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Intrinsic & Extrinsic parameters Intrinsic & Extrinsic parameters

controlling Fish Spoilagecontrolling Fish Spoilage

Dr. Dr. SubhenduSubhendu DattaDatta

Sr. Scientist Sr. Scientist

CIFE, Kolkata Centre, IndiaCIFE, Kolkata Centre, India

Extrinsic parametersExtrinsic parameters

Temperature of storageTemperature of storage

Relative humidityRelative humidity

Oxygen concentrationOxygen concentration

SalinitySalinity

Exhaustion of fish before catchExhaustion of fish before catch

Load of external microorganisms in the fish Load of external microorganisms in the fish

bodybody

By controlling these parameters it is possible to By controlling these parameters it is possible to control spoilage.control spoilage.

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Storage TemperatureStorage Temperature

Higher the temperature quicker the dissolution of rigor Higher the temperature quicker the dissolution of rigor and onset of autolysis and bacterial decomposition.and onset of autolysis and bacterial decomposition.

Each bacterial species has a range of temperature in Each bacterial species has a range of temperature in which it has optimum growth.which it has optimum growth.

Also there is a minimum temperature below which the Also there is a minimum temperature below which the growth does not take place and a maximum temperature growth does not take place and a maximum temperature above which bacteria cannot grow.above which bacteria cannot grow.

Cold loving bacteria Cold loving bacteria –– PsychrophilicPsychrophilic (0(0--202000C). Opt 15C). Opt 1500C eC e.g. Psuedomonas

MesophilicMesophilic bacteria bacteria –– 2020--454500C, Opt. C, Opt. 30 - 370C, e.g. Salmonella typhi.

ThermophilicThermophilic bacteria bacteria –– 4545--707000C, Opt 55C, Opt 5500C, C, e.g. Clostridium botulinum.

TempTemp……

Therefore, most of the spoilage bacteria grow faster with Therefore, most of the spoilage bacteria grow faster with the rise in temperature, thereby produce unpleasant endthe rise in temperature, thereby produce unpleasant end--products.products.

Therefore, the practical way to preserve fish in good Therefore, the practical way to preserve fish in good condition is to store the fish at low temperature. condition is to store the fish at low temperature.

After landing, fish should be immediately cooled down to After landing, fish should be immediately cooled down to the temperature of melting ice to retard quality loss.the temperature of melting ice to retard quality loss.

Chilling, however, only slows down the microbial activity, Chilling, however, only slows down the microbial activity, since since psychrophilicpsychrophilic bacteria are able to survive in chilled bacteria are able to survive in chilled fish.fish.

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TempTemp……..

"Gaping" depends on temperature; the higher "Gaping" depends on temperature; the higher the temperature of fish at the beginning of the the temperature of fish at the beginning of the rigor mortis process the greater the gaping of rigor mortis process the greater the gaping of the muscle.the muscle.

Gaping is muscle separation in fish fillets (during Gaping is muscle separation in fish fillets (during storage) which is considered a quality defect.storage) which is considered a quality defect.

Therefore, during rigor mortis fish temperature Therefore, during rigor mortis fish temperature should be as low as possible. should be as low as possible.

TempTemp……

Fish body temperature is a decisive factor in the Fish body temperature is a decisive factor in the onset and duration of the onset and duration of the rigor mortisrigor mortis process. process.

The higher the temperature the sooner it begins and The higher the temperature the sooner it begins and the faster it ceases. the faster it ceases.

For example, for roach and perch kept at 0For example, for roach and perch kept at 0°°C, C, rigor rigor mortis mortis begins 24 hours after death and lasts for 72begins 24 hours after death and lasts for 72--80 80 hours. hours.

When the same species is kept at 35When the same species is kept at 35°°C, it begins 20C, it begins 20--30 30 minutes after death and stops after about 3 hours. minutes after death and stops after about 3 hours.

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Temp..Temp..

This is evidenced by enzymatic reactions whose This is evidenced by enzymatic reactions whose speed increases with increased temperature. speed increases with increased temperature.

