Environmental Variability & Mussel Stocks. Kati Michalek, SAMS

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1 Environmental Variability & Mussel Stocks Kati Michalek, SAMS ASSG AGM, Oban

2 Arctic Seas Dynamic Oceans Marine Renewables People & The Sea

3 Calcium in a Changing Environment - CACHE Shell Production for Shellfish Farming & Biotech in a Changing World Cultivation Environment Shellfish Production Population Genetics Calcification Shell Characteristics Biomimicry Applications Nov

4 Blue Mussel Cultivation in Scotland An inexpensive, sustainable shellfish that gives a boost to your immune system and brain The Guardian Record production 2016, supporting: Growth, employment, sustainable food production Fluctuating production due to: Inconsistent spat fall Appearance of non-marketable mussels Elevations in marine toxin levels more frequent Scottish Shellfish link to environmental cultivation conditions suggested

5 PhD Study Overview Environmental Monitoring Species Identification Product Marketability Shell Shape Shell Strength

6 Experimental Design Loch Leven 1m Mussel Rope Mussel Sampling (monthly) Mussel Analyses Product Quality 3m 5m Species Identity 7m Shell Traits

7 Water Monitoring Loch Leven Water Samples Food Chemistry Depth Profiles Temperature Salinity Data Logger Temperature Salinity Niskin bottle ~ 500 CastAway CTD 5000 CT Logger 600

8 Depth (m) Mussel Cultivation Environment Physical Temperature C Salinity 1 32 PSS

9 Depth (m) Mussel Cultivation Environment cont. Food Chlorophyll μg/l Carbon/Nitrogen

10 Meat Yield (%) (Flesh WW/(Flesh + Shell WW) Mussel Product Quality Food Supply / Growth Gametogenesis / Food Shortage glycogen & lipid reserves Spawning Meat Yield Meat Yield (%) is significantly higher in near-surface grown mussels influenced by environment and genotype (Beaumont et al. 2008)

11 Implications for Industry Environmental conditions differ with cultivation depth Surface waters very variable, deeper waters more stable conditions Better growth and product performance in surface waters (warmer waters, more food available) Influencing cultivation time, mortality, spat recruitment Mussel product quality is affected by both, depth as well as season Highest yields in surface grown mussels, harvested in Jun - Aug Mussel appearance differs with cultivation depth Surface-water mussels show greater variation in size and shell shape, while being less prone to fouling

12 Mussel Species ~ Appearance Environment ( Salinity) Species ( M. trossulus) Shell Strength ( weaker ) weaker mussels at cultivation sites ( exposure & predation pressure) in near-surface waters ( salinity) Associated with mussel identity, i.e. M. trossulus

13 Mussel Species Distribution mm rain/year (Metoffice) Michalek et al. (2016), Marine Genomics

14 Mussel Identity Single Marker Loch Spelve Loch Leven 1m 5m 10m 1m 3m 5m 7m

15 Mussel Population Genetics Single Marker 1 locus (e.g. Me 15/16) Species Identity ET EE TT TT EE ET Extent of Hybridisation Multiple Marker many loci (SNP assay)

16 Mytilus trossulus Introgression Depth 1m 3m 5m 7m Depth 1m 3m 5m 7m Proportion of Mytilus trossulus (%) 80 Mytilus trosslus (%) ID Mytilus trosslus (%) Shell Strength (kg per cm shell length) Strength (kg/cm SL) ID

17 M. trossulus reflected in shell characteristics? M. trossulus hybrids had significantly weaker shells Shell strength increased with depth weakest shells at 1m (~4kg) strongest at 7m (~32 kg); similar size but different species (M. trossulus vs M. edulis) Shell Strength

18 M. trossulus reflected in shell characteristics? cont. Image Shell Shape Outline 1m 7m Geometric Morphometric Analysis

19 Implications for Industry Shell characteristics are affected by a variety of factors Mussel strength & shape are different in surface waters Affected by environmental conditions, stocking density and species identity M. trossulus-like mussels have weaker shells Mussel population structure is affected by the environment M. trossulus occurrence and extent of M. trossulus gene introgression is higher in surface waters Surface water conditions are very variable, with frequent low salinity episodes

20 Executive Summary warmer water & more food = faster growth low shell fouling more mussels/area variable environment freshwater influence might favour less desired species weaker shells robust shells stable environment ensuring consistent growth desired species prevail slower growth longer cultivation time more shell fouling lower meat yields

21 Thank you for your attention!