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Fishery Bulletin 99(4) 
Upjter beak Half upper beak 
(3D view) (inner view) 
Figure 1 
Diagram of upper beak of Octopus vulgaris and lateral wall showing growth bands, rostral tip area, the 
distal posterior beak end, and counting line. 
counted at least three times by the same person, and 
those with less than two identical counts were rejected 
from analysis. 
The number of rings in beaks of paralarvae was com- 
pared with the number of days each one lived. 
Results 
Octopus obtained from the small-scale fishery ranged in 
size from 4.8 to 165 mm VML, and weighed between 0.38 
and 3926 g. Females ranged from 60 to 165 mm VML and 
weighed from 215 to 3926 g. Males ranged from 58 to 
160 mm VML and from 200 to 3167 g in weight. We were 
unable to sex two individuals (4.8 mm VML, 0.38 g and 8.1 
mm VML, 0.60 g). Paralarvae ranged from 1.0 to 2.7 mm 
VML and from 0.001 to 0.005 g in weight. 
The internal lateral walls of upper beaks from 302 in- 
dividuals (27 paralarvae and 275 individuals in benthic 
stages of Octopus vulgaris) revealed a pattern of concen- 
tric bands deposited from the rostral tip of the beak to the 
opposite margin of the lateral wall, parallel to the beak 
edges. Both halves of the upper beaks showed similar spa- 
tial and density patterns of microstructures. Lower beaks 
showed no regularity in the pattern of bands along the 
lateral walls and were discarded. On the upper beaks the 
distance from the rostral tip to the distal end of the later- 
al wall showed a positive correlation with the VML (Pear- 
son’s correlation: r=0.825; PcO.OOl) (Fig. 2). 
Ring counts were more difficult near the rostral tip 
where rings were frequently discontinuous. Counts were 
easier to make near the edges of the lateral wall which 
was less highly pigmented. 
Paralarvae survived in tanks from 3 to 26 days. For 
48.1% of paralarvae, the concentric ring count in the later- 
al wall of the upper beak equaled the number of days that 
they lived. Otherwise, in 22.2% and 29.6% of paralarvae 
the number of rings counted were one more or one less, 
respectively, than the number of days of age. These data 
(Fig. 3) indicate that daily deposition of a growth incre- 
ment in the lateral wall of the upper beak begins on day 
one after hatching. The weight-age and VML-age relation- 
ships of paralarvae (Fig. 4, A and B) were similar to those 
found by Villanueva (1995), with differences attributable 
to rearing conditions. Given the correlation between incre- 
ment counts and age of paralarvae, we applied the upper 
beak ring count method for age determination of 272 com- 
mon octopus, ranging from 4.8 to 165 nun VML. Results 
should be taken with caution for the benthic stages of oc- 
topus pending the validation of growth of adults and the 
frequency of rings deposition. 
Increments counted on beaks from octopus collected in 
the wild ranged from 53 to 398 corresponding to indi- 
viduals of 0.38 and 3926 g body weight, respectively (4.8 
and 165 mm VML). Males and females had no difference 
in the number of rings counted in the lateral walls of up- 
per beaks (ANOVA, F=0.0006, P=0.98). The age of males 
ranged between 3.2 and 12.3 months (95-369 rings), and 
females ranged between 3.1 and 13.3 months (93-398 
rings), see Figure 5 (A and B) for weight-age and MVL-age 
relationships for benthic octopus. 
Discussion 
In Octopus vulgaris and other shallow-water cephalo- 
pods, regular patterns of activity and evidence of endog- 
enous rhythms induced by the light-dark cycles have been 
reported in both field and laboratory animals (Cobb et ah, 
1995). These endogenous rhythms may be reflected in a 
