Title
Bottom trawling on a carbonate shelf: Do we get what we see?
Date Issued
15 January 2021
Access level
open access
Resource Type
journal article
Author(s)
Universidade Federal de Pernambuco
Publisher(s)
Elsevier B.V.
Abstract
Bottom trawling is a common fisheries method and also a widespread scientific sampling method for benthic and demersal species. Selectivity and catchability are usually estimated using different meshes and studies with alternative methods are rare. In this study, to improve the estimation of trawl selectivity, we compare bottom trawl catches and recordings made by a camera fitted on the top of the net. Scientific trawling was conducted along the Northeast Brazilian shelf, a typical carbonate shelf with presence of sponges, coralline bottoms and a high water visibility. In total, 23 taxa (19 species and four genera) were identified in the videos and 30 taxa (25 species and five genera) in the trawls, indicating a higher potential of trawling to record species richness. Overall, no significant differences were observed in the assemblage structure identified by trawling and underwater footages. However, divergences were observed in fish catchability between trawls and videos. Net sampling was more selective for fish with low swimming capacity, while species with shelter and fast swimming capacity seemed to be underestimated. Furthermore, underwater footages allowed for an assessment of the trawling impacts on erect sponges with the observation of the damage on large branching and tubular sponges. The vulnerability of those habitats that concentrate higher fish diversity to mechanical impact raise the need for creation of preventive measures to protect these sensitive areas from commercial fishing operations. The use of less destructive methods is an important survey alternative under special conditions, particularly in conservation areas. In this study the videos could not be used as a complete alternative for the trawls, which presented higher efficiency, however, videos had shown to be a useful complement. Possibly, the speed and height determined by the trawling operation affected the performance of video sampling, being performed in suboptimal conditions. Using dedicated video sampling, such as towed video, could significantly improve its efficiency and compensate the disadvantages observed from the videos.
Volume
213
Language
English
OCDE Knowledge area
Ingeniería oceanográfica
Oceanografía, Hidrología, Recursos hídricos
Subjects
Scopus EID
2-s2.0-85097664492
Source
Continental Shelf Research
ISSN of the container
02784343
Sponsor(s)
We acknowledge the French oceanographic fleet for funding the research expedition ABRACOS 2 and the crew of the R/V ANTEA for their assistance and guidance in the field operations. We also acknowledge the assistance of Dr Thaynã Cavalcanti (UFPE) in the sponges' identification, as well as the help of all participants from the LECOR and BIOIMPACT Laboratories. This study was partially financed by the project PELD-TAMS (Long Duration Ecological Program – Sustainable Tamandaré ; grant number 441632/2016-5 ), by CAPES (Coordination for the Improvement of Higher Education Personnel) through a student grant to Maria Jacqueline Gomes de Barros, Leandro Nolé Eduardo and Alex Souza Lira, and by CNPQ ( National Council for Scientific and Technological Development ) through a productivity research grant to Beatrice Padovani Ferreira and Flávia Lucena Frédou. This work is a contribution of the LMI TAPIOCA and of the PELD-TAMS (grant number 441632/2016-5 ).
This work was funded by the French oceanographic fleet , through the project ABRACOS 2 ( https://doi.org/10.17600/17004100 ), and partially financed by the project PELD-TAMS (Long Duration Ecological Program – Sustainable Tamandaré ; grant number 441632/2016-5 ), by CAPES (Coordination for the Improvement of Higher Education Personnel) and by CNPQ (National Council for Scientific and Technological Development) .
Sources of information:
Directorio de Producción Científica
Scopus