The Effects of temperature and Density on
year of young (YOY) Rock Bass
(Ambloplites rupestris) Growth in Gull
Biotic and abiotic Factors that
affect fish growth and survival
Food availability
population density
other potential competitors
predation pressure
• Temperature affects environment of YOY fish,
which in turn affects growth rates, metabolism and
• Therefore growth is dependant on temperature, for
which there is an Optimum temperature for
Growth (Kelly,99)
• Optimum Temp is calculated 2-3 degrees below
temp where intake of food and metabolism is
• Definition: estimated # of fish in population
• if population is high, competition and
search for food s more intense therefore
limiting growth in YOY (Leslie,93)
• fish growth is influenced by quantity of
energy expended for activity
• activity levels are expected to rise with
increasing population (Holm,99)
Temperature Dependant Model
• Only above a given temp. will fish begin to
gain mass and promote growth (Kelly,99)
• therefore as temperature increases so
should YOY growth
• must find the YOY length for Rock bass
using Peterson Method, due to high
variability std deviations were calculated
• max length cut off was 55mm
Temperature Dependant Model
• Daily temperatures must be converted to
Growing Degree Days (mean daily tempbase temp), 12c air temperature was used
for base temperature for rock bass
Density Dependant Model
• Use seine haul results to estimate catch per
unit effort
• catch per unit effort gives an estimation on
density of a population (Bagenal, 78)
• its expected that a negative relationship
would be shown between density and
average fish length or as density increased,
fish length decreased
• 1992,96,97 had lowest amount of Growing
degree days, 2000 was 856.1 GDD’s
• 41mm was found to be average YOY length
over ten years, 2000 YOY length was 42mm
• 1992,96,97 showed YOY lengths below
• 1992,96,97 also showed low density
Interpretation of Data
• Problems with a high degree of variability
within data and small sample set, try to
increase sample size in future
• 1992,96,97 years that had smaller YOY
lengths and the fewest GDD’s this would
support the positive correlation that with
increased GDD’s we should see increase in
fish length
Interpretation of Data
• McClendon and Rabeni found that
temperature has a major impact on fish
growth when its below the fishes
• Minden never reached this temp of 25 c set
by Carlander for rock bass, therefore
temperature dependant growth was
obeserved, substatiating the temperature
Dependant Model
Interpretation of Data
• Density dependant model was rejected,
because we should have observed a
increase in fish length as density decreased
• however 1992,96 and 97 showed low
densities and the fish size decreased
• seine hauls should be increased for larger
sample sizes
• perhaps openings in nets at to small for