jacks, mackerels, large parrotfishes, etc.). Minutes 2-5 - the diver swam over the center of
the transect to identify and enumerate opportunistic fishes that tend to be attracted to
transect areas, presumably to feed upon mechanical disturbances created by the diver (e.g.
wrasses, groupers, hamlets, caribbean puffer). Minutes 6-10 - the diver swam over each
side of the transect to identify and count fishes that are either territorial (e.g. damselfishes)
or that remain very close to their benthic microhabitat, without any evident concern of diver
presence (gobies, grammas, squirelfishes, small parrotfishes, etc.). Minutes 10-12 – the
diver swam over each side of the transect to search for fish species present in relatively low
abundance (rare) and/or that may be either entering or exiting small reef microhabitats (e.g.
cherubfish, basses). Minutes 13-15 the diver swam over each side of the transect to identify
and enumerate non-criptic motile, megabenthic invertebrates present within belt-transect
areas (e.g. cephalopods, gastropods, ophiuroids, urchins, holothurians, crabs, lobsters,
shrimps, etc.). Fish surveys were performed during the summer of 2004 (June-August) at
the 30 and 40 m depths in the SW Wall Reef, and during the summer of 2005 (June-August)
at 50 m depth in Agelas Reef. A winter (January-March) survey was performed at the 30
and 40 m depths in the SW Wall Reef.
Large, elusive fish populations, which includes most of the commercially important and
many recreationally valuable populations were evaluated using an Active Search Census
(ASEC). This is a non-random, fixed-time method designed to optimize information of the
numbers of fish individuals present at the main reef habitats, providing simultaneous
information on size frequencies. At each depth (30, 40, 50 meters) the total number of
individuals for each species observed within a fixed time frame of 30 min. was registered.
Individuals were actively searched for within crevices, ledges and potentially important
hiding places. For each individual sighted, a length estimate was recorded. Length (in cms)
was visually estimated and aided by a measuring rod with adjustable width. Precision of
length estimates allowed discrimination between small juveniles, juveniles, adult and large
adult size classes. Two ASEC surveys were performed at 30 and 40 m depths, and one
ASEC survey was performed at 50 m. All data was recorded in plastic paper.
Closed circuit Inspiration Rebreather units were used to conduct underwater survey
operations at Isla Desecheo. We used mostly oxygen partial pressures of 1.3 ATA to survey
depths between 30 – 50 m, with maximum decompression times of 30 minutes.
14
the transect to identify and enumerate opportunistic fishes that tend to be attracted to
transect areas, presumably to feed upon mechanical disturbances created by the diver (e.g.
wrasses, groupers, hamlets, caribbean puffer). Minutes 6-10 - the diver swam over each
side of the transect to identify and count fishes that are either territorial (e.g. damselfishes)
or that remain very close to their benthic microhabitat, without any evident concern of diver
presence (gobies, grammas, squirelfishes, small parrotfishes, etc.). Minutes 10-12 – the
diver swam over each side of the transect to search for fish species present in relatively low
abundance (rare) and/or that may be either entering or exiting small reef microhabitats (e.g.
cherubfish, basses). Minutes 13-15 the diver swam over each side of the transect to identify
and enumerate non-criptic motile, megabenthic invertebrates present within belt-transect
areas (e.g. cephalopods, gastropods, ophiuroids, urchins, holothurians, crabs, lobsters,
shrimps, etc.). Fish surveys were performed during the summer of 2004 (June-August) at
the 30 and 40 m depths in the SW Wall Reef, and during the summer of 2005 (June-August)
at 50 m depth in Agelas Reef. A winter (January-March) survey was performed at the 30
and 40 m depths in the SW Wall Reef.
Large, elusive fish populations, which includes most of the commercially important and
many recreationally valuable populations were evaluated using an Active Search Census
(ASEC). This is a non-random, fixed-time method designed to optimize information of the
numbers of fish individuals present at the main reef habitats, providing simultaneous
information on size frequencies. At each depth (30, 40, 50 meters) the total number of
individuals for each species observed within a fixed time frame of 30 min. was registered.
Individuals were actively searched for within crevices, ledges and potentially important
hiding places. For each individual sighted, a length estimate was recorded. Length (in cms)
was visually estimated and aided by a measuring rod with adjustable width. Precision of
length estimates allowed discrimination between small juveniles, juveniles, adult and large
adult size classes. Two ASEC surveys were performed at 30 and 40 m depths, and one
ASEC survey was performed at 50 m. All data was recorded in plastic paper.
Closed circuit Inspiration Rebreather units were used to conduct underwater survey
operations at Isla Desecheo. We used mostly oxygen partial pressures of 1.3 ATA to survey
depths between 30 – 50 m, with maximum decompression times of 30 minutes.
14