Aquatic Habitat In the Ogunquit River

Salvelinus fontinalis, or Eastern Brook Trout, is a cold-water fish species native to Northeastern America. The abundance of this indicator species has drastically declined across their historic range due to habitat fragmentation and the geomorphological impacts of deforestation and mill damming. Development in the watershed from the 20th century onward, combined with climate change, perpetuates the impacts of early colonial activities on aquatic habitat. Limited published data exists on stream network impactedness and the quality of habitat in the Ogunquit River, a low-gradient coastal system, spanning a watershed of over 50 square kilometers. Initial efforts to assess general aquatic habitat and conditions for brook trout were done by archival research on settlement patterns and catchment scale research on landscape characteristics using GIS. This broader work was combined with river-network-scale-habitat and stream-feature-mapping along with reach-scale measurements of water quality at three sites with multiple transects along the mainstem. While the mainstem of the Ogunquit is classified as perennial, observations during a drought year showed the stream was intermittent and dry throughout many reaches in the mainstem. Results also showed that summer thermal regimes were unsuitable for brook trout at sites downstream closer to development, while dissolved oxygen conditions upstream were unsuitable for brook trout. Macroinvertebrate sampling via rock baskets showed a lack of sensitive organisms and benthic diversity upstream. Though greater proportions of sensitive organisms comprised samples at downstream sites, total abundances were similar or lower. This study provides environmental data about the suitability of brook trout habitat in Ogunquit River in the context of historical landscape processes