The species matures at an early age, estimated as early as 3 months. Dolphin are known to be sexually mature as small as 14 inches in fork length, with all fish reaching sexually maturity by the time they are 22 inches in fork length. The presence of very young dolphin almost year-round in the Florida Current, coupled with almost continuous spawning observed in some captive fish, may indicate these fish spawn continuously throughout their life. A Florida study calculated that a female 39 inches in fork length produces roughly 555,000 eggs per spawn.
With such rapid growth, it is only natural that dolphin possess a voracious appetite and are aggressive predators. They are opportunistic feeders, eating whatever is abundant at the time, even each other. Off North Carolina squid, crabs, small jacks and small triggerfish, which are the most abundant members of the Sargasso weed community, comprise the bulk of their diet.
However, off Barbados, flying fish and its cousin the flying gurnard are more prevalent in the area and make up the bulk of dolphin’s diets, with squid and small triggerfish playing a smaller role. Dolphin held in captivity have consumed over 20 percent of their body weight in food per day
Any animal that lives life in this “fast lane” is bound to have a down side. Dolphin serves as an important forage species for many of the ocean’s apex predators such as marlins and sharks. Research indicates that the annual production of juvenile dolphin suffers a total annual mortality level of 98 to 99.7 percent. This would translate into only 0.3 to 2.0 percent of all juvenile fish produced in a given year to survive a full 12 months. Aging studies conducted on fish harvested in North Carolina, South Florida and Barbados in the Southern Caribbean found that fish less than 1 year of age made up 80, 74 and 100 percent respectively of all fish landed by fishermen. These are very high percentages considering that these are very biased fisheries, generally selecting older, larger fish. Two year-old fish are exceptionally old for the species and have been shown to make up less than 3 percent of the catch. The oldest individual reported was only four years old. For comparison, this is the age at which red drum just begin to mature sexually.
The species is considered highly migratory and is known to travel as far as 800 miles in ten days. Recoveries of fish tagged off the South Carolina coast shows that when leaving, they move north to North Carolina venturing even as far north as Long Island, NY. Currently, science theorizes that the stock of fish found off the U.S. east coast is shared with the Bahamas, Northern Caribbean Islands and possibly even Bermuda. The Atlantic stock may even intermix with dolphin from the Gulf of Mexico. This is largely speculation since no scientific data has been collected to confirm this theory. An attempt to use molecular genetics to identify the various stocks of dolphin present in the Western North Atlantic failed to show any differences among fish from the Southern Caribbean, Gulf of Mexico, Bahamas or U.S. east coast.
The Marine Resources Division of the Department of Natural Resources initiated a three-year study in 2001 to address questions about the geographic range of the U.S. east coast dolphin stock. The research will utilize uniquely numbered streamer tags to mark individual fish in order to track their movements, migrations and distribution patterns. The study is divided into two phases, one where department biologists will tag fish and the other will utilize volunteer anglers from New York to Key West to the Bahamas to tag dolphin along the full length of their east coast range.
Through the recapture of these fish, science will begin to map movements of individual fish. Because fish can be individualistic in behavior, it will require the recapture of many fish to establish patterns of distribution or migrations. Tag recovery rates for highly migratory oceanic fish is commonly only 1 to 2 percent. The recapture of tagged dolphin is complicated by their extremely high annual mortality, highly migratory nature and overall short life expectancy. This means that each tag recovery is extremely valuable and very important to the success of the program.
Dolphin Length – Weight Table
Weights observed for size classes of dolphin when sexes are combined.N=552
Weight shown in pounds and size classes in inches fork length.
(Hammond, D. L. 1998. SC Recreational dolphin fishery. SC Dept. Nat. Res. Special Rpt. 14p.)