2.3.2 Population Ecology Studies
Few population ecology studies focused on particular species of echinoderms have
been carried out in Mexico. This is regrettable, especially in the case of echinoids
and holothurians, considering their importance as key organisms in the structure
and dynamics of benthic communities, and their potential for commercial
exploitation. Important species include the sea urchin D. mexicanum and the sea
cucumbers Isostichopus fuscus and Parastichopus parvimensis.
Echinoids
Espino-Barr et al. (1996) analyzed the density and population structure of
D. mexicanum on the rocky shore of the state of Colima in the Mexican Pacific as
part of a technical assessment for requests of permission for sea urchin fishing
along Colima and Jalisco shores. The results indicated an average density of
17,000 ind ha
-1 . There was an increase in gonad weight with respect to body
weight from May to August, followed by a decrease, indicating spawning during
those months. They propose the commercial exploitation of the species between
May and September when the gonads reach the greatest weight. Nevertheless they
proposed it be restricted to protect the species.
Herrera-Escalante et al. (2005) evaluated the importance of D. mexicanum as a
bioerosive agent of coral carbonate at Bahias de Huatulco and the relative magnitude
of coral accretion and bioerosion. The results showed that, in general, D. mexicanum
did not exert a significant role on coral reef community structure at the study area,
probably because of their relatively small size and low numbers. Regarding the
balance between bioerosion and carbonate production, they established that coral
accretion exceeded sea urchin erosion at all sites examined, indicating that at Bahias
de Huatulco coral reef communities were actively growing.
Benitez-Villalobos et al. (2008) evaluated the temporal variation of population
densities and bioerosion by D. mexicanum at Isla Montosa, La Entrega, Isla
Cacaluta and San Agustin, Bahias de Huatulco. Mean density of the sea urchins
was relatively constant during the study at all localities and there were significant
differences between La Entrega and the other localities. The calculated amount of
CaCO 3 removed by D. mexicanum showed variations between localities. The
lowest rate of bioerosion occurred at San Agustin and the highest at La Entrega.
They compared their results with those obtained by Herrera-Escalante et al. (2005)
and established that the recent urchin population decrease means a reduction in
their removal of coral CaCO 3 , and this reduction could be beneficial for coral reef
growing and recovery from stress. Nevertheless it could also signify an increase in
algal biomass and competition with corals for light and space.
Benitez-Villalobos et al. (2009) reported that until May 2009, the density of
D. mexicanum at the different reef communities of Bahias de Huatulco remained
relatively constant over time, with the highest density at La Entrega, where up to
2 The Echinoderms of Mexico
33
Few population ecology studies focused on particular species of echinoderms have
been carried out in Mexico. This is regrettable, especially in the case of echinoids
and holothurians, considering their importance as key organisms in the structure
and dynamics of benthic communities, and their potential for commercial
exploitation. Important species include the sea urchin D. mexicanum and the sea
cucumbers Isostichopus fuscus and Parastichopus parvimensis.
Echinoids
Espino-Barr et al. (1996) analyzed the density and population structure of
D. mexicanum on the rocky shore of the state of Colima in the Mexican Pacific as
part of a technical assessment for requests of permission for sea urchin fishing
along Colima and Jalisco shores. The results indicated an average density of
17,000 ind ha
-1 . There was an increase in gonad weight with respect to body
weight from May to August, followed by a decrease, indicating spawning during
those months. They propose the commercial exploitation of the species between
May and September when the gonads reach the greatest weight. Nevertheless they
proposed it be restricted to protect the species.
Herrera-Escalante et al. (2005) evaluated the importance of D. mexicanum as a
bioerosive agent of coral carbonate at Bahias de Huatulco and the relative magnitude
of coral accretion and bioerosion. The results showed that, in general, D. mexicanum
did not exert a significant role on coral reef community structure at the study area,
probably because of their relatively small size and low numbers. Regarding the
balance between bioerosion and carbonate production, they established that coral
accretion exceeded sea urchin erosion at all sites examined, indicating that at Bahias
de Huatulco coral reef communities were actively growing.
Benitez-Villalobos et al. (2008) evaluated the temporal variation of population
densities and bioerosion by D. mexicanum at Isla Montosa, La Entrega, Isla
Cacaluta and San Agustin, Bahias de Huatulco. Mean density of the sea urchins
was relatively constant during the study at all localities and there were significant
differences between La Entrega and the other localities. The calculated amount of
CaCO 3 removed by D. mexicanum showed variations between localities. The
lowest rate of bioerosion occurred at San Agustin and the highest at La Entrega.
They compared their results with those obtained by Herrera-Escalante et al. (2005)
and established that the recent urchin population decrease means a reduction in
their removal of coral CaCO 3 , and this reduction could be beneficial for coral reef
growing and recovery from stress. Nevertheless it could also signify an increase in
algal biomass and competition with corals for light and space.
Benitez-Villalobos et al. (2009) reported that until May 2009, the density of
D. mexicanum at the different reef communities of Bahias de Huatulco remained
relatively constant over time, with the highest density at La Entrega, where up to
2 The Echinoderms of Mexico
33