regrowth from unharvested subsurface 

 fronds on cut plants. In areas where 

 Nereocystis "luetkeana and Macrocystis 

 co-occur, the amount of _N. luetkeana 

 harvested is restricted by law. Nereocys - 

 tis luetkeana is an annual, and its 

 reproductive blades occur near the 

 surface. Harvesting too much Nereocystis 

 could inhibit its re-establishment. 



Between 100,000 and 170,000 wet tons 

 of Macrocystis &re currently harvested 

 annually in California (Frey 1971, 

 Oliphant 1979), and sales by the kelp 

 harvesting industry exceed $35 million a 

 year (Wilson and McPeak 1983). Forests 

 are also harvested in Mexico with plants 

 imported to Kelco Company in San Diego. 

 The majority of the California harvest 

 normally comes from the large forests in 

 southern California (Barilotti pers. 

 comm.), but harvesting occurs as far north 

 as Carmel Bay in central California. 

 Particular stands in southern California 

 may be harvested up to three times per 

 year (see McPeak and Glantz 1984 for a 

 review of kelp harvesting and uses). 



Kelp harvesting has a variety of 

 possible impacts on giant kelp, kelp 

 forests, and associated nearshore 

 communities. Concern over these impacts 

 has been a major stimulus for kelp forest 

 studies since the late 1950's. The 

 primary concerns have been the possible 

 destruction of kelp stands, destruction of 

 canopy-dwelling invertebrates and fishes 

 during harvesting operations, reduction in 

 fish populations due to loss of food 

 and/or habitat, and an increase in beach 

 erosion and amount of drift kelp on 

 beaches. Early studies of these potential 

 problems were summarized by North and 

 Hubbs (1968), who concluded that "No 

 adverse influence of harvesting could be 

 found among the statistics or field 

 observations for the periods studied." 

 Uncut fronds grow to replace those cut, 

 and it appears that only occasionally is 

 an entire plant torn from the bottom 

 during harvesting operations (Rosenthal et 

 al . 1974). Harvesting the canopy 

 increases light on the bottom, and may 

 enhance recruitment of Macrocystis 

 (Rosenthal et al. 1974, Kimura and Foster 

 in press). Miller and Geibel (1973) found 

 that adult Macrocystis abundance declined 

 after repeated experimental canopy removal 



at Point Cabrillo near Monterey. Kimura 

 and Foster (in press) found no adverse 

 affects after a single experimental har- 

 vest in Carmel Bay. The latter study more 

 closely resembled commercial harvesting as 

 currently practiced in Carmel Bay, and 

 suggests that Miller and Geibel 's (1973) 

 results represent what may happen in 

 central California if an area is over- 

 harvested. Kimura and Foster (in press) 

 did find that the timing of recruitment in 

 kelps ( Macrocystis and Pterygophora 

 cal ifornica ) changed in harvested areas, 

 but this change had no apparent negative 

 effects. Barilotti et al. (in press) 

 found that survivorship of adults was not 

 reduced in the two harvested forests they 

 studied. 



No overall reduction in fishes or 

 invertebrates in particular forests has 

 been reported due to harvesting opera- 

 tions, even though numerous organisms are 

 removed along with the cut fronds (North 

 and Hubbs 1968, Miller and Geibel 1973). 

 Hunt (1977) did find significant declines 

 in turban snail ( Tegula montereyi ) densi- 

 ties in harvested areas in Carmel Bay. 

 Sea otters avoid kelp harvesting ships, 

 and no mortality related to kelp harvest- 

 ing operations has been reported for this 

 or other mammals. 



Clendenning (1971b) estimated that 

 10% or less of Macrocystis production is 

 removed by harvesters in harvested for- 

 ests. Possible changes in consumer popu- 

 lations in kelp forests or elsewhere 

 (beach, offshore) that may be an indirect 

 result of removing this primary production 

 have not been investigated. 



Recent research on growing Macro - 

 cystis for fuel is discussed in Section 

 6.6.2. Macrocystis has also recently been 

 introduced in the People's Republic of 

 China to possibly replace Laminaria as a 

 source of food and algin (Foster pers. 

 obs.). 



6.2.1.2 Other plants . The only 

 other plant commercially harvested from 

 California kelp forests is Gel idium 

 robustum , a source of high-quality agar 

 (Figure 17). This plant is occasionally 

 harvested by divers when prices are high 

 (Frey 1971). The plant is very suscep- 

 tible to overharvesting, as it grows 



110 



