Madeira and Joyeux: Distribution patterns of tidepool fishes on a tropical flat reef 
307 
Table 1 
Morphometric characteristics, substrate composition, macroalgae cover, and physicochemical parameters of pools at Praia dos 
Castelhanos, Espirito Santo, Brazil. Pools were characterized once for depth, surface area, volume, and rugosity and every three 
months between August 2005 and June 2007 for substrate, cover, and physicochemical parameters (n = 8 for all pools except 
pool 1 where n= 7). *=mean (range: minimum-maximum). Depth (max)=mean depth (and maximum depth); area=surface area; 
vol.=volume; rug.=rugosity. 
Pool 
Morphometric characteristics 
Substrate 
Cover 
Physico-chemical parameters 
Depth (max.) 
cm 
Area 
m 2 
Vol. 
m 3 
Rug. 
Sand 
% 
Gravel 
% 
Rock 
% 
Algae 
% 
Temperature* 
°C 
Salinity* 
1 
8.30(20.5) 
6.35 
0.53 
1.11 
30 
10 
60 
20 
26.1 (22.5-35.0) 
28.1 (17.0-35.8) 
2 
22.2(36.3) 
10.15 
2.24 
1.19 
80 
10 
10 
40 
24.4 (21.5-29.6) 
34.3 (32.0-38.0) 
3 
17.4 (25.5) 
1.36 
0.24 
1.26 
30 
60 
10 
40 
24.8 (22.0-30.1) 
34.3(31.4-37.0) 
4 
28.2 (49.0) 
7.88 
2.22 
1.30 
40 
20 
40 
70 
24.2 (21.8-29.7) 
34.5 (32.0-37.0) 
5 
23.8 (46.0) 
16.12 
3.81 
1.20 
10 
10 
80 
30 
24.7 (22.2-28.0) 
34.8(31.3-39.0) 
6 
25.6(51.0) 
6.52 
1.67 
1.27 
20 
50 
30 
40 
24.5 (22.2-24.9) 
34.7 (31.0-38.0) 
corresponded to 100% of bottom cover. The ichthyofauna 
was collected on the second sampling day with hand nets 
and with application of water-based rotenone solution 
(Polivka and Chotkowski, 1998; Gibson, 1999) and was 
later fixed in 10% formalin. Due to seasonal variation 
in beach profile, tidepool 1 was covered by sand during 
the August 2006 sampling. 
Sample processing 
The fishes were measured (total length; TL) to the 
nearest mm and weighed (individual total wet weight; 
W) at 0.01 g precision. The species were categorized 
by their degree of residency in pool habitats (modified 
from Griffiths, 2003) as permanent residents, oppor- 
tunists, and transients. Permanent residents (PR) can 
spend their entire life in pools and are frequently highly 
adapted for intertidal life. Opportunists (O) spend only 
part of their life history in pools, usually as juveniles 
or during high tide feeding excursions, when they are 
trapped in pools. Transients (T) are species that only 
occasionally or accidentally enter pools, generally have 
no specialized adaptations for intertidal life, and nor- 
mally occur in large rockpools for a short period of time 
(from a tidal cycle to several weeks). In this study, the 
assignment of species to categories was based upon fre- 
quency of capture, life stage(s) present in pools, species 
size, and occurrence in the infralittoral zone. 
Data analysis 
Temperature and salinity data were tested for normality 
by the Kolmogorov-Smirnov-Lilliefors test (Zar, 1999) 
and the data were shown to be normally distributed 
(P>0.05). Variation in temperature and salinity during 
the ebb tide was tested though repeated-measures 
ANOVA (n- 8; except n=7 for tidepool 1), and contrasts 
of “beginning vs. middle” and “beginning vs. end” were 
tested. The Mauchly test was used to verify data sphe- 
ricity and the F-value obtained from the Greenhouse- 
Geisser test was used when sphericity assumptions were 
violated. The fish community of each pool was described 
by the mean number of individuals, number of taxa, 
Shannon-Wiener index (using log e ), and Pielou's even- 
ness. Friedman nonparametric tests were used to detect 
differences among pools with significance estimated 
through Monte Carlo resampling (10,000 runs) (Zar, 
1999). The mean length and weight of all individuals 
were tested among pools by using Kruskal-Wallis non- 
parametric tests for independent samples with Monte 
Carlo resampling (10,000 runs). 
Nonmetric multidimensional scaling (nMDS) was 
used to determine the similarity between rockpools by 
using 1) the morphometric characteristics (4 variables 
[area, mean depth, volume, rugosity] x 6 pools), 2) the 
physicochemical parameters of the water (6 variables 
[mean, minimum and maximum for temperature and 
salinity] x 6 pools), and 3) the fish community structure 
(64 variables [=taxa]x6 pools) by using total abundance 
and total weight (summed up across the eight sampling 
events). Data were transformed (fourth th root) and ma- 
trices were built with the Bray-Curtis coefficient. 
Results 
Characteristics of rockpools 
The pools differed in morphometric characteristics but 
were similar in their physicochemical setting, except for 
pool 1 (Table 1). Changes during low tide were exacer- 
bated in pool 1 (Fig. 2) because of groundwater inflows 
(which lowered salinity during the rainy season) and 
shallowness (which allowed temperature to rise because 
of the high ratio between area [i.e., insolation] and 
volume). In extreme cases, a thermopycnocline formed 
within the pool (without apparent effect on the ich- 
thyofauna; senior author, personal observ.). Besides 
