Dredging

About: Dredging is a research topic. Over the lifetime, 3300 publications have been published within this topic receiving 28325 citations.

Evaluation of shell damage to the clam Chamelea gallina captured by hydraulic dredging in the Northern Adriatic Sea

Abstract: The impact of experimental hydraulic dredging was assessed on Chamelea gallina populations in two sites along the north-western Adriatic coast (Lido and Jesolo) by detecting and quantifying shell damage caused by fishing operations on both captured and discarded clams. Various levels of stress were applied, the highest being that used by commercial fishing vessels, which employ high water pressure and mechanised sorting and the lowest manual sampling of clams by scuba divers. Water pressure and sorting significantly increased shell damage, the highest levels always being observed in commercially dredged clams. At Lido, damage was mostly due to the action of the mechanised sorter; at Jesolo, the effect of high water pressure was more clearcut. Moreover, clams collected at Jesolo had both higher mean damage level and higher numbers of damaged individuals compared to the Lido samples. These differences seem to be mostly related to differing bottom features in the two sites. A positive relationship was observed between damage level and clam size: small-sized samples (length <17 mm) were less damaged than medium-sized ones (25 mm < length < 17 mm) and commercial size clams (<25 mm) showed the highest damage level. The severe and harmful physical impact of hydraulic dredging was apparent in captured and then discarded animals, a small fraction of which appears able to recover, as shown by the presence of clams with repaired shells. 2003 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights

Remote-sensing monitoring for spatio-temporal dynamics of sand dredging activities at Poyang Lake in China

Abstract: As the largest freshwater lake in China, Poyang Lake is suffering from declining water quality related to the excessive dredging of sand. Field supervision is difficult due to the size of the lake (>3000 km2, wet season) and limited human resources. In this study, an approach is proposed to monitor sand-dredging activities using medium-resolution optical remote-sensing imagery, including 45 Landsat TM/ETM+ images from 2002 to 2012 and 140 HJ1A/B CCD images from 2009 to 2012. The procedure for detecting dredging vessels involves three steps. (1) The entire image is segmented into different homogeneous partitions to overcome water body heterogeneity, and ships in each partition with different levels of water clarity are detected using three types of contrast box architecture. (2) Dredging vessels are then identified based on a spatial overlay analysis of ships and dredging plumes, which are extracted from remote-sensing imagery. (3) False alarms (FAs) of dredging vessels are screened according to the distri...

Patterns of succession in benthic infaunal communities following dredging and dredged material disposal in Monterey Bay

Abstract: : This report deals with the patterns of benthic succession in soft-bottom marine communities. The primary study objective was to elucidate and evaluate the mechanisms that control these patterns. Benthic succession is the pattern of community recovery following a perturbation. Controlled perturbations of bottom communities were effected by the dredging of locations in Moss Landing Harbor and by the disposal of dredged material in Monterey Bay, Calif. The general pattern of succession was highly dependent upon the nature of the physical environment and the structure of surrounding communities. The open coast communities of Monterey Bay are numerically dominated by small crustaceans and polychaetes. Succession was divided into an early and a late phase. The early phase was characterized by the immigration of peracarid crustaceans and the settlement of the larvae of relatively opportunistic species of polychaetes. The latter have relatively short generation times, small size, low fecundity and high larval availability (frequency and abundance of larve in the water). These opportunistic are uncommon in the natural, undisturbed bottom community. The later phase of succession was characterized by the gradual reestablishment of the less mobile crustaceans and less opportunistic polychaetes that inhabited the areas prior to the experimental distrubances. It was concluded that the management of benthic marine resources and dredging operations should involve an analysis of the natural distrubance regime at a potential dredging or disposal site and its relation to the associated bottom communities.