Assessment of the Relation of Age, Height and Number of Gambusia Holbrooki

Assessment of the Relation of Age, Height and Number of Gambusia Holbrooki


Gambusia Holbrooki is a fish species also referred to as the mosquito fish. They are believed to have serious impacts on the population of the mosquitoes’ larvae found in shallow ponds, vegetated lakes, and even quiet waters. The mosquito fish are thus said to have great importance in the ecosystem as they aid in balancing the population of the prey they feed on. This goes a long way to a research of their use as biological control tools. To understand the mosquito larva, there is great need to have a study of their population. This study aims at identification and understanding of the age, height and statistical distribution of these larvae in their natural habitat. Various methods of data collection are used sampling being the most prominent. Tools used are majorly the fish nets which help in trapping the mosquito fish. The number of fish collected are observed and analyzed for the fore mentioned parameters (Russel 332)


Gambusiaame holbrooki is a ray-finned fish whose genus name emanates from a Cuban term Gambusino which refers to nothing. This was used in a joking context when fishers came home without fish. It survives in freshwater with a pH range of between 6 and 8. (Whiteside et al. 58). The maximum length of male mosquito fish is about 47mm while that of female ranges up to 80mm. They are considered larvivorous since their extreme diet is the mosquito larva. In appearance, they assume a gray color and a large abdomen. They also possess a round caudal fin and dorsal fins (Russel 345).


This research aims at assessment of the size, age, and population of the Gambusiaame holbrooki. These parameters are crucial in understanding the adaptability and means of survival of the mosquito fish in the population. Their number helps in an understanding of their impact on the environment and impact of environmental conditions on their number.


Sampling methods

During the collection of the mosquito fish, the samples were collected using various gears. First, the water body for collection of the sample were selected randomly. The trawl net was selected as the fishing before the actual specimen collection. Fish were caught randomly, observed for the parameters of the study and then returned to the water. All the observations were recorded as seen in the life history results table. Sample collection was done in triplicate and the averages used as the raw data.


The areas covered was just a representation of the entire area where fish are located. The specific population is determined by multiplying the sample collected by the whole field then dividing by sample area. The age of the mosquito fish is determined by having a thorough assessment of the vertebrate (Rupp 234).  The bony structures are compared so as to come up with an estimate of the age of the fish. In this case, the scales were used to assess the age of the fish. This was done by determining the number of annuli on the scale. The spacing between every ring was also observed and its proportionality to fish growth determined. The scales are used in this method because they are never toxic. The disadvantage of this approach is the possibility of underestimating the age of the older mosquito fish (Whiteside et al. 108).

The life table constructed for Gambusia Holbrook is that of age, height, and length. The fish are put into classes. The samples in each grade have almost similar features regarding age, height, and duration. The statistical table below is constructed because it makes it easy to make a comparison of the mosquito fish or even extract information for various analysis.



Figure 1; life table for the year 2016

Length (mm) Age Number of sampled
9-12 2 79
13-15 52 330
16-18 68 376
19-21 171 310
22 + 140 135


            Figure 2; reference table for the year 2015

Length Age Number sampled
9-12mm 0 5
13-15mm 30 5
16-19mm 60 13
20-23mm 90 17
24-26mm 120 6
27+ 150 1


The net reproductive rate for population collected would be 79+ 135=214

While that of the provided sample is 5+1=6



The population of-of Gambusia collected and the one provided differ so much. This is an indication that the rate of growth was as high in the year 2016 as compared to the year 2015. The optimal age of sexual maturity is at about 60 years. At this level, the population starts reducing even as the age increases. This type of life table is chosen because it provides the best opportunity to make comparisons within the population. The comparison helps in making an informed opinion about the changes in the population.

Importance of Life Table

The life table is of great significance in the study of the ecology of a population. Their relevance cannot be underestimated as they are essential in determining longevity among the population. The table explicitly puts across the chances of surviving a particular age, the life expectancy of survivors and ratio of first birth to that in a particular cohort.


Works Cited

Whiteside, Bobby; Bonner, Timothy; Thomas, Chad; Whiteside, Carolyn. “Gambusia affinis western mosquitofish.” Texas State University. Retrieved 25 October 2011. 58-120

Rupp, Henry (1995). “Adverse Assessments of Gambusia affinis.” North American Native Fishes Association (NANFA). Retrieved 2 January 2012.

Russel, Sabin (12 July 2008). “Heatwave adds to West Nile danger.” San Francisco Chronicle. San Francisco, California: SFGate. p. B–1. Retrieved 3 January 2012. 322-345