what could be some negative effects of dredging?

Answer 1

Stirring up contaminants and putting them back in the ecosystem. PCBs mainly come to mind.

Answer 2

Effects of Trawling and Dredging


“Habitat alteration by the fishing activities themselves is perhaps the least understood of the important environmental effects of fishing” (National Research Council, 1994).

The use of mobile fishing gear has become a source of concern because of the size of the affected fishing grounds, the modification of the substrate, disturbance of benthic communities, and removal of nontarget species. The long-term viability of some fish populations could be threatened if essential fish habitat is degraded. Also, because of declines in many traditional fisheries, efforts to find under-exploited fish populations have increased interest in exploiting less accessible, previously unfished areas. These efforts have been facilitated by the development of new gear and navigational aids. Extensive new regions of the continental shelf, slope, submarine canyons, and seamounts have been exposed to the effects of bottom trawling and dredging. Expansion of fishing into new territory could lead to the loss of habitats that might have provided as refuge for heavily exploited species.

Since the publication of the 1994 National Research Council report, there has been additional research on the effects of fishing gear, especially trawls and dredges, on marine benthic habitats. The magnitude depends on gear configuration, on the subtle modifications various operators make to their gear and on the many and varied habitats fished. Given the inherent difficulty of studying offshore habitats and the problems associated with determining causation under shifting environmental conditions (current, temperature variation, natural migration, storm activity), not all questions regarding the effects of fishing on the seafloor have been answered—nor are they likely to be in the near future. Evaluating the effects of bottom trawling on benthic communities is complicated by the sparseness of data on species abundance and composition before intensive bottom fishing began. This is important because recent analyses of the few existing historical data sets suggest that larger bodied organisms (fish and benthos) were more prevalent before intensive bottom trawling began (Frid and Clark, 2000; Greenstreet and Hall, 1996). Existing studies necessarily indicate changes relative to recent conditions, not changes relative to the less disturbed ecosystem. There has been an increase in the understanding of fishing gear and habitat interactions that can be used for making decisions about habitat management.

Answer 3

Mostly it could reduce flooding and keep the river in its banks. When the flooding takes place u get things into our water system that are very bad.