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 temp- base 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