Approximately 100 million sharks are killed for their fins each year. | Photo: South China Morning Post
I found myself in awe as a team of artists and conservationists made efforts to raise awareness for two endangered species. As a response to Sea Walls: Painting Ocean-Inspired Murals in Mexico to Save Sharks and Rays, the efforts to create awareness were inventive and inspiring. One of the main influences of their project was due to shark finning in Asia, where research shows that approximately 100 million sharks are killed for their fins each year. Coincidentally, the same motivation and effort that drove our team was due to the same immoral shark fin trade.
Recently, a few students and I from the University of Delaware worked on a worldwide modeling project that was used to analyze and predict shark populations and their extinction rates. Our main objective in creating this model was to understand the extinction patterns in order to possibly mitigate them. Over the past several decades, recent studies show a dwindling shark population due to many factors including climate change, diminishing food supply, and hunting. The issue of hunting is especially troublesome due to the fact that sharks are often killed from bycatching for other fish. When they are directly targeted, sharks are often killed solely for their fins while the remains are wastefully disposed. Consequently, several species of sharks have made their way onto the endangered species list. If conservation efforts are not put into effect, it is very likely that we may lose a fascinating creature that has been on the earth longer than most. However, it is difficult to determine which conservation efforts would be most effective, because so little is known about sharks and they tend to travel across wide areas. Therefore, we focused our attention on the efforts that could affect hunting patterns of sharks. Through the development of this model we attempted to answer the following questions:
1.When will certain species of sharks become extinct if current hunting and bycatching patterns continue?
2. How effective laws (those that affect the hunting of sharks) need to be to protect sharks and ensure that their population increases as opposed to decreasing to the point of extinction.
In recent years, research regarding sharks has profoundly improved. Still, there is a lack of comparative analysis. First, upon researching, we quickly learned that many assumptions were going to have to be made, which, in turn, limits the precision of our model. As previously mentioned, it is estimated that 100 million sharks are killed each year. This estimation can be broken down into 2 categories – harvesting through hunting and harvesting as a result of bycatching. In layman’s terms, bycatching is harvesting sharks that have been caught in fishing nets and other fishing practices. In order to decrease bycatching rates, research and change of netting and fishing practices needs to be in place. Consequently, we focused on the hunting aspect of trade, rather than the latter.
In order to accomplish this endeavor, we created a generalizable analytic model that can be applied to specific species. Our team used Leslie matrices and their properties to predict population growth. Additionally, in using the general data we were able to find about shark populations and their hunting patterns. We were able to create a model that has the power to predict the time of extinction of a certain species of shark, as well as the ability to predict if shark populations will increase or stabilize when certain laws are put in place. These laws could prevent a certain amount of hunting of sharks for their fins, sport, or otherwise.
Sparing readers the details on the process of formulating our model, we created a dual age class Leslie Age Structured Matrices, juveniles and adults, in which, historically, can predict population growth in ecology. For those interested in modeling and the process, I urge you to read How to Solve it, by George Polya. We applied our model to a specific shark species that we believed had the most data – the great white. We assumed the following. First, the distribution of females and males were even. On average, only 1 female offspring lives to reach maturity, due to the low fecundity rate of white sharks (meaning low survival rate of female offspring). The low fecundity rate is proportional to the survival rate of offspring, as well as the survival rate of juveniles and adults. However, we allowed survival rates to be functions that have the power to change due to hunting increase/decrease and laws being placed into effect over time.
Consequently, we estimated that with unchanging habits and laws, we see great whites becoming extinct in about 370 years. Upon reflection, we believed this number was higher than expected, so we returned to the data of our assumptions. We may not have taken into account the probability that they were all female or all male, or whether or not they will even come in contact to mate. Therefore, extinction could potentially occur much sooner. Our model merely predicts when extinction is definite, or the longest possible time period before extinction occurs.
In short, our model elucidates the longest possible time in which a shark species will last before extinction as opposed to exactly when a shark population will become extinct. Our model also has the power to predict how much of hunting needs to be stopped in order for the shark populations to stabilize or increase.
By growing up in the surfing community, most people have a strong passion and ownership of the ocean. With this sense of respect, we should also find it in our hearts to protect what cannot protect itself. From manta rays to coral reefs, we are obligated and have a duty to help and preserve its essence.
[Part 2 will consist of the final model and respective conclusions]
