Environmental and Ecological Drivers of Growth in Demersal Fishes Across the Depth Continuum

Fishes display a high degree of diversity in growth rate across the depth continuum. While deep-sea fishes (>500m) generally grow more slowly than fishes in shallow waters, diversity in growth rate persists even at depth. The environmental and/or ecological drivers of fish growth rates across depth have not yet been resolved. We evaluated how temperature, food supply, metabolism, oxygen concentration and phylogeny affected growth rates in demersal fishes from the near-surface to 4000m in depth. We used a meta-analytical approach evaluating 80 studies on growth for a range of species. Data for 55 species met our criteria for inclusion. Collected age and size data were used to calculate growth parameters for each species. Temperature and oxygen data at each species’ habitat were collected from the World Ocean Atlas. Flux of particulate organic carbon to each habitat was estimated with methods from Lutz et al. (2007) and models from the Ocean Productivity data portal at Oregon State University. Growth rates declined with habitat depth as seen in previous studies. Our analysis indicates that temperature and metabolic rate are important drivers of this pattern, lending support for the use of thermal age and metabolism as predictors of growth rate. Food availability, oxygen, and phylogeny appear to have little or no relationship to growth rate. Our results explain ~50% of the variance in growth rate, suggesting that we can reasonably predict growth rates in deep-sea species. More data is necessary for more accurate, species-specific estimates. Predicting the growth of deep-sea fishes has become increasingly urgent as the human footprint in the deep sea widens. Sensitivity of deep-sea fish stocks to overfishing highlights the need to predict their growth and resilience to increasing global stressors such as deep-sea mining and climate change. These results represent a promising step toward accurately modeling growth in fishes across the depth continuum.