there is no chance of escape. The onslaught methodically continues until the last sardine has been consumed.
The Sails
Sailfish range through the tropical and sub-tropical waters of the world’s oceans. Highly prized as a game fish, the sailfish is the subject of an immensely valuable, worldwide recreational fishery. Sailfish are considered to be one of the fastest fishes in the ocean. Their speed, agility, tendency to jump, and readiness to feed, make sailfish one the most sought after and commonly captured sport fish. While commercial fleets rarely target sailfish, pelagic longliners and purse seiners encounter them as incidental catch while fishing for tuna and swordfish, and they are captured in artisanal fisheries along many coastlines.
Due to their value to sport fishermen, sailfish have been the subject of one of the most expansive tagging efforts of any pelagic species to date. Since the 1950’s, over 90,000 sailfish in the Atlantic have been conventionally tagged with a plastic streamer through the efforts of various billfish and regulatory organizations, such as The Billfish Foundation. The vast majority of these tagging efforts have occurred in the western north Atlantic, with a center along the east coast of Florida. Around 1,900 tags had been recaptured with a recapture rate of 2%, with the longest time period between a release and a recapture ranging from 8–11 years. While this recapture rate remains low, it is the highest among the billfishes, and tag shedding, non-reporting, and international language barriers may all contribute to the low numbers of returns. Most recaptures were relatively close to their release sites, leading managers and researchers to believe sailfish have a much patchier, coastal distribution. Previous attempts to retain satellite tags on sailfish were relatively short-lived (i.e., less than 5 months) and provided results similar to those depicted by conventional tagging.
Simply put, most people think sailfish don’t move around much, if at all!
But us being inquisitive scientists, we decide to look into the matter ourselves. Isla Mujeres and the Yucatan Peninsula of Mexico are a major fishing hub and hotspot for sailfish. Dr. Molly recalled how it all came about:
The reason we went to Isla Mujeres to tag sailfish was because of our long partnership tagging giant bluefin tuna with Captain Anthony Mendillo. He invited my husband and I down to “swim with the sails” because he thought it was a sight we needed to see! We went one Christmas holiday, and knew immediately that we had to find out more about these fish- where did they come from, where did they go. Since we had great success at tracking big fish like giant bluefin tuna, and Capt. Anthony is among the best known captains for handling bluefin and sailfish, he put us together with Guy Harvey to discuss starting a satellite tagging project for sailfish. Everyone was enthusiastic, so LPRC’s Emily Chandler and I went back the next springtime to get tags on sails. Over the course of three years of sail tagging, we’ve had many “guest captains and crew” helping us with the work- including Anthony’s daughters, Lily and Andrea, ocean videographer George Schellenger, a K-12 science teacher supported by Guy Harvey Ocean Foundation, and a number of fishermen “rock stars”, including captains and mates from our other projects. And of course we are backed by the analytical prowess of LPRC’s oceanographic and tag data analysis team, Dr. Tim Lam and Ben Galuardi.
In the field
Under the deteriorating funding climate, most scientists consider themselves lucky if they get to carry out a study for a single field season or year. We are firm believers in the need to study a migratory, long lived fish species over many years to truly understand what they do, so we decided to aim for the long term, and grew our project over time. At the end, we achieved a 3-year project, deploying 34 popup satellite tags. This was possible because we pooled resources from the Large Pelagics Research Center and Guy Harvey Ocean Foundation, and were lucky to have Berry Inc. donated vessel time, and Sir Richard Branson & Virgin United generously sponsored six PSATs. Sir Branson had his own close encounter with sailfish while chartering Captain Anthony Mendillo, and was beautifully captured by Shawn Heinrichs.
After all, each popup satellite tag (which is more like a pressure- and water-proof iPhone for marine animals) costs us $4000 USD each! And that doesn’t include the time and effort our team put in to do the field work and analyze the data once the tags “pop off”. Successful PSAT tagging for big fish is nearly always the result of carefully orchestrated hard work by a diverse team of experienced fishermen and taggers, with a tight budget!
