S. M. N. Amin

Embryonic, larval, and early juvenile development of the tropical sea urchin, Salmacis sphaeroides (Echinodermata: Echinoidea).

Salmacis sphaeroides (Linnaeus, 1758) is one of the regular echinoids, occuring in the warm Indo-West Pacific, including Johor Straits, between Malaysia and Singapore. In order to investigate the developmental basis of morphological changes in embryos and larvae, we documented the ontogeny of S. sphaeroides in laboratory condition. Gametes were obtained from adult individuals by 0.5 M KCl injection into the coelomic cavity. Fertilization rate at limited sperm concentration (10−5 dilution) was 96.6 ± 1.4% and the resulting embryos were reared at 24°C. First cleavage (2-cell), 4-cell, 8-cell, 16-cell, 32-cell, and multicell (Morulla) stages were achieved 01.12, 02.03, 02.28, 02.51, 03.12, and 03.32 h postfertilization. Ciliated blastulae with a mean length of 174.72 ± 4.43 μm hatched 08.45 h after sperm entry. The gastrulae formed 16.15 h postfertilization and the archenteron elongated constantly while ectodermal red-pigmented cells migrated synchronously to the apical plate. Pluteus larva started to feed unicellular algae in 2 d, grew continuously, and finally attained metamorphic competence in 35 d after fertilization. Metamorphosis took approximately 1 h 30 min from attachment to the complete resorption of larval tissues and the development of complete juvenile structure with adult spines, extended tubefeet and well-developed pedicellaria, the whole event of which usually took place within 1 d postsettlement. This study represents the first successful investigation on embryonic, larval, and early juvenile development of S. sphaeroides. The findings would greatly be helpful towards the understanding of ontogeny and life-history strategies, which will facilitate us to develop the breeding, seed production, and culture techniques of sea urchins in captive condition.

Length weight relationships and fecundity estimates of long-spined Sea Urchin, Diadema setosum, from the Pulau Pangkor, Peninsular Malaysia

The present study is an attempt to describe the size frequency distribution, length weight relationships and fecundity estimates of long-spined Sea Urchin, Diadema setosum from the Pulau Pangkor, Peninsular Malaysia. In total 101 specimens of D. setosum were collected from the inter-tidal reef of Pulau Pangkor of Parek during the breeding season in May–August, 2010. Individual total length (TL) was measured using digital slide calipers and individual body weight (BW) was taken using a digital balance. Mean length of D. setosum was estimated as 59.66 mm and the mean weight was 101.68 g. Among the 101 specimens, 52 were males and 49 were females, indicating a sex ratio of male to female of 1:0.94. The logarithmic form of length-weight relationship of D. setosum was Log W = −1.3977 + 1.9049*Log TL, while the exponential form of equation obtained for the length-weight relation was W = 0.04*TL1.9049. The value of regression co-efficient (r2) estimated for the species was 0.63. The mean fecundity was estimated at 7,313,600 (±567,992) with a range between 6,290,000 and 7,980,000 eggs. Analysis of the relationship between the absolute fecundity (F) and total length (TL), and also between the fecundity and drained body weight (DW), revealed a linear regression model with a positive and significant relationship. This study presents results on the total length-body weight relationships and fecundity estimates of this Sea Urchin from Pulau Pangkor, Peninsular Malaysia for the first time.

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

3 . Peak abundance of Penaeus was found in June to July, while Acetes was found throughout the year with peak abundance in September. Higher abundance of Lucifer 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.

Population biology and stock status of planktonic shrimp Acetes indicus (Decapoda: Sergestidae) in the coastal waters of Malacca, Peninsular Malaysia

Reproductive cycle, growth, mortality and exploitation rate of Acetes indicus were examined in the coastal waters of Malacca, Malaysia between February 2005 and March 2007. Monthly length frequency data were analyzed using FiSAT software for estimating population parameters of A. indicus, including asymptotic length (L∝), growth co-efficient (K) and exploitation rate (E) to assess the status of the stock. The annual mean L∝ and K for males were estimated at 29.93 mm and 1.60 yr−1, and for the females were 40.95 mm and 1.20 yr−1. Mean growth performance index (φ′) was calculated as 3.15 and 3.31 for males and females, respectively. Maximum life span (tmax) of males and females was 1.88 and 2.50 years. Total mortality (Z) by length converted catch curve was estimated at 4.30 yr−1 for males and 3.62 yr−1 for females. The rate of natural mortality (M) for males and females was calculated as 2.54 yr−1 and 1.93 yr−1, and the fishing mortality (F) was 1.77 yr−1 for males and 1.70 yr−1 for females. Recruitment pattern of A. indicus was continuous throughout the year with two major peaks. The exploitation rate (E) of males was 0.41 and that of females was 0.47, though the exploitation rates were slightly less than the optimum level of exploitation (E = 0.50). Thus, the stock of A. indicus is under pressure in the coastal waters of Malacca, Malaysia.

Population dynamics of yellowtail scad, Atule mate (Cuvier 1833) in Marudu Bay, Sabah, Malaysia

The yellowtail scad, Atule mate, forms important fisheries throughout the Indo-Pacific region. To know about the stock status of A. mate in Malaysia, various population parameters were measured, by utilizing length-frequency data, that included asymptotic length (L∞), growth coefficient (K), mortality rates (Z, F and M), exploitation level (E) and recruitment pattern of this species from Marudu Bay, Sabah, Malaysia. Total length and body weight relationship was estimated as W = 0.007TL3.148 (R2 = 0.937). The asymptotic length (L∞) and growth coefficient (K) were estimated 27.80 cm and 1.50 yr−1, respectively. Total mortality (Z), natural mortality (M) and fishing mortality (F) were found to be 4.53, 2.46 and 2.07 yr−1, respectively. The exploitation level (E) was estimated 0.46. It was showed that the recruitment pattern was continuous with two major peaks per year. Relative yield per recruit predicted a maximum exploitation rate (Emax) which was 0.55. The current E value (0.46) is lower than the optimum exploitation (E = 0.50) as well predicted Emax. Therefore, it could be concluded that stock of A. mate in the investigated area of Marudu Bay, Sabah is under exploited.