Research Article

Long-term changes in the diversity, abundance and size composition of deep sea demersal teleosts from the Azores assessed through surveys and commercial landings

¹ IMAR Institute of Marine Research, University of the Azores, 9901-862 Horta, Portugal
² Okeanos R&D Centre, University of the Azores, 9901-862 Horta, Portugal
³ MARE Marine and Environmental Sciences Centre, University of the Azores, 9901-862 Horta, Portugal
⁴ Faculty of Science and Technology, Department Oceanography and Fisheries, University of the Azores, 9901-862 Horta, Portugal

^* Corresponding author: regisvinicius@gmail.com

Handling Editor: Flavia Lucena Fredou

Received: 14 March 2019
Accepted: 4 October 2019

Abstract

To obtain important baseline information about population dynamics and to provide valuable insights about the possible effects of artisanal fishing on the demersal fish community, this study had three specific objectives: (1) to update the annotated list of demersal teleost species occurring in the Azores (mid-North Atlantic); (2) to describe their depth distribution and related fishery information; and (3) to evaluate annual changes in their observed abundance and length composition. To do this, a time series with about 25 years of scientific data from the commercial fishery and surveys was analyzed. The demersal teleost community was represented by 213 species, predominantly deep-water species, reflecting the main marine habitat in the Azores region. Fishery takes place mainly in the intermediate strata (200–600 m), where the most commercially important species occur. No changing in the fork length (L_F) distribution toward small individuals caused by size-selective fishing was detected in this study. The high variability observed in the L_F data indicates the need for more accurate studies considering alternative statistical analyses (e.g., generalised linear models) to examine the possible factors (e.g. depth coverage, gear configuration, soak time, and fishing area) that cause this variability. On the other hand, the abundance indices of some commercially important species appear to have declined (Phycis phycis, Pontinus kuhlii, Conger conger, Beryx splendens and B. decadactylus), while others appear to be more stable (Helicolenus dactylopterus) or even increasing (Mora moro). Although the available data are insufficient for a formal assessment on the status of exploited populations, the long-term analysis of commercial landings and survey data was used as a basis to assess deep sea demersal teleost fisheries of the Azores, under a precautionary approach.