Chapter 19 Flashcards
Harvesting the Oceans Resources
Sea has been a major source of food for human populations
- new source of natural resources over past 100 years
- many are concerned about increased development along with increased fishing pressure
Commercial Fishing dooms day study
A study released in 2006 reported that by 2048 most commercially fisheries will collapse due to overfishing
Humans have harvested fish and shellfish (invertebrates) from oceans for thousands of years but there has been A
dramatic increase in past 50 years
Over the past 50 years there has been a change in how fisheries catch has been used
1950: 90% human consumption; 10% feed
1988: 60% human consumption; 40% feed
Renewable Resources
resources that can replenish themselves
- animals not caught can replace those that were
The goal of fisheries management is to maintain these resources by:
Enacting policies on fishing practices
Setting catch limits
If done correctly should:
Prevent overfishing to the point of extinction
Allow enough animals to survive and reproduce
Allow for fisheries to be sustainable in the future
Stocks
a separate population of fish that is assumed to be reproductively isolated from others in the range
Tagging
a procedure for monitoring the distribution and movement of animals in the environment
Landings
the catch made by fishing vessels
Fishing effort
a measure of the number of vessels fishing, the number of fishers working, and the number of hours spent fishing
- Catch Per Unit Effort (CPUE)
Potential Yield
the number of pounds of fish or shellfish a stock can yield annually without being overexploited
Sustainable Yield
the maximum yield over several years that will not stress a stock
Surplus population models
– used to search for the largest fishing mortality rates that can be offset by increased population growth, normally measured in changes in population biomass per unit time
Complex calculations based upon several life history parameters, including:
population density
population biomass
population growth rate
If quota set too high:
yield would exceed the surplus population so the population would be driven to extinction
If quota set too low:
- will stabilize and yield lower than BMSY or
- will become unstable and either increase to equilibrium at the higher population size or crash
Biological interactions
mean that population dynamics of different species are inevitably linked
Overfishing
is catching fish faster than they can reproduce and replace themselves
At least 60% of the world’s 200 most valuable species are currently overfished
Overfishing can cause changes in:
- Genetic diversity
- Species diversity
- Habitat
Trawl Nets
are large nets that are dragged along the sea bottom
Gillnets
made from monofilament line continue catching for hundreds of years
Bottom Trawls
can stir up sediment and destroy bottom substrates
Exclusive Economic Zone (EEZ):
is the area of ocean that a coastal nation controls
Law Of the Sea (1977)
established 200-mile-wide Exclusive Economic Zones (EEZ)
granting coastal nations exclusive rights with respect to natural resources
Surimi
is a fishery product made from Alaskan Pollock
- fats and oils removed; flavor added back to mimic shellfish
Incidental Catch (Bycatch)
the non-commercial animals that are killed during fishing for commercial species
Trash Fish
the term used for incidental catch that is solely fish
Inefficient use of catch: Shark Finning
100 million sharks are killed each year
Estimates are between 63-273 million per year
Drift Nets
are large nets that may stretch for as much as 60 kilometers
Tans
are individual sections of a drift net
Case Study mackerel and red snapper
GOM shrimp fisheries discarded 19 million red snapper and
3 million Spanish mackerel
Aquaculture (Mariculture):
the use of aquaculture techniques to breed and raise marine organisms
Monoculture
the process of raising a single species in aquaculture
Polyculture
the process of raising several species together in aquaculture
Raft Culture
a form of aquaculture in which juveniles of commercially valuable molluscs are attached to ropes suspended from rafts
Eco-Friendly Aquaculture
is a type of aquaculture where the growing of fish or shellfish do not have negative impacts on the environment; sometimes positive
Eco-Friendly Aquaculture Often involves
Using waste to produce food for animals
- sewage to grow algae to feed oysters
Using waste a fertilizer for plants
- shrimp farm waste to fertilize adjacent fields
3) Using animals to minimize waste back to sea
- bivalves to clean waste water before return
Problems with Aquaculture
Pollution
- nutrients
food waste
animal waste
- drugs & chemicals
2) Wild fish caught to feed cultured fish
- global production decreases
3) Invasive species
- impact foodwebs
- cause disease
Purse seines
are huge nets that can be closed by pulling on a line; similar to the way a purse or a bag of marble is closed
Backing Down
a technique in which the skiff setting the purse seine backs up, causing the edge of the net to drop beneath the surface of the water, allowing dolphins to escape
Ocean Ranching (sea ranching):
a process in which young fish are raised in pens and then returned to the sea to supplement natural populations
- ½ fish commercially caught are hatchery fish
Desalination
the process of removing salt from seawater
Sulfides
minerals containing sulfur
include gold, silver, platinum etc…
Manganese - estimated 16 million metric tons on ocean floor
Fossil Fuels
are fuels formed from the remains of organisms that lived millions of years ago
Methane Hydrate
is ice that holds methane gas
Case Studies
Anchovies
Anchovies represent worlds largest catch of a single species; Changes is ocean production (El Nino) coupled with overfishing caused a crash in the fishery
Case Studies Tuna
Tuna are a global fishery with over 4.6 million tons annually harvested in the US
Depending upon species and location tuna are either:
Longlined – yellowfin, bigeye, albacore
Hand lined – Bluefin, albacore
Purse seined – yellowfin, bluefin
Case Studies
Marine Mammal Protection Act
1972
to reduce the number of marine mammals, including dolphins killed in fisheries
Implemented several changes to purse seining methods and equipment including a Backing Down procedure
Case Studies
Salmon
Salmon are an important fishery in the US
Pacific Salmon – Pacific NW & Alaska
Atlantic Salmon – N. Atlantic & Farmed
Due to high demand for fish and increased pressure upon wild stocks; fish in Pacific NW & Alaska are reared in hatcheries and released to supplement wild stocks
- ½ fish commercially caught are hatchery fish
Case Studies
Shellfish
represent a large amount of the commercial catch in the world
- 7 million metric tons molluscs
- 5.5. million metric tons crustaceans
Mineral Resources
30% of the worlds supply of Salt (NaCl)
200 million metric tons annually
60% of the worlds supply of Magnesium
70% of the worlds supply of Bromine
10 million tons of Gold 4 billion tons of Uranium
Most widespread seafloor mining is to extract sand and gravel for:
cement
- concrete
- replenishing natural beaches
- creating artificial beaches
Oil and Natural Gas
90% of the value of minerals taken from the sea - formed from remains of microorganisms like diatoms
Annual revenue of offshore production is over $100 Billion
