116
A. D. BONEY
marked variations of the population density of Ascophyllum with
substratum. Thus the plant density was much less on stony ground
than on rocky shores, and similar features governed its degree of
association with Fucus vesiculosus and F. serratus. The mean density
of the Ascophyllum plants was somewhat greater in the upper threefifths than in the lower two-fifths of its zone (Fig. 1). Whilst accurate
measurements of plant density are of great value, quick visual estimates by experienced surveyors are sometimes necessary. Grenager ( 1958)
described experimental surveys which were carried out in Norway to
expedite population surveys of Ascophyllurn and Laminaria on a much
indented region of the coast with numerous islands, inlets and skerries.
These surveys were based on experience gained on other shores, and on
a knowledge of the principal environmental characters of the shores to
be surveyed. In some test surveys the estimated and measured standing
crops were compared and were found to differ by relatively small
amounts. Thus with sufficient experience and a full knowledge of the
ecology of the shore reasonably accurate estimates of the standing
crops are possible.
2. Sublittoral surveys
Chapman (1944, 1950) described the combined use of echo-sounding
apparatus and aerial photography in measurements of the extent of the
sublittoral Laminaria forests. Use of specially designed grapnels in
accurately charted seas was also described. Walker (1950) obtained
quantitative data on plant density by the use of a spring-loaded grab
which sampled unit areas of the seabed ; these methods were combined
with accurate navigational measurements. Aerial photography waa
also used in these studies. The same methods have been applied by
other workers in this field, e.g. MacFarlane (1952a). In recent years
development of the self-contained breathing apparatus has enabled
direct measurements to be made of plant density and vertical distribution (Forster, 1955, 1958; Ernst, 1955, 1958). Kain (1962) has described how divers working in pairs can map the rocky sublittoral
profiles, and sublittoral studies on Macrocystis using similar techniques
have been described (Neushul, 1959; Neushul and Haxo, 1963). Given
suitable climatic conditions reasonably accurate assessments can be
made of undersea plant populations.
B. Summary of some data on standing crops obtained by direct
measurements
Much of the available data concerns the brown and red algae used for
their extractives and for seaweed meals. The more detailed surveys are
A. D. BONEY
marked variations of the population density of Ascophyllum with
substratum. Thus the plant density was much less on stony ground
than on rocky shores, and similar features governed its degree of
association with Fucus vesiculosus and F. serratus. The mean density
of the Ascophyllum plants was somewhat greater in the upper threefifths than in the lower two-fifths of its zone (Fig. 1). Whilst accurate
measurements of plant density are of great value, quick visual estimates by experienced surveyors are sometimes necessary. Grenager ( 1958)
described experimental surveys which were carried out in Norway to
expedite population surveys of Ascophyllurn and Laminaria on a much
indented region of the coast with numerous islands, inlets and skerries.
These surveys were based on experience gained on other shores, and on
a knowledge of the principal environmental characters of the shores to
be surveyed. In some test surveys the estimated and measured standing
crops were compared and were found to differ by relatively small
amounts. Thus with sufficient experience and a full knowledge of the
ecology of the shore reasonably accurate estimates of the standing
crops are possible.
2. Sublittoral surveys
Chapman (1944, 1950) described the combined use of echo-sounding
apparatus and aerial photography in measurements of the extent of the
sublittoral Laminaria forests. Use of specially designed grapnels in
accurately charted seas was also described. Walker (1950) obtained
quantitative data on plant density by the use of a spring-loaded grab
which sampled unit areas of the seabed ; these methods were combined
with accurate navigational measurements. Aerial photography waa
also used in these studies. The same methods have been applied by
other workers in this field, e.g. MacFarlane (1952a). In recent years
development of the self-contained breathing apparatus has enabled
direct measurements to be made of plant density and vertical distribution (Forster, 1955, 1958; Ernst, 1955, 1958). Kain (1962) has described how divers working in pairs can map the rocky sublittoral
profiles, and sublittoral studies on Macrocystis using similar techniques
have been described (Neushul, 1959; Neushul and Haxo, 1963). Given
suitable climatic conditions reasonably accurate assessments can be
made of undersea plant populations.
B. Summary of some data on standing crops obtained by direct
measurements
Much of the available data concerns the brown and red algae used for
their extractives and for seaweed meals. The more detailed surveys are