LE3 .A278 2022

2022

Stewart, Don
Rawlings, Timothy

Acadia University

Master of Science

Masters

Biology

Biology

The Atlantic Sea Cucumber, Cucumaria frondosa (Echinodermata, Holothuria) is a suspension-feeding sea cucumber found throughout the North Atlantic. Recently, interest has emerged in developing a trawl fishery for this species in Nova Scotia, specifically on the Scotian Shelf. As new fisheries emerge in Canada, precautionary management entails examining underlying genetic structure to inform fisheries stocks. This is also important to follow international efforts from organizations such as the Convention on Biological Diversity (CBD) to characterize and manage biodiversity as a biological resource. Little is known about the population genetics of this species, including connectivity across the North Atlantic. One previous study examined genetic structure of C. frondosa in the North Atlantic using Cytochrome oxidase c subunit 1 (COI) and found evidence of minor structure between Europe and North America, but no regional structuring. When this dataset was augmented with additional individuals and sampling sites in this study, the minor structuring between continents remained, but pairwise Fst values between study sites changed. In addition, my results showed that the way DNA sequence data is trimmed can significantly redistribute haplotypes between study sites, implying the need for more standardized methodology for sequence trimming in future analyses. Regional genetic structuring between the coasts of Atlantic Canada and Iceland was re-assessed with a higher resolution method, Restriction Site-Associated DNA Sequencing (RADseq). Overall, both COI and RADseq analyses supported the hypothesis of one metapopulation of C. frondosa across the North Atlantic, with the RADseq analysis indicating that sea cucumbers off the coasts of Iceland and Atlantic Canada constituted at least two subpopulations. In addition, a minor difference between the study site in NAFO Zone 4X and the remainder of Atlantic Canada was found. Thus, there may be greater amounts of genetic structuring within Cucumaria frondosa on the Scotian Shelf than previously thought. There is also evidence that methodology (e.g. marker selection, sequence trimming, sample size) can impact the results of population genetic analyses. The results of this thesis have established a baseline of population structuring for C. frondosa in the North Atlantic, with at least two subpopulations between North America and Europe, but they also demonstrate the need for standardized methodology for trimming sequence data and even selecting appropriate markers for research questions. This will be important for further work on establishing genetic data as a biological resource and for informing long-term management of fisheries.

The author retains copyright in this thesis. Any substantial copying or any other actions that exceed fair dealing or other exceptions in the Copyright Act require the permission of the author.

https://scholar.acadiau.ca/islandora/object/theses:3882