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• Carbohydrates; Carbohydrates provide the bulk of energy for the fry and in excess amounts will be stored in the fry as fat. To be used as energy, carbohydrates are broken down by enzymes into soluble glucose which can be absorbed into the blood stream. Compared to other animals, fish (especially tropical species) have a relative ly low requirement for carbohydrates and a much higher protein requirement.
-
Protein; Proteins are made up on amino-acids which are broken down in the fry s digestive system by certain enzymes. Guppies have a relatively simple digestive system which consists of a simple stomach and a moderate-length intestine which suits their omnivorous diet (10). Protein is split into amino acids by hydrochloric acid and the enzyme pepsin present in the stomach. Protein undigested in this way is then broken down by enzymes such as trypsin in the intestine.These are then used to allow the fry to develop muscle mass and enzymes etc. In situations where carbohydrates are unavailable, the fry are able to convert some of the protein they consume into energy; however, compared to carbohydrates, very little energy is extracted from proteins.
-
Ash Content; Processed foods have a varying ash content depending on the quality of the manufacturing process. Traditional food products are produced at a higher temperature and thus have a higher ash content. Newer food processing technologies such as Tetra s “Primex” process
the food at lower temperatures and preserving the nutritional content resulting in a “lower ash content”. These foods however cost more than trad itional types.
• Vitamins and Minerals; These are added to processed foods and occur naturally in other foods such as daphnia and algae. Lack of certain vitamins and minerals would result in stunted growth, blindness or emaciation.
Analysis of Variables
Independent Variables;
Independent variables are factors in the experiment which are changed to produce an effect. In this experiment, the independent variables are the types of fish food offered.
• TetraPrima Granules; The most expensive of the processed fish foods teste d and this is reflected by the highest nutritional value. It als o has a very low ash content of 10%. Ash is inert material which would not be digested by the fish a nd offers no nutritional value whatsoever. Protein content of this feed is very high (47.5%) considering it is designed mainly for adult fish.
• Aquarian Tropical Flake Food; A budget processed fish food which offers reasonable nutritional value but a much higher ash content (14%). This would result in a much higher production of waste material by the fry. This food also has the lowest protein content of all the processed foods used (36.5%)
-
Freeze-dried Brine Shrimp; An entirely natural product and commonly used as a “first food” for developing fry. It is renowned for its high protein and fibre content as well as virtually the same nutritional content as fresh Brine Shrimp. Freeze drying keeps the products original nutritional content and allows the product to be stored for much longer than live or fresh foods. Because Freeze Dried Brine Shrimp is a relatively unprocessed food product, nutritional information varies greatly. Generally, Freeze Dried Brine Shrimp contains 48-52% protein.
-
Natural Food Products; These include foods which Guppy Fry will consume in the wild. These include infusoria (small aquatic organisms), insect larvae, algae and daphnia. Infusoria were gathered by soaking lettuce leaves in old tank water which encourages the growth of organisms which cloud the water whereas insect larvae and algae are collected from an established fish tank. Mosquito Larvae provide the bulk of the diet of Guppy fry in the wild, and the experiment had to be carried out when they are in season. It has been suggested that natural foods contain the highest vitamin and mineral content; however, they also contains a high percentage of water and indigestible fibre, which offers no nutritiona l value.
Dependent Variables
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Dependent variables are affected by the independent variable, and are measured to see whether the independent variable has had an effect. Dry mass of the fry would be the most accurate way of
measuring the growth of fry, however this would be both unethical and impractical, as the fry would need to be measured on a regular basis. Wet mass would be used instead as it allows growth to
be measured while the animal is still alive and avoids ethical issues.
Control/Extraneous Variables
-
Temperature of water: Guppies, like most other bony fish cannot regulate t heir body temperature independent from the environment, which means that all their heat is gathered from their surroundings. Because the surrounding temperature can determine the metabolism of the fry, it is very important to ensure that all the fry in this experiment are exposed to the same temperature conditions. The water temperature is kept at a constant 21℃ to ensure validity and reliability.
