This study reports growth parameters and mortality for Sphoeroides testudineus from La Carbonera, a karstic tropical coastal lagoon on the northwestern coast of the Yucatán Peninsula, Mexico. A total of 461 specimens were collected between April 2009 and March 2010. We obtained the length-weight relationship and the growth parameters of von Bertalanffy growth model (VBGM) by length frequency analysis. Additionally, mortality was estimated and analyzed. Exponent b indicated an isometric growth pattern. The growth parameters of VBGM were: L ∞ = 29.50 cm, k= 0.77 year-1 and t 0 =-0.168 years. The instantaneous natural mortality was 1.53 year-1 .

Summary This study reports length–weight relationships and growth parameters for Sphoeorides testudineus from La Carbonera, a karstic tropical coastal lagoon on the northwestern coast of the Yucatan Peninsula, Mexico. A total of 461 specimens were collected between April 2009 and March 2010. The length–weight relationship was W = 0.061Lt2.98. Model parameters of the von Bertalanffy growth equation were: L∞ = 29.50 cm, k = 0.77 year−1 and t0 = −0.168 years.

Summary This study reports length‐weight relationships and growth parameters for Floridichthys polyommus Hubbs, 1936 and Fundulus persimilis Miller, 1955 from La Carbonera, a karstic tropical coastal lagoon on the northwestern coast of the Yucatan Peninsula, Mexico. Specimens were collected between April 2009 and March 2010. The resulting length‐weight relationship for F. polyommus was: W = 0.0180 Lt3.37 and W = 0.0142 Lt3.35 for F. persimilis. This study presents the first estimation for both species of the von Bertalanffy growth model parameters, the growth performance index, the L50, and is the first report of the length‐weight relationship for F. persimilis.