Optimization of dose of methyltestosterone (MT) hormone for sex reversal in tilapia (Oreochromis niloticus L.)

This paper describes the optimization of dose of methyltestosteronei (MT) hormone for masculinization of tilapia (Oreochromis niloticus). Five treatments (i.e. T1 T2, T2, T4 and T5) with different doses such as 0, 40, 50, 60 and 65 mg of MT hormone were mixed with per kg of feed for each treatment and fed the fry four times a day up to satiation for a period of 30 days. The stocking density was maintained 10 spawn/liter of water. The growth of fry at different treatments was recorded weekly and mortality was recorded daily. At the end of hormone feeding the fry were reared in hapas fixed in ponds for another 70 days and at the 100th day the fish were sexed by the gonad squashing and aceto-carmine staining method. The analysis of growth data did not show any significant variation in length and weight of fish among the different treatments. High mortality of fry ranging 66% to 81.6% was observed in different treatments and highest mortality was observed during the first twelve days of the experiment. The sex ratio analysis showed that T2 (40 mg/kg) and T5 (65 mg/kg) produced 93.33% of sex reversed male and T3 (50 mg/kg) and T4 (60 mg/kg) produced 96.66% sex reversed male, and these ratios were significantly (p<0.05) different from 1:1 male: female sex ratio. The control, T1 (0 mg/kg) contained 43.33% male progeny. From these results it is suggested that either 50 mg/kg or 60 mg/kg of MT with a feeding period of 30 days could be considered as an optimum dose for masculinization of tilapia (O. niloticus).

Effect of gamma radiation in combination with freezing on the microbiological changes in frozen shrimp Penaeus monodon

In this study gamma radiation (3, 6 and 9 kGy) in combination with low temperature (-20°C) were applied to retain the quality and shelf-life of shrimp, Penaeus monodon for a longer period. The quality was assessed by monitoring microbiological changes (TBC, TMC, TYC, TCC and Salmonella count) in irradiated and non-irradiated (control) samples. Among microbiological indicators of spoilage, total bacterial count (TBC) values for irradiated shrimps were found to be 1875, 1625 and 1525 cfugˉ¹ of sample at 3, 6 and 9 kGy respectively after 90 days whereas for non-irradiated samples it was found 2475 cfugˉ¹ of sample. Total moulds count (TMC) value for non-irradiated samples after 90 days were found 425 cfugˉ¹ sample whereas that for irradiated shrimps at 3, 6 and 9 kGy were found to be 275, 250 and 200 cfugˉ¹ sample respectively. Total yeast count (TYC) value for non-irradiated samples after 90 days were found 4125 cfugˉ¹ sample whereas that for irradiated shrimps at 3, 6 and 9 kGy were found to be 2850, 2150 and 1725 cfugˉ¹ sample respectively. Total coliform count and Salmonella count showed that those were absent during 90 days storage period. From this study, it was clear that gamma radiation in combination with low temperature showed shelf-life extension (90 days) in each dose of radiation used but during the use of 9 kGy radiation, Penaeus monodon showed best quality.

Aquatic Vegetation, Largemouth Bass and Water Quality Responses to Low-Dose Fluridone Two Years Post Treatment

Whole-lake techniques are increasingly being used to selectively remove exotic plants, including Eurasian watermilfoil ( Myriophyllum spicatum L.). Fluridone (1-methyl-3-phenyl- 5-[3-(trifluoromethyl)phenyl]-4(1 H )-pyridinone), a systemic whole-lake herbicide, is selective for Eurasian watermilfoil within a narrow low concentration range. Because fluridone applications have the potential for large effects on plant assemblages and lake food webs, they should be evaluated at the whole-lake scale. We examined effects of low-dose (5 to 8 ppb) fluridone applications by comparing submersed plant assemblages, water quality and largemouth bass ( Micropterus salmoides ) growth rates and diets between three reference lakes and three treatment lakes one- and two-years post treatment. In the treatment lakes, fluridone reduced Eurasian watermilfoil cover without reducing native plant cover, although the duration of Eurasian watermilfoil reduction varied among treatment lakes. (PDF has 11 pages.)

Evaluation of SP1001 (Pelargonic Acid) in Combination with Glyphosate on Cattail and Alligatorweed

Cattail (Typha latifolia L.) is a common and troublesome weed in shallow, freshwater environments throughout the United States. Alligatorweed (Alternanthera philoxeroides (Mart.)Griseb.), in spite of the introduction and success of several insects as biological controls, remains a troublesome we4ed in a a number of locations in the Southeast where there are frequent human disturbances (e.g., insecticide spraying, mechaniceal removal, etc.) and/or weather conditions that affect the life cycle of the insects (Kay1992, Vogt et al. 1992). Both of these weeds routinely are managed by foliar applications of the herbicide, glyphosate [N-(phosphonomethyl)glycine]. Regrowth and reinfestation of previously treated areas usually necessitates additional herbicide application during subsequent years. A new product that could enhance the activity of glyphosate on these weeds would be useful in their management. In 1997, SePRO Corp. initiated t4esting of an experimental compound, SP1001, to determine its efficacy either as a herbicide or as an adjuvant to boost the activity of glyphosate for use in aquatic sites. The objective of this study was to evaluate the potential for using SP1001 as an adjuvant to replace surfactants customarily used during application of glyphosate for control of cattail and alligatorweed.

