parts of chicken or rabbit, well hung. If the water is slack, there should be no lead on the line.
A well-known bass fisher once related to me with tears in his voice how, when bass fishing, his hook being covered with skate's liver, a mullet which weighed at least 12 lbs seized his bait, ran out every yard of line, and then broke the triple gut.
While the youngsters play about in the sharp running water and perpetrate fierce onslaughts on shoals of innocent sand-eels and herring fry, the more elderly fish, as I have pointed out, coast round the rocks, and enter harbours and other places where there is plenty of refuse for them to feed upon. In such situations their tastes appear to degenerate, for they will often scornfully turn away from a delicate sand-eel presented to them alive, while a malodorous piece of oily ray's liver they will suck in greedily.
There are few baits bass will not take at times; but, as I have pointed out, where fish develop a taste for scavengering, their tastes must be pampered, and if ray's liver is not available the entrails of chicken or rabbit (if somewhat high so much the better) may often be used with success.
"Practical Letters to Young Sea Fishers" (1898) John Bickerdyke at pages 109, 138, 226 & 231
IX: Natural Baits and how to Find Them
Ray's Liver
This bait, which can rarely be obtained except from the trawlers, is in high repute for bass and large mullet. It is somewhat difficult to keep on the hook. Where bass and mullet swim close to the shore round the edge of the rocks, some of this odorous and oily substance should be placed in a small sack with a stone or two, and lowered by means of a light cord a few feet under the surface of the water. I have some reason for supposing it attracts fish.
XIII: Bottom Fishing from the Shore
Among the best baits for bass and grey mullet are skate's liver, squid, mackerel, and the larger sea worms. Bass, which feed near the mouths of harbours and the estuaries of rivers, also favour such delectable delicacies as chickens' or rabbits' interiors, and offal of various kinds.
XXI: Bass
One of the very best baits is a piece of ray's liver … and near the harbour the entrails of chicken or rabbit will often entice large bass. So also will a piece of bloater highly flavoured from long keeping.
XXII: The Mullets
About harbours, and other similar places, mullets are undoubtedly foul feeders, and are occasionally caught in or near such places on the ray's liver bait intended for bass …
"The Sportsman's Library: Sea Fishing" (1935) Major D. P. Lea Birch ("Fleur-de-Lys") at page 83
Chapter V: Bait
Ray's Liver
This is most attractive to many kinds of fish, but after a thorough trial the conclusion has been arrived at that it is not a practical proposition, for it is so soft that it is almost impossible to keep on the hook. When any happens to be available, it will serve as a valuable ingredient of the ground-bait, for if well mixed in, it will impart an attractive oiliness to the compound. No method of hardening ray's liver sufficiently to give it reasonable toughness appears to have been discovered.
"Sea Angling Modern Methods and Tackle" (1952) Alan Young at page 63
Baits
Ray's Liver
The liver of various species of ray is a good bait for bass, but it is difficult to keep on the hook in its natural state. I wrap up a piece of liver in butter muslin or cheese-cloth to make a bait the size of a golf ball.
"Bass: How to Catch Them" (1955) Alan Young at pages 50 & 51
Chapter III: Baits
Miscellaneous Baits
The flesh of the razorfish is excellent as a bass bait, but difficult to get. Strips of bacon, strips of tripe, cockles, whelks, mussels, crabs other than shore crabs, shrimps, sandhoppers, skate's liver (a golf-ball size piece in a hair-net) and a score of other baits have all accounted for bass.
"Salt-Water Angling" (1956) Michael Kennedy at pages 352 & 353
Natural Baits for Salt-Water Fish
Ray's Liver
Various species of ray - chiefly thornbacks, blondes and homelyns - form a large part of the catch of the small motor trawlers which operate from many of the smaller fishing towns and villages around our coastline.
These rays, in common with other fishes, are gutted either at sea, or on return to port; and usually the wings - the only edible portions - are cut away. The rest of the carcase and the entrails are dumped overboard - often in the harbour, despite the warning notices erected by the local authorities.
Where the carcases of rays are dumped in harbours or along the shore, bass - and mullet - are frequently seen grubbing about amongst them. In such places, the oily livers of the rays - easily obtainable, by arrangement with the fishermen - are an excellent bait for bass and mullet: though there is some evidence to show that their taste for ray's liver is an acquired one, for it is not everywhere a deadly bait.
Ray's liver is extremely soft, and as a bottom bait for bass is best cut in pieces about an inch square, each of which should be wrapped in a scrap of muslin or of an old nylon stocking - the muslin or nylon serves to keep the liver on the hook, but the oil oozes through it. When ray's liver is used as a float-fishing bait for mullet, it is best to employ a trace with a loop at each end, and to use a tapered shank size 10 treble hook whipped to a 9in length of monofilament, with a loop for attachment to the trace. To bait - using pieces of liver about the size of one's thumb nail - detach the hook link from the trace and, by means of a baiting needle (Fig X, 10) thread the hook link through the liver, and pull the treble hook into it. The hook link may then be attached to the trace.
