The effects of ambient and aquaculture structure hydrodynamics on the food supply and demand of mussel rafts.

摘要

A field and modeling study of the food supply and demand of mussel (Mytilus edulis) rafts in Maine established the hydrodynamic and particle consumption characteristics of shellfish aquaculture structures. Mussels on rafts filtered about 8x106 L/h and consumed about 40 g chlorophyll a (chl a)/h under favorable conditions. Because of the drag of the culture ropes and predator nets, velocity inside the rafts was reduced by 75%-80% in relation to ambient conditions. Chlorophyll consumption by mussels increased with increased food (chl a) concentration and also with increased water velocity inside the rafts. Clearance rates per raft also increased with food concentration. Model results allow for an estimation of water flux and seston depletion within the rafts through the use of point measurements and correction factors. Water velocity measurements taken mid depth in the middle of the rafts underestimated the mean flow through the raft by 10%. Measurements of current velocity and chl a concentration taken mid depth in the middle of the rafts underestimated the mean particle consumption rates by 13%. Model results and field data indicate that mussel raft hydrodynamics are a function of raft orientation to current direction, mussel raft size, raft aspect ratio, the presence of predator nets, the presence of multiple rafts, rope spacing, and rope diameter. Mussel raft design, placement, and biomass may be adjusted to optimize hydrodynamics and conditions favorable for improved mussel growth rates. Recommended flow speeds through experimental mussel rafts with a cross-sectional area of 121 m2 require a minimum outside flow speed of 14-23 cm/sec.