Levine, Robert2015-01-072019-08-192014-08-18bibid: 8793449https://hdl.handle.net/1813/38916Submarine canyons contain dense aggregations of euphausiids and are ecologically important for many marine predators. At the Northwest Atlantic shelf break, euphausiids play a critical role, supporting diets for top predators and many commercially import species of fish, yet their distribution is poorly understood. The species composition of euphausiid aggregations was examined relative to abrupt changes in topography and variations in environmental conditions along the Northwest Atlantic shelf break. Net sampling was conducted on seven occasions from 2004-2013 within three canyons and two non-canyon sites along the New England shelf break. The objective was to determine if euphausiid biomass and abundance are greater within canyons than at non-canyon sites along the shelf break, and investigate temporal variation in the aggregation structure over five years of repeat sampling within a single canyon. Additionally, we investigated the impact of a warm-core ring on one canyon region during its presence from June to August 2010. Twenty species were identified, of which 6 were coldwater species and 14 were warm-water species. Cold-water species dominated all samples, but only Meganyctiphanes norvegica was significantly more abundant at shallow sites than deep sites. Species distribution and abundance was significantly related to bottom depth, with no significant difference between canyon and non-canyon sites. Interannual sampling showed high variability between years. There appeared to be a relationship between biomass and temperature, though an increased sample size is needed to improve the strength of statistical testing.en-USzooplanktonshelf breakeuphausiiddissertation or thesis