"The Sea Angler Afloat and Ashore" (1965) Desmond Brennan at pages 188
Mullet
The list of baits on which mullet are taken is long and varied so a word or two about them will not be out of place at this point. Fish is high on the list and again the oily fishes - pilchard, herring and mackerel take pride of place. The rolls of flesh from the back of the fish makes the most durable baits but I have also had excellent fishing using the guts as well. The roe of the fish seems particularly attractive and so does the liver but it is difficult to keep on the hook. I find that if the liver is wrapped in a piece of fishnet nylon stocking … it can be kept securely on the hook.
"Modern Sea Angling" (1971) Richard Arnold at page 143
Natural Baits
Fish Baits
Other Fishes The skin of the gurnard, the ray, and even the common dogfish may be used in the same manner as the mackerel and bass lasks. Ray's liver is a favourite bait for bass in some waters, but is neither easy to obtain nor pleasant to use owing to its odoriferous properties !
"Sea Fishing For Fun" (1977) Alan Wrangles & Jack P. Tupper at page 71
5. Choosing and Storing Bait
Other baits and home-made lures
Where professional fishermen operate it is often possible to get a supply of skate or ray liver. This is a good bait for a fairly wide range of fish.
"The Bait Book" (1979) Ted Lamb at page 172
Other Baits and Oils
Fish livers
The livers of many larger fish make good legering baits for rays, flatfish, dogfish and so on. Cod and skate livers are the most easily obtained, and my fishmonger keeps them for me and charges nothing. Although rather soft, they can with care be made to stay on the hook. They also make a good attractant used in combination on the same hook with some other bait like fish strip or shellfish.
"Attractants Basics" (2003) Syed Yahiya Yacoob, A. Victor Suresh
How do Attractants Work?
Attractants release chemical signals that are received by the olfactory (smell) and gustatory (taste) receptors of the animals. These signals are then transmitted to and interpreted by the central nervous system, where they consequently elicit reactions such as movement toward the source of the signal, initiation of feeding, ingestion, and continuation of feeding. Scientists believe that in the case of olfaction, the signals are interpreted based on previous experience. Thus, one can train a fish to like or dislike a chemical signal by providing reward or punishment.
Scientists also believe that olfaction is a distant-sensor, which induces a general alert response, and there is hardly any species-specific difference in the spectrum of stimulatory substances. Therefore, signals that appeal to the olfactory sense may be important only in the initial phases of food search. In contrast, the gustatory sense is highly developed in many fish species, and considered innate and genetic in origin. In other words, we have to feed the cultured species what it likes, for we cannot train the animals to accept everything we feed them.
Amino Acids
Amino acids are the single most important group of attractants. Only free L-amino acids are effective attractants. Singly and in combination, they stimulate feeding behaviours … As indicated, the attractability of amino acids is species-specific. However, there are major differences in the effectiveness of amino acids as attractants between carnivore and herbivore aquatic species.
Although it is hard to generalize based on the evidence available, proline and glycine are known to be highly effective in carnivores, while glutamic acid is effective in herbivores. Betaine often has a synergistic interaction with amino acids in improving the attractability of feed.
Nucleotides and Nucleosides
Inosine monophosphate (IMP), adenosine diphosphate, guanine monophosphate, and uradine monophosphate (UMP) have been found effective attractants in carnivorous fish. Nucleotides also synergistically interact with amino acids. There is evidence of species specificity in the effectiveness of different nucleotides and nucleosides. UMP, but not IMP, is effective in eels; while ATP, but not AMP, is effective in lobsters.
Quaternary Ammonium Bases
Betaine and glycinebetaine are highly effective attractants in a number of aquatic species, including shrimp, pufferfish, pinfish, pigfish, red sea bream and Dover sole. The effectiveness of trimethylamine, glycyamine, and creatine is also indicated in some species … Dimethylthetin is a proven attractant in Dover sole …
Phospholipids
… The phospholipid, but not glycolipid, fraction of squid extract is an effective attractant in at least one carnivore species of fish, the yellowtail …
Biogenic Amines
Nitrogenous products that result from flesh decomposition - such as putrescine, cadaverine, tiramine, spermine, and spermidine - have long been considered potential attractants for shrimp …
Organic Acids
Citric acid, malic acid, and succinic acid are possible stimulants. Citric acid is conclusively known as a feeding stimulant or enhancer in many fish species, including carnivores. The low pH of feed itself might be a stimulant in some fish and shrimp species. However, it is not clear whether reducing the pH by inorganic acids alone would be effective.
Attractants in Aquafeeds
The aquafeed industry has long relied on ingredients that are naturally rich in attractants. Fishmeal, a major ingredient in aquafeeds, is a good source of attractants, but feed manufacturers are trying to reduce its use. Fish oil probably serves as an attractant/stimulant, as the addition of fish oil improves feed palatability.
Fish solubles are rich in free amino acids as well as nitrogenous breakdown products, so they are excellent attractants. Fish hydrolysate is also rich in free amino acids and small-chain peptides, and can be an effective attractant. Fish, however, is relatively low in glycinebetaine, a highly effective attractant/stimulant.
