Effects of shore sedimentation to tachypleus gigas (Müller, 1785) spawning activity from Malaysian waters

Ripraps, land reclamation and fishing jetty renovation were perturbing Balok Beach shores between the years 2011 and 2013 and visible impacts were scaled using horseshoe crab spawning yields. Initially, placement of ripraps at Balok Beach effectively reduced erosion and created a suitable spawning ground for the horseshoe crab, Tachypleus gigas. However sediments begun to gather on the beach onward year 2012 which increased shore elevation and caused complete shore surface transition into fine sand properties. This reduced sediment compaction and made Balok Beach less favourable for horseshoe crab spawning. During the dry Southwest monsoon, Balok River estuary retains more dense saline water which assists with sediment circulation at the river mouth section. Comparatively, the less dense freshwater during the wet Northeast monsoon channels sediments shoreward. Circa-tidal action that takes place at Balok River sorts the shore sediments to produce an elevated and steep beach. Hence, the reduced number of T. gigas nests and eggs retrieved during year 2013 (after comparing with yield of year 2012) at Balok Beach are indicating impacts from anthropic-caused sedimentation. Models need to be constructed and associated with T. gigas spawning-migration to fully understand sediment transport especially at coastal areas that need or are undergoing nourishment

Citizen science frontiers horseshoe crab population regain at their spawning beach in East Peninsular Malaysia

Carcinoscorpius rotundicauda and Tachypleus gigas may co-exist and share common spawning grounds elsewhere but at Balok (East Coast of Peninsular Malaysia), C. rotundicauda is an understudied species. Neglected as research candidate because of inaccessible spawning grounds, smaller size and less commercial value than T. gigas and also, difficulty to attain from the wild has made C. rotundicauda population status remaining unidentified at Balok. This standpoint drove the present attempt because anthropic activities like structure placement and mining are point-source for runoffs that load sediments into Balok River. While erosion-accretion events have altered Balok River width, the shore sediments in Balok Beach were transitioned between medium-fine and fine sand between years 2012 and 2016. Eventually by year 2016, the C. rotundicauda were depositing 5117 eggs in 91 nests from 200 to 1000 m range along this corridor facing South China Sea. From this yield, C. rotundicauda released 2880 eggs in 56 nests during the Southwest monsoon, 1254 eggs in 19 nests during the Northeast monsoon and 983 eggs in 16 nests during the Inter-monsoon seasons. Though female C. rotundicauda opted to lay their eggs in shallow burrows at lower shorelines, the absence of erosion and substantial silt and clay (>20%) deposition facilitates C. rotundicauda embryogenesis with brief periods of temperature and salinity shocks during day-time falling tides. This encourages C. rotundicauda to emerge with increasing abundance and carry out bi-monthly spawning at Balok Beach. In short, shore restoration initiatives like systematic boat docking, proper disposal of nets and waste and, periodic fish-catching operations were effectively led by the Balok fisher citizen scientist. This successful community joint-cooperation proves that citizen-led caretaking of degraded beaches offers marine life protection and are practical for coastal area management especially at areas where other oviparous animals such as turtles and crocodiles are harboured

Carcinoscorpius rotundicauda (Latreille, 1802) population status and spawning behaviour at Pendas coast, Peninsular Malaysia

The present study evaluates impacts from seasonal monsoons and lunar phases on the spawning activity of the mangrove horseshoe crab, Carcinoscorpius rotundicauda at Pendas (Sites 1–3) in State Johor, Peninsular Malaysia. The biological (no. of crabs and nests/eggs) observations indicated that Pendas is an active spawning ground for C. rotundicauda throughout the year. Higher egg yield was observed for Southwest monsoon (2918 eggs in 55 nests), followed by Northeast (2331 eggs in 48 nests) and Inter-monsoon (1253 eggs in 20 nests) periods. In all seasons, the full moon conditions favoured more number of eggs than to the new moon. Besides the availability of adult crabs in all three sampling sites, the spawning took place only at Site-1 due to its location (mini sandbar) being sheltered away from the impact of Johor Strait waters, underground (domestic) discharge point and pioneer mangroves like Sonneratia and Avicennia spp. nearby. In contrast, Sites 2 and 3 are open to the seawater current and its surface sediment is covered by broken seashells/pebbles and/or dense A. alba pneumatophore roots. Among the environmental (water quality and sediment) parameters tested, except sand, silt and clay, the rest (e.g. temperature, pH, salinity, total organic carbon, etc.) didn't show any strong correlation with the spawning behaviour of C. rotundicauda. The ongoing physical infrastructure developments on housing and property constructions in the vicinity are likely to pose a threat to the spawning ground of C. rotundicauda and thus requires a serious attention for its conservation and management. Keywords: Mangrove horseshoe crab, Spawning ecology, Seasonal impact, Local topography, Johor strait, Malaysi

