Monoculture of climbing perch, Thai koi, Anabas testudineus (Bloch) under different stocking densities at on-farm

An on-farm trial was undertaken in nine earthen ponds (400 to 640m2) to evaluate the growth and production potentials of climbing perch, Thai koi (Anabas testudineus) for the period of four months from March through June 2006. Three stocking densities such as 75,000 (T1), 100,500 (T2) and 125,000/ha (T3) were tested with three replications. Fish were fed with commercial (SABINCO) pelleted feed (35% crude protein). Fish productions obtained in three treatments such as T1, T2 and T3 were 6,480±217, 6,384±154, 6,617±187 kg· 1ha, respectively. The results demonstrated higher mean growth in T1 than in T2 and T3. However, the net benefit was achieved Tk. 7,26,975 from T1, where the stocking density was 75,000/ha.

Culture feasibility of silver barb (Barbodes gonionotus Bleeker) and GIFT with shrimp (Penaeus monodon Feb.) in brackishwater pond

An experiment was conducted to understand the culture feasibility of sliver barb (Barbodes gonionotus) and GIFT (Genetically Improved Farmed Tilapia) with shrimp (Penaeus monodon). There were three different treatment (T) combinations: (T1) shrimp (10,000/ha) and silver barb (10,000/ha), (T2) shrimp (10,000/ha) and GIFT (10,000/ha), and (T3) shrimp (10,000/ha). Shrimp, after 120 days of culture, attained an average weight of 23.77g in T1, followed by T3 (23.70g). The highest average weight was recorded in T2 (24.93g). The specific growth rate (SGR) of shrimp was 6.9%, 6.94% and 6.9% for T1 T2 and T3, respectively. The SGR for the B. gonionotus and GIFT was 2.56% and 4.26%, respectively. The final weight of silver barb was 69.75g and that of GIFT was 161.83g. Survival of shrimp was higher (65.50%) in T2, followed by T3 (59.97%) and T1 (57.03%). Survival rate of silver barb (58.10%) was lower compared to that of GIFT (78.43%). Sporadic and scanty mortality of silver barb with a symptom of blind-red-protruded eye, swollen belly and body lesion was observed. Production of shrimp was higher of 284.05 kg/ha in monoculture, followed 162.47 kg/ha in concurrent culture with silver barb and 136.77 kg/ha culture with GIFT. In spite of similar stocking density of B. gonionotus and GIFT in T1 and T2, respectively, the production of GIFT was higher (1272.95 kg/ha) than that of silver barb ( 402.72kg/ha). Survival, final weight and production rates of shrimp among the treatments were found insignificant while total production of shrimp/fish was found to vary significantly (P

Polyculture of carps using over-wintered fingerlings under different stocking densities

An on-farm trial was undertaken in twelve earthen ponds (1200-1600 m') to evaluate the growth and production of over-wintered fingerlings of rohu (Labeo rohita), catla (Carla catla) and mrigal (Cirrhinus rnrigala) in polyculture at three stocking densities. The stocking densities were 2,250; 3,250 and 4,250 fish/ha in treatment-1, treatment-2 and treatment-3, respectively. Fish in all ponds were fed with rice bran and mustard oil cake at the ratio of 3:1. Fish production obtained in three treatments were 2325±74.75, 2620±49.66 and 2982±171.52 kg/ha. The results demonstrated higher mean growth in T-1 than in T-2 and T-3. However, the highest production as well as net benefit was obtained in treatment-3.

Effect of stocking density on the production of common carp (Cyprinus carpio Lin.) in cages at Kaptai lake, Bangladesh

Growth, survival and food conversion ratio (FCR) of Cyprinus carpio in cages at different stocking density were studied in Kaptai lake. Fingerlings of common carp (12.47 ± 4.29 g) were stocked at 25/m2 , 50/m2 and 75/m2 each with replication in six floating net cages each of Sm x Sm x 4m and reared for 240 days. The growth rate was inversely related to the stocking density with the mean weights of 325.5 ± 11.74 g, 268.99± 8.44 g and 167.0 ± 11.66 g at low, medium and high densities, respectively. At harvest, standing crop biomass averaged 7 .82, 12.83 and 11.58 kg with the survival of 98.9%, 97.6% and 94.4% and food conversion ratios of 4.51, 3.82 and 4.21 for the above three densities, respectively. Weight gain and production at density 25 fish/m 2 were significantly different (p< 0.01) from other two densities. Water quality was not affected in the cages having different stocking densities.

