SEA 



SCIENCE 



ONE 



looking at the rings of a felled tree. Each ring 

 serves as a marker in time, chronicling years 

 of drought and disease, years of growth and 

 abundance. Sometimes, foresters use the rings 

 to tell us about our own history. A 100-year-old 

 tree was only six when the Titanic sank, but 95 

 on 9/1 1 — and lived through many historical 

 milestones in between. 



Chris Taylor, a researcher at North 

 Carolina State University's Center for Marine 

 Science and Technology 

 (CMAST), studies the past 

 through rings too. As part of an 

 N.C. Fishery Resource Grant 

 (FRG) project, Taylor spends his 

 time studying the rings found in 

 the otoliths of southern flounder. 



As a fish grows, calcium 

 carbonate material is deposited, 

 forming a bony structure in the 

 fish's "ear" — the otolith — to 

 help keep the fish balanced. The 

 rings of the otolith are laid down 

 for each day and year of growth. 

 Fishery biologists use these rings 

 to age fish, much like foresters 

 aging trees. 



But much more than age 

 can be gleaned from otolith rings. 

 As the rings are added, chemical 

 elements from the surrounding 

 water body incorporate into each layer. 



"Layers added while the fish are in 

 estuaries have higher concentrations of barium 

 and lower concentrations of strontium, for 

 example," says Taylor, who is examining these 

 chemical signatures to track how southern 

 flounder use various coastal aquatic habitats. 



A mass spectrometer and laser operated 

 by the Wood's Hole Oceanographic Institute 

 in Massachusetts affords Taylor the fine detail 

 needed to examine the tiny otoliths. "Using a 

 laser, we can sample very small amounts of 

 the otolith — within and between rings — in 

 regions that would represent winter, spring, 

 summer and fall," he says. 



Taylor uses chemical cues found in the 

 rings to determine how long the fish are in 



can learn a lot by estuaries versus how long they remain offshore. 



The results of his study will provide a better 

 understanding of the migration patterns of 

 southern flounder. 



Fishery biologists know that southern 

 flounder spawn in the ocean and that larvae and 

 juvenile flounder migrate into estuaries in late 

 winter. In North Carolina, most flounder stay in 

 the upper reaches of estuaries for their first year 

 of life, where the marshy shoreline offers them 

 food and protection from large predators. 



ABOVE: Tliis otolith is from a 4-year-old southern 

 flounder caught in October 2004. The core, or 



primordium, is the region that contains material 

 accumulated during larval and early-juvenile 

 growth. Researcher Chris Taylor examines the 

 otolith rings to determine how this fish moved 

 inshore/offshore over its lifetime. 



When the flounder mature, they migrate 

 offshore to join spawning adults. Previous 

 studies suggest that flounder tend to travel south 

 over their lifetime, but generally move into 

 estuaries during the spring and summer months, 

 presumably to feed on the abundant juvenile 

 fish and crustaceans found there. 



But questions remain. How long do 

 flounder stay in the ocean? Do they return to 



estuaries every spring? Do males and females 

 follow the same pattern of behavior? 



Taylor is trying to answer some of these 

 questions by studying the otolith rings. 



N.C. FLOUNDER FISHERY 



Southern flounder became a major fishery 

 in North Carolina during the 1980s and 1990s, 

 when restrictions on the historically important 

 summer flounder fishery increased demand for 

 other flounder. Local fishers turned to southern 

 flounder, according to Bob Hines, 

 FRG coordinator for North 

 Carolina Sea Grant. 



Southern flounder has 

 become such a mainstay in the 

 commercial fishing community 

 that the N.C. Division of 

 Marine Fisheries (DMF) now 

 considers the stock "overfished." 

 In response, DMF approved a 

 statewide Southern Flounder 

 Fishery Management Plan (FMP) 

 in 2005 that imposed new harvest 

 guidelines to protect the fishery 

 and help it recover. 



To reduce the amount of 

 flounder harvested, the FMP 

 increased the allowable mesh 

 size of gill nets and raised the 

 minimum legal size for southern 

 flounder from 13 inches to 

 14 inches. Increasing the mesh size and the 

 minimum legal size allows more young fish 

 to remain in the water and contribute to the 

 spawning population. A larger spawning stock 

 will mean more new flounder are added to the 

 population every year, helping rebuild the fishery. 



Although many people agree that 

 something needs to be done to protect the fishery, 

 not everyone agrees that statewide regulations are 

 the best approach. 



"When the [2005] FMP was being 

 developed, a lot of people wanted to see more 

 regional variation in management," says Chris 

 Batsavage, fisheries biologist at DMF. "We 

 considered it at the time, but couldn't really 

 develop that, because of data deficiencies for 



Continued 



Coastwatch I Spring 2006 I www.ncseagrant.org 23 



