by Mike Severns during a visit to the old pier on the property.
** Includes Gymnodoris sp. #7.
total of 167 species have been recorded from Hekili Point. Seven
added by sand samples extending from the beach to the outer slope (one
planktonic, four generally found at over 3 m, two typically found in
water). Three species were added by plankton tows. Nine species were
in the intertidal. Two species (Fiona pinnata &
Doto sp. #1) were found only on beached debris. So,
148 species were found in shallow benthic habitats (including the two
water ones from sand samples). Of those: 114 were found in algae
were found on day floats, 80 were found on night floats, 98 were found
combined visual searches, 49 were found only in algae washes, 21 were
only on night floats, 3 were found only on day floats and 32 were found
combined visual searches. The algae washes picked up 77% of the fauna,
floats 34%, the night floats 54% and the combined visual searches 66%.
Or, in other
words, 33% of the fauna would have been missed without algae washes,
have been missed without visual searches, 14% would have been missed
night floats, and 2% would have been missed without day floats.
material from sand samples added an additional 1%. Of the species that
noted during day floats, only 24 are usually seen crawling about or
the open by day. The other 27 are typically nocturnal species that were
largely by rock turning. So, only about 16% of the fauna would be
casual daytime snorkelers. And, that estimate is probably high since
the diurnal species are too small and cryptic to be easily seen in the
breakdown by species for the site is: 4 acteonoideans, 40
anaspideans, 41 sacoglossans, 1 tylodinoidean, 5 pleurobranchomorphans,
dorids (29 cryptobranch, 12 phanerobranch), 4 dendronotids and 19
breakdown by species for the shallow water benthic community is: 4
cephalaspideans, 8 anaspideans, 40 sacoglossans, 1 tylodinoidean, 3
pleurobranchomorphans, 34 dorids (22 cryptobranch, 12 phanerobranch), 3
dendronotids and 18 aeolids. One species, Stylocheilus striatus,
53% of the animals found in the algae washes with the second
species contributing only about 4%. However 30 species from the washes
of those found) were recorded from only one specimen. By number, the
of the algae washes is: Acteonoidea--0.0%, Cephalaspidea--19.9%,
Sacoglossa--18.4%, Pleurobranchomorpha--0.1%, Doridacea--3.1%,
Dendronotacea--0.1% and Aeolidacea--3.2%. So, the shallow benthic
community is dominated
by cephalaspideans and sacoglossans although anaspideans contribute the
greatest number of animals due to the prominence of S.
breakdown by species for the intertidal community is: 2 acteonoideans,
anaspideans, 4 sacoglossans, 3 pleurobranchomorphans, 22 dorids (20
cryptobranch, 2 phanerobranch), and 5 aeolids. By number, the
the intertidal community is: Acteonoidea--1.9%, Cephalaspidea--3.8%,
Sacoglossa--1.9%, Pleurobranchomorpha--1.1%, Doridacea--67.6%, and
Aeolidacea--2.3%. So, the intertidal community is dominated by dorids
terms of species and numbers.
sand samples yielded shells of about 35 species (with some uncertainty
due to condition). As mentioned, above, these include four benthic
typically found in water deeper than the 3 m boundary of significant
sampling as well as three planktonic species leaving 28 species from
benthic community. Two or them were collected only in the sand samples.
shells of 26 (or 45%) of the 58 live-collected species that have
external shells were also found in a moderately extensive series of
samples. More sampling would almost certainly increase that number but
the species that are nominally shell-bearing have very fragile shells
break up rapidly and are unlikely to be found. As would be expected,
dominated the sample.
What all this suggests is that (even
with very intensive
sampling) daytime and visual searches are insufficient for compiling a
complete or nearly complete survey of an opisthobranch fauna. Rather, a
methods need to be used, particularly sweeping surfaces for small and
species. So, a more rigorous application of the latter technique could
an important complement to more widely used methods in
studies and other surveys.