Over the years, there has been a steady decline in the great white shark population. New data, gathered and published in the PLOS ONE online journal, suggest that the population is now increasing.
Ocean swimmers may not be thrilled to hear this news, but for the overall ecosystem, it is positive for the health of the oceans. While the study could not actually count the number of great whites, it captured trends in shark abundance in the northwest Atlantic.
Great white sharks were hunted aggressively in the 1970s and 80s for their fins and jaws, used in foods and medicines. Many were caught in nets meant for the sea animals the great whites hunt. This reduced the population by approximately 70% from 1961. In the 1990s, conservation efforts began and 1997 was the year that federal law banned hunting great whites. In 2009, the population was 31% lower than the benchmark year of 1961.
Another PLOS ONE study indicated that great white shark abundance is probably growing in the Pacific Ocean as well. This is in direct opposition with the results of a 2011 Stanford University study. Obviously, researchers need more time and more accurate ways of tracking and studying the great white population.
One of the new ways that is being tried is labeled “Citizen Science” in which data collected by scuba divers and snorkelers. By taking photos to accurately identify species, divers can assist scientists with data on populations. It seems that the information is surprisingly accurate. A system called acoustic telemetry, used to track tagged sharks, has confirmed and supported the numbers reported by citizen science. Abundance estimates derived from the divers’ reports and the data from acoustic telemetry are remarkably close. No doubt, this practice will continue to assist researchers as they monitor the status of the great white shark.
In Australia, scientists tested the accuracy of aerial observation in the monitoring of shark population. In general, this was found to be less accurate than other measures. Air patrols in helicopters tended to undercount the number of sharks in any given area, mostly due to the difficulty in actually seeing the sharks from that vantage point. While they may be of use when there is some noted activity in an area by checking if there are a high number of sharks – enough to compromise the safety of beachgoers, this method is otherwise ineffective.
One question related to all of this is: How long do great white sharks live? This certainly affects numbers. Recent data suggests that females live to approximately age 40 and males to age 73. One must wonder if other studies took this data into account when discussing population. What is the female to male ratio? Is the population being affected by the number of female sharks and reproduction opportunities?
Regardless of how they are being counted and subsequently studied, great whites appear to be benefitting from the conservation measures and laws in place for their protection. Hopefully the positive trend will continue and great whites will once again be able to fully represent their part in the bigger ecological system in our oceans.
