Dredging Impact on Fish Stocks

Ray Drabble has just had the following news article published in Marine Pollution Bulletin. His efforts to get this on the agenda for Coastal Futures sadly failed. Similarly MMO and CEFAS have been very dismissive about considering fresh evidence that challenges their stated position.

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Strategic Scoping Report and dredging effects

The U.K. Marine Management Organisation (MMO) published its updated Strategic Scoping Report for marine planning in England (SSR) in August, an important tool to assist the marine planning process. However, its claim to incorporate best available evidence merits further examination with respect to one sector, Marine Aggregate Extraction. The SSR explains that the footprint of dredging activity is typically only 10–15% of the licensed areas; however, open access track data shows the footprint of dredging activity extends beyond both the dredge zone and the licence area. Electronic Monitoring System (EMS) data that is used to record and regulate dredging activity under-estimates by an order of magnitude the effect of entrainment as it fails to register when dredgers are operating dredge pumps above the seabed when turning or fluidizing the cargo.

The basic process of trailer suction dredging around U.K. coasts has evolved little over the past 50 years and removes not only gravel, but most fish and other animals along with it, especially juveniles. This affects a number of important food species, including scallops, plaice and sole. Financial estimates based upon published research into dredging impacts in the Eastern English Channel using the industry’s own data (See Mar. Poll. Bull. 64, 2, 363–372) show the by-catch of scallops alone is estimated to be 595 tonnes with an equivalent value of £238,000. In a given year, the volume of material dredged for the purposes of mineral extraction can be doubled by sediment removed from ports and harbours and their approach channels; the overall scale and cost of fish by-catch from dredging is estimated to be equivalent to 7% demersaldemersal Living on the seabed by-catch from England and Wales at a value of between £6 and £9M.

Of potentially far greater concern is the longer-term impact on the ecosystems from the loss of marine life from all levels in the food chain through dredging, the scale of which has not been measured. Notwithstanding the weight of evidence, fish by-catch is not regarded as a significant concern by the industry or its regulators. Without the rigorous pursuit of best scientific evidence, enforced by government regulators, there is a risk that licence monitoring becomes a tick box exercise rather than offering a high degree of protection to the environment.

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Ray’s article reminded me of an instance a few years ago when I spied a great swirl of noisily screaming excited gulls descending on a very large heap of marine aggregate just landed from a dredger on Great Yarmouth Quayside for the purpose of building a new bridge crossing over the Yare. Anxious to investigate the reason for the gull’s excitement, I took a sample bucket full to determine the content, which as well as gravel proved be a mass of immature fish, mainly dabs, plaice, flounders, sea urchins, shellfish, starfish, and even a large turbot and other flatfish of eatable size. Had a fisherman had landed such a catch, he would surely be in deep trouble with the authorities.

PG 15/11/13

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