Rocha-Olivares: Age, growth, and mortality of Lutjanus peru 
569 
25 
20 
15 
10 
5 
females 
n = 262 

"i 1 1 1 1 i 
10 
15 
20 
25 
30 
35 
Age groups (years) 
Figure 6 
Age structure of Lutjanus peru females, males, and sexes combined of di- 
rectly aged specimens collected at La Paz fish market or caught by hook- 
and-line and shrimp trawling activities off the southeast coast of Baja 
California Sur. Data represent whole-otolith ages (up to 15 years) and sec- 
tioned-otolith ages (beyond 15 years). Most of the unsexed individuals are 
undifferentiated fish but some are reproductively active adults that could 
not be sexed. 
red snapper (10 to ca. 100 cm TL). The 
lower size limit of L. peru in the hook- 
and-line catch ( 18.3 cm) was very close to 
that reported for L. campechanus fished 
with similar size hooks in the Gulf of 
Mexico (18.0 cm) (Nelson and Manooch, 
1982). This might indicate a comparable 
vulnerability due to morphological simi- 
larity. Because fishermen do not typically 
change hook size to target small snappers 
(personal observation), the preponder- 
ance of small fish in the catch (ca. 61% in 
numbers) that had not yet recruited to 
the spawning population was not due to 
gear selectivity. The upper limit of the 
range was also sampled and a length 
record is reported for the species. Thus it 
seems unlikely that the growth param- 
eters of L. peru may be biased owing to 
inadequate sampling of its length-range. 
Age determination 
The monthly fluctuation in the percent- 
age of translucent margins suggests 
that the period of translucent ring for- 
mation takes place in the summer dur- 
ing the spawning season (Fig. 3). This 
observation enabled Rocha Olivares and 
Gomez Munoz ( 1993) to indirectly vali- 
date whole-otolith rings as annuli in L. 
peru up to 10 years old. 
The greater precision of sectioned 
otoliths suggested by %D and %E re- 
sulted from a more direct access to the 
marking patterns of the structure. Dif- 
ferent degrees of wear and tear were 
noted on the anterior margin of large 
scales, which contributed to age deter- 
mination variability within reading 
rounds. Comparison of individual age 
estimates ofL. peru from whole otoliths, 
sectioned otoliths, and scales provided 
evidence supporting age underestima- 
tion by the latter. This underestimation 
by scales has also been observed in the 
Antarctic fish Notothenia gibberifrons 
Lonnberg (Coggan et al., 1990). Libby (1985) also 
concluded that whole-otolith ages were more accu- 
rate and less subjective than scales for ageing the 
anadromous alewife, Alosa pseudoharengus (Wilson). 
As in other species, however, this effect does not seem 
to be very important during the first five years in L. 
peru. For example, Lou (1992) found that either 
scales or sectioned otoliths provided reliable age es- 
timates up to five years in the tropical parrotfish 
Scarus schlegeli (Bleeker), and Lowerre-Barbieri et 
al. (1994) reported similar findings in weakfish, 
Cynoscion regalis (Bloch and Schneider), to age six. 
Apparently, otoliths are more reliable structures than 
scales (Beamish and McFarlane, 1987) over most 
ages, and this study extends this observation to the 
Pacific red snapper. 
