Patterns of Growth in Fishes

1. Patterns of Growth in Fishes Grow + Survival = Reproduction

2. Growth patterns in fishes • Context for study of growth: • Success = viable offspring • Reproduction = survival to maturity • Maturity = growth

3. Factors Affecting Growth • Temperature– Most important environmental factor – Growth increases up to a point (indeterminant) • – Fish tend to prefer temperatures where their growth is maximal • Hormones– Growth hormone secreted by pituitary – Steroid hormones from gonads

4. Growth patterns in fishes • Dissolved Oxygen– More is better • Ammonia– High concentrations are worse! (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. Bioenergetic context • Growth is the accumulation of somatic (body) tissue that depends on a surplus of energy consumed

8. 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.

9. Growth Rate • Anything in the internal or external environment that increases or decreases intake: • food availability • competition with other fish for food • time spent hiding from or escaping predators • time spent defending a territory

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

11. 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)

12. 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?)

13. 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)

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

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

16. When Am I An Adult? • Juvenile when you still have larval features. • When larval features gone, then (and only then) you are an adult. • Transition can be abrupt! • Growth = metamorphosis • Growth = significant change in body size (material)

17. When Am I An Adult? • REM: Age and size are constantly in a trade off. • More eggs if older, but may die first. • Younger fish often produce fewer eggs and are weaker from the attempt. May die anyway. • Fish under heavy predation pressure will reproduce quickly.

20. What Counts as Growth? • “Growth” in fish is measured in creative ways. 1. Change in amount of body material? (how do you measure this?) • Is growth always positive? • Growth could be a change in calories stored as body (somatic) or reproductive (gonadal) tissue.

21. What Do We Typically Measure?

24. Condition factor (K) -K= w/L3 w=weight, L = length

28. POPULATION SIZE GROWTH • 1. MARK/RECAPTURE • Tagging fish with PIT • (Passive integrated transponder) tags • Dyes • Discs • Implanted magnets • Hanging Tags • Advantage: Good data • Disadvantage: • a. Methods must not interfere with normal fish behavior. • Can’t interfere with recapture efforts either. • Expensive • Time consuming

29. Raise in a controlled environment (good for aquaculture) GR =100 (logeWf-logeWi)/tf-ti)

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

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

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

36. 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.)

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

38. 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

39. 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