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Not AvailableExperimental bottom trawling was conducted from MFV Sagarkripa at five transects of water depths 15-20 m, 21-25 m, 26-30 m, 31-35 m and 36-40 m in commercial trawling grounds to assess the impact of bottom trawling on the epifauna off Veraval coast. Trawling was conducted for 17 months in a span of 20 months (September 2005-April 2007) excluding the trawl ban period (June to August). Altogether 41 species of gastropods, 1 species of scaphopod, 19 species of bivalves, 3 species of crab, 3 species of shrimps, 2 species of Balanus, 1 species of stomatopod, 4 species of finfishes, 2 species of brown algae and 4 species of octocorals were identified. The soft corals found were Litophyton sp. and Studeriotes sp. (Christmas tree soft coral). The gorgonians collected were young stages of Subergorgia suberosa and Juncella juncea (Whip coral). The presence of octocorals recorded in the month of October, immediately after the closed season (June to August) when the sea bottom is not heavily trawled suggests that this area is an abode of corals and a favourable site for coral reef formation. But intense trawling in the succeeding months destroys these valuable entities of ecosystem and the samples were not encountered in the subsequent months. The changes before and after trawling in biodiversity indices were significant at 15-20 m. The abundance-biomass curve showed that the rate of stress increased with water depth. The shallow depths are lightly trawled due to intermittent rocky nature of bottom and as water depth increases, the trawling intensity increases. The analysis of similarity of percentages in Simper showed that the dissimilarity of fauna before and after experimental trawling was more evident in lightly trawled area and remained masked in heavily trawled area. Suggestions are made for the promotion of eco-friendly gears and for conducting studies on appropriate un-trawled control sites for comparative assessment. Management strategies have to be adopted for the conservation and biodiversity protection of octocorals.Not Availabl

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Not AvailableThe present communication is a study on the impact of bottom trawling on the sediment characteristics along Veraval coast, which is the largest trawler port of India. Experimental bottom trawling was conducted from MFV Sagarkripa at five transects of water depths 15–20 m, 21– 25 m, 26–30 m, 31–35 m and 36–40 m in commercial trawling grounds. Trawling was conducted for 12 months in a span of 15 months excluding the trawl ban period (June to August). The sediment texture was analysed by pipette analysis and organic matter by wet oxidation method. The variations in organic matter and sediment texture were prominent between the stations selected at different depths. The sedimentary organic matter exhibited variations with different water depths and seasons. The organic matter content decreased with depth. Experimental trawling considerably reduced the organic matter content at all depths. Continued and incessant trawling operation can cause even more drastic reductions, where organic matter content is already very small. The sand proportion showed depth-wise variation; but seasonal and trawling effect was not significant showing highest values at 36–40 m depth. The silt proportion did not exhibit significant depth-wise variation. The seasonal variation of silt was significant whereas trawling effect imparted to silt was not evident. Trawling has no significant effect on clay concentration. But seasonal variation had great influence on the clay distribution and indicated significantly high depth–season interaction. The sediment of the study area was predominant in silt proportion. It was observed that the seasonal/natural variations were more prominent masking the trawling effect on silt.Not Availabl

Fishing activities

Unlike the major anthropogenic changes that terrestrial and coastal habitats underwent during the last centuries such as deforestation, river engineering, agricultural practices or urbanism, those occurring underwater are veiled from our eyes and have continued nearly unnoticed. Only recent advances in remote sensing and deep marine sampling technologies have revealed the extent and magnitude of the anthropogenic impacts to the seafloor. In particular, bottom trawling, a fishing technique consisting of dragging a net and fishing gear over the seafloor to capture bottom-dwelling living resources has gained attention among the scientific community, policy makers and the general public due to its destructive effects on the seabed. Trawling gear produces acute impacts on biota and the physical substratum of the seafloor by disrupting the sediment column structure, overturning boulders, resuspending sediments and imprinting deep scars on muddy bottoms. Also, the repetitive passage of trawling gear over the same areas creates long-lasting, cumulative impacts that modify the cohesiveness and texture of sediments. It can be asserted nowadays that due to its recurrence, mobility and wide geographical extent, industrial trawling has become a major force driving seafloor change and affecting not only its physical integrity on short spatial scales but also imprinting measurable modifications to the geomorphology of entire continental margins.Fil: Oberle, F.K.J.. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias del Mar; EspañaFil: Puig, P.. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias del Mar; EspañaFil: Martín de Nascimento, Jacobo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin