Hypothesis

I hypothesize that stream crossing structures that are a physical barrier (have a hang height) will significantly decrease the upstream catch per unit effort (CUE) of stream fish species.

Weak Swimmers

Upstream catch rates of weaker swimming fish species is expected to dramatically decrease as soon as any hang height (>0.01m) is present at the outlet of a culvert stream crossing structure.

---

Fig. 1. Theoretical decrease in catch per unit effort (#fish/s) of weaker swimming fish species 
as a function of culvert hang height (m). 

Strong Swimmers

Stronger swimming stream fish species of the Salmonid family are expected to experience decreased upstream catch rates as culvert hang heights increase. The decline in upstream catch rates, however, is not as rapid as because higher culvert hang heights are required to exceed the jumping abilities of members of Salmonidae.

---

                                                                           Fig. 2. Theoretical decrease in catch per unit effort (#fish/s) of stronger swimming fish                                                                                species as a function of culvert hang height (m).