Inferring species interactions through joint mark-recapture analysis.

Area of Science:

• Ecology
• Conservation Biology
• Population Dynamics

Background:

• Introduced species often cause native species declines, but evidence is frequently weak.
• Rigorous demographic analysis, like mark-recapture, is crucial for management but lacks models for interacting species.
• Existing models struggle to jointly analyze species interactions, hindering conservation efforts.

Purpose of the Study:

• Introduce a novel two-species mark-recapture model for joint population analysis.
• Investigate the impact of introduced rainbow trout on endangered humpback chub in the Colorado River.
• Test hypotheses on environmental factors, density dependence, and interspecific interactions affecting humpback chub.

Main Methods:

• Developed a two-species mark-recapture population model allowing vital rates to vary with interacting species abundance.
• Conducted a simulation study to assess model bias and select appropriate models.
• Applied the model to mark-recapture data of humpback chub and rainbow trout from 2009-2016.

Main Results:

• The simulation study showed minimal bias, even with low capture probabilities and high process error.
• Negative relationships were found between rainbow trout abundance and juvenile humpback chub survival, growth, and capture probability.
• Interspecific interactions significantly affected survival and capture, while environmental factors were also important drivers.

Conclusions:

• The new two-species mark-recapture model effectively quantifies impacts of interacting species.
• Introduced rainbow trout negatively affect humpback chub, highlighting the need for management interventions.
• The model framework is adaptable for diverse ecological systems and invasive species research.