Effects of tank colour on larval survival and development of mud crab Scylla serrata (Forska ˚l) Abed Golam Rabbani & Chaoshu Zeng Tropical Crustacean Aquaculture Research Group, School of Marine Biology and Aquaculture, James Cook University, Queensland, Australia Correspondence: C Zeng,Tropical Crustacean Aquaculture Research Group, School of Marine Biology and Aquaculture, James Cook University,Townsville, Queensland 4811, Australia. E-mail: chaoshu.zeng@jcu.edu.au Abstract Hatchery culture of mud crabs has not yet achieved commercial viability despite decades of research e¡orts. Further research is therefore needed to better understand larval culture requirements of the crab. Based on anecdotal observations, an experiment was carried out to test whether the background colour of the culture vessel a¡ected larval culture success. Newly hatched larvae of Scylla serrata were reared in culture vessels of ¢ve colours, i.e., black, dark green, maroon, sky blue and white. Larval survival and development were monitored daily until all of them either moulted to the ¢rst crab stage or died. The results showed clear e¡ects of background colour on larval survival. A general tendency of higher larval survival in dar- ker-coloured backgrounds was evident. In particular, overall zoeal survival for larvae reared in black vessels was signi¢cantly higher than those reared in white ones. Background colour also appeared to a¡ect larval development. Larvae reared in darker backgrounds generally had shorter development times and more synchronized moulting. A signi¢cant delay in zoeal development was observed in larvae reared in white vessels. Dark backgrounds possibly facilitated more e⁄cient feeding, reduced settlement of larvae at the bottom of the vessels as well as mini- mized stress. This result appears to be the ¢rst to de- monstrate that background colour can signi¢cantly a¡ect larval survival and development of a crusta- cean species. Keywords: mud crab, Scylla serrata, background colour, larval survival, larval development Introduction Mud crabs of the genus Scylla are commercially im- portant in many Indo-Paci¢c countries (Cowan 1985; Keenan 1999). They are also known as man- grove crabs or king crabs. Mud crabs are found in tro- pical, subtropical and warm temperate areas where they inhabit brackish and saltwater estuaries or mangrove forest. Because of their large size, high meat yield and delicate £avour, mud crabs are a sea- food delicacy. They are in great demand wherever they occur (Keenan 1999). Based on genetic analysis, Keenan, Davie and Mann (1998) recently identi¢ed four species from the genus Scylla and revised their taxonomic nomenclature as S. serrata, S. olivacea, S. paramamosain and S. tranquebarica. Among the four mud crab species, S. serrata grows the largest and is the most widely distributed species (Keenan et al . 1998). Mud crab farming is widely regarded as a viable al- ternative to the disease-plagued prawn farming in- dustry in the Indo-Paci¢c region. As a consequence, there is growing interest in aquaculture of the spe- cies in the region (Keenan 1999; Sheen & Wu 1999; Trin ì o & Rodriguez 2002). While mud crab aquacul- ture in the region has already contributed signi¢- cantly to total mud crab production (Anonymous 1999); current farming practice relies almost entirely on juvenile crabs caught from the natural environ- ment (Fortes 1999; Keenan 1999). Apparently, such a practice is unsustainable and has seriously hindered further expansion of the industry (Keenan1999). As wild mud crab seed supply is limited and often £uctuates considerably, it is clear that sustainable growth of the mud crab farming industry is only Aquaculture Research, 2005, 36, 1112^1119 doi: 10.1111/j.1365-2109.2005.01328.x 1112 r 2005 Blackwell Publishing Ltd