NOTE Hazin et al.: Distribution and relative abundance of Prionace glauca 



477 



Of 810 specimens, 652 (about 80%) were male 

 and 158 were female (about 20%). Overall, the sex 

 ratio (male/female) for the entire period was 4.12:1. 

 The sex ratios for each month are given in Table 4. 



Females ranged in size from 162 to 226 cm and 

 males from 156 to 250 cm (Fig. 5). Seasonal fluc- 

 tuation in male CPUE during 1990 was different 

 among age groups (Fig. 6). From February to May, 

 ages ranged from 4.5 to 8.5 years, with most (83%) 

 individuals between 6 and 8.5 years old (83%). The 

 CPUE rise in June— July was due to an increase 

 in the same age classes as from February-May. 

 Some older specimens from 9 to 10.5 years also 

 appeared. The CPUE offish younger than 7 years 

 decreased markedly in August. During Septem- 

 ber-October the CPUE of ages 7.5 to 10 increased 

 sharply. In November-December the CPUE of age 

 classes from 7.5 to 8.5, and also 9.5, were reduced, 

 whereas the CPUE of other age classes did not change 

 much. From February to July, younger fish (4.5 to 

 7.5 years) were more abundant than from August to 

 December, their CPUE being particularly high in 

 June-July From August to December, fish older than 

 7.5 years had a higher CPUE than in the previous 

 months, with a peak in September-October. 



The calculated depth of longline hooks during 137 

 longline fishing operations of 1990 ranged from 87 

 to 206 m (Table 5). The figures given in this table 

 approximate the actual depths of longline hooks. The 

 most striking feature of the DBT profiles is the pres- 



Jan . Feb . Mar . Apr . May Jun . Jul . Aug . Sep . Oct . Nov . Dec . 

 Month 



Male 1987 -*- Male 1990 -t— Male 1991 

 Female 1987 — *— Female 1990 *- Female 1991 

 — • — Sea surface temperature 



Figure 4 



Monthly mean sea surface temperature in 1990 and 

 monthly mean catch per 100 hooks (CPUE) of male 

 and female blue shark, Prionace glauca, in the south- 

 western equatorial Atlantic Ocean, from August to 

 December 1987 and from February 1990 to Decem- 

 ber 1991. 



Table 3 



Analysis of variance (ANOVA) and expected mean squares 

 for comparison of monthly mean CPUEs of blue sharks, 

 Prionace glauca, caught by the FV Argus, during 325 

 longline sets, from August to December 1987 and from 

 February 1990 to December 1991, in the southwestern 

 equatorial Atlantic Ocean. 



Source of 

 variation 



Degrees of 

 freedom 



Sum of 

 squares 



Mean 

 squares 



Month 



Error 



Total 



24 

 300 

 324 



11.41 

 30.68 

 42.09 



0.48 

 0.10 



4.65 <0.0001 



155-165 176-185 196-205 216-225 236-245 



166-175 186-195 206-215 226-235 246-255 



Fork Length (cm) 

 n= 104 



155-165 176-185 196-205 216-225 236-245 



166-175 186-195 206-215 226-235 246-255 



Fork Length (cm) 

 n= 374 



Figure 5 



Length-frequency distribution of male and female 

 blue shark, Prionace glauca, in the southwestern 

 equatorial Atlantic Ocean, from February to Decem- 

 ber 1990 and November to December 1991. Males: n 

 = 374; min. = 156 cm; max. = 250 cm. Females: n = 

 104; min. = 162 cm; max. = 226 cm. 