-
Nitrogen content of water: Studies have shown that fishes kept in overcrowded o r smaller
tanks will exhibit stunted growth compared to those kept in larger volumes of water. This is evident in “goldfish bowls” where animals kept in these will only reach less than half their potential size. There have been many theories for why this may be; one suggests that the physical stress of not having enough space prevents them from growing to their full potential size. Another suggests the presence of a growth-inhibiting hormone emitted by all fishes that builds up in smaller environments and prevents all members of the community from outgrowing their environment. Respirating aquatic life emits ammonia, which even in low concentrations is very toxic. This causes stress and changes in physiology that prevents the fry from reaching their full size. It is important to ensure that ammonia levels in the experiment tank are kept under
control. Ordinarily, ammonia would be kept under control by “cycling” the tank, allowing beneficial bacteria to build up which converts the ammonia into nitrites and then into harmless nitrates. To keep the experiment valid, the fry must be kept in a sterile tank to ensure that they have no
access to any other food source other than those given and this means cycling the tank is not possible. In this experiment, a partial water change would be carried out every day to prevent the build-up of ammonia and the use of the mineral zeolite to adsorb excess ammonia.
• Oxygen content of water: Because the fry are being kept in the same tank, it is assumed that the dissolved oxygen concentrations should remain the same. While this would not affect the validity of the experiment, reliability may be compromised as oxygen levels would fluctuate, and a repeat experiment may not have the same dissolved oxygen levels, causing a different final result. Oxygen content of the water may affect the fry s metabolism and their growth and this would need to be taken into consideration.
• Fry genetic makeup: The fry used in this experiment have been line bred from 5 guppies for over 4 generations, so it is likely that they are genetically similar. Unfortunately, they may still show differences in terms of growth and behaviour, all of which can affect the validity of the experiment.
• Nutritional Value of Natural Foods: “Natural Foods” in this experiment refers to the fo ods that guppies will encounter in their natural habitat, including infusoria, daphnia and mosquito larvae. Unlike processed foods though, natural foods have no definite nutritional value, and their water content varies greatly, making it very hard to measure precisely how much food the fry have consumed. Fry also encounter different conditions in the wild, which makes it hard to determine how much food they should eat. The fry fed natural foods in this experiment have had quantities determined by experience.
Trial Investigation
Procedure;
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1. It is important to sterilise the tank and equipment as much as possible as to avoid giving the fry any additional food source. This was done by soaking them in boiling water. No bleach or disinfectants were used as the traces left behind, even after rinsing is toxic to aquatic life. It is impossible to keep tanks completely sterile during the course of the experiment as micro-organisms can occur from invisible spores or from the fry themselves.
This experiment would be carried out with 6 fry per fish food type, which should give enough
2.
results for a valid experiment. Because the survival rate of fry is much lower than that of adult fish, having 6 per tank would ensure that there woul d always be 5 in a tank should one not survive.
All fry are individually weighed by mass by putting them into a known mass of water and
- calculating the difference.
One tank is used for all experiments to ensure that factors such as water temperature,
- hardness, pH and dissolved oxygen levels are the same for all fishes. Mesh dividers are used to separate the fry and food.
The mass of food the fry receive is very small, and is difficult to measure individual feedings separately. This is why the food was weighed to provide enough over a 5 week period (or
- 0.15g). Natural food products such as infusoria and mosquito larvae cannot be weighed easily and their nutritional content varies greatly, so the fry are given a continuous supply as they would in the wild. The fry are fed daily with their pre-measured food reserves.
A partial water change of 40% is conducted daily to ensure ammonia remains at a safe level and pH buffers such as calcium carbonate are replenished. The zeolite used to adsorb
- ammonia works by ion exchange, and it is possible that sodium ions could be leached into the water. A partial water change should remove any excess ion build up as well.
The fry will be measured every week to track their progress
Once they have been in controlled conditions for 5 weeks, they will be returned to their original
species tank where they originated.
7.
8.
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Original Trial Method with mesh dividers
Equipment/Specimens;
-
Sterile food-grade plastic tanks; Food grade plastic is used as it does not leech any substances into the tank water, and they don t carry the same physical dangers as glass. They are also lightweight making daily water changes much less risky.
-
Thermometers; Used to measure the water temperature to ensure that all the tanks are at the same temperature. The thermometers used measure the temperature to the nearest 0.1℃ which is adequate for ensuring the tanks are al the same temperature.
