An investigation of patterns of deep-sea demersal fish metabolism and feeding rates

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The deep sea is the largest habitat on earth. Many studies of deep-sea animals have documented feeding habits and regional and depth related patterns in biomass, abundance, and community composition. Now, the critical need for deep-sea benthic communities is information on metabolic rates. Metabolic rate sets the pace of many processes such as resource utilization, growth, and reproduction which in turn affect many ecological processes. The general absence of this information has been an obstacle to constructing dynamic food webs which then help the oceanographic community to ask better questions about how the deep sea works. Two general hypotheses have been advanced with which to predict the metabolic rates of organisms. The recent, and controversial, Metabolic Theory of Ecology claims to explain the majority of variation in metabolism using temperature and body mass alone. However, studies of many deep-sea pelagic animals groups, show significant declines in metabolic rates with depth that cannot be explained by this model. Another model, the Visual Interactions Hypothesis attempts to explain these declines in metabolic rate as the result of the decrease in the evolutionary selection pressure for sustained locomotory capability, a feature common in most fishes, due to declining light levels and reaction distances between predators and prey. Very little data for deep-sea benthic or demersal animals are available with which to evaluate these models. In fact, very little data is available on the metabolic rates of deep sea fishes or the role that these fish play in energy flow through the deep sea food web. In this project a unique dataset for deep sea fishes will be collected to assess their metabolic rate and see which of the models described above can be used to reasonably estimate their energetic demands. To do this the metabolic rates of fishes from 100-4000 m depth will be measured using novel in situ respirometers and the data will be used to quantify their energetic demands. Demersal fishes are an ideal group to study as many of them are top predators which play a vital role in various marine communities by controlling prey populations and therefore influencing energy flow through the deep sea food web. It is important to gather key energetic information on deep-sea species soon because of expanding human activities in their environment as deep-sea fisheries continue to exploit demersal fishes. Metabolic rates are tied to growth rates and together they are integral to estimating the productivity of fish stocks. By developing information for food-webs this study could also shed light on how these fisheries will affect the ecosystems by removing top predators. The investigators will also be involved the training of undergraduate and graduate students as well as providing teacher-at-sea opportunities to enhance curriculum development for the participants.