Sharks May Be Much Closer To Cities Than You Think, New Research Finds

Researchers expected the sharks to avoid areas close to the city because of the chemical, light, and noise pollution emanating from the coastal metropolis. However, this is not what they found.

Humans are rapidly settling near the world's coastlines, but this increased urbanisation is impacting species living in the ocean. However, the impact of the increased human species on marine species is not fully understood. A team of researchers led by scientists at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science recently tracked the movements of three shark species, bull, nurse and great hammerhead, in relation to the city of Miami. 

The researchers expected the sharks to avoid areas close to the city because of the chemical, light, and noise pollution emanating from the coastal metropolis. However, this is not what the scientists found.

The study titled "Urban Sharks: Residency patterns of marine top predators in relation to a coastal metropolis " was published June 16 in the journal Marine Ecology Progress Series.

Urban Exploiters, Urban Adapters & Urban Avoiders

Animals can be divided into three groups on the basis of their relationship with urban areas. Animals such as pigeons and raccoons, which thrive in the cities, often become dependent on human garbage for food, and are known as "urban exploiters". Other animals which may show some use of urbanised areas, but still largely rely on natural areas, are known as "urban adapters". There are some species such as land predators which are very sensitive to human disturbance, and avoid big cities. These animals are known as "urban avoiders". Wolves are "urban avoiders".

In a statement released by University of Miami, Neil Hammerschlag, the lead author on the paper, said few studies have investigated the movements of ocean predators in relation to urbanisation, but since other studies have shown that land predators are urban avoiders, the team expected sharks to be too. 

Sharks Spend A Lot Of Time Near Cities

He added that the researchers were surprised to find that the sharks they tracked spent so much time near the lights and sounds of the busy city, often close to shore, no matter the time of day. 

The team conducted that the behaviours of the tracked sharks resembled that of "urban adapters". According to the study, sharks could be attracted to shore from land-based activities, such as discarding of fish carcasses.

The tracked sharks were observed to use the urban-impacted areas a lot, and this may have consequences for both sharks and humans.

Hammerschlag said by spending so much time close to the shore, sharks are at risk of exposure to toxic pollutants as well as fishing. This could impact their health and survival. 

Shark bites on humans are rare. However, the study stated that areas close to shore could be avoided by human water users to reduce probability of a negative shark encounter. This would promote human-shark coexistence.