1 Executive Summary

  • The aim of this report is to explore two research questions using the provided dataset. This report caters to those interested in the trend between sharks and water temperatures and focuses on two prompts: “Is there more risk of shark encounters during summer?” and “Do Bull Whaler sharks prefer warmer water than Scalloped Hammerhead sharks?”. After conducting a hypothesis test, it became evident that more sharks were captured in seasons other than summer. Research question two shows that bull whaler sharks prefer warmer temperatures in comparison to scalloped hammerheads. These results can be utilised to discuss the safety of recreational beach activities that can put lives of both humans and marine life at risk.

2 Full Report

2.1 Initial Data Analysis (IDA)

  • The data is sourced from Agriculture and Fisheries, Queensland Government and can be accessed through this link; https://www.daf.qld.gov.au/__data/assets/excel_doc/0013/300064/shark-catch-stats-2001-to-dec2016.xls. It is a record of shark encounters during the Shark Control Program at various beaches across Queensland, documenting the species, date, area, exact location, length, water temperature, month and day of the week. Since it is sourced from the government, the reliability and validity of the data can be accounted for. There are some ethical issues surrounding the sourcing of the data as it requires sharks to be captured and held in nets. This poses a threat to the marine life and it can be argues that this is an unjustified intrusion into the ecosystem. A possible limitation to this dataset is that it is not future proof and it will soon become outdated. Other issues include the constraint on location, as the data is only taken from Queensland and it is not an accurate representation of Australia. Potential stakeholders that can benefit from this dataset are beach-goers, who can gain an understanding of the amount of sharks in the water, marine biologists, scientists, the fishing industry and the tourism industry. There are 10 variables represented in columns in this dataset, their names and classification are displayed below. Each row is data collected on a single shark capture, thus providing a very detailed account of the encounter. The main variable used in this analysis is Water temperature (temp at capture), Month (month of capture) and Shark species.
## read in data
sharkrawdata=read.csv("sharks.csv", header = T)

## show classification of variables
str(sharkrawdata)
## 'data.frame':    532 obs. of  10 variables:
##  $ Species.Name  : chr  "AUSTRALIAN BLACKTIP" "BLACKTIP REEF WHALER" "BLACKTIP REEF WHALER" "BLACKTIP REEF WHALER" ...
##  $ Date          : chr  "2016-11-16" "2016-01-02" "2016-01-02" "2016-01-05" ...
##  $ Area          : chr  "Cairns" "Cairns" "Cairns" "Mackay" ...
##  $ Location      : chr  "Holloways Beach" "Buchans Point Beach" "Ellis Beach" "Harbour Beach" ...
##  $ Latitude      : chr  "-16°49.82" "-16°43.56" "-16°43.3" "-21°7.08" ...
##  $ Longitude     : chr  "145°44.85" "145°39.78" "145°39.01" "149°13.62" ...
##  $ 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         : chr  "November" "January" "January" "January" ...
##  $ Day.of.Week   : chr  "Wednesday" "Saturday" "Saturday" "Tuesday" ...


2.2 Research Question 1: Is there more risk of shark encounters during summer?

This section is looking at the number of shark encounters during summer, where the beach is used regularly, and winter, where there are not many people in the water. To properly assess, the dataset had to be manipulated to focus on moths and number of sharks, and then a new column was mutated into the data to classify the months. Summer is from December to February, whilst all other months are considered Not Summer for this analysis. A hypothesis test is to be conducted with the Null hypothesis being: There is less risk of shark encounters during Summer and, Alternate hypothesis being : There is more risk of shark encounters during summer. After conducting a Welch Two Sample t-test, the p value is given to be 0.2723 with a 95% confidence interval and a 5% significance level. The p value is far greater than 0.05, which means that the null hypothesis in this case is not to be rejected. This concluded that there is more risk of shark encounters during seasons other than summer. According to research, different species of sharks prefer different temperatures of water( Ball, 2022). The different species prove to be a possible confounding factor to this test. This analysis is by no means concrete evidence that all sharks prefer cooler waters, rather it is a reflection of this specific dataset. Since this data is obtained from captured sharks, it does not reflect all shark encounters as the appearance of humans and equipment can dissuade marine life from approaching the beach. Perhaps analysing a dataset detailing shark sightings could be more helpful but has its own limitations regarding details.

