BIOLOGY OF SEAWEEDS O F ECONOMIC IMPORTANCE
211
the standing crop little changed. There are indications that controlled
harvesting of Macrocystis can be advantageous during the active
growth period.
Large quantities of certain sublittoral seaweeds, e.g. Chondrus and
Gracilaria, are successfully harvested from shallow-draught boats
using long-handled rakes with tines set at a sharp angle. Long poles
with hooks are used in Japan to collect the konibu blades. These tend
to detach the holdfast as well, so that regenerative growth is not
readily observed. These methods pick up large quantities of seaweed in
the North American seas, and in the instance of Chondrus remove
sufficient quantities of the frondage without injury to the attaching
systems (p. 193). Long-handled cutting knives have been used for
harvesting Macrocystis fronds in Tasmania (Cribb, 1954), and longhandled rakes with Undaria plants in Japan.
Some harvests depend on cast weeds, e.g. Chondrus on Prince
Edward Island (MacFarlane, 1964a), and Pterocladia on the North
Island in New Zealand (Newton, 1963), in which cases a fairly rapid
collection is necessary before the seaweed is damaged by exposure to air.
Many of the seaweeds are still harvested by hand, and this would
still appear to be the most economic mode of collecting. The collecting
may be carried out under the sea by means of divers, whilst handpicking of fronds of plants growing on the shore has been found to be
advantageous in allowing regrowth of new frondage. Gelidium sp. and
Pterocladia sp. are harvested in this way. Porphyra plants are handpicked from the " hibi '' in Japan, and this has the advantage of ensuring that mainly the fully-grown thalli are collected. Pickings of the
cultivated plants can be made three or four times between November
and March. In the British Isles the Porphyra plants used as sources of
laver are collected directly from their shore habitats, and in some cases
the collectors are known to " farm '' the regions of shore from which
they harvest the Porphyra (Hampson, 1957). The quantity of any
material harvested will depend on the initial spore attachment. It is
important to know the relationship between the quantity of spores
released and the hydrographical and meteorological conditions which
occur at the time. Suto (1952) suggested that if quantitative estimates
can be made of the spore output of a particular plant and when the
maximum release is observed in the sea, then announcements made over
the radio from local research stations could indicate to fishermen the
best times to obtain dense spore settlements on suitable surfaces.
The large-scale exploitation of seaweeds requires adequate processes
of drying, since there will be deterioration of the harvested material
if this is not expeditiously carried out. Studies specifically concerned
211
the standing crop little changed. There are indications that controlled
harvesting of Macrocystis can be advantageous during the active
growth period.
Large quantities of certain sublittoral seaweeds, e.g. Chondrus and
Gracilaria, are successfully harvested from shallow-draught boats
using long-handled rakes with tines set at a sharp angle. Long poles
with hooks are used in Japan to collect the konibu blades. These tend
to detach the holdfast as well, so that regenerative growth is not
readily observed. These methods pick up large quantities of seaweed in
the North American seas, and in the instance of Chondrus remove
sufficient quantities of the frondage without injury to the attaching
systems (p. 193). Long-handled cutting knives have been used for
harvesting Macrocystis fronds in Tasmania (Cribb, 1954), and longhandled rakes with Undaria plants in Japan.
Some harvests depend on cast weeds, e.g. Chondrus on Prince
Edward Island (MacFarlane, 1964a), and Pterocladia on the North
Island in New Zealand (Newton, 1963), in which cases a fairly rapid
collection is necessary before the seaweed is damaged by exposure to air.
Many of the seaweeds are still harvested by hand, and this would
still appear to be the most economic mode of collecting. The collecting
may be carried out under the sea by means of divers, whilst handpicking of fronds of plants growing on the shore has been found to be
advantageous in allowing regrowth of new frondage. Gelidium sp. and
Pterocladia sp. are harvested in this way. Porphyra plants are handpicked from the " hibi '' in Japan, and this has the advantage of ensuring that mainly the fully-grown thalli are collected. Pickings of the
cultivated plants can be made three or four times between November
and March. In the British Isles the Porphyra plants used as sources of
laver are collected directly from their shore habitats, and in some cases
the collectors are known to " farm '' the regions of shore from which
they harvest the Porphyra (Hampson, 1957). The quantity of any
material harvested will depend on the initial spore attachment. It is
important to know the relationship between the quantity of spores
released and the hydrographical and meteorological conditions which
occur at the time. Suto (1952) suggested that if quantitative estimates
can be made of the spore output of a particular plant and when the
maximum release is observed in the sea, then announcements made over
the radio from local research stations could indicate to fishermen the
best times to obtain dense spore settlements on suitable surfaces.
The large-scale exploitation of seaweeds requires adequate processes
of drying, since there will be deterioration of the harvested material
if this is not expeditiously carried out. Studies specifically concerned