Miller—Chapter 13-6

Fisheries 3rd major food producing system Definition: Concentrations of particular

aquatic species suitable for commercial harvesting in given ocean area or inland body of waterExamples: Cod, tuna, mackerel, sardine,

anchovy, crab, shrimp, oyster, clam, squid, octopus

Most of (99%) catch is taken from coastal waters (as a result disrupted/polluted)

Fishing Industrialization

Fleets use:Satellite positioning

equipmentSonarHuge netsSpotter planesFactory ships that can

process and freeze their catches

Types of Fish Demersal: Mostly bottom-

dwelling Pelagic: Surface-dwelling Crustaceans: Hard

exoskeleton Mollusks: Live in hard

shell

Harvesting Methods To catch demersal and

shellfish (shrimp) Drag funnel-shaped net

held open at the neck along the ocean bottom

Destroys bottom habitats Nets big enough for 12

jumbo jets Small fish escape, but

other species (seals, turtles) can be trapped

Bycatch (other throwback species) get released

To catch pelagic species, such as tuna (feed near surface in schools)

Looks like a large drawstring purse to trap fish

Can also kill other species, ex: dolphins, which swim near surface with fish species

Harvesting Methods Put out lines of 80 mile-long

hung with thousands of baited hooks to catch open-ocean fish species (swordfish, tuna, sharks)

Can hook pilot whales, dolphins, turtles and sea-feeding bird, the albatross.

Uses huge drifting nets that hang about 15 meters below surface and are up to 34 miles long

Can lead to overfishing Traps/Kills large quantities of

unwanted species, like longlining.

US has banned nets longer than 1.6 miles in international waters Compliance is voluntary, difficult

to monitor fishing fleets and now more longlines are used which are also dangerous

Harvesting Methods

Fishing The remaining 1% comes from aquaculture

and inland freshwater lakes/ponds, rivers Between 1950-1982, the commercial fish

catch has increased 5-fold.Since ‘82, catch amount has slowed down and

will continue to decline…Why?

Want to achieve a “sustainable yield” The size of the annual catch that could be

harvested indefinitely without a decline in the population of a species○ Challenges: Hard to monitor mobile populations

and populations shifts year-to-year due to climate, pollution and other factors

Overfishing Taking so many of the fish that too little

breeding stock if left to maintain numbers (exceeds its sustainable yield)If continues, can lead to commercial

extinctionToo many fishing boats pursuing too few

fish (tragedy of the commons)Leads to a lot of political disputes (over 100

disputes about rights between countries)There are 14 fisheries that are so depleted it

would take 20 years for them to replenish the stocks if they halted everything now

Overfishing Problem

Other Problems Degradation/destruction/pollution of

wetlands, estuaries, coral reeds, salt marshes, mangroves

Projected global warming because there will be warmer ocean waters that would degrade or destroy coral reeds, enhance effects from habitat degradation

Thinning of ozone causes more UV radiation penetrating into the water

El Nino warming patterns

A possible answer:

Aquaculture Fish/shellfish are raised for food, supplies.

*China is leader in this practice. Two types:

Fish farming: Cultivates fish in a controlled environment (coastal/inland pond/lake/rice paddy) and harvest them when they reach desired size

Fish ranching: Holding anadromous (breed in freshwater) species such as salmon, live in captivity for their first few years of their lives (fenced in areas, lagoons, estuaries) then release them and harvest when adults return to spawn

Typical fish species: Carp, catfish, tilapia, milkfish, clams and oysters

Aquaculture Some countries (China) combine with agriculture.

They use pig manure and other waste to fertilize aquaculture ponds, promoting growth of phytoplankton to feed species

Used to stock for game fish purposes or to raise the expensive fish and shellfish 90% of all oysters 40% salmon (75% in US) 50% of internationally traded shrimp and prawns 65% freshwater fish sold in marketplace Catfish is leading product in US (Mississippi, Louisiana, Arkansas,

Alabama)

Some studies show that aquaculture has worsened the problem for fisheries by: Raising demand for some ocean fish (anchovies) that are

ground into fish meal and fed to aquaculture species Create vast amounts of waste in the coastal areas

Aquaculture

ADVANTAGES DISADVANTAGES

Highly efficient High yield in small volume of

water Increase yield through

crossbreeding and genetic engineering

Can reduce overharvesting of conventional fisheries

Little use of fuel Profits not tied to price of oil High profits

Large inputs of land, feed and water needed

Produces large and concentrated outputs of waste

Destroys mangrove forests Increased grain production

needed to feed some species Fish can be killed by pesticide

runoff from nearby cropland Dense populations are

vulnerable to diseases Tanks too contaminated to

use after about 5 years