Patterns of Growth in
Fishes
Grow and Survive to Reproduce
Growth patterns in fishes
 Context
for study of growth:
 to “succeed”, a fish must reproduce
viable offspring
 to reproduce, a fish must survive long
enough to reach maturity
 to reach maturity, a fish must grow:
Factors Affecting Growth

Hormones
– Growth hormone secreted by pituitary
– Steroid hormones from gonads

Temperature
– Most important environmental factor
– Growth increases up to a point
– Fish tend to prefer temperatures where their
growth is maximal
Growth patterns in fishes
 Dissolved
Oxygen
– More is better
 Ammonia
– High concentrations slow growth
 Salinity
– Growth is altered when fish are not in their
optimum salinity
Growth patterns in fishes
Competition
– Generally slows growth
 Food
– Availability & quality affect growth
 Photoperiod
– Longer days increase growth

Growth patterns in fishes
•
Age & Maturity
– Growth is rapid early in life
– With maturity more energy is diverted to gonadal
tissue
– Larger fish need more energy to maintain body
 Conditioning
(Weight lifting for fish??)
Keys to success:
 GROW
 SURVIVE
 REPRODUCE
Bioenergetic context
 Growth
is the accumulation of somatic
(body) tissue that depends on a surplus
of energy consumed
Bioenergetic context
 Bioenergetic
equation:
I=M+G+R+E






I = energy ingested
M = energy used to maintain healthy tissues
G = energy for growing somatic tissue
R = energy for reproduction
E = energy “lost” through inefficiency of
energy transfers, etc.
Growth Rate
 Anything
in the internal or external
environment that increases or
decreases I:




food availability
competition with other fish for food
time spent hiding from or escaping
predators
time spent defending a territory
Growth Rate
 Anything
in the internal or external
environment that increases or
decreases M:



temperature
dissolved oxygen
toxins - NH4+, heavy metals, organic toxins
Growth Rate
 Energy
for growth is a tradeoff with
energy for reproduction


general pattern: grow first, then reproduce
increased size -->
• increased fecundity (females)
• increased territorial success (males, females)
• increased metabolic efficiency (to a point)
Fish growth often is periodic
 Seasonal
variation in temperature, food
availability, spawning activity, can
cause seasonal growth cessation
(Can you think of examples where this might
happen?)
Fish growth often is periodic
 Seasonal
variation in temperature, food
availability, spawning activity, can cause
seasonal growth cessation
 If periods are regular (e.g., annual or
daily), a record of growth and nogrowth periods is formed in hard
structures:

scales, fin spines or rays, vertebral centra,
opercle bones, ear bones (otoliths)
Fish growth often is periodic
 Periodic
growth marks allow estimation
of growth rates by counting and
measuring distances between growth
checks
Endocrine Growth Regulation
 Pituitary



growth hormone:
increases appetite
increases food conversion efficiency
increases production of stomatomedin
(stimulate cell growth and division)
How do different forms of mortality effect overall population
growth??
Internal regulation of growth endocrine system
 Anabolic



steriods stimulate growth:
testosterone in males
estrogen in females
corticosteroids in both sexes
Internal regulation of growth endocrine system
 Thyroid
hormones stimulate growth
 Also regulate metamorphosis
Fish growth is indeterminate
 Growth

continues throughout life cycle
limits to ultimate size are BIOTIC (food
availability, metabolic efficiency) and not
MECHANICAL (counteracting gravity, etc.)
Fish growth is indeterminate
 Advantages

to indeterminate growth:
larger size yields greater efficiency
Fish growth is indeterminate
 Advantages


to indeterminate growth:
larger size yields greater efficiency
larger size yields more food options
• faster swimming
• larger gape size
• better sensory range & acuity
Fish growth is indeterminate
 Advantages



to indeterminate growth:
larger size yields greater efficiency
larger size yields more food options
larger size reduces number of potential
predators
• swimming speed
• gape size