Sustainable science in the deep blue sea
Diana is diving deep into the waters of the Azores to find non-harmful ways to document the diversity and abundance of deep-water sharks. Combining environmental DNA (eDNA) samples – taken from depths of as much as 1500 m – with deep-sea baited remote underwater video system (BRUVs) records, she’ll contrast her findings using these two non-invasive methods with those of the existing demersal longline research fishing surveys. Through this project, she hopes to identify the most sustainable ways to monitor the more than 30 deep-sea sharks caught as bycatch by bottom longline and handline fishing around the Azores.
Diana Catarino
For as long as I can remember I have had a passion for nature and its inhabitants, and for the sea in particular. I grew up in a small coastal village close to Sintra in Portugal and spent summer holidays playing at the beach. I was always very curious about all the creatures in the rock pools and would dedicate part of the day to checking what the tide had left on the sand, on the rocks, and in the pools – and I still love doing that today! In my teens, I went on a trip to the Azores,...
Deep-sea elasmobranchs biodiversity and conservation: Assessment and comparison of non-invasive tools for research and monitoring
This project aims to compare the efficiency of two non-invasive methods (eDNA and BRUVs) with deep-sea longline surveys as bio-monitoring tools. We also aim to collect novel information about the biodiversity and spatial distribution of deep-sea elasmobranchs and to identify essential habitats and species hotspots for the sustainable management and conservation of deep-sea fish.
Deep-water elasmobranchs are among the most vulnerable fish species known to date, with nearly half the species in the north-eastern Atlantic listed as at risk by the IUCN. Although fishing for most of the species is prohibited, these elasmobranchs are taken as by-catch in bottom longline fisheries in the Azores. Because current monitoring is carried out mostly by lethal fishing methods, we need to find alternative, non-invasive methods without further compromising the conservation of these vulnerable species.
Many elasmobranchs inhabiting the depths of the ocean live long, reproduce late and produce few pups. All these life-history strategies make them particularly vulnerable to anthropogenic pressures such as fishing, habitat degradation, deep-sea mining and climate change. Knowing the biodiversity of deep-water elasmobranchs, how abundant they are, the habitats that are essential for key stages in their life history, and their spatial ecology and distribution is very important for managing the fishery of these species effectively and sustainably and promoting their conservation. But too little is known. Studying deep-water elasmobranchs is difficult due to their remote habitat and the cost involved and because there is still uncertainty about species identification. Furthermore, traditional bio-monitoring typically relies on fishing methods that are often lethal. To evaluate spatial abundance and biodiversity patterns of deep-water elasmobranchs in the Azores, this project will assess the potential of two non-invasive methods, the innovative environmental DNA (eDNA) sampling and Baited Remote Underwater Video (BRUV), and compare them with a fishing survey. The use of eDNA is especially relevant for monitoring vulnerable species such as deep-water elasmobranchs, as it overcomes many of the limitations of traditional fishing methods and enables species to be identified with high accuracy and resolution from water samples. This methodology has proven its efficiency in tracing elusive species, such as sharks that were thought to be locally extinct, and it can be a powerful tool in detecting cryptic and rare species. It will be the first time this method will be tested on deep-water elasmobranchs. BRUVs is also a promising non-invasive alternative that has been widely used to document the biodiversity, habitat and behaviour of top predators, to detect cryptic species and to estimate local abundances.
- To compare the efficiency of non-invasive methods (eDNA and BRUVs) in assessing deep-water elasmobranchs’ diversity and relative abundances with traditional monitoring techniques (longline fishing).
- To collect new information about spatial patterns of deep-water elasmobranch biodiversity and relative abundance across the Azores EEZ and compare them in protected and non-protected areas.
- To identify areas of essential habitat and species hotspots for the sustainable management and conservation of deep-sea fish.
Summary of main research results/outcomes
The eDNA metabarcoding is a promising tool for monitoring deep-water elasmobranchs in the Azores, showing potential as a complement or alternative non-invasive method to traditional sampling for biodiversity. eDNA showed to be a very efficient method in capturing deep-water elasmobranch biodiversity, with an average of 10 species detected per sample, compared with 3.8 species of deep-water elasmobranchs detected using bottom-longline surveys. However, for species such as sixgills sharks and the flapper skate, both eDNA and bottom longline sampling seem to be less efficient, with few detections. Surprisingly, these BRUVs revealed a great potential for monitoring, with detections in most of the deployments. Therefore, it is suggested that for a comprehensive monitoring of the deep-water elasmobranchs, a multidisciplinary approach, using more than one method, is the more efficient way to ensure the most appropriate monitoring of the deep-water elasmobranchs community.