Aquaculture Extension Manual No. 64

July 2017

Diseases of juvenile and adult mud crab Scylla spp.

in the Philippines

Eleonor A. TendenciaMa. Venuz C. Cabilitasan

Emilia Tobias-Quinitio

Southeast Asian Fisheries Development CenterAQUACULTURE DEPARTMENT

www.seafdec.org.ph

Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development

Department of Science and Technology

For commentsand inquiries

TelFax

EmailAQD website

SEAFDEC Aquaculture DepartmentTigbauan 5021, Iloilo, Philippines

(63-33) 330 7030 (63-33) 330 7031aqdchief@seafdec.org.phwww.seafdec.org.ph

Diseases of juvenile and adult mud crab Scylla spp. in the Philippines

July 2017

ISSN 0115-5369

Published and printed by:Southeast Asian Fisheries Development CenterAquaculture DepartmentTigbauan, Iloilo, Philippines

Copyright © 2017Southeast Asian Fisheries Development CenterAquaculture DepartmentTigbauan, Iloilo, Philippines

All rights reservedNo part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system,without permission in writing from the publisher

Tendencia, Eleonor A.

Diseases of juvenile and adult mud crab Scylla spp. in the Philippines / Eleonor A. Tendencia, Ma. Venuz C. Cabilitasan, Emilia Tobias-Quinitio. -- Tigbauan, Iloilo, Philippines : Aquaculture Department, Southeast Asian Fisheries Development Center, 2017, ©2017.

30 pages : color illustrations. -- (Aquaculture extension manual ; no. 64).ISSN: 0115-5369

1. Scylla (Crustacea) -- Diseases -- Philippines. 2. Crab culture -- Philippines. I. Cabilitasan, Ma. Venuz C., joint author. II. Tobias-Quinitio, Emilia, joint author. IV. SEAFDEC. Aquaculture Department.

SH 380.45 .P6 T46 2017 DLS2017-01

SEAFDEC Aquaculture Department Library Cataloging-in-Publication Data

FOREWORD

Mud crab has been polycultured with milkfish, tilapia and shrimps for the past several years and is now an important source of income for small scale coastal farmers not only in the Philippines but in the Southeast Asian region. Mud crab farming has been regarded as a lucrative business venture next to Penaeus monodon because crabs command a higher market price and are more resistant to disease than shrimp. However, mortalities due to diseases have been recently reported in cultured mud crab.

Issues concerning mud crab culture including diseases have been addressed by the Aquaculture Department of the Southeast Asian Fisheries Development Center (SEAFDEC/AQD) in collaboration with the Australian Center for International Agricultural Research (ACIAR), the European Union’s International Cooperation Project on Culture and Management of the Crab Scylla (INCO-CAMS), the Government of Japan-Trust Fund (GOJ-TF) and the Philippine Council for Agriculture, Aquaculture and Natural Resources Research and Development (PCAARRD) of the Department of Science and Technology (DOST). The latter designated SEAFDEC/AQD as the lead agency of the National Mud Crab S & T Program.

In 2004, a manual on the “Diseases in Farmed Mud Crabs Scylla spp.: Diagnosis, Prevention and Control” (by C. Lavilla-Pitogo and L. dela Pena) was published based on the outputs of studies funded by ACIAR, INCO-CAMS and GOJ-TF (I). It is with pleasure that we now present one of the fruits of our collaboration with PCAARRD-DOST which is an updated version of the manual published in 2004. It is hoped that this manual will assist farmers in the region to identify diseased mud crab, avoid risk factors and implement measures to prevent possible infestations and infections that may result in mortalities.

Chihaya Nakayasu, Ph.D.Acting ChiefSEAFDEC Aquaculture Department

CONTENTS

Foreword v Introduction 1Species of Mud Crab 2 Anatomy of Mud Crab 3 External Anatomy 3 Dorsal features 3 Ventral features 4 Internal Anatomy 5 Stages of Ovarian Maturation 5Environmental Requirements 6What is a Disease 7How Disease Develops 7Diseases of Mud Crab 9 Viral Diseases 9 White spot disease (WSD) 9 Infectious hypodermal and hematopoietic 10 necrosis (IHHN) Bacterial Diseases 11 Bacterial shell disease 11 Perforations on exoskeleton 12 Shell Fouling 13 Barnacles on exoskeleton 13 Bivalves on exoskeleton 14 Fouling microorganisms on the exoskeleton 15 Black deposits on the abdominal region 16 External Morphological Abnormalities 17 Discolorations of the Exoskeleton 18 Rust spot disease 18 Albinism 19 Bluish shell discoloration 20 Rusty discoloration 21 Red sternum disease 22 Internal Abnormalities 23 Black or brown gills 23 Stalked barnacles infestation 24 Black ovary 25 Others 26 Loss or regenerated appendages 26Acknowledgment 27References and Suggested Readings 28