Abstract
As the emerging temperate kelp industry seeks to scale in the west, established seeding methodologies, principally twine anddirect seeding, present persistent bottlenecks in hatchery costs, space requirements, and operational reliability. This studyevaluates splice seeding, a precision-spacing technique common in East Asian kelp aquaculture, as an alternative approachfor Saccharina latissima cultivation. Seeded twine was cut into 3 cm sections and manually inserted into 12 mm twistedcultivation ropes at 5, 10, and 20 cm intervals; conventional twine-wrapping served as the control. Sea trials in centralNorway (November 2024 – June 2025) demonstrated a stepwise decline in absolute biomass yield with increasing spliceinterval: 2.9, 2.4, and 1.8 kg m⁻1, compared to 3.8 kg m⁻1 for conventional twine. However, evaluated as biomass per meterof seeded twine (a metric we term "seeding substrate efficiency") splice seeding yielded 4.7, 8.0, and 12.0 kg m⁻1 comparedto 3.5 kg m⁻1 for the control, representing material efficiency gains of 36–248%. The density of large sporophytes (> 40 cm)was the primary driver of total yield (Pearson's r = 0.80, p < 0.001), and their lower absolute numbers in splice treatmentsexplains the observed yield gap. Increasing large sporophyte density within splice sections through earlier deployment, higherinitial seeding densities, or improved substrates represents the most direct pathway to yield parity and would enable spliceseeding to deliver its full economic and operational advantages for Western kelp aquaculture.