Enhanced production of Pacific dulse ( Palmaria mollis) for co-culture with abalone in a land-based system: effects of stocking density, light, salinity, and temperature

Abstract

Palmaria mollis or Pacific dulse is used as both a biofilter and feed in temperate, land-based marine aquaculture of abalone and finfish. Land-based tumble-culture techniques capable of producing commercial quantities of P. mollis are still in development. In this study the effects of stocking density, light, salinity, and temperature on growth rates and yields of P. mollis were examined. Under a natural photon flux density (PFD) of 39–52 mol photons m −2 day −1 an aerial stocking density of 3–4 kg m −2 provided highest yields. Specific growth rates of P. mollis were highly correlated with specific light densities (SLD) over a range from 0.0048 to 0.036 mol photons g −1 [fresh wt.] day −1 and no light saturation was evident at a culture temperature of 16±1 °C. Growth of P. mollis was highest at a salinity of 30±1‰, whether municipal tap water or brackish well water was used for diluting seawater. Optimal temperature for growth was 12 °C at low light intensities (SLD=0.010 mol photons g −1 day −1) and 14–18 °C at high light intensities (SLD=0.021 mol photons g −1 day −1). Growth at higher temperatures was positively correlated with increasing light. Lowering culture temperature at night from 15 to 11 °C significantly increased growth for cultures that were not supplied with supplemental inorganic carbon.