Gonadosomatic index-based size at first sexual maturity of male and female Amblygaster clupeoides (Bleeker, 1849) (Clupeidae) on the east coast of the Malaysian peninsular

Size at first sexual maturity and condition of Amblygaster clupeoides were determined in a population at the Malaysian east coast. A total of 887 specimens were collected from commercial fishing vessels between March and November 2012. A random sample was taken each time to avoid bias in the cohort sampling. Size at first sexual maturity was determined by the relationship between the total length and gonadosomatic index (GSI). Similarly, the relationship between the condition factor and GSI was applied to determine the condition at first sexual maturity. The sex ratio was close to 1:1. The total length at first sexual maturity of both males and females were at around 18 cm. Males with a GSI of ≥3.2% and females with a GSI of ≥6.5% were mature, having condition factors of ≥0.90 and ≥0.93, respectively. Based on these results the minimum permissible capture size was identified. This study establishes a strong need for regular and continued monitoring of the changes in fish size at first sexual maturity

Culture of the Calanoid Copepod, Acartia erythraea and Cyclopoid Copepod, Oithona brevicornis with various Microalgal diets

Two experiments were conducted to develop Acartia erythraea and Oithona brevicornis cultures: The performance of five microalgal diets to produce nauplii, copepodites and adults of A. erythraea; and the performance of the same diets to produce nauplii, copepodites and adults of O. brevicornis. The five different microalgal diets were Isochrysis galbana (IG), Chaetoceros affinis (CA), Chlorella marina (CM), Nannochloropsis oculata (NO) and mixed algae (mixture of IG, CA, CM and NO at an equal abundance to provide the exact cell density). The results indicated that the abundance of both A. erythraea and O. brevicornis was higher in tanks supplied with IG and mixed algae than the tanks supplied with CA, CM and NO. IG and mixed algal diets were statistically similar on the mean abundance for both A. erythraea and O. brevicornis. The maximum production of A. erythraea nauplii was observed on day 12 of culture period and the nauplii production decreased from day 13 onwards. The mean abundance of A. erythraea copepodites and adults increased along with time up to the end of the culture period. In the case of O. brevicornis nauplii, the maximum abundance was observed on day 9 day of culture period and the nauplii production decreased from day 10 onwards. The mean abundance of O. brevicornis copepodites and adults increased gradually from the beginning to the end of the culture period. Under the experimental conditions of this study, both IG and mixed algal diets can be recommended for the best growth performance of A. erythraea and O. brevicornis

Effect of recent flood on ichthyoplankton and juvenile fish assemblage changes in Kuantan River revealed through DNA barcoding

Identifying early life stages of fishes to the species level is one of the challenging task for the taxonomist as the information on key morphological characters are overlapping between genetically closer individuals. Universal DNA barcode (cytochrome oxidase C subunit 1) gene sequence helped tremendously in species level identification of early life stages of fishes. This study was aimed to address the effect of recent monsoon on assemblage changes in Ichthyoplankton and juvenile fishes of Kuantan river, Whereby, the samples were identified to the species level using COX1 gene sequencing. Samples were collected using modified bubu light trap net between April 2015 and December 2015 in Kuantan river and its all tributaries. Fish larvae/juvenile size ranged from 3mm to 100mm, with most abundant individual belong to size class <10mm. A total of 28 species belong to 15 families were successfully identified to the species level from the total of 58 barcodes generated from 372 larval/juvenile samples collected. Unlike the previous study, significant shift in species assemblage has been recorded in this study. Statistical analysis showed significant effect of salinity and suspended particulate on the species distribution and abundance. The dominant fishes belong to the cyprinidae family followed by toxotidae, ambasidae and eleotridae compared to the previous study (Ariidae, Lactaridae and Lutjanidae). It could be concluded that the recent flood (mid-December 2014 to January 2015) in east peninsular Malaysia will have greater positive impact on Kuantan river fish diversity in near future