Horseshoe crab bio-ecological data from Balok, East Coast Peninsular Malaysia

The data available in this repository were gathered from Balok, the only most productive spawning site for horseshoe crabs Tachypleus gigas and Carcinoscorpius rotundicauda in East Coast of Peninsular Malaysia. The mangrove horseshoe crab, C. rotundicauda population and spawning data are available in the first table. The horseshoe crabs were retrieved from Balok River using 11.43 cm mesh size gill nets installed at the river mouth, the confluence and last meander. The arthropods were inspected for damage, abnormality and growth before their release into Balok River, particularly at the site of capture. Sediment samples were retrieved at their spawning grounds to ascertain sediment composition and size classifications which were also processed using Logarithmic Method of Moments. Water parameters like temperature, pH and salinity were also investigated during year 2016. All these information are compiled into the second table and arranged according to the period of data availability. The horseshoe crab catch data of years 2012, 2013, 2014, 2015 and 2016 were made available by artisanal fisher and compiled in the third and fourth table for inter-species comparison

Genetic diversity of Carcinoscorpius rotundicauda in Peninsular Malaysia

info:eu-repo/semantics/publishe

Mangrove horseshoe crab (Carcinoscorpius rotundicauda Latreille, 1802) populations reveal genetic break in Strait of Malacca, with connectivity along southern coasts of Peninsular Malaysia

The mangrove horseshoe crab, Carcinoscorpius rotundicauda, has divergent populations between the east and west coasts of Peninsular Malaysia, with the southern coast acting as a land barrier. The actual position of such a genetic break along Peninsular Malaysia as well as the connectivity status of the southernmost C. rotundicauda populations with east and west coast populations remain unexplored, however. The aim was to investigate the genetic diversity and structure of C. rotundicauda populations from the west (Kuala Sepetang in State Perak), east (Balok in State Pahang), and southern (Pendas in State Johor) coasts of Peninsular Malaysia. Haemolymph samples from adult C. rotundicauda specimens (n = 152) and eggs from their freshly deposited nests (n = 190) were collected monthly (from January 2016 to January 2017) for the sequencing of mitochondrial cytochrome c oxidase subunit I (COI). Gene isolates of C. rotundicauda from the present study were compared with National Center for Biotechnology Information (NCBI) GenBank sequences to cover most of the range of the species in Asia. A neighbour-joining tree strongly supported two clades, separating the west-coast populations from the south- and east-coast populations, with further substructure patterns. Both haplotype network and barrier analyses revealed a genetic break within the Strait of Malacca instead of the southern tip of Peninsular Malaysia. The southernmost samples from the Strait of Johor formed a haplotypic diverse gene pool that appeared only as a subclade of the eastern populations. In a detailed haplotype network of 347 individuals, individuals with similar COI sequences indicate connectivity between C. rotundicauda on the east and C. rotundicauda on south and south west of Peninsular Malaysia. Overall, the genetic break between C. rotundicauda populations is better explained by the convergent ocean currents and available mangrove habitats on the west coast (i.e. Strait of Malacca), rather than the point of the Malay Peninsula acting as a land barrier alone.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Status of the undisturbed mangroves at Brunei Bay, East Malaysia: A preliminary assessment based on remote sensing and ground-truth observations

Brunei Bay, which receives freshwater discharge from four major rivers, namely Limbang, Sundar, Weston and Menumbok, hosts a luxuriant mangrove cover in East Malaysia. However, this relatively undisturbed mangrove forest has been less scientifically explored, especially in terms of vegetation structure, ecosystem services and functioning, and land-use/cover changes. In the present study, mangrove areal extent together with species composition and distribution at the four notified estuaries was evaluated through remote sensing (Advanced Land Observation Satellite-ALOS) and ground-truth (Point-Centred Quarter Method-PCQM) observations. As of 2010, the total mangrove cover was found to be ca. 35,183.74 ha, of which Weston and Menumbok occupied more than two-folds (58%), followed by Sundar (27%) and Limbang (15%). The medium resolution ALOS data were efficient for mapping dominant mangrove species such as Nypa fruticans, Rhizophora apiculata, Sonneratia caseolaris, S. alba and Xylocarpus granatum in the vicinity (accuracy: 80%). The PCQM estimates found a higher basal area at Limbang and Menumbok-suggestive of more mature vegetation, compared to Sundar and Weston. Mangrove stand structural complexity (derived from the complexity index) was also high in the order of Limbang > Menumbok > Sundar > Weston and supporting the perspective of less/undisturbed vegetation at two former locations. Both remote sensing and ground-truth observations have complementarily represented the distribution of Sonneratia spp. as pioneer vegetation at shallow river mouths, N. fruticans in the areas of strong freshwater discharge, R. apiculata in the areas of strong neritic incursion and X. granatum at interior/elevated grounds. The results from this study would be able to serve as strong baseline data for future mangrove investigations at Brunei Bay, including for monitoring and management purposes locally at present.SCOPUS: ar.jinfo:eu-repo/semantics/publishe