NOTE Hernandez-Lopez et at: Age of Octopus vulgaris determined from concentric rings on beaks 
681 
Beak lateral wall length = -64. 166+ 1 9.522 In ( VML) 
Pearson's Correlation: r = 0.825; r 2 - 0.6808 
F = 580. 1 5; P < 0.001 ; n = 275 
Figure 2 
Relationship of beak lateral wall length to ventral mantle length (VML) of ben- 
thic Octopus vulgaris. 
chitinous structure such as the heaks (Raya and Hernan- 
dez-Gonzalez, 1998) or in calcium deposits in statoliths. 
Statoliths are the hard structures most commonly used 
for cephalopod age estimation (Lipinski, 1986, 1993; Arkh- 
ipkin, 1993), although the presence of concentric rings in 
the internal shell, beaks, and eye lenses have also been 
used (Clarke, 1965; Gonpalves, 1993; Raya and Hernan- 
dez-Gonzalez, 1998). When beaks are used, erosion of the 
rostral area during the life of the animal may bias age 
determination toward underestimation (some of the first 
rings may be eroded and therefore not counted). We found 
evidence of incomplete increments on the edge of the lat- 
eral wall, near the rostral tip area; therefore, ages we 
provide for benthic adults are to be considered minimum 
estimates. 
If rings on the lateral walls of the upper beaks are laid 
down daily and can be accurately counted even in the old- 
est specimens (as indicated by the pattern in paralarvae), 
then our results are consistent with a lifespan of 12-13 
months in the Canary Island waters. Rava and Hernan- 
dez-Gonzalez (1998) gave a lifespan of 10-12 months for 
octopus caught off the coast of northwest Africa (21-26°N ) 
