The Tarpon Weight Calculator allows anglers to get an estimate of the weight of their fish based on length and girth without removing the fish from the water. Leaving tarpon larger than 40” long in the water is important to making sure the tarpon survives after being released. To estimate a tarpon’s weight, find the dorsal girth on the vertical axis and the fork length on the horizontal axis.
Or consult the graph:
Source: Ault, J. S., & Luo, J. (2013). A reliable game fish weight estimation model for Atlantic tarpon (Megalops atlanticus). Fisheries Research, 139, 110–117.
To estimate a tarpon’s age, find the fork length on the vertical axis of the chart below and scan right until that line crosses the blue (male) or orange (female) lines. Then scan down to the horizontal axis to find the estimated age. For example, the dashed line shows that a tarpon with a 58” fork length is approximately 22 years old if it is a male (blue dashed line) and 15 years old if it is a female (orange dashed line). These represent the average age for each length due to differences in individual growth rates. Unfortunately, there is no way to tell if a tarpon is a male or female by appearance, so make your best guess. This data is based on tarpon in Florida; growth rates may vary in other regions.
Data from: Crabtree, R.E., E.C. Cyr, J. M. Dean 1995. Age and growth of tarpon, Megalops atlanticus, from South Florida waters. Fishery Bulletin 93:619-628.