-
Camera and ruler guide; Used to measure the growth of fry. The measurements taken can be very accurate as distance can be judged with the subject still in software.
-
Water conditioners and resins; Used to remove harmful chlorine from the domestic water
supply and to ensure that the constant output of ammonia from the fry is kept under control.
• Air Pump; used to circulate the water in the tank using the “ air-lift” principle, bringing oxygen rich surface water to the bottom of the tank and vice-versa. A 4 way splitter and diffuser was used to prevent excessive water movement in the fry tank which could cause stress.
• Infusoria Tank; This tank is kept near a hot window and contains aquatic fertilisers and organic matter which feeds and encourages the growth of micro-organisms one group of fry will feed on.
• Guppy Fry; The fry used in this experiment have been separated from the main tank and kept under normal conditions with a varied diet for 2 weeks. This is to ensure that we can select healthy fry for the experiment. Deformed fry such as those with bent spines or common “belly-sliders” who have a dysfunctional swim-bladder ar e culled and not used in the experiment.
Problems with Original Procedure
The trail procedure quickly showed major flaws in th e design of the experiment concerning accuracy of measurements and physical limitations of the way the fry are kept.
-
Calculating Fry Growth: Originally, the growth of the fry would be calculated by wet mass, which theoretically would have been the best way to measure mass. In practice however, even with extremely sensitive scales (0.001g), it was difficult to determine the mass of the fry. It was found that a single fry would have very different masses when weighed within minutes of each other. An explanation for this could be the film o f water transported with the fry, as the surface tension makes it difficult to transport the fry wi thout water. The scales also varied greatly with the fry on them, as the movement of the fry caused the reading to change, preventing an accurate reading. Restraining fish of this size is both str essful and potentially harmful for the organism.
-
Single Tank and Contamination: Having all fry in a single tank with mesh dividers was done to ensure all the fry are kept under the same conditions, temperature and pH for example. In practice, this was very impractical as the mesh dividers were only able to separate the processed foods while natural or live foods such as mosquito larvae, daphnia and baby brine shrimp would swim freely through the mesh to be eaten by other fry.
Changes to Experiment
Calculating Fry Growth
Length would be the next best way of measuring growth. Even this had problems, as the fry are constantly moving making measurement near impossible. Instead, a photo of the fry would be taken from directly above as to avoid distortion due to perspective, then analysed in image manipulation software to provide an accurate measurement of the length of fry. It is also essential that the water level is as low as possible to allow for accurate measuring of length. Several images
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are taken in succession to provide the best image of each fry (fry are constantly swimming and it is important to capture them at the moment where their bodies are straight). Measuring fry with this method is not as valid as mass. Fins are also not taken into account.
Length of Fry measured in Adobe Photoshop. The sample container is placed on a ruler for reference
Single Tank and Contamination
Instead of keeping all fry in a single tank, each fi sh food group would have its own tank. This would ensure that there is no contamination in fish food, however it makes it more likely for conditions in one tank to be different from another, especially in the natural/live food tank where organisms will be respiring or photosynthesising. This was alleviated by testing the water on a daily basis and conducting a partial water change every day to quickly replenish buffers and minerals in the water, as well as removing any excess ammonia. All the tanks will also be kept adjacent to one another to keep factors such as lighting and heat the same. Oxygen concentration is difficult to control, especially in the natural/live food tank, therefore must be considered an extraneous variable.
Final Method
1. In the final method, fry fed on different types of fi sh food will be kept in different tanks as to avoid contamination. These tanks would be of the same size and shape to keep variables such as space and surface area the same.
- This experiment would be carried out with 6 fry per fish food type, which should give enough results for a valid experiment. Because the survival rate of fry is much lower than that of adult fish, having 6 per tank would ensure that there w ould still be a large number of fry should one not survive.
- Instead of mass, the start length of fry would be measured by length. To do this, all fry are removed into a separate flat-bottom containing an d placed over a ruler for reference. An image
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of the fry would be taken directly above and then analysed in image editing software to identify length
-
All fry tanks would be kept in the same room under the same conditions. Room temperature is kept at a constant 21℃, although if there are any variations in temperature would affect all fry, which would prevent validity issues at the expense of reliability. Factors such as ammonia concentration, pH and nitrate concentration are also tested regularly to ensure that the tanks provide similar conditions.
