Setting a species-specific population model in the context of an aquatic food web model: a case study for the Topeka shiner

Transcription

1 Setting a species-specific population model in the context of an aquatic food web model: a case study for the Topeka shiner Amelie Schmolke 1 Steven Bartell 2 Colleen Roy 1 Nicholas Green 1 Dan Perkins 1 Nika Galic 3 Richard Brain

2 Goals Population-level risk assessment for threatened and endangered species Recommendation by the National Academy of Sciences (NAS): use of population modeling approaches for the purposes of assessing potential risks of pesticides under the Endangered Species Act Develop a modeling approach capable of evaluating potential direct and indirect effects of pesticides on the Topeka Shiner Individual-based model (IBM) for populations with species-specific representation of life history and diet Link to an aquatic food web model (CASM) for indirect effects Flexible approach to assess various food web mediated stressors 2

3 Topeka shiner (Notropis topeka) Listed as endangered under ESA for its entire range Small fish (up to 7cm) with short life span (up to 3 years) Habitat: small water bodies with no or low flow (e.g., ponds, oxbows, low-flow areas of streams) Threats to species and its habitat listed recovery plan (FWS): Changes in stream hydrology Agricultural impacts on water quality Road and bridge construction Impoundments Urbanization Dredging Introduction of predators 3

4 Topeka shiner diet Omnivorous diet dominated by: Small crustaceans Insect larvae Plant matter Detritus Literature data from stomach content studies used to parameterize diet preferences in functional response implementation Importance of detritus in diet unclear 4

5 Assessing potential stressors on populations Population-level effects Effects of stressors on populations are dependent on the life history of a species Fish could potentially experience indirect (food web meditated) effects from stressors such as pesticides Representation in a hybrid model approach CASM-TS: aquatic food web model captures dynamic of diet available to populations Hybrid model with TS-IBM: species-specific model captures the life history and bioenergetics of individual Topeka shiners, daily input of diet biomasses from CASM-TS Hybrid model with daily feedbacks (linked): TS-IBM receives daily biomasses of diet groups, feed-back to CASM after consumption by Topeka shiner 5

6 Assessing potential direct and indirect effects Schematic of model linking 6

7 TS-IBM: Population model for Topeka shiner Individual-based model (IBM), not spatially explicit Life history and individual growth (fish bioenergetics model and functional response to prey density) Calibrated to fish sizes reported for Topeka shiner Interaction of fish within the population: Competition for food Density-dependent egg and larval survival Single-year simulation: Comparison of Topeka shiner model outputs 7

8 Population-level impacts of reduction in food availability Systematic reduction in availability of food groups (input to TS-IBM) Detritus preference scenarios: how do population-level effects in food reductions depend on diet preferences? Population-level outcomes after 50 years of simulations 50-year simulation (TS-IBM): Topeka shiner population trends with different food availabilities 8

9 Population-level impacts of reduction in food availability 9

10 Summary Hybrid model approach for risk assessment to listed fish populations: Combination of species-specific population model with realistic representation of the aquatic food web Can be used as tool to assess food-web mediated effects of stressors Uncertainties about species ecology and interactions with effects can be tested explicitly: example of diet preference for detritus Temporal pattern of stressors, combinations of different stressors and conditions of different waterbodies can be simulated 10

11 Outlook Testing the hybrid model with simulated exposure to atrazine (indirect effects on Topeka shiner populations) Extend application of hybrid model to address conservation questions (off-channel habitat restoration): What makes a waterbody a suitable habitat for Topeka shiner? What waterbody conditions and/or community composition may impact Topeka shiner population performance over time? Wed, 4pm, platform presentation 461 by Steven Bartell, room 204: Combining an individual-based model and an aquatic food web-ecosystem model to assess ecological risks: A case study with the endangered Topeka shiner 11

12 Thank you! Co-authors: Steven Bartell 2 Colleen Roy 1 Nicholas Green 1 Dan Perkins 1 Nika Galic 3 Richard Brain 3 Contact: Amelie Schmolke (schmolkea@waterborne-env.com)