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Fisheries Traditional food production and distribution practices are unable to feed the world’s 6.3+ billion people Will resources in the sea be able to provide enough food to alleviate future problems of malnutrition and starvation ?

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Traditional food production and distribution practices are unable to feed the world’s 6.3+ billion people

Will resources in the sea be able to provide enough food to alleviate future problems of malnutrition and starvation ?

  • Most valuable living marine resources:
  • Fish
  • Crustaceans
  • Mollusks

Commercial fishing:

  • 500 species regularly caught
  • employs 15 million people worldwide
  • In 1999:
  • 137 million tons taken
  • $70 billion

World Harvest of Marine Fish (in millions of metric tons)

Country 1995 1999 2000


China 11 15 14.8

Peru 8.9 8.4 10.6

Japan 5.9 5.1 4.9

United States 5.2 4.7 4.7

Chile 7.4 5.0 4.3


World Commercial Catch of Marine Fishes, Crustaceans, and Mollusks (1995)


Species Group Millions of Metric Tons, Live Wt.

Herrings, sardines, anchovies 22.0

Jacks, mullets, sauries 11.2

Mollusks 11.0

Cods, hake, haddock 10.6

Redfish, basses, conger eels 7.0

Crustaceans 4.8

Tunas, bonitos, billfish 4.7

Mackerel, snooks, cutlass fishes 4.7

Flounders, halibut, soles 0.9

Miscellaneous marine fishes 17.7

Total (excluding marine mammals) 94.6


Non-Food Products from the Sea

  • Bioactive Compounds
    • Anti-viral (e.g., acyclovir)
    • Anti-tumor (e.g., bryotstatin from a bryozoan, Didemnin-B from a tunicate)
    • Insecticide (e.g., Padan from a marine annelid worm)
  • B. Algin & Agar: products from seaweed
    • Algin used to stiffen fabrics, as an emulsifier in salad dressings and paints, in ice cream to prevent formation of large ice crystals
    • Agar and derivatives used extensively in microbiology and molecular biology as a gelling agent
  • C. Whales: Oil for lubrication, in cosmetics, bones for fertilizer
  • D. Seals and sea lions: furs

II. Food from the Sea

  • Seaweeds
  • Invertebrates (e.g., oysters, clams, crabs, lobster, squid, etc.)
  • Fish (herring, mackerel, haddock, cod, tuna, mahi-mahi, etc.)
  • Whales
  • 1. Commercial whaling moratorium pronounced by the International Whaling Commission effective 1987
  • 2. Japan continued whaling Minke under provision for scientific research, but meat and blubber was sold at market
  • 3. Beginning in 1993, Norway resumed whaling Minke 4. In 2000, Japan expanded to Blue and Bryde‘s whales

Fisheries mismanagement

  • Overfishing
  • Commercial extinction
  • Bycatch (27 million metric tons annually)
  • Targeting smaller species on the low end of the food chain

Peru Anchovy Fishery

  • Upwelling zone off Peru
  • Fishery began 1950
  • Greatest fish catches for any single species
  • Fish exported for domestic animal feed
  • Fishery collapsed due to El Niño and overfishing

Peru Anchovy Fishery

= El Niño







Peru Anchovy Fishery

Normal Year

El Niño Year


Collapse of New England Fisheries

  • Cod, haddock, ocean perch, herring, mackerel, blue fin tuna
  • George’s Bank- highly productive, nutrient rich environment
  • Prior to 1976, Russia, Japan, Norway, & West Germany fished in Georges Bank

Collapse of New England Fisheries

Magnuson Act passed & prevented foreigners from fishing in U.S. waters

Fishery technology intensified and resulted in overfishing

Harvests were beyond the max. sustainable yield

Georges Bank closes after collapse

Some fish stocks begin to rebound



  • Anadromous fish that migrate from sw to fw to spawn
  • Spawning grounds affected by dam construction
  • Aquaculture and restocking efforts

Shark Overfishing

  • Slow growth
  • Low reproductive rate
  • Late sexual maturity

Orange Roughy

  • Distribution: world wide, high concentrations in New Zealand
  • Found: 700-1000m depth
  • Life span: slow-growing, long-lived, ~150 years
  • Size: 30-40 cm
  • Diet: prawns, fish, & squid
  • Reproductive age: 25-30 years old