All the fry fed on processed food will receive 0.025g of food each (0.15g of total food per
- variable) which would last 5 weeks. Fry fed on live food will have a constant supply of algae, daphnia and various insect larvae.
A partial water change of 40% is carried out every day to ensure ammonia remains at a safe
- concentration and pH buffers are replenished. Waste ions from the zeolite s ion exchange is also removed in this way.
Fry will be measured every week to track progress
After 5 weeks, the fry will be returned to their original species tank.
7.
8.
Bar Chart showing Average Difference in Length of Fry
0.60
Difference
in Length
(cm)
0.45
0.30
0.15
0
TetraPrima Aquarian Flakes Natural Foods FD Brine Shrimp
This graph initially shows that feeding Freeze Dried Brine Shrimp increases growth rate considerably compared to other fish food types while feeding Aquarian Flakes shows the lowest growth rate over the 5 week period. TetraPrima granules provide the second fastest growth rate
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whereas natural foods gives the second slowest. Upon closer inspection however, and it is clear that from the SD bar data that there is considerable overlap in some of the results. For example,
the SD bar for Aquarian Flakes is almost completely overlapped by that from Natural Foods, which makes it very difficult to support the conclusion th at Aquarian Flakes provide the slowest growth rate as some of the guppies fed on Natural Foods may have grown as slowly. The only reliable conclusion we can draw from this graph is that feeding fry Freeze Dried Brine Shrimp results in a significantly higher growth rate than Aquarian Flake s, as the SD bars do not overlap.
Statistical Analysis (Mann Whitney U Test)
The first step to determining statistical significanc e by using the Mann Whitney U Test is to arrange the data from the two groups to be compared in order size. A “rank” is then placed after each value (if two values are of the same rank, then the ranks would be applied, then added together and divided by the number of values which fall into the same rank, hence some of the ranks in the table being 11.5 or 2.5)
In this example, we investigate if there is any statistical significance between the growth difference of fry fed on TetraPrima and Aquarian Flakes.
∑R1 is calculated by adding the values of the ranks together N1 is the number of values (fry) in each category
U1 is measured by adding the n1 value of each category together. This value is then added to the value of (0.5*n2*(n2+1))-∑R1.
The critical value of U is found by looking at the Critical Values chart. The particular chart used for this experiment has a level of significance of 5% (P =0.05) and with a both sample sizes being 6, the critical value is 5. We can find out if the null hypothesis is to be rejected or not by comparing the “Smalest U-Value” with the Critical Value of U. If the “Smallest U-Value” is smaller than the “Critical Value of U”, the Null hypothesis is rejec ted with a 0.5% confidence level. The opposite would be true if the Smallest U-Value was larger than the Critical Value of U.
This process is repeated for all the hypothesis to determine the statistical significance.
1.0
2.5
2.5
5.0
5.0
9.0
25.00
6.00
4.00
0.18
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Hypothesis (Green = Directed, Red = Null)
Fry fed on Freeze Dried Brine Shrimp would grow faster than those fed on TetraPrima, Fry fed on Freeze Dried Brine Shrimp would grow no faster than those fed on TetraPrima
Fry fed on Freeze Dried Brine Shrimp would grow faster than those fed on Aquarian Flakes, Fry fed on Freeze Dried Brine Shrimp would grow no faster than those fed on Aquarian Flakes
Fry fed on Freeze Dried Brine Shrimp would grow faster than those fed on Natural Foods,
Fry fed on Freeze Dried Brine Shrimp would grow no faster than those fed on Natural
Foods
Fry fed on TetraPrima would grow faster than those fed on Freeze Dried Brine Shrimp, Fry fed on TetraPrima would grow no faster than those fed on Freeze Dried Brine Shrimp
Fry fed on TetraPrima would grow faster than those fed on Aquarian Flakes, Fry fed on TetraPrima would grow no faster than those fed on Aquarian Flakes
Fry fed on TetraPrima would grow faster than those fed on Natural Foods, Fry fed on TetraPrima would grow no faster than those fed on Natural Foods
Fry fed on Aquarian Flakes would grow faster than those fed on Freeze Dried Brine Shrimp,
Fry fed on Aquarian Flakes would grow no faster than those fed on Freeze Dried Brine
Shrimp
Fry fed on Aquarian Flakes would grow faster than those fed on TetraPrima, Fry fed on Aquarian Flakes would grow no faster than those fed on TetraPrima
Fry fed on Aquarian Flakes would grow faster than those fed on Natural Foods, Fry fed on Aquarian Flakes would grow no faster than those fed on Natural Foods
Comments
No Significant Difference. Null Hypothesis
Accepted.
