Lecture 1 Flashcards
What is the demersal zone of the sea?
Any body of water near or interfacing with the sea bed
What is the pelagic zone of the sea?
Anywhere in the water column but not the seabed
What is the oceanic zone of the sea?
Where the continental shelf starts and out too sea. Deep sea
What is the epipelagic zone of the sea?
Water from 200m to the surface
What is the benthic zone of the sea?
Sea bed/under the sea bed
Where are industrial fisheries mostly contained to?
Continental shelf and areas of sea from land out to 200m
What are the 2 types of fisheries?
Benthic/demersal and pelagic
What are the largest environmental concerns of industrial fisheries?
Over exploitation and by catch
What is the average size of industrial vessels?
20 gross tonnes. 10-15m in length
What are the 2 approaches of fishing?
Active and passive
What is active fishing?
Gears moved through water to catch e.g. Trawler
What is passive is fishing?
Entanglement in nets or entrapment in static pots/nets
What are the 3 classifications of fisheries?
Inshore, pelagic and deep water
What are the 3 classifications of teleost fish?
Round, flat and white fish
What were nets historically made of?
Hemp
What are nets now made of?
Monofilament
What are net holes measured on?
EEC net gauge
What is the main process of trawling?
Large beam dragged across seabed.
How does trawling net select for different fish?
Through net gauge and habitat
What are the negative effects of trawling?
Destructive to seabed.
High amounts of by catch
Fuel demanding
How does netting work?
Vertical panels of nets
What are the 3 different types of netting?
Set nets
Encircling
Purse seining
What is long lining?
Long line with lead at the bottom to sink. Use of snap hooks
What is potting an example of?
Passive fishing
How does potting work?
Selective opening size, escape doors.
Pots set on strings and left for 2-3 days
What did frederiksen 2004 find?
Population numbers of black legged kittiwakes decline by more than 50% where Sandeel fishery was active. Need to monitor effects of fisheries on seabirds
What did Rice 1989 find?
Active fishing tends to remove adults from the population and enhance whether the set or survival of juveniles
What did Barko 2004 find?
High percentage of sea turtles died from passive fishing ethnic yes. Main factors influencing mortality was the depth of net deployment.
What did Hinz 2009 find?
Otter trawl impacts are cumulative and can lead to profound changes in benthic communities which can have implications for marine food webs
What did Griffiths 2010 find?
Pelagic longline fisheries often catch incidentally large apex predators which causes potential disruption to the ecosystem if the predators exert strong top down control
