Masuda et al.: Fish assemblages associated with three types of artificial reefs 
165 
was conducted according to the method of San- 
tos et al. (2005) and Friedlander et al. (2007). 
The estimated average length of each species for 
each sample was converted to mass by using the 
length-mass relationship 
M=aSL 6 , 
where a and b - constants for allometric growth; 
SL = standard length; and 
M = mass. 
Length-mass parameters were obtained from Fish- 
Base (www.fishbase.org, accessed on July 2008) 
and calibration was based on our own samples. 
The number of fish species (species richness), 
total number of fish individuals (abundance), to- 
tal fish biomass, and number of individuals of 
each fish species associated with each type of AR 
were compared among the three types of ARs by 
repeated measures ANOVA followed by Tukey’s 
HSD test. Data for the number of fish individuals 
and their biomass were log (x+l) transformed to 
obtain homoscedasticity. 
Estimation of the impact of AR deployment 
on fish abundance in the adjacent area 
Fish assemblages in the area surrounding the ARs 
were compared before and after AR deployment. 
Data from the twice monthly visual censuses in 
each area were used for this purpose (Masuda, 
2008; Fig. 2). The number and size of fish of each spe- 
cies found along three 400-m 2 belt transects have been 
recorded twice a month since 1 January 2002. One 
transect was close to the location of the ARs that we 
deployed in the present study (transect 1), and the other 
two were relatively distant (transects 2 and 3). There- 
fore, species richness and fish abundance in transect 1 
would decline after AR deployment if fish were simply 
attracted from the adjacent natural reef to these ARs. 
Each of the three transects included areas of rocky reef, 
live oysters and their dead shells, a sandy or muddy 
silt bottom, and an artificial vertical structure made 
of concrete blocks that had been deployed more than 
20 years earlier. The size (length x width x height) of 
the concrete structures along transects 1, 2, and 3 were 
0. 5x3x2. 4 m, 1. 8x3x1 m, and 2. 5x2. 5x2 m, respectively. 
Data from 23 May 2002 to 15 May 2004, and those from 
29 May 2004 to 8 May 2008 were used to compare the 
fish assemblages before and after deployment of the 
ARs. Analyses of covariance (ANCOVA) was used to 
compare species richness and fish abundance in each 
transect before and after deploying the wooden or PVC 
ARs, and bottom water temperature was used as a 
covariant because fish species richness and abundance 
increase almost linearly with the increase of bottom 
water temperature in this habitat (Masuda, 2008). The 
number of individuals of each species was also compared 
by ANCOVA before and after deployment of the ARs. All 
Table 1 
The mean (± standard error) number of species, individuals, and 
estimated biomass of fish attracted to the cedar, broadleaf, and 
PVC artificial reefs over the entire observation period (2004-08) 
and for each of the four years (n = 3 ARs per type). Different let- 
ters represent significant differences among AR types (P<0.01, 
Tukey’s HSD test). 
Cedar ARs 
Broadleaf ARs 
PVC ARs 
No. of species 
Whole period 
4.14 ±0.138° 
3.49 ±0.107 6 
3.00 
±0.113° 
1 st year 
5.14 ±0.332° 
3.44 ±0.245 6 
2.51 
±0.201° 
2 nd year 
4.10±0.289° 
3.49 ±0.244 h 
2.83 
±0.232° 
3 rd year 
3.93 ±0.226° 
3.63±0.225° 6 
3.28 
±0.217 6 
4 th year 
3.38 ±0.196 
3.40 ±0.193 
3.38 
±0.195 
No. of individuals 
Whole period 
40.7 ±4.43° 
27.9 ±2.88 fe 
20.3 
±2.18° 
1 st year 
84.5 ±12.9° 
36.8 ±5.86 h 
29.6 
±6.23° 
2 nd year 
24.1 ±5.00° 
28.0 ±5.88“ 
10.9 
±2.25 h 
3 rd year 
32.1 ±8.31° 
24.7 ±6.80 ft 
19.0 
±4.00 b 
4 th year 
22.0 ±4.59 
22.1 ±4.15 
21.9 
±3.82 
Fish biomass (grams) 
Whole period 284 ±34.7° 
143 ±19.1* 
157 
±40. 7 6 
1 st year 
498 ±89.8° 
113 ±24.4 ft 
243 
±157 6 
2 nd year 
222 ±51.6 
134 ±38.7 
89.1 
±19.3 
3 rd year 
310 ±82.0 
179 ±44.8 
141 
±28.4 
4 th year 
108 ±29.9 fc 
148 ±41.8 ft 
155 
±28.2° 
statistical analyses were conducted with the software 
JMP (vers. 5.0. 1J, SAS Institute, Inc., Cary, NC) with 
an alpha level of 0.01. 
Results 
Fish assemblages associated with the ARs 
Both species richness and fish abundance were high- 
est associated with the cedar ARs, intermediate with 
the broadleaf ARs, and lowest with the PVC ARs when 
compared over the entire sampling period (Table 1). 
These differences were significant among the three AR 
types in both of these measurements (repeated mea- 
sures ANOVA followed by Tukey’s HSD test: PcO.Ol). 
The greater effectiveness of the cedar ARs was promi- 
nent in the first year after deployment but decreased 
with time and became nonsignificant in the fourth 
year (Table 1; Fig. 3). Fish biomass was greatest in 
the cedar and PVC ARs in the first and fourth year, 
respectively, but did not differ significantly in the 
second and third years. 
A total of 62 fish species were observed in 96 dives 
on these nine ARs, among which six species were 
found most frequently in the cedar ARs, two in the 
broadleaf ARs, and two in the PVC ARs (Table 2). 
Five most commonly observed fish species in the ARs 