Significant Difference Present. Null
Hypothesis Rejected.
No Significant Difference. Null Hypothesis
Accepted.
No Significant Difference. Null Hypothesis
Accepted.
Significant Difference Present. Null
Hypothesis Rejected.
No Significant Difference. Null Hypothesis
Accepted.
Significant Difference Present. Directed
Hypothesis Rejected
Significant Difference Present. Directed
Hypothesis Rejected
No Significant Difference. Null Hypothesis
Accepted.
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Hypothesis (Green = Directed, Red = Null) Comments
Fry fed on Natural Foods would grow faster No Significant Difference. Null Hypothesis
than those fed on Freeze Dried Brine Shrimp, Accepted.
Fry fed on Natural Foods would grow no
faster than those fed on Freeze Dried Brine
Shrimp
Fry fed on Natural Foods would grow faster No Significant Difference. Null Hypothesis
than those fed on TetraPrima, Fry fed on Accepted.
Natural Foods would grow no faster than
those fed on TetraPrima
Fry fed on Natural Foods would grow faster No Significant Difference. Null Hypothesis
than those fed on Aquarian Flakes, Fry fed on Accepted.
Natural Foods would grow no faster than
those fed on Aquarian Flakes
The Mann Whitney U Test confirms the conclusions dra wn from the bar chart and it s SD bars. It suggests that there is no significant difference bet ween the different types of fish food apart from Freeze Dried Brine Shrimp and Aquarian Flakes.
Conclusions
From both the bar chart and the Mann Whitney U Test, we can conclude that there is a significant difference between the growth of fry fed on Freeze Dried Brine Shrimp and Aquarian Flakes, thus we can accept with confidence the hypothesis that fe eding fry Freeze Dried Brine Shrimp causes them to grow faster than if they were fed Aquarian Flakes. There is no significant difference between any of the other values however, which means that none of the other directed hypothesis can be accepted.This is understandable as the difference in % protein content of TetraPrima (47.5%) and Aquarian Flakes (36%%) is only 11% whereas the difference in protein content of Aquarian Flakes and Freeze Dried Brine Shrimp (up to 52%) is much greater at 15%. Protein is broken down by the fry s digestive system into amino acids by breaking peptide bonds which are then used by the body to produce new muscle mass and proteins etc. This leads to growth and as this experiment shows, providing more protein to guppy fry causes them to grow more rapidly.
Unfortunately, while the bar chart suggests that the growth rate of fry follows the pattern of FD Brine Shrimp > TetraPrima > Natural Foods > Aquarian Flakes, the SD bars and Mann Whitney U Test suggests that there is in fact no significant d ifference between the rest of the results. Therefore we should accept the null hypothesis for these results.
Discussion
The SD bars for Natural Fish Foods is unusually large compared to the other fish food types. With a Standard Deviation of 0.12, it is twice the Standard Deviations of the fry fed on TetraPrima. This could be due to the fact that natural foods vary greatly in terms of nutrition (the low SD of TetraPrima could be the effect of a consistent manufacturing process) and also the fact that natural/live foods can respire or photosynthesise, affecting the oxygen/carbon dioxide/mineral content of the water which could ultimately affect the growth of the fry.
We could even draw another conclusion from the SD values for the different fish food types, as it follows a very interesting pattern. TetraPrima and Aquarian Flakes both have a lower SD value than Freeze Dried Brine Shrimp (which is relatively unprocessed) and Natural Foods which could
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be due to their manufacturing process. We could also possibly conclude that TetraPrima is a more consistent fish food than Aquarian Flakes, and this may be due to a different “Primex” manufacturing process.