At high temperatures it results in greater changes in At high temperatures it results in greater changes in proteins, the latter causing higher loss of tissue proteins, the latter causing higher loss of tissue juices during processing. juices during processing.

Usually, the later Usually, the later rigor mortisrigor mortis begins and the longer begins and the longer it lasts, the longer are the storage life of the fish and it lasts, the longer are the storage life of the fish and its use for consumption.its use for consumption.

TempTemp……

Chilling and freezing is an effective way of Chilling and freezing is an effective way of reducing spoilage in fish, if it is done quickly, reducing spoilage in fish, if it is done quickly, handled carefully and hygienically. handled carefully and hygienically.

Higher the temperature of storage, shorter the Higher the temperature of storage, shorter the shelf life of fish. shelf life of fish.

As a general rule, for every hour that the fish are As a general rule, for every hour that the fish are kept at ambient temperature the equivalent of kept at ambient temperature the equivalent of one day's storage life is lost and for every 5one day's storage life is lost and for every 50C C and 0and 00C that they are stored, the storage life in C that they are stored, the storage life in ice is reduced by half. ice is reduced by half.

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TempTemp……

Freezing is by far the best method of heat Freezing is by far the best method of heat removal of fish. removal of fish.

The faster the freezing process, the lesser the The faster the freezing process, the lesser the spoilage. Therefore, quick freezing is adopted spoilage. Therefore, quick freezing is adopted commercially. commercially.

The recommended level at which the The recommended level at which the temperature of the fish has to be brought down temperature of the fish has to be brought down is is --303000C and the interior part of the fish has to be C and the interior part of the fish has to be --202000C. C.

R.H.R.H.

Higher the R.H. higher the chances of spoilage Higher the R.H. higher the chances of spoilage by bacteria.by bacteria.

Small fishes can be salted and dried within 2 Small fishes can be salted and dried within 2 days, but during inclement weather when the days, but during inclement weather when the R.H. is high the period could extend to 5R.H. is high the period could extend to 5--7 days. 7 days.

This results in poor quality of fish due to This results in poor quality of fish due to harbouring of spoilage bacteria and insect harbouring of spoilage bacteria and insect larvae. larvae.

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Fish Catching Technique or Fish Catching Technique or

Exhaustion of fish before catchExhaustion of fish before catch

The concentration of lactic acid formed due breakdown of glucoseThe concentration of lactic acid formed due breakdown of glucose is found to is found to be dependent on the glycogen reserves of the muscle prior to deabe dependent on the glycogen reserves of the muscle prior to death. th.

The glycogen reserve of the muscle is directly related to the stThe glycogen reserve of the muscle is directly related to the struggle the fish ruggle the fish has undergone prior to capture and death. has undergone prior to capture and death.

The greater the struggle the fish has experienced the lesser areThe greater the struggle the fish has experienced the lesser are its glycogen its glycogen reserves and the onset of reserves and the onset of rigor mortisrigor mortis becomes rapid. becomes rapid.

Therefore,Therefore, Rigor mortisRigor mortis proceeds very quickly in very active fish but rather proceeds very quickly in very active fish but rather slowly in inert fish. slowly in inert fish.

One consequence of the accumulation of lactic acid in the muscleOne consequence of the accumulation of lactic acid in the muscle is the is the lowering of pH from near neutrality (pH 7.0) to the lactic acid lowering of pH from near neutrality (pH 7.0) to the lactic acid range (pH 6.0). range (pH 6.0).

The decline of pH affects the quality of the fish tissues, in thThe decline of pH affects the quality of the fish tissues, in that flesh become at flesh become firmer and tendency to drip enhances. But after the death of fisfirmer and tendency to drip enhances. But after the death of fish acidic pH is h acidic pH is better than alkaline pH to prevent microbial decomposition.better than alkaline pH to prevent microbial decomposition.

Fish Catching Technique/handlingFish Catching Technique/handling……..

