Distribution and Feeding Ecology of Bathylagus euryops (Teleostei: Microstomatidae) along the Northern Mid-Atlantic Ridge from Iceland to the Azores

The northern Mid-Atlantic Ridge, from Iceland to the Azores (MAR), ranges in depth from 800 – 4500 m and extends over an area of 3.7 million km2. Recent evidence from MAR-ECO, a Census of Marine Life field project, reported increased abundance and biomass of deep-pelagic fishes below 1000 m on the MAR. Among the fishes sampled, Bathylagus euryops was found to be the biomass-dominant species and ranked third in total abundance. In this thesis, we characterize the distribution and feeding ecology of B. euryops as a function of physical, biological, and life history parameters along a mid-ocean ridge system. Multiple biologically plausible general linear models were fitted to B. euryops catch-per-unit-effort (CPUE) data to investigate the role of various combinations of explanatory variables on the distribution of this species. Results indicated that a model containing categorical depth and geographic location variables provided the most parsimonious description of B. euryops CPUE data. Vertical migration analyses were also conducted to investigate the vertical distribution of B. euryops along the MAR and results indicated that time of day had little influence, whereas ontogeny likely influenced the vertical distribution of B. euryops. To describe the feeding ecology of B. euryops, a general diet composition was determined. Multivariate analyses, including a cluster analysis and a canonical correspondence analysis, were utilized to investigate factors that cause variability within the diet of B. euryops. Results revealed that fish size and geographic location significantly influenced the diet of B. euryops. Furthermore, daily rations were estimated to better understand the role of B. euryops in the food webs of the North Atlantic and results were consistently estimated to be less than 1% of the average wet weight along the MAR. The general trend observed was a southward increase in daily ration estimates along the MAR.