Harvesting living marine resources: fisheries and fishery management

what are fisheries

• hunting/gathering of aquatic and marine biological resources

fished marine species

• algae

• zooplankton

• invertebrates

• cartilaginous and bony fish

• turtles

• mammals

human consumption: land vs sea

• about 98% of human food comes from land and freshwater

  • ocean accounts for 10% of protein

• harvesting from land and ocean are VERY DIFFERENT

distribution of world fisheries

• ~90% of marine fishing takes place over continental shelves

• upwelling regions

  • lots of nutrients

  • lots of primary production

  • support very productive fisheres

fishing techniques

• hooking individually

• entangling in nets

• surrounding in nets

• traps

• dredging

problem of overexploitation (3)

• bycatch

• ghost gear

  overfishing

  • in one area too intensely

  • too much without knowing maximum sustainable yield

bycatch

• unintended catch

  • used for other purposes (fish meal)

  • discarded overboard

• constitutes much of world catch

overfishing

• maximum sustainable yield

• maximum economical yield

maximum sustainable yield

largest annual catch that can be sustained indefinitely

maximum economical yield

largest annual catch that produces the highest net revenue

consequences of overfishing

• population too small to reproduce

• juveniles harvested before they reproduce

• fisheries crash

fishing down the food web

• largest, high trophic level species fished first because they are the most desired

• as large fish become economically extinct, fishers will shift to lower trophic levels

• if fish in lower levels are captured in abundance, then fish higher up will not have food

tragedy of the commons

• actions of self-interest can degrade a shared resource to detriment of all

• many open ocean resources were assumed “unowned” or open to all

• increased competition for limited resources leads to overfishing

law of the sea treaty

• territorial water: 12 nautical miles

• exclusive economic zone: 200 nautical miles

  • need to manage domestic catch

  • have to open excess catch to other nations

stock (1)

populations that are geographically definable and consisting of individuals responding to similar environmental factors

stock (2)

fisheries management unit

nursery, feeding area, political boundaries

why is stock important

stock identification is important in societal disputes about fishing policy

tags

utility depends on rate of recovery, time period that they last, define movement

biochemical and molecular markers

identify different stocks that have become genetically isolated and distinct