Life History

Growth of Dolphin through Tagging Data

Sept 2022 By Wessley Merten 

Fisheries scientists often talk about when a fish may ‘enter’ a fishery or be at a size that is large enough to be caught by a certain size of tackle. For dolphin, based on a combination of our tagging data and photos shared with us through the years, while rare, we estimate this can occur as early as 6″ fork-length (FL). We have had two fish tagged at that size, four at 7″, five at 8″, and seventeen at 9″ FL. It is not until 14″ FL, however, that we observe over 500 records or ~1% of our tag release data. Based on this, it appears rare for anglers to catch fish less than 14″ FL, and if those catches occur it is likely situational when anglers are using smaller gear such as small live bait hooks, a sabiki rig, or small lures. Here, we use the large increase in tagging records at 14″ to denote the size when dolphin enter the region’s recreational fishery.

Perrichon et al. (2019) documented the developmental dynamics of dolphinfish and noted at ~13 cm FL, or ~5″ FL, dolphin begin the juvenile phase 55 days post-hatch.  This puts a fish of that size just shy of two months old.  Preliminary results from a comprehensive analysis of growth observed through our tagging data estimate dolphin can grow up to 1″ per week.  Therefore, we estimate that a 6″ FL juvenile dolphin is two months old and a 14″ FL fish at a late 3- or early 4-month old fish.  

With those statistics set, we can now begin to better understand the age of tackle testing bulls and cows that we all dream of catching.  With a grow rate of up to 1″ per week, or 4″ per month, a 3-4 month old fish will be pushing 42″ to 46″ FL at 11 to 12 months of age based on the growth rate obtained through our tagging data.  Using dolphinfish length/weight records collected by the Puerto Rico Department of Natural and Environmental Resources, 42″-46″ dolphin weigh between 20-25 pounds.  This size is the typical gaffer fish that we encounter when conducting tagging work around Puerto Rico and the Virgin Islands.  This is also likely the size where dolphin start to slow their growth in terms of length and, instead, start to pack on the pounds.  See Captain Bouncer’s Smith tag story from years ago (click here).

When fish reach the size like Bouncer’s incredible recovered fish, or Captain Carlos ‘Chispa’ Torres brute (pictured below) caught north of San Juan, Puerto Rico, on September 24th, 2022, based on the reported weight of 49-pounds gutted and our growth model, we estimated that this fish is 635 days or 1.6 years old.  That age is just shy of the age of Bouncer’s 60-pound fish which we estimated at 707 days.  It is important to note that last month’s newsletter included a report about a fish that was at large for 374 days and released at 16″ fork-length.  After refining our growth model we overestimated the weight of that fish by 8 pounds.

Big Bulls of 2020

By Wessley Merten October 2020

Catches of massive bull dolphin are exciting to report because, most often, they represent a state or tournament record, boat record, or angler record (click here for a table we maintain).  For most that fish offshore, acquiring a coveted record, such as largest dolphinfish, is nothing short of spectacular and only a few will have the opportunity to ink their name somewhere in a record book.  For scientific purposes, it is important to document landings of large individuals to examine seasonal, interannual, and decadal trends by location.  As part of our annual tradition, we are excited to share our list of the top five largest bullswe observed through social media in the Western Central Atlantic Ocean in 2020.  Weight is reported in pounds below.  Note that La Calankita’s fish is whole weight gutted, which points to the importance of gathering weight measurements of massive fish before they are processed.  Backlash’s fish established a new tournament record at the White Marlin Open and is the third 72+lb fish to be landed in Poor Man’s Canyon off Maryland in the past two fishing seasons.  Who knows, maybe in 2021, we will receive word that the long-standing world record, which still stands at 87 pounds, will be surpassed.  After all, that is only 12.5 more pounds than Wagner’s fish! Given that, last year, two anglers within 3 weeks of each other caught similar sized bulls in the same canyon, we might be documenting a new trend within the Mid-Atlantic Bight (MAB).  Further down the coast, Florida state waters produced at least one 70+lb fish in 2020 and several others in the 50+lb, range including the Slay family’s 58.90 lb fish caught off Cudjoe Key in the Lower Keys.  The latter represents one of the larger fish observed in the Keys over the last several years.