To tag, the crew has to catch and hook a sailfish via rod and reel, and then carefully leaders it onto a thick wet padded mat. We cover its eyes to minimize stress and irrigate its gills with a stream of seawater through the mouth. With seawater oxygenating the gills, sailfish recuperate quickly and their colors return right away. We then carefully anchor the tag’s dart in the best spot on its flank. It has to be just right so as not to disturb the fish’s fins or impact its swimming behavior. For future genetics work, we also collect and store a very tiny fin clip sample and remove the circle hook from the fish’s gape. All of these actions are well orchestrated and usually completed within 90 seconds or less. We have one last look at the sailfish’s condition before the crew lifts it carefully over the gunnel and sends it off into the blue!
The big surprise
We were able to keep multiple tags attached on sailfish for up to a full year! As if that wasn’t exciting enough, our sailfish proved wrong traditional ideas about where these fish go. The majority of conventionally tagged sailfish were recaptured in the same regions they had been originally tagged in. Our tagged fish have shown us what they are capable of — going just about everywhere in the Northwest Atlantic if they choose to.
Here is one example: We tagged this first sailfish off the Yucatan, where it hung out for a short while. It then traveled to the center of the Gulf of Mexico before heading west past Cuba and eventually ended up off the Florida and Georgia coasts. It then trekked back to the Yucatan exactly one year later. Our PSAT tag popped off 18 miles (29 kilometers) from where this sailfish was originally tagged! This sailfish definitely knew where it was going- as if it has its own GPS and Google Maps. Yes! Without a smartphone.
But that’s not all we learned. Sailfish feed around the Yucatan in the late winter and spring and then go off on yearlong migration or “road trips” to various productive coastal regions in the West Atlantic, including to a region off the Northeast coast of Brazil. One sailfish journeyed to Brazil, some 2962 miles (4768 kilometers) away, and eventually returned to the Isla Mujeres region and was again, within 180 miles (300 kilometers) from where it had been tagged the year before.
You have got to see this migration to believe it!
When we have such a detailed collection of movement data from multiple individuals, we are able to assemble a bigger picture of where sailfish would be in space and time. Without diving too deeply into the details, here are the highlights of our study:
To learn more
There is a lot more than what we can cover in this introductory article, so if you are interested in learning more about our work, it’s best to go read our published paper. It’s in the public domain and free for everyone, so please distribute and spread the word on our new and exciting findings. You will find all the fancy figures and supplementary materials here:
http://www.nature.com/articles/srep38163
For more information please visit: https://medium.com/@Tuna/riding-with-sailfish-to-northwest-atlantic-ocean-hotspots-d4b3947f6051#.pydbwrgto
Photo Captions:
Sailfish1: Lilly Mendillo of Keen M International checking on a recently tagged sailfish. Credit: George Schellenger
Sailfish2: Isla Mujeres
Sailfish3: FV Keen M
Sailfish4: It’s a team effort, y’all! Credit: Charles Blaney/Large Pelagics Research Center
Sailfish5: Credit: Charles Blaney/Large Pelagics Research Center
Sailfish6: Credit: Anthony Mendillo/Large Pelagics Research Center
Sailfish7: Credit: Anthony Mendillo/Large Pelagics Research Center
Sailfish8: Hard at work in the field. From the top: Dr Molly fought to bring in a sailfish. Once you have reeled it in, you have to move fast to do the tagging and sampling. That includes cutting a very tiny piece of the fin for genetic analysis and taking measurement on the sailfish’s length. After all that is done, the whole team is always very pumped up and excited that we have accomplished another successful release. As you can see we’re a diverse team: women scientists and a multi-national crew. Credit: Anthony Mendillo/Large Pelagics Research Center
January 2017 - Stories from the Sea
94 - SEVENSEAS