Master of Oceanography, Marine Biology and Ecology Mathilde Horaud at The Norwegian College of Fishery Science (NFH) will Wednesday 3rd of June hold her trial lecture and defend her thesis for the PhD degree in Natural Science.
Trial lecture on assigned topic will take place at 10:15: "Environmental and evolutionary impact of aquaculture and fisheries on marine biodiversity"
Later, at 12:15 she will defend her thesis entitled: "Spatio-temporal genomic and phenotypic divergence in Atlantic lumpfish from Norwegian waters: Implications for fisheries and aquaculture management - Adaptive population structure in Atlantic lumpfish ".
Understanding population structure is essential for the sustainable management of exploited marine species, particularly when divergence is subtle, multidimensional, and driven by adaptive rather than neutral processes. Atlantic lumpfish (Cyclopterus lumpus) have gained increasing economic importance in the North Atlantic due to their targeted roe fishery and their extensive use as cleaner fish in salmon aquaculture.
Despite this, fundamental aspects of Atlantic lumpfish wild populations regarding their genetic structure, connectivity, and adaptive diversity remain poorly resolved. This raises concerns about the ecological sustainability of current exploitation of wild populations and cleaner fish translocation practices between aquaculture facilities with the risk of escaping and introgression into wild populations.
This thesis provides the first integrated genomic and phenotypic assessment of wild Atlantic lumpfish population structure across both temporal (spawning season) and spatial axes in Norwegian waters. Using whole-genome sequencing of mature females sampled at several spawning grounds, combined with detailed analyses of sagittal otolith age, growth, and shape, this work investigates how spawning phenology, environmental heterogeneity, homing behavior, and genomic architecture interact to shape population divergence.
The results demonstrate that population structure in Atlantic lumpfish is complex and cannot be explained by geography alone. Strong and parallel divergence was detected between spring- and autumn-spawning individuals, driven primarily by adaptive differentiation concentrated in a specific region of the genome, consistent across distant spawning grounds. In contrast, spatial structuring among spring spawners was associated with chromosomal inversions and sex-linked genomic regions, revealing discrete genetic clusters along the Norwegian coast despite extensive offshore mixing in foraging areas. Otolith morphology mirrored both temporal and spatial genetic patterns.
Collectively, these findings reveal that Atlantic lumpfish comprise multiple temporally and spatially structured spawning components shaped by interacting ecological, behavioral, and genomic processes. This multidimensional structure has direct implications for fisheries management and aquaculture, since treating Atlantic lumpfish as a single homogeneous stock risks disproportionate depletion of vulnerable genetic groups, erosion of adaptive diversity, and genetic introgression from translocated broodstock.
By combining high-resolution genomics with otolith-based phenotypic analyses, this thesis provides a biologically informed framework for identifying management units and highlights the need for precautionary, structure-aware management of Atlantic lumpfish in Norwegian waters
Evaluation Committee
Supervisors
Streaming
Both the trial lecture and defense and will be streamed and recorded:
Thesis
The thesis is available in Vitenarkivet