The bull shark, Carcharhinus leucas, is a highly robust and adaptable species. Public interest in this large predator in temperate coastal regions, such as the New Jersey shore, is high due to its reputation. The bull shark possesses unique biological characteristics that make its presence in these waters noteworthy. This article addresses whether bull sharks are found in New Jersey and explores the environmental factors that facilitate their occasional arrival.
Confirmed Presence in New Jersey Waters
Bull sharks have been scientifically documented in New Jersey waters, confirming their occasional presence, though they are not year-round residents. Their appearance is tied to the seasonal migration of warm water masses moving northward up the Atlantic coastline. The summer months, typically from June through September, mark the period when ocean temperatures are suitable for these tropical and subtropical sharks to extend their range into the Mid-Atlantic region.
Historical records provide the most compelling evidence of their presence, most notably linking them to the Matawan Creek attacks in 1916. The attacks that occurred several miles up a freshwater creek are widely accepted to have been caused by a bull shark, given its tolerance for low salinity environments. More recently, fishermen and local authorities have reported sightings, particularly in the estuarine systems and bays, during periods of prolonged warmth.
The increasing health of local fish populations, which serve as a food source, combined with rising average water temperatures, may contribute to a more frequent northward expansion of their range. While confirmed sightings remain relatively uncommon compared to species like the sandbar or sand tiger shark, their documentation establishes them as a genuine, albeit rare, visitor to the New Jersey coastal ecosystem.
Estuaries and Salinity Tolerance
Bull sharks can venture into New Jersey’s bays and rivers due to their biological adaptation known as euryhalinity. This trait allows them to thrive in both saltwater and freshwater, distinguishing them from most other large shark species. They regulate their internal salt and urea balance using specialized organs, including the kidney, liver, and rectal gland.
When moving into freshwater, their body adjusts to prevent the influx of water and loss of salts. Their renal system, particularly the kidney, conserves salts and excretes excess water. This physiological flexibility allows them to penetrate far up waterways like the Delaware Bay and the Navesink River, areas inaccessible to most other large sharks.
Warm water is the primary trigger for this northward movement, as bull sharks prefer temperatures exceeding 70°F (21°C). Estuaries and shallow coastal bays warm up faster than the open ocean, becoming attractive habitats for feeding and possibly as nursery areas. Juvenile bull sharks often use low-salinity estuaries as protected environments to avoid predators and find plentiful food.
Distinguishing Bull Sharks from Common Local Species
Identifying a bull shark from other large sharks found off the New Jersey coast requires attention to specific physical characteristics. Bull sharks possess a short, blunt snout that is wider than it is long, giving their head a rounded or “bull-like” appearance. Their bodies are stocky and robust.
In contrast, the sandbar shark (Carcharhinus plumbeus) has a taller, triangular first dorsal fin that originates near the pectoral fin insertion. The sand tiger shark (Carcharias taurus) is identifiable by its needle-like teeth that protrude from its mouth, and its first dorsal fin is set farther back on the body, closer to the pelvic fins.
Another distinguishing feature is the absence of an interdorsal ridge—a line of raised skin between the two dorsal fins—which is present on species like the sandbar and dusky sharks. The combination of the bull shark’s blunt snout and stocky profile serves as the clearest visual cue for identification. Most bull sharks observed in this region average around 7 to 8 feet in length when mature, though they can grow larger.
Safety Measures for Coastal Visitors
While the presence of bull sharks in New Jersey is confirmed, the risk of an encounter remains low, and informed awareness is the most effective safety measure. Coastal visitors can minimize interactions by avoiding swimming when sharks are most active: at dawn, dusk, and at night.
Swimmers should stay out of murky water, often found near river mouths or after heavy rain, as low visibility can increase the chance of a shark confusing a human with its natural prey. Avoid areas where large schools of fish are visible, or where there are signs of fishing activity, such as discarded bait or fish scraps. These conditions signal food sources that could attract sharks.
Staying close to shore and swimming in groups provides a layer of protection, making individuals less vulnerable. Always adhere to the instructions and warnings provided by lifeguards and local authorities, as they monitor for sightings and are trained to assess potential hazards. Understanding that the ocean is the natural habitat of many species, including sharks, allows for respectful enjoyment of the coast while minimizing risk.