Otolith shape analysis as a tool for stock discrimination of the black scabbardfish, &lt;i&gt;Aphanopus carbo&lt;/i&gt; Lowe, 1839 (Pisces: Trichiuridae), in Portuguese waters

Inês Farias,Ivone Figueiredo,Ana Rita Vieira,Leonel Serrano Gordo

doi:10.3989/scimar.2009.73s2047

Abstract

The variability in otolith contour shape of black scabbardfish ( Aphanopus carbo ) from Portuguese waters was analysed for stock discrimination purposes. The contour shape of otoliths from specimens caught off mainland Portugal, Madeira and Azores archipelagos was digitised and extracted according to the closed-form Fourier analysis technique. Mainland and Madeira specimens were compared through the adjustment of a MANOVA model to the normalised elliptic Fourier descriptor (NEFDs) obtained for the otoliths of 200 females and 200 males sampled at each area. Significant differences were found between areas and between sexes; the interaction term was not statistically significant. The effect of the area also proved to be significant when samples from the three regions were considered. These results were further supported by the discriminant analysis of the individual NEFDs for which the correct classifications were 87.5-89% when they were considered by sex and total length for the mainland and Madeira, and 90.9-97.7%, when NEFDs from the three areas were compared by sex and fish length. Otolith contour shape was shown to be a possible tool for differentiating between black scabbardfish stocks in the NE Atlantic.

Highlights

The black scabbardfish, Aphanopus carbo Lowe, 1839, is a deep-water species from the family Trichiuridae that is common at depths between 450 and 1300 m and has a world-wide distribution
The main objective of this work was to try answering the questions posed above by comparing the otolith contour shape of specimens caught off the Portuguese mainland, Madeira and the Azores, and by quantifying the differentiation among them
Black scabbardfish specimens were sampled from commercial landings of longliners operating off mainland Portugal (Sesimbra, 38o26’N 9o06’W), the Madeira archipelago, and the Azores archipelago

Summary

Introduction

The black scabbardfish, Aphanopus carbo Lowe, 1839, is a deep-water species from the family Trichiuridae that is common at depths between 450 and 1300 m and has a world-wide distribution. There are records of the species in the NW and NE Atlantic, from Iceland to the south of Madeira Island. In the northeast Atlantic it is one of the leading deepwater species exploited. In Portugal it was the fifth most important fish species in terms of commercial landings in 2007, attaining almost 6.5 thousand tonnes (INE, 2008). The main Portuguese ports where this species is landed are Sesimbra (in mainland Portugal) and several ports in the Madeira archipelago. In the Azores archipelago the species is exploited on an irregular basis

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