Assessment of Road Culverts as Passage Barriers to Brook Trout (Salvelinus fontinalis) and Brown Trout (Salmo trutta) in Pennsylvania Headwaters

Road culverts can pose as barriers to migratory fish and other aquatic organisms, which can lead to small isolated populations. To categorize the degree to which culverts prevent fish movement, watershed managers use physical measurements to classify culverts as “green” if they are passable, “red” if they are impassable, or “gray” if passability cannot be determined. The Little Bear Creek watershed, a small subwatershed within Loyalsock Creek, contains several road culverts that fell within the “gray” category. It is unknown to us whether or not the culverts falling within this category are indeed barriers to migratory fish, especially trout. To measure how passable these culverts are, we tagged 486 brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) with passive integrated transponder (PIT) tags throughout the Little Bear watershed, particularly upstream and downstream of the three “gray” culverts. Antenna arrays were constructed on the upstream side and downstream side of each culvert, as well as a control site lacking anthropogenic barriers to trout movement. In addition to tracking whether or not the culverts are passable, the arrays will reveal the exact time of movements through culverts. This will allow us to test for correlations with stream flow, water temperature, and other stream conditions that may influence trout movements. By “ground-truthing” culvert assessment methods, we anticipate our study will ultimately help watershed managers better prioritize culverts for removal or replacement