Larval rearing and fry raising of Pangasius sutchi(Fowler)

Pangasius sutchi were artificially bred for determining the hatching success and larval growth response to live food in relation to varying stocking densities. The fertilized eggs were hatched out with successful hatching rates ranging between 60 and 63%. Newly hatched larvae of 4.4 mm average length were reared using Tubifex as live food in metallic trays with water temperature of 27 to 29.5°C and dissolved oxygen level of 3.88 to 6.22 mg/1 for 6-day with an average survival rate of75.56±13.25%. The P. sutchifry of9- day old were further reared using Tubifex in the polythene covered metallic trays at the stocking densities of 2-7 fry per litre of water for a period of 14 day. P. sutchi fry raising at 4 individual per litre of water for 14 day gives better results in terms of survival and growth.

Scalar dissipation and mean reaction rates in premixed turbulent combustion

A general equation for a variance parameter, appearing as a crucial quantity in a simple algebraic expression for the mean chemical rate, is derived. This derivation is based on a flamelet approach to model a turbulent premixed flame, for high but finite values of the Damköhler number. Application of this equation to the case of a planar turbulent flame normal to the oncoming flow of reactants gives good agreement with DNS data corresponding to three different values of the Damköhler number and two values of the heat release parameter. © 2011.

Nursery management system of stinging catfish, Heteropneustes fossilis and walking catfish, Clarias batrachus in Bangladesh

A total of four experiments were conducted to develop nursery management system for the two important native catfishes viz. stinging catfish, Heteropneustes fossilis and walking catfish, Clarias batrachus during 2003 and 2004. Two experiments were conducted in on-station condition to determine stocking density efficacy in hapa and in earthen mini ponds for H. fossilis. This was followed by on-farm trial on stocking density in earthen mini ponds. In hapa, the highest survival rate was 60% for H. fosssilis at stocking density of 100/square meter; followed by 54.5 and 50% at stocking densities of 150 and 200/square meter, respectively. Similarly, gain in weight and length was also better in lower stocking densities. Similar survival rate (45 to 55%) was observed in three densities in earthen mini ponds. However, gain in weight and length showed no significant (p<0.05) differences. H. fossilis, C. batrachus showed almost similar survival rates (57.5-59.0%) in all the three stocking densities (100, 150 and 200/square meter) in earthen mini ponds in on-station condition. In terms of gain in weight and length showed no significant (p<0.05) differences in pond conditions. Almost similar result was obtained in terms of growth and survival in on-farm condition.

Studies on the occurrence and growth rates of two intertidal fouling bryozoans in the Mattancherry channel of Cochin harbour, south-west coast of India

Occurrence and growth rates of two species of intertidal fouling bryozoans namely Electra bengalensis (Stoliczka) and Electra crustulanta (Pallas) are presented in this paper. The former was a typically marine form, settling on panels only during the high saline conditions of the pre-monsoon period and were absent during the low salinity conditions of the monsoon period, while the latter appeared to be a typical brackish water form settling on panels during the low saline conditions existing during the monsoon and post-monsoon periods and were totally absent during the pre-monsoon months. Regression co-efficient of the former was higher than that of the latter suggesting more pronounced growth in Electra bengalensis. Maximum growth for this species was noticed during March, April and May (pre-monsoon) while for the other species growth was more or less similar during monsoon and post-monsoon months (June-January) showing that the species was at home in oligohaline and mesohaline waters.

DIFFERENT RATES OF MITOCHONDRIAL-DNA SEQUENCE EVOLUTION IN KIRK DIK-DIK (MADOQUA-KIRKII) POPULATIONS

We have investigated evolutionary rates of the mitochondrial genome among individuals of Madoqua kirkii using the relative rate test. Our results demonstrate that individuals of two chromosome races, East African cytotype A and Southwest African cytotype D, evolve about 2.3 times faster than East African cytotype B. Cytogenetic changes, DNA repair efficiency, mutagens, and more likely, hitherto unrecognized factors will account for the rate difference we have observed. Our results suggest additional caution when using molecular clocks in the estimation of divergence time, even within lineages of closely related taxa. Rate heterogeneity in microevolutionary timescales represents a potentially important aspect of basic evolutionary processes and may provide additional insights into factors which affect genome evolution. (C) 1995 Academic Press, Inc.

The effect of various protein levels on the growth and survival rates of Penaeus monodon Fabricius

Postlarvae of tiger prawns, P. monodon , were fed with various protein levels of 0; 30; 40 and 50%, fish meal and rice bran were combined and pelletized for 16 wks. Prawns used had an average mean length of 1.2 mm and an average mean weight of 5.5 mg. Nitrite, ammonia, dissolved oxygen content, temperature and pH were monitored. After one month of feeding, growth increments of postlarvae fed with 30% protein diet were significantly different from those given 0; 40 and 50%. Survival rate of the group fed 40% protein was higher (81.7%) but was not significantly different from those fed 30% (68.0%). The highest feed efficiency was obtained from the 30% protein pellets (4.6). At the end of 16 weeks, growth increment of 40% protein level was significantly different from the 30% and 50% protein levels, but the survival rate was not signficantly different from the 30% protein level. Feed conversion for the 40% protein diet was 2.8.

