predation, chiefly induced by overexploited fish species, exert in the control of
populations of D. africana. Consequently, overexploitation of sea urchin predators
has been directly linked to large densities of D. africana, which causes the direct
elimination of erect algal beds and results in the prevalence of rocky unvegetated
bottoms in the rocky subtidal (‘‘urchin barren grounds’’). The disappearance of
these algal beds limits benthic primary production, as well as the amount of food
and shelter these algal habitats provide for associated invertebrates and fishes. This
exacerbates, even more, the deterioration of marine biodiversity in the shallow
subtidal waters of the Canarian Archipelago. Last, but not least, there is a positive
relation between the increases in densities of D. africana and the recent increase in
sea water temperature (Hernández et al. 2010a). This work is based on a historical
compilation of sea water surface temperature data from 1948 to the present and a
continuous collection of data on settlement, recruitment and densities from 2001 to
2008. The major conclusion is that the increase in sea water temperature, coupled
with the prevalence of ‘‘urchin barren grounds’’, enhanced the survivorship of D.
africana recruits. This work predicts an increase in the densities of this sea urchin
as well as the extension of ‘‘urchin barren grounds’’ under the predicted scenario of
raising temperatures. In conclusion, the rise in sea water temperature has been a
relevant factor in conjunction with overfishing of sea urchin predators to enhance
densities of the sea urchin.
The high level of social interest about the effect of high densities of D. africana
has not only increased the publication of scientific manuscripts. Publications have
disseminated the characteristics of the sea urchin to society in non-technical language (Brito et al. 2004; Tuya et al. 2004d; Hernández et al. 2009). These publications have tried to raise awareness on the necessity to implement conservation
strategies to guarantee the sustainability and conservation of benthic communities
in the Canary Islands since high densities of the sea urchins are directly connected
with perturbed bottoms. Indeed, increasing interest on preserving the rocky subtidal reefs of the Canaries has been consolidated by the development of the project
Diademar (Instituto Canario de Ciencias Marinas), which is exploring ways to
commercially exploit the high densities of the sea urchin, mainly for human
consumption of gonads, as a way of population control. In addition, the Viceconsejería de Medio Ambiente and the Viceconsejería de Pesca of the Canary
Government and several insular administrations (Cabildos) have implemented a
program to periodically eliminate this sea urchin in large experimental plots across
the entire archipelago. The goal is to preserve algal beds (but see Sect. 15.5).
Other echinoderms have not received the same focus of attention within the
scientific community. There are only a few studies on other species of sea urchins,
such as the genetic diversity (Calderon et al. 2008) and a description of the
juvenile phases of Paracentrotus lividus (Hernández et al. 2005), and the spatial
distribution patterns of P. lividus and Arbacia lixula across depth gradients in the
shallow subtidal (Tuya et al. 2007). Other works focused on some ecological
aspects, such the relation between densities of D. africana and other species of
echinoderms (Ortega et al. 2009), particularly the holothurians (Tuya et al. 2006b).
15 Echinoderms of the Canary Islands, Spain
483
populations of D. africana. Consequently, overexploitation of sea urchin predators
has been directly linked to large densities of D. africana, which causes the direct
elimination of erect algal beds and results in the prevalence of rocky unvegetated
bottoms in the rocky subtidal (‘‘urchin barren grounds’’). The disappearance of
these algal beds limits benthic primary production, as well as the amount of food
and shelter these algal habitats provide for associated invertebrates and fishes. This
exacerbates, even more, the deterioration of marine biodiversity in the shallow
subtidal waters of the Canarian Archipelago. Last, but not least, there is a positive
relation between the increases in densities of D. africana and the recent increase in
sea water temperature (Hernández et al. 2010a). This work is based on a historical
compilation of sea water surface temperature data from 1948 to the present and a
continuous collection of data on settlement, recruitment and densities from 2001 to
2008. The major conclusion is that the increase in sea water temperature, coupled
with the prevalence of ‘‘urchin barren grounds’’, enhanced the survivorship of D.
africana recruits. This work predicts an increase in the densities of this sea urchin
as well as the extension of ‘‘urchin barren grounds’’ under the predicted scenario of
raising temperatures. In conclusion, the rise in sea water temperature has been a
relevant factor in conjunction with overfishing of sea urchin predators to enhance
densities of the sea urchin.
The high level of social interest about the effect of high densities of D. africana
has not only increased the publication of scientific manuscripts. Publications have
disseminated the characteristics of the sea urchin to society in non-technical language (Brito et al. 2004; Tuya et al. 2004d; Hernández et al. 2009). These publications have tried to raise awareness on the necessity to implement conservation
strategies to guarantee the sustainability and conservation of benthic communities
in the Canary Islands since high densities of the sea urchins are directly connected
with perturbed bottoms. Indeed, increasing interest on preserving the rocky subtidal reefs of the Canaries has been consolidated by the development of the project
Diademar (Instituto Canario de Ciencias Marinas), which is exploring ways to
commercially exploit the high densities of the sea urchin, mainly for human
consumption of gonads, as a way of population control. In addition, the Viceconsejería de Medio Ambiente and the Viceconsejería de Pesca of the Canary
Government and several insular administrations (Cabildos) have implemented a
program to periodically eliminate this sea urchin in large experimental plots across
the entire archipelago. The goal is to preserve algal beds (but see Sect. 15.5).
Other echinoderms have not received the same focus of attention within the
scientific community. There are only a few studies on other species of sea urchins,
such as the genetic diversity (Calderon et al. 2008) and a description of the
juvenile phases of Paracentrotus lividus (Hernández et al. 2005), and the spatial
distribution patterns of P. lividus and Arbacia lixula across depth gradients in the
shallow subtidal (Tuya et al. 2007). Other works focused on some ecological
aspects, such the relation between densities of D. africana and other species of
echinoderms (Ortega et al. 2009), particularly the holothurians (Tuya et al. 2006b).
15 Echinoderms of the Canary Islands, Spain
483