FISHERIES PT.3

Question 1

what is bycatch

Answer 1

portion of commercial catch caught unintentionally

Question 2

3 forms of bycatch

Answer 2

Excess catch of the target species
Catch of non-target fisheries species
Catch of non-fisheries species

Question 3

bycatch species

Answer 3

Mammals (MMPA)
sea birds
sea turtles

Question 4

effects of fisheries on benthos

Answer 4

Structure = habitat – decreases diversity

Question 5

gear used for Bottom contact fisheries

Answer 5

Trawls e.g. beam
Dredges e.g. scallop
Long lines

Question 6

what area do Bottom contact fisheries trawl

Answer 6

• Entire continental shelves - trawled every 4yrs
• Trawling to 3000m – now extending off shore

Question 7

impacts of Bottom contact fisheries

Answer 7

• Loss of structure forming organisms (both hard + soft substrates)
• Altered geochemistry of sediments – o2 from tube dwellers + nutrient cycling
• Reduced physical structures – loss of sediment, ripples, rocks etc
• Changes in species composition + decreased abundances
• Changes in infauna – increases in scavengers, species adapted to disturbance

Question 8

other types of sea bed disturbance other than fisheries

Answer 8

Natural disturbance
Storm waves
Currents
Icebergs
Large mammals
Mixing sediments

Question 9

similar effects that bottom trawling and clear cutting have

Answer 9

Remove biomass
Alter substrate
Eliminate late successional species
Release carbon

Question 10

differences between bottom trawling and clear cutting

Answer 10

bottom trawling:
- less time to recover
- more area covered globally
- public areas only

Question 11

Specific benthic habitats effected

Answer 11

• Cold seeps – chemosynthetic ecosystem
• Seamounts + canyons
• Slopes and shelves