Patterns of Growth in Fishes

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Patterns of Growth in Fishes

• Grow and Survive to Reproduce

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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

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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

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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

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Growth patterns in fishes

• Competition
• Generally slows growth
• Food Availability quality affect growth
• Photoperiod Longer days increase growth

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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??)

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Keys to success

• GROW
• SURVIVE
• REPRODUCE

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Bioenergetic context

• Growth is the accumulation of somatic (body)
  tissue that depends on a surplus of energy
  consumed

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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.

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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

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Growth Rate

• Anything in the internal or external environment
  that increases or decreases M
• temperature
• dissolved oxygen
• toxins - NH4, heavy metals, organic toxins

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Growth Rate

• Energy for growth is a tradeoff with energy for
  reproduction
• general pattern grow first, then reproduce
• increased size --gt
• increased fecundity (females)
• increased territorial success (males, females)
• increased metabolic efficiency (to a point)

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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?)

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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 no-growth periods is formed
  in hard structures
• scales, fin spines or rays, vertebral centra,
  opercle bones, ear bones (otoliths)

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Fish growth often is periodic

• Periodic growth marks allow estimation of growth
  rates by counting and measuring distances between
  growth checks

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Endocrine Growth Regulation

• Pituitary growth hormone
• increases appetite
• increases food conversion efficiency
• increases production of stomatomedin (stimulate
  cell growth and division)

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How do different forms of mortality effect
overall population growth??
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Internal regulation of growth - endocrine system

• Anabolic steriods stimulate growth
• testosterone in males
• estrogen in females
• corticosteroids in both sexes

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Internal regulation of growth - endocrine system

• Thyroid hormones stimulate growth
• Also regulate metamorphosis

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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.)

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Fish growth is indeterminate

• Advantages to indeterminate growth
• larger size yields greater efficiency

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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

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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