In those fish which are in good condition (wellIn those fish which are in good condition (well--nourished) nourished) rigor mortisrigor mortis is more intensive. Fish put to death just after is more intensive. Fish put to death just after removal from the water reach a state of removal from the water reach a state of rigor mortisrigor mortis later later than those fish which died after a long agony. than those fish which died after a long agony.

In the case of carp put to death just after capture In the case of carp put to death just after capture rigor rigor mortismortis begins after 48 hours, but if the carp died after a begins after 48 hours, but if the carp died after a long agony it sets in after 24 hours (at 0long agony it sets in after 24 hours (at 0°°C).C).

Unnecessary and rough handling of the fish can shorten Unnecessary and rough handling of the fish can shorten the time of occurrence and duration of the time of occurrence and duration of rigor mortisrigor mortis. Such . Such treatment causes stress in live fish.treatment causes stress in live fish.

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handlinghandling

Efficient handling immediately after shrimp Efficient handling immediately after shrimp

harvest is very effective in preventing harvest is very effective in preventing

black discolouration on raw shrimp. black discolouration on raw shrimp.

TyrosinaseTyrosinase and and polyphenolpolyphenol oxidaseoxidase, that , that

catalysecatalyse black spot formation, are present black spot formation, are present

in large quantities in the digestive system in large quantities in the digestive system

of the shrimp. of the shrimp.

Oxygen concentrationOxygen concentration

Oxidative rancidity - Oxidation of fish oils yielding the rancid odours and tastes which are the major problem encountered in fish storage.

Lowering of oxygen level reduce the magnitude of rancidity

Aerobic - Bacteria which grow only in the presence of air. e.g. Micrococcus.

Anaerobic - Bacteria which grow only in the absence of oxygen. e.g. Clostridium sp.

Facultative – Bacteria grow in presence or absence of oxygen. Ex. Salmonella, Vibrio

Microaerophilic – bacteria grow better in the presence of very little free oxygen. Ex. – Lactobacillus, Streptococcus

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SalinitySalinity

Halophilic - Bacteria which grow best in the presence of salt.e.g. Serratea salinaria.

Halophobic - Bacteria which cannot tolerate salt concentrations higher than 6%.e.g. Achromobacter, Pseudomonas.

The population and nature of bacterial flora The population and nature of bacterial flora depend on the waters from where the fish are depend on the waters from where the fish are caught i.e. whether from sea water, brackish caught i.e. whether from sea water, brackish water or fresh water.water or fresh water.

Depending on the salinity and pollution range of waters, Depending on the salinity and pollution range of waters, the bacterial flora of fishes vary from water to water.the bacterial flora of fishes vary from water to water.

Majority of bacterial flora of marine fishes are gram Majority of bacterial flora of marine fishes are gram negetaivenegetaive, non, non--spore forming rods or spore forming rods or coccicocci..

Bacterial flora fresh water fishes are predominantly gram Bacterial flora fresh water fishes are predominantly gram positive in nature.positive in nature.

There are large number of bacterial types in marine There are large number of bacterial types in marine water than Fresh water water than Fresh water

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Load of external microorganisms in Load of external microorganisms in

the fish bodythe fish body

Fish often get contaminated through woodenFish often get contaminated through wooden--boxes, ice, dressingboxes, ice, dressing--tables tables etc., which usually carry heavy bacterial load. etc., which usually carry heavy bacterial load.

Proper treatment of surfaces, equipments etc., with disinfectantProper treatment of surfaces, equipments etc., with disinfectants and s and detergents, and use of potable water for washing and icedetergents, and use of potable water for washing and ice--making are making are necessary to reduce bacterial contamination. necessary to reduce bacterial contamination.

The initial bacterial load and the nature of contaminants play aThe initial bacterial load and the nature of contaminants play a vital role in vital role in the deterioration of fish in the later stages. the deterioration of fish in the later stages.

Slime contains large amounts of nitrogenous compounds and these Slime contains large amounts of nitrogenous compounds and these provide provide good nourishment for microgood nourishment for micro--organisms originating from the environment. organisms originating from the environment.

