Comparing traditional vs. biodegradable seed mussel collectors (SMCs) for seed settlement, seed density, and seed growth: Effect of deployment depth and location

Mussel bottom culture is historically based on transplanting wild mussel seed to designated culture plots. Seed mussel collectors (SMCs) that are deployed in the water column are gradually replacing benthic mussel beds for mussel seed resource provisioning. Traditional SMCs consist of weighted filamentous nylon ropes. The performance of SMCs are promising, but the major disadvantages are the increased cost, effort, and the use of non-sustainable materials. In this study, we developed an innovative SMC: the BioShell-SMC. It consists of a coconut core rope surrounded by empty cockle shells that are held in place by biodegradable socking. The advantage of this system compared to traditional SMCs is that it provides biodegradable and sustainable resource material suitable for on-bottom placement. We compared its relative performance to that of a traditional SMC at different deployment depths and locations used for SMC deployment in the Dutch Wadden Sea and Oosterschelde. The results from this experiment indicated that in six out of nine locations mussel seed biomass was comparable between the two collector types. On both collector types, mussel seed biomass was higher in the Wadden Sea than in the Oosterschelde. We also found that mussel seed biomass development was not affected by deployment depth, though mussels were more numerous and shorter in deep water. The results of the current study provide a promising start toward a more sustainable mussel seed collection for bottom cultivation.