The Development of Molecular Techniques for the Conservation of Captive Elasmobranchs

Abstract

The loss of biodiversity is one of the most critical environmental problems facing conservation biologists. One of the worst affected vertebrate lineages is the Elasmobranchii, a subclass of cartilaginous fish containing the sharks, skates and rays. Elasmobranchs are often extremely vulnerable to exploitation, as their low rates of population growth leave them unable to respond to increases in fishing pressure. Effective conservation measures are needed and whilst in situ conservation is often very effective, captive breeding programmes can also offer successful ex situ alternatives. Molecular genetic techniques enhance the success of conservation measures. Genetic monitoring can facilitate the unambiguous identification of species for accurate landing data and the genetic management of populations through genotyping, a process essential for captive populations in order to preserve their genetic diversity. DNA is typically obtained from elasmobranchs through invasive fin clips and skin biopsies. However, these methods can cause harm and significant disturbance, which is undesirable, particularly if working with endangered species. There are very few effective non-invasive sampling techniques available for elasmobranchs and their possible applications for ex situ conservation measures have rarely been investigated. In this body of work, I developed a minimally invasive sampling technique suitable for use with different species of elasmobranch. I went on to test the practical applications of the sampling protocol, carrying out DNA barcoding, to accurately identify the samples taken, and microsatellite analysis, to genotype a population of undulate rays (Raja undulata), which are part of a European wide captive breeding programme. The minimally invasive sampling technique proved effective, with 81% of amplified samples correctly identified through DNA barcoding and four times the amplification success rates recorded for ray-type species in comparison to shark-type species. Genotyping the captive population of undulate rays revealed it has maintained fairly high levels of genetic diversity. Early signs of inbreeding were detected, but with the correct genetic management the effects should be reversed. To the best of my knowledge, this is the first time DNA has been collected and amplified from many of these species without the need for invasive tissue samples and I have greatly expanded the geographical sampling of genetic diversity in captive undulate rays. I have shown that the minimally invasive sampling technique is an effective means of obtaining DNA from different species of elasmobranch and can form an inherent part of genetic monitoring programmes. Molecular genetic techniques have a role to play in both the in situ and ex situ conservation of elasmobranchs, and whilst this body of work focused on captive populations, it is hoped these techniques will also prove effective in wild populations.

Date of Award	1 Aug 2017
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Richard Preziosi (Supervisor), Jennifer Rowntree (Supervisor) & John Fitzpatrick (Supervisor)