Fish which secrets more slime, contains more microorganisms fromFish which secrets more slime, contains more microorganisms from the the environmentenvironment

After bringing to the factory, the fish are washed with flowing After bringing to the factory, the fish are washed with flowing water to water to remove the heavily contaminated slime.remove the heavily contaminated slime.

Intrinsic parametersIntrinsic parameters

�� Intrinsic quality means the sum of attributes that Intrinsic quality means the sum of attributes that are inherent in the harvested raw material are inherent in the harvested raw material ((ConnelConnel, 1980)., 1980).

�� It is somehow more difficult to control the It is somehow more difficult to control the inherent properties of fish tissues that influence inherent properties of fish tissues that influence enzymatic and microbial spoilage of fish.enzymatic and microbial spoilage of fish.

�� The The intrinsicintrinsic moisture content, pH, physical and moisture content, pH, physical and chemical nature of fishchemical nature of fish (fresh or marine), in part, (fresh or marine), in part, control the number and types of microorganisms control the number and types of microorganisms involved in the spoilage process.involved in the spoilage process.

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In the case of fish, caught in the wild, the In the case of fish, caught in the wild, the complete control or manipulation of intrinsic complete control or manipulation of intrinsic quality is impossible.quality is impossible.

But two types of control are possible. The first is But two types of control are possible. The first is conscious selection of grounds, seasons or conscious selection of grounds, seasons or fishing methods.fishing methods.

The second is selection or sorting from mixed The second is selection or sorting from mixed catches, the fish of desired quality.catches, the fish of desired quality.

In the case of cultivated fish active control of In the case of cultivated fish active control of intrinsic quality is feasible.intrinsic quality is feasible.

Factors affect the intrinsic qualityFactors affect the intrinsic quality

The factors that affect intrinsic quality areThe factors that affect intrinsic quality are

Species Species

SizeSize

SexSex

Condition and compositionCondition and composition

Parasites and other organismsParasites and other organisms

Naturally toxic fishNaturally toxic fish

Contamination with pollutantsContamination with pollutants

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SpeciesSpecies

Certain fishes are generally costly as they are Certain fishes are generally costly as they are rated as rated as ““good fishgood fish””..

Ex. Ex. –– RohuRohu & & CatlaCatla fetches more price than fetches more price than

MrigalMrigal, Silver carp, common carp, Tilapia, Silver carp, common carp, Tilapia

Marine fishes contains more lipid than Marine fishes contains more lipid than freshwater fishes. freshwater fishes.

Therefore, chances of rancidity is higher in Therefore, chances of rancidity is higher in marine fishes than freshwater fishes. marine fishes than freshwater fishes.

SpeciesSpecies……

The time The time rigor mortisrigor mortis begins and its duration begins and its duration depend on the depend on the fish speciesfish species..

For carp at 0For carp at 0°°C, it starts after 48 hours, C, it starts after 48 hours,

For roach and perch at 0For roach and perch at 0°°C after 24 hoursC after 24 hours

It was also found that fast swimmers, for It was also found that fast swimmers, for example trout, undergo example trout, undergo rigor mortis rigor mortis faster but for faster but for a shorter duration than slow swimmers like carpa shorter duration than slow swimmers like carp..

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SpeciesSpecies……

Fish which secrete great quantities of slime have poorly Fish which secrete great quantities of slime have poorly developed scales; very often the quantity of slime developed scales; very often the quantity of slime reaches 2reaches 2--3% of the fish mass and that in turn creates 3% of the fish mass and that in turn creates problems during processing. problems during processing.

Slime contains large amounts of nitrogenous compounds Slime contains large amounts of nitrogenous compounds and these provide good nourishment for microand these provide good nourishment for micro--organisms originating from the environment. organisms originating from the environment.

Therefore, the slime spoils quickly: first giving an Therefore, the slime spoils quickly: first giving an unpleasant smell to the fish, and second opening the unpleasant smell to the fish, and second opening the way for further and deeper bacterial penetration into the way for further and deeper bacterial penetration into the fish.fish.

