Article by Capt. Mark Sampson
It’s been a pretty sharky season for us aboard the “Fish Finder”, and as of the last day of August we’ve landed 593 sharks representing 15 different species. If things hold true to course, we’ll probably still be catching them right into the first week of October. It’s been a fun summer, and this year there’s been a lot more interest by the public and different news media about the various shark research projects we’ve been involved with, so I thought I’d take this chance to write a short summary of what kind of extra-curricular activities we’ve been doing besides just trying to help our clients end up with a shark at the end of their line.
Tagging for the Cooperative Shark Tagging Program
Before releasing a shark, we often plant a small tag at the base of its dorsal fin. The tag is a small plastic capsule attached to an even smaller stainless steel dart. The dart is inserted just under the skin of the shark and the very visible capsule trails on the outside. Inside the capsule is a note written in five languages that has the contact information for the Cooperative Shark Tagging Program run by NMFS (a branch of NOAA) in Rhode Island. This program was created in 1961, and since then thousands of fishermen and scientists have been tagging and releasing sharks to help researchers better understand and manage these incredible fish. Over the years, recapture information has given scientists valuable data about shark migrations, travel patterns, fishing pressure, mortality figures, growth rates and much more. This knowledge can be an invaluable tool to scientists and marine managers. So far this year, we’ve tagged 142 sharks with “M” tags.
Satellite SPOT tagging
For the third year in a row, we have been involved in a project to put satellite transmitters or “SPOT tags” on mako sharks. This year we were successful in tagging twelve makos and one common thresher shark. This type of tagging requires sharks to be carefully lifted out of the water long enough to literally “bolt” the transmitter to the dorsal fin of the animal before release, a process that we’ve been able to hone down to a 6-8 minute process. The location of these sharks can then be pinpointed every time their dorsal fin breaks the surface and the transmitter sends out a signal. The thresher was tagged on May 19th while we were fishing for makos and it was determined at that time to go ahead and put one of the expensive, $1,800 transmitters on the shark as an experiment to see if that species was a viable candidate for that type of tagging study since a thresher had never been successfully tagged with a SPOT tag before. While makos had been reporting in almost every day, after two months our thresher had not been heard from and it was feared that perhaps it had not survived the tagging and release. Finally, on July 21st it finally broke the surface and gave us a location off Maine. By late August it had reported three more times and was up in the Bay of Fundy off Nova Scotia.
Anyone who wishes to follow the daily tracks of our makos can find a link to the tracking site on my BigSharks.com website. From the right side of my homepage click on the “Shark Tracking” tab, then click “Go to the tracking site >> here” which will take you to the “Choose a Project Page” where you should select option #3 “W. North Atlantic.” Then select any of the sharks on the right side of the screen to follow. Their sponsor name or number is listed below along with a few details about each shark.
Age and growth study
Most of the sharks we tag are also injected with oxytetracycline (OTC) which is an antibiotic used in veterinary medicine. We inject the sharks with OTC, not for the antibiotic qualities but for the side affect that it stains the shark’s vertebrae. If an injected shark is ever recaptured and biologists are able to examine the vertebrae (under a microscope) they can measure how much it grew from the time we originally stained it. This will provide them with information that might some day allow them to accurately determine the age of a shark simply by measuring the vertebrae. A total of 130 have been injected this season.
DNA study
So far this season, 410 of the sharks we’ve landed have had a small snip of tissue removed from the trailing edge of their dorsal fin that was sent down to Nova Southeast University in Florida where the DNA will be extracted and catalogued. The data from this analysis will assist ongoing projects designed to help researchers better understand the distribution and movements of sharks by examining if, or how similar species of sharks found in different locations around the world are related.
Completion of a hook study for sharks taken in the recreational shark fishery
Since 2012, we have been participating in a project, in cooperation with the Maryland Department of Natural Resources, that was designed to compare the efficiency of both circle-hooks and J-hooks in the recreational shark fishery. The goal of the project was to determine the effectiveness of each style at both hooking and staying hooked, as well as if the hook was most likely to set in the jaw or the gut. Every day, for three seasons, we fished two "study lines" rigged with either circle or J-hooks and details of every bite were recorded. After 204 trips and 781 bites, the study revealed that if a shark takes a bait on a circle hook it is more likely to get hooked than with a J-hook. Once hooked, it is less likely to come off a circle hook than a J-hook and it is more likely to be hooked in the jaw with a circle hook than with a J-hook. In other words, “when it comes to catching sharks, circle hooks are the best choice for fishermen in all categories.” The results of this study has just recently been submitted for publication and will hopefully be available for public review in the months ahead.
White shark sightings
On July 15th, an estimated 13-foot white shark visited our chumline about five-miles offshore and gave us a close enough encounter that we were able to tag it and get an underwater video as it swam behind the boat. (The video can be viewed on our “modernsharking” YouTube channel) On July 28th, the same shark was observed and videoed by white shark researchers off of Chatham, Massachusetts who were able to identify it by the unique scarring on its back, a laceration on its head and the tag we planted in its back. On July 20th we had a quick encounter with another white shark that surfaced 20-yards behind the boat and then left us. We estimated that shark to be 8 to 10 feet long. White sharks are not particularly abundant off Delmarva, but they certainly wander through our waters periodically.
Blocker-Rig research and development
Over the years, we have realized that despite the use of circle hooks, rather than being hooked in the jaw, a shark will still be hooked in the esophagus or stomach 5 to 10% of the time, depending upon the species and the circumstances. In order to minimize this small (but still present) risk of deep hooking, we have spent the last eight years developing terminal tackle that greatly minimizes the risk of a shark being hooked anywhere but in the jaw, thereby increasing the chances of it surviving the process of catch-and-release. Known as a “blocker-rig”, this specialized terminal tackle almost totally eliminates the risk of deep hooking most sharks. This season we designed, tested and adopted improvements in the construction of our blocker-rigs so they would be easier to make and more efficient at catching fish.
With the exception of the “hook study”, the rest of this season, and then again in 2016 should find us again lending assistance with these worthwhile and (at least for us) very interesting shark research projects.
Mark Sampson is an outdoor writer and Captain of the charter boat, “Fish Finder”, docked at the Ocean City Fishing Center.
