255
fishing of sea urchins by scuba diving such as requiring expensive equipment such
as full diving team and boats and diving safety issues (James et al. 2018).
In United States, West Coast sea urchins are commercially harvested by divers
using “hooka” diving gear, consisting of a low-pressure air compressor that feeds air
through a hose from the vessel to the divers. Sea urchins are harvested from the
ocean bottom with a hand-held rake or hook and put into a hoop-net bag or wire
basket. The basket is winched onto the boat and emptied into a larger net bag (Price
2000). Since urchins are selected manually with this method, the fact that individuals of the desired size can be selected by divers and the undersized sample can be
sent back without significant mortality contributes to the sustainability of sea
urchins (James et al. 2018). Urchins are harvested with a drag in areas where diving
is not feasible.
The average harvest size has decreased gradually due to over exploitation in
countries where sea urchins are fished. For this reason, regulations such as limiting
the harvest season and creating protection areas have encouraged the sea urchin
culture (Sætra 2019).
4.2.1.5 Some Important Species of Sea Urchins
Various types of sea urchins are harvested for their roe globally. Green sea urchin
(Strongylocentrotus pulcheriius), red sea urchin (Strongylocentrotus franciscanus),
and purple sea urchin (Strongylocentrotus intermedius) are the species of highest
demand globally. Pseudocentratus depressus, Heliocidaris crassispina, and
Strongylocentrotus droebachiensis are also in good demand (Bledsoe et al. 2003).
Tripneustes ventricosus (Lamarck, 1816) (White Sea Urchin)
The White Sea urchin is a member of the sea urchin group and is large. As with all
urchins, it has a spherical exoskeleton (test) consisting of fused calcareous plates
placed in two separate groups containing five ambulacral and five inter-ambulacral
series. The plate series extend from the mouth in the centre of the animal’s ventral
side to the anus in the centre of the dorsal side. They use their spines for defence
against predators. They can do this while on the move. The reproductive system of
the white Sea urchin consists of five gonads, sometimes more or less fused and
suspended by mesenterial strands to the “roof” of both male and female urchins.
The gonads are not only the source of eggs or sperm, which are referred to as roe,
but also serve as the main nutrient storage organ. Gonads tend to be bright orange in
colour in females and light yellow in males. The white sea urchin is found along the
west coast of Africa from the Gulf of Guinea to Walvis Bay and along the western
central Atlantic Ocean from Bermuda, to the Carolina coast of the United States of
America, and the Caribbean to Brazil. White sea urchins live in various shallow
water habitats such as rock rubble, moss rock circles and sea grass beds. Sometimes
many White Sea urchins form in tidal pools. However, it tends to high death events
due to very high water-temperatures and periodic subaerial exposure of such habitats, especially in tides (Pena et al. 2010).
4.2 Sea Urchin
fishing of sea urchins by scuba diving such as requiring expensive equipment such
as full diving team and boats and diving safety issues (James et al. 2018).
In United States, West Coast sea urchins are commercially harvested by divers
using “hooka” diving gear, consisting of a low-pressure air compressor that feeds air
through a hose from the vessel to the divers. Sea urchins are harvested from the
ocean bottom with a hand-held rake or hook and put into a hoop-net bag or wire
basket. The basket is winched onto the boat and emptied into a larger net bag (Price
2000). Since urchins are selected manually with this method, the fact that individuals of the desired size can be selected by divers and the undersized sample can be
sent back without significant mortality contributes to the sustainability of sea
urchins (James et al. 2018). Urchins are harvested with a drag in areas where diving
is not feasible.
The average harvest size has decreased gradually due to over exploitation in
countries where sea urchins are fished. For this reason, regulations such as limiting
the harvest season and creating protection areas have encouraged the sea urchin
culture (Sætra 2019).
4.2.1.5 Some Important Species of Sea Urchins
Various types of sea urchins are harvested for their roe globally. Green sea urchin
(Strongylocentrotus pulcheriius), red sea urchin (Strongylocentrotus franciscanus),
and purple sea urchin (Strongylocentrotus intermedius) are the species of highest
demand globally. Pseudocentratus depressus, Heliocidaris crassispina, and
Strongylocentrotus droebachiensis are also in good demand (Bledsoe et al. 2003).
Tripneustes ventricosus (Lamarck, 1816) (White Sea Urchin)
The White Sea urchin is a member of the sea urchin group and is large. As with all
urchins, it has a spherical exoskeleton (test) consisting of fused calcareous plates
placed in two separate groups containing five ambulacral and five inter-ambulacral
series. The plate series extend from the mouth in the centre of the animal’s ventral
side to the anus in the centre of the dorsal side. They use their spines for defence
against predators. They can do this while on the move. The reproductive system of
the white Sea urchin consists of five gonads, sometimes more or less fused and
suspended by mesenterial strands to the “roof” of both male and female urchins.
The gonads are not only the source of eggs or sperm, which are referred to as roe,
but also serve as the main nutrient storage organ. Gonads tend to be bright orange in
colour in females and light yellow in males. The white sea urchin is found along the
west coast of Africa from the Gulf of Guinea to Walvis Bay and along the western
central Atlantic Ocean from Bermuda, to the Carolina coast of the United States of
America, and the Caribbean to Brazil. White sea urchins live in various shallow
water habitats such as rock rubble, moss rock circles and sea grass beds. Sometimes
many White Sea urchins form in tidal pools. However, it tends to high death events
due to very high water-temperatures and periodic subaerial exposure of such habitats, especially in tides (Pena et al. 2010).
4.2 Sea Urchin