Shrimp life
Shrimp lifeI. Purpose
The purpose of our experiment was to find how diet affects the growth rate of Macrobachium rosenbergii. The two variables included within our experiment were the use of two different food particles: protein and fatty substances with a separation net to separate the pairs of shrimp. The goal of our experiment was to find where shrimp will grow the largest, in a region where the particles of food are fatty, or where the particles are high in protein.
II. Background
Shrimp are structurally similar to lobsters and crayfish, but they lack enlarged pincers and are flattened laterally instead of horizontally. The animals are usually transparent or are green or brown in color. They have thick-muscled abdomens, which they contract rapidly in making their sudden, backward-swimming escapes. (The shrimp meat served in numerous dishes, an important product of the fishing industry, is the curved muscle extracted from the abdomen.) The animals have eight pairs of appendages on the thorax: the front three, called maxillipeds, are mouthparts used for feeding; the rear five, called pereipods, are used for walking. The abdomen contains five pairs of swimming legs, called pleopods, and a fanlike tail.
Many small shrimp are harvested from the cold waters of Iceland, Greenland, and Canada. Today, cultured or farmed marine shrimp play an important role in supplying the world’s shrimp demand. Total wild and farmed shrimp harvest accounts for less than 5 percent of the total world fisheries harvest. Even so, shrimp has a very high commercial value and is the most important species group in world fisheries trade. The United States spends more on shrimp purchased from around the world than on any other imported fishery product.
The amount of shrimp consumed in the US has doubled in the last decade to some one billion lbs a year, making it the one of the most popular seafoods in the US. In 1997, per capita consumption of shrimp in the U.S. was 2.7 lbs., second only to tuna (at 3.1 lbs.) among seafoods. The price of a pound of shrimp dropped from $14 a decade ago to $5 today. Restaurants purchase 80% of the shrimp in the US.
Western Europe consumed 400 million lbs of shrimp in 1993. In Western Europe, 53% of the shrimp imported in 1992 was a cheaper cold-water variety exported by Denmark, Norway and Iceland. 14,414 more metric tons were imported than Japan, but, because it was the cheaper cold-water variety, the value of the imports was US $776,270 less than Japan's.
Japan consumes the most shrimp per capita of any nation in the world. In 1993, 700 million lbs of shrimp were consumed in Japan. Shrimp sales are less tied to fluctuations of the economy in Japan. While the price elasticity for shrimp in the US is 2.04 (a one percent fall in price results in a 2.04 percent increase in consumption), the price elasticity in Japan is 1.03.
There are 342 species of shrimp of commercial value. Of those, 109 are Penaeid species, the dominant type of warmwater shrimp; 34 are Pandalids, or coldwater shrimp. Because they're primarily deepwater animals, coldwater shrimp do not ingest mud, sand, etc., with their food, one reason their veins are clearer than those of warmwater shrimp. Of the estimated 733,000 tons of farmed shrimp grown in the world in 1994, the top species, by far, was black tiger shrimp Penaeus monodon at 61%, followed by Western white shrimp Penaeus vannamei at 15%. Thailand is the top foreign shrimp supplier to the U.S. market, shipping more than 80,000 tons of product in 1994. Other major suppliers are Ecuador (48,100), Mexico (22,900), China (22,800) and India (22,600). The average American consumes around 2.5 pounds of shrimp a year, more than Europeans at 1.8 pounds per person, but far less than the Japanese at 8.8 pounds.
Shrimp generally grow bigger in warmer waters and like the darker seas. They generally hide under seashells and “claim” territory to protect it. When no food is available shrimp fight very commonly and eat each other. They are cannibalistic. When shrimp shed their “skin” they then eat it, it is a good source of protein and calcium.
Shrimp, unlike fish, seem to be very docile towards movement and sound. They seem to not be aggravated or scared of such things. The only time our shrimp seemed to spasm is when we touched them, or tried to catch them.
III. Design
Model A:
Model B: Model C:
Model D
The design of our tank had a major influence on the outcome of both data and well-being designated to our shrimp. (Model A) shows a picture of the entire tank. We separated the two sections to get our desired question answered. We used a net held together by staples and PVC pipe to make sure there was no way the shrimp could change sides or receive food from the other side.
We decided that it was important to build structures that the shrimp could hide under and protect themselves under. We decided to use rocks for arithmetic reasons as well as the fact that it was a very easily obtained material. Shrimp tend to guard their territory so we made several layers that each shrimp could designate as its own.
Light was a considerable determination of shrimp growth. Shrimp tend to do better in dark areas, so we isolated them from light as much as possible by having a solid top and forming a growth of plant life not illustrated in the pictures above the tank.
