BIOLOGY OF OFFSHORE HAKE, MERLUCCIUS ALBIDUS, 



IN THE GULF OF MEXICO 1 



Bennie A. Rohr and Elmer J. Gutherz 2 



ABSTRACT 



Biological data of the offshore hake, Merluccius albidus, in the Gulf of Mexico are presented and 

 compared with those of other species of Merluccius . The species has been found from Georges Bank to 

 Rio de Janeiro, Brazil, in 192 to 1 , 1 70 m. In the Gulf of Mexico it occurs in greatest abundance in the De 

 Soto Canyon area in depths of 350 to 1,000 m. 



Merluccius albidus are segregated by size and sex on the continental slope with juveniles, males, and 

 young females found in depths less than 550 m and large, mature females found in depths exceeding 

 550 m. Mature males were smaller than females and grew at a reduced rate following the onset of 

 sexual maturity. 



Males and young females were found on the upper slope and older mature females found on the lower 

 slope. Spawning appeared to take place on or near the bottom in 330 to 550 m. Spawning in the southern 

 latitudes appears to occur from late spring to early fall and may be more protracted at the southern 

 limits of its range. Eggs and the earliest larval stages have been described only for M. albidus from New 

 England. 



Merluccius albidus are opportunistic feeders preying primarily on fishes, squid, and crustaceans. 

 Fishes make up about 75% of their diet, with species of Merlucciidae and Myctophidae consumed most 

 frequently. Prey species exhibited diel movement, but the similarity between day and night catch rates 

 of M. albidus suggests that offshore hake do not move far off the bottom in pursuit of prey. 



Density estimates suggested a small population of M. albidus in the northern Gulf of Mexico. 

 Merluccius albidus stocks in 370 to 730 m on the De Soto Canyon slope north of Tampa, Fla., are 

 estimated to be a minimum of 3.3 x 10 6 kg. 



Species of the genus Merluccius are distributed 

 worldwide in temperate and tropical waters but 

 are exploited primarily in temperate seas. Aspects 

 of their biology, distribution, and utilization have 

 been reported by numerous authors (Hickling 

 1927, 1933; Bigelow and Schroeder 1953, 1955; 

 Graham 1956; Fritz 1960; Lozano Cabo 1965; 

 Marak 1967; Botha 1969, 1971; Grinols and 

 Tillman 1970; and Nelson and Larkins 1970). 

 Northern Gulf of Mexico Merluccius are consid- 

 ered to be divergent forms of M. albidus (Karnella 

 1973). Several of the above authors have com- 

 mented on the similarity in life history patterns of 

 various species of Merluccius. Offshore hake, M. 

 albidus, display some of these same patterns, 

 indicating that aspects of their life histories are 

 similar to those documented for other species. 



Biological data concerning M. albidus are 

 sparse. Those reported in this paper are limited 

 primarily to the Gulf of Mexico. This study is a 



'Contribution No. 453, Southeast Fisheries Center, Pas- 

 cagoula Laboratory. 



2 Southeast Fisheries Center Pascagoula Laboratory, National 

 Marine Fisheries Service, NOAA, P.O. Drawer 1207, Pascagou- 

 la, MS 39567. 



Manuscript accepted June 1976. 



FISHERY BULLETIN: VOL. 75, NO. 1, 1977. 



composite of published accounts, data acquired 

 during resource assessment, gear evaluation and 

 general exploratory cruises, and results of 

 biological studies conducted by personnel of the 

 Southeast Fisheries Center Pascagoula Labora- 

 tory, National Marine Fisheries Service (NMFS), 

 NOAA. 



MATERIAL AND METHODS 



Specimens were collected with a variety of bot- 

 tom trawls (Table 1) equipped with mud rollers, 

 loop chain, floats, and usually a tickler chain. The 

 larger trawls (38 to 60 m headrope) were fished 

 with wooden bracket doors and ground cables 

 whereas the smaller trawls (12 and 22 m head- 

 rope) utilized wooden chain doors. Mesh size on the 

 larger trawls was 7.6 cm in the wings and body, 5.1 

 cm in the throat, and 4.5 cm in the cod end; smaller 

 trawls had 5.1-cm mesh throughout with 3.8 cm in 

 the cod end. In October 1971, a 22-m trawl with a 

 1.3-cm inner liner was used to collect juvenile M. 

 albidus. Rough bottom areas were fished with a 

 12-m flat or semiballoon trawl and smooth areas 

 with larger trawls (22 to 68 m). 



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