The Effects of temperature and Density on
year of young (YOY) Rock Bass
(Ambloplites rupestris) Growth in Gull
Lake
Biotic and abiotic Factors that
affect fish growth and survival
•
•
•
•
•
Food availability
population density
other potential competitors
predation pressure
temperature
Temperature
• Temperature affects environment of YOY fish,
which in turn affects growth rates, metabolism and
ingestion
• 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
greatest
Density
• 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
Results
• 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
average
• 1992,96,97 also showed low density
numbers
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
preferendum
• 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
YOY