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Topic

Influence of hatchery protocols on Yesso scallop larval survival, growth, and microbiome

Department of Biology

Date & location

• Tuesday, July 29, 2025
• 10:00 A.M.
• Clearihue Building, Room B021

Examining Committee

Supervisory Committee

• Dr. Steve Perlman, Department of Biology, ßÉßɱ¬ÁÏ (Supervisor)
• Dr. John Taylor, Department of Biology, UVic (Member)
• Dr. Timothy Green, Centre for Shellfish Research, Vancouver Island University (Outside Member)

External Examiner

• Dr. Timothy Bowden, School of Food and Agriculture, University of Maine

Chair of Oral Examination

• Dr. Dante Canil, School of Earth and Ocean Sciences, UVic

Abstract

Scallop farming creates jobs in remote coastal communities and is a sustainable avenue for improving food security. Yesso scallop (Mizuhopecten yessoensis) is an economically important cultivated scallop species due to its fast growth rate, large adductor muscle size, and high market value. Access to seed (juvenile scallops) limits aquaculture production due to frequent and unexplained mass larval mortality events linked to bacterial disease outbreaks. Suboptimal larval rearing conditions may cause unstable microbial communities in culture tanks and favor the proliferation of pathogenic bacteria. Many factors may contribute to mortality, as larval cultures are complex systems and scallops are highly sensitive to environmental fluctuations. This thesis evaluates the effects of tank cleaning frequency, temperature, photoperiod, diet, and probiotic bacterial exposure on the growth, survival, and microbiome of scallop larvae. Growth and survival were measured throughout the larval stage, from D-stage to pediveliger. Microbiome was characterized by 16S rRNA sequencing at several time points to assess the succession of microbial communities throughout development. Morphological development and health status of larvae were evaluated using microscopy and a scoring chart of the most common larval conditions observed. Results demonstrate that the husbandry practices tested did not determine larval survival, and thus genetic pedigree of broodstock or gamete quality (broodstock conditioning) may be a key factor. However, larval growth was increased with 15°C seawater (compared to 12°C), and with a 12L:12D (Light:Dark) photoperiod (compared to 0L:24D) in combination with a microalgae diet with higher proportions of flagellate species relative to diatom species. Knowledge from this project will inform the scallop industry toward improvement of hatchery rearing methods.