Fisheries Research 191 (2017) 41–48 Contents lists available at ScienceDirect Fisheries Research j ourna l ho me page: www.elsevier.com/locate/fishres Full length article On the way for detecting and quantifying elusive species in the sea: The Octopus vulgaris case study Q. Mauvisseau a , M. Parrondo a , M.P. Fernández b , L. García b , J.L. Martínez c , E. García-Vázquez a , Y.J. Borrell a,∗ a Department of Functional Biology, University of Oviedo, Calle Julián Clavería S/N, 33006, Spain b Centro de Experimentación Pesquera, Dirección de Pesca Marítima, Gobierno Del Principado De Asturias, Gijon, Spain c Sequencing Unit, Edificio Severo Ochoa, C/Julian Claveria S/N, University of Oviedo, Oviedo 33006, Spain a r t i c l e i n f o Article history: Received 22 August 2016 Received in revised form 2 February 2017 Accepted 28 February 2017 Handled by George A. Rose Keywords: Environmental DNA Detection Fisheries Octopus vulgaris Quantification a b s t r a c t Environmental DNA (eDNA) can be a powerful method for assessing the presence and the distribution of aquatic species. We used this tool in order to detect and quantify eDNA from the elusive species Octopus vulgaris, using qPCRs (SybrGreen protocol). We designed species-specific primers, and set up an exper- imental aquarium approach to validate the new molecular tool in different controlled conditions. Field validation was conducted from sea water samples taken from 8 locations within an octopus fishery area in the Cantabrian Sea during February–March 2016. A significant positive correlation between the total biomass (g of O. vulgaris within thanks) and the amount of O. vulgaris eDNA detected (p-value = 0.01261) was found in aquarium experiments. The species was also detected by PCR in 7 of the 8 water samples taken at sea, and successfully quantified by qPCR in 5 samples. This preliminary study and innovative method opens very promising perspectives for developing quick and cheap tools for the assessment of O. vulgaris distribution and abundance in the sea. The method could help in a close future for quantifying unseen and elusive marine species, thus contributing to establish sustainable fisheries. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Growth strategies in the marine sector aim at strengthening the potential for sustainable development in coasts, seas and oceans of Europe. Innovation in all sectors of the blue economy could help to develop all the potential for growth, employment and significant environmental benefits. Local fisheries represent a good snapshot of the lifestyle of many European communities and guaranteeing their future is necessary. They must be scientifically managed to ensure their sustainability over the long term and their benefits for the community. Well-managed fisheries are the source of sustain- able incomes and generate several other economic activities. To drive commercial fisheries towards sustainability while improving the management of small-scale fisheries and aquaculture prac- tices is currently a serious need worldwide (De Melo et al., 2016). Despite many efforts, nearly a third of commercial fisheries glob- ally have already collapsed and only a few of the ocean’s fish stocks have been rigorously assessed (Vasilakopoulos et al., 2014; Smith et al., 2014). Overfishing affects many marine species and destroys ∗ Corresponding author. E-mail address: borrellyaisel@uniovi.es (Y.J. Borrell). marine ecosystems by removing species performing essential func- tions and/or spawning individuals (Howarth et al., 2014). The common Octopus, Octopus vulgaris (Cuvier, 1797) is an elu- sive coastal cephalopod living between the surface and a depth of about 100–150 m (González et al., 2015). The lifetime of the species is estimated to be two years for both males and females (Otero et al., 2007; González et al., 2015). Its biology and ecology are relatively well known (Mangold and Von Boletzky, 1973; Otero et al., 2009; Perales-Raya et al., 2014; Hermosilla et al., 2010, 2011; González et al., 2015), although there are still regional knowledge gaps (González et al., 2015). This cephalopod is the most harvested octopus’s species from the Atlantic and the Mediterranean Sea (Hermosilla et al., 2011) with more than 43,000 t in the world in 2014 (FAO, 2016). Most important fisheries of O. vulgaris occur in the east Atlantic (Guerra, 1981) and it is the major cephalo- pod species in the Cantabrian coast (Spain) (González et al., 2015). This species is of highest interest for the fisheries in that region (Fernández-Rueda and García-Flórez, 2007), as well as in other areas of the east Atlantic. However, to date its population abun- dance and microscale distribution are largely unknown (González et al., 2015). Short lifespan and single breeding of cephalopods means that time available to assess and respond to changes in http://dx.doi.org/10.1016/j.fishres.2017.02.023 0165-7836/© 2017 Elsevier B.V. All rights reserved.