Marine by-products such as mollusk meal, squid meal, squid liver meal, shrimp head meal, shrimp meal, krill meal, krill hydrolysates, and Artemia are well known for their effectiveness as attractants in aquafeeds. Tubifex worms are also considered a rich source of attractants/ stimulants. Meat solubles are an effective attractant in shrimp.
Yeast and yeast hydrolysate are also considered attractants, probably due to their relatively high levels of nucleotides and nucleosides. However, brewer’s yeast acquires a bitter taste from the hops used in beer manufacturing, and is known to depress feed intake if used at levels exceeding 3-5%. Many plant-based ingredients contain feeding deterrents, so when vegetable proteins replace animal proteins in feeds, it is be important to consider the addition of a concentrated dose of attractants/stimulants to counter any deterrent effect.
Betaine is probably the only chemical that is widely used in the feed industry as an attractant. Its effectiveness has been shown in many fish species, but in shrimp, the evidence is still equivocal. A number of synthetic products based on a combination of amino acids, nucleotides, and other attractants are also entering the market. These products can be blended with a concentrated extract of natural attractant sources, such as various marine ingredients, to enhance their effectiveness.
"Effect of amino acids on the feeding behaviour in red sea bream" (1980) Yasumasa Goh & Tamotsu Tamura
Abstract
The effects of amino acids and betaine on the feeding behaviour of red sea bream (Chrysophyrys major) were studied by adding the chemicals to a casein-base purified diet. Among the 15 chemicals tested, ½ (alanine + betaine), ½ (glycine + betaine), L-alanine, L-valine, glycine, L-serine, L-arginine and L-glutamine were found to be effective in activating the feeding behaviour. The behavioural experiments were concluded to harmonize well with the electrical activities of the gustatory system rather than those of the olfactory system.
"Chemical nature of feeding stimulants for the juvenile Dover sole" (2006) A. M. Mackie, J. W. Adron & P. T. Grant
Abstract
Juvenile Dover sole, Solea solea, were weaned from a live food, Artemia salina nauplii, on to a casein-based particulate diet flavoured with flesh of the mussel, Mytilus edulis. These fish would not accept an unflavoured casein-based diet but readily ate the diet flavoured with either mussel flesh or a mixture of pure chemicals whose composition was based on an analysis of the low-molecular weight fraction of mussel flesh. The rate of growth and survival over a seventy-seven day period was essentially the same on either of the flavoured diets. The active constituent in the mixture of pure chemicals was identified as glycine betaine for fish of wet weight exceeding 50g while glycine betaine with certain L-amino-acids was required for fish of about 2.5 g wet weight. These results are discussed in relation to the known feeding behaviour and food preferences of the wild Dover sole.
"Attractive chemical substances for the weaning of Dover sole (Solea vulgaris): qualitative and quantitative approach" (2009) R. Métailler, M. Cadena-Roa & J. Person-Le Ruyet
Abstract
Two experiments were conducted to confirm and define quantitatively and qualitatively the efficiency of a mixture of attractive chemical substances (betaine, glycine, L-alanine, L-arginine, L-glutamic acid, inosine) for the weaning of 35-day-old, 120 mg weight soles. During the weaning period, a relatively high quantity (6.9% of the diet) is needed. Addition at lower levels (2.9%, 1.5%) resulted in slower growth (specific growth rate from 4.9% to 4.1%), lower survival (from 78% to 50%) and poorer feed conversion (from 2.2 to 5.5). The chemical mixture can be simplified by using only betaine, glycine and inosine, without any loss in attractive efficiency as compared to the original mixture.
"Operation Sea Angler: The Second Wave" (2013) Mike Ladle & Steve Pitts at pages 161 to 163
The Science of Lures and Baits
Are 'superbaits' a possibility
… both freshwater and marine fish use the 'key substance' approach to food location and identification … the active portion seemed to include seven amino acids. The amino acids serine and glycine produced grade 4 responses ("persistent searching") even at very low concentrations … whiting failed to respond to any mixture of amino acids if glycine and alanine were not present. Several other amino acids (arginine, taurine, aspartine and cysteine) gave only the very lowest level (grade 1 "no interest") responses.
The feeding activities of the fish were classified according to the amount of interest which they showed in the extracts:
- no interest or response
- aware of presence
- feeble searching
- persistent searching
- searching, backing up and biting at the food pipe
- directed searching, backing and biting at the pipe
At extremely low concentrations of bait extract the fish were unable to find the source of the attractant, even though their behaviour showed that they knew it was there. Mixtures of amino acids generally produced stronger responses than individual compounds, showing that no single substance was the perfect attractant. Although for cod and whiting glycine seemed to be the basis of attraction, it was still less effective than natural lugworm, so other substances are certainly involved … it seems that there is nothing to beat a bit of fresh natural bait although … the latest soft plastic lures … are often impregnated with artificial scents or come packed in 'juices' which some claim boost their catch rates.
… the dead remains of certain crustaceans may repel live animals of the same species … the most effective artificial bait would be one which involves not only attraction of the species that you want to catch, but also something that repels the ones you don't want … if live crabs can be repelled by the smell of dead crabs … a portion of dead shore crab attached to the hook could protect your bait from the depredations of living shore crabs …