growing semi-professional activity. However, the general overfishing situation of
the traditional resources could favour an increase of sea urchin fisheries in the near
future (Thorpe et al. 2000). At this time accurate stock studies are needed to
promote appropriate regulations for a sustainable fishing activity and prevent the
collapse of this resource.
Human fishing activity effects on P. lividus populations, although it has not
been studied in the Canary Islands, are evident in many intertidal habitats of the
islands compared to remote or marine protected areas locations. In these areas, of
human use, P. lividus is scarce and is restricted to inaccessible deep cavities in the
basaltic volcanic rock. In the Canary Islands, fishing activities in the intertidal are
regulated. Only Sport Fishing Licence holders can fish for shellfish during
weekends and holidays. No number or close season regulations exist. In our
opinion, this is an insufficient measure to regulate shellfish fishing activities that
favors overfishing in many intertidal benches. This situation has focused the
attention of managers who have recently funded a National Project to optimize and
promote P. lividus culture in Galicia and in the Canary Islands. This project aims
to improve the technical and biological aspect of larval culture and to develop
culture systems at different locations along the Spanish coast to provide juveniles
for farms or repopulation. This project was supported by the Ministerio de Medio
Ambiente y Medio Rural y Marino through the Junta Asesora de Cultivos Marinos
(JACUMAR). It has contributed to the improvement of spawning and fertilization,
larval culture and metamorphosis-settlement.
In addition to human collection, other factors such as temperature and competition also modify the abundance of P. lividus. The Canary Islands are the
southern-most limit of this temperate species. It is more abundant off the eastern,
colder islands. Although, there are no specific studies that assess the temporal
abundance of this sea urchin, we have noticed that anomalous warm summers like
occurred in 2003 were associated with localized mass mortalities at several
intertidal and subtidal locations in Tenerife (Girard et al. in press). The sea water
warming trend in the Canarian Arquipelago (Hernández et al. 2010a) will probably
increase the frequency of these mortality events in the future, which would
decrease the intertidal populations. Bathymetric segregation of P. lividus occurs in
the littoral area. It is more abundant in shallow waters between 1–5 m (Tuya et al.
2007). This bathymetric segregation is mainly caused by competition with the
grazing of the abundant D. africana which has greatly reduced food resources and
has limited P. lividus distribution to shallow macroalgae stands refuges. Otherwise
it could reach deeper waters as in the Mediterranean Sea. In summary, the
depletion of macroalgae stands by D. africana, sea water warming and human
collection is modifying the potential distribution of P. lividus in the archipelago.
In recent years, due to the outbreak of D. africana, local management agencies
have become interested in the development of a commercial sea urchin fishery. At
the same time, these agencies are proposing reducing activity of D. africana at
some sites to gain in the conservation status of rocky bottoms of the Canary
Islands. However, both strategies have the potential to restore local unproductive
barren grounds to algal stands (Brito et al. 2004). These strategies should be
500
J. C. Hernández et al.
the traditional resources could favour an increase of sea urchin fisheries in the near
future (Thorpe et al. 2000). At this time accurate stock studies are needed to
promote appropriate regulations for a sustainable fishing activity and prevent the
collapse of this resource.
Human fishing activity effects on P. lividus populations, although it has not
been studied in the Canary Islands, are evident in many intertidal habitats of the
islands compared to remote or marine protected areas locations. In these areas, of
human use, P. lividus is scarce and is restricted to inaccessible deep cavities in the
basaltic volcanic rock. In the Canary Islands, fishing activities in the intertidal are
regulated. Only Sport Fishing Licence holders can fish for shellfish during
weekends and holidays. No number or close season regulations exist. In our
opinion, this is an insufficient measure to regulate shellfish fishing activities that
favors overfishing in many intertidal benches. This situation has focused the
attention of managers who have recently funded a National Project to optimize and
promote P. lividus culture in Galicia and in the Canary Islands. This project aims
to improve the technical and biological aspect of larval culture and to develop
culture systems at different locations along the Spanish coast to provide juveniles
for farms or repopulation. This project was supported by the Ministerio de Medio
Ambiente y Medio Rural y Marino through the Junta Asesora de Cultivos Marinos
(JACUMAR). It has contributed to the improvement of spawning and fertilization,
larval culture and metamorphosis-settlement.
In addition to human collection, other factors such as temperature and competition also modify the abundance of P. lividus. The Canary Islands are the
southern-most limit of this temperate species. It is more abundant off the eastern,
colder islands. Although, there are no specific studies that assess the temporal
abundance of this sea urchin, we have noticed that anomalous warm summers like
occurred in 2003 were associated with localized mass mortalities at several
intertidal and subtidal locations in Tenerife (Girard et al. in press). The sea water
warming trend in the Canarian Arquipelago (Hernández et al. 2010a) will probably
increase the frequency of these mortality events in the future, which would
decrease the intertidal populations. Bathymetric segregation of P. lividus occurs in
the littoral area. It is more abundant in shallow waters between 1–5 m (Tuya et al.
2007). This bathymetric segregation is mainly caused by competition with the
grazing of the abundant D. africana which has greatly reduced food resources and
has limited P. lividus distribution to shallow macroalgae stands refuges. Otherwise
it could reach deeper waters as in the Mediterranean Sea. In summary, the
depletion of macroalgae stands by D. africana, sea water warming and human
collection is modifying the potential distribution of P. lividus in the archipelago.
In recent years, due to the outbreak of D. africana, local management agencies
have become interested in the development of a commercial sea urchin fishery. At
the same time, these agencies are proposing reducing activity of D. africana at
some sites to gain in the conservation status of rocky bottoms of the Canary
Islands. However, both strategies have the potential to restore local unproductive
barren grounds to algal stands (Brito et al. 2004). These strategies should be
500
J. C. Hernández et al.