Cruise ships navigating vast ocean expanses often encounter sharks, leading to observations of sharks appearing to follow them. This phenomenon sparks curiosity, as the presence of sharks near these large ships is not coincidental. Several factors contribute to this interaction, ranging from direct attractants generated by the ships themselves to the natural behaviors of sharks within their marine environment.
Attraction to Discarded Food and Waste
Cruise ships, carrying thousands of passengers and crew, produce substantial amounts of organic waste, particularly food scraps from galleys and dining areas. While strict regulations govern waste disposal at sea, some organic matter can still enter the water, either inadvertently or through permitted discharges of finely macerated food waste outside of protected areas. This discarded food creates a highly concentrated scent plume that disperses through the ocean currents.
Sharks possess an exceptionally developed sense of smell, which allows them to detect minute concentrations of chemicals, including amino acids released from decaying organic matter, from considerable distances. This keen sensory ability enables them to trace the scent of food waste back to its source, drawing them directly to the ship’s vicinity. This readily available food source can attract smaller marine species, which in turn attracts opportunistic predators like sharks.
Artificial Ecosystems Around Ships
Beyond direct food waste, cruise ships inadvertently foster temporary artificial ecosystems that draw marine life, attracting sharks. The large size and structure of a ship can act as a mobile aggregation point, offering shelter in the open ocean. This can attract various fish species, which then gather around the hull.
Furthermore, the bright lights emanating from cruise ships, particularly at night, play a role in this attraction. These lights penetrate the water, drawing in plankton and small baitfish, which are themselves a primary food source for larger fish. As these smaller marine creatures congregate near the illuminated areas, they create a concentrated feeding ground that larger predatory fish and sharks find appealing. This indirect food chain effect contributes to the presence of sharks around vessels.
Natural Behaviors and Opportunistic Encounters
The presence of sharks near cruise ships also relates to their natural, opportunistic behaviors. Sharks are widely distributed throughout the world’s oceans, inhabiting diverse environments from coastal waters to the open sea. Cruise ships traverse vast ocean territories that are already part of sharks’ natural migratory paths and feeding grounds.
Sharks are highly opportunistic predators, constantly investigating for food or unusual activity. An approaching ship, with its unique sounds and disturbances, can pique a shark’s curiosity, prompting it to investigate. Thus, a sighting may mean the ship passed through a shark’s territory, prompting investigation of a novel stimulus or food opportunity.