Dr. Guy Harvey's Fish Recovered off Key Largo

August 2020

When COVID-19 boating restrictions were lifted in the Cayman Islands at the end of June, we can only imagine how quickly Dr. Guy Harvey and his daughter, Jessica Harvey, set up an outing to get offshore.  As luck would have it, one of the two dolphin they tagged north of Grand Cayman during one of their first offshore trips of the summer, on July 1st, would go on to provide direct evidence of the time it takes a dolphin to swim from Grand Cayman to Key Largo, FL; 38 days.  Guy and Jess measured the fish to be 24″ in fork length, and Captain Lazaro Rangel measured 28″ in fork length when he and his family recaptured the fish aboard Lady C on birds off Key Largo, FL. A total growth of 4″ equates 

to a daily rate of .105″/day, which is slightly faster than the program’s overall average of .084″/day. The movement, when compared to surface drifter tracks (left) over the last three years from June to August, is consistent with the speed of the only observed drifter traversing the area in 2020.  While we do not have a track of exactly where this fish swam, given the predominate west-northwest tendency for surface drifters and overall flow of surface currents, this recapture event highlights another U.S. Atlantic coast dolphin supply route via the western Caribbean Sea and Loop Current.  The other supply routes were identified in a paper we published in 2016 about the seasonal re-entry of dolphinfish along the U.S. East Coast from the northeastern Caribbean Sea. Click here to access that paper.  This new recovery adds to our work on better describing the

Captain Lazaro Rangel measured 28" in fork length when he and his family recaptured Guy's fish aboard Lady C on birds off Key Largo, FL.
Figure 1 X46344 Straight-line movement to Key Largo, FL, as well as surface drifter ID 4101630 movement from 6.1.2020 to 8.17.2020.
Figure 2 June (yellow), July (red), and August (blue) surface drifter movements during 2018, 2019, and 2020..

movements of dolphinfish across the broader Caribbean Sea and adds to the remarkable results we acquired only a year ago when, for the first time, a bull was observed to swim across the Caribbean Basin to the southwestern portion of the Caribbean Sea known as the Columbia Basin. The tag released from the fish approximately 75 miles east-southeast from Isla Providencia and 106 miles east northeast of the San Andres Islands in the southwestern Caribbean Sea. This intriguing movement raises a multitude of questions regarding the movements of dolphin in the Caribbean Sea.  Our research in this area began eight years ago with the first PSAT deployment on a dolphin off the southwest coast of Puerto Rico.  That bull was tagged on April 2nd, 2011, and went on to carry the tag for the full 30-day monitoring interval. Then, two years later, we deployed two more PSATs in the same area.  One of those fish returned another full 30-day monitoring period but we

 did not hear back from the other.  Recently, and for the first time in this 19-year study, one of our PSATs was recovered off the south coast of the Dominican Republic after a 56 day monitoring period.  Thankfully, our volunteer Fishing and Research Ambassador, Chris Whitley, along with colleague Rick Alvarez, worked together to successfully return the tag to the DRP HQ and we retrieved the entire movement log from the 47″ bull. While we need many more movements to better understand the seasonal movements of dolphinfish throughout the Caribbean Basin collectively these movements establish a baseline (below).    The primary objective of this work is to describe both broad and fine-scale horizontal and vertical movements of dolphin tagged and released in the Lesser and Greater Antilles within the Caribbean Sea (i.e., it excludes fish tagged in the tropical Atlantic north of the British Virgin Islands, United States Virgin Islands, Puerto Rico, Hispaniola, Cuba and the Bahamas).  This is the first study of this nature to be undertaken in this region and will help us to better understand how this species moves between jurisdictions within the Caribbean Sea, what movement routes pathways, and corridors dolphin may use and on what time frame, and how fish that move through the eastern Caribbean Sea are connected to other regions including the southwestern, western, and northwestern Caribbean Sea. 

Figure 3 Preliminary movements of dolphin based on conventional (yellow arrows) and satellite tag (red arrows) data in the Caribbean Sea since 2009. The numbers indicate days at large. Stars without numbers indicate additonal recapture sites for fish tagged along the U.S. East Coast.
Figure 4 The comparison of X34351 popup location to an extensive surface drifter analysis conducted by Richardson (2005). The black stars in the three diagrams represent the approximate popup location of tag X34351 in the northern part of the Columbia-Panama Gyre. Click to enlarge.

Captain Teke’s Fish Recovered Off Barbuda

March 2020

Last year, Captain Ron Teke and his fishing team, Colorado Magic, requested a sleeve of 50 tags.  Part of their motivation to receive this many tags was that they were determined to become 2019’s top tagging private boat and beat the reigning champions, the Killin’ Time II fishing team, who fish offshore just down the road in the Lower Keys.  Although they fell short of winning the coveted dolphin tagging award, little did they know that their drive to win and consequential uptick in tagging activity would result not only in a milestone recovery for the program but their second and most significant recovery since they began tagging for the Dolphinfish Research Program (DRP) in 2004.  In addition, Captain Teke’s fish, reported by Captain Vickram Dindyal while fishing a FAD northeast of Barbuda on March 4th, 2020, represents the third recovery in the Tropical Atlantic in the last 15 months for the DRP.  Similar to the other recoveries, Captain Teke’s fish grew 30″ in 265 days, which equates to a weekly growth rate of .79″.  These observations show the movement of dolphin biomass from the U.S. East Coast to the Tropical Atlantic/Northeastern Caribbean Sea in 9 to 11 months.  All three recoveries were dolphin that ranged between 16″ and 24″ fork length, were released during summertime off the Keys, grew to tackle testing adult fish, and were recaptured during winter in the Tropical Atlantic.  Collectively, this is the 7th international recovery in the Tropical Atlantic for the DRP.  When this event is compared to a geolocation track obtained from a 42” bull in 2014, it suggests this fish traveled much more than the distance of that track (8,059.10 miles).  We approximate that if this fish followed a path similar to that of the 2014 bull, and one assumes this fish followed the Gulf Stream north from its release site to offshore South Carolina (574 miles), this dolphin traveled at least 8,633 miles in 265 days. 