Moving over to the U.S. Caribbean Sea, Captain Colt Cook and angler Alex Zimmerman enjoyed catching a 63.7 lb beast just a few miles north of St. Croix in the Anegada Passage.  Less than two weeks before Hook N’ Cook caught its big bull, Captain Emmanuel Markham had a stellar day south of La Parguera, Puerto Rico, in late January and caught another massive fish that weighed 53 lbs after it was gutted.  In 2020, take note that the largest observed fish within the U.S. Caribbean Sea occurred during late January and early February, and only five months later, the largest fish occurred along the U.S. East Coast between June and August.  Last year, the top two largest fish were caught in the MAB between late July and mid-August, which is consistent with this year’s timing.  However, in early March of 2019, angler Dylan Louis caught a ~72 lb fish off Port Everglades, which was and remained as the largest for the year off Florida.  In 2019, we observed out of season catches of big bulls at FADs off the north coast of the USVIs and south coast of the Dominican Republic.  Congratulations to each of the vessels and anglers for catching these massive bulls in 2020.

Big Bulls of 2019

By Wessley Merten October 2019

The Mid-Atlantic Bight (MAB) makes up a massive part of the U.S. East Coast and, for offshore fishing, it consists of numerous offshore canyons that vary in size, distribution, and location from Norfolk Canyon in the south to Hydrographer Canyon (and others beyond) in the northeast.  This year, two record breaking dolphin were caught in Poor Man’s Canyon off Maryland, which set new state records for the Old Line State.  On August 16, 2019, Kristi Frashure of Pasadena caught a 74.5-pound bull while participating in the Poor Girls Fishing Tournament in Ocean City, MD.  She was fishing aboard Haulin N’ Ballin.  This brute was caught just 3 weeks after Jeff Wright of Cambridge, MA, caught a 72.8 pound fish to break a 34-year long standing record set by Kim Lawson in 1985.  Her fish weighed 67.5 pounds.  Even though Mr. Wright’s record only stood for 3 weeks, both occurrences raise a host of questions about the presence of these large fish in the same canyon in roughly the same time.  For example, were these fish traveling together? While bulls are known to be very aggressive in captivity if held simultaneously, can very large bulls like this co-occur in a large school of females?  The DRP has observed multiple males in schools while scuba diving but not 70-pound fish.  Even if they were not traveling or migrating together per se, did they originate in a similar location and make it to the MAB following a similar water body or influx of bait?  This occurrence, while possibly random in nature, seems too much of a coincidence to not think of other movement dynamics occurring.

When we consider other large bulls caught in the Atlantic in 2019, other patterns also emerge.  For example, angler Dylan Louis caught a ~72 pound fish on March 14^th, 2019, off Port Everglades and was the only massive bull reported in Florida in 2019.  In addition, this might have been the only 70+ pound fish caught in Florida in the past few years,  which signals a series of questions regarding the size occurrence of dolphin in the Florida Straits over the past several years.  Where are all of Florida’s big fish?  The state record for Florida still stands at 81 pounds for a fish caught in 2007 by R. Vail.  Another interesting pattern to note are the large dolphin (numbers #4 and #5) caught at FADs in the Caribbean Sea.  Angler Chris Berry and angler Oscar Paredes caught huge bulls this past summer off St. Thomas, and south of Casa de Campo this past summer.  Lastly, Captain Kenny Midgett operator of Marlin Gull Sport Fishing Charters sent us some great reports this past season including a very nice bull caught on the North Carolina-Virginia border in 1000 fathoms in early May.  The end of April and early May is a time for U.S. East Coast return migrants and this nice bull, and report from Captain Midgett, provides supporting evidence to patterns we have observed through years of tagging data.  Click here to read an article on U.S. East Coast return migrants.

The Mythical Century-Mark Behemoth Dolphin

By Jennifer Betz and Wessley Merten

Biggest dolphin caught during the 2018 Big Rock Tournament – June 14, 2018 Photo courtesy of Brian Peele

Documenting the most rare of individuals of any fish with IGFA does entail a thorough process, but we are grateful that this process exists to allow anglers the opportunity to advance society’s knowledge on the uniqueness of the rarest individuals in any given species.  We just still can’t believe that 87 pounds is still the all-tackle world record for mahi!  But, with large 72- to 76- pound fish caught off the U.S. East Coast just last year (and last month), maybe it could happen this year. So, get your scales ready.  Examples of some acceptable weighing devices and scales which must be certified by authorized officials are shown to the right.  Part II of this article examines current state- and country- based dolphin records around the country and region (see table below) and we use recapture data to examine when it is likely state records could be challenged, and that is spring.  The table below will be updated periodically and expanded to contain more records for large dolphin in other key locations such as the Bahamas and Dominican Republic.   Click here to read a short article about U.S. East Coast return migrants and showcases the dedicated anglers and captains who tagged and released small dolphin and took precious time to report recoveries of large fish returning to the coast in spring.

Click here to check out all the line class, tippet, and junior world records for dolphinfish certified by IGFA.