Regeneration and reproduction of Mazzaella cornucopiae (Rhodophyta, Gigartinaceae) after frond harvesting

The effects that different intensities of frond harvesting have on frond re generation and subsequent production of reproductive structures were invest igated for the red intertidal alga Mazzaella comucopiae (Postels & Ruprecht ) Hommersand from British Columbia, Canada. Harvesting was done by pruning fronds in the late spring (when stand biomass is highest) of 1993 at two in tensities: total and partial collection of fronds, in this second case leav ing all frond biomass less than 1 cm high in place. Holdfasts were not dama ged. Total percent cover of thalli, frond density, mean frond length, and s tand biomass for these experimental quadrats were statistically similar to values for control quadrats in the spring of 1994. These results suggest th at one total harvest of fronds per year, done in late spring without damagi ng holdfasts, may give the highest sustainable yield of biomass. The effect s of harvesting intensity on reproduction were variable and difficult to ex plain. Neither the appearance nor the abundance of cystocarpic fronds were affected by frond pruning, compared with control areas, but pruning did aff ect the appearance and the abundance of tetrasporic fronds. Partial pruning resulted in a longer presence of tetrasporic fronds, whereas total pruning was associated with their complete absence. Results are compared with thos e for the few other species of the Gigartinaceae for which experimental har vesting has been done.