Sharks inhabit oceans globally, from frigid polar regions to warm tropical seas. Their ability to thrive in varied environments raises questions about their relationship with water temperature. The notion of whether sharks prefer cold or hot water is not simple, as their thermal preferences are as varied as the species themselves.
Diverse Thermal Preferences
Shark species exhibit a wide spectrum of thermal preferences. Some are adapted to colder environments, like the Greenland shark, which prefers water temperatures between -1.1 and 7.4 °C and can be found at depths up to 1,200 meters. This Arctic inhabitant is known to migrate seasonally based on depth and temperature, moving to shallower waters in winter and deeper, or further south, in summer. The salmon shark in the northern Pacific and the porbeagle shark in the Atlantic are also adapted to cold waters.
Conversely, many shark species are specialized for warm, tropical waters. The great hammerhead prefers tropical and warm temperate waters, typically between 20-30°C. Other warm-water species include the bull shark (20-28°C), the oceanic whitetip shark (20-28°C), and blacktip reef sharks (21-30°C) found around coral reefs.
Some sharks, like the great white, demonstrate broader temperature tolerance. They inhabit coastal and offshore waters globally in temperate and subtropical regions, often migrating to follow their preferred range of 10 to 26.5°C. This adaptability allows them to exploit diverse hunting grounds. Juvenile great white sharks, however, prefer a narrower band, typically 14 to 24°C, in shallow coastal nursery areas.
Physiological Adaptations to Temperature
Most sharks are ectothermic, meaning their body temperature largely mirrors that of their surrounding water. This characteristic influences their metabolic rates; in colder waters, their internal body processes slow down, while warmer waters increase their metabolic activity. However, a unique group of sharks in the Lamnidae family—including the great white, shortfin mako, salmon, and porbeagle sharks—possess regional endothermy.
These sharks can warm specific body parts, such as swimming muscles, brain, and eyes, above ambient water temperature. They achieve this through a specialized network of blood vessels called the rete mirabile, or “wonderful net.” This countercurrent heat exchange system transfers heat from warmer venous blood to cooler arterial blood. For example, a great white can maintain its stomach temperature up to 14°C warmer than the surrounding water, enabling faster digestion and powerful muscle contractions. Salmon sharks can maintain internal temperatures up to 11°C above ambient, remaining active predators in cold northern Pacific waters. This internal warming provides a performance advantage, enabling higher activity levels, faster swimming, and quicker reactions, particularly beneficial when hunting in cooler environments.
Influence on Behavior and Distribution
Water temperature is a primary driver of shark behavior and geographic distribution. Seasonal temperature changes often trigger extensive migrations. Great white sharks, for example, follow their preferred temperate water range, moving from areas like Maine in summer southward as waters cool. Tiger sharks also exhibit temperature-driven migrations; as ocean temperatures warm, their annual migrations extend further poleward and their arrival times in northern areas occur earlier. This shift can impact their foraging opportunities and exposure to fishing pressures.
Temperature also dictates habitat selection. Tropical species, like the blacktip reef shark, prefer shallow, warm waters around coral reefs. The bull shark, known for its versatility, favors warm coastal regions and can even venture into freshwater systems within the tropics. Conversely, cold-water species like the Greenland shark are found in deep, cold habitats, though they may move to shallower waters in winter.
Reproduction in sharks is closely linked to water temperature. Many species select specific breeding and pupping grounds based on suitable thermal conditions. Sandbar sharks, for instance, migrate to breeding grounds off the East Coast of Florida in spring. Rising ocean temperatures can impact reproductive success, potentially leading to smaller, less energetic pups. Warmer conditions can accelerate embryonic development, causing embryos to use yolk sacs faster and hatch earlier, which may leave them undernourished.
Temperature affects foraging and hunting behaviors by influencing prey distribution and shark activity levels. Sharks often follow their prey, which also respond to temperature fluctuations. Endothermic species like the great white and mako sharks use their enhanced metabolic rate and muscle efficiency to hunt effectively in cooler waters where prey is abundant. For ectothermic sharks, activity levels are directly tied to ambient water temperature, making them more active in warmer conditions.