Effect of sodium bicarbonate on hatching and on postembryonic growth of Brachydanio rerio, Cyprinus carpio, Labeo rohita, Cirrhinus mrigala and Catla catla

The treatment of sodium bicarbonate at the dosage of 100 to 1000 mg/litre has been tested experimentally on the hatching and postembryonic growth of Brachydanio rerio, Cyprinus carpio, Labeo rohita, Cirrhinus mrigala and Catla catla. Lower dosages of 100 to 200 mg have been found to reduce the hatching period, yolk absorption period and improve the survival and growth of the post embryonic larvae. The higher dosages of 500 to 1000 mg has been found to reduce the hatching percentage and post embryonic growth of the larvae. The findings indicate that application of sodium bicarbonate in the hatchery and nursery management of carps in the lower dosages of 100 to 200 mg/L to improve hatching and postembryonic growth.

The bacterial flora and their possible association with spoilage in a variety of fresh-water fish: Cyprinus carpio. var. communis

The bacteria from a variety of fresh-water fish, Cyprinus carpio. var. communis, showed the presence of micrococci, Gram positive and Gram negative rods. These have been characterized as far as was possible. Of thirty-eight strains of bacteria used, only six strains were considered as causing spoilage of fish flesh in experiments where flesh was incubated with individual cultures of the bacteria. These six strains had been found on the surface and/or intestine of the fish and support the suggestions that, after death, invasion of flesh by bacteria from the surface and intestine could be the cause of bacterial spoilage of fish.

Studies on growth and mortality of Cyprinus carpio (Lin.) in floating ponds

Growth and mortality rate of Cyprinus carpio (Linnaeus) under five different dietary conditions were studied in fifteen floating net cages in ponds of the Bangladesh Agricultural University Campus, Mymensingh. Growth rate was found to vary under different dietary conditions. The feed with mixture of 25% rice bran, 5% wheat bran, 30% linseed oil cake and 40% water hyacinth leaf meal exhibited the highest growth rate. The gain of log of body weight per unit increase of log of total length was significant. Significant survivals of the fishes were found.

Catch assessment of indigenous and exotic carp species of Nasti baor

An investigation on length-weight relationship, length-frequency distribution, catch per unit of effort (CPUE) and stocking and harvesting status of three Indian major carps: rohu Labeo rohita, catla Catla catla and mrigal Cirrhinus mrigala and three exotic carps: silver carp Hypophthalmichthys molitrix, grass carp Ctenopharyngodon idella) and common carp Cyprinus carpio was carried out in Nasti baor (oxbow lake) for the harvesting season from August to December 1995. The length-weight relationship for six carp species was established for the harvesting months of November and December 1995. The b values for different species respectively for the months of November and December were 2.95 and 2.58 for rohu, 3.06 and 2.98 for catla, 2,84 and 2.90 for mrigal, 2.75 and 2.60 for silver carp, 2.51 and 1.97 for grass carp and 2.38 and 2.50 for common carp. In CPUE study, the CPUE was 0.58 kg/ha/hr while the catch per gear was 0.08 kg/ha/hr/purse-seine. The recovery percentage of mrigal was highest (63.57%) and it was lowest (16.81%) in case of silver carp. The density of submerged macrophytes (Hydrilla, Utricularia, Ceratophyllum and Vallisneria) was highest (4.39 kg/sqm) in November and was lowest (0.76 kg/sqm) in September.

Effect of thyroxine on hatching and on postembryonic growth in Brachydanio rerio, Cyprinus carpio, Labeo rohita, Cirrhina mrigala and Catla catla

Studies on the effect of thyroxine on the eggs and postembryonic growth of Brachydanio rerio, Cyprinus carpio, Labeo rohita, Cirrhina mrigala and Catla catla have been carried out. The treatments were given in the dosages ranging from 0.025 to 0.20 mg. Lower doses of 0.025 to 0.075 mg were effective in reducing the hatching period, accelerating the yolk absorption and improving the growth of postembryonic stages in case of all the five species. Higher doses of 0.15 to 0.20 mg were found to reduce the survival significantly in B. rerio, C. carpio, L. rohita and C. mrigala.

