Lecture 1:

  • Growth: Change in size (width and length) over time or change in calories stored
  • Storage can be in reproductive tissue
  • Healthy populations will have good fish growth
  • Is a good indicator of fish health
  • Aquaculture: What is the fastest rate of growth that can be achieved?

Simplified Energy Equation:

  • I = M + G + E
  • I = Ingested food energy
  • M = Energy for metabolism, effected by pollution, migration and other changes
  • G = Energy for growth
  • E = Energy excreted
  • Influential factors:
  • Temperature: Most important determinate in growth rate
  • Fish = ectotherm, cold = low growth rate
  • Competition:Intense competition = limits resources and ‘stunts’ growth rate of fish
  • Selective pressure for fish that develop/ growth factor
  • Harvesting can improve this rate
  • Salinity: Important with respects to metabolic rate via osmoregulation processes
  • Low concentration of ammonia = increase growth rate
  • Higher rates of ammonia concentration = decrease growth rate
  • There are several other factors
  • Water levels
  • Stress/ stress response
  • Ph

Condition Factor:

  • K =
  • Units in g/ cm3
  • K= condition factor
  • W = weight of fish in grams
  • L = length in cm
  • Heavier fish tend to be longer as well

Measuring growth:

  • PIT traps – Scan tag with ‘wand’, release back into wild and measures growth rate
  • Age and growth in hard structures (Rings of fish)
  • Scales, ear bone (Otoliths), spine
  • Rate of growth in diameter of bones/spines/scales is proportional with length

Aging structures:

  • Scales, dorsal spine, Cleithra (Jaw bone), otoliths, opercula
  • Scales = easiest because of calcium carbonate grows it
  • Age increase = decrease growth rate, harder to read
  • Growth rings (Circuli) = can be identified with magnification
  • Annulies = Count annuli to determine age – comparison of rings
  • Otoliths = Ear bone
  • Based from alternating transparent rings
  • Can ID older fish easier than scales
  • Size vs age graph -> measure length and use of hard structures
  • Trade-off between growth rate and reproduction

Lecture 2:

Physiology:

  • Many tools (swim tunnel) can help identify traits
  • How do fish work in specific environments?
  • Metabolism, osmoregulation
  • Aids in aquaculture -> how fish growth/ develop
  • Wants to optimise to be most efficient
  • Response of fish under stressful conditions
  • Nitrogenous waste and effects in water properties
  • Changes physiology of fish (stress factors)

List of four main topics for physiology:

  1. Temperature
  2. Water and respiration
  3. Osmoregulation
  4. Nitrogenous waste

Temperature:

  • Ranges with optimal efficiency, changes with species
  • Ectotherms, peak of curve optimal/ preference
  • Lethal temperature (upper and lower values)
  • Also, known as critical temperature
  • Critical temperature = Changes with life stage (egg -> Juvenile -> Adult)
  • Effects of recruitment
  • Temperature = determine geographical range of species
  • Aquaculture = inland with recirculation which is greater because of controlling of optimal temperature

Water and Respiration:

  • Solubility of water is less than air, ~1/3
  • Diffusion = low
  • Density is greater in air, greater energy required to move
  • Therefore, water has less oxygen availability
  • Countercurrent exchange between water and blood in gills
  • Aquatic hypoxia
  • Ice covers can create this environment because oxygen is much less than usual
  • Warm water = greater oxygen but more dead matter

Osmoregulation:

  • Thin membrane in gills = ion and water movement and exchange
  • 2 processes involved
  • Osmoregulation
  • Nitrogenous waste
  • Poor kidney development, therefore uses gills more
  • Fresh water = body has greater sodium concentration than outside
  • Excretes dilute urine
  • Salt water = body has less sodium concentration than outside
  • Drinks water, excretes ions

Nitrogenous waste:

  • Ammonia, urea, or uric acid are the forms of nitrogenous waste
  • Teleost -> bony fish
  • Most fish excrete ammonia, secretion via gills and kidneys
  • Is very toxic (most toxic of the three)
  • Abundance in a water environment allows the nitrogenous waste to be diluted

Swimming:

  • Body form = indicator of mobility
  • Increase efficiency of respiration
  • Decrease cost of locomotion
  • Cruising: Red muscles, aerobic respiration fuels this movement
  • Weak and long
  • Burst: White muscles, anaerobic, allows fish to jump and chase
  • Short and powerful

Lecture 3: No lecture, toured Fisheries facilities in BioSci