Composition and diversity of larval fish in the mangrove estuarine area of Marudu Bay, Sabah, Malaysia

The composition of fish larvae and their diversity in different habitats are very important for fisheries management. Larval fishes were investigated in a mangrove estuary of Marudu Bay, Sabah, Malaysia from October 2012 to September 2013 at five different sites. Monthly samples of fish larvae were collected at five sampling sites by a plankton net with a mouth opening of 40.5 cm in diameter. In total, 3879 larval fish were caught in the investigated area. The mean density of ichthyoplankton at this area was 118 larvae/100 m(3). The fish larval assemblage comprised of 20 families whereas 13 families occurred at St1, 16 at St2, 16 at St3, 12 at St4 and 16 at St5. The top major families were Sillaginidae, Engraulidae, Mugilidae and Sparidae with Sillaginidae consisted 44% of total larval composition. St3 with 143 larvae/100 m(3) had the highest density amongst the stations which was due to higher abundance of Sillaginidae. Shannon-Wiener diversity index represented significant variation during monsoon and inter-monsoon seasons, peaking in the months December-January and May-June. However, Shannon-Wiener index, evenness and family richness showed significant differences among stations and months (p < 0.05)

Growth and length-weight relationship of Penaeus monodon (Fabricius) cultured in artificial sea water.

Post larvae of Penaeus monodon were cultured in a tank with artificial sea water between November 2009 and February 2010. Length and weight of the specimens were taken every seven days interval for the study of growth and length-weight relationship. The overall average growth rate was estimated at 0.36 mm per day. The mean daily growth rate was 0.53, 0.33 and 0.27 mm at the first, second and third month respectively. The mean body weight of the cultured specimens varied from 111.17 to 874.00 mg. Average growth of the body weight was estimated at 9.03 mg per day. The relative growth coefficient (b) and condition factor (a) was estimated at 2.94 and 0.00693. It is reveal that the exponent (b) of Penaeus monodon was very near to the isometric value (b = 3.0). So, the growth of P. monodon cultured in tank with artificial sea was isometric. It could be concluded that artificial sea water is feasible for culturing P. monodon when sea water is not available or sea water resource is further away from hatchery

Fecundity and egg size of grey-eel catfish Plotosus canius (Hamilton, 1822) from the coastal waters of Kampong Telok, Negeri Sembilan, Peninsular Malaysia

Despite the vast researches on catfish species in Malaysia, Plotosus canius, the grey- eel catfish which is primarily found throughout the coastal seas of Malaysia has been neglected. No single published work on aspects of biology, especially its reproductive biology is available. In this study, fecundity and egg size of P. canius from coastal waters of Kampong Telok, Malaysia were studied. A total of 32 gravid females were used in the study. The mean fecundity of the female having a length of 50.28 cm and a wet body weight of 680 g was estimated to be 865 eggs. Fecundity was found to show positive relationship with total length (r = 0.379), body weight (r = 0.494) and gonad weight(r = 0.336) but the values were not statistically significant (p>0.05). Egg diameter (mm) among the various length groups showed a polymodal distribution but the differences were statistically significant (p>0.05). This study being the first attempt to gather information of P. canius in Malaysia would form a basis for future works of this catfish

Effects of temperature on food consumption of juveniles dog conch, Laevistrombus canarium (Linnaeus, 1758) in laboratory condition

The dog conch, Laevistrombus canarium (Linnaeus, 1758) is one of the economically important marine molluscs that have high market value, particularly in the Southeast Asian region. This study investigates food consumption and assimilation by the juvenile conch at different temperature regimes (22, 26, 30 and 34°C). Live samples of the juvenile conch were collected on several occasions between December 2013 to May 2105 at Merambong shoal, Johor Straits, Malaysia. They were acclimatized for one week in stocking aquaria with well-aerated seawater at 30 PSU, 26°C and fed with commercial marine sinking pellets. Prior to experimentation, the gastric emptying levels of the samples were standardized by allowing them to feed until satiation, followed by 24 hrs starvation. All treatments were carried out in ten replicates of similar sized aquarium (20 x 15 x 15 cm) containing 4L of aerated seawater. The conch food consumption rate was significantly different (p<0.05) between different temperature regimes. The food absorption efficiency was also affected by different temperature regimes (P<0.05), and ranged between 50.14% to 73.76%. The food energy absorbed were then calculated, which showed significant variations between temperatures (P<0.05). Based on these calculations, higher food consumption and assimilation were recorded at 26°C followed by 30, 34 and 22°C. Results from this study allow us to predict the optimal temperature regimes (26°C) for the culture of these marine sea snail L. canarium. Further studies are indeed, needed to provide a better insight on the effect of climate change parameters on these species

