Fish distribution during smolt migration in the Penobscot Estuary, ME

Estuaries are complex and dynamic ecosystems. The Penobscot Estuary is particularly important because it harbors a suite of imperiled diadromous fish species. In order to properly manage these populations, it is imperative to understand their distribution and ecology. My study focuses on May because endangered Atlantic salmon migrate seaward then. Successful emigration of these smolts is important to the population's overall fitness. One potential way to increase the likelihood of migratory success (survival) is to decrease their risk of predation. Assuming that predators in this system are generalists, overall smolt predation may be reduced by having a larger selection of alternative prey (other fish species). We hypothesize that diadromous fish abundance is increasing as a result of recent (2012-2013) dam removals. To explore this hypothesis, I used hydroacoustic methods to characterize the distribution patterns of alternative prey (TL=10-30 cm). I found that peak fish abundances occurred in the mid-estuary, especially during mid-May, and depth distribution patterns varied weekly. By understanding these seasonal, longitudinal, and vertical distribution patterns, I explored potential interactions of other fish populations as prey buffers to emigrating smolts.