EEB202H1 : Marine biology.docx
14 Apr 2013
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Document Summary
Bycatch- animals that are accidentally caught while fishermen are trying to capture something else. Reasons for being caught in net: curious, attracted to large fish, don"t notice net, not understanding danger, 20,000,000 tonnes, 25-40% total global catch in a single year bycatch. There are two types of nets: still nets- stationary. Weir- moderate bycatch, but porpoise common among herring weirs. V-shaped fence- like structures that channel fish in a pen dug in a riverbed. Gill nets- fish trapped by gills when they try to force through net. Pingers were developed in canada and are acoustic beacons that emit and intermittent, short, high pitched noise which are attached along nets to prevent marine mammals from being trapped. Expensive, scare away fish, get use to and ignore. Mammals particularly threatened are: harbour porpoises(north american coastline), north atlantic right whale (the bay of fundy), humpback whale (newfoundland: mobile nets- moving.
