Habitat associations and effects of survey expansion on abundance indices and population demographics for 2 deepwater fish species off the Atlantic coast of the southeastern United States

Deepwater fisheries have become increasingly important over the past couple of decades, yet challenges in adequately characterizing relative abundance and population demographics of deepwater stocks have persisted for fishery-independent surveys. Consequently, in stock assessments of the complex of deepwater snapper and grouper species along the Atlantic coast of the southeastern United States, fishery-dependent data have been relied on to track population trends, which may be biased by management actions and fishing behavior. In this study, we investigated the effects of increasing the sampling intensity and spatial scale of a historical deepwater fishery-independent survey on estimates of abundance and population demographics and aimed to identify important habitat associations for snowy grouper (Hyporthodus niveatus) and blueline tilefish (Caulolatilus microps). Increased sampling intensity and spatial expansion of the survey did not significantly affect estimates of abundance for either of these species, but model uncertainty was reduced for snowy grouper. Length compositions differed significantly for snowy grouper. Inclusion of significant covariates related to habitat association into indices of abundance did not affect estimates of abundance or uncertainty for snowy grouper but increased the magnitude of abundance and improved model fit for blueline tilefish. Identifying and incorporating habitat association information into stock assessments are critical for improving the management of data-limited deepwater species in the region.