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Use of side-scan sonar for estimations of Crassostrea brasiliana (Lamarck, 1819) stocks in subtidal banks on the south coast of Brazil

Authors :
Gisela Geraldine Castilho Westphal
Antonio Ostrensky
Source :
Brazilian Journal of Oceanography, Vol 64, Iss 1, Pp 49-56 (2016)
Publication Year :
2016
Publisher :
Universidade de São Paulo, 2016.

Abstract

Abstract Uncontrolled extractivism has led to a worldwide reduction in oyster stocks. The use of new and more efficient management tools for impacted environments must increase. The application of such tools requires previous biological and environmental knowledge of the resident populations of these bivalve mollusks. Technical difficulties are usually associated with studies of submerged oyster banks, and these difficulties result in a considerable lack of biological data on the oysters that inhabit subtidal zones. This study aimed to survey Crassostrea brasiliana (also known as C. gasar) stocks in submerged banks and to evaluate a method with which to measure the extent of the banks and identify and quantify the oysters in the banks with the use of side-scan sonar. This study was conducted on 10 oysters banks located in the subtidal zone of Guaratuba Bay, on the south coast of Brazil. The prospection of all these banks was later validated by diving, and oyster samples (n = 20/bank) were collected for species identification with a molecular method. Only one bank contained oysters that were generically classified as Crassostrea sp.; those in the remaining banks being identified as C. brasiliana. The prospected banks contained oysters of various sizes (average 1.5 m, n = 1,107) that were heterogeneously scattered in the riverbeds. The total number of oysters in the 10 sampled banks was estimated to be 21,159.13 oysters or 1 oyster/4.5 m², which represents a low oyster density in the study site. The results validate the use of side-scan sonar as an efficient means with which to prospect for oysters in banks located within subtidal zones.

Details

Language :
English
ISSN :
1982436X and 16798759
Volume :
64
Issue :
1
Database :
Directory of Open Access Journals
Journal :
Brazilian Journal of Oceanography
Publication Type :
Academic Journal
Accession number :
edsdoj.332113522f2c43d7bb600a06d60a0e8f
Document Type :
article
Full Text :
https://doi.org/10.1590/S1679-87592016104506401