Biofouling on Greenshell™ mussel (Perna canaliculus) farms: a preliminary assessment and potential implications for sustainable aquaculture practices

Abstract

Greenshell TM mussel (Perna canaliculus) culture is the primary aquaculture industry in New Zealand. However, our knowledge of biofouling on Greenshell TM mussel farms, and its contribution to farm ecotrophic effects, is poor. We conducted a preliminary study of biofouling accumulation at two Greenshell TM mussel farms during Intermediate and Final seed on-growing stages (each of 6 months duration) with sampling of mussel ropes at 0, 3, 5 and 6 months during each on-growing stage. A diverse range of biofouling organisms (71 distinct taxa) accumulated on mussel ropes, with biofouling biomass dominated by suspension-feeding organisms (*88% of biofouling biomass) such as other bivalves, ascidians and, to a lesser degree, bryozoans. Biofouling biomass increased with culture time, varied between farms and was generally greater at 2 m than at 8 m depth. After 6 months, biofouling organisms on average comprised 54% of the total rope biomass. The reseeding of ropes between Intermediate and Final seed crops reduced the amount of non-Greenshell TM mussel biofouling. However, after 6 months, non-Greenshell TM mussel biofouling on average still comprised 15% of the total rope biomass. To evaluate potential ecotrophic effects of biofouling on Greenshell TM mussel farms, we compare the clearance rates of Greenshell TM mussel longlines based on Greenshell TM mussels alone and when combined with the two dominant biofouling species observed in our study (the mussel Mytilus galloprovincialis and the ascidian Ciona intestinalis). Our study shows that accumulated biofouling biomass on Greenshell TM mussel ropes can be significant and recommends further investigation as to actual ecotrophic effects of biofouling to ensure sustainable mussel farm practices.

Characterising biofouling communities on mussel farms along an environmental gradient: a step towards improved risk management

“…1). It is a 56 km long, relatively deep (average water depth 40 m) and highly indented estuarine system with variable freshwater input from the Kaituna and Pelorus rivers entering at the head of the Sound, as well as oceanic exchange from upwelling waters in Cook Strait (Heath 1974, Woods et al 2012). There are complex tidal, estuarine and wind-driven circulation systems in the Pelorus, with mean residence times varying from 21 d in Pelorus channel to 6 d in the Kenepuru.…”

“…The occurrence and impacts of specific biofouling species on marine farm structures varies spatially (Cecche relli & Campo 2002, Thomsen et al 2006) and temporally (Staehr et al 2000, Forrest & Taylor 2002, including variation in community structure among years (Underwood & Anderson 1994), locations (Lutz-Collins et al 2009, Sievers et al 2014) and depths (Hanson & Bell 1976, Woods et al 2012). For example, Woods et al (2012) and Cronin et al (1999) found reduced biofouling biomass and less diversity in biofouling communities with increased depth on marine farm structures (mussel long-lines and tuna sea cages).…”

“…For example, Woods et al (2012) and Cronin et al (1999) found reduced biofouling biomass and less diversity in biofouling communities with increased depth on marine farm structures (mussel long-lines and tuna sea cages). Some biofouling populations also proliferate rapidly and then gradually retreat.…”

“…In New Zealand, Pelorus Sound (located in the Marlborough Sounds) is the major growing region for the mussel farming industry, with approximately 645 farms spread across 5000 ha of farming area (Woods et al 2012). Despite the value and extent of this area, aside from a few site-specific studies (Woods et al 2012), our knowledge about the spatial and temporal variation of biofouling organisms associated with these aquaculture farms is limited.…”

“…Despite the value and extent of this area, aside from a few site-specific studies (Woods et al 2012), our knowledge about the spatial and temporal variation of biofouling organisms associated with these aquaculture farms is limited. Hence, this study had 3 specific objectives: (1) to characterise biofouling on mussel farm long-lines in Pelorus Sound, with the expectation that community structure and the relative abundance of pest species would vary across the study region; (2) to investigate the influence of depth on biofouling community structure and species relative abundance, with the expectation that biofouling cover would decrease with increasing depth; and (3) to assess potential mechanisms contributing to biofouling structure by investigating the relationship between biofouling community similarity and distance between marine farms, with the expectation that community similarity would decrease as geographical distance between farms increased.…”