Abstract .- Tilefish Lopholatilus 

 chamaeleonticeps and yellowedge 

 grouper Epinephelus flavolimbatus 

 are deepwater fishes and targets of 

 a relatively recent bottom longline 

 fishery in the Gulf of Mexico. They 

 are long-lived, slow growing, have 

 very limited movements and distri- 

 bution, and are susceptible to long- 

 lines. However, population size and 

 life-history parameter estimates are 

 generally unknown for Gulf fish. This 

 study compared two methods for 

 estimating population sizes to deter- 

 mine the most cost-effective one for 

 use on long-term fishery-indepen- 

 dent stock assessments. Bottom long- 

 lines were used to deplete fish from 

 a small area, and a regression of 

 catch per effort on cumulative catch 

 was used to estimate the area's popu- 

 lation prior to fishing. The popula- 

 tion was also estimated by counting 

 fish burrows from a submersible and 

 expanding the mean number per unit 

 area by the study site's area after 

 correcting for the number of occu- 

 pied burrows. Longlines and submer- 

 sibles provided significantly different 

 estimates of tilefish populations, the 

 only species for which estimates 

 could be compared. Longline esti- 

 mates were probably more accurate 

 because errors in area estimation 

 and double counting were evident in 

 submersible data. Longlines were 

 less expensive to operate ($5000 vs. 

 $8000 per day) and they afforded col- 

 lection of size, age, and sex data on 

 each fish caught. These data were 

 not available from the submersible. 

 Longlines could be used more cost- 

 effectively than submersibles in 

 determining long-term population 

 changes. However, direct observa- 

 tion of fish behavior was not avail- 

 able from longlines, but was from the 

 submersible. Submersibles also pro- 

 vide data on habitat and gear assess- 

 ment, including deployment, effici- 

 ency, bait predation, and potential 

 catch loss during retrieval. 



Comparison of Two Techniques 

 for Estimating Tilefish, Yellowedge 

 Grouper, and Other Deepwater 

 Fish Populations 



Gary C. Matlock 



Fisheries Division, Texas Parks and Wildlife Department 

 4200 Smith School Road, Austin, Texas 78744 



Walter R. Nelson 



Southeast Fisheries Science Center, National Marine Fisheries Service, NOAA 

 75 Virginia Beach Drive, Miami, Florida 33149 



Robert S. Jones 



Marine Science Institute. University of Texas at Austin 

 P.O. Box 1267, Port Aransas, Texas 78373 



Albert W. Green 



Environment Assessment. Texas Parks and Wildlife Department 

 4200 Smith School Road, Austin, Texas 78744 



Terry J. Cody 



Coastal Fisheries Branch, Texas Parks and Wildlife Department 

 100 Navigational Circle, Rockport, Texas 78382 



Elmer Gutherz 



Mississippi Laboratory, National Marine Fisheries Service, NOAA 

 P.O. Drawer 1207, Pascagoula, Mississippi 39567 



Jeff Doerzbacher 



I 1505 Oak Branch Drive, Austin, Texas 78737 



Manuscript accepted 1 August 1990. 

 Fishery Bulletin, U.S. 89:91-99 (1991). 



Tilefish Lopholatilus chamaeleonti- 

 ceps support an economically impor- 

 tant bottom longline fishery in the 

 Mid- Atlantic Bight (Grimes et al. 

 1980, Turner 1986), and are the focus 

 of a developing longline fishery in the 

 South Atlantic Bight and the Gulf of 

 Mexico (Katz et al. 1983, Low et al. 

 1983). Impacts of this development in 

 the Gulf are unknown because popu- 

 lation sizes and life-history param- 

 eter estimates there are generally 

 unknown. However, the potential 

 for recruitment overfishing appears 

 large even at relatively low fishing ef- 

 fort because of the fish's life history 

 (Harris and Grossman 1985). The fish 



is long-lived, slow growing (Turner et 

 al. 1983, Harris and Grossman 1985), 

 has limited movement (Grimes et al. 

 1983, 1986), and is restricted to tem- 

 peratures of 9-14°C (Grimes et al. 

 1986, Freeman and Turner 1977). 

 Tilefish are burrowers, requiring a 

 clay substrate that is soft enough to 

 allow burrowing, but firm enough for 

 maintenance of burrows that may ex- 

 ceed 1 m in diameter and 3 m in depth 

 (Able et al. 1982, Grimes et al. 1986, 

 Twichell et al. 1985). In the Gulf of 

 Mexico this is a narrow geographic 

 area along the outer edge of the con- 

 tinental shelf between depths of 229 

 and 411m (Nelson and Carpenter 



91 



