Dredging Harbours?

[Drew]

As mentioned in a previous topic, Donaghadee harbour is currently being dredged, this is the first time I've seen this done down here and I'm not sure how it's going to effect the fishing.

Does anyone know how dredging effects the fishing generally?

Any advice is welcome.

Will maybe head down and take pics today.

[shamoo0804]

I guess there are a few different ways you can look at it.

It may scare the fish off, and may even ruin the sea bed in terms of the habitat of worms, small crustaceans etc.

Alternatively it could be stirring up the bottom bringing out lots of small food items for whatever resident fish there are, and with the outgoing tide, it could be creating a "slick" which may attract fish from further out into the harbour.

I dont have any personal knowledge of the dredging of harbours, nor do I know of any scientific evident that will assit your question, the above it just what came to mind when I read your post.

[The Austrian]

Dredging activities have the potential to change the environment.
At the sites of dredging and disposal the seabed and associated communities are disturbed and for some distance, suspended sediment may cause turbidity in water and increased sedimentation on the bottom.
It also effects water quality.
Depending upon the nature of the dredged material, its disturbance from the sea bed may lead to changes in the chemical composition of the water. Eg. many toxicants such as heavy metals and organic contaminants tend to stick to particulate matter and sink to the sediment. Some of these contaminants are very persistent in the sediment and some may change their oxidation state during burial, which alters their solubility. If these sediments are disturbed, the contaminants can be released to the water column and affect marine life.
and last, but by no moeans least, it effects human health.
As well as toxicants, the nutrient elements, particularly nitrogen and phosphorus, which control the rate of marine plant growth can also be released from sediments during dredging, with a risk of triggering algal blooms. Not only nutrients are important here - many of the toxic algal species, which are a health risk for consumers of shellfish, have a resting stage (cyst) which lies in the sediment. If dredging disturbs these cysts when conditions are favourable, a bloom of toxic algae may be caused.
Another biological risk from dredging involves the transport of species in dredgers from one port (or even country) to another. Exotic marine pests are now recognised as a major environmental concern and steps must be taken to minimise their transport to new environments.
So, as you might have gathered by now, I'm not a big fan of it... beneficial to a few, detrimental to most of us. The usual 'excuses'... and noone really cares...

[Drew]

Thanks for the info man. There goes the neighbourhood.