First hatchery bred streaked spinefoot rabbitfish (Siganus javus) in Sabah, Malaysia

The present study aims to expand the market potential of the streaked spinefoot rabbitfish (Siganus javus) in Malaysia and provide consumers more choices of affordable protein source from aquaculture. Spawning hehavior of S.javus was recorded in a week after the new moon in October 2019 and January 2020. Spawning occurred between midnight and early morning, and the eggs hatched about 16 to 18 hours later. Throughout the incubation and larvae rearing period, water temperature was maintained at 30 to 31 °C. Water salinity, pH and DO were 31 to 33 ppt, 7.8 to 8, and 5 to 7 mg/l, respectively. Eggs diameter ranged from 0.550 to 0.603 mm. At 1 day after hatched (d AH), eyes of the larvae were formed but unpigmented and mouth structure was not developed. At 2 d AH, the pigmentation of eyes darkened, digestive tract formed, and anus and mouth opened. At 3 d AH, the lower jaw began to show movement, indicating that the ability of larvae to indulge in feeding. The buds of dorsal and ventral fins started to develop and elongate from 9 d AH and were covered with melanophores. At 25 d AH, the body of the larvae turned brownish and abdominal cavity was deeply pigmented, indicating the onset of metamorphosis. By the age of 30 d AH, the larvae completed development into juvenile stage. At 270 d AH, the juvenile reached maximum size of 21 cm in total length. This study was the first successful attempt at naturally spawning and hatchery rearing of S. javus into juvenile stage in the country. The development of a complete larval rearing protocol for S. javus could provide information of practical importance in hatchery breeding of other rabbitfish species.

An updated checklist of marine copepoda from Peninsular Malaysia with notes on their functional traits and distributional records

An up-to-date checklist of marine zooplankton copepods from the water of Peninsular Malaysia is presented, there are 235 species of copepods which consists of 89 genera and 44 families. Extensive list of bibliographical references with synonymy, detailed information on their functional groups, and distributional data are provided for each species. The checklist is based on taxonomic and ecological literature until 28 May 2020. Calanoida recorded the most diverse order with 101 species in total, followed by Harpacticoida with 70 species and 61 species from Cyclopoida. As for Canuelloida, Monstrilloida and Siphonostomatoida all recorded with 1 species respectively. There are 192 species of copepod recorded along the west coast (Malacca Strait) and 123 species on the east coast (South China Sea). Endemicity at species level attains 1% for the whole Peninsular Malaysian coast, with 2 genera restricted to the east coast (Kensakia parva and Brachiella malayensis) and one genus to the west coast (Labidocera jaafari). There are six dominant species that can be found along the coast of Peninsular Malaysia (Acartia erythraea, Acartia pacifica, Bestiolina similis, Euterpina acutifrons, Microsetella norvegica, Paracalanus aculeatus, Oithona nana, Oithona simplex and Temora discaudata).

Estimation of Partial Pressure of CO2 (pCO2) Around Mount Krakatau waters, Sunda Straits, Indonesia

The study aimed to develop the formula and validation the value of oceanic carbon dioxide partial pressure (pCO2sea) around Krakatau Waters in the Sunda Strait using parameters such as sea surface temperature (SST), sea surface salinity (SSS), and chlorophyll-a (Chl). Using observation data from different seasons (September 2017 and April 2018) The formulation of the empirical equation by using a multivariate polynomial regression method. The results of the study show that the empirical equation for estimating the pCO2 sea is as follows: : pCO2= -472.069+1044.043x log(SST) -435.897xlog(SSS) -5.03xlog (Chl).This formula can be applied for both seasons. The results of the analysis of the T-student test and p-value showed a strong relationship between the SST parameters and pCO2 with a correlation of 0.91 then followed by salinity with a correlation of -0.82. Whereas chlorophyll-a holds a weak proportion with a correlation of 0.32. The increase in SST accelerates the solubility of CO2 from atmosphere to the sea thereby increasing CO2 sea concentration and increasing pCO2 sea. While the increase in salinity and chlorophyll-a only gives a weak effect

