the lowest adult density was recorded in this area since 1999 (with a reduction of
62 %). Juveniles (\16 cm) were almost completely absent from the survey area
from December 1994 until July 1999, after which there was a sudden increase,
with juvenile densities increasing by a factor of 20, reaching a peak value of
0.47 ind m
-2 in April 2001. This maximum density of juveniles implies settlement
sometime in early 1998, at the height of El Niño event (Hearn et al. 2005).
Following this peak, there was a steady decline, with densities as low as
0.20 ind m
-2 in the pre-fishery survey of 2003 (Hearn et al. 2005). The Bolívar
Channel has been recognized as a sea cucumber nursery ground and has remained
closed to fishing activities for the fishing seasons of 2003, 2004 and 2005 (ToralGranda 2005). Lawrence and Sonnenholzner (2004) reported densities of I. fuscus
in seven localities at the central region of Galápagos of between 0.02 ± 0.03 and
0.05 ± 0.04 ind m
-2 .
Growth and Reproduction
There is no knowledge of the recruitment dynamics or growth patterns of the
population of I. fuscus in Galápagos. Herrero-Pérezrul et al. (1999) and ReyesBonilla and Herrero-Pérezrul (2003) obtained preliminary population parameters
of I. fuscus from México, including estimations of asymptotic length
(L? = 32.613 cm) and growth coefficient (K = 0.2115 yr
-1 ). However, Hearn
et al. (2005) questioned if those growth parameters were applicable to Galápagos,
where individuals might reach 16 cm in length approximately 3.3 yr after settlement and the minimum landing size of 20 cm in length after 4.5–5 yr. Isostichopus
fuscus reproduces sexually and can spawn throughout the year. Complete information on its reproductive biology is limited for the whole archipelago. ToralGranda (1996) studied the reproduction of I. fuscus in a population at Caamaño
Island, Galápagos in 1995. Fifty percent of individuals were sexually mature at
23.6 cm and between 161.0 and 170.0 g dry weight. The smallest individual (less
than 16 cm) found with mature gonads had a dry weight between 121.0 and
130.9 g. Four reproductive peaks were found, two reproductive events in each cold
and warm water seasons, suggesting a continuous reproduction. The highest gonad
index (GI) value was found in December whilst the lowest was recorded in April
and September. Mean fecundity (eggs per gonad) for this species was
567,884 ± 95,528. Many animals were regenerating on June 2002 at the western
side of Galápagos at the Bolívar Channel (Sonnenholzner, personal observation).
These specimens were between 8 and 10 cm in length, and were without a mouth
or an anus, indicating an asexual reproduction episode by fission in this population.
Diet and Feeding Habits
Sonnenholzner and Cajas (1993) determined the most dominant food components
of I. fuscus collected early in the morning at Bolívar Channel at a depth of 12 m.
The gut contents contained a high percentage (50.3 %) of polyps of stony corals,
followed by benthic diatoms of the genus Melosira sp. (12.3 %), Grammatophora
6 Echinoderms of Ecuador
197
62 %). Juveniles (\16 cm) were almost completely absent from the survey area
from December 1994 until July 1999, after which there was a sudden increase,
with juvenile densities increasing by a factor of 20, reaching a peak value of
0.47 ind m
-2 in April 2001. This maximum density of juveniles implies settlement
sometime in early 1998, at the height of El Niño event (Hearn et al. 2005).
Following this peak, there was a steady decline, with densities as low as
0.20 ind m
-2 in the pre-fishery survey of 2003 (Hearn et al. 2005). The Bolívar
Channel has been recognized as a sea cucumber nursery ground and has remained
closed to fishing activities for the fishing seasons of 2003, 2004 and 2005 (ToralGranda 2005). Lawrence and Sonnenholzner (2004) reported densities of I. fuscus
in seven localities at the central region of Galápagos of between 0.02 ± 0.03 and
0.05 ± 0.04 ind m
-2 .
Growth and Reproduction
There is no knowledge of the recruitment dynamics or growth patterns of the
population of I. fuscus in Galápagos. Herrero-Pérezrul et al. (1999) and ReyesBonilla and Herrero-Pérezrul (2003) obtained preliminary population parameters
of I. fuscus from México, including estimations of asymptotic length
(L? = 32.613 cm) and growth coefficient (K = 0.2115 yr
-1 ). However, Hearn
et al. (2005) questioned if those growth parameters were applicable to Galápagos,
where individuals might reach 16 cm in length approximately 3.3 yr after settlement and the minimum landing size of 20 cm in length after 4.5–5 yr. Isostichopus
fuscus reproduces sexually and can spawn throughout the year. Complete information on its reproductive biology is limited for the whole archipelago. ToralGranda (1996) studied the reproduction of I. fuscus in a population at Caamaño
Island, Galápagos in 1995. Fifty percent of individuals were sexually mature at
23.6 cm and between 161.0 and 170.0 g dry weight. The smallest individual (less
than 16 cm) found with mature gonads had a dry weight between 121.0 and
130.9 g. Four reproductive peaks were found, two reproductive events in each cold
and warm water seasons, suggesting a continuous reproduction. The highest gonad
index (GI) value was found in December whilst the lowest was recorded in April
and September. Mean fecundity (eggs per gonad) for this species was
567,884 ± 95,528. Many animals were regenerating on June 2002 at the western
side of Galápagos at the Bolívar Channel (Sonnenholzner, personal observation).
These specimens were between 8 and 10 cm in length, and were without a mouth
or an anus, indicating an asexual reproduction episode by fission in this population.
Diet and Feeding Habits
Sonnenholzner and Cajas (1993) determined the most dominant food components
of I. fuscus collected early in the morning at Bolívar Channel at a depth of 12 m.
The gut contents contained a high percentage (50.3 %) of polyps of stony corals,
followed by benthic diatoms of the genus Melosira sp. (12.3 %), Grammatophora
6 Echinoderms of Ecuador
197