Grenadier abundance examined at varying spatial scales in deep waters off Newfoundland, Canada, with special focus on the influence of corals

Abstract

There is a growing body of research examining the effects of corals on fish communities, species abundances, and biodiversity. Yet, few studies have quantitatively examined what factors are influencing the distribution of individual fish species. In general, many researchers believe they know what influences the distribution of grenadiers on large spatial scales, but numerous studies have shown the distributions of organisms are often determined by various factors that change in relative importance when viewed at differing scales. Our study used video collected from three deep canyons off Newfoundland, Canada (North west Atlantic) to examine how the factors apparently influencing the distribution of four grenadiers (Macrouridae: Coryphaenoides rupestris, Coryphaenoides carapinus, Nezumia bairdii, and Macrourus berglax) change when assessed at varying spatial scales. We paid special attention to the influence of deep-water corals found in the study area (large gorgonians/antipatharians, small gorgonians, sea pens, soft corals, and cup corals). The factors that influenced grenadier presence and/or abundance (and the magnitude of this effect) varied as different sampling resolutions were examined. We found C. rupestris abundance was positively related to cup coral abundance in transects longer than 10 m, likely as a result of similar habitat preferences between both taxa. When significant relationships between depth and C. rupestris presence and/or abundance were found, they were always negative. Depth was a significant predictor of C. carapinus abundance in transects longer than 10 m. Very few predictors of M. berglax abundance or presence could be found. Depth and the number of small gorgonians were consistent predictors of N. bairdii abundance.