305 
Distribution patterns off tidepool fishes 
on a tropical fiat reef 
Raphael M. Madeira (contact author) 
Jean-Christophe Joyeux 
Email address for contact author: raphaelmacieira@hotmail.com 
Laboratorio de Ictiologia 
Departamento de Oceanografia e Ecologia 
Universidade Federal do Espirito Santo 
Av. Fernando Ferrari, 514 
Goiabeiras, 29075-910 
Vitoria, Espirito Santo, Brazil 
Abstract — Rockpools on a tropical 
flat reef off the southeastern coast of 
Brazil were sampled to determine the 
influence of pool morphometry and 
water characteristics on fish com- 
munity structure. The pool closest to 
the inner fringe of the reef had lower 
salinity and higher temperature due 
to inflow of groundwater. The other 
pools varied only with respect to their 
morphometric characteristics, algal 
cover, and bottom composition. Spe- 
cies with a strong affinity for estu- 
arine-like waters characterized the 
pool closest to the beach and distin- 
guished its fish community from that 
of the other pools. Instead of being 
strongly structured by the physico- 
chemical setting and position in the 
reef, fish communities of the other 
pools were determined by behavioral 
preferences and intra- and inter- 
specific interactions. Differences in 
community structure were related to 
pool size (the larger sizes permitting 
the permanency of schooling species), 
to algal cover (which allowed camou- 
flage for large predatory species), to 
bottom composition (which provided 
substrate for turf flora available to 
territorial herbivores), and to eco- 
logical effects (e.g., competition, ter- 
ritoriality, and predation). Although 
distribution patterns of tidepool 
fishes have previously been related 
to the availability of niches, indepen- 
dent of pool position in the reef, our 
results show synergistic interactions 
between water properties, presence 
or absence of niches, and ecological 
relationships in structuring tidepool 
fish communities. 
Manuscript submitted 24 November 2010. 
Manuscript accepted 6 May 2011. 
Fish. Bull. 109:305-315 (2011). 
The views and opinions expressed 
or implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National Marine 
Fisheries Service, NOAA. 
Habitually, at low tide most fishes of 
the intertidal zone are concentrated 
in tidepools. There, physicochemical 
(e.g., temperature and salinity) and 
biological (e.g., recruitment) variables 
are inherently related to the duration 
of pool isolation from the sea (Gibson, 
1986). Thus, isolation has been sug- 
gested to be a determinant for the 
establishment and maintenance of a 
fish community (e.g., Gibson, 1972) 
and has become one of the “templates” 
onto which fish distribution patterns 
are established, either partially or 
totally (Zander et al., 1999). However, 
factors such as surface area or water 
volume also influence community com- 
position and structure (Mahon and 
Mahon, 1994). For instance, larger, 
deeper pools allow the permanency of 
more stenotopic species (Gibson and 
Yoshiyama, 1999). Therefore, the dis- 
tribution of fishes is to some extent 
“azonal” (i.e., pool height within the 
intertidal zone is not necessarily 
the single or even the main deter- 
minant for fish distribution) because 
the occurrence of each species is more 
dependent upon pool characteristics 
than upon the vertical position of the 
pool on the rocky shore (Zander et al., 
1999). On the other hand, the syner- 
gistic effects between pool morphom- 
etry and pool isolation have obscured 
the distinction of their respective 
contributions to the spatial distribu- 
tion of fishes (Bennett and Griffiths, 
1984). As a consequence, the influ- 
ence of ecological aspects like compe- 
tition, predation, or niche availability 
on shaping tidepool fish distributions 
may thus far be inadequately evalu- 
ated (Faria and Almada, 2001, 2006; 
Arakaki and Tokeshi, 2010; Rojas and 
Ojeda, 2010). 
In flat reefs, there are no signifi- 
cant differences in vertical position 
of pools and in wave impact on pools 
and, consequentially, the duration of 
isolation from the sea is similar for all 
pools (e.g., Mahon and Mahon, 1994). 
In such a situation, pool morphometry 
probably is the most influential fac- 
tor on the distribution of fishes. The 
relative evenness of physicochemical 
factors among pools enables a stan- 
dardization of the species filter (i.e., 
one or more environmental factors 
that impede species occurrence), and 
differences among pools will be due 
more to differences in the availability 
of resources (e.g., food, mates, space, 
protection) and microhabitat. How- 
ever, despite offering an opportunity 
to study these effects without overly 
confounding factors, flat reef areas 
have been little studied in respect to 
the spatial distribution of their inter- 
tidal fishes (Mahon and Mahon, 1994; 
Zander et al., 1999). Thus, how pool 
size and shape (depth and volume) 
and substrate complexity interact 
to affect community composition re- 
mains poorly understood. Therefore, 
our objectives were to investigate the 
effects of the physicochemical setting 
(temperature and salinity) and mor- 
phometric characteristics of pools on 
the structure of fish communities on 
a flat reef, without the interactive 
effects caused by differences in the 
duration of isolation of the rockpools. 
In comparison with a “classic” rocky 
shore (with varying duration of isola- 
