Towards sustainable fishery management for skates in South America: The genetic population structure of Zearaja chilensis and Dipturus trachyderma (Chondrichthyes, Rajiformes) in the south-east Pacific Ocean.

Carolina Vargas-Caro,Jennifer R Ovenden,Michael B Bennett,Carlos Bustamante,Tzen-Yuh Chiang

doi:10.1371/journal.pone.0172255

Abstract

The longnose skates (Zearaja chilensis and Dipturus trachyderma) are the main component of the elasmobranch fisheries in the south-east Pacific Ocean. Both species are considered to be a single stock by the fishery management in Chile however, little is known about the level of demographic connectivity within the fishery. In this study, we used a genetic variation (560 bp of the control region of the mitochondrial genome and ten microsatellite loci) to explore population connectivity at five locations along the Chilean coast. Analysis of Z. chilensis populations revealed significant genetic structure among off-shore locations (San Antonio, Valdivia), two locations in the Chiloé Interior Sea (Puerto Montt and Aysén) and Punta Arenas in southern Chile. For example, mtDNA haplotype diversity was similar across off-shore locations and Punta Arenas (h = 0.46–0.50), it was significantly different to those in the Chiloé Interior Sea (h = 0.08). These results raise concerns about the long-term survival of the species within the interior sea, as population resilience will rely almost exclusively on self-recruitment. In contrast, little evidence of genetic structure was found for D. trachyderma. Our results provide evidence for three management units for Z. chilensis, and we recommend that separate management arrangements are required for each of these units. However, there is no evidence to discriminate the extant population of Dipturus trachyderma as separate management units. The lack of genetic population subdivision for D. trachyderma appears to correspond with their higher dispersal ability and more offshore habitat preference.

Highlights

The skates (Family Rajidae) form one of the largest groups within the batoids, with 27 genera and about 250 species [1, 2]
This study provides a genetic analysis of populations of Zearaja chilensis and Dipturus trachyderma, two economically important elasmobranch fishes in South America
It is interesting that mitochondrial genome provides resolution on population structure, even though mitochondrial DNA (mtDNA) variation in elasmobranchs is notoriously low [70] and relatively low numbers of single nucleotide polymorphisms (SNPs) were found in the mitochondrial control region (mtCR) of these two longnose skates

Summary

Introduction

The skates (Family Rajidae) form one of the largest groups within the batoids, with 27 genera and about 250 species [1, 2]. Longnose skates (Tribe Rajini) have a worldwide distribution, inhabiting mostly marine environments from the sublittoral zone to depths of about 3,000 m [1, 2]. Most studies on skates rely on fishery catch data to define a species’ distribution, abundance, dispersal potential and to detect demographic fluctuations [13, 14]. Such data are generally insufficient to allow different stocks to be distinguished, as is required for sound fisheries management practices [15]. Molecular analysis has become an important tool in the study of exploited fish populations [16], and is frequently applied to examine stock structure and connectivity, and to identify species from body parts, such as fins and carcasses [17,18,19,20,21,22,23], each of which can aid fisheries management and conservation efforts [22,23,24,25]

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