| REPRODUCTION |
BEHAVIORS |
- SPAWNING
SEASON : sporadic throughout year with peaks in southern
winter (August to October), and a secondary peak in summer
(January to February).
- also
regional: northern & central Peru - peak 1 at end
of winter & peak 2 at end of summer; southern Peru
- one single winter spawn
- LIFE
CYCLE: egg --> larva --> juvenile --> adult
- LIFE
SPAN: 4 years
- COMPETITORS:
sardine & machete
- SEXUAL
MATURITY: by 1 yr (females spawn 10,000 eggs); 2 yr females
can spawn >20,000 eggs
How
can the fishing industry deplete a population when it harvests
small individuals, even though they are sexually mature? Think
about growth overfishing and the
amount of eggs a female produces based on her size. |
- MIGRATION
PATTERNS: No definite migratory movements. But shoals tend
to move closer to shore during summer months and disperse
into deeper water during winter months.
- SCHOOLING
BEHAVIOR: Greatest density during the day; dispersed at
night, with evidence of vertical displacement towards the
surface.
- SIZE
COMPOSITION: Number of small fish (8 to 10 cm) increase
from January to March, resulting from eggs spawned during
winter of previous year. Fish generally increase in size
as year progresses.
|
| |
| The
anchovy is a pelagic schooling fish that feeds on
plankton. As with any organism on this planet, its
location and population size is influenced by availability
of its food source (in this case, plankton). The
chart below organizes steps in the anchovy population's
life cycle that fluctuates with the seasons. |
|
in
NORTHERN HEMISPHERE
|
|
winter
|
spring
|
summer
|
autumn
|
|
Dec
• Jan • Feb
|
Mar
• Apr • May
|
Jun
• Jul • Aug
|
Sep
• Oct • Nov
|
|
summer
|
autumn
|
winter
|
spring
|
|
in
SOUTHERN HEMISPHERE
|
|
|
|
|
|
|
|
spawning
peak 2
|
|
spawning
peak 1
|
|
recruit
cohort 1 from spawn 1
|
|
recruit
cohort 2 from spawn 2
|
|
|
The
anchovy population is most abundant off the coast of
Peru.
- What
is unique about this coast that enables it to maintain
such a rich resource?
- What
kinds of natural and human-made ecological events
can disturb the high productivity along the Peruvian
coast? Consider the data presented in this website.
- What
do you think happens when these ecological disturbances
occur?
(Paulik,
1981;Jordan, 1980).
|
|
(Data
for figure from FAO Fish Stat 2001)
|
This
figure represents the annual catch of anchovy. Use it to generate
an estimate of anchovy population size in the last 30 years.
Analyzing the graph in detail reveal the following speculations
about the Peruvian anchovy population:
- 1960s.
The steady increase in anchovy harvest suggest the anchovy
population was abundant during this decade.
- 1965
& 1969. Small, but noticeable dips in harvest.
- 1970.
Anchovy harvest peaked at 12 million metric tons.
- 1972.
Anchovy population plummeted.
- 1970
to 1990. The anchovy population did not appear to recover
for two decades.
- 1982-83.
The population reached an all time low.
- early
1990s. Population show signs of recovery.
- 1998.
Population plummets again.
- 2000.
Anchovy population appear to be recovering again.
- 2001.
Signs of declining population.
- Take
a close look at the years of peak harvest and declines.
Compare them with other data available, i.e. ecological
and human activities data. What do you notice?
- The
anchovy population seems to oscillate considerably. How
much of this is caused by humans and how much is natural?
- Could
human activities magnify natural fluctuations, or vice versa?
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This web
site was created by Lynn Tran at the North Carolina State University, Department
of Mathematics, Science, and Technology Education on 7/12/03. Faculty advisor
Dr. David Eggleston, NCSU, Department of Marine, Earth, & Atmospheric Sciences.
Last updated
December 29, 2003
.
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