The filter system we used was quite elementary. We decided that over feeding the shrimp would cause a buildup of sediments beneath the tank, therefore we decided to feed them the proper amount for daily growth and not to overfeed them over the weekend. We used a device that uses suction and gravity to periodically clean the bottom of the tank, as well as giving periodic water exchanges to keep everything normal. We made sure that both the left side (model C) and the right side (model D) received equal weights of food so that all data was accurate. Fortunately no modification of our tank was required throughout the experiment.
IV. Procedures
The testing of and collection of growth research data was the most important variable included within our experiment. We used various devices to help us discover such things as pH and salinity. Included with these devices came a need of knowledge of how and why to use them.
For testing pH we used a test tube filled with the water from the tank. We then added two to three drops of universal indicator. We let the solution mix and then compared the color to the color chart provided. We then concluded the pH level of the tank. Testing for ammonia was very similar except we would add two drops of Nesslar Reagent instead of the universal indicator.
Testing for nitrate and nitrite were both very complicated processes. To measure them we needed a Direct Reading Spectrophotometer. Testing for nitrite required the program to be on number 371 while nitrate required program number 355. After using distilled water as a base, you would dial to 507 nm for nitrite and 500 nm for nitrate. We made sure we filled a sample cell with 25 ml of our water and 25 ml of distilled water. One important thing we made sure not to forget was to press shift 7 for nitrate after the timer beeped.
Dissolved oxygen and temperature are both tested using the YSI 55 Dissolved Oxygen Meter. We simply turned it on and stuck it in the tank. Immediately the temperature was recorded. Next we waited until the D.O. reading settled and we took the reading at the top and bottom of the tank, then took the mean. When testing salinity, we filled up the Sea Test Full Range Specific Gravity Meter and watched until the thimble settled. We then recorded the specific amount of ppt's of salinity.
The most important data we calculated was the weight gain of each shrimp. To measure them we would take them directly out of the tank on a net and place them directly on the scale. We would then take the weight and record it and put the shrimp in a jar of water to make sure we didn't weigh the same shrimp twice. Next we would get another shrimp and repeat the process until we weighed all the shrimp.
V. Results Chart A:
Chart B:
Chart C:
Chart D:
Chart E:
Chart F:
Chart G:
Chart H:
The results provided important information about the underling question. The data showed how variables can affect the growth rate and how simple changes in temperature can have an effect on growth rate. They also depict that there is no true medium, as all data results can be different depending upon the shrimp’s environment.
Chart A depicts a picture form of the data we acquired using the spectrometer. It shows a steady decline in nitrate levels over the life of our tank. All the levels are in the safe zone (below 0.5 ppm) and shouldn’t have affected our experiment in any way. High nitrite can be due to overfeeding and parasite/diseases. Luckily, since we watched our tank so diligently, we ran into no problems.
Chart B shows the inclination and declination of our temperature in the water. I noticed that as the temp rises, the food conversion ration rises. This may be just a fluke, but based on our data, it is highly likely.
Chart C shows the concentration of dissolved oxygen in our tank. Although we came close to a fatal level in our second test, we decided to increase the aeration, which brought the D.O. back to normal.
Chart D shows the levels of pH in our tank. We had a very low pH during the entire experiment, but decided to reduce food levels on 09/12/99 which brought the pH slowly back up. Good levels are those above 6.8.
Chart E shows the salinity in our tank. The levels seamed to be ok as they were all really low, and we had no problem associated with the salinity in our tank. It seemed to be on a gradual rise throughout the testing period. I assume this is because of the salt on the food.
Chart F shows how The fat diet had a much greater increase in weight over the testing period. This is the conclusion and answer to our experiment. I believe that my hypothesis was incorrect in guessing that protein would bring a greater weight. I suppose fatty foods are digested slower.
Chart G shows the food conversion ratio, which is slightly higher for the fat group throughout the experiment. Again I believe this is due to digestion, and as the shrimp got bigger they needed more food. It was a process in which protein could never catch up.
Chart H shows the nitrate levels though out the experiment. The results seem to be ok as they didn’t reach above 7 ppm over the duration of the testing. I believe that our constant water exchanges prevented anything of this nature from occuring.
VI. Discussion
I have learned a lot about shrimp including how valuable they are to today’s restaurant business. I have also learned how important setting a control is. One simple difference and the results can have a huge variance. The problems that occurred were easy to solve. Such problems included lighting, and setting up a food intake ratio that was appropriate. I believe we could have avoided these problems by researching shrimp more at the beginning, and anticipating the future more often. If I were to set up the same experiment again I believe I would use a different separating device. We used a net, and we could have used a solid piece. We could have also used different tanks, but then there would be a variance in results due to water quality. A larger tank would have been greatly appreciated. Thank you very much.