Fishing Methods

  • Harpoon - whales, swordfish, bluefin tuna
  • Pole and line - mahi-mahi and used for tuna extensively in the 50‘s
  • Longline - swordfish, tuna (pelagic); cod, halibut (bottom)
  • Trolling - salmon, albacore, mahi-mahi
  • Drift (gill) netting - various pelagic fish
  • Trawl - anchovies (pelagic); cod, halibut (bottom)
  • Purse seine - sardines, herring, mackerel
  • Traps and Pots - Crabs, lobster, rock fish

Drift Net

net size:

20 m x 65 km


Gill net

Purse seine

Bottom-dwelling fish


Before trawl

After trawl


Laws of the Sea Treaty

Allow nations to claim jurisdiction over their territorial seas (contiguous sea beds and their waters that extend off shore by 12 nautical miles)

  • Exclusive Economic Zone (EEZ)
  • 200 nautical miles
  • under direct control of the country that owns the nearest land
  • Regulates continental shelf resources:
  • Fishing
  • Mineral exploration
  • Scientific research

Fisheries Problems & Solutions

  • Maximum sustainable yield: maximum amount of fish that can be harvested without depleting future stocks
  • World‘s maximum sustainable yield estimated at 100 to 135 million metric tons
  • Present harvests are at about 100 million metric tons
  • For fisheries where numbers available, estimated that 45% are currently over-fished
  • A number of fisheries have already collapsed (Anchovy fishery off Peru, Cod fishery in the N. Atlantic)

Fisheries Problems & Solutions

F. Bycatch (or bykill): animals unintentionally killed during harvest of the target species

Trawling: Bycatch in shrimp trawling is very high (125 to 830% of the catch is discarded as bycatch), turtles often caught in trawls.

SOLUTION: trawls with trap doors to let turtles escape


Purse seine: Tuna known to hang out under pods of dolphins, nets set around pods of dolphins would result in many drowning.

SOLUTIONS: Nets not set around dolphin pods and/or employ — “backing down”, a technique that lowers upper edge of net letting dolphins escape

Dolphins caught in tuna net


Fisheries Problems & Solutions

  • Bycatch
  • Driftnets: indiscriminate entangling of many sorts of marine animals
  • SOLUTION: banned in oceanic fisheries (but some countries still using them)
  • Long lining: Many albatross drown trying to snatch bait from long lines being deployed. snagged on hooks and pulled under.
  • SOLUTION: deploy in the dark or with special rig to let line out under water.

Mariculture or Aquaculture

(marine agriculture)- farming finfish, shellfish and algae under favorable conditions


Aquaculture also produces:

    • Bait fish
    • Ornamental or aquarium fish
    • Aquatic animals used to augment natural populations
    • Algae for chemical extraction
    • Pearl oysters


  • 2000 years ago in Egypt, Rome, China
  • <2000 years in Hawaii
  • 600 years ago France developed mussel aquaculture
  • 500 years ago Europe developed the idea of using pond fertilizer to promote plankton growth
  • 400 years ago China discovered that oysters would grow on bamboo stakes
  • 1960’s- Europe and U.S. catfish and salmon

Criteria for selecting species for farming:

- inexpensive to grow

- grows quickly

- high sales price

- resistant to disease and parasites


Problems associated with Mariculture:

  • Won’t make a dent in the shortfall in food supply
  • Many farmed fish must be fed fish meal
  • Produces much waste (especially shrimp)
  • Destroys habitat for other species
  • Crowded pens lead to disease (antibiotics)

Molokai: South Coast

  • The pond’s walls were made from lava boulders and coral.
  • Walls keep the fish inside while allowing the sea water to ebb in and out.

Types of fish raised in ponds:

    • ulua (trevally)
    • kumu (goatfish)
    • kahala (amberjack)
    • manini (convict tang)
    • palani (surgeon)
    • oio (bonefish)
    • uhu (parrotfish)
  • These fish were kept in a separate pond to breed and raised so they could easily be harvested by hand.

Artificial Reefs

  • Improve the local marine bio-density
    • attract schools of fish
    • providing habitats for the colonization of commercially valuable species
    • improve the local inshore marine harvest

May wash up

on beaches

construction rubble


ship wrecks