Great White Shark Populations Have Been Declining and Migrating; Predatory Orcas Could Be a Reason Why

While South Africa is known to host some of the world's largest great white shark populations, there have been significant declines in shark numbers in areas where these creatures typically gather.

Declining Great White Shark Populations

Back in 2011, skilled shark spotters were able to record more than 300 sightings of great white sharks in eight different beaches. However, since 2019, there have been no documented sightings. These declining numbers have raised concerns regarding great white shark conservation, as these creatures play a pivotal role when it comes to marine ecosystems.

Being top predators, great white sharks aid with the balancing and health of aquatic food webs and affect the entire stability and structure of the ecosystem.

Specialists needed to examine whether this decline was due to actual population changes or due to migration. To delve deeper, researchers conducted a study that looked into abundance trends over time and distribution shifts across the range of South Africa.

Findings revealed vital variations in terms of abundance in main areas where great white sharks gather. In some locations, declines were observed, while others exhibited stability or increases. Generally, the trend appears to be stable, which suggests that the numbers of great white sharks have stayed consistent since they started being under protection.

While this is reassuring, there are challenges that surface alongside the unforeseen distribution of these creatures. Hence, it is vital to monitor shark locations better.

Biggest changes were seen from 2015 to 2020. Understanding the underlying patterns behind the changes is still a challenge. Nevertheless, environmental conditions, including season, lunar phase, food availability, and water temperature, all affect their movement. Climate change and prolonged ocean changes also play a role. Their nature to migrate enables these great white sharks to look for ideal conditions when their environments are seen to be unfavorable.

Predatory Orcas

The complexity of great white shark distribution gets even deeper when killer whale orcas enter the picture. These apex predators have been seen to prey over sevengill, bronze whaler, and white sharks.

Though there has been no established causative link, tracking data and observations reveal that white sharks have a flight response that follows incidents of predation. It was also made clear recently that when an orca pod killed three or more white sharks, the remaining sharks were forced to migrate out of the area.

Better Shark Monitoring

As patterns of shark movement lean towards the east, it is vital to consider the potential risk changes.

Moreover, given how shark presence could affect activities of humans, it may be necessary to adjust management strategies as these shark distributions change over time. This may involve adding more signages, implementing temporary closures, or boosting education.

There is a need to conduct further research in order to know more about what affects shark movement and distribution. The recent study stresses the importance of having standardized methods for data collection in order to be able to generate reliable statistics that cover their full range.

The researchers also propose the establishment of long-term tracking programs throughout the Eastern cape and that focus on reducing shark death count.

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