Satellite Tags to Identify Habitat Utilized by Dolphinfish.
The use of archival pop-off satellite tags is most commonly associated with research on large apex predators such as sharks, swordfish, tunas and marlins. These environment monitoring instruments capture time-specific data on water depth and temperature along with daylight intensity which
is used to calculate geo-location. These hi-tech devices have never been used to study dolphinfish. This report provides the first information on temperature selection and water column usage by a free-swimming dolphinfish. Data from
this short-term track suggests that dolphin utilize more of
the vertical water column than previously suspected.
This 15-page report presents findings from the four year dolphin tagging study conducted by the Marine Resources Division of the South Carolina Department of Natural Resources. From 2002 through 2005 more than 700 recreational anglers fishing from over 290 different vessels tagged and released 4,900 dolphin from Key West, Florida, to Nantucket, Massachusetts, in the Bahamas and Gulf of Mexico. A total of 115 tag recoveries were reported during the study including several international recoveries. It examines both the tagging of dolphin as well as their recorded movements looking at evolving behavior patterns. This report presents the first in-depth look at how and when dolphinfish move along the east coast and raises questions regarding relationships to dolphin stocks found in other areas of the
Expressive Colors is a short article examining the use of body color patterns by dolphinfish. Other animals use body hair or feathers to enhance their body language. Lacking these features, dolphinfish use body color patterns instead. This article looks at patterns used defensively as well as those reflecting an emotional state. Many anglers will see color patterns which they have never seen on living fish. This article is intended to make anglers more alert to the amazing colors that this magnificent gamefish possesses.
World-renowned artist Dr. Guy Harvey, a fisheries scientist himself, recognizes the importance of gathering information on the movements and migration of dolphinfish in the western North Atlantic and is personally active in supporting the Dolphinfish Research Program.
The Dolphinfish Research Program is a scientific research project by the fishermen for the fishermen. Virtually all of the field work is carried out by recreational anglers. These concerned citizen conservationists spend their own time and money to catch dolphin, tag them and complete the necessary paperwork. It is also the private angler who is taking the time and making the effort to report the recovery of a tagged fish. Without either of these important contributors the program would not succeed.
The dolphinfish offers many challenges to the study of its movement since they likely travel several thousand miles in a year including the entire western North Atlantic, Caribbean Sea and Gulf of Mexico and only 2 or 3 out of every 100 tagged are likely to be recovered. To conduct a research project on the movements of these fish requires fish to be tagged throughout their full range in the North Atlantic Ocean. Such a project using paid biologists and incurring the expense of the vessels needed to conduct the work, would be cost prohibitive. Subsequently, this project’s success rests with the individual fishermen who support this research.
During the twelve years of the study more than 1,100 boats from Texas to Florida to Massachusetts, the Bahamas and several Caribbean Islands have taken an active role in the research program. As of the end of 2013, more than 2,200 anglers from 40 states and ten foreign countries have participated providing more than 16,000 dolphinfish for tagging and the recovery of more than 450 tags. This page is dedicated to recognizing the commitment and hard work put forth by so many captains and anglers who tag dolphin each year.
Note: This page will be updated at the first of each year to reflect the previous year’s tagging activity. Some names may be incomplete, misspelled or omitted due to illegible handwriting or incomplete information on the tag report cards.
Report: Use of Pop-off Satellite Archival Tags to Monitor
Cobia Utilizing Port Royal Sound, South Carolina
and Dolphinfish Present off the East Coast of the U. S.
Abstract: Cobia, Rachycentron canadum, and dolphinfish, Corypheana hippurus, are important species in the marine recreational fisheries of South Carolina as well as the South Atlantic Bight and Gulf of Mexico. Little information is available on the movements, associated water temperatures encountered and water depths occupied by these two species. The Microwave Telemetry’s model PTT-100 pop-off satellite archival tag (PSAT) was used to monitor temperature, pressure and, on certain instruments, geo-position information. These were attached to 5 dolphinfish off the U.S. East Coast and western Caribbean Sea and 4 cobia in or adjacent to Port Royal Sound, SC. Data were received from 4 instruments placed on dolphinfish and 3 attached to cobia. Dolphinfish were monitored for periods up to 23 days while cobia were monitored for as long as 92 days. Data received from the instruments showed that cobia used waters as deep as 70m and rose to the surface more frequently during May/June than July/August. Cobia were observed to utilize water temperatures from 20.7 to 29.33C but spent the majority of their time in waters from 22.0 to 26.99C. Dolphinfish were shown to utilize ocean waters with temperatures ranging from 16.0 to 30.5C. The highest temperatures were recorded by fish off south Florida while those off South Carolina entered the coldest waters. Dolphinfish off south Florida spent most their time in surface waters of 27.2 to 28.9C while fish off South Carolina spent most of their time in surface waters of 26.3 to 27.2C. Data showed that dolphinfish spend the majority of their time in the top 10 m of the water column but regularly made dives below 30 m going as deep as 124 m. Deep diving behavior was shown to be most prevalent at night.
Report: Is the U.S. Fishery for Dolphinfish Changing?
The Dolphin Tagging Study has listened to fishermen express concerns over the health of the U.S. dolphin stock since it first began working with private anglers in 2002. The question was raised in the mid-1990s by the South Atlantic Fisheries Management Council that resulted in the council’s convening a workshop in1998 on dolphin and wahoo. This workshop ultimately resulted in the Dolphin and Wahoo Management Plan that is currently in place. The outcome of council’s review of all available information was that existing data were inconclusive as to whether the dolphin stock was healthy, but there was no indication that the stock was in decline.
Unfortunately, little has changed in the way of management data available on dolphinfish since the workshop. Data on recreational harvest, number of and size of fish landed, and amount of fishing effort, so crucial to a stock assessment, are still collected by the same National Marine Fisheries Service’s program that was found severely deficient during the 1998 workshop. The Marine Recreational Fisheries Statistical Survey (MRFSS) remains the only monitoring program that captures catch and effort data on the U.S. recreational dolphin fishery in the South Atlantic Bight and Gulf of Mexico.
The following article takes a look at this data base to see if any trends have evolved in the fishery in recent times. Information was examined as far back as 1990 to provide a long-term, 18-year, look at the fishery. The resulting trends were fairly uniform between the fisheries of the U.S. Atlantic and Gulf coasts. But because of the questionable accuracy of this information, the downward trends shown can not be considered real but should be considered a wake-up call that a good quality program is needed now to monitor this important U.S. recreational fishery.
(Information in this article was presented to the South Atlantic Fisheries Management Council at its September 2008 meeting in Charleston, South Carolina)
Presented at the 5th World Recreational Fishing Conference,
November 11, 2008, Dania Beach, Florida USA.
The downloadable file (2.62 MB) is a copy of the presentation, including graphics, made by Don Hammond to the international conference of 300 fishery researchers, managers and anglers from 22 nations. The talk presented a summary on the findings of the first six years of research, 2002 through 2007, in the Dolphin Tagging Study. It demonstrates how volunteer anglers can be utilized as field staff to collect specimens, tag them and record the necessary data. The presentation shows how anglers tagging in widely separated locations can reveal variations in the fish’s behavior. Data generated by private anglers documents the south to north spring and summer movements of dolphin a long the U.S. Atlantic seaboard. Information collected by the program challenges the multi-stock concept currently held by fishery managers for dolphinfish in the Western North Atlantic Ocean.