May 29, 2001 COLLEGE STATION, Texas -- Humans have all sorts of ways of telling where an individual is from -- passports, birth certificates and sometimes even physical appearance - but identifying a fish's origins is not so easy.
By analyzing the earstones of red drum, Texas A&M University at Galveston marine biologist and Sea Grant researcher Jay Rooker hopes to identify red drum nursery grounds and determine the contribution of each area to the adult red drum population.
Earstones, or otoliths, can provide this information. Otoliths are part of the inner ear system and used for hearing and balance. They are formed as the fish grows and are constructed from chemicals contained in the seawater. If scientists can identify earstone compositions that are unique to particular bays or ecosystems, then they can determine where a fish originated.
"Based on differences in the water chemistry of different bays, we expect that the otolith chemistry will be distinct," Rooker said. "We can use the technique to identify the source of adult red drum stocks in Texas."
If the project can identify the major sources of red drum, he said, then that information will let fishery managers know which nursery grounds need to be protected.
"If we can understand what areas are important nursery grounds - from a management standpoint, that definitely will help when we try to enhance the recovery of the stock," he said.
This project, which is funded by the Texas Sea Grant College Program, also may help determine stocking practices in which officials release farm-raised fish into the wild to boost the numbers in a population. Researchers hope to show whether fish from different areas of the coast intermingle, Rooker said.
For example, red drum growing up along Texas' northern coast may not mix with fish from the south. If this is the case, he said, then fishery officials may need to stock northern areas only with fish from that portion of the coast.
Rooker said he also will compare fish originating in nursery grounds with a lot of sea grasses to fish from areas with no sea grasses to see if they have earstones different from one another. If so, this would allow scientists to determine whether one area is more productive than the other in terms of the number of red drum coming from those areas.
"The real value is that if we know that certain bay habitats are contributing more than other bays, it may tell us something about the value and health of different ecosystems or bay habitats along the Texas coast," Rooker said.
The National Sea Grant College Program is a partnership of university, government and industry, focusing on marine research, education and advisory service. The Sea Grant Program is a practical, broad-based effort to promote better understanding and use of marine resources through research, education, extension and information transfer.
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