The life cycle of common snook
Common snook, Centropomus undecimalis is one of five snook species found in Florida and the only one we see here in southwest Florida.
Where they live
Snook occur from South Carolina to Brazil, including Florida to Texas along the Gulf of Mexico. They can live in most any habitat, provided they have moderate to good water quality and water temperatures that generally stay above 60 degrees Fahrenheit. Snook are euryhaline, meaning they can move freely between fresh and salt water. But that doesn’t mean they count as freshwater fish. If you are targeting them, you need a saltwater fishing license.
Snook are protandrous hermaphrodites, meaning males may change to females as they age. This transition takes place when snook are between one and seven years, or 12-35 inches in total length. The transition happens quickly and is identified by both male and female sex cells present in the gonads. In transitioning snook, female gonads mature directly from male gonads shortly after spawning. As such, it’s possible for snook to spawn once as a male and then again as a female within the same season.
Snook spawning occurs between April and October, with peek spawning during long day light days in June and July. During this time, snook congregate in spawning areas. Salinity is important for spawning snook. Saltwater is dense, making eggs buoyant. The more buoyant the environment, the greater chance of eggs and newly hatched larvae getting carried to suitable habitats.
Once spawning begins, a snook can spawn every other day, releasing 1.5 million eggs each spawn. Snook spawning typically occurs during a new or full moon. Released eggs hatch after about 28 hours. Newly hatched larvae drift towards the closest estuary on incoming tides, where they settle out after finding suitable habitat.
Early life stage
In their early life stages, snook prefer low salinity to freshwater backwater habitats with an adequate supply of planktonic insects, molly’s and mosquito fish to prey on. They require dense, overhanging vegetation or emergent plants to protect them from birds and other predators, and prefer quiet, sheltered areas with little to no flow. At this early stage, snook have physiological adaptations that allow them to tolerate low oxygen waters. Few fish can endure low oxygen conditions, affording young snook refuge from many fish predators.
After about a year, snook must move out to the lower estuary. They are now losing their tolerance for low oxygen conditions and require larger food prey. At around 10-12 inches in size, snook are found in the same habitat as adults. But young snook must be careful. Big snook are cannibalistic. As such, small snook generally choose docks and other structures to hide. At this age, a snook’s diet consists of fish, shrimp, crabs and plant tissue.
Male snook may reach sexual maturity at one year, but typically by two to three years of age. Female maturity is around three to four years. The probability that common snook of a particular size will be female increases with length and age. On the west coast of Florida, at age five, there’s about a 50% mix of males to females. Although most male snook do transition to female, not all will. In Florida, the oldest female recorded was 15 years on the Gulf coast and 18 years on the Atlantic coast. The oldest male was 12 years on the Gulf coast and 15 years on Atlantic coast. Although the oldest snook recorded was 18 years, it’s thought they can live at least 20 years and probably closer to 30 years.
In southwest Florida, seventy percent of an adult snook’s diet consists of fish with pinfish (20%) and minnows (16%) rounding out the top two positions for prey items, followed by shrimp at 13%. Snook eat greater than ten times more pinfish in the summer months than in the winter even though more pinfish are available to them in the winter. This is likely because pinfish recruit to the estuary in the winter and are very small. Studies have shown that snook prefer prey 14% their own body length, so in the winter months, pinfish are much too small to be attractive to an adult snook. Snook feed on shrimp year-round but more so in the winter.
During winter months, snook stomachs contain only about a quarter of what is in them in the summer. This is likely because cold water causes their metabolic rate to slow, resulting in decreased feeding. In fact, snook are extremely cold sensitive and become lethargic and may die when water temperatures dip below 60 degrees for any length of time.
Typically we have two closed seasons for snook, one corresponding to their spawning cycle, and the other to protect them during the winter when water temperatures drop. Anglers may continue to catch and release snook during closed seasons. Right now however, snook are catch-and-release only in all coastal counties from the Pasco/Hernando county line south through Gordon Pass in Collier County through Aug. 31, 2020 (UPDATE: extended through May 31, 2022 for Sarasota Bay through Gordon Pass), as a proactive measure due to impacts of red tide in this area.