Contributions to Management Strategies in the NE Atlantic Regarding the Life History and Population Structure of a Key Deep-Sea Fish (Mora Moro)

SIMPLE SUMMARY: The growing scarcity of continental shelf and epipelagic oceanic fishes has led to commercial fishing in deeper waters. With this spatial expansion in fishing efforts, some vulnerable deep-sea species have been increasingly captured. To reduce fishing-induced impacts on these resources, information on population traits is required by fishery scientists to produce adequate management advice. In the Northeast Atlantic, the common mora Mora moro has become the main fish species caught by bottom longliners operating in deep waters between 600 and 1200 m. Information about the biology and exploitation status of this species is scarce. This study unravels and highlights important and crucial aspects of the habitat preferences, life-history traits (sex ratio, timing of reproduction, size at maturity, growth pattern, and mortality rates), size structure, and abundance of the M. moro based on scientific surveys and commercial fisheries in the Azores region. Results highlight its vulnerability to overfishing due to its large size, slow growth, low natural mortality, long life span, and late maturity. ABSTRACT: With the commercial fishery expansion to deeper waters, some vulnerable deep-sea species have been increasingly captured. To reduce the fishing impacts on these species, exploitation and management must be based on detailed and precise information about their biology. The common mora Mora moro has become the main deep-sea species caught by longliners in the Northeast Atlantic at depths between 600 and 1200 m. In the Azores, landings have more than doubled from the early 2000s to recent years. Despite its growing importance, its life history and population structure are poorly understood, and the current stock status has not been assessed. To better determine its distribution, biology, and long-term changes in abundance and size composition, this study analyzed a fishery-dependent and survey time series from the Azores. M. moro was found on mud and rock bottoms at depths below 300 m. A larger–deeper trend was observed, and females were larger and more abundant than males. The reproductive season took place from August to February. Abundance indices and mean sizes in the catch were marked by changes in fishing fleet operational behavior. M. moro is considered vulnerable to overfishing because it exhibits a long life span, a large size, slow growth, and a low natural mortality.