FISHERY BULLETIN: VOL. 75, NO. 1 



90 

 80 

 70 



OB 

 OS 



I 60 



S 50 



I 40 

 30 



20 



10 







II. ■<rUcciis 



1 " ■•««* I (Fro. I 



lotbo 1971 ) 

 M. ppfodoims 



M. ■•rlictln 



M- blllMoris (llgelow I Schroadar 1953) 



M. olbidts (Present study) 



Mol«s 



Ftnalts 



1 2 3 4 5 6 7 8 9 10 11 

 AGE (years) 



FIGURE 9. — Comparative growth rates for five species of Atlan- 

 tic Merluccius: M. merluccius, M. capensis, and M. paradoxus 

 from various authors after Botha (1971, fig. 17), M. bilinearis 

 from Bigelow and Schroeder (1953), and M. albidus (present 

 study). 



TABLE ll. — Comparative length in centimeters by age for 

 Merluccius albidus, M. capensis, M. paradoxus, and M. pro- 

 ductus . 



1 Data from Table 1 of present study. 



Calculated lengths from Botha (1971). 



Calculated lengths (Nelson and Larkins 1970); Dark (1975) gives similar 

 calculated lengths for M. productus including estimates for 1 , 2, and 3 yr fish as 

 16.6, 26.2, and 41.1 FL. 



Growth rates of male and female M. productus 

 (Dark 1975) indicate that growth is rapid during 

 the first 3 yr but then slows perceptibly. Gulf of 

 Mexico M. albidus are larger than M . productus at 

 age 2. However, the growth rates of 3- to 5-yr-old 

 female M. albidus and M. productus appear 

 similar. Growth rates of males of these species do 

 not appear to be similar. Merluccius albidus from 



the Gulf of Mexico appear to grow faster than M. 

 bilinearis (Figure 9). 



A small number of female M. albidus were 

 collected in February 1970 below the head of De 

 Soto Canyon in depths of 550 to 730 m. These fish 

 ranged from 21 to 59 cm SL and showed modal 

 peaks at 36, 40, and 44 cm SL which were similar 

 to the peaks shown in Figure 8. Females collected 

 on the De Soto Canyon slope in June 1971 at 

 depths of 550 to 730 m showed modal peaks at 38, 

 42, and 45 cm SL. 



Length frequency data imply that males rarely 

 live longer than 3 yr whereas a large number of 

 females live at least 5 yr (Figures 8, 9; Tables 10, 

 11). However, longevity in other species of Mer- 

 luccius is reported as upwards of 13 yr for females 

 and 1 1 yr for males. Additional sampling lower on 

 the slope throughout the year may generate a 

 broader data base from which additional age- 

 classes could be defined bringing longevity of M . 

 albidus in closer agreement to other species of 

 Merluccius. Figure 8 suggests a high mortality 

 rate for 2- to 3-yr-old males residing higher on the 

 slope which probably increases their accessibility 

 to predators. Botha (1971) showed that male M. 

 paradoxus do not live as long as females and stated 

 that males over 7 yr of age are extremely rare. 



A length-weight curve for males and females 

 was computed from 1,920 specimens from the Gulf 

 of Mexico (Figure 10). Rate of weight increase was 

 similar in both sexes up to about 18 cm SL, af- 

 ter which the rate of increase for males became 

 greater possibly because males develop mature 

 gonads earlier. 



STANDING STOCK OF M. ALBIDUS 

 IN THE GULF OF MEXICO 



The standing stock estimate and confidence 

 interval for each stratum and for all strata are 

 listed in Table 12. Maximum density per drag in 

 June 1971 was 11 kg/hectare, mean density 3 kg/ 

 hectare, and minimum density 0.45 kg/hectare. 



Since trawl efficiency or catchability coefficient 

 (q) is unknown for offshore hake, a q of 1 was used 

 in the calculations thereby minimizing the 

 standing stock estimate. Catchability of any trawl 

 is somewhat dependent on several biological, 

 physiological, and adaptive characteristics of the 

 species sought which must be considered in as- 

 signing a value to q . Other species of hake come off 

 the bottom to feed and M. productus forms large 

 schools about 9 m off the bottom (Nelson and 



156 



