Abstract
Fisheries managers frequently try to protect juveniles in order to preserve stocks. Juveniles can be protected by either implementing changes designed to avoid catching immature animals (e.g. increasing mesh size or altering fishing techniques) or protecting nursery grounds. To prevent the capture of immature animals, an estimate of size at maturity is required as well as a knowledge of both fishing methods and the exact location of the nursery grounds. Strong demand for juvenile mud crabs to stock aquaculture ponds has resulted in development of fisheries targeting crabs of all sizes from instar 1 to mature individuals. Using five different fishing methods, different stages in the life cycle of Scylla paramamosain were followed for a period of 16 months in an estuarine population in the Mekong Delta, Vietnam. Mangrove habitat utilisation begins when crabs settle out from the plankton at instar 1 [modal internal carapace width (ICW), 0.5 cm] amongst the pneumatophores at the mangrove fringe. Increasingly larger crabs were found deeper into the mangrove but they were still living on the surface (modal ICW size class, 1.5 cm). As their size increases, the crabs either dig burrows (modal ICW size class, 4.5 cm) or they live in the sub-tidal zone, migrating into the mangrove with each tide to feed (modal ICW size class, 4.5 cm). Larger crabs were caught offshore (modal ICW size class, 12.5 cm) where females accounted for 60% of the catch although of these, only 63% were mature. Recruitment of early instars was continuous but peaked in December to February. Subsequent peaks in the catch rates of larger size classes indicated the development of a single cohort with an estimated growth rate of 2.0 cm ICW per month. On the basis of abdominal width, females were estimated to mature at 10.2 cm ICW although at 9.7 cm ICW, 50% of females had disengaged abdomens. Abdominal disengagement occurred in males at the slightly smaller size of 9.1 cm ICW. Allometric relationships between chela height and carapace width suggested 50% of males acquire mature chelae at 10.2 cm ICW. These results demonstrate the close linkage between early life stages of S. paramamosain and certain specific niches within mangrove habitats, with the main adult population found to be living sub-tidally at some distance from the mouth of the estuary. The study also highlights the special importance of the mangrove fringe, the border between the mangrove forest and the sea, an area which is particularly vulnerable to physical and anthropogenic impacts.
Similar content being viewed by others
References
Angell CA (1992) Summary of the proceedings of the seminar on mud crab culture and trade. In: Angell CA (ed) Seminar on mud crab culture and trade, Bay of Bengal programe. BOBP Report, Madras, pp 1–2
Arriola FJ (1940) A preliminary study of the life history of Scylla serrata (Forskal). Phil J Sci 73:437–458
Barnes DKA, Dulvy NK, Priestly SH, Darwall WRT, Choisel V, Whittington M (2002) Fishery characteristics and abundance estimates of the mangrove crab Scylla serrata in southern Tanzania and northern Mozambique. S Afr J Mar Sci/S-Afr Tydskr Seewet 24:19–25
Beck MW, Heck KL, Able KW, Childers DL, Eggleston DB, Gillanders BM, Halpern B, Hays CG, Hoshino K, Minello TJ, Orth RJ, Sheridan PF, Weinstein MR (2001) The identification, conservation, and management of estuarine and marine nurseries for fish and invertebrates. Bioscience 51:633–641
Bramslev J (2004) Cumulative impact analysis and nam theun 2 contributions. Annex 2: hydrology report. http://www.adb.org/Documents/Studies/Cumulative-Impact-Analysis
Christensen SM, Macintosh DJ, Phuong NT (2004) Pond production of the mud crabs Scylla paramamosain (Estampador) and S. olivacea (Herbst) in the Mekong Delta, Vietnam, using two different supplementary diets. Aqua Res 35:1013–1024
Conan GY, Comeau M (1986) Functional maturity and terminal molt of male snow crab, Chionoecetes opilio. Can J Fish Aquat Sci 43:1710–1719
Estampador EP (1949) Studies on Scylla (Crustacea: Portunidae). I. A revision of the genus. Phil J Sci 78:95–108
Fielder DR, Eales AJ (1972) Observations on courtship, mating and sexual maturity in Portunus pelagicus (L, 1766). J Nat Hist 6:273–277
Fielder DF, Heasman MP (1999) Workshop 2. Larval rearing and nursery production. In: Keenan C, Blackshaw A (eds) Mud crab aquaculture and biology. ACIAR Proceedings, Darwin, Australia, 21–24 April 1997, pp 209–214
Forbes AT, Hay DG (1988) Effects of a major cyclone on the abundance and larval recruitment of the portunid crab Scylla serrata (Forskal) in the St Lucia Estuary, Natal, South Africa. S Afr J Mar Sci/S-Afr Tydskr Seewet 7:219–225
