514 
Fishery Bulletin 99(3) 
when habitats have little structural complexity (Dittel et 
al., 1995; Hines and Ruiz, 1995). The swash zone is prob- 
ably difficult for larger predators to penetrate and they 
risk being stranded. In addition, birds that exploit the 
swash zone are less active at night (Brown and McLach- 
lan, 1990). 
Softshell and premolt crabs were not collected in the 
swash zone; it appears that this zone may not be a molt- 
ing ground owing to its dynamic characteristics. However, 
most diurnal and adult crabs in the samples were paper- 
shell crabs, which are also vulnerable to predation; the 
swash zone, therefore, may be important as a refuge for 
postmolt crabs. 
In our study, juvenile and immature crabs dominated 
the population of O. punctatus in the swash zone during 
late summer. From the size of the crabs, these were first- 
year crabs born in the previous winter or spring, and 
therefore their occurrence in the swash zone may be lim- 
ited to the summer and fall, when these juvenile and im- 
mature crabs appear (Sasaki and Kawasaki, 1980). A simi- 
lar seasonal occurrence of juvenile O. ocellatus from July 
to October on exposed sandy beaches of the mid-Atlantic 
Coast of the United States has been reported in an inshore 
area (McDermott, 1983). The occurrence and behavior of 
O. punctatus in the swash zone suggest that this habitat 
is important as a feeding ground and a refuge from preda- 
tion. Intertidal sand-burrowing peracarids, the major diet 
items of O. punctatus, also consume particulate organic 
matter and organisms in the swash zone (Kamihira, 1992; 
Takahashi and Kawaguchi, 1998). Thus by feeding in the 
swash zone, young O. puncta tus transport some of the sec- 
ondary production from the swash zone to the offshore ar- 
ea through their ontogenetic migration into deeper water. 
Acknowledgments 
We are grateful to Captain K. Morita and T. Kawamura, 
and K. Hirano of the Otsuchi Marine Research Center, 
Ocean Research Institute (ORI), for their help in field 
sampling. We would like to thank C. Vallet of Soka Uni- 
versity who translated the French articles. We also thank 
T. R Hirose of the Japan Sea National Fisheries Research 
Institute and the staff of the Plankton Laboratory of ORI 
for their help with fieldwork and for fruitful discussions 
during the course of our study. 
Literature cited 
Barshaw, D. E., and K. W. Able. 
1990. Deep burial as a refuge for lady crabs Ovalipes 
ocellatus : comparisons with blue crabs Callinectes sapi- 
dus. Mar. Ecol. Prog. Ser. 66:75-79. 
Brown, A. C., and A. McLachlan. 
1990. Ecology of sandy shores. Elsevier Science Publish- 
ing Company Inc., Amsterdam, 328 p. 
Caine, E. A. 
1974. Feeding of Ovalipes guadulpensis (Saussure) (Decap- 
oda: Brachyura: Portunidae), and morphological adapta- 
tions to a burrowing existence. Biol. Bull. 147:550-559. 
Dittel, A. I., A. H. Hines, G. M. Ruiz, and K. Ruffin. 
1995. Effects of shallow water refuge on behavior and den- 
sity-dependent mortality of juvenile blue crabs in Chesa- 
peake Bay. Bull. Mar.Sci. 57:902-916. 
Drach, P, and C. Tchernigovtzeff. 
1967. Sur la methode de determination des estades d’inter- 
mue et son application generale aux crustaces. Vie Milieu 
18:595-609. 
Du Preez, H. H. 
1983. The effects of temperature, season and activity on 
the respiration of the three spot swimming crab, Ovalipes 
punctatus. Comp. Biochem. Physiol. 75A:353-362. 
1984. Molluscan predation by Ovalipes punctatus (De Haan) 
(Crustacea: Brachyura: Portunidae). J. Exp. Mar. Biol. 
Ecol. 84:55-71. 
Du Preez, H. H., and A. McLachlan. 
1984. Biology of the three-spot swimming crab, Ovalipes 
punctatus (De Haan) II. Growth and molting. Crusta- 
ceana 47:113-120. 
Haefner, P. A. Jr. 
1985. Morphometry, respiration, diet and epizoites of Ovali- 
pes stephensoni Williams, 1976 (Decapoda, Brachyura). J. 
Crust. Biol. 5:658-672. 
Hines, A. H., and G. M. Ruiz. 
1995. Temporal variation in juvenile blue crab mortality: 
nearshore shallows and cannibalism in Chesapeake Bay. 
Bull. Mar. Sci. 57:884-901. 
Kamei, M. 
1976. Biology of Hiratsume-gani, Ovalipes punctatus (DE 
HAAN), in Sagami Bay. Jpn J Ecol 26:65-69. [In Jpn., 
Engl, abstr.] 
Kamihira, Y. 
1979. Ecological studies of macrofauna on a sandy beach of 
Hakodate, Japan II. On the distribution of peracarids and 
the factors influencing their distribution. Bull. Fac. Fish. 
Hokkaido Univ. 30:133-143. [In Jpn., Engl, abstr.] 
1992. Ecological studies of sand-burrowing amphipod Haus- 
torioides japonicus Dogielinotidae), on the south-western 
Hokkaido, Japan. Rev. Hakodate Univ., spec. no. 1:1-106. 
[In Jpn., Engl, abstr.] 
McDermott, J. J. 
1983. Food web in the surf zone of an exposed sandy beach 
along the mid-Atlantic Coast of the United States. In 
Sandy beaches as ecosystems (A. McLachlan and T. Eras- 
mus, eds.), p. 529-538. Junk Publishers, The Hague. 
McLachlan, A. 
1980. The definition of sandy beaches in relation to expo- 
sure: a simple rating system. S. Afr. J. Sci. 76:137-138. 
McLachlan. A., T. Wooldridge, and G. Van der Horst. 
1979. Tidal movements of the macrofauna on an exposed 
sandy beach in South Africa. J. Zool. Lond. 187:433-442. 
Mitchell, S. J. 
1984. Feeding of ling Genypterus blacodes (Bloch and Sch- 
neider) from New Zealand offshore fishing grounds. N. Z. 
J. Mar. Freshwater Res. 18:265-274. 
Moksnes, P-O, L. Pihl, and J. van Montfrans. 
1998. Predation on post larvae and juveniles of the shore 
crab Carcinus tnaenas: importance of shelter, size and can- 
nibalism. Mar. Ecol. Prog. Ser. 166:211-225. 
Norman, C. P, and M. B. Jones. 
1992. Influence of depth, season, and moult stage on the diet 
analysis of the velvet swimming crab Necora puber ( Branchy - 
ura, Portunidae). Estuar. Coast. Shelf Sci. 34:17-83. 
Ropes, J. W. 
1989. The food habits of five crab species at Pettaquamscutt 
River, Rhode Island. Fish. Bull. 87: 197-204. 