Food and feeding habits of Omobranchus sp. (Blenniidae: Omobranchini) larvae in the seagrass-mangrove ecosystem of Johor Strait, Malaysia

The stomach contents of Omobranchus sp. (family Blenniidae) larvae were investigated in a seagrass-mangrove based ecosystem in Johor Strait, Malaysia from October 2007 to September 2008. Specimens of larval fish were collected through subsurface towing of a Bongo net from five different stations. The stomach sacs of 267 Omobranchus sp. larvae were separated and observed, which comprised of 24 significant food stuffs belonging to 6 main groups viz. phytoplankton (62.45%), zooplankton (18.24%), algae (5.56%), plant-like particles (5.75%), debris (4.22%) and unidentified particles (2.03%). In situ water parameters were also measured throughout the sampling cruises. There was a strong and significant positive correlation between stomach phytoplankton and salinity (r = 0.658, p < 0.05).? Canonical correlation analysis indicated a weak relationship (29.8%) between stomach contents and physico-chemical parameters. Only salinity appeared to be the controlling factor for the stomach contents of Omobranchus sp. larvae in the investigated area. Based on the stomach content analysis, it could be concluded that Omobranchus sp. were mainly herbivorous during the larval stages

Population characteristics, length-weight and length-length relationships of Acetes vulgaris (decapoda: Sergestidae) of the Coastal waters of Pontian, Johore, Peninsular Malaysia

The population structure, length-weight and length-length relationships of Acetes vulgaris were examined based on 1141 specimens collected in the months of June and July 2006 from Pontian, Johor Bahru. The morphological characteristics of A. vulgaris were examined and the result was found to be similar when compared with the previous research. Mean length of males was 23.18 ± 2.95 mm while for females was 23.91 ± 3.53 mm. The range of total length for the males and females was 14.00-33.00 and 13.00-32.00 mm, respectively. The relationship between the total length and body weight of A. vulgaris was W = 0.0178L2.6368 (r2 = 0.829) for males and W = 0.0082L2.9144 (r2 = 0.902) for females. The carapace length and total length, relationship for males and females were CL = 4.1844TL + 2.3983 (r2 = 0.732) and CL = 4.0872TL + 1.8879 (r2 = 0.732), respectively. The sex ratio of female to male was found to be at 1: 3.27 with the number of males exceeded that of the females

Impacts of gamete concentration, age and contact time on the fertilization success in the tropical species of white sea urchin, Salmaciella dussumieri

The globoid sea urchin (Salmaciella dussumieri) occurs abundantly in the Indo-West Pacific from the Island of the West Indian Ocean, East Africa, Magdagascar, Red Sea, South-East Arabia, Ceylon, Bay of Bengal, North Australia, Philippine, China and South Japan and Australia, and also has significant biological, ecological, aquaculture, conservational and medicinal importance. An experiment was carried out to assess the influence of sperm dilution, egg concentration, sperm-egg exposure time, and gamete aging on fertilization success of S. dussumieri in a captive laboratory condition. It has been found that dilution, age and contact time of sperm to egg were successively the most dominant factors effecting the success of fertilization, but concentration of eggs did not significantly so over the range investigated. The sperms retained their competency for more than two hours only in relatively dense sperm concentrations (> 10-4 dilution of `dry' sperm), although they exhibited lower capability and potency with increasing dilutions and age. In the trials of the egg-sperm exposure time, >80% eggs were fertilized within 10 sec of contact time at lower dilutions (10-3-10-2) of concentrated sperm, while some longer times were required to get the higher rates of fertilization. On the contrary, eggs remained in good quality for up to a period of 3 h and no abnormality or any adverse effects in fertilization were observed. The findings obtained from the present experiment reveal that limited longevity of diluted sperm have an important effect on fertilization rate of sea urchin eggs during natural spawning seasons in the field. Hence, the globoid sea urchin (S. dussumieri) is under extensive selective pressures to breed synchronously with the purpose of producing high sperm concentrations and higher sperm-egg interactions to maximize the success of fertilization in the water column