Analysis of Electrolyte Flow in Localized Electrochemical Deposition

AbstractLocalized electrochemical deposition (LECD) is a favorable technology for fabrication of the high-aspect ratio electrodes of various materials. This technology is found to be one of the simple and inexpensive ways to fabricate non-circular electrodes for micro-EDM. In order to fabricate non-circular electrodes a mask of non-conductive material is placed between the anode and cathode, which is immersed in a mixed electrolyte of copper sulfate, 1.0M sulfuric acid and as an additive agent 0.04 gm/liter of thiourea. The deposition of copper is localized on the cathode surface using a mask and applying ultra-short voltage pulses between the anode and cathode. In this set up the cathode is placed above the anode and mask, so that the deposited electrode can be used directly for EDM or any application without changing its orientation. In order to localize the deposited structure on the cathode surface, the electrolyte needs to flow through the mask and needs to touch the cathode and a constant flow rate of the electrolyte is maintained by using a pump. For this reason, micro holes of desired shapes are fabricated in the mask using micro milling. This study shows the effect of electrolyte flow through the micro holes of the mask and micro gap between the mask and anode on the microstructure of deposited electrode using FLUENT analysis. Moreover, an optimum range of electrolyte flow rate through the micro passages is also shown for the LECD process in order to fabricate high aspect ratio microstructures

Study on the contamination of najs mutawassitah in fish and water of the kuantan river

Halal food should be free from najs (filth). The Kuantan River is very important in term of recreation, ecology and fish supply. It has a wide variety of fishes, which is regularly marketed for human consumption. It receives a lot of untreated sewage waste, which may carry enormous level of enteric bacteria. Therefore, a 12-month study was conducted to (i) investigate the occurrence of enteric bacteria (najs) contamination in water and fish and the variation of quality and quantity of enteric bacteria in water and fish in the Kuantan River, (ii) elucidate the relationship between water quality, and the quality and quantity of enteric bacteria in water and (iii) make recommendation based quality and quantity of enteric bacteria in water and fish. For the qualitative and quantitative estimation of bacterial load including enteric bacteria, 3 fish species namely chemparus (Cyclocheilichtys apogon), kawan (Labiobarbus festivus) and kerisi (Pristipomoides filamentosus) were collected by gill net from Kuantan River. Water and sediment samples were taken at 4 (four) zones: 5 km from the Kuantan River estuary insight sea, Kuantan River estuary, 5 km upstream from Kuantan River estuary and 10 km upstream of the Kuantan River estuary. Bacteria were cultured in both nutrient and marine agar plates. A molecular method (16S rRNA gene sequencing) was applied to identify all bacteria up to their genus/species level. Overall, chemparus (6.68×103 ± 0.74×103/g) had significantly higher (P<0.01) bacterial load compare to kawan (5.12×103 ± 0.60×103/g) and kerisi (5.20×103 ± 1.49×103/g). Bacterial load was significant higher (P<0.01) in gut than in gill and followed by skin of fishes. No serious pathogenic enteric bacteria were observed in fishes and therefore, fish are still safe for human consumption. Enteric bacteria were commonly observed in sediments and various layers of water column in all sampling zones. This gives evidence that Kuantan river water was contaminated with najs (filth). Mean bacterial load in water in Zone D was 5.8, 4 and 4.3 times higher than in Zone A, Zone B and Zone C, respectively. A significant negative relationship (r = - 0.742, P<0.01) was observed between salinity and bacterial load in the river water. Bacterial abundance in sediment in Zone D (8.38×106 ± 0.31×106/5g) was significant higher (P<0.01) than bacterial abundance in sediment in all other Zones (Zone A: 1.27×106 ± 0.31×106/5g, Zone B: 2.38×106 ± 0.61×106/5g and Zone C: 0.64×106 ± 0.35×106/5g). The mean dissolved inorganic nitrogen (DIN) concentration was significantly (P<0.05) lower in the monsoon months compared to other months. The mean DIN concentration in water in the sampling Zone near the Kuantan city (2.24±1.48 mg/l) was significantly higher than the mean DIN concentration (0.20±0.14 mg/l) in the upstream zone. Waste from Kuantan city is significantly influencing the growth of enteric bacterial (in water and sediment) and the water quality of the Kuantan River. The result of the study can be used for the proper management of the Kuantan River. Careful waste management by the Kuantan city authority may reduce enteric bacterial load in water and sediment and concentration of inorganic nitrogen in the Kuantan river water. These will help in increasing fish production and save the biodiversity of the river

