Deck 19: Harvesting the Oceans Resources

Question 1

In addition to increased mortality rates, what are two other problems associated with overfishing?

Answer 1

Overfishing occurs when the fish are caught rapidly than their reproduction and replacement. This causes high mortality rate of fishes by depleting the stocks. Overfishing can lead to genetic and species diversity and destruction of the habitat. Overfishing causes changes in the genetic characteristics by selecting for or against of traits like size of animal sexual maturation. This may be observed in the case of capturing of larger mature fish.
Constant capturing of larger fish favors the survival of the fish that mature at earlier age with smaller size. Heavy fishing leading to capture of fishes that are early in reproductive life causes depletion of fish of younger age and damage their reproductive life. As a result, the genetic variability shift to the individuals that reproduces at early age or smaller size and becomes selective pressure.
Overfishing affects the biological diversity by reducing the number of species. This causes population decline because no species can play a role of prey, predator or competitor in the ecosystem and may become ecologically extinct. Removal of important species may lead to restructure of ecosystem by evolving new prey species and new predators in the place of fish caught.
Overfishing also damages the habitat because of disturbance in ecosystem. For example, fishing activities can damage the coral reefs due to habitat loss. Heavy trawl nets dragged on ocean floors damage the sea grass beds and rocky habitats. This may physically damage the fish and shellfish.

Question 2

What is the relationship between the size of the world's population, fishing effort, and the size of the commercial catch of fish and shellfish?

Answer 2

In the year 1950, the total world catch of shellfish and marine fish was about 21 million metric tons approximately. In the year 2000 it has reached to 86.7 million metric tons. From this it can be known commercial fishing has been increased dramatically according to the growing demand of human population of more than 7 billion.
The world fish catch has not been increased proportionately relative to the fishing effort and is being around 80 million metric tons for the past 10 years. In the year 2009, the total world catch of marine fish and shellfish was about 79.5 million metric tons and most of the ocean species that were found in peaks during 1980 are reported to be declined. Over the past 50 years, the use of commercial catch has been changed.
In 1950, about 90% of world's fish catch have been used for human consumption and remaining 10% was used as fish meal products to feed the livestock. By the year 1988, 60% of fish catch was used for human consumption and 40% feeding the domestic animals.
This trend is being continued and according to 10% rule of ecology, the 10% of energy available in one trophic level is passed on to the next level. Therefore, for each ton of commercial fish fed to animals should yield about 0.1 ton of animal biomass. Most of the commercial fishes are in higher trophic levels and therefore, huge waste of energy than harvesting fishes at lower trophic level is observed.

Question 3

When the size of the commercial catch increases, the size of individual fishes decreases. Why does this occur?

Answer 3

Overfishing also damages the habitat because of disturbance in ecosystem. For example, fishing activities can damage the coral reefs due to habitat loss. Heavy trawl nets dragged on ocean floors damage the sea grass beds and rocky habitats.
This may physically damage the fish and shellfish. Therefore, increase in the size of commercial catch decreases the size of individual fishes because of habitat loss and damage caused due to fishing operations and equipment.

Question 4

How does the cost of fishing influence the kinds of fish caught and the methods used to process them?

Question 5

Commercial fish and shellfish are raised using the same methods that are used in agriculture for terrestrial animals, a. practice known as aquaculture or mariculture.

Question 6

Considering the vast mineral resources of the sea, why aren't more minerals mined from this rich area?

Question 7

Many ____ are killed as a result of the methods of fishing for tuna.
a. turtles
b. seabirds
c. dolphins
d. noncommercial fishes
e. molluscs

Question 8

Why is it important for the fisheries industry to be regulated?

Question 9

Why is it difficult to accurately determine the size of commercial stocks of fishes and shellfishes?

Question 10

Why is it not ecologically sound to use anchovies for livestock feed?

Question 11

Suggest some ways that commercial fishers could decrease the size of their catch without becoming unemployed or going bankrupt.

Question 12

Why are some commercial fishers opposed to ocean ranching?

Question 13

Many commercial fishing practices are harmful to the environment. Dredges and trawl nets disrupt benthic communities, destroy bottom habitat, and kill many noncommercial species. Since nets are not designed to catch only one type of fish, many noncommercial species (the by-catch) are caught and killed in fishing.

Question 14

In the United States, most of the by-catch is
a. used for feeding livestock
b. consumed by humans
c. dumped into landfills
d. returned to the sea
e. exported to other countries

Question 15

Compare potential yield with sustainable yield.

Question 16

Increased fishing effort has decreased many stocks of fish and shellfish to dangerously low levels. One recent report suggests that by the middle of this century there will be nothing left to catch.

Question 17

Other resources obtained from the sea include salt, water, gravel, sand, oil, natural gas, and a variety of minerals.

Question 18

Match the following terms with the appropriate definition or description:

Question 19

A major problem associated with preferentially fishing for large fish such as tuna is that

A) they are harder to catch in nets
B) they feed at higher trophic levels
C) fewer can be caught at one time
D) they yield more waste when processed
E) they do not swim in schools

Question 20

The largest seafloor mining operations extract
a. salt
b. manganese
c. sulfides
d. sand and gravel
e. calcium

Question 21

Besides overfishing, what other problems are contributing to the decline in fisheries production?

Question 22

What is the goal of fisheries management?

Question 23

By 1980, what percentage of the commercial catch was being converted into fish meal?

A) 10%
B) 20%
C) 30%
D) 40%
E) 50%

Question 24

From an ecological standpoint, would it make more sense for humans to eat anchovies or tuna? Explain.

Question 25

What are some benefits of aquaculture?

Question 26

Fisheries management is important to ensure that commercial fish stocks are not depleted and to maintain stable populations for future generations to fish.

Question 27

Which of the following fishing techniques is most likely to damage habitat?

A) purse seining
B) drift netting
C) gill fishing
D) trawling
E) pole fishing

Question 28

The most valuable substance (in dollar amount) that is removed from the sea is
a. coal
b. salt
c. water
d. oil
e. sulfide

Question 29

What are some ecological problems associated with aquaculture?