Masuda et al.: Fish assemblages associated with three types of artificial reefs 
163 
The recent trend for ARs in Japan has shifted 
from concrete to wooden construction. This has 
been partly due to funding shortages, but also 
because fishermen have found that wooden ARs 
attract fish more rapidly than those made of con- 
crete or steel. Indeed, most coastal prefectures 
in Japan deploy wooden ARs with or without 
governmental subsidies under the supervision 
of local fishermen’s cooperatives. The materials 
and shape of wooden ARs differ depending on 
each fishery cooperative. As much as 70% of the 
land area in Japan is forested, half of which is 
plantation forests of conifers, such as Japanese 
cedar (Cryptomeria japonica) and hinoki cypress 
( Chamaecyparis obtusa). Although these forests 
require occasional thinning, many of them lack 
such maintenance because of the decline in the 
market price of timber. Therefore, the construc- 
tion of wooden ARs also has the socioeconomic 
potential to stimulate the demand for forestry 
materials. 
The primary goal of the present study was to 
confirm the efficacy of wooden ARs, especially 
those made of cedar tree logs as fish habitat. For 
this purpose, fish assemblages associated with 
ARs made from cedar trees were compared to 
those made from broadleaf trees and those made 
with polyvinyl chloride (PVC) pipes. There is a 
debate whether ARs merely attract fishes from adjacent 
areas or whether they do improve fishery productivity 
(Grossman et al., 1997; Pickering and Whitmarsh, 
1997). We therefore tested the possibility that ARs at- 
tract fishes from adjacent areas and thus concentrate 
fish abundance at the ARs, rather than fish abundance 
is spread over the fishing ground as a whole. A visual 
census had been conducted twice a month for more 
than two years before the deployment of these ARs in 
adjacent areas; hence the fish fauna was compared in 
the area before and after the deployment of ARs. 
Materials and methods 
Deployment and visual census of artificial reefs 
Three types of ARs were prepared. The design of the ARs 
was modified from that designed by the Atake Forestry 
Association, Yamaguchi, Japan (http://www.geocities.jp/ 
abu_kikori/katsudou/gyosyou/gyosyou2.html, accessed 
on December 2003; also see Fig. 1). The first type of AR 
(cedar AR) was constructed of 16 log sections (1.5 m long, 
6.9-18.4 cm diameter) of Japanese cedar ( Cryptomeria 
japonica) arranged in a parallel cross formation. Each 
corner was tied with rope and fixed with a stainless 
steel rod. Diagonal wires helped maintain the rectan- 
gular shape. The second type of AR (broadleaf AR) was 
constructed from six species of broadleaf trees harvested 
from the Ashiu Forest Research Station, Kyoto Univer- 
sity, and assembled with the same dimensions as those 
used for the cedar AR. The broadleaf tree species used 
were Japanese cherry birch ( Betula grossa), hornbeam 
( Carpinus laxiflora), Japanese beech ( Fagus crenata), 
Chinese chestnut (Castanea crenata), redvein maple 
( Acer rufinerve), and macropoda holly ( Ilex macropoda). 
The diameter of broadleaf and cedar logs ranged from 
7.5 to 19.2 cm. The third type of AR (PVC AR) was made 
of hollow PVC pipes (11.8 cm diameter, 3 mm thickness) 
and was assembled in the same manner as that used for 
the other two types of ARs. 
These three types of ARs were constructed in trip- 
licate and deployed at a depth of 8 m off the Maizuru 
Fisheries Research Station (MFRS), Nagahama, Maiz- 
uru, Kyoto (35°29'N lat. and 135°22'E long.) on 21 May 
2004 (Fig. 2). The shore in this area is a concrete bank 
and its subtidal zone consists of natural rocks, concrete 
blocks, both partly covered by live oyster ( Crassostrea 
gigas) and their dead shells, and sandy silt with some 
macroalgal vegetation. The substrate in the research 
area consisted of muddy silt with no macroalgae veg- 
etation. Each AR was sunk with 240 kg of sand bags 
(60 kg attached to each corner of the AR). ARs were 
set 15 m apart. 
Twice monthly visual censuses of fish assemblages as- 
sociated with each AR were conducted for four consecu- 
tive years after AR deployment. All census observations 
were made by the first author with SCUBA equipment. 
The area in and around each AR was observed for about 
three minutes and the species, size, and number of 
fish were recorded. A census commenced from one of 
the lateral sides of an AR and extended out to about 
1 m from each side. The observer then swam around 
and above the AR, and the fish inside the AR were 
