Fisheries

Question 1

What is the cryosphere?

Answer 1

The frozen water part of the Earth system

Question 2

Difference between Antartica and Arctic with regards to sea ice?

Answer 2

Antarctica
Open ocean allows the ice to move freely
Sea ice tends to be covered by a thicker layer of snow

Arctic
Sea ice is enclosed in the middle.

Question 3

Global temperature change enhanced at the poles

Answer 3

In the arctic we see the a 6-7 degree projected increase

Antarctica 2-3 degrees

Question 4

Sea ice as

Answer 4

A feeding ground

A substitute to land for reproduction

Question 5

Ecological consequences of sea ice decline

Answer 5

Alteration of food web
Habitat loss
Extinctions

Question 6

Sea ice decline and alteration of food web

Answer 6

Antarctic Krill
Feed primarily on phytoplankton
Habitat for larvae/ juvenile is sea ice

Walruses use sea ice…
As a platform for feeding
Sea ice = drifting platform (away from habitat)
Problem in accessing feeding areas

Question 7

It was originally thought that the small, short-lived species were less vulnerable to fishery pressures, therefore biologists advise higher harvest rates for these species…BUT

Answer 7

These species collapse just as often as species with slower life histories.

Question 8

Why might a fast life history increase vulnerability to collapse?

Answer 8

Populations of short lived species can grow or decline quickly in response to climatic shifts, and a rapid decline in productivity often requires similarly rapid reductions in fishing efforts.
If fisheries management lags behind these biophysical changes, a population can be driven to collapse.

Question 9

Note that environmental variability alone can drive variation in fish abundance. For example…

Answer 9

Short lived species may be particularly sensitive to such environmental variability because of their fast growth rates and short generation times.
Longer lived you have a more adaptive buffer to seasonal shifts.

Question 10

Even though short lived species may recover more q quickly from collapse than other fishes…

Answer 10

Collapses in small, low trophic level species can last from years to decades- cascading effects.
These durations are long enough to have substantial impacts on the food web.
MEANWHILE- the taxa are moving

Question 11

Why are marine species better able to keep pace with climate change than terrestrial species?

Answer 11

Marine species may shift more rapidly than species on land because they face fewer barriers to dispersal.

Question 12

What can rapid range shifts do to marine communities?

Answer 12

Fundamentally reorganise them- climate induced movements of highly commercial species have already sparked cross border dishes conflicts and they can confound traditional management approaches.
Species with restricted ranges easier to fish out.