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Understanding Growth Patterns in Fishes: Key Factors for Survival and Reproduction

This comprehensive guide explores the growth patterns of fishes, emphasizing their crucial role in survival and reproduction. It highlights essential factors affecting fish growth, including hormones, temperature, dissolved oxygen, food availability, and competition. Additionally, it discusses the endocrine regulation of growth, the concept of indeterminate growth, and how various environmental influences can lead to seasonal growth variations. Understanding these patterns not only aids in fishery management but also sheds light on the biological and ecological dynamics of aquatic ecosystems.

gwendolyn-fuller
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Understanding Growth Patterns in Fishes: Key Factors for Survival and Reproduction

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  1. Patterns of Growth in Fishes Grow and Survive to Reproduce

  2. 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:

  3. 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

  4. 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

  5. Growth patterns in fishes • Competition – Generally slows growth • Food– Availability & quality affect growth • Photoperiod– Longer days increase growth

  6. 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??)

  7. Keys to success: • GROW • SURVIVE • REPRODUCE

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

  9. 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.

  10. 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

  11. Growth Rate • Anything in the internal or external environment that increases or decreases M: • temperature • dissolved oxygen • toxins - NH4+, heavy metals, organic toxins

  12. 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)

  13. 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?)

  14. 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)

  15. Fish growth often is periodic • Periodic growth marks allow estimation of growth rates by counting and measuring distances between growth checks

  16. Endocrine Growth Regulation • Pituitary growth hormone: • increases appetite • increases food conversion efficiency • increases production of stomatomedin (stimulate cell growth and division)

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

  18. Internal regulation of growth - endocrine system • Anabolic steriods stimulate growth: • testosterone in males • estrogen in females • corticosteroids in both sexes

  19. Internal regulation of growth - endocrine system • Thyroid hormones stimulate growth • Also regulate metamorphosis

  20. 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.)

  21. Fish growth is indeterminate • Advantages to indeterminate growth: • larger size yields greater efficiency

  22. 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

  23. 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

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