Figure 1 – Dolphin dispersals from Florida and South Carolina to the Tropical Atlantic and Caribbean Sea.  The bold black arrow is the most recent international recovery depicted as a straight-line between mark and recapture sites.  Numbers indicate days at liberty.  The colors of the geolocation track obtained in 2014 indicate the month.  BAR = Barbuda; TA= Tropical Atlantic; CS=Caribbean Sea.

This would, however, put the daily movement rate of this fish at 32.5 miles per day, which is substantially slower than the 2014 bull (44.7 miles/day).  In a scientific paper published in 2014, the combination of both conventional mark and recapture data with surface drifter tracks provided realistic movement route comparisons given dolphin fidelity with drifting objects as well as their shallow diving nature (click here to see that paper and additional web article below).  In that paper, one fish recaptured in the north-central Atlantic (443 miles southwest of the Azores Islands) provided evidence of dolphin along the U.S. East Coast moving at least 2,400 miles into the Atlantic.  When this observation is combined with surface drifter tracks and seven recoveries (Cuba, Hispaniola, Mona Passage, Puerto Rico, USVIs, Anguilla, and Barbuda) in the Tropical Atlantic, all observations point to fall/winter migration from the U.S. East Coast to the Tropical Atlantic with increasing days at liberty for recovered fish as you move east along the Greater Antilles from the Cuba event (see figures; 159 DAL) to the recent northern Leeward Islands event recently off Barbuda (265 DAL).  In the future, additional geolocation tracks from dolphin tagged and released off Florida, South Carolina, or Rhode Island can provide routes dolphin take that can be compared to the patterns observed in conventional recoveries as well as surface drifter tracks.  Congratulations to Captain Ron Teke and the Colorado Magic fishing team as well as Captain Vickram Dindyal for logging yet another fascinating recovery for the DRP. 

Figure 2 – Examples of dolphin dispersals from Florida to the Tropical Atlantic in December (Dec) 2018 and March (Mar) 2019.  The bold black arrows are the most recent international recoveries depicted as a straight-line between mark and recapture sites.  Numbers indicate days at liberty.  The colors of the geolocation track obtained in 2014 indicate the month.  TA= Tropical Atlantic; CS=Caribbean Sea.

Another Dolphin Goes the Distance (Again!)

March 2019

Another Dolphin Goes the Distance (Again!) Last month we reported on a major recovery that occurred north of Arecibo, Puerto Rico, in December.  You can read a detailed article about that recovery by clicking here.  This month we are excited to report that Danielle and Daryl Gustafson of Big Pine Key, FL, added another major recovery for the DRP, but this time it was north of St. Thomas, USVI.  The fish was recaptured by Eric Estrada during a charter run by Captain Colin Butler, owner of Fish Whistle Sport Fishing Charters.  This is the first international recapture from Florida to the north coast of the USVIs for the DRP and the second recovery in the northern portion of the U.S. Caribbean in the past three months for the DRP.  Is this a pattern?  Two recoveries do not point to a pattern but the recoveries are intriguing for a couple of reasons.  First, the most obvious observation is that both fish were tagged off the Florida Keys in nearly the same location (only 20 miles between release locations) and recaptured north of the continental shelf break that separates the USVIs and Puerto Rico from the Caribbean Sea.  Secondly, these recoveries are the first for the DRP since the program began in 2002 that moved from the Keys to this area.  In the case of the most recent recovery, the fish was at liberty for 210 days and grew 14″ or at least .46″ per week before being recovered.  While the time at large is similar to the December recovery (a difference of 12 days), the growth rate of the fish involved in the most recent recovery is substantially slower.  In the case of the December recovery, the fish weighed 27 pounds when recovered.  Looking at thousands of length-at-weight records, a dolphin that weighs 27 pounds is estimated to range between 44” to 47” depending on the gender (which was unknown in the December recovery).  Therefore, we estimate the growth of the fish recovered in December to range between .70” to .98” per week, or 35% to 54% faster than the most recent recovery.  The biggest caveat with this comparison is the fact that the December growth rate was estimated based off measurements that were estimated.  However, even when we compare the growth rate of the fish involved in the most recent recovery to only those recaptures that have occurred throughout the history of the program where sizes were measured upon release and recapture, the growth rate is still substantially slower for this fish.  Could this have been a pompono dolphin which are known to be smaller than their common dolphin cousins?  The Gustafsons did not note that this was a pompono upon release (and they tagged 9 other individuals on that particular day), and when recaptured, Captain Colin Butler did not notice anything peculiar about the fish but did note that it was a male (it was noted a male upon release, too).  Male pompono also develop a blunt forehead but it is not as pronounced as the common dolphin.  Because of this observation, we lean more toward this recovery being a common dolphin, but because a photograph was not taken of the fish before it was re-released with the tag, we are not 100% certain.  Take home message: please take photos of fish that are recaptured

February 2019

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