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 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 – 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 I = energy ingested M = energy used to maintain healthy tissues M = energy used to maintain healthy tissues G = energy for growing somatic tissue G = energy for growing somatic tissue R = energy for reproduction R = energy for reproduction E = energy “lost” through inefficiency of energy transfers, etc. 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 food availability competition with other fish for food competition with other fish for food time spent hiding from or escaping predators time spent hiding from or escaping predators time spent defending a territory time spent defending a territory

10. Growth Rate  Anything in the internal or external environment that increases or decreases M: temperature temperature dissolved oxygen dissolved oxygen toxins - NH 4 +, heavy metals, organic toxins toxins - NH 4 +, heavy metals, organic toxins

11. Growth Rate  Energy for growth is a tradeoff with energy for reproduction general pattern: grow first, then reproduce general 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)

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) 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 appetite increases food conversion efficiency increases food conversion efficiency increases production of stomatomedin (stimulate cell growth and division) 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?) (how do you measure this?) 2. Is growth always positive? 3. 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/L 3 w=weight, L = length

28. 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. b.Can’t interfere with recapture efforts either. c.Expensive d.Time consuming POPULATION SIZE GROWTH

29. Raise in a controlled environment (good for aquaculture) GR =100 (log e W f -log e W i )/t f -t i )

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 testosterone in males estrogen in females estrogen in females corticosteroids in both sexes 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.) 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 larger size yields greater efficiency

38. Fish growth is indeterminate  Advantages to indeterminate growth: larger size yields greater efficiency larger size yields greater efficiency larger size yields more food options larger size yields more food options faster swimmingfaster swimming larger gape sizelarger gape size better sensory range & acuitybetter sensory range & acuity

39. Fish growth is indeterminate  Advantages to indeterminate growth: larger size yields greater efficiency larger size yields greater efficiency larger size yields more food options larger size yields more food options larger size reduces number of potential predators larger size reduces number of potential predators swimming speedswimming speed gape sizegape size