Patterns of Growth in Patterns of Growth in FishesFishes

Grow and Survive to ReproduceGrow and Survive to Reproduce

Growth patterns in fishesGrowth patterns in fishes

Context for study of growth:Context for study of growth: to “succeed”, a fish must reproduce to “succeed”, a fish must reproduce

viable offspringviable offspring to reproduce, a fish must survive long to reproduce, a fish must survive long

enough to reach maturityenough to reach maturity to reach maturity, a fish must grow:to reach maturity, a fish must grow:

Factors Affecting GrowthFactors Affecting Growth

HormonesHormones – – Growth hormone secreted by pituitary Growth hormone secreted by pituitary

– Steroid hormones from gonads– Steroid hormones from gonads TemperatureTemperature

– – Most important environmental factor Most important environmental factor – Growth increases up to a point – Growth increases up to a point – Fish tend to prefer temperatures where their– Fish tend to prefer temperatures where their

growth is maximal growth is maximal

Growth patterns in fishesGrowth patterns in fishes

Dissolved OxygenDissolved Oxygen – – More is betterMore is better

AmmoniaAmmonia – – High concentrations slow growthHigh concentrations slow growth

SalinitySalinity – – Growth is altered when fish are not in their Growth is altered when fish are not in their optimum salinityoptimum salinity

Growth patterns in fishesGrowth patterns in fishes

Competition Competition

– – Generally slows growthGenerally slows growth FoodFood

– – Availability & quality affect growthAvailability & quality affect growth PhotoperiodPhotoperiod

– – Longer days increase growthLonger days increase growth

Growth patterns in fishesGrowth patterns in fishes

• • Age & MaturityAge & Maturity – – Growth is rapid early in life Growth is rapid early in life – With maturity more energy is diverted to gonadal – With maturity more energy is diverted to gonadal tissue tissue

– Larger fish need more energy to maintain body– Larger fish need more energy to maintain body ConditioningConditioning (Weight lifting for fish??)(Weight lifting for fish??)

Keys to success:Keys to success:

GROWGROW

SURVIVESURVIVE

REPRODUCEREPRODUCE

Bioenergetic contextBioenergetic context

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

Bioenergetic contextBioenergetic context

Bioenergetic equation:Bioenergetic equation: I = M + G + R + EI = M + G + R + E

I = energy ingestedI = energy ingested M = energy used to maintain healthy tissuesM = energy used to maintain healthy tissues G = energy for growing somatic tissueG = energy for growing somatic tissue R = energy for reproductionR = energy for reproduction E = energy “lost” through inefficiency of E = energy “lost” through inefficiency of

energy transfers, etc.energy transfers, etc.

Growth RateGrowth Rate

Anything in the internal or external Anything in the internal or external environment that increases or environment that increases or decreases I:decreases I: food availabilityfood availability competition with other fish for foodcompetition with other fish for food time spent hiding from or escaping time spent hiding from or escaping

predatorspredators time spent defending a territorytime spent defending a territory

Growth RateGrowth Rate

Anything in the internal or external Anything in the internal or external environment that increases or environment that increases or decreases M:decreases M: temperaturetemperature dissolved oxygendissolved oxygen toxins - NHtoxins - NH44

++, heavy metals, organic toxins, heavy metals, organic toxins

Growth RateGrowth Rate

Energy for growth is a tradeoff with Energy for growth is a tradeoff with energy for reproductionenergy for reproduction general pattern: grow first, then reproducegeneral pattern: grow first, then reproduce increased size -->increased size -->

• increased fecundity (females)increased fecundity (females)• increased territorial success (males, females)increased territorial success (males, females)• increased metabolic efficiency (to a point)increased metabolic efficiency (to a point)

Fish growth often is periodicFish growth often is periodic

Seasonal variation in temperature, food Seasonal variation in temperature, food availability, spawning activity, can availability, spawning activity, can cause seasonal growth cessationcause seasonal growth cessation

(Can you think of examples where this might (Can you think of examples where this might happen?)happen?)

Fish growth often is periodicFish growth often is periodic

Seasonal variation in temperature, food Seasonal variation in temperature, food availability, spawning activity, can cause availability, spawning activity, can cause seasonal growth cessationseasonal growth cessation

If periods are regular (e.g., annual or If periods are regular (e.g., annual or daily), a record of growth and no-daily), a record of growth and no-growth periods is formed in hard growth periods is formed in hard structures:structures: scales, fin spines or rays, vertebral centra, scales, fin spines or rays, vertebral centra,

opercle bones, ear bones (otoliths)opercle bones, ear bones (otoliths)

Fish growth often is periodicFish growth often is periodic Periodic growth marks allow estimation Periodic growth marks allow estimation

of growth rates by counting and of growth rates by counting and measuring distances between growth measuring distances between growth checkschecks

Endocrine Growth RegulationEndocrine Growth Regulation

Pituitary growth hormone:Pituitary growth hormone: increases appetiteincreases appetite increases food conversion efficiencyincreases food conversion efficiency increases production of stomatomedin increases production of stomatomedin

(stimulate cell growth and division)(stimulate cell growth and division)

How do different forms of mortality effect overall population How do different forms of mortality effect overall population growth??growth??

Internal regulation of growth - Internal regulation of growth - endocrine systemendocrine system

Anabolic steriods stimulate growth:Anabolic steriods stimulate growth: testosterone in malestestosterone in males estrogen in femalesestrogen in females corticosteroids in both sexescorticosteroids in both sexes

Internal regulation of growth - Internal regulation of growth - endocrine systemendocrine system

Thyroid hormones stimulate growthThyroid hormones stimulate growth Also regulate metamorphosisAlso regulate metamorphosis

Fish growth is indeterminateFish growth is indeterminate

Growth continues throughout life cycleGrowth continues throughout life cycle limits to ultimate size are BIOTIC (food limits to ultimate size are BIOTIC (food

availability, metabolic efficiency) and not availability, metabolic efficiency) and not MECHANICAL (counteracting gravity, etc.)MECHANICAL (counteracting gravity, etc.)

Fish growth is indeterminateFish growth is indeterminate

Advantages to indeterminate growth:Advantages to indeterminate growth: larger size yields greater efficiencylarger size yields greater efficiency

Fish growth is indeterminateFish growth is indeterminate

Advantages to indeterminate growth:Advantages to indeterminate growth: larger size yields greater efficiencylarger size yields greater efficiency larger size yields more food optionslarger size yields more food options

• faster swimmingfaster swimming• larger gape sizelarger gape size• better sensory range & acuitybetter sensory range & acuity

Fish growth is indeterminateFish growth is indeterminate

Advantages to indeterminate growth:Advantages to indeterminate growth: larger size yields greater efficiency larger size yields greater efficiency larger size yields more food optionslarger size yields more food options larger size reduces number of potential larger size reduces number of potential

predatorspredators• swimming speedswimming speed• gape sizegape size