Influence of Amount of Phytoplankton to Gizzard Shads Body Weight

This paper tested the mean differences of percentage increase in Gizzard shads (Dorosoma cepedianum) body weight with 100 percent, 80 percent, and zero percent amount of phytoplanktons relative to experimental fishes body weight in a laboratory experiment.  Forty five aquaria at 15 each treatment, with lake water as aquarium water, with one experimental fish each were used.  The results confirmed that higher amount of phytoplanktons available as food for the experimental fishes increased their body weights.

Keywords  Gizzard shads (Dorosoma cepedianum), phytoplankton, percentage body weight

Oceans and rivers are mans primary sources of food.  Every time fish is served as part of a meal, one wonders what biosynthesis and pre-predator food chains make possible the growth of fishes.  The implications of prey-predator food chains to the survival of big fishes become relevant when one thinks of the necessary biological settings so that marine environment can sustain a balanced ecosystem.

Food web in water environments begins with microscopic phytoplanktons, which are the foundation of the marine food chain. (Herring D, 2010).  These are eaten by small fishes, which are eaten by big fishes, which are eaten by still bigger fishes. Thus the food chain is a cycle of producer  consumer interactions. The food chain necessitates that organisms in the higher food ladder should be fewer in number than those at the lower levels since the efficiency rate at each level is only 10 percent. This means there is 90 percent loss of food value as food is consumed from the lower ladder by those in the higher ladder. (Corey  Beutel, 2009).

A direct implication of increasing pollution of lakes and oceans on the food chain is the need to ensure that the bottom level producers in the food chain should proportionately increase in number and biomass. This study will use Gizzard shad (Dorosoma cepedianum), a filter feeding omnivore prey fish abundant in U.S. waters.  (Watson, Bayne, DeVries  Williams, 2004). Shad, Hickory Shad, Herring, Skipjack are other names for Gizzard shad. These fish species thrives in large lakes and in marine environments. While it is considered worthless as a food fish (Texas Parks and Wildlife Department, 2009), it is food to some other fishes, hence, important in sustaining other fish species.
Question  Is the increase in body weight of Gizzard shad (Dorosoma cepedianum) influenced by the amount of phytoplanktons available

Hypothesis  There is a higher rate of increase in body weight of Gizzard shad (Dorosoma cepedianum) with increasing amounts of phytoplanktons available as food.

Prediction  If availability of phytoplanktons is supplied in excess of 90 percent, of the body weight of Gizzard shad, then body weight increase of Gizzard shad will be higher.

Controlled Experiment and Methods
The experiment will consist of 45 aquaria with one experimental fish each.  Fifteen aquaria each will be supplied with 100 percent (Treatment 1), 80 percent (Treatment 2), and 0 percent (Treatment 0) amount of phytoplanktons based on the fishes body weight. T0 is the experimental control treatment. The 45 fishes will be randomly assigned to the aquaria.

The variables held constant will be the fish species in terms of its age and sex. The following variables are to be the same for all 45 aquaria  dimension of the aquaria, water, water level, water temperature, rate and type of aeration, and amount of light. The experimental fish species will be (Dorosoma cepedianum) all fishes will be from the same father and mother raised in captivity all males 18-day old (i.e. 14 days after they are hatched) Gizzard shad grown in the same common aquaria will be used for the experiment. The same lake water will used for the aquaria to facilitate completion of the experiment.
Change of lake water will be done every 7 days. Phytoplanktons will be cultured and harvested to ensure that the same species of phytoplanktons is used throughout the experiment.  The variable to be tested is the amount of phytoplanktons influence on the fishes body weight.

The following aspects of the experiment will be controlled  water level, aeration, room and water temperature, data collection time, and procedures for providing the phytoplanktons and for data collection.

Data to be collected will be  amount of phytoplanktons, initial body weight, and succeeding body weight.  A final percentage increase in body weight will be computed from the initial and final body weight after 28 days. The experiment will run for 28 days and body weight measurements will be made every two days with corresponding supply of phytoplanktons.  Below are the hypothetical data and computed results.  The T-computed values were computed through calculator for t-test. (Dimension Research Inc., 2003).

Percent Increase in Body Weight
T1 (100 percent phytoplanktons) 140, 125, 130, 210, 190, 110, 109, 100,115, 120
      100, 108, 95, 105, 110
T2 (80   percent phytoplanktons) 30, 35, 60, 48, 50, 20, 15, 40, 25, 30, 10, 5, 25, 30, 8
T0 (0     percent phytoplanktons) 15, 20, 30, -5, 0, 12, 8, 6, 35, 10, -4, 5, 12, 8, 25

TreatmentMeanStandard DeviationT-computedT-tabulated, 28 df, alpha0.05RemarksTreatment 1124.4733.1310.07132.04841Treatment means are significantly differentTreatment 228.7316.06TreatmentMeanStandard DeviationT-computedT-tabulated, alpha0.05RemarksTreatment 1124.4733.1312.42442.04841Treatment means are significantly differentTreatment 011.811.66TreatmentMeanStandard DeviationT-computedT-tabulated, alpha0.05RemarksTreatment 228.7316.063.30392.04841Treatment means are significantly differentTreatment 011.811.66

Based on the results, the hypothesis is accepted.  That is, increasing amount of available phytoplanktons as food for Gizzard shad (Dorosoma cepedianum), a filter feeding fish, increases its body weight.  To refine the generality of this conclusion, the percentages of phytoplanktons can be in the range of zero (as experimental control treatment), 60, 70, 80, 90, 100, 110.  This refinement in the treatments will ensure that there is no abrupt difference in percentages of available phytoplanktons, except for the experimental control treatment.  Other food fish species can be used as experimental unit to have a more practical application of the results. Also, replication experiments for other filter feeding fishes can generate a definitive conclusion of the influence of amount of phytoplanktons on fish body weight.


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