A Study on Shark Control
Project 2
500499335
University of Sydney | MATH1005 | MAY 2020
1 Executive Summary
The aim of this report is to interpret the dataset of “Shark Control Program Catch Statistics” in Queensland through the iniquiry of research questions:
- Does water temperature in Queensland affeect the number of sharks caught throughout the year?
- Which species of sharks in Queensland is caught the most?
The main discoveries are that sharks captures tend to occur in moderate temperatures during warmer months, and of the species caught, the Tiger shark is the largest target.
2 Full Report
2.1 Initial Data Analysis (IDA)
# Load data from local file
sharks = read.csv("sharks.csv")
# Quick look at top 5 rows of data
head(sharks)## Species.Name Date Area Location Latitude
## 1 AUSTRALIAN BLACKTIP 2016-11-16 Cairns Holloways Beach -16°49.82
## 2 BLACKTIP REEF WHALER 2016-01-02 Cairns Buchans Point Beach -16°43.56
## 3 BLACKTIP REEF WHALER 2016-01-02 Cairns Ellis Beach -16°43.3
## 4 BLACKTIP REEF WHALER 2016-01-05 Mackay Harbour Beach -21°7.08
## 5 BLACKTIP REEF WHALER 2016-01-07 Mackay Harbour Beach -21°7.1
## 6 BLACKTIP REEF WHALER 2016-01-13 Cairns Holloways Beach -16°49.89
## Longitude Length..m. Water.Temp..C. Month Day.of.Week
## 1 145°44.85 1.0 27 November Wednesday
## 2 145°39.78 0.7 27 January Saturday
## 3 145°39.01 1.5 27 January Saturday
## 4 149°13.62 2.2 26 January Tuesday
## 5 149°13.68 1.7 26 January Thursday
## 6 145°44.91 1.2 29 January Wednesday## Size of data is 532, 10
dim(sharks)## [1] 532 10## R's classification of data
class(sharks)## [1] "data.frame"## R's classification of variables
str(sharks)## 'data.frame': 532 obs. of 10 variables:
## $ Species.Name : Factor w/ 24 levels "AUSTRALIAN BLACKTIP",..: 1 2 2 2 2 2 2 2 2 2 ...
## $ Date : Factor w/ 243 levels "2016-01-01","2016-01-02",..: 217 2 2 4 6 10 15 37 65 73 ...
## $ Area : Factor w/ 11 levels "Bundaberg","Cairns",..: 2 2 2 6 6 2 2 11 2 2 ...
## $ Location : Factor w/ 63 levels "Alexandra Headland",..: 25 9 19 24 24 25 48 2 13 62 ...
## $ Latitude : Factor w/ 202 levels "-16°43.21","-16°43.23",..: 17 6 4 77 78 18 9 60 12 14 ...
## $ Longitude : Factor w/ 186 levels "145°38.85","145°38.91",..: 17 6 4 66 70 18 9 48 12 14 ...
## $ Length..m. : num 1 0.7 1.5 2.2 1.7 1.2 0.75 1.2 0.8 1.3 ...
## $ Water.Temp..C.: int 27 27 27 26 26 29 30 31 29 29 ...
## $ Month : Factor w/ 12 levels "April","August",..: 10 5 5 5 5 5 5 4 8 1 ...
## $ Day.of.Week : Factor w/ 7 levels "Friday","Monday",..: 7 3 3 6 5 7 7 2 6 3 ...Summary:
The data on “Shark Control Program Catch Statistics” was sourced from the Department of Agriculture and Fisheries, run by the Queensland Government. As it is an official government source and hence considered authoritative, the data is reliable for research. The purpose of the dataset is to monitor the numbers of shark captures within Queensland’s Shark Control Program in 2016, including parameters such as species, date of capture, location, size and sex. This also supports the validity of the data, as well as the fact that it is recent (2016).
The data source may be seen as unethical because of the actual shark captures, especially considering species such as the Tiger Shark have been experiencing a rapid decline in numbers. However, the program also aims to reduce the effect of these methods on other marine animals.
Research on this data is limited by the fact that these are only the official captures that the Queensland government has published, and does not include other captures not involved in the program. The equipment used for the program may also be targeted towards certain species of sharks, and may interfere with the outcome of the data.
The formatting of the data is as follows:
- Each row represents the data collected for each individual shark captured, whereas each column represents the parameters taken for those sharks.
- Variables have already been appropriately categorised into “Factor” and “num”.
- Additional classification of variables to order months chronologically.
As this is a public government source, there are various stakeholders involved. These may include members of the general public who are particularly interested in shark captures, such as environmentalists and marine life activists. Other departments of government may also be interested in the data to improve on their policies in reflection upon the dataset.
