Reproduction and Early Life History of Common Snook, Centropomus Undecimalis (Bloch), in Florida
This paper combines published literature and unpublished Florida Department of Environmental Protection (FDEP) data on snook reproduction and early life history. Published literature originally dealt with fisheries investigations (1950s) and freshwater culture (1970s) but has expanded to include marine stock enhancement, spawning, and larval and juvenile ecology. In addition, ongoing FDEP projects provide considerable information. Snook are protandric hermaphrodites that probably spawn near river mouths, passes (inlets), and points of land in central and southern Florida estuaries. Females are older and larger than males at 50% maturity (5 yrs and 500–522 mm SL versus about 2 yrs and 330–348 mm SL) and have group synchronous ovarian development. The spawning season is long (approx. April to December or January) and includes multiple spawnings. Most spawning occurs between May and September. Spring spawning occurs at water temperatures >22°C and salinities >27‰. Several researchers noted increased spawning activity around the times of spring and summer new or full moons. In pre-spawning behavior, females are escorted by a number of (usually) smaller males, but actual spawning has not been documented. In the laboratory, eggs averaged 0.70 mm diameter and hatched in 17–18 h at temperatures of 26–29°C and salinities of 28–38‰. Newly hatched larvae (1.4–1.5 mm notochord length) spend ∼2.5 wks in nearshore waters before their arrival at shallow-water nursery sites. Eggs have been collected during field studies in only one secondary embayment of lower Tampa Bay, but preflexion larvae have been taken in lower Tampa Bay and just off the beach at Naples. Postflexion larvae have been reported from both coasts of Florida, but only 16 larvae are listed in published literature. Late-stage larvae recruit to vegetated shorelines of quiet, shallow-water creeks, canals, and lagoons in both low-salinity (riverine) and high-salinity (mangrove swamp and salt marsh) environments. Early juvenile-stage snook occupy a spatially restricted microhabitat along shores having limited water movement, moderate shoreline slopes, and vegetation extending over and/or into the water; as the juveniles grow, their habitat becomes less defined and restricted. Early juveniles (<40 mm SL) feed on copepods and other microcrustaceans, but later juveniles (40–50 mm SL) switch to small fish (mainly poeciliids and cyprinodontids) and crustaceans (mainly palaemonid shrimp). Factors other than fishing regulations that affect survival of adult snook include human impacts on habitat quantity and quality and natural perturbations such as cold kills and red tides. Some of these same factors may also affect the survival of larval and juvenile snook.
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Document Type: Research Article
Publication date: 1998-03-01
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