Marine capture fisheries in Malaysia with emphasis on overexploited fish stocks

Malaysia is very rich in marine fisheries resource. Marine fisheries sector can make an important contribution to the Malayisian’s wellbeing and prosperity. Marine fisheries sector is of fundamental importance to Malaysia in terms of protein supply, revenue generation and employment. This sector is also important for the food security of Malaysian coastal community. In Malaysia, the total capture production has increased in the last decade. The total capture production in Malaysia has been increasing by 10% since 2000. Although total marine capture production in Malaysia is still increasing every year, the production of some species such as yellowstripe scad and carangids are decreasing very rapidly. Very intensive research is needed for an urgent basis to find out the actual reason of reducing production of these species. However, the possible reason of dramatic reduction in catch might be due to over exploitation. Once any fish stock is overexploited, it produces lower yields than their biological and ecological potential. Therefore, proper management is urgently needed for sustainable production to ensure long-term sustainability in supplying animal protein for Malaysian people. To recover overexploited stock many suggestions has been proposed in the literature. After synthesizing literatures, two main approaches can be proposed for sustainable fisheries production: (i) establishing protected areas, or (ii) limiting capacity and number of fishing vessels, and the allocation of access rights. Continues data collection and their analysis are prerequisite for the successful of both approaches. Therefore, collaboration between scientists, policymaker and fishers is extremely valuable in managing fisheries for sustainable production. Apart from these, managing competing uses such as fishing industry, aquaculture, energy companies, shipping companies, government interests and conservation groups, and reducing by-catch should also be considered for sustainable fisheries production

Dynamics of dissolved inorganic nitrogen in a tropical tidal river

Dissolved inorganic nitrogen plays a critical role in controlling primary production in the river ecosystem. A 12-month study (September 2014-August 2015) was conducted to know the spatio-temporal dynamics of inorganic nitrogen in the Kuantan river which is influenced by daily tidal activity. Various forms of inorganic nitrogen (NO2- N, NO3-N and NH3-N) were measured at two sampling sites: 5 (near Kuantan city) and 10 (upstream, freshwater zone) km upstream from the Kuantan river estuary. Each zone had a total of three sampling stations which were considered as replication. Besides inorganic nitrogen, physical parameters such as water temperature, dissolved oxygen (DO), pH, conductivity, salinity were measured. All parameters were measured in the three layers (surface, middle and bottom) of the water column in each sampling station. Results indicated that mean inorganic nitrogen concentration near the Kuantan city (2.25±0.09 mg L-1) was significantly higher than the mean inorganic nitrogen concentration in the upstream zone (1.46±0.11 mg L-1). This might be due to organic discharge into the river from the Kuantan city compare to upstream zone. Similar pattern of inorganic nitrogen concentration was also observed in the case salinity, conductivity and DO concentrations. Overall inorganic nitrogen content was higher near the bottom water (2.15±0.16) compare to surface (1.65±0.10) and middle (1.75±0.12) layers of water. Both temperature and dissolved oxygen concentration were higher in the surface water compare to middle and bottom layers of water. The mean highest and lowest inorganic nitrogen concentrations were observed in January (0.70±0.15) and May (3.46±0.25), respectively. The overall mean inorganic nitrogen concentrations were lower in the monsoon months compare to non-monsoon months

Sustainable exploitation of marine fishes with an emphasis on overexploited fish stocks

2000, the production of some fishes such as yellowstripe scad and other carangids are decreasing very rapidly. An intensive research is needed for an urgent basis to find out the actual reason of reducing production of these species. However, the possible reason of dramatic reduction in catch might be due to over exploitation. Once any fish stock is overexploited, it produces lower yields than their biological and ecological potential. Therefore, proper management is urgently needed for sustainable production to ensure long-term sustainability of these fishes. To recover overexploited stock many suggestions has been proposed in the literature. After synthesizing literatures, two main approaches can be proposed for sustainable fisheries production: (i) establishing protected areas, or (ii) limiting capacity and number of fishing vessels, and the allocation of access rights. Continuous data collection and their analysis are prerequisite for the successful of both approaches. Collaboration between scientists, policymaker and fishers is extremely valuable in managing fisheries for sustainable production. Apart from these, managing competing uses such as fishing industry, aquaculture, energy companies, shipping companies, government interests and conservation groups, and reducing by-catch should also be considered for sustainable fisheries production