Toxicity of copper sulphate on some haematological parameters of a freshwater teleost Cyprinus carpio var. communis

Haematological changes in a freshwater teleost, Cyprinus carpio var. communis, exposed to acute and sublethal toxicity of copper sulphate were studied. During the acute treatment, erythrocyte and leucocyte count, and haemoglobin content increased, whereas during the sublethal treatment, erythrocyte count and haemoglobin content decreased and leucocyte count increased.

Responses of plasma transaminase activity in Cyprinus carpio var. communis to mercury toxicity

The present study reports the behavioural and enzymological responses in a freshwater teleost fish, Cyprinus carpio var. communis, exposed to acute and sublethal toxicities of mercuric chloride. During acute treatment, significant behavioural changes like erratic swimming, excess mucus secretion and increased opercular movements were noticed. During acute and sublethal treatments, both aspartate amino transferase and alanine amino transferase activity increased throughout the study period. Comparing the treatments, the changes in enzyme activities were found high in acute treatment and all the values were significant at 5% level. The above findings can be used as non-specific biomarkers of environmental pollutants.

Responses of Cyprinus carpio var. communis to Cyhalothrin, a pyrethroid insecticide

Haematological and biochemical profiles in a freshwater teleost, Cyprinus carpio var. communis, exposed to sub-lethal toxicity of the insecticide cyhalothrin were studied. During the treatment, erythrocyte count, haemoglobin content and protein content decreased, whereas leucocyte count and glucose level increased. The data are discussed in relation to the significance of haematological and biochemical changes as non-specific biomarkers against anthropogenic stress.

Management of the nile perch, Lates niloticus, fishery in Lake Victoria in light of the changes in its life history characteristics

Nile perch, Lates niloticus Linnaeus, 1758, is a predatory fish of high commercial and recreational value. It can grow to a length of 2 m and a weight of 200 kg. In Uganda, Nile perch was originally found only in Lake Albert and the River Nile below Murchison Falls. The species is, however, widely distributed in Africa, occurring in the Nile system below Murchison Falls, the Congo, Niger, Volta, Senegal and in Lakes Chad and Turkana (Greenwood 1966).

Species interaction between carp species in polyculture system

A three months experiment was conducted to study the species interactions of two carp species in polyculture system under supplemental feeding. Four species of fishes such as silver carp (Hypophthalmichthys molitrix), mrigal (Cirrhina cirrhosus), catla (Catla catla) and common carp (Cyprinus carpio) were cultured in four different combinations each containing two species. The combination of silver carp and mrigal in treatment 1, and silver carp and common carp in treatment 2 resulted better growth and production than other two treatments of different combinations of catla and common carp, and catla and mrigal.

Growth and yield of GIFT (Oreochromis niloticus) and Thai silver barb (Barbodes gonionotus Bleeker) in rice fields and their effects on the yield of rice

(GIFT) (Oreochromis niloticus) and Silver barb (Barbodes gonionotus) in rice fields and their effects on the yield of rice was carried out in nine experimental rice plots. Three treatments viz., treatment-1 with 0. niloticus (T1), treatment-2 with B. gonionotus (T2) and treatment- 3 was kept as control (T3, without fish) were used in this study. Fertilizers such as, Urea (178 kg ha-1), T.S.P (125 kg ha-1) and M.P. (67 kg ha-1) were applied in each treatment. The fishes were stocked @ 6250 ha·1 and the experiment was continued for a period of 107 days. The values of water quality parameters such as, water temperature, dissolved oxygen, pH and chlorophyll-a were found within suitable level. Between the two species, higher specific growth rate was recorded in 0. niloticus than that of B. gonionotus. But B. gonionotus showed much higher survival (72%) than that of 0. niloticus (35%). Similar to survival, higher production (244 kg ha-1) and income (Tk. 6399 ha-1) were recorded in B. gonionotus than those of 0. niloticus (142.8 kg ha'1 and Tk. 2137 ha-1). Significant differences (pof rice grain and straw were observed between the treatments with fish and without fish.