From the analysis of variables, Freeze Dried Brine Shrimp contains the most protein (48 -52%) (14) and therefore would suggest that feeding the fry this food would show the most growth. The results have shown that there is a significant diffe rence between aquarian flakes (which has the lowest protein content of the processed foods tested) and Brine Shrimp which supports the prediction that protein content of food determines how fast the fry grows. This follows on from salmon feeds which have a higher protein content for fry to encourage growth (2). Unfortunately, it is not possible to measure the nutritional content of live/natural foods although from the results, we could assume that it contains more protein than Aquarian Flakes though less than TetraPrima and Freeze Dried Brine Shrimp.
Evaluation
Systematic Errors
Systematic errors alter the end result by the same amount each time and because of this, any correlation shown by the experiment would still show. This means that the validity of the experiment would not be affected should systematic errors occur. Reliability of the experiment however would be affected by systematic errors because different results would be gathered should the experiment be repeated. Systematic errors in this experiment included;
1. Water composition; The water used for this experiment was sourced from the South East of England and this water supply is notorious for being very hard in composition. All the fry in this particular experiment were kept under the same water conditions, however, should the experiment be conducted at a location with a different water supply, the results may be different.
-
Water Temperature; The thermometer used in this experiment may not have been calibrated properly, and thus may have given an inaccurate result each time the temperature reading was taken to ensure that it remains constant. An error in the thermometer would result in the experiment losing its reliability should it be repeated.
-
Calibration of rulers; Length was the primary means of measuring the growth of the fry, and the same ruler was used to measure all the fry in this experiment. A slight error in the ruler s measurement would cause all the measurements made in this experiment to be inaccurate by a repeated amount.
-
Determining length of fry; This experiment measures fry from the tip of their head to the end of the caudal peduncle. This is important to consider as this experiment ignores the growth of
the fry s caudal fin. Other experiments may take the caudal fin into account when measuring length. Depending on the growth patterns of the fin, this could either be a systematic or random error.
Random Errors
Random errors are caused by the experimenter in most cases and thus are sometimes called human errors. There is no repeated pattern when random errors occur and thus are likely to affect any correlation shown by the experiment. It is extremely important to take random errors into
account when conducting experiments with a low margin of error as this can be masked by random errors. Because random errors affect the correlation of the end results, they both lower the validity and the reliability of the experiment.
5. Determining length of fry; It can often be difficult for an experimenter to mea sure the length of the fry as each fry would have a slightly different shape or details. Length of fry was measured from the tip of the head to the end of the caudal peduncle (the base of the caudal/tail
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fin). For example, the caudal peduncle in some guppi es tends to tilt downwards due to the weight of their enlarged caudal fin and this may aff ect their measurements.
-
Mass of food given; It is necessary to handle very small amounts of food when dealing with fry and it is very easy to lose what appears to be a very small fraction of the total food given. This however can make a big difference in terms of the fry s scale.
Contamination; Due to the close proximity of the experiment tanks (in an effort to keep
- conditions the same for all tanks), there is a chance of contamination where food intended for one tank may fall into another. This can be particularly problematic when feeding live foods such as mosquitoes as these are very mobile.
Variation in nutritional content of Live Foods; Live foods such as mosquito larvae and
- daphnia vary greatly in nutritional value depending on their condition etc, and it is very difficult if not impossible to judge without higher end equipment how these foods compare to the
processed foods.
Genetic variation of individual fry; Differences in the fry s genetic makeup can affect their metabolism and determine their mass gain during the growth period. This error cannot be
- avoided unless cloned individuals are used, however with the basic equipment available as well as ethical issues related to this,
Ethical Issues
This experiment carried few ethical issues in terms of procedure, as all the fry are kept in optimal conditions with the added protection of being in captivity (being safe from predators). In fact, their survival rate would be much higher in this experiment than in the species tank they are normally kept in, as larger guppies would have eaten the smaller weaker fry. The only issue would have been restricting their diet, however, the food sources used provided all the nutrients they require, but in slightly different amounts.
