Relation of mussel spatfall on natural and artificial substrates: Analysis of ecological implications ensuring long-term success and sustainability for mussel farming

Abstract

The characteristic that enables mussels to settle on filamentous type substrates is exploited to supply seeds for mussel farming via spatfall on ropes. This produces a strong socio-economic impact, as it allows independent and micro-producers to participate directly in an activity that produces >3milliontonnes annually worldwide. Despite the importance of this ecosystem service, there is no record of an association between the dynamics of natural beds and spatfall on ropes in literature published to date. This paper presents the case of Mytilus chilensis a species that dominates the inter-tidal and shallow sub-tidal communities in estuaries on the Chilean coast and part of the Argentine coast. Cultivation of this species in Chile produces about 240,000tonnes annually. Our aim is to study the dynamics of natural M. chilensis beds in Reloncaví fjord, one of the most important areas for mussel spatfalls in Chile, and investigate their relationship with spatfall on collectors (ropes) installed by local producers. Veliger competent larvae were present in relative abundance during most of the breeding season, which was reflected in a high spatfall on ropes. However, this larval abundance resulted in low recruitment into the natural beds, suggesting a mismatch between larval supply and recruitment. Oversupply of artificial substrate can promote recruitment failures in natural beds, which can be a threat to the mussel farming industry. There is a risk that the search for a possible alternative to natural seed supply (e.g. seed production in the laboratory) to satisfy mussel farming requirements, may come into conflict with the principles of the Ecosystem Approach to Aquaculture; thus, management measures should be implemented, in order to ensure the long-term sustainability of this activity.