Embryonic and larval development of Mystus gulio (Ham.)

Mystus gulio eggs are strongly adhesive and contain relatively small yolk (0.75-1.0 mm). The egg envelop is thick and transparent. First cleavage (two cells), four cells, eight cells, sixteen cells and multi cells stages were found 20, 25, 35-40, 60 and 70 minutes after fertilization, respectively. The morula stage was visualized within 1.5 h after fertilization. The heart beat visible and the circulatory system commenced after 16 h of fertilization. Embryos hatched 18-20h after activation of egg. The newly hatched larva measured 2.82±0.03 mm in length and 0.32±0.06 mg in weight. The yolk sac was fully absorbed by the third day though larvae commenced exogenous feeding even before completion of yolk absorption. A 5-day old post larva began wandering in search of food. Ten-day old post larvae endowed with eight branched rays in dorsal fin and seven in caudal fin. Fifteen-day old post larvae had the pectm:al spine become stout though the embryonic fin folds had to be disappeared. The length of fingerlings ranged from 25-30 mm after 30 days, and their external features were just like those of an adult except that they were not sexually matured.

Effects of supplemental feed and fertilizer on growth and survival of Macrobrachium rosenbergii (de Man) post larvae in pond nursery system

The study was conducted to compare the performance of different nursing practices of giant freshwater prawn (Macrobrachium rosenbergii) post-larvae (PL). Three treatments such as only fertilizers (T1), fertilizers with 5% supplementary feed (local feed) (T2), and 10% commercial feed (T3) were applied in the nursing system of prawn PLs in earthen pond. An earthen pond (315m²) was divided into nine equal small ponds by fine meshed nylon nets. Feeds were used once daily on a tray placed near the pond bottom. There was a significant difference (p<0.05) in some water quality parameters like pH and total alkalinity, but all measured water quality parameters viz. water temperature, transparency, dissolved oxygen and ammonia-nitrogen were within the acceptable range for nursing of prawn PL. The results showed that the mean final lengths of prawn post-larvae were 6.3±0.07 cm, 7.12±0.22 cm and 8.17±0.16 cm in T1, T2 and T3, respectively. There were significant difference (p<0.05) in mean final length of prawn PL among the treatments. Significantly higher (p<0.05) average daily weight gain was observed in T3 (0.071 ±0.007 g) than in T2 (0.052±0.006 g) and T1 (0.031 ±0.002 g). The specific growth rate (SGR) of T3 (8.81±0.26) was found significantly higher (p<0.05) than T2 (8.35±0.22) and T1 (7.42±0.11). Survival rate (%) was also significantly higher (p<0.05) in T3 (66.24±1.58) than in T2 (60.52±1.64) and T1 (53.86±2.71). Therefore, it may be concluded that the growth and survival in prawn nursery was better in commercial feed than only fertilizers and fertilizers with local feeds.

In vivo and in vitro storage of kutum, Rutilus frisii kutum eggs

Effects of post-ovulatory and post-stripping retention time and temperature on egg viability rates were studied in kutum (Rutilus frisii kutum). Eggs were retained inside (in vivo storage) or outside the ovarian cavity with ovarian fluid (in vitro storage) at various temperatures. Two experiments were performed: 1) Partial volumes of eggs were stripped and fertilized at 24- hour intervals for 96 hours post-ovulation (HPO) (at 11 °C) and at 12-hour intervals for 72 HPO (at 14 °C), and 2) stored eggs were fertilized after 0, 2, 4, 6, and 8 hours post-stripping (HPS) at temperatures of 4, 10, 12, and 26 °C. In the first experiment, the highest eyeing and hatching rates (76% and 60% at 11 °C; 81% and 71% at 14 °C) and the lowest eyed-egg mortalities (20% at 11 °C; 12% at 14 °C) occurred in the eggs fertilized immediately (0–24 HPO at 11 °C and 0–12 HPO at 14 °C) after ovulation. Egg viability, as shown by successful eyeing and hatching rates, was completely lost by 72–96 HPO at 11 °C, and 60–72 HPO at 14 °C. In the second experiment, the maximum eyeing (87%) and hatching (75%) rates of eggs took place at 0 HPS followed by 8 HPS (> 80% and > 70%, respectively) at 4 °C. As storage temperature increased, egg viability decreased: 80%, 70%, and 50% viable at 8 HPS at 4, 10, and 12 °C, respectively. The eggs stored at 26 °C lost their viability almost completely after 4 HPS. Eyed-egg mortality increased from 13% at 0 HPS to 48.2% at 4 HPS at 26°C. These results demonstrate that egg stripping should take place within 168 °C-hours after ovulation and that complete loss of viability of the eggs occurs by 672°C-hours after ovulation. The in vivo storage method is more effective compared to in vitro storage. Also successful in vitro storage of eggs can be used atleast within 8 hours at temperatures ranging from 4 to 12ºC.

