Co-culture of dulse Palmaria mollis and red abalone Haliotis rufescens under limited flow conditions

Abstract

A series of experiments was conducted to determine factors limiting the stocking density and growth rates of red abalone in a co-culture system with the macroalgae dulse ( Palmaria mollis). Co-culture conditions were altered by varying the degree of artificial illumination (0 h, 12 h at night, and 24 h d −1 in addition to ambient sunlight) used to supplement ambient sunlight and water volume exchange rate (1, 6, or 35 d −1). Rates of dulse production, dulse consumption by abalone, ammonia uptake by dulse and ammonia excretion by abalone were measured seasonally over 1 year. Abalone growth rates under co-culture conditions were measured. Maximum abalone stocking densities within the co-culture system were first limited by the amount of algae available for abalone consumption, and then by the capacity of the algae to absorb ammonia excreted by abalone. Degree of supplemental illumination, water volume exchange rate, and abalone body weight all affected maximum stocking densities within the co-culture system. The growth rates of abalone fed dulse grown under all co-culture conditions (range: 112–132 μm shell length d −1) compared favorably with that of abalone fed on other algal and artificial diets. Both duration of supplemental illumination and water volume exchange rate affected abalone growth. Overall, the co-culture of dulse and abalone provides the farmer with a reliable supply of nutritious abalone food while ensuring high water quality through uptake of excreted ammonia by the dulse.