1. BIOLOGICAL PROCESS THAT EFFECT FISH
STOCK
1. Reproduction
1.1.
Meaning
 Biological reproduction of new
individuals through breeding
1.2.
Type of reproduction
 Asexual
- Not involve sex between
male and female
- Example
Fission: amoeba
Cutting: plants
 Sexual
- Involves sex between male
and female
- Egg fertilized by the sperm of
the male to form embryo
develop into new individual
- Type
External
o eggs and
sperm
released to
external
environment
o most fish
undergo
external
reproduction
Internal
o fertilization
takes place in
female body
o few fish,
mammals,
human
1.3.
Factor affect reproduction
 Environmental
 Growth
 Age at maturity
 Food and nutrient
 Fish health
 Availability of sexual partners
1.4.
How to manipulate factor
 Control river speed and
temperature
 Build fish ladders for
migrate(salmon)
 Make habitats more structurally
complex
 Enforce Laws and
regulations(protect fish during
breeding season)
2. Growth
2.1.
Meaning
 Biological process when fish
increase in weight and length
over time through addition of
tissue
2.2.
Reason to growth
 Achieve the maturity age
 To perform recruitment
 To reach predation
 To increase its overall chance of
survival
2.3.
Affected by
 Food availability
- Fish eat more and have
better growth
 Environmental factors
- Temperature increase, fish
active(eat more), growth
faster
- Tropical fish growth faster
than temperate fish
2.4.
How to manipulate
 Adding fertilizer to water to
increase planktons for fish
 Protect nursery area
 Control water quality parameters
 Adopt technique that will
increase fish food organism

2. 3. Recruitment
3.1.
Meaning
 Biological process which fish
enter fish stock for the first time
3.2.
How to manipulate
 Stocking programs at hatcheryraised fish
 Protect nursery area
 Enforce laws, rules and
regulations
- Ban fishing during breeding
seasons and spawning
migrations
- Ban fishing when catching
gravid females
4. Mortality
4.1.
Meaning
 Biological process in which a fish
die and is removed from the fish
stock
4.2.
Type
 Natural
- Fish die to natural causes
Predation
Disease
Old age
 Fishing
- Caught by fisherman and
removed from stock
4.3.
How to control fishing by
humans
 Soft approach
- Education
- Awareness
- Campaigns
 Hard approach
- Enforcing fishing rules
- Regulations
- Laws on fisherman