Physiological and biochemical study of over-ripened oocyte in the cultivated Caspian brown trout (Salmo trutta caspius) and determination of egg quality markers

To determine the best time for egg stripping after ovulation and over-ripened oocyte in the Caspian brown trout (Salmo trutta caspius), the eggs were retained in the parental abdominal cavity for 40 days post-ovulation (DPO) at 7±0.6°C. Eggs were stripped every 10-day interval in 4 treatment and were fertilized with a pool of semen obtained from 8 males. Also, the physiology and biochemistry of the eggs and ovarian fluids were studied. Results showed that the level of eyed eggs and hatched alevins declined with over-ripening time: that is, the expected amounts (90.65 ± 6.28% for eyeing and 86.33 ± 6.82% for hatching) in newly ovulated eggs (0–10 DPO) decreased to 0.67 ± 1.34% and 0.49 ± 0.98%, respectively, in over-ripened eggs (30–40 DPO). However, larval abnormalities remained constant for 30-days after ovulation. During the course of oocyte over-ripening, the pH of the ovarian fluid significantly decreased and the concentration of glucose, protein, calcium, iron, and aspartate aminotransferase activity significantly increased. Moreover, the concentration of protein, triglycerides, and aspartate aminotransferase activity in the eggs also changed. In the newly ovulated egg, the yolk consisted of homogenous tissue and its perivitelline space diameter had no considerable differences. With over-ripening, the yolk became heterogeneous, while chorion diameter and micropyle did not change. The perivitelline space diameter varied among different areas. The present study demonstrated that the best time to take Caspian brown trout eggs after ovulation at 7± 0.6°C was up to 10 DPO. Among the studied parameters of the egg and ovarian fluid, egg quality was related to both ovarian fluid parameters (e.g., pH, protein, aspartate aminotransferase, glucose, cholesterol, triglycerides, calcium, iron) and egg parameters (e.g., cholesterol, triglycerides, iron, aspartate aminotransferase). Thus, these parameters can be used as a egg quality markers in this species.

The study of the ergosan and vibromax effects on growth performances, survival rate and increase of the resistance to some of the environmental stresses in post larvae stage of the Indian white shrimp

In this study, which has been done in Hormoz larve Hatchery at Kohestak in Minab at 1385, the efficiency of Ergosen and Vibromax vaccine and the effect of them on growth factors such as total length, Carapase, dry weight and the number of upper mordents of rostrum and survival of the stages of larvae and post larvae of Indian white shrimp was studied. Thus in order to comparison the effects of Vibromax and Ergosen, each of them separately, in one treatment, and in another simultaneously with one control treatment was used. Vaccination against larvae shrimps was done through Artemia. This study used four treatments with three replicates in a completely randomized design and comparison of means was done through Duncan test. Breeding larvae and post larvae of Indian white shrimp from zoa I stage to PL 15 was done in 20 litter plastic buckets. Present results indicated that the highest amount of growth and survival factors in larvae stage (from zoa to PL1), and also in stages of PL5 and PL15, in the treatment of Ergoson effect + vaccine and it was with a little difference from that treatment of Ergoson effect which was in high significance difference in regard to control treatment at α<0.01 level and treatment of vaccine effect and control treatment at α<0.01 level often have no significant difference. This research used environmental stress tests to study the quality of post larvae under experiment. Studying in this field showed that feeding vaccine to larvae of Indian shrimps which was done through Artemia nauplii enrichment ,and ergosen , in treatment of ergosen vaccine lead to more resistance of post larvaes against salinity stress tests and formalin .This case was observed in every three stages ,so that in stress formalin test 100 parts per million and also 10 and 20 salinity parts in thousands the most survival was observed in treatment of Ergosan effect+vaccine and after that in treatment of Ergoson effect and with a little difference in treatment of vaccine effect. Of course this case, in treatment of Ergoson effect + vaccine due to the synergistic properties vaccine with Ergoson was more than to other treatments, while every three treatments, in most stages had significant difference toward control treatment at α<0.01 level and the control treatment because of not having Ergoson and nauplii artemia with vaccine, having the least survival rate in this stages.

Evaluation and comparison of ozone, hydrogen peroxide and physical treatment on fungal infection prevention and hatching rate of Iranian sturgeon (Acipenser persicus)

Ozone due to having low half-life and devoid of environmental harmful effects is recognized as one of the most effective disinfectant and fungicide in aquaculture. The objective of this study is to consider the effects of periodicay ozonation, hydrogen peroxide treatment, and physical treatment capability in hatching rate enhancement. Three concentrations of 0.05, 0.1 and 0.15 ppm ozone (10 min) and peroxide hydrogen with dose of 500 and 1000 ppm in two procedures accompanied with physical treatment and without physical treatment were examined on hatching rate. In the first year, Egg ozonation (0.1 ppm) with physical treatment have been resulted the greatest hatching rate (81.4%). In the second year, egg treatment with 1000 ppm hydrogen peroxide with physical treatment have been showed the greatest hatching rate (78%). Average hatching rate for the blank control treatment (without disinfectin and physical treatment) was 32.7%. From the economic viewpoint, 0.05 ppm ozone with physical treatment, due to considerable minimizing at consumption energy and ozonation system retention costs, indicated as the best treatment than other ozone treatments for fungal control. Very low correlation (r=-0.14) have been observed between hatchery water temperature and fungal infection percentage in control treatment.

Widows' struggles in post-war Sri Lanka

This report documents the post-war struggle of women, mainly widows, from the fishing communities of Mannar, Sri Lanka, attempting to reconstruct their lives.