It can be argued that the fry have been kept in unnatural conditions and the bare transparent tanks they are kept in can cause considerable stress compared to the species tank they are normally kept in which has opaque walls. This was necessary however to ensure that the tank can be maintained easily and prevent the growth of bacteria and algae which can potentially serve as an additional food source, reducing the validity of the experiment. This problem was somewhat alleviated by keeping the fry in a sizeable tank.
The size of tanks the fry are kept in can have a large impact on their wellbeing. Even if water quality is carefully monitored, it is important to ensure that each animal has enough personal space. This is because even though guppy fry prefer to shoal and aren t territorial, they require a physical space between them to avoid stress. The same concept has also been shown in humans and other animals such as deer; research has found that deer kept in overcrowded conditions tend to live shorter lives regardless of diet or infection and human violence is much more prevalent in overcrowded conditions (12).
Culling of deformed fry has been debated, i.e. “We should care for them as we have the resources to do so”. Keeping deformed fry and allow ing them to breed would cause future generations in the gene pool to suffer from the same problems, and deformities such as spinal problems or belly-sliding would be painful and also make them vulnerable to other boisterous individuals in the tank. Deformed fry usually never survive for more than 2 weeks, and it is important that if they are to be culled, it is done as humanely as possible. There are many methods of culling fry, including temperature shock, destruction of the brain or anaesthetic overdose, each method works for different species/sizes of fish.
The preferred method of culling guppy fry is to immerse the fry in a 1 drop per litre emulsion of clove oil ( 70% eugenol) which acts as an anaesthetic to allow the fry to “sleep”. Once gill movement slows, 100ml of Vodka (37.5% ethanol) is then added to kill the fry in the sleep state.
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The fry are then kept in freezing water which guarantees death (doing this is preferred as tropical fish do not “hibernate” in cold conditions like cold -water fishes do).
Bibliography
1)
Article discussing various methods of culling fish. http://www.wisegeek.com/what-is-the-most-humane-way-to-euthanize-a-fish.htm Date: 26/11/10
2)
Feeding the Fish
WWF and the Scottish Wildlife Trust Joint Marine Programme. Also commissioned by the RSPB Scotland and work conducted by independent consultants Poseidon Aquatic Resource Management LTD (1-39)
Date: 26/11/10
3)
Final Report
Written by Dr. Alejandro Buschmann, Dr. Barry A. Costa-Pierce, Dr. Stephen Cross, Dr. Jose Luis Iriarte, Dr. Yngvar Olsen and Dr. Gregor Reid. (2-68)
Nutrient impacts of farmed Atlantic Salmon (Salmo salar) on pelagic ecosystems and implications for carrying capacity
Date: 26/11/10
4)
Cornell University - Chronicle Online Written by Susan S. Lang
www.news.cornell.edu/stories/Dec05/salmon.ssl.html
Article discussing the health risks of consuming farm raised Salmon Date: 26/11/10
5)
WWF Binary Item; State of Information on Salmon Aquaculture feed and the Environment by Albert G.J. Tacon Ph.D (1-57)
Report discussing the quantity and quality of aquafeed used in aquaculture. Date: 26/11/10
6)
The State of World Fisheries and Aquaculture 2008 Part 3; Highlights of Special Studies Report on global aquaculture (113-149)
Date: 26/11/10
7)
Science Magazine - Ecology, Nature s Subsidies to Shrimp and Salmon Farming http://www.sciencemag.org/cgi/content/full/282/5390/883?maxtoshow=&HITS=10&hits=1 A report identifying use of natural aquafeed in commercial fish farming
Date: 26/11/10
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8)
Aquarticles - Diseases Transmitted to Humans Notes written from talks by Adrian Lawler, Ph.D
Article describing the number of diseases which can be transmitted to humans from aquatic animals and their symptoms
Date: 26/11/10
9)
What has gone wrong with salmon farming in the Broughton Archipelago? www.raincoastresearch.org/salmon-farming.htm
Article discussing the problems associated with salmon farming Date: 26/11/10
10)
Tropical Fishlopedia (ISBN: 1582451664) Published by Interpet, 2000 Illustrated/Reprint edition
Book written by Mary Bailey and Peter Burges on the care of Tropical fish. Also contains extensive information on tropical fish anatomy and bodily func tions.
