South Carolina Sea Grant Consortium

Cooperative Fisheries Research Grant Progress Report

Title:   Use of Archival pop-off satellite tags to study cobia in Port Royal Sound , SC and dolphinfish present off the East Coast.

 

Report Period:  July 1, 2006 to January 1, 2007

 

Principle Investigator: David Harter, Hilton Head Reef Foundation

Associate Investigator: Donald L. Hammond, Cooperative Science Services, LLC

 

Project Award:$30,400

 

Progress:

1. Deploy four pop-off archival satellite tags in cobia captured in or adjacent to Port Royal Sound. 

                Only a small number of large-mature cobia entered Port Royal Sound in 2006.  Subsequently only one fish was obtained for tagging.  A satellite tag programmed to record for 90 day before releasing was placed on a 44 inch FL cobia on June 7^th.  The tag has not been heard from since its deployment.  Unfortunately, this is not unusual.  Dr. Jim Franks with Southern Mississippi University who is the only other researcher to use satellite tags on cobia has had two tags that did not report. 

2. Deploy six similar tags in dolphinfish captured in the South Atlantic Bight.

                Three instruments were deployed on dolphin in 2006.  Two were deployed in the Florida Straits one off Islamorada and the other off the Western side of Bimini Island , Bahamas .  The third tag was deployed off South Carolina .  Attempts were made to release two tags off Cape Hatteras , North Carolina , but due to absence of large fish, none were deployed.

3. Develop a water temperature selection profile for each species utilizing time-at-temperature as recorded by the archival tags. 

                Over 12, 000 time-date specific observations on temperature and depth were received from the three tags deployed on dolphinfish. These data showed that fish off south Florida used warmer and a more narrow range of temperatures than dolphin off South Carolina .  Preliminary analysis of the data also indicated that dolphin will enter much colder waters than previously thought, down to 16.1^oC. 

4. Analyze vertical movements in the water column for behavioral patterns using time-at-depth as recorded by the archival tags.

                Time-at-depth data from the instruments placed on dolphinfish is revealing a new behavior never before noted or even suspected for the species. Data shows dolphin to use more of the water column the previously suspected making dives as deep as 125 meters.  It also indicates that dolphin spend more time below 30 meters during the night than in the day.

5. Attempt to identify near-shore waters utilized by cobia using depth and temperature records.

                No progress was made toward fulfilling this objective due to lack of data.

6. Attempt to document long distance movements using the satellite tag geo-positioning system.

                This tracking function is limited to the three 90-day tags designated for cobia.  No data was received from the one 90-day instrument that was deployed. A limited tracking of the dolphin movements is being attempted by back calculations using drift speeds.

 

Challenges Encountered: The biggest problems encountered have been the standard issues facing the study of living, animals in the wild, weather and availability of individuals.  Weather, conflicts in scheduling and the absence of proper size fish, hampered the study in 2006. It has been difficult to secure recreational fishermen who are willing to give up their large cobia and dolphin even for cash incentives. Efforts will be made to attempt deployment earlier in the year. If the two remaining 90-day instruments were deployed on 1 April 2007, data from these instruments would not be received by the project until August. Subsequently, it will be necessary to seek an extension for this project. The date when the instruments are deployed will largely determine the length of the extension period needed.

Budget Status:     No Draws were made on the Sea Grant award.  Reimbursement for expenditures will begin in 2007.