DNA extraction from formalin-fixed Franciscana tissues

The present paper reports the extraction of DNA from formalin-fixed Pontoporia blainvillei tissues. Following the Vachot and Monerot (1996) protocol, fragmented DNA (300-700bp) was extracted from more than 95% of liver and muscle samples. DNA yield in liver samples was significantly higher than in muscle samples (4.574 ± 1.169mg DNA/mg versus 0.808 ± 0.297mg DNA/mg). Similar results were obtained from nine other species of cetaceans and five species of pinnipeds. It is of special interest to have a method that allows the utilisation of museum specimens not originally preserved for genetic studies, which may include rarely available, declining or extinct species. SPANISH: El presente trabajo reporta la extracción de ADN a partir de tejidos formolizados de Pontoporia blainvillei. Siguiendo el protocolo de Vachot y Monerot (1996) se pudo extraer ADN degradado (300-700pb) en más del 95% de las muestras de hígado y músculo analizadas. El rendimiento en ADN fue significativamente mayor en muestras de hígado que en muestras de músculo (4.574 ± 1.169mg DNA/mg tejido húmedo versus 0.808 ± 0.297mg DNA/mg tejido húmedo). Resultados similares se obtuvieron en otras nueve especies de Cetáceos y cinco de Pinnípedos. Resulta de gran interés contar con un método que permita la utilización de especímenes depositados en museos y que no hayan sido originalmente colectados para estudios genéticos, incluyendo especies de difícil obtención, en franca declinación o extintas.

Disinfection of aquarium effluents by chlorination and UV treatment

The study was conducted to investigate the efficacy of chlorine and UV irradiation in disinfecting aquarium effluent. A non-agglutinating, a virulent strain of Aeromonas salmonicida (NCIMB 11 02) was used as the test organism. Effluents from a fish tank were inoculated with a suspension of test organisms and subsequently treated with different concentrations of hypochlorite and UV irradiation separately and simultaneously. When used alone, 1.0 ppm hypochlorite reduced the viable cell count from 6.5 log to 3.0 log within 20 minutes of contact period. On the other hand, when used in combination with UV irradiation only 0.5 ppm hypochlorite exerted the same bactericidal effect within the same contact period as was observed with 1.0 ppm hypochlorite alone. This result indicated that required dose of disinfectant for the disinfection of aquarium effluents can be considerably reduced when it is used in combination with UV irradiation.

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.

On the comparative efficiency of trawls made of cotton, polyethylene and combination of both the materials

The merits and demerits of cotton, polyethylene and combination of the two materials ascertained on the basis of cost, wear and tear, maintenance, total catch and qualitative analysis of the catch are discussed by making comparative fishing experiments with the three trawl gears made of these materials. The study can be concluded with a suggestion for switching over to polyethylene twisted monofilaments for better, in case of bottom trawls without in any way adversely affecting the catch of shrimps and at the same time for enhanced fish catch. Even though the combination net is found to be equal in efficiency as the polyethylene net this idea cannot be conveniently adopted from the point of view of economy.

Import substitution of combination wire rope. Part 1. Design, production and evaluation of a prototype combination wire rope

Model combination wire ropes with different covering materials were prepared and worked out specification for the prototype. A table model hand operated wire rope twisting machine was also developed for this. Prototype combination wire rope was twisted in collaboration with M/s South India Wire Ropes Ltd., Alwaye. Specification details, properties and field performance of the prototype studied are reported.

Import substitution of combination wire rope. Part 2. Production and standardisation of 17 mm dia combination wire rope.

The prototype combination wire rope (Cift-CWR 1) developed for deep sea trawling was further studied for improvement, optimisation of efficiency and standardization. A series of improved prototype combination wire ropes (Cift-CWR 2 to 6) were twisted and evaluated their mechanical properties and reported in this paper with recommendations for a standard 17mm dia combination wire rope of 6S (7C+8+1 Scr) + 6 Crs(6+1+1 Crc) construction.

Import substitution of combination wire rope. Part 3: Comparison of standard Cift-CWR and imported combination wire rope

Tensile and extension properties of standard Cift-CWR and imported combination wire ropes from Japan, Norway and Denmark are studied and the analysis is presented in the paper. Tensile and chemical properties of steel wire, tensile and abrasive properties of PP covering, effect of twist on material at different stages are worked out and reported.

Effects of gamma radiation and freezing on the chemical and sensory changes in shrimp Penaeus monodon (Fabricius, 1978)

Gamma radiation (3, 6 and 9 kGy) in combination with low temperature (-20°C) were applied to retain the quality and shelf-life of shrimp, Penaeus monodon for a longer period. The quality was assessed by monitoring the chemical (TVN, TMA) and sensory changes in irradiated and non-irradiated (control) samples. Among chemical indicators of spoilage, total volatile nitrogen (TVN) values for irradiated shrimps were found to be 2.26, 2.18 and 1.57 mg N/100g of sample at 3, 6 and 9 kGy respectively after 90 days whereas for non-irradiated samples it was found 2.45mg N/100 g of sample. Trimethylamine (TMA) value for non-irradiated samples after 90 days were found 2.30mg N/100 g sample whereas that for irradiated shrimps at 3, 6 and 9 kGy were found to be 2.10, 2.08 and 1.98 mg N/100 g sample respectively. The sensory scores of control sample were gradually decreased with the progress of storage period. From this study, it was clear that gamma radiation in combination with low temperature showed shelf-life extension (90 days) in each dose of radiation used but during the use of 9 kGy radiation, P. monodon showed best quality.