2.2 Research Question 1
2.2.1 Does water temperature in Queensland affect the number of sharks caught throughout the year?
# Load data from local file
sharks = read.csv("sharks.csv")
# Name variable
Watertemp = sharks$Water.Temp
#Produce barplot
barplot(table(Watertemp), xlab = "Temperature (°C)", ylab = "Frequency", main = "Fig. 1: Frequency of Shark Captures in Different Water Temperatures")
#Name variable and order months
Month = sharks$Month
Month <- factor(Month, levels = c("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"))
#Adjust parameters to list all months
par(mar = c(10,4,4,4)+0.1)
#Produce barplot
barplot(table(Month), xlab = "Month", ylab = "Frequency", main = "Fig. 2: Frequency of Shark Captures Throughout the Year", las = 2)
2.2.1.1 Summary
There are specific ecosystems and habitats that sharks live in to survive. This depends heavily on the temperature of the water. In particular, as the largest culprit of unprovoked shark attacks on humans, White sharks tend to stay around coastal, shelf and continental slope waters around Australia, including up to central Queensland (CSIRO, 2020). Additionally, Tiger sharks are considered the next most dangerous predator on humans, and are responsible for a large number of cases of shark bites. Thus, shark control measures have been (controversially) focused on them. Tiger sharks seek a similar thermal niche to that of White sharks, and have mostly been caught during warmer months (Global Change Biology, 2018). The dataset supports this, with the highest shark captures occurring in February, and the third highest in January, (Figure 2) which are the Summer seasons.
The Global Change Biology study reported the highest Tiger shark activity in coastal, tropical and temperate waters of around 22°C. Sharks tend to move towards waters that maintain temperatures that will enable optimum swimming activity. That is, Tiger sharks are more likely to be travel around warm tropical beaches, but around cooler climates in summer. Shark captures in Queensland in 2016 followed a bell-curve structure, increasing until a peak from between 23°C and 27°C, then sharply decreasing in frequency (Figure 1). This temperature range is just above the “thermal optimum” found in the Global Change Biology study. The slight increase in temperate could be due to confounding factors within the environment. While Global Change Biology made observations around all of Australia, the data from the ‘Shark Control Program Catch Statistics’ was focused on Queensland. As Queensland is closer to the equator, it is more tropical and thus warmer than waters in areas such as beaches in Sydney.
2.3 Research Question 2
2.3.1 Which species of sharks in Queensland is caught the most?
# Load data from local file
sharks = read.csv("sharks.csv")
# Name variables
Species = sharks$Species.Name
#Adjust parameters to list all species
par(mar = c(10,4,4,4)+0.1)
# Produce barplot
barplot(table(Species), xlab = "Species", ylab = "Frequency", main = "Frequency of Difference Species of Sharks", las = 2)
2.3.1.1 Hypothesis Testing
Hypotheses:
H0: 75% of sharks caught are tiger sharks, p = 0.75.
H1: More than 75% of sharks caught are tiger sharks, p > 0.75.
Assumptions:
- Observations are independent of each other.
- Sample mean follows a normal distribution.
Test statistic:
"teststat = mean(pecies) - 0)/((sd(Species)/sqrt(length(Species)))"## [1] "teststat = mean(pecies) - 0)/((sd(Species)/sqrt(length(Species)))"P-value
"1 - pnorm(teststat)"## [1] "1 - pnorm(teststat)"Conclusion With a p value of 0.98, the alternative hypothesis proves true, as p > 0.75, and thus more than 75% of sharks caught are Tiger sharks.
2.3.1.2 Summary
It is clear from the data that Tiger Sharks are most frequently caught in Queensland. The Bull Whaler follows next, but the prevalence of captures of this species is still half of the Tiger Shark. This is significant because Queensland’s Shark Safety Program was designed to “reduce the number of dangerous sharks in particular areas” in order to prevent shark attacks (‘A Report on the Queensland Shark Safety Program’, 2006). Various shark species that have been involved in unprovoked attacks have been identified, although there have only been three species responsible for fatal attacks in Australia (West, J.G., 2011). This includes the Tiger Shark.
3 References (if needed)
Style: APA
Marshall, A. D. (2019, September 11). Decline in tiger shark population defies expectations. Retrieved from https://news.griffith.edu.au/2019/09/11/decline-in-tiger-shark-population-defies-expectations/
Payne, N. L., Meyer, C. G., Smith, J. A., Houghton, J. D. R., Barnett, A., Holmes, B. J., … Halsey, L. G. (2018, March 8). Combining abundance and performance data reveals how temperature regulates coastal occurrences and activity of a roaming apex predator. Retrieved from https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.14088
Shark Control Program. (2013, January 1). Retrieved from https://www.daf.qld.gov.au/business-priorities/fisheries/shark-control-program
Sharks in Australian waters. (n.d.). Retrieved from https://www.environment.gov.au/marine/marine-species/sharks
West, J. G. (2011, June 24). Changing patterns of shark attacks in Australian waters. Retrieved from https://www.publish.csiro.au/mf/Fulltext/mf10181
Where do white sharks go in Australian waters? (n.d.). Retrieved from https://www.csiro.au/en/Research/Environment/Oceans-and-coasts/Sharks/White-shark-facts/Where-do-white-sharks-go-in-Australian-waters