Abstract
In this paper, we will be discussing the Gambusia holbrooki. We will be conducting experiments to test our hypotheses: as the age of G. holbrooki increase so does the mortality rate. We also analyzed our data that is quantified in the life table. In this experiment we went to the field and gathered our subjects and observed them to obtain our needed information. We then compared and discussed our findings.
Introduction
Gambusia holbrooki is a type of small fish that is commonly called the eastern mosquito fish. It lives in a habitat of freshwater more specifically ponds. It usually resides in the patches of rooted aquatic plants (Blanco et al, 2004). G. holbrooki is a native species of the United States and they have become invasive in other parts of the world where it was artificially introduced. G. holbrooki usually feeds on algae and detritus but when there is heightened completion they become more carnivorous and eat animal larvae and smaller animals. In this paper and during the field experiment we aimed to showcase the different stages in the life cycle of the eastern mosquito. I hypothesize that as the age of the fishes increase, the survival rate will decrease proportionally. My null hypothesis is that the survival rate will stay the same.
Methods
My team and me went to the pond at FIU and each group randomly collected thirty fish. To collect the fishes, we used nets. After catching the adequate number of fishes, we measured each fish with a marked ruler; we then released them back to their environment. With that measurement we were able to estimate the approximate age of each fish and compiled it into a list.
First we calculated the age of the fishes by taking their length measurements and multiplying it by eight then subtracting the product by sixty-eight. Next we calculated the survival rate by dividing the number of fishes alive in the age class by the number of fishes that are alive in the very first age class (l(x) = n(x) / n(0)). We calculated the number of offspring produced per individual fishes at each of the age class by multiplying the survival rate to our given fecundity data (l(x)*b(x)). We computed the age-weighted fecundity by multiplying the number of offspring produced per individual fishes at each of the age class by each age class. For the G. holbrooki we constructed a vertical life table because we were unable to actually follow the fishes for the entirety of their life i.e. from birth to death due to the impracticality of that scenario (Mulvey et al, 1994) If one is not following the entire life cycle of our study subject then you must construct one that is static and that only looks at the subject for only a single point of their life.
I found that the optimum age for reproduction was 120 days. The survival rate had a bit of an anomaly. The survival rate had some fluctuation maybe due to the size samples we collected. I conducted some statistical test to either support or reject my hypothesis.
Results
Table 1- Example 2: Vertical Life Table for a Gambusia holbrooki population
Table 2: Vertical Life Table for a Gambusia holbrooki population
Discussion
My R0 was significantly higher than the examples; as a matter of fact all of my data was higher except for r. Both populations are increasing as R0>1 but from my collected data, my fishes appears to produce more children in their lifetime. The generation time are actually quite close, there is a slight difference (mine is higher) in the period between each generation. The example’s intrinsic growth rate is actually higher probably because my R0 was so big and their mean generation time was smaller. Those differences are probably due to a difference in the sample size and the habitat in which we collected our samples.
We opted to create a vertical life table instead of horizontal one. We chose this type of life table because we only had a limited amount of time (specifically ~3hrs). Because of that constraint we had do choose the type of table where the data collected during that time can be used to generate a life table. Life tables are an essential part of ecology. A life table is packed full of pertinent information about the species of the research. A life table is essentially a summary of the birth and death rates for an organism at different points of their life cycle. Within the life table you can figure out the growth of a population, you can compare different life tables and see how populations have change or differ in different types of habitat or region. Life tables can also be practical and they can inform people of the best time that they can sustainably harvest animals, and they are used by insurance companies to estimate facts about their clients in order to maximize profit. Overall life tables are important for a lot of different reason as long as you know how to interpret it.
References
- Blanco, S., S. Romo, and M. J. Villena. 2004. Experimental study on the diet of mosquitofish (Gambusia holbrooki) under different ecological conditions in a shallow lake. International Review of Hydrobiology 89: 250-262.
- Mechanisms of sexual selection operating on body size in the mosquitofish (Gambusia holbrooki). Behavioral Ecology 3: 1-12.
- Mulvey, M., G. P. Keller, and G. K. Meffe. 1994. Single and multiple locus genotypes and life-history responses of Gambusia holbrooki reared at two temperatures. Evolution. 46: 1810-1819.
- Voronov DA, 2005. Calculating the intrinsic growth rate: comparison of definition and model. Medline.
- Al-Daham, N.K., Huq, M.F., Sharma, K.P. 1977Notes on the ecology of fishes of the genus Aphanius and Gambusia affinis in southern IraqFreshwater Biol.7245251
- Arthington, A.H., Marshall, C.J. 1999Diet of the exotic Mosquitofish, Gambusia holbrooki, in an Australian Lake and potential for competition with indigenous fish speciesAsian Fish. Sci.12116