Fisheries science and management I: a history of fishing and the basis of sustainable fishing

Question 1

Why do we study fisheries science?

Answer 1

• Understand seasonality and location of fish
• Predict where and when fish can be caught
• Link abundance to environmental conditions
• Predict how many fish will be produced

Question 2

Give a brief account of the history of fishing

Answer 2

• low scale fishing (hand lines, small nets, small boats) -> low risko of overfishing
• 1700-1800 - more efficinent gear and mechanisation of vessels + refrigeration -> overfishing risk increased but still low
• 1900s - high gear efficiency, fish finding technologies, helicopters, models -> volnurability of fish stocks increased dramatically

Question 3

What was an important food fish for Maori?

how did it dissapear?

Answer 3

• Upokororo, or southern grayling (Prototroctes oxyrhynchus)
• Commonly reached 280 mm, up to 450 mm and 1.5 kg
• Entered rivers from the sea Oct-Jan to spawn; two size classes – spawned more than once?

propably outcompet by introduced trout

Question 4

Why is fishing important to humans?

Answer 4

Worldwide

• 20% of the animal protein in their food from fish directly
• 5% from fish meal fed to livestock.

87% of the annual commercial catch of fish and shellfish comes from the ocean (rest from freshwater).

In most Asian and island countries, fish and shellfish supply 30-90% of the animal protein eaten by people. Therefore we need to manage fish harvest.

Question 5

What are the major commercial fishing methods?

Answer 5

A. Potting

B. Gill netting

C. long lining

D. dredging

E. trawling

F. purse seining

Question 6

How is the global fishing producito nestimated?

Answer 6

• global primary production (phytoplankton),
• the trophic level of the main fishery species, and
• the efficiency of energy transfer between trophic levels
• Assume 10% goes from one level to the next

we can estimate the maximum possible global fisheries production.

highest production in upwelling areas bt they only make up 0.1% of surface area. Open ocean is the lowest production/m but due to high surface area the highest over all.

240million tonnes/year over all p=fish prodcution in the ocean (can’t all be harvested)

Question 7

What is the FAO (2010) estimation of harvestable fish from the ocean?

Answer 7

100 million tonnes (already reached)

Question 8

What are the basic principles of fisheries management?

Answer 8

• reservoir analogy (input - output)
• What do we need to know to find out what the effect of fishing might be on the reservoir (stock) of fish?
• fishing mortality (yield)
• -> survivorship curve (lots of offspring but high mortality

Question 9

How does the current annual yield influence stock assesement?

Answer 9

Question 10

How did the peruvian anchoveta fisherie collaps?

Answer 10

• fish is tightly coupled with environmental events.
• upwelling failed due to El Nino in 72 -> no primary production -> no recruitment -> fisheries collapse