Hierarchical structure of bivalve culture systems and optimal stocking density

Abstract

Bivalve culture systems are hierarchical, with culture units being nested within culture gear, which are nested within farms, and so on. The possibility that processes acting at the scale of individual culture units may interact with high-level processes has been overlooked in carrying capacity models, although basin-scale patterns are generated at the scale of culture units. Here I study the effect of increasing basin-scale loading on unit-scale optimal stocking density (OSD). I find a curvilinear relationship, with OSD decreasing with basin-scale loading. Clearly basin-scale models should incorporate culture-unit effects. This may be achieved by using experimental studies of the clearance rate of whole culture units to complement estimates of ecophysiological processes of individuals. Such culture-unit information, along with knowledge of associated local phytoplankton depletion at various current speeds and culture-unit stocking levels, may be used to generate submodels to be included in basin-scale models. To facilitate experimental testing of across-scale effects, I develop a simple food-regulated growth model combining density dependence at the scale of individual culture units and at the scale of basins. Keywords Bivalve culture Á Carrying capacity Á Hierarchy Á Mussel Á Stocking density Abbreviations OSD Culture unit optimal stocking density BN curve Biomass-density curve N * model Body size-density model with hierarchical effect of number of culture units only mN model Body size-density model mNN * model Body size-density model with hierarchical effect of body size, culture unit population density and number of culture units combined M. Fréchette (

Evaluating chlorophyll depletion in mitigation mussel cultivation at multiple scales

“…At the basin scale, there have been efforts to characterize bivalve culture depletion impacts on phytoplankton abundance with airborne spectral remote sensing (Grant et al 2007) and satellite remote sensing (Gernez et al 2017). Coupling analytical scales as performed in this study with basin-scale analysis could enhance precision in estimates of depletion, as well as help resolve competing effects, such as wind-driven advection, baroclinic advection, or vertical dispersion further afield (Fréchette 2010).…”

Influence of suspended and off-bottom mussel culture on the sea bottom and benthic habitats: a review1This review is part of a virtual symposium on current topics in aquaculture of marine fish and shellfish.

“…Suspended mussel culture is known to influence and be influenced by hydrodynamic circulation at a wide range of spatial scales. Mussel culture systems present a porous barrier and are hierarchical, with individual bivalves and their associated fouling organisms nested within culture units (e.g., socks,), these being nested within culture gear (longlines or rafts), which are nested within farms, and so on (Plew et al 2005;Stevens et al 2008;Fréchette 2010). An understanding of processes operating at each scale, as well as the relations between these scales, is needed to predict how hydrodynamics influence the settlement and recruitment of organisms within culture systems and to understand cascading effects on the ecosystem.…”

“…In all cases, biodeposit production was measured for a single or low numbers of mussels and not by complete mussel socks. It is likely that mussels in a mussel sock function differently from the sum of a series of individual mussels as the interactions between mussels and the environment are scale-dependent (Smith et al 2006;Stevens et al 2008;Fréchette 2010). Although recent work (McKindsey et al 2009) has addressed these issues by measuring biodeposit production by small mussel socks suspended over large sediment traps, only a single size class of mussels was evaluated in one site at one time of the year.…”

Dynamics of phytoplankton community in scallop farming waters of the Bohai Sea and North Yellow Sea in China

“…A shift in phytoplankton dominance from diatoms to dinoflagellates was observed in shellfish farming waters of the Zhangzi Island, which was attributed to the phosphate and silicate limitations [ 22 ]. Moreover, the filter feeding of bivalves such as scallops, oysters and mussels, also has a considerable top-down control on the phytoplankton biomass [ 10 , 22 ]. Their selective feeding on certain algae species would further enhance the phytoplankton succession, making the phytoplankton dynamics more complex in the farming waters [ 9 , 22 ].…”