One aim of this investigation was to identify the population growth rate of the Killer Whale population and to determine if they are in danger of going extinct. The population models used in this investigation analysed the different stages of the life cycle of the Killer Whale population. These stages included; yearlings, juveniles, mature/reproducing females and non- reproducing populations. Using the Lefkovitch matrix transition and R studio the population dynamics of this population were graphically illustrated, and the population growth rates determined. An initial analysis into the population of Orcinus Orcas, Killer Whale in the coastal regions of British Columbia and Washington state shows that the population has a positive growth rate, and over the next 100 years the population is said to grow exponentially assuming that there is no illegal harvesting of the population. The analysis of the stochastic models considers other factors of density dependency such as the harsh environments which the population may be subjected to throughout the course of the 100 years. Although the population growth rate differs slightly from that of the deterministic model, there is not much difference between the two values, suggesting that although the models are not perfect, they give an accurate representation of the population dynamics of Killer Whales along the coast of British Columbia and Washington state.
The elasticities of the deterministic and stochastic population models indicated that the mature/reproductive stage is the most fundamental element of the Killer Whales life cycle and that any change to the proportion of females surviving this stage would result in an exponential decline in the population growth rate. As part of the analysis, a harvesting scenario of this stage in the lifecycle showed that a 6% change in the proportion of this population surviving would lead to a reduction in the population growth over the next 100 years and may eventually lead to the extinction of the animals. Including a harvesting scenario as part of this investigation as, it allows for the development of sustainable conservation strategies to protect the Killer Whale species to prevent these endangered animals going extinct in the future.
It is assumed that anthropogenic activities have resulted in the consequential threats to the conservation of many endangered animals, including; Killer Whales and Grizzly bears. To mitigate the effects of human activity on various animal populations protected areas have been utilised as appropriate conservation strategies. A paper by Williams assessed the benefit of introducing these protected areas for the Killer Whale populations. They named them marine protected areas (MPA). The results of their investigation found that the Killer Whales displayed a greater preference for the MPA compared to normal waters. For a space to be characterised as a marine protected area, it is fundamental that specific attributes are examined. These include; salinity, sea surface temperature and topography. Many other conservationists have advocated for the construction of specific Killer Whale sanctuaries, aimed at protecting the Killer Whale populations. They have suggested that these sanctuaries could be used to protect the Whales for their entire life, or they could be targeted to Whales who are at specific stages in their lifecycle, for example those at the reproductive stage. Based on the results of this investigation, it may be useful to design an MPA to protect the mature, reproducing female Whales, as this has been shown to have a major impact on the population growth rate.
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There are numerous other strategies which have been aimed at the conservation of Killer Whales. Some of these strategies have included; minimise the noise and disturbances caused by large vessels around habitats where Killer whales have been observed feeding. There is also a conservation strategy which involves restricting mass fishing in certain areas which have been known to act as foraging zones for the Killer Whales. One study investigated genetically distinct Killer whales and how their population dynamics differ depending on their fish consumption. The study suggested that some forms of the Killer Whale are exclusively dependent on a single species of salmon as a food source. The paper investigated the effects of salmon fishing on the population dynamics of the Killer Whale population. They gave evidence to show that in areas where there is a high level of salmon fishing, there is a reduction in the population growth rate of the Killer Whales. This is an interesting concept which indicates that there could be a decline in the population growth rate as an indirect result of negative anthropogenic activity which could potentially be included in the population model of this investigation as part of the future prospects. Weiler identified that a decline in the salmon populations has been one of the main challenges faced by conservationists as it has resulted in a decline in the population of Killer Whales, particularly along the coast of Washington state. They claim that one of the causes for the reduction of the salmon population is due to the construction of dams which have been known to prevent the migration of fish, remove habitats and change the flow of the river. This results in a lack of salmon fish migrating downstream towards to the coastal regions where they would normally act as an abundant food source for the Killer Whales.
Conclusion
This investigation focused on assessing the population growth of Killer Whales in the coastal regions of Columbia and Washington state. It was found that the population growth of the animals is expected to increase in the next 100 years assuming that there are no major changes to their environmental conditions. This was confirmed through the construction of deterministic and density- dependent stochastic models. This study also wanted to determine which stage of the Killer Whales life cycle had the biggest impact on the population growth. Using Lefkovitch matrix transitions, sensitivity values and elasticity values, it was found that the mature, reproducing female stage had the biggest impact on the population growth of the population. Next, a harvesting scenario was introduced to determine what percentage of the mature, reproducing female stage could be harvested without having an impact on the population growth rate. From this, it was found that a 6% decrease in the proportion of mature, reproducing females surviving would lead to a decrease in the growth of the population in the next 100 years and would eventually lead to the extinction of the killer Whales in that region. This information is important as it allows for conservationists to develop strategies to protect this species and prevent them from going extinct in the future.
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