An anesthetized mummichog beside a pit tag, which is about half an inch long. Photo by Sharon Settlage.<\/figcaption><\/figure>\n\n\n\nRudershausen installed antenna units in three locations in Morehead City \u2014 Pelletier, Porters and Spooner creeks \u2014 and an unnamed creek in Beaufort he calls AV Creek. The creeks are found in areas with different “alteration scores” as calculated by the N.C. Coastal Habitat Protection Plan, or CHPP, committee.<\/p>\n\n\n\n
Generally, high alteration scores are associated with more development. Jen Weaver, a former Sea Grant\/N.C. Division of Marine Fisheries fellow, worked with DMF and Buckel to recommend alteration scores. (See Summer 2012 Coastwatch for a story on CHPP.)<\/p>\n\n\n\n
Rudershausen, Buckel and Hightower are testing whether the health of the primary fish species living in the tidal creeks is related to the alteration scores, and thus to coastal development.<\/p>\n\n\n\n
Gloria Putnam, Sea Grant coastal resources and communities specialist, agrees with the approach. “A lot of what we look at now is related to bacterial counts and whether the water is safe for human contact and consuming oysters. But we don’t have a lot of biological indicators to assess creek health.” Putnam continues, “I think that’s something we need to look at and focus on more, so we can really tell how these creeks are altered.”<\/p>\n\n\n\n
Mummichogs are an ideal type of fish for this study because they tend to stay in or near the location where they are spawned. Thus, the team theorized that mummichogs would be good barometers for the health of the creeks.<\/p>\n\n\n\n
As Buckel recounts it, the original grant proposal called for studying two creeks, but the energetic Rudershausen expanded the study to four creeks with antennas, plus two more creeks where he is monitoring the mummichog population.<\/p>\n\n\n\n
They are measuring physical parameters of the fish’s growth and movements, as well as biochemical metrics of fish health.<\/p>\n\n\n\n
Electronic Data<\/h2>\n\n\n\n Buckel and Hightower previously led Sea Grant-funded projects to monitor red drum and spot populations using tagging methods. However, mummichogs need an exceptionally small tag because of their size \u2014 they are about 2 inches long.<\/p>\n\n\n\n
The tags are radio-frequency tags known as Passive Integrated Transponder, or PIT, tags. The PIT tags are the same as those used for microchipping dogs and cats.<\/p>\n\n\n\n
The transceiver detects the electrical current that is produced when the magnetic chip in the tags is close to the antenna wire. Enclosed in PVC pipe, the wire is anchored in the creek and connected to the transceiver unit.<\/p>\n\n\n\n
Detecting small tags in marine waters is difficult because salt water masks electrical currents, Rudershausen explains. In tidal creeks it is doubly difficult because salinity varies with rainfall. A downpour can reduce the salinity of the creek. Fortunately, the reader automatically adjusts for the salinity changes.<\/p>\n\n\n\n
Rudershausen and Buckel credit Ben Letcher, Matt O’Donnell and Todd Dubreuil at the S.O. Conte Anadromous Fish Research Center in Turners Falls, Mass., for helping them to customize the system for salt water. That group continues to collaborate with the NC State team on improvements in antenna design and ways to analyze the data. The center, named for the late U.S. congressman Silvio O. Conte, was established by the USGS, and is affiliated with the University of Massachusetts Amherst campus.<\/p>\n\n\n\nRudershausen tags one of 40 fish on a November day. Photo by Sharon Settlage.<\/figcaption><\/figure>\n\n\n\nSeveral times a year, Rudershausen surgically implants upwards of 100 fish per creek with PIT tags, each coded with a unique combination of 13 numbers and letters. When the tagged fish passes near the antenna wire, it is logged as a detection event.<\/p>\n\n\n\n
To insert the tag into a mummichog, Rudershausen uses a sterile scalpel to make a small slit in the anesthetized fish’s belly and slides the tag in. Afterwards he applies an iodine mixture and returns the fish to a recovery tank. No suturing is required. In about 10 minutes or less, the fish is swimming about again. He has never lost a fish from the procedure, developed in collaboration with Craig Harms of NC State’s College of Veterinary Medicine.<\/p>\n\n\n\n
Once per month, Rudershausen captures mummichogs using minnow traps baited with dry cat food. He measures each fish’s weight, length and sex and checks how many of the captures are tagged. These data allow him to calculate how many fish are in each creek.<\/p>\n\n\n\n
Going with the Flow<\/h2>\n\n\n\n In an earlier Sea Grant-funded study, Rudershausen installed three antennas in Porters Creek, located in a rural area outside of the Morehead City limits off the Newport River.<\/p>\n\n\n\n
He found that he could follow the movements of individual fish in the creek. He initially tagged 44 fish and recorded 1,112 moves past the antennas over four months.<\/p>\n\n\n\n
A total of 42 of the 44 tagged fish were detected at some point between November 2010 and August 2011, indicating a high detection rate. But by the end of the study, the apparent survival was only 3 percent, which verifies other studies indicating that the fish are naturally short lived.<\/p>\n\n\n\n
They also are prey for birds, crabs and other fish. Rudershausen recounts a winter day when he saw a cormorant scooping up mummichogs. He also has seen blue crab and bluefish having mummichogs for a meal.<\/p>\n\n\n\n
The three antennas showed that mummichogs move predominantly in the direction of the tide. They move upstream into the creek headwaters during flood tide and leave the creek headwaters to return to the mouth of the creek, where it drains into the Newport River, late in ebb tide.<\/p>\n\n\n\n
Buckel explains that the original function of the antennas was to monitor any fish emigration from the creek, which they assumed would be rare. Instead the team found that the fish were regularly moving out of, and then back into, the marsh creek.<\/p>\n\n\n\n
“It was really beautiful data. Every day as the water started to recede, we’d see antennas 3, 2 and 1 register the fish as they moved out of the creek and as soon as the water started to come back in we’d see 1, 2, 3 as the fish came back in. We learned they were moving in and out with the tide and our original supposition that the bulk of these animals would stay in the creek above the antennas was incorrect,” Buckel recalls.<\/p>\n\n\n\n
The movements into the creek maximize the fish’s access to the intertidal marsh, which is flooded for about three hours, twice per day in Porters Creek.<\/p>\n\n\n\n
At high tides, when the marsh is flooded, mummichogs enter into the Spartina grass to feed and find refuge. A study conducted near Beaufort in the 1980s by National Oceanic and Atmospheric Administration Fisheries researcher William F. Hettler Jr., at the NOAA Beaufort Laboratory, used nets to capture fish during high tide in the marsh. Mummichogs were the most prevalent species.<\/p>\n\n\n\n
A Sea Grant-funded study from the 1970s by R.T Kneib and S.E. Stiven of the University of North Carolina at Chapel Hill, showed that mummichogs feed on small crustaceans, insects, algae, fecal pellets and detritus in the marsh grass. Because mummichogs are prey for larger fish such as red drum, they are an important part of the transfer of energy from the marsh to deeper-water fish species.<\/p>\n\n\n\n