Towards integrated adaptive management of an endangered elasmobranch in the North East Atlantic

Increasing use is made of marine protected areas (MPAs) to locally manage and conserve marine biodiversity. Although highly mobile, with complex temporal and spatial movement patterns, many endangered elasmobranchs show site association to critical habitats at important life history stages. Consequently MPAs are considered a key management tool in shark conservation.
Low fecundity, long gestation periods and historical exploitation have precipitated severe declines in spurdog (Squalus acanthias) biomass in the North East Atlantic (NEA). As aggregating species spurdog are identified as both endangered in the NEA (IUCN) and paradoxically as choke species, fouling fishing gear. NEA populations are considered a single stock from tagging data, with wide-ranging regional movements characteristic. Yet recent work suggests some individuals display winter residency within the 'Loch Sunart to Sound of Jura' MPA (Thorburn et al. 2015), originally designated to protect critically endangered flapper skates. Determining the status (source or sink) of current spurdog population(s) in this MPA, and connectivity via contemporary gene flow with other NEA populations, is paramount for viable population management. Identification and integration of residential behaviour may increase management effectiveness by identifying critical areas where MPAs could conserve migratory species.
Our previous genetic analyses revealed little population structure within the NEA, and identified relatives within aggregations (Thorburn et al. 2018), indicating unsuspected vulnerability through erosion of selectable familial variation, making estimates of effective population size, aggregation composition and provenance key questions in managing for viability. Indirect population genetic approaches function well where there is restricted gene flow and prior knowledge of population boundaries, yet these assumptions are difficult to justify for the highly mobile spurdog. Additionally, demographic interpretation of traditional analyses remains challenging, which integrate processes on evolutionary rather than contemporary timescales. However, information contained in the spatial distribution of close kin can provide direct estimates of population connectivity and have been successfully used for defining dispersal kernels, identifying the drivers of juvenile dispersal patterns, and investigating contemporary recruitment dynamics.
Approach: Juvenile and adult contemporary management relevant connectivity will be inferred from spatial distribution of parent-offspring, full- and half-siblings, identified from genome-wide SNP analysis, from the MPA and adjacent sites, and contrasted with indirect estimates of connectivity obtained from maternally inherited mitogenomes (Feutry et al. 2017). Additionally data on close kin pairs (parents and offspring) will be utilised in a close-kin mark-recapture (CKMR) approach to estimate absolute stock abundance. Provenance of individuals will be confirmed by lead isotope analysis utilising isotopic seascape approaches that we have developed and used for a variety of conservation issues.
This QUADRAT (DTP) project will provide training in core and generic skills, along with cutting edge technologies (population genomics, bioinformatics, stable isotopes and multi-elemental fingerprinting) integrating Biodiversity and Earth systems; translating into improved policy and practice for effective conservation management of endangered marine species.
Key questions: Does the existing MPA encompass recruitment areas? What temporal site associations exist? Is philopatry (return to natal sites) evident? Do adult abundance and productivity estimates suggest viable Scottish populations? What management measures are likely to sustain connectivity and viability?