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9. Managing fish stock:

Science & The Fishing Industry

OBJECTIVES
> To understand the value of fish as a food source To know how fishing methods increase yield
> To understand how overfishing has reduced fish stocks
> To appreciate that the management of fish stocks depends on scientific research

Fish as a source of food Setting of quotas

Fish have been a valuable food source for Governments set quotas in an attempt to limit the
humans for thousands of years. Fish are an size of catches. Unfortunately, scientists now
excellent source of protein and, depending on believe that initial quotas for some species were too
species, of oils. Scientists are becoming more high, and even the reduced quotas now in force
aware of the value of fish oils in preventing some have not allowed fish populations to recover. The
of the `diseases of affluence', such as coronary fishermen are tempted to catch more than their
heart disease. It is very important that humans quota but
include certain oily compounds (especially to throw back the smaller, less marketable fish.
unsaturated fatty acids) in their diet, and these These fish are often damaged by capture and do
oily compounds are extremely abundant in some not survive to reproduce.
fish species. As with many situations, there are no clear-cut
Steps taken to conserve fish stocks answers. Fishermen understand that fish stocks
must be allowed to recover but are naturally anxious
Education
about making a living. The scientists can only
Through knowledge of the growth pattern of
advise, the governments must act on this advice!
individual fish, it is possible to study small groups
Restocking
of fish to work out how long they take to reach
breeding age, what their maximum size will be Fish can be bred in very large numbers in

and which diseases they might be susceptible to. enclosures, either in the sea or in lakes. These fish
This allows scientists to advise on net mesh sizes can be grown to a size at which they can be
which should be used to catch adult fish, and to successfully released to replenish wild populations.
suggest fishing methods which will limit the catch
of 'trash' fish (fish which are not used for human
food). Fishing methods and mesh sizes used in
herring fishing are shown opposite.

1 Tilapia is a fish which can be 'grown' in
fish farms. Suggest

a. why this is more financially sensible in
tropical countries
b. three benefits of having Tilapia in the
diet

Mesh and methods used in herring fishing

Learning Module Organisms and Their Environment | Class 11 32