Date: 26/11/10
11)
Guppy Designer www.guppydesigner.com
Enthusiast website based around breeding various strains of guppies, also contains brief information on the guppies digestive system. (The website for this URL has recently changed and the information from the former website is no longer available).
Date: 24/11/10
12)
Body Language by Allan Pease (ISBN: 0859694062) Published by Sheldon Press, 1984
First edition
Provides brief information on the effects of overcrowding on animals and humans Date: 28/11/10
13)
Dietary Supplement Fact Sheet: Vitamin D
Provides extensive information on the health risks/benefits of vitamin D as well as it s sources http://www.webcitation.org/5Rl5u0LB5
Date: 28/11/10
14)
Protein content of Freeze Dried Brine Shrimp http://www.americanaquariumproducts.com/BrineShrimp.html Date: 02/01/11
15)
Scientific Journal providing information on Omega 3 and it s effect on heart disease http://circ.ahajournals.org/cgi/content/full/106/21/2747
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Date: 06/01/11
Evaluation of Resources Used
The resources used to support this report had their inherent problems. For example, the WWF binary items could not be relied upon entirely for giving fully balanced arguments, even with their information gathered from independent consultants. Many of the binary items tend to bias towards the negative aspects of salmon farming as well as emphasising the statistical information in context to the environment. For example, when talking about the substitution of fish oils for vegetable ones, the article immediately states the possible clearance of large areas of rainforest to suit the demand.
Some articles state that certain types of farmed salmon can only be eaten a certain number of times per year before the toxic effects of the contaminants they harbour take hold. It is however unclear as to the concentration of these toxins needed to induce their harmful implications and this figure could be exaggerated as the figure could be so mewhat subjective depending on the individual.
Dealing with ethical issues such as euthanasia requires informed sources of information to ensure that they are dispatched in the most humane way possible. The article found on culling fish tends to draw on previous experiences rather than scientific evidence. It can also be argued that it isn t entirely possible to guarantee the humane dispatch of fish due to the lack of indicators showing signs of pain etc.
Appendix 1: Risk Assessment
Like all experiments dealing with biological organisms, this experiment carries health risks. Aquatic fish have been known to carry certain strain s of Tuberculosis which can infect humans, causing tissue damage, especially in the skin where the bacteria can enter cuts and abrasions (8). Fish waste may also harbour bacteria and parasites, and certain parasites with complex life cycles may be able to use our bodies as hosts. The risks of parasites in captive fish are considerably lower though due to the lack of contact with the ecosystem.
The risk of zoonosis (cross infection between human and animal) can be greatly reduced by quarantining new individuals for several weeks before they are introduced to the main tank. This would allow time to observe the individual and ensure that they are disease and parasite free (any infection would have developed to a visible stage for treatment in this time). Risk of infection can further be reduced by reducing the interaction between the main tank and the wider ecosystem (i.e. By feeding live foods which have either been sterilised or grown independent of the wild) and limiting the time of contact between bare skin and tank water. Tank maintenance should also be avoided if direct water contact with cuts and grazes are likely.
Physical risks are generally scarce in this experiment as guppy fry and adults are not capable of inflicting any serious injury. The equipment used however does pose a small risk. Water pumps and filters in the main tank for example have fast s pinning motors and impellers which operate below the water surface, and it is important to ensure that these devices are switched off when putting hands into the tank. It is also important to ensure that all wiring is properly laid out with enough “slack” and that all insulation is in place before underwater operation.
The fry tanks pose fewer risks than the main tank. For example, they are made of lightweight plastic and electronic equipment (e.g. the air pump) are kept out of the water. There are however risks associated with this. The air pump for example works using a vibrating diaphragm and if this
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ruptures, the electromagnet may overheat due to lack of air flow. Because the diaphragm is very delicate and operates at high speed, it is important to ensure that pressure in the tubing is kept to a minimum by keeping the pipes at a sensible depth and allowing excess output to “bleed” rather than clamping it completely. It is also important to ensure that the air-line is fitted with a valve an d the pump itself placed above water level to prevent water from being siphoned into the air pump in the event of failure.
Appendix 2: Full Data Set