The propagation of the mud crab Scylla serrata (F.) de Haan

The mud crab Scylla serrata is an important commercial species found in many brackish areas in the Philippines. During spawning and hatching, the berried females migrate to the sea. Seeds for pond stocking are obtained from the wild. Because of the unpredictability of seed supply, there is a need to propagate the species artificially. Thus, spawning, larval rearing, maturation, and rematuration of the species are being studied. The first attempts at hatching S. serrata were successful with rates varying between 75% and 90%. Two out of three trials on larval rearing yielded a few megalops. The first zoeal stages were fed diatoms, rotifers, Artemia salina, and bread yeast. Overfeeding programs were implemented during the critical premolting periods to prevent weakening of the larvae and lessen cannibalism. Larval weakening during the premolt makes them susceptible to attacks by fungi like Lagenidium and ciliates like Vorticella. S. serrata larvae survived salinity levels as low as 15 ppt until the 14th day of rearing. Other larvae were able to survive in salinities of 30-32 ppt for 8 to 13 days. Zoeal molting was hastened by lowering the salinity to 25-27 ppt. Artificial broodstocking of juveniles and adult crabs has been made possible using a simple refuge system made of three-compartmented hollow blocks. This system has been helpful in minimizing fighting among crabs. Remarkable growth rates have been observed with feeds like mussel meat and trash fish. Average growth increments of 11 mm carapace length and 20 . 35 g body weight have been observed every fortnight. A newly spent spawner could gain additional weight of 22 . 5 g in only 6 days. Feeding rates of juveniles and adult crabs have been established based on the average body weight from an experiment using mussel meat. Crabs feed more at night. In another experiment, eyestalk ablation was found to be effective in inducing growth and mating. Aside from hastening the molting process, copulation is induced even among the small crabs (average carapace length = 55 mm). Natural mating lasts about 26 hr. A copulation which lasted for seven days with a break in between was observed.

Mass production of Penaeus monodon Fabricius juveniles in earthen nursery ponds

Different culture techniques were tried for rearing larvae of Penaeus monodon, in order to obtain preliminary data on stocking density, water management, fertilization versus feeding and effect of different types of vertical substrate. The results of the experiments showed that: (1) older fry have greater chances of survival; (2) the traditional nursery pond designs and practices used for milkfish in the Philippines are applicable to prawn only at very low densities and give acceptable high survival rates only when used with the older postlarval stage.

The effect of various salinity levels and stocking density manipulation methods on the survival of milkfish fry (Chanos chanos Forsskal) during storage

Results of the study indicate that the survival rate and increase in body weight did not differ significantly at different salinity levels or at different stocking density manipulation methods. A significant interaction between salinity and stocking density manipulation could not be demonstrated statistically. There apparently is no need to reduce the salinity of the water used in storing milkfish Chanos chanos fry in order to attain higher survival as commonly believed. Sufficient food and maintenance of good water quality are more important than salinity for higher survival of fry during storage.

Studies on the egg quality of Penaeus monodon Fabricius based on morphology and hatching rates

Eggs of P. monodon are classified into 5 different types on the basis of morphological criteria and hatching rates: A sub(1) eggs, which undergo normal development with 58% hatching rate; A sub(2) eggs, which show delayed and/or abnormal development with 32% hatching rate; B eggs, which are unfertilized and characterized by irregular cytoplasmic formation; C eggs, which are unfertilized and show no change in appearance; and D eggs, which are unfertilized and show extensive bacterial presence. The establishment of a highly linear relationship between percent A sub(1) eggs and hatching rate provides a useful tool to aid the hatchery technician in determining which spawnings to reject outright and which to rear through the larval and post-larval stages.

Effects of water movement and aeration system on the survival and growth of hatchery bred sugpo (Penaeus monodon Fabricius) in earthen nursery ponds

An experiment was conducted to determine the effects of water movement and airlift aeration on the survival and growth of P. monodon fry reared from P sub(4)P sub(5) to P sub(32)P sub(33) in earthen brackishwater ponds. The high survival rates obtained justify the need for aeration when using the earliest stages of fry (P sub(4)P sub(5)) at higher stocking densities. For older stages regardless of source and at lower stocking densities, nursery operations based on traditional methods could also achieve better survival rates.