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Fishery Bulletin 89(1), 1991 



1968, Wolf and Rathjen 1974). For the above reasons, 

 tilefish are susceptible to capture on longlines (Nelson 

 and Carpenter 1968, Wolf and Rathjen 1974, Grimes 

 et al. 1982, Cody et al. 1981) and overfishing (Harris 

 and Grossman 1985). 



Yellowedge grouper Epinephelus flavolimbatus are 

 also a target of the developing Gulf longline commer- 

 cial fishery (Prytherch 1983, Graham 1978). However, 

 even less is known about the life history andjtopula- 

 tions of this species than of tilefish. They are apparent- 

 ly present in commercial concentrations off Texas in 

 the 128-274 m depth zone (Nelson and Carpenter 1968). 

 On only 90 trips in the Gulf in 1982 over 65,000kg of 

 yellowedge grouper were landed (Prytherch 1983). 

 However, their frequent distribution around rock and 

 coral formations may preclude sustained commercial 

 catches because of gear loss (Graham 1978). 



This study was conducted to contrast "fishing out" 

 an area with bottom longlines to direct visual observa- 

 tions from a small research submersible as methods for 

 determining population sizes of tilefish, yellowedge 

 grouper, and other deepwater fishes. The impact of 

 longline fishing on these populations within a limited 

 area was also determined. 



Materials and methods 



Preliminary activities 



In May 1984 the NOAA ship Oregon II spent 6 days 

 surveying an area measuring 95 km east-to-west (94° 

 10' long, to 95°00'W long.) between 183- and 457-m 

 depths directly south of Galveston, Texas. Bottom con- 

 figuration and acoustic signatures of fish were noted 

 with a color-enhanced fathometer. Eleven bottom 

 longline sets were made during each day to locate areas 

 of high tilefish and yellowedge grouper catch rates 

 (5*0.3 fish/100 hook-hours). Based on these preliminary 

 cruises, specific sites were chosen for the submersible 

 and longline studies described in this paper. Three days 

 (10-13 September 1984) were spent by the Oregon II 

 making detailed charts of each study site prior to the 

 arrival of the submersible. Bathymetric charts of each 

 site were developed using a depth sounder and Loran 

 "C" plotter. These charts represented an area 2.6km 2 

 (lnmi 2 ) and were contoured by 10-m depth intervals. 

 The trackline interval used in mapping was about one 

 track per 15 m. The charts were duplicated and copies 

 were provided to the Harbor Branch Foundation's RV 

 Johnson prior to the beginning of submersible and 

 fishing activities. This allowed both vessels to track and 

 plot the position of the submersible and location of 

 longline sets precisely. 



Figure 1 



Tilefish study area (center point at 27°40.0'N lat. and 

 94°22.8'W long.) showing depth contours in meters, submer- 

 sible transect tracks (dashed lines), and distribution of longline 

 sets (solid lines) within the southern part of the study area. 

 Chart represents one square nautical mile. 



Study area 



Tilefish A study area (1.9 x 1.1km) was selected off 

 the north Texas coast at 27°40.0'N lat. and 94°22.8W 

 long. (Fig. 1). The area was a broad ridge with a mini- 

 mum depth of 304 m. Approximately 50% of the study 

 area was less than 31 1 m in depth with the bottom drop- 

 ping gradually away to 316-318m at the northern part 

 of the area, and 320-329 m in the southwestern part. 

 The area was almost entirely covered with a soft sand- 

 clay mixture, characteristic of tilefish habitat along the 

 entire U. S. eastern coastline (Freeman and Turner 

 1977, Able et al. 1982, Twichell et al. 1985, Grimes 

 et al. 1986). However, the substratum was less cohesive 

 than in east coast tilefish grounds. A fin-stabilized 

 metal rod, dropped from a height of 1.2 m by the sub- 

 mersible's manipulator arm, penetrated 80-100 cm in 

 the gulf and 20-30 cm on east coast tilefish grounds 

 (C.B. Grimes et al., NMFS Panama City Lab., unpubl. 

 data for Mid-Atlantic Bight and South Atlantic off 

 Florida). 



Many of the burrows in the study area were dug at 

 an oblique angle into the substratum or into a sloping 

 face, instead of perpendicular as is characteristic of east 

 coast tilefish on flat bottom (Able et al. 1982, Grimes 

 et al. 1986). It was evident that the low cohesiveness 



