434
J. Iglesias and L. Fuentes
23.2.4 Physical and Chemical Parameters
Physical and chemical parameters in broodstock tanks are important determinants
of successful egg laying. Density should not exceed 5 kg m
−3
and tanks should be
provided with filtered seawater and a minimal renewal rate of 400–800 % day
−1
in order to maintain abiotic water parameters at optimal levels (Iglesias, personal
communication). Dissolved oxygen levels should be kept around 100 % saturation.
Temperature should follow that of the natural seawater temperature cycle as much
as possible and should not drop below 14 °C nor exceed 25 °C (Iglesias et al. 2007).
Similarly, water salinity should simulate local seawater values. Semi-dark conditions are commonly used, but natural photoperiod with shaded natural light is also
utilized (De Wolf et al. 2011). Individual shelters (terracotta or polyvinyl chloride
(PVC) tubes) should be provided to facilitate egg laying.
23.3 Spawning Process
23.3.1 Female Conditions
Each spawning female with its strings of eggs should be transferred to an individual
tank to avoid being disturbed by conspecifics and to facilitate the counting of eggs
laid and hatched paralarvae. Tank volume should be 200–500 L, and temperature
must be the same as the broodstock tank.
Females take care of egg masses by oxygenating and cleaning them throughout the
embryonic development process. They do not feed during this period and consequently reduce their weight; a 4-kg female, for example, can lose 30 % of its weight during
this process (Fig. 23.1). Under suboptimal or stressful circumstances, females may
leave the shelter and abandon the egg clusters. In this case, hatching percentage can
fall to as little as 50 % due to egg detachment, fungal infection, etc. (Lenzi et al. 2002).
Exceptionally, another different female from the broodstock may take over the eggcaring role (Iglesias, personal communication). A special incubator to maintain eggs
without a female was patented by Rosas et al. (2010). It was originally developed for
O� maya, a large-egg species, but is currently being tested for O� vulgaris in the Austral University of Chile. Simple PVC tube systems with continuous water flow and
aeration have also been successfully tested at the Spanish Institute of Oceanography.
23.3.2 Egg Handling
A weekly check of each egg cluster should be established to estimate the time in
days necessary to hatch according to the incubation temperature. Using this method,
the hatching date can be predetermined in order to estimate in advance the needs for
J. Iglesias and L. Fuentes
23.2.4 Physical and Chemical Parameters
Physical and chemical parameters in broodstock tanks are important determinants
of successful egg laying. Density should not exceed 5 kg m
−3
and tanks should be
provided with filtered seawater and a minimal renewal rate of 400–800 % day
−1
in order to maintain abiotic water parameters at optimal levels (Iglesias, personal
communication). Dissolved oxygen levels should be kept around 100 % saturation.
Temperature should follow that of the natural seawater temperature cycle as much
as possible and should not drop below 14 °C nor exceed 25 °C (Iglesias et al. 2007).
Similarly, water salinity should simulate local seawater values. Semi-dark conditions are commonly used, but natural photoperiod with shaded natural light is also
utilized (De Wolf et al. 2011). Individual shelters (terracotta or polyvinyl chloride
(PVC) tubes) should be provided to facilitate egg laying.
23.3 Spawning Process
23.3.1 Female Conditions
Each spawning female with its strings of eggs should be transferred to an individual
tank to avoid being disturbed by conspecifics and to facilitate the counting of eggs
laid and hatched paralarvae. Tank volume should be 200–500 L, and temperature
must be the same as the broodstock tank.
Females take care of egg masses by oxygenating and cleaning them throughout the
embryonic development process. They do not feed during this period and consequently reduce their weight; a 4-kg female, for example, can lose 30 % of its weight during
this process (Fig. 23.1). Under suboptimal or stressful circumstances, females may
leave the shelter and abandon the egg clusters. In this case, hatching percentage can
fall to as little as 50 % due to egg detachment, fungal infection, etc. (Lenzi et al. 2002).
Exceptionally, another different female from the broodstock may take over the eggcaring role (Iglesias, personal communication). A special incubator to maintain eggs
without a female was patented by Rosas et al. (2010). It was originally developed for
O� maya, a large-egg species, but is currently being tested for O� vulgaris in the Austral University of Chile. Simple PVC tube systems with continuous water flow and
aeration have also been successfully tested at the Spanish Institute of Oceanography.
23.3.2 Egg Handling
A weekly check of each egg cluster should be established to estimate the time in
days necessary to hatch according to the incubation temperature. Using this method,
the hatching date can be predetermined in order to estimate in advance the needs for