Characteristics of surface currents in Manado Bay, North Sulawesi, Indonesia

Manado Bay is a complex waterway located in Manado City, North Sulawesi, Indonesia. It is an entry point for the Indonesia Trough-Flow, and its circulation is affected by the seasonal winds. Manado City has no debris net on its river estuaries. Therefore, marine debris can easily be carried away by the ocean currents and accumulate in the tourism areas located along the coast of Manado Bay. Consequently, it is important to study the sea surface current circulation in Manado Bay to deal with marine debris accumulation. In the present study, we utilized the DELFT3D software to simulate the hydrodynamic circulation in Manado Bay from 2016-2017. We conducted a 2-dimension (2D) horizontal hydrodynamic simulation using tidal and wind forcing from European Centre for Medium-Range Weather (ECMWF). The simulation results indicate that the change in bathymetry and wind affect the sea surface currents. During the summer monsoon (June-August), the sea surface current flows from the northeast to the southwest with an average speed of 1.1 cm s-1. On the contrary, during the transitional monsoon 1 (September-November), the sea surface current flows from the southeast to the northwest with an average speed of 1.3 cm s-1. Meanwhile, in the winter monsoon (December-February), the sea surface current originated from the southwest flows to the east with an average velocity of 1.9 cm s-1. Then, it moves from west to east during transitional monsoon 2 (March-May) with an average speed of 1.5 cm s-1. The current speed increases whenthe water enters the strait between the Bunaken Islands due to refraction, diffraction, and shallowing effect. As current flows toward the shallower area, the current speed increases, compensating the water column reduction.

Utilization of fluorescence images in chlorophyll in Cirebon waters, Indonesia

Satellite is one of the tools used to detect chlorophyll concentration. MODIS chlorophyll concentrations appears to be disturbed by colored dissolved organic matter (CDOM). The fluorescence approach can represent the chlorophyll concentration near the coast more accurately. The data for this study was obtained from satellite Aqua MODIS Level 2 which consisted of MODIS chlorophyll, MODIS fluorescence data, and Observation data. The data was taken on 6 September 2020 in Cirebon Waters. Results of the chlorophyll concentration field data ranged from 0.64 mg m-³ - 4.26 mg m-³. Estimation of chlorophyll concentrations using the standard chlorophyll method ranged from 2.55 mg m-³ - 7.20 mg m-³ and the chlorophyll concentrations using the fluorescence method were 2.58 mg m-³ - 3.5 mg m-³. Comparison of field data with satellite images is better with the florescence method than the standard MODIS chlorophyll technique, with an error of 47.8% for fluorescence and 235.5% for the standard MODIS chlorophyll.

Low Cost Method Of Turbidity Estimation Using A Smartphone Application In Cirebon Waters, Indonesia

Coastal conditions are closely related to the conditions of rivers and estuaries in the region and changes in the river condition caused by human activities will affect water turbidity. Rivers discharge which carries suspended materials and pollution to the sea have an important role in affecting Cirebon Water turbidity. The aim of this study is to estimate the turbidity using a smartphone application called HydroColor. The study data are obtained in September 2020. This study used Horiba U-10 and HydroColor as a method used to obtain the turbidity data of Cirebon Water. HydroColor is an advancement of technology that can be used to estimate water turbidity. Estimation method using HydroColor is a low-cost method because it only requires a gray card and a HydroColor that is available for iOS and Android for free. HydroColor uses a camera on a smartphone as a 3-band radiometer and produces reflectance values measured by HydroColor. Horiba U-10 data is used as in-situ data and is used to compared to HydroColor data to obtain a correlation between the two data. The results show that the correlation of HydroColor data with in-situ data is 0.91 and HydroColor tends to produce lower turbidity values than in-situ.

Zooplankton in seagrass and adjacent non-seagrass habitats in Tun Mustapha Park, Sabah, Malaysia

A comparison of zooplankton abundance and community in the seagrass and non-seagrass areas of Limau-limauan and Bak- Bak waters within the newly established Tun Mustapha Marine Park was made during 15-17 May 2017. Samples were collected via horizontal tow of a 140 μm plankton net. Environmental variables (temperature, salinity, DO, pH, turbidity) showed no significant differences among the study sites. However, zooplankton showed increasing abundance from non-seagrass, seagrass edge, to seagrass areas at Limau-limauan, while abundance values were comparable among the stations at Bak-bak. Overall zooplankton abundance was significantly higher at the seagrass areas relative to the non-seagrass station at Limau-limauan (p < 0.005), while no statistical difference was found at Bak-Bak (p < 0.21). Mean canopy height was 3-fold higher (p < 0.001) at Limau-limauan than Bak-Bak, suggesting the importance of seagrass bed structural complexity in habitat preference for zooplankton. Cluster analysis revealed the zooplankton community from the seagrass area at Limau-limauan was different from that at seagrass edge and non-seagrass areas, which may be attributed to the influence of seagrass meadows in forming characteristic zooplankton compositions. Marked differences in zooplankton composition and abundance even in close vicinity of sites suggest the importance of local small-scale variations in seagrass habitats in shaping the zooplankton community.

