Zoological Studies

Vol. 51 No. 6, 2012

Population Structure and Reproduction of the Mysid Shrimp Acanthomysis thailandica (Crustacea: Mysidae) in a Tropical Mangrove Estuary, Malaysia

Tueanta Ramarn1,3, Ving-Ching Chong1,2,*, and Yukio Hanamura4

1Institute of Biological Sciences, University of Malaya, Kuala Lumpur 50603, Malaysia
2Institute of Ocean and Earth Science,University of Malaya, Kuala Lumpur 50603, Malaysia
3Department of Biology, Faculty of Science, Thaksin University, Phattalung Campus, Phattalung 93110, Thailand
4Japan International Research Center for Agricultural Sciences, Owashi 1-1, Tsukuba 350-8686, Japan

Tueanta Ramarn, Ving-Ching Chong, and Yukio Hanamura (2012) The mysid shrimp Acanthomysis thailandica Murano, 1988 in the Matang mangrove estuary showed large spatial and temporal variations in population density.  Large numbers occurred on the mudflat where the mean salinity was 25 ppt, but rapidly declined towards the upper estuary (14 km upstream) where the salinity fell to 15 ppt.  Mysids were present year-round and exhibited marked monthly variations in abundance, with modal peaks in May, Sept., and Dec. 2009 and Apr. 2010 in the mudflat area.  All developmental stages were observed, except juveniles which were absent from the middle to upper estuary.  Females predominated over males and matured at a smaller size.  Juveniles and empty (= post-spawning) females comprised the largest groups (at about 17% for each stage) of the population on the mudflat suggesting that the mudflat serves as the main spawning and nursery ground.  Brooding females occurred together with juveniles in all monthly samples, indicating that reproduction was year round.  Brood size was independent of female body length, and ranged 5-25 embryos per brood.  Mean lengths of eggs (0.26 0.03 mm), and eyeless (0.58 0.06 mm) and eyed larvae (0.73 0.10 mm) were also independent of total length.

Key words: Reproductive biology, Spatial and temporal abundance, Developmental stages, Mudflat area, Crustacea.

*Correspondence: Tel: 603-79674220.  Fax: 603-79674178.  Present address: National Research Institute of Fisheries Science, Fisheries Research Agency, Fuku-ura-2-12-4, Kanazawa-ku, Yokohama 236-8648, Japan.  E-mail:chong@um.edu.my