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

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

Length-weight relationships and relative condition factor of Parapenaeopsis sculptilis (Heller, 1862) from the coastal waters of Perak, Peninsular Malaysia

Length-weight relationship (LWR) parameters and relative condition factor (K n) of marine shrimp, Parapenaeopsis sculptilis (Heller, 1862) were estimated using length-weight data collected between February 2012 and January 2013 from the coastal waters of Terong, Perak, Peninsular Malaysia. The estimated length-weight relationship of P. sculptilis for both sexes was W = 0.00027TL2.80. Meanwhile, the estimated relative growth coefficient (b) was 2.80 for both sexes, indicating a negative allometric growth pattern of P. sculptilis in the investigated area. Relative condition factor (Kn) values ranged from 0.99 to 1.064 (1.013±0.005, mean ±SD). Kn value changes in various months: the highest peak was in March-April, indicating the spawning period and the trough and small peaks indicating the cycle gonadal development

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

Population dynamics of sergestid shrimps Acetes japonicus in the estuary of Tanjung Dawai, Kedah, Malaysia

Population parameters of male and female A. japonicus were studied using the monthly length frequency data to evaluate the mortality rates and its exploitation level. The sex ratio (male: Female) was found at 1: 0.94. Asymptotic length (L∞) was 25.20 mm and 28.88 mm for male and female, respectively. Growth co-efficient (K) for males and females was estimated at 1.80 and 1.30 year-1, respectively. Total mortality (Z) was calculated at 5.98 and 4.44 year-1 for male and female of A. japonicus respectively. Natural mortality (M) was 2.82 and 2.19 year-1 for the male and female shrimps. The fishing mortality (F) was 3.16 year-1 for male and 2.25 year-1 for female. Exploitation level (E) for male and female of A. japonicus was calculated at 0.53 and 0.51. The exploitation level was slightly over (E>0.50) the optimum level of exploitation (p = 0.50). The stock of A. japonicus was found to be slightly over exploited in Tanjung Dawai estuarine waters

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

Effects of feeding frequency on growth performance of endangered Temoleh, Peobarbus jullieni (Sauvage, 1880) juveniles

The experiment was designed to investigate the effects of feeding frequencies on the growth and feed utilization efficiencies of endangered Temoleh, Probarbus jullieni under captive rearing condition. The juvenile fish, weighing from 12.03g to 32.64g, were fed with an extruded commercial pellet for 60 days. Three restricted feeding regimes were tested in treatments viz., three meals per day (Teratment-1, T1), two meals per day (Teratment-2, T2) and one meal per day (Teratment-3, T3). The experiment was carried out in aquarium tanks on a recirculating water system. The fortnightly mean growth rate was 2.00 g in T1, 1.27 g in T2 and 0.57 g in T3, decreasing from T1 to T3 in that order. The percentage weight gain, specific growth rate (SGR), and daily growth rate (DGR) were significantly different (P < 0.05) among the treatments, which were highest in T1 as compared to those in T2 and T3, respectively. The best food conversion ratio (FCR) was also observed in T1. Among the tested treatments, three times a day feeding regime appeared to be the most suitable and could be recommended for rearing of P. jullieni under intensive culture systems

Influence of habitat structure and environmental variables on larval fish assemblage in the Johor Strait, Malaysia

Our previous study demonstrated that among different habitat sites (mangrove, estuary, river, seagrass and Open Sea) in Johor Strait, Malaysia, seagrass showed highest family diversity and abundance of larval fish. However, it is unclear whether this was due to difference in habitat complexity or water quality parameters. To test this, larval fish were collected by using a bongo net equipped with a flow meter by subsurface horizontal towing from different habitats in Johor Strait between October 2007 and September 2008. Various physico-chemical parameters were measured and then examined for any relationship to fish larvae diversity and abundance. Among the 24 families identified from the sites, seven families (Blenniidae, Clupeidae, Mullidae, Nemipteridae, Syngnathidae, Terapontidae and Uranoscopeidae) were significantly correlated with the tested waters quality parameters. Salinity showed a positive and negative significant correlation with Clupeidae (p < 0.01) and Uranoscopeidae (p < 0.05), respectively. Terapontidae was significantly correlated with dissolved oxygen (p < 0.01), while both Mullidae and Syngnathidae were significantly correlated with pH (p < 0.05). However, a canonical correspondence analysis test indicated weak overall correlation (36.4%) between larval assemblage and in the seagrass-mangrove ecosystem of Johor Strait, Malaysia. This likely indicates that habitat structure was more important in determining larval abundance (highest in the seagrass habitat) as compared to water quality at the tested sites. This study emphasizes the need to conserve seagrass beds as important nursery grounds for various fish larvae to ensure adequate recruitment and ultimately sustainable fisheries management

Influence of environmental parameters on shrimp post-larvae in the Sungai Pulai seagrass beds of Johor Strait, Peninsular Malaysia

Monthly sampling for shrimp post-larvae was conducted between April 2007 and March 2008 from the seagrass beds of Sungai Pulai Estuary, Johor, Peninsular Malaysia. Samples were collected from sub-surface using a bongo net equipped with a flow meter. In situ environmental parameters such as water temperature, dissolved oxygen, pH, salinity, total dissolved solid and conductivity were recorded during each sampling time. Total catch was comprised of four major taxa namely:Lucifer (94.9%), Acetes (1.52%), Penaeus (0.13%) and Mysis (0.06%). Mean density of shrimp post larvae (PL) was calculated as 22,614.74 individuals/100 m3. Peak abundance of Penaeus was found in June to July, while Acetes was found throughout the year with peak abundance in September. Higher abundance ofLucifer compared to the other genus was observed throughout the year with peaks in the monsoon months (May to July and October to December). The occurrence and abundance of Mysis was also restricted only in the monsoon months (November to January and May to July). There were significant correlation between the abundance of shrimp PL and in situ environmental parameters in the study area