IMPACT OF HARVESTING ON FROND DENSITY AND BIOMASS OF IRISH MOSS (CHONDRUS-CRISPUS STACKHOUSE) BEDS IN THE SOUTHERN GULF OF ST-LAWRENCE

Dragrake harvesting had an adverse impact on frond density and biomass of Chondrus crispus Stackhouse as revealed by the comparison of these parameters in a dragraked bed (Miminegash) and a nondragraked bed (Rustico). Mean frond density peaked in September at both locations; it was significantly greater at Miminegash than at Rustico because of a higher density of small plants (Classes 1, 2, and 3). Intraannual variations in density were due to fluctuations of mostly the small plants (Classes 1 and 2). Mean frond biomass was significantly greater at Rustico than at Miminegash because of higher density and biomass of large Class 4 and 5 plants. Intraannual distribution of biomass was bimodal at Miminegash (June and September peaks) whereas it was unimodal at Rustico (peak in July). Mean frond density and biomass of reproductive plants were significantly greater at Rustico than at Miminegash. The study recommends a 1-mo delay in harvest season opening to enhance biomass yield. A longer postponement would not be beneficial, as populations will enter a period of natural decrease in density and biomass of C. crispus and of increased biomass of associated algae.