SpeciesSpecies……

During storageDuring storage

NonNon--fatty (or white fish) keep longer than fatty (or white fish) keep longer than

fatty fish.fatty fish.

Freshwater fish keep longer than marine Freshwater fish keep longer than marine

fishfish

Fish from warm waters keep longer than Fish from warm waters keep longer than

fish from temperate waters. fish from temperate waters.

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SizeSize

In general, large fish of a given species fetch the In general, large fish of a given species fetch the

higher price, for example, shrimp, Scampi, crab, higher price, for example, shrimp, Scampi, crab,

lobster.lobster.

The % yield of edible material is higher and The % yield of edible material is higher and

handling cost per unit weight is lower in large handling cost per unit weight is lower in large

fish of a given species.fish of a given species.

It is a fact that large fish keep better than small It is a fact that large fish keep better than small

fish. This can be attributed to:fish. This can be attributed to:

The smaller surface area to volume ratio for The smaller surface area to volume ratio for large fish so that in the same time period, less of large fish so that in the same time period, less of the interior of large fish is affected by spoilage the interior of large fish is affected by spoilage micromicro--organisms penetrated from the surface to organisms penetrated from the surface to the interior.the interior.

Small fish of a given species tend to have a Small fish of a given species tend to have a higher posthigher post--rigor pH than large fish of the same rigor pH than large fish of the same species, thus giving rise to the greater bacterial species, thus giving rise to the greater bacterial action.action.

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SexSex

In certain species, the females are of very In certain species, the females are of very

poor quality soon after spawning.poor quality soon after spawning.

The canned product made from female The canned product made from female

Capelin (Capelin (MallotersMalloters villosusvillosus) is very ) is very

different from that made from male different from that made from male

capelin.capelin.

Condition & CompositionCondition & Composition

During certain period fish appear thinner, During certain period fish appear thinner, flabbier and less lively, the flesh being more flabbier and less lively, the flesh being more watery and softer and containing less protein watery and softer and containing less protein and fat.and fat.

The fat content of many species vary The fat content of many species vary considerably throughout the year.considerably throughout the year.

After spawning the fat content of many fishes After spawning the fat content of many fishes vary considerably.vary considerably.

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Parasites, bacteriaParasites, bacteria

Sea fishes can harbour protozoa and intestinal worms Sea fishes can harbour protozoa and intestinal worms which are dangerouswhich are dangerous

Intrinsic bacteria and viruses in the slime, gill, guts and Intrinsic bacteria and viruses in the slime, gill, guts and intestine of the fishintestine of the fish

Bacterial population in fish body:Bacterial population in fish body:

Skin surface < gill tissue < IntestineSkin surface < gill tissue < Intestine

Summer months > winter monthsSummer months > winter months

Naturally Toxic fishNaturally Toxic fish

Due to Ciguatera toxicity in the flesh of fish Due to Ciguatera toxicity in the flesh of fish & shellfish inhabiting shallow waters in or & shellfish inhabiting shallow waters in or near subtropical coral reefs.near subtropical coral reefs.

Paralytic shellfish poisoning in Paralytic shellfish poisoning in molluscsmolluscs & & calms during the period of in the high calms during the period of in the high concentration of concentration of dinoflagellatesdinoflagellates in sea.in sea.

These poisoning spoil the fishes in source.These poisoning spoil the fishes in source.

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Contamination with pollutantsContamination with pollutants

Metals (Hg), chlorinated hydrocarbons, Metals (Hg), chlorinated hydrocarbons,

Mineral oils, radioactive isotopes, Mineral oils, radioactive isotopes,

antibiotic residues etc. contaminate the antibiotic residues etc. contaminate the

fishes in source and are therefore, fishes in source and are therefore,

intrinsic in nature. intrinsic in nature.

Moisture content of fish bodyMoisture content of fish body

Higher the moisture content higher will be the spoilage.Higher the moisture content higher will be the spoilage.