Marketing margins of aquaculture shrimp production in Kedah

Shrimp aquaculture has great potential for providing income and employment opportunities to farmers. Shrimp production can also contribute to economic growth given its high value and demand in Malaysia. However, it is often said that players in the marketing channel extract high margins for themselves. This study intends to verify this claim by examining a case study based on white leg shrimp (Litopenaeus vannamei) aquaculture in Kedah. The data for this study was obtained from a detailed study involving a shrimp retailer in Kedah. The marketing margins were calculated from the interviews of the farmer and the retailer. The results showed that the marketing channel was quite efficient because there was no large gap in the prices between the marketing channels. The difference between retail price and farm price is only RM7 per kilogram for the white shrimp which accounts for 43.75 percent of total farm price and represents the cost of bringing shrimps from the farm to the retail market.

Length-weight relationship and relative condition factor of pearl oyster, Pinctada fucata martensii, cultured in the Tieshangang Bay of the Beibu Gulf, Guangxi Province, China

Tieshangang Bay in the Beibu Gulf, Guangxi of China, is a strategic location for pearl farming. Although water pollution has been reported in this bay but the general health of the pearl oyster, Pinctada fucata martensii, farmed there has never been assessed. The present study examined the condition of P. fucata martensii farmed in the Tieshangang Bay by analyzing its length-weight relationship (LWR) and relative condition factor (RCF). A total of 111 specimens were sampled for measuring their shell height and total weight for determining the LWR and RCF. The coefficient of correlation of the LWR was high (R2 = 0.93), significant at 0.01 level. Negative allometric growth (b = 2.7048) was observed. However, P. fucata martensii achieved the expected growth in terms of weight, as determined through the RCF (mean 1.13). Negative allometric growth is commonly reported on the wild Pinctada spp. collected from different regions. Apparently, the water pollution in the Tieshangang Bay did not compromise the general health of the pearl oyster cultured there. Nevertheless, further study on the farm’s surrounding water quality and plankton availability is necessary to investigate the interaction between the growth of the oyster and its culture environment. In conclusion, the P. fucata martensii farmed in the Tieshangang Bay was considered healthy and the bay is still suitable for pearl oyster farming.

Advances in the use of photoheterotrophic, mixotrophic and multi-trophic systems in marine shrimp farming

The growth of aquaculture can cause different environmental impacts, from the use of large amounts of water to the excessive release of effluent. Shrimp farming can be done in different systems: extensive, semi-intensive, intensive and super-intensive. Extensive systems with low productivity (<500 kg ha-1 year-1), exhibit low technological levels and less control of environmental conditions. The semi-intensive system requires food supplementation, reasonable natural productivity, biomas yield of 3,000 - 5,000 kg ha-1 year-1) and water change (5 to 10 % day-1). To increase production, different culture systems are used, such as photoheterotrophic, heterotrophic and mixotrophic, with minimal water exchange (0.5 to 3 % day-1), providing greater biomass yield (intensive 10 to 20 ton ha-1 cycle-1 and super-intensive 20 up to 40 ton ha-1 cycle-1). These can be developed in nursery or grow-out tanks, but with high operating costs, high technological levels, disease control and better control of environmental conditions. However, intensive and super-intensive systems accumulate nitrogen, phosphorus and solid waste that can be transformed into biomass in multi-trophic aquaculture systems. In this review, we will discuss the effects of these systems on water quality and productivity of marine shrimp. The photoheterotrophic, mixotrophic and multi-trophic systems are interesting alternatives to the photoautotrophic systems in shrimp production, demonstrated by the higher zootechnical performance, as well as the environmental quality, since these models promote the minimum exchange of water and the transformation of nutrient residues in biomass.