Lake Pontchartrain, a vast body of water in southeastern Louisiana, often sparks curiosity regarding the types of aquatic life it harbors. Many wonder if dolphins, creatures typically associated with open oceans, inhabit its waters. Understanding the presence of such animals in Lake Pontchartrain requires examining its distinct ecosystem.
Dolphins in Lake Pontchartrain
While Lake Pontchartrain is not a typical habitat for marine dolphins, bottlenose dolphins (Tursiops truncatus) are occasionally observed within its boundaries. Historical records show their presence was rare before the mid-2000s. However, reports of dolphins in the lake increased after Hurricane Katrina in 2005, with approximately 30 to 40 individuals observed in 2007. These dolphins are usually transient visitors, entering the lake for reasons such as following prey, exploring, or during periods when the lake’s salinity is higher.
Some dolphins observed in the lake have displayed skin lesions, which are thought to result from prolonged exposure to lower salinity water. While an albino bottlenose dolphin, a “pink” dolphin, has been sighted in Louisiana waters, these unique individuals are found in river channels closer to the Gulf of Mexico, not as common residents of Lake Pontchartrain itself.
The Lake’s Unique Waters
Lake Pontchartrain is classified as an estuary, a body of water where freshwater from rivers mixes with saltwater from the sea. Its salinity levels fluctuate considerably, influencing the types of aquatic life that can thrive there. The lake connects to the Gulf of Mexico primarily through the Rigolets strait and Chef Menteur Pass, and also via the Inner Harbor Navigation Canal (IHNC). These connections allow saltwater to enter the lake, particularly in its eastern regions.
Freshwater input comes from several rivers, including the Tangipahoa, Tchefuncte, Tickfaw, Amite, and Bogue Falaya. Additionally, the Bonnet Carré Spillway can divert Mississippi River water into the lake during flood events, further reducing salinity. Salinity can range from nearly freshwater in the western areas to almost half that of seawater in the east, with an average historically around 3.5 parts per thousand (ppt), but sometimes reaching up to 15 ppt.
Other Aquatic Life
In Lake Pontchartrain, some large aquatic animals might be mistaken for dolphins by casual observers. Manatees are frequently sighted in the lake and surrounding waterways, and their size and surface behavior can lead to misidentification. These slow-moving mammals can grow to over 10 feet in length and weigh more than 1,000 pounds. Manatees are adaptable, able to inhabit freshwater, saltwater, or brackish environments, but they prefer warmer waters and migrate when temperatures drop below certain thresholds.
Another large species found in Lake Pontchartrain that could potentially be confused with a dolphin is the alligator gar. This fish is one of the largest freshwater fish in North America and can reach lengths of up to 10 feet. Alligator gar are highly adaptable and can live in various aquatic environments, including brackish water. While their appearance is distinctly different from a dolphin, their size and occasional surfacing might lead to momentary confusion for an uninformed observer.