FISHERY BULLETIN: VOL. 75, NO. 1 



1960), suggesting a low population level, unavail- 

 ability to the fleet, or lack of recognition by the 

 fishermen. However, mixed commercial con- 

 centrations of M. albidus and M. bilinearis were 

 found south of Hudson Canyon on the edge of the 

 shelf by the RV Albatross III (Edwards et al. 1962) 

 and on Georges Bank by West German stern 

 trawlers (Mombeck 1971). 



Exploratory fishing data from the Pascagoula 

 data files showed that M. albidus composed 25% of 

 the total finfish available to trawl gear between 

 350 and 1,000 m on the Mississippi slope and 60% 

 between 450 and 730 m on the west Florida-De 

 Soto Canyon slope. Several large catches con- 

 taining individual fish weighing in excess of 0.45 

 kg have been made by NMFS vessels. 



In the Gulf of Mexico, M. albidus have been 

 taken at depths of 142 to 1,100 m. Between 1950 

 and 1971, NMFS vessels caught M. albidus at 73% 

 of all trawl stations in depths of 182 to 1,100 m. 



Relative apparent abundance of M. albidus in 

 the Gulf of Mexico was established by computing 

 catch rates based on historical fishing records. 

 Highest concentrations occurred in the northern 

 Gulf between Tampa, Fla., and the Mississippi 

 Delta. Prior to the M. albidus assessment cruise in 

 June 1971, catch rates of 14 kg/h (31 pounds/h) or 

 greater occurred at only 37 Gulf of Mexico stations 

 (Figure 1) of which 78% had catch rates less than 

 50 kg/h. These stations are primarily in the 

 northeast quadrant of the Gulf of Mexico in depths 

 of 370 to 930 m (Figure 1). Maximum catch rates 

 recorded for this period in the Gulf of Mexico are as 

 follows: north Gulf, De Soto Canyon, 640 m, 161 

 kg/h; east Gulf, off Tampa, 490 m, 284 kg/h; west 

 Gulf, east of Brownsville, Tex., 430 m, 31 kg/h; 

 south Gulf, east of Veracruz, Mexico, 540 m, 22 

 kg/h; and north of Campeche Bank, 550 m, 20 

 kg/h. 



Nineteen 5-h trawling stations were completed 

 on the De Soto Canyon slope in June 197 1 to obtain 

 biological data and estimate the size of the M. 

 albidus population. Catch rates varied from 5.7 to 

 144.0 kg/h in depths of 370 to 730 m and averaged 

 38.7 kg/h (Figure 1). 



Highest catch rates of M. albidus after June 

 1971 were 12.5 kg/h in 440 m on the western slope 

 of De Soto Canyon, 15.5 kg/h in 550 m south of Dry 

 Tortugas, and 58.5 kg/h in 420 m on the De Soto 

 Canyon east slope. These catch rates may be arti- 

 ficially low, as the trawls used were not rigged 

 specifically for catching M. albidus. Abundance in 

 the western and southern Gulf of Mexico is 



unknown due to the considerable area of un- 

 trawlable bottom off Texas, western Louisiana, 

 and in the Gulf of Campeche. 



Merluccius albidus were caught at depths of 200 

 to 795 m in the Caribbean Sea including the insu- 

 lar slopes of the Antilles. During a 1970 trawl 

 survey on the Caribbean slope between Belize and 

 Aruba, it was taken most frequently at depths of 

 450 to 630 m north of Aruba. Caribbean trawling 

 records give no indication of any significant 

 concentrations of M. albidus. However, Cervigon 

 (1964) reported that M. albidus may be of 

 economic importance off Venezuela in depths 

 greater than 370 m. 



RELATION OF DEPTH TO SIZE AND SEX 



Studies have shown that size increases with 

 bottom depth in various species of hake (Grinols 

 and Tillman 1970). Rohr (1972) showed that M. 

 albidus segregates by size and sex on the conti- 

 nental slope in the Gulf of Mexico (Figures 2, 3). 

 Juveniles of both sexes, young adult females, and 

 adult males inhabit the upper slope (depths <550 

 m) while larger, mature females are concentrated 

 on the lower slope (depths >550 m). This pattern is 

 clearly demonstrated when plotting the male- 

 female ratio vs. depth (Figure 3). 



A similar distributional pattern of M. albidus 

 was reported on the Honduran-Panamanian slope 

 by Bullis and Struhsaker (1970) and observed by 

 the senior author on both the western and south- 

 ern Caribbean slopes from Belize to Aruba. 



W. i.o- 



S 0.5- 



640 

 METERS 



FIGURE 2. — Average weight of individual Merluccius albidus vs. 

 depth for 487 trawl stations in the Gulf of Mexico. 



150 



