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NOAA Commercial Fisheries • NERO
The marking methods involved in mark and recapture programs are almost as diverse as the types of animals examined. In our forests, some animals such as bears and wildcats are continually tracked using radio transmiting tags, humpback whale movements are followed using the markings on their tails (much like a fingerprint), migratory paths of many bird species have been traced using lightweight bands placed on birds' legs, genetic markers in salmon have been used to determine whether natural and aquaculturally raised fish interbreed, fin clipping is common in freshwater streams to examine the distance of travel within a river system and several billfish (eg. marlin, sailfish) have received tags which transmit data back to scientists by way of satellite. Each separate project has unique objectives and goals which must be weighed against the cost and effectiveness of the individual marking methods.
After
careful consideration of the marking methods available, the Cooperative Black
Sea Bass Tagging Project chose an internal-anchor tag as the primary marking
method. Internal-anchor tags are inserted into the body cavity through
a small incision on the ventral side of the fish. In this case, a 1/2"
incision is made, allowing the enlarged end of the tag to be securely inserted
above the musculature. An antibiotic solution is applied to the incised
area and the fish are placed into a holding tank for observation. Once
they have adjusted to the new appendage, they are gently released back into
the ocean, where they return to the bottom to hide among the obstructions. The
biologists performing the incisions must be selective in placing the tag so
no organs are damaged and minimal harm is brought to the animal. Proper
knowledge of black sea bass anatomy and tag insertion technique insure minimal
danger or chance of infection.
The objectives of this project are to determine the population size, exploitation rate and general movements of the northern Atlantic (Cape Hatteras, NC to the Gulf of Maine) black sea bass. There have been very few studies on the ecology of black sea bass; none have specifically examined population size or exploitation. This species is an increasing concern as biological indicators show a trend of overfishing and a decline in the reproductive population. Total catch of the species has declined over time (Figure 1) giving rise to concerns of a decrease in population size and total biomass. Although changes in fishery regulations may account for a part of the catch decline, a broader picture of the populations' size and exploitation rate is needed to improve our understanding of the black sea bass population trends.
FIGURE 1
Total Reported Commercial Catch In Metric Tons Per Year (1950-2001).
Data taken from the NMFS Commercial Fisheries website and NMFS MRFSS data.
or see the Northeast Regional Office of NOAA for other fishery related information and data.
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