Culture of Amblypharyngodon mola in rice fields alone and in combination with Barbodes gonionotus and Cyprinus carpio

A rice-fish culture experiment with four treatments viz., T 1 with Amblyphmyngadan mala alone, T 2 with A. mala and Barbodes gonionotus, T3 with A. mala and Cyprinis carpio and T4 as control (without fish) was carried out in the rice fields during April through August1999. The recovery rate of A. mala were 42%, 37% and 42% in treatments 1, 2 and 3 respectively and the same recorded for B. gonionotus and C. cmpio were 62% and 55% respectively. Among the three species of fish, B. gonionotus showed much higher recovery rate than both of A. mala and C. carpio. The production of A. nwla was 12.50 kg/ha/3 months in monoculture, and 7.92 kglha/3 months and 8.86 kglha/3 months in combination with B. gonionotus and C. carpio, respectively. The production of B. gonionotus in T2 was 169.29 kg/ha/3 months and C. cmpio in T 3 was 252.92 kg/ha/3 months. The total fish production was 12.50 kg/ha/3 months, 175.21 kg/ha/3 months and 261.88 kg/ha/3 months in Tp T2 and T3, respectively. The highest yields of rice grain (5.78 ton/ha) and straw (7.83 ton/ha) were recorded in T3 and the lowest of the same was in T4 (grain 4.96 ton/ha and straw 6.62 ton/ha). Rice yield increased by about 12.10% in T1, 13.30% in T2 and 16.33% in T3 in context to T4, rice-alone culture. The results demonstrated that the culture of fish in rice fields had profound beneficial impact on the production of rice grain and straw.

Determination of acute mercury toxicity to developing stages of Cyprinus carpio and Cirrhinus mrigala

Toxicity of inorganic mercury to different life history stages of fresh water fishes, Cyprinus carpio and Cirrhinus mrigala were demonstrated by static bioassays. 48 and 94% of egg hatching occurred in controls at 72 and 24h of experimentation in C. carpio and C. mrigala respectively. While fish eggs in water containing mercuric chloride showed delayed development as compared to the control. LC50, LC100 and safe concentrations of hatchling, fry and fingerling were calculated. Hatchling and fry were observed to be more susceptible as compared to fingerlings of C. carpio and C. mrigala.

Effects of stocking density on growth and production of GIFT (Oreochromis niloticus)

The study was carried out to assess the effects of stocking density on growth and production of GIFT for a period of 100 days. Three stocking densities were used 150, 200 and 250 fish/decimal; designated as treatment T1, T2 and T3 respectively having two replicates for each. Commercial pellet feeds were fed at the rate of 30% body weight up to first 10 days and then gradually it was readjusted to 22%, 18%, 15%, 12%, 10%, 8%, 6%, 5% and 4% respectively after every 10 days interval. The result showed that the fish in the treatment T1 stocked with the lowest stocking density (150 fish/dec) resulted in best individual weight gain (148.65g) followed by those in treatment T2 and T3 respectively. The specific growth rates (SGR) at every 10 days were ranged from 6.59 to 1.11 in different treatments during the experimental period. The food conversion ratio (FCR) values ranged between 1.82 to 2.03 with treatment T1 showing the lowest FCR. The survival rate ranged between 84 to 92%. Treatment T1 and treatment T2 showed significantly higher survival than Treatment T3. The fish production rate in treatment T1, T2 and T3 were 18.58, 23.87 and 26.78 kg/decimal respectively.

The biology, ecology and impact of the Nile perch, Lates niloticus in lakes Victoria, Kyoga and Nabugabo and the future of the fisheries

Nile perch (Mputa), Lates niloticus was introduced into Lakes Victoria and Kyoga from lake Albert to increase fish production of these lakes by feeding on and converting the small sized haplochromines (Nkejje) which were abundant in these lakes into a larger table fish. It was, however, feared that Nile perch would prey on and deplete stocks of the native fishes and affect fish species diversity. Nile perch became well established and is currently among the three most important commercial species. It is presently the most important export fish commodity from Uganda. Considerable changes have taken place in fishery yield, and in life history characteristics of the Nile perch itself since the predator got established in Lakes Victoria and Kyoga.