Bacteria need water for growth and multiplication. Below a Bacteria need water for growth and multiplication. Below a minimum level of water activity (aminimum level of water activity (aww), microorganisms cannot ), microorganisms cannot grow.grow.

When we dry fish, water is removed from the fish muscle to When we dry fish, water is removed from the fish muscle to a level below 0.9, so that bacterial action is completely a level below 0.9, so that bacterial action is completely prevented.prevented.

By drying & salting, the moisture content of fish is brought By drying & salting, the moisture content of fish is brought around 38% when bacterial growth is inhibited. around 38% when bacterial growth is inhibited.

When the moisture content of fish is reduced to 25%, When the moisture content of fish is reduced to 25%, autolyticautolytic activity is greatly reduced, while mould growth is activity is greatly reduced, while mould growth is prevented if moisture level is reduced to 15%.prevented if moisture level is reduced to 15%.

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pHpH

Lower the pH lower the decomposition by Lower the pH lower the decomposition by bacteria.bacteria.

Acidophiles - Bacteria which can survive at a pH of 4.5 and below. e. g. Lactic acid bacteria.

Example: Fish silage is preserved against the microbial spoilage mainly by the lowered pH, obtained by the added or in-situ produced acid.

Specifically, the unionized acid molecules are able to cross the cytoplasmic membrane barrier of the microbial cell while protons (H+) and acid anions cannot.

pHpH……

But once inside the bacterial cell, the acid molecule can ionize, and since the membrane traps the ions, the pH gradually comes down killing the cell.

Thus, it is the unionized acid molecules that are responsible for the preservative action rather than the total acid concentration.

At equal concentrations, organic acids are weekly ionized in solution compared to inorganic acids, thus contain greater amounts of unionized (free) acid molecules making them more effective preservatives.

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pHpH……..

Once the rigor mortis ceases, bacterial Once the rigor mortis ceases, bacterial spoilage becomes rapid. spoilage becomes rapid.

This is accompanied by the rise of muscle This is accompanied by the rise of muscle pH from acidic range to alkaline range pH from acidic range to alkaline range (sometimes upto pH 8) due to (sometimes upto pH 8) due to accumulation of volatile bases like accumulation of volatile bases like ammonia and ammonia and trimethyltrimethyl amine (TMA) amine (TMA) produced by spoilage of fish. produced by spoilage of fish.

pHpH……

Spoilage bacteria present is the fish tend to minimize the Spoilage bacteria present is the fish tend to minimize the rich free amino acid pool present as energy source and rich free amino acid pool present as energy source and produce ammonia thereby increase the pH (by produce ammonia thereby increase the pH (by deaminationdeamination reaction caused reaction caused denaturationdenaturation of protein).of protein).

Number of lactic acid bacteria (LAB) present in fish are Number of lactic acid bacteria (LAB) present in fish are too few to result in their dominance over much greater too few to result in their dominance over much greater number of spoilage number of spoilage microfloramicroflora..

Because of this reason, sugar and innoculum of lactic Because of this reason, sugar and innoculum of lactic acid bacteria is added in fish silage to provide a head acid bacteria is added in fish silage to provide a head start to lactic acid fermentation.start to lactic acid fermentation.

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Physical and chemical nature of Physical and chemical nature of

fish (fresh or marine)fish (fresh or marine)

Already discussed before under the Already discussed before under the

title title ““SpeciesSpecies””..

SummarySummary

So to reduce the spoilage of fish during storage;So to reduce the spoilage of fish during storage;

Reduce the temperature of storage (< Reduce the temperature of storage (< -- 202000C)C)

Reduce the moisture content of the fish (<20%)Reduce the moisture content of the fish (<20%)

Reduce the pH (< 7) of stored fishReduce the pH (< 7) of stored fish

Reduce the rough handling of fish during catching, packing, Reduce the rough handling of fish during catching, packing, storing etc.storing etc.

Reduce R.H., OReduce R.H., O22 during storageduring storage

Reduce storing of smaller sized fishReduce storing of smaller sized fish

Reduce the time lag between catching of fish and Reduce the time lag between catching of fish and preservationpreservation