Sex ratio, spawning season and the size at maturity of Parapenaeopsis sculptilis (Heller 1862) in the coastal waters of Perak, Peninsular Malaysia

Parapenaeopsis sculptilis (Heller, 1862) locally referred to as "udang kulit keras" in Malaysia has profound biological, ecological, aquacultural and conservational significance. The reproductive biology of this important penaeid from the coastal waters of Perak, Peninsular Malaysia, was studied during the period between February 2012 to January 2013. Females outnumbered males with a sex ratio of M: F= 1:3 (P < 0.05). Four maturity stages of female gonads viz., immature, maturing, mature and spent stages were distinguished. The first stage of sexual maturity was attained at a length of 9.3 cm, and female P. sculptilis showed a peak gonadosomatic index during the month of April, August and October, indicating that P. sculptilis potentially breeds throughout the year. The findings of this study would greatly contribute towards the understanding of gonadal maturation, spawning season and breeding biology, which could be important for the effective population management of this prawn species

Optimization of surface roughness in high speed end milling of Titanium alloy Ti-6Al-4V under dry conditions

The techniques of High Speed Machining (HSM), while still in an initial stage of wide acceptance, have already been proven in leading aircraft manufacturing plants [1]. HSM has been applied successfully to materials like magnesium and aluminum. Among the titanium alloys, Ti-6Al-4V being the most commonly used and it is the workhorse alloy of the titanium industry, accounting for over 45% of the total titanium production [2]. Therefore, the efficiency of titanium machining is one of the major challenges in production engineering. Various studies have been conducted on the surface roughness in end milling of various materials using deferent cutting tools, experimental and optimization techniques. Baek et al [3] selected the optimal 187ederate using a bisection method. Peigne et al [4] studied effects of the cutting vibratory phenomena and their impacts on machined surface roughness. Franco et al [5] developed a numerical model for predicting the surface profile and surface roughness in face milling with round inserts. Alauddin et al [6] used RSM and ANOVA to optimize the surface finish in endmilling of Inconel 718. Only two cutting parameters (i.e., cutting speed and feed rate) were considered, and 13 experiments were conducted. An important parameter (depth of cut) was not considered. Choudhury et al [7] noticed that the surface finish improves with increase of the cutting speed at constant feed rate and constant depth of cut in machinability assessment of Inconel 718. Kuang-Hua Fuh and Chih-Fu Wu [8] used RSM for surface quality prediction in end milling of Al-alloy. Beside the usual cutting variables, they considered nose radius and flank width as parameters to be optimized. In this study, 3-level full factorial experimental designs of RSM were used for high speed end milling of Ti-6Al-4V. The 3-level factorial method was used to study qualitatively the 3D (three dimensional) surface morphologies/topographies for the machined surfaces of Ti-6Al-4V to determine the machining conditions that could give the best possible surface finish. Desirability function of RSM was applied to optimize the cutting parameters

Variation of growth and proximate composition in Portunus pelagicus juveniles fed with selected feeds in recirculating aquaculture system (RAS)

Aim: The experiment was conducted to determine the suitability of using scad fish, Acetes shrimp and common squid for the direct and indirect application as diets for the juvenile rearing of the blue swimming crab Portunus pelagicus. Methodology: A total of 54 crab juveniles with an initial weight of 2.46 ±0.94 g were randomly stocked in triplicate at 6 crabs per 60 l tank (0.26 m²) experimental units and fed twice daily with three different types of feed namely scad fish, squid tissue and frozenAcetesshrimp foraperiodof31days. Results: At the end of the trail, ammonia and nitrite-nitrogen compound were significantly higher in Acetes shrimp fed group. It is found that final body weight (g) of P. pelagicus was significantly higher when fed with squid, however no significant differences were noticed between scad fish and Acetes shrimp fed groups. The whole body proximate composition was similar in all the diet fed individuals except the level of lipid which was higher in squid compared to scad fish and Acetes shrimp. Significantly (p<0.05) better food conversion ratio (FCR) was observed in juvenile crab fed with squid even though scad fish possessed the highest crude protein of 83.33%. Interpretation: Overall, the results suggested that squid meal could be recommended for P. pelagicus juvenile culture. Hence, squid meal may be incorporated in crab artificial diet as protein source to attain better survival and growth