Bonefish Reproduction

Fish have some of the most diverse ways of reproducing in the animal kingdom.  From males creating nests and caring for eggs, to females bearing live young, to both sexes broadcasting gametes into the water column so that fertilized eggs can drift for days in the ocean’s currents, fish have evolved a wide range of reproductive strategies to maximize the likelihood that their offspring will survive, disperse, grow, and eventually reproduce as well.  Since the ‘success’ of a fish’s life is tied to its ability to contribute young to the next generation, understanding the detailed reproductive ecology of each fish species is critical to developing conservation strategies that help sustain their populations – populations that play important ecological roles in aquatic ecosystems as well as support valuable commercial and recreational fisheries around the world.

Bonefish (Albula spp) represent one of the most sought after group of marine recreational fishes inhabiting subtropical and tropical flats.  Despite contributing greatly to the enjoyment of many anglers as well as to the economy of many regions, it might come as a big surprise that we still know very little about the life history of bonefish, especially their reproductive ecology.  Anglers and guides who spend a great deal of time on the water are able to make important observations about the seasonal movement patterns of bonefish, and some have even provided anecdotal information about where, when, and how bonefish reproduce.  Several scientific studies tend to confirm some of these observations, yet most of the evidence is still quite circumstantial regarding the reproductive activity of bonefish.  For instance, we have a fairly good idea about what time of year bonefish spawn, but we still do not know exactly where spawning occurs or how bonefish behave during spawning bouts.  One small confounding factor in understanding the reproductive ecology of bonefish is that there are now over 10 known species worldwide, and each may have its own particular timing and mode of spawning. 

In 2004, a group of scientists from Carleton University, the University of Illinois, and the University of Wisconsin converged at the Cape Eleuthera Institute and formed the Flats Ecology and Conservation Program (FECP) – a research initiative that has been using bonefish as a model species to study the integration and complexity of shallow marine ecosystems.  Fortunately, unlike other regions in the Atlantic, all bonefish that have been sampled for genetic analyses thus far have been identified as a single species, Albula vulpes, meaning that it is possible to complete a relatively accurate picture of this species’ life history and ecology.  Not long after the FECP formed, we began using remote telemetry to measure the movement patterns of bonefish inhabiting the shallow tidal creeks and flats of Eleuthera.  Remote telemetry uses an array of receivers affixed to the sea floor that ‘listen’ for fish implanted with transmitters.  Each time the receivers are downloaded we are impressed by the hundreds of thousands of detections, or ‘hits’, generated by tagged bonefish swimming within range of our receivers.  These hits allow us to put together maps indicating movements, schooling patterns, and site preferences of bonefish in the detection area. 

Data from our tagged bonefish clearly show seasonal differences in their movement patterns.  From May through late November bonefish spend nearly all of their time moving between shallow tidal creeks and flats, likely because of the high food abundance and ability to avoid predators in these ‘skinny’ waters.  In December, however, bonefish broaden their movement patterns to include deeper water near the end of a peninsula of land that is adjacent to deep water.  Snorkeling in these deeper waters revealed bonefish in extremely large schools (we can’t tell you how much fun it is so swim with 500 bonefish, but that is a story for another day!) and fish caught from these schools showed signs of spawning readiness.  To our surprise, bonefish held in tanks at the Cape Eleuthera Institute also showed signs of reproductive activity at exactly the same time – to our knowledge this is the first time bonefish have attempted to spawn in a controlled environment.  Interestingly, both of these observations were soon followed by ‘hits’ on remote receivers positioned up to 3 km offshore.  Bonefish were also detected at the end of the peninsula and on offshore receivers in 90 ft of water in March and April right on the edge of an undersea canyon that drops to over 1000 feet deep.  The proportion of tagged bonefish using these areas ultimately exceeded 75% of all tagged fish indicating that March and April may be peak spawning times for bonefish.  Also of interest is the fact that these movements coincided with both the full and new moons.  Full and new moons are periods within the lunar cycle when the tides and tidal currents are the greatest, and it is potentially advantageous for bonefish to spawn during these times as a way to maximize the dispersal of their fertilized eggs. 

Given that we tagged a relatively small proportion of the population and that bonefish reside in large schools, we estimate that there must have been thousands of bonefish using deep offshore waters during the spawning season.  Following their visit to offshore waters, our tagged bonefish abruptly returned inshore and resumed their more recognizable behavior of moving in and among shallow tidal creeks and flats.  Thanks to the continued support of the Bonefish & Tarpon Trust, along with other supporting organizations, such as Patagonia, we will continue to examine the where, when, and especially how bonefish spawn in the waters off Eleuthera through 2009.  Collectively this information will help identify other potential spawning sites throughout the Bahamian Archipelago as well as the rest of the Caribbean.

For more information contact Dr. Andy Danylchuk ( This e-mail address is being protected from spambots. You need JavaScript enabled to view it )