Hartnoll RG (1982) Growth. In: Abele LG (ed) Emybrology, morphology and genetics. Academic Press, New York, pp 111–196
Hill BJ (1978) Activity, track and speed of movement of the crab Scylla serrata in an Estuary. Mar Biol 47:135–141
Hill BJ, Williams MJ, Dutton P (1982) Distribution of juvenile, sub-adult and adult scylla-serrata (Crustacea, Portunidae) on tidal flats in Australia. Marine Biology 69(1):117–120
Hill BJ (1994) Offshore Spawning by the Portunid Crab Scylla serrata (Crustacea, Decapoda). Mar Biol 120:379–384
Horwood JW, Nichols JH, Milligan S (1998) Evaluation of closed areas for fish stock conservation. J Appl Ecol 35:893–903
Houde E, Roberts S (2001) Marine protected areas and fishery management in the coastal ocean: A US perspective ICES CM 2001 Theme session; Sustainable Development and Conservation of Natural Resources of the Coastal Zone. International Council for the Exploration of the Sea, Oslo, Norway
Keenan C (1999) Aquaculture of the Mud Crab, Genus Scylla—past, present and future. In: Keenan C, Blackshaw A (eds) Mud crab aquaculture and biology. ACIAR Proceedings, Dawin, Australia, 21–24 April 1997
Keenan CP, Davie PJF, Mann DL (1998) A revision of the genus Scylla de Haan, 1833 (Crustacea: Decapoda: Brachyura: Portunidae). Raffles B Zool 46:217–245
Kite G (2001) Modelling the Mekong: hydrological simulation for environmental impact studies. J Hydrol (Amst) 253:1–13
Knuckey IA (1996) Maturity in male mud crabs, Scylla serrata, and the use of mating scars as a functional indicator. J Crustacean Biol 16:487–495
Le Vay L (2001) Ecology and management of mud crabs, Scylla spp. Asian Fish Sci 14:101–111
Le Vay L, Ngoc Ut V, Jones DA (2001) Seasonal abundance and recruitment in an estuarine population of mud crabs, Scylla paramamosain, in the Mekong Delta, Vietnam. Hydrobiologia 449:231–239
de Lestang S, Hall NG, Potter IC (2003) Reproductive biology of the blue swimmer crab (Portunus pelagicus, Decapoda: Portunidae) in five bodies of water on the west coast of Australia. Fish Bull 101:745–757
Macintosh DJ, Overton JL, Thu HVT (2002) Confirmation of two common mud crab species (genus Scylla) in the mangrove ecosystem of the Mekong Delta, Vietnam. J Shellfish Res 21:259–265
Macnae W (1968) A general account of the fauna and flora of mangrove swamps and forests in the Indo-West-Pacific region. Adv Mar Biol 6:73–270
Moser SM, Macintosh DJ (2001) Diurnal and lunar patterns of larval recruitment of Brachyura into a mangrove estuary system in Ranong Province, Thailand. Mar Biol 138:827–841
Moser SM, Macintosh DJ, Prinpanapong S, Tongdee N (2002) Estimates of growth of the mud crab Scylla olivacea in the Ranong mangrove ecosystem, Thailand, based on a tagging and recapture study. Mar Freshw Res 53:1083–1089
Odum EP (1971) Fundamentals of ecology. Saunders, Philadelphia
Overton JL, Macintosh DJ (2002) Estimated size at sexual maturity for female mud crabs (Genus Scylla) from two sympatric species within the Ban Don Bay, Thailand. J Crust Biol 22:790–797
Robertson WD, Kruger A (1994) Size at maturity, mating and spawning in the portunid crab Scylla serrata (Forskal) in Natal, South-Africa. Est Coast Shelf Sci 39:185–200
Ryan EP (1967) The morphometry of sexually mature instars in the crab, Portunus sanguinolentus (Herbst) (Brachyura: Portunidae). Mar Biol Ass India Symp Ser 2:715–723
Stanners D, Bourdeau P (1995) Europe’s environment. The Dobris assessment. Office for official publications of the European Community, pp 676
Trino AT, Millamena OM, Keenan C (1999) Commercial evaluation of monosex pond culture of the mud crab Scylla species at three stocking densities in the Philippines. Aquaculture 174:109–118
Ut VN (2002) Assessment of the feasibility of stock enhancement of mud crabs, Scylla paramamosain, in the Mekong Delta, Vietnam. PhD, School of Ocean Sciences
Watson J (1970) Maturity, mating, and egg laying in spider crab, Chionoecetes opilio. J Fish Res Board Can 27:1607–1616
Acknowledgements
This research was supported by the European Commission, INCO-DEV contract no. ICA4-CT-2001-10022. We would like to thank the anonymous reviewers for their valuable comments. This research complied with current Vietnamese law.
Author information
Authors and Affiliations
Corresponding author
Additional information
Communicated by J.P. Thorpe, Port Erin
Rights and permissions
About this article
Cite this article
Walton, M.E., Le Vay, L., Truong, L.M. et al. Significance of mangrove–mudflat boundaries as nursery grounds for the mud crab, Scylla paramamosain . Mar Biol 149, 1199–1207 (2006). https://doi.org/10.1007/s00227-006-0267-7
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00227-006-0267-7