Oceans and Fisheries

1
Oceans and Fisheries

• Chapter 13 part 2

2
Oceans and Climate

• High Heat capacity
• Good heat storage acts as buffer
• Store and cycle chemical elements
• Major storage of carbon

3
Ocean Food Webs (food)

• Planktonic (phyto, zoo, etc..)
• Require light, O2 and nutrients.
• So most occur on continental shelves

4
Ocean food webs 2

• Intertidal
• Attached algae (kelp)
• Important in life cycles of fish and shellfish.
• Food, value, endangered, diverse.

5
Ocean food webs 3

• Choral reef
• Corraline algae and symbionts
• Major habitat for diversity

6
Fisheries

• Most from oceans.

7
Fish in diets

• 6.6 in North America
• 9.7 in Europe
• 21.1 in africa
• 8.2 latin america
• 27.8 in far east
• 21.7 in Central asia

8
History

• Marine take
• 1989 - 86 million tons
• 1993 - 84 million tons
• Total increasing due to aquaculture
• Main countries - Japan, China, Russia, Chile, US.

9
Fishery Locations

• See figure 13.14
• Fisheries located in areas of continental shelves
  and upwelling
• 10 of ocean 90 of fisheries

10
Upwelling
Wind
Continental Shelf
nutrients
11
Management of fisheries

• Goal - sustainable harvest from fish stock
• Problem - overfishing results in reduction of
  stock.
• Problems arise from an MSY approach based on
  logistic growht

12
Peruvian example

• Anchovy catch was estimated based on previous
  performance and MSY
• In El Nino years, upwelling ceased and pop
  decreased, resulting in overfishing, decreasing
  potential population.

13
Salmon Example (fig 13.15)

• Note how age profile of fish changes and
  correlate this to how the nuber of fish caught
  changes.

14
Has the Sea given up its bounty?

• New York Times
• Tuesday July 29, 2003

15
Basics

• More than 70 of fish stocks now considered fully
  exploited
• Increasing number of threatened and endangered
  species

16
Timeline

• 1900 2.6miltons, 33large
• 1950 7.3miltons, 48large
• 1975 15.1miltons, 30large
• 1999 12.4miltons, 31large
• Largecod, halibut, tuna

17
Worst is over???

• Peak in overfishing and environmental disregard
  was 10 yrs ago

18
Examples

• Swordfish 1900 they were 300 lbs 1990s, 90 lbs
• Cod have dissapeared from eastern Canada

19
Fishing spreads

• Since north Atlantic died out in 70s, now fishing
  off West Africa and Southeast Asia.
• Many stocks now 10 of 50 yrs ago

20
Biomass Extraction

• Fishing down the food chain
• Results in fish sticks or food pellets

21
Aquaculture

• Increases as stock decreases
• But uses coastal ecosystems

22
Whales and stuff

• Two kinds of whales - toothed and baleen
• Two uses of whales - subsistence and commercial
• Whaling was largely subsistent until pelagic
  whaling made oil

23
Whale commerce

• Oil used for cooking, lubrication, lamps,
  perfume
• Baleen used for corset stays and other springy
  needs
• Never a major industry in terms of total dollars

24
Whale conservation

• IWC formed in 1982 a major moment
• Have helped protect species and limit whaling
• Whaling limits are concerned with extinction and
  maintenance, not harvest

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