library(tidyverse)
## ── Attaching packages ─────────────────────────────────────── tidyverse 1.3.1 ──
## ✓ ggplot2 3.3.6     ✓ purrr   0.3.4
## ✓ tibble  3.1.5     ✓ dplyr   1.0.7
## ✓ tidyr   1.1.4     ✓ stringr 1.4.0
## ✓ readr   2.0.2     ✓ forcats 0.5.1
## ── Conflicts ────────────────────────────────────────── tidyverse_conflicts() ──
## x dplyr::filter() masks stats::filter()
## x dplyr::lag()    masks stats::lag()
#Read in data
sharkmonth=read.csv("Sharks_month.csv", header = T)
dataq1<-sharkmonth %>%
  #Add season classification colmn to dataset
  mutate(Season = ifelse(Month %in% c("December","January","February"), "Summer", "Not Summer"))
Summer <-dataq1 %>%
  filter(Season == "Summer")
NotSummer <- dataq1 %>%
  filter(Season != "Summer")
#Create barplot by grouping summer and not summer
data <- dataq1 %>%
  group_by(Season) %>%
summarise(Shark_Encounter = Sharks) %>%
  arrange(desc(Shark_Encounter))
## `summarise()` has grouped output by 'Season'. You can override using the `.groups` argument.
ggplot(dataq1,aes(x=Season, y= Sharks))+geom_col()

t.test(Summer$Sharks,NotSummer$Sharks, alternative = "greater")
## 
##  Welch Two Sample t-test
## 
## data:  Summer$Sharks and NotSummer$Sharks
## t = 0.71285, df = 2.1738, p-value = 0.2723
## alternative hypothesis: true difference in means is greater than 0
## 95 percent confidence interval:
##  -23.05105       Inf
## sample estimates:
## mean of x mean of y 
##  50.33333  42.33333


Summer

2.3 Research Question 2: Do Bull Whaler sharks prefer warmer water than Scalloped Hammerhead sharks?

## read in data
dataq2=read.csv("BullVSHammerSharks.csv", header = T)
#create boxplot
ggplot(data = dataq2, aes(x = Species.Name, y = Water.Temp..C.)) +
       stat_boxplot(geom = "errorbar", 
                    width = 0.2) +
       geom_boxplot(fill = "#4271AE", colour = "#1F3552", 
                    alpha = 0.9, outlier.colour = "red") +
       scale_y_continuous(name = "Temperature") +  
       scale_x_discrete(name = "Shark Species") +      
      
       theme(axis.line = element_line(colour = "black", 
                                      size = 0.35))

This question aims to compare two species of sharks: the Bull Whaler shark and the Scalloped Hammerhead. The latter is harmless to humans whilst the former poses a threat to swimmers and surfers at the beach. The box plot above shows a general trend where bull sharks prefer warmer water, and this is supported by research that indicates that bull sharks are more likely to attack during summer (Callinan, 2016). The median line in the two plots appear to be indicating similar values, with bull sharks pulling ahead by very little. But the IQR indicates a clearer trend where more scalloped hammerheads are sighted in cooler temperatures than bull whalers. The analysis has the same limitations as the last question, wherein the method of data collection can affect the shark captures as they would be less likely to approach near crowds and equipment. Nevertheless, this dataset still reflects a clear trend that is backed by research.


3 References

Ball, J. (2022, August 12). Do Sharks Like Cold Water? [It Depends On The Species]. WildlifeBoss.com. https://wildlifeboss.com/do-sharks-like-cold-water/

Callinan, R. (2016, April 1). Bull sharks on the bite in hot water, new research suggests. The Sydney Morning Herald. https://www.smh.com.au/environment/conservation/bull-sharks-on-the-bite-in-hot-water-new-research-suggests-20160401-gnvs0i.html