NOPR Community:

Toxicity of Hg (II) to prawns Penaeus monodon and Penaeus indicus (Crustacea: Penaeidae) from Rushikulya estuary, Bay of Bengal

2009-05-29T16:30:40Z

Title: Toxicity of Hg (II) to prawns Penaeus monodon and Penaeus indicus (Crustacea: Penaeidae) from Rushikulya estuary, Bay of Bengal Authors: Das, Snehalata; Sahu, B. K. Abstract: Penaeid prawns belonging to size 35-55 mm TL and 55-75 mm TL were exposed to the five concentrations of Hg (II) in salinities 5, 15, and 25 ‰. The values of LC₅₀ with 95% confidence limitfor 96 hours were 0.036 (0.032-0.041) and 0.042 (0.036-0.044) mg l^-1 for large size groups of P. monodon and P. indicus respectively. The LC₅₀ decreased with increase of time period. Small size groups were more sensitive to mercury at lower salinities while large size groups were more tolerant at high salinities. Penaeus monodon was more sensitive to mercury than P. indicus at each salinity. Threshold limit for P. monodon and P. indicus was 0.016 and 0.024 mg l^-1 respectively. Page(s): 337-339

Effect of ultraviolet-B radiation on biochemical composition of three Ulva species (Chlorophyta) from southeast coast of India

2009-05-28T16:30:36Z

Title: Effect of ultraviolet-B radiation on biochemical composition of three Ulva species (Chlorophyta) from southeast coast of India Authors: Eswaran, K.; Ganesan, M.; Periyasamy, C.; Rao, P.V. Subba Abstract: The young plants of Ulva fasciata, U. reticulata and U. lactuca were subjected to UV–B (320-280 nm) radiation for 30, 60, 90, 120, 150 and 180 min. The changes in chlorophylls, carotenoids, protein, nitrate contents and reductase activities were studied. Compared to control, in UV exposed plants both pigments and protein concentrations were significantly decreased. The magnitude of such decrease was higher in Ulva lactuca than in other two species. In contrast to this in vitro nitrate reductase activity was more severely affected in Ulva reticulata. The experiments clearly showed that the UV (A & B)-B radiation has a strong inhibitory effects on biochemical properties in all three Ulva species. However, the rate of inhibition is dependent on the duration of exposure of plants to UV (A & B)-B radiation. Page(s): 334-336

Gill net selectivity studies for fishing frigate tuna, Auxis thazard Lacepede (Perciformes/Scombridae) in Thoothukkudi(Tuticorin)waters, southeast coast of India^*

2009-05-27T16:30:48Z

Title: Gill net selectivity studies for fishing frigate tuna, Auxis thazard Lacepede (Perciformes/Scombridae) in Thoothukkudi(Tuticorin)waters, southeast coast of India^* Authors: Jude, D.; Neethiselvan, N.; Gopalakrishnan, P.; Sugumar, G. Abstract: Auxis thazard form commercial fishery in Thoothukkudi coastal waters from June to October in big meshed drift gill nets with the mesh size ranging from 60 to 100 mm. The fishery is mainly constituted by the length group 275-500 mm. The present study deals with the estimation of mesh size to capture the commercially significant length group (326-400 mm) of A. thazard and its enmeshing pattern in gill nets with two different mesh sizes. The optimum mesh size for the exploitation of the commercial significant size group of A. thazard from Thoothukkudi coastal waters is estimated as 84 mm. As the length at first maturity of this species in Thoothukkudi coast varied from 300 to 310 mm, the nets with proposed mesh size would reduce growth and recruitment over fishing of A. thazard in this coast and allow for spawning before first capture. Though the big meshed drift gill net fishery of Thoothukkudi coast is multi species oriented, the study emphasises the need to regulate the mesh size of the nets based on the type of fishes that form fishery and fishing seasons. It is recommended to conduct big meshed gill net fishing from June to October with the nets having the mesh size of 84 mm,as A.thazard is the major contributor to the big meshed gill net catch during this season. The use of gill nets with the 60 mm-mesh size should be banned during this season, as this would result in capturing of juveniles of A.thazard leading to growth overfishing. Page(s): 329-333

Imposex in rock whelks Thais and Ocenebra species (Mollusca, Neogastropoda, Muricidae) from Gujarat coast

2009-05-28T16:30:36Z

Title: Imposex in rock whelks Thais and Ocenebra species (Mollusca, Neogastropoda, Muricidae) from Gujarat coast Authors: Tewari, A.; Raghunathan, C.; Joshi, H. V.; Khambhaty, Yasmin Abstract: Imposex in Thais bufo, T. rudolphi, T. tissoti and Ocenebra bombayana was observed from Saurashtra coast of Gujarat. The maximum percentage of imposex out of total sample size (44.80 and 46.55%) were observed at Porbandar in T. bufo and T. rudolphi respectively while T. tissoti and O. bombayana at Mahuva showed 10.29 and 9.72% of imposex respectively. The percentage conversion of potential females to imposex was minimum at Diu and maximum at Porbandar. The number of ships operated from Porbandar and Diu directly correlated with severity of CPFII and percentage of imposex at these places. The results indicate that severity of imposex in T. rudolphi could be utilized as a bioindicator of TBT contamination in the marine environment. The Relative Penis Size Index(RPSI) ranged from 3.24 at Veraval to 16.50 at Porbandar in T. bufo while in T. rudolphi it ranged from 44.26 at Okha and 55.96 at Veraval. It was 21.19 and 14.26 for T. tissoti and O. bombayana respectively. The results indicate that RPSI may not be a foolproof indicator of severity of imposex in these organisms. Therefore a new index has been developed which is termed as Conversion of Potential Females to Imposex Index (CPFII) to calculate the potential females of a given area of a population. It seems the causative agents in seawater is neither toxic nor growth inhibitory at all the places of study but it interferes with the reproductive mechanisms and morphogenesis in these four species. The imposex in these organisms and its relation to TBT concentration in the marine environment is discussed. Page(s): 321-328

NOPR Community:

Toxicity of Hg (II) to prawns Penaeus monodon and Penaeus indicus (Crustacea: Penaeidae) from Rushikulya estuary, Bay of Bengal

Effect of ultraviolet-B radiation on biochemical composition of three Ulva species (Chlorophyta) from southeast coast of India

Gill net selectivity studies for fishing frigate tuna, Auxis thazard Lacepede (Perciformes/Scombridae) in Thoothukkudi(Tuticorin)waters, southeast coast of India*

Imposex in rock whelks Thais and Ocenebra species (Mollusca, Neogastropoda, Muricidae) from Gujarat coast

Gill net selectivity studies for fishing frigate tuna, Auxis thazard Lacepede (Perciformes/Scombridae) in Thoothukkudi(Tuticorin)waters, southeast coast of India^*