Raising Sea Urchin For Beginners
                     Raising Sea Urchin
Broodstock Nutrition
Most studies on adult sea urchin nutrition have focused on gonadal index (GI) improvementor 
gonad palatability, flavor, and/or color enhancement for human consumption (Shpigelet al. 2006; 
Symonds et al. 2007; Suckling et al. 2011). P. lividus has been the subject of most of these efforts, 
as it is the most commercially valuable European species. However, there is minimal data on the 
relevance of nutrition to spawning success or the effects of broodstock diet on offspring 
performance (Gago et al. 2009), and no prior information on the effects of maternal fatty acids (FA) 
on P. lividus larval and juvenile performance.
Recent work undertaken at AML as part of the ENRICH project has examined the effect of artificial 
diets on broodstock reproduction and offspring performance. The data showed that the higher 
protein and lipid contents of artificial diets respectively improved somatic growth (test diameter 
across the ambitus) and gonadal index (GI, measured as percentage of the body weight) (Carboni et 
al., in press). 
However, GI and fecundity were not related and females fed the natural kelp diet, which presented 
the smallest gonads, produced the highest Trim Size: 170mm x 244mm Brown c09.tex V1 - 
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Nnumber of eggs (Carboni et al., in press). This highlights that there is no clear relationship 
between gonad size and number of viable eggs produced after spawning induction. Sea urchin 
gonads have a dual role, functioning as both reproductive organs and nutrient stores (Russell 1998; 
Hughes et al. 2005). Uniquely, sea urchin gonads grow in size not only because game to genesis 
increases the size and number of germinal cells, but also because somatic cells (nutritive 
phagocytes) within the germinal epithelium store nutrient reserves (Walker et al. 2007). During the 
feeding trial, relative fecundity (number of eggs per gram of body weight) may have been enhanced 
by dietary xanthophyll, present in the kelp diet but absent in the artificial diets, as already reported 
by de Jong-Westman et al. (1995). 
Comparative analysis of fatty acid profiles of diets, gonads, and eggs revealed the presence in 
gonads of some FA that were not present in the diets and/or much higher contents of some long-
chain polyunsaturated fatty acids (LC-PUFA). Moreover, some unusual FA, such asnonmethylene 
interrupted (NMI), were found in gonads and eggs but not in the diet, suggesting that P. livid us may 
be capable of synthesizing these FA and accumulating them in the egg (Carboni et al. 2012a). 
This study also confirmed a previous observation (Gagoet al. 2009) that fatty acid profiles of the 
egg can be manipulated by broodstock diet, but that this had no significant impact on larval 
survival. This suggests that biotic and abiotic factors during larval rearing such as feeding, 
temperature, salinity, and water exchange may play a more important role in influencing larval 
survival than the FA levels of the eggs (Carboniet al. 2012b). 
In a detailed study on the effects of maternal provisioning, the evolution of P. livid us gonad fatty 
acid profiles during game to genesis was observed and described for the first time and, although no 
clear conclusion can be drawn, it appears that, amongLC-PUFA, eicosapentaenoic (EPA), and 
docosahexaenoic (DHA) acids are primarily accumulated during game to genesis, while arachidonic 
acid (ARA) is the only LC-PUFA clearly accumulated into the eggs along with NMI FA (Carboni et 
al. 2012a). Further studies on the effect of egg LC-PUFA content on embryo development and pre 
feeding larvae are required to determine if maternal provisioning of FA can influence sea urchin 
hatchery production output.
Breeding Programs
One of the main problems in culturing P. lividus commercially in Scotland is the time it takes to 
reach market size; at ambient temperatures this can be as much as 3 years. Substantial variation in 
juvenile growth rate within the same spawning cohort is also a problem; it can be alleviated to some 
extent by continuous and labor intensive grading, but a substantial percentage of individuals are 
currently discarded due to slow growth. The fact that this species is at the extreme northern limit of 
its range in Scotland and hence experiences relatively low water temperature is the main factor 
associated with slow growth rate.
Another potential issue is that animals derived from a relatively small population of original 
broodstock constitute the P. livid us stock held at SAMS and the AML. Inbreeding might be 
contributing to the slow growth observed in hatchery produced urchins, as has been shown with 
larvae of the purple sea urchin Strongy locentrotus purpuratus (Anderson and Hedgecock 2010) and 
other marine invertebrates (Evans et al. 2004; Keys et al. 2004). An evaluation of the genetic 
variability currently present at AML and comparison with genetic variability at other farms and in 
the wild in several European countries (Italy, Israel, and Ireland) will begin in 2012, in collaboration 
with the Institute of Aquaculture, University Trim Size: 170mm x 244mm Brown c09.tex V1 - 
01/31/2015 7:19 P.M. Page 215Sea Urchin Aquaculture in Scotland 215 of Stirling. This will 
represent the first step toward the implementation of best management practice for P. lividus 
broodstock and potentially, the establishment of a breeding program that could improve growth 
performance.
Hatchery Production
Larval Rearing Systems: SAMS
Gravid adults are induced to spawn by injection of 1.0 M KCl to the hemocoel via the peristomal 
membrane. Gravid individuals can be expected to spawn within 40 min and the gametes are then 
mixed to achieve fertilization. 
Hatching to release swimming blastocystsoccurs in 24–48 h depending on species and temperature. 
At SAMS, sea urchin larvae were reared in static seawater cultures in a culture room with air 
temperature controlled to 17 °C and were routinely brought to the point of metamorphosis without 
substantial losses in 14–21 days. 
Rearing methods were based on the methods developed for P. lividusby Leighton (Leighton 1995) 
at the Shellfish Research Laboratory in Galway, Ireland and modified for P. miliaris and for E. 
esculentus (Kelly et al. 2000; Jimmy et al. 2003). The larvae are reared in tanks of static, aerated, 
filtered seawater, at densities ranging from 1–4per milliter depending on their size. 
The water is replaced every 2–3 days by gently siphoning the larvae onto a sieve and returning them 
to a clean, replenished tank. Production of juveniles at SAMS is on the order of 10,000 juveniles 
annually, but in the future as production is scaled up larvae will be produced using the through-flow 
methods described below to reduce labor.
Larval Rearing Systems: AML
At AML, the current practice is to rear P. lividus larvae in a flow-through system at a density of four 
larvae per milliliter, under continuous light and using the microalgae Cricosphaeraelongata as feed. 
Production capacity is about 200,000 juveniles per annum.
P. lividus brood stock, raised at the Ardtoe Marine Laboratory and fed on Palmariapalmata, 
Laminaria digitata, and Saccharina lattisima (20:40:40, wet weight) are regularly induced to spawn 
by injection of 1.0 M KCl (40 µl/g of body weight) into the coelom via the peristomial membrane. 
Three females and three males are commonly used as breeding stock. Each female is able to spawn 
approximately 2 million eggs that are fertilized by adding a few drops of diluted sperm. Fertilization 
rate is assessed 2 h post fertilization and is usually approximately 98%. The fertilized eggs are left 
to hatch in static seawater without aeration for 24 h in the dark. Observed hatching rates are usually 
above 85%. Seawater used for spawning, hatching, and larval rearing is mechanically filtered and 
UV treated, and room temperature is maintained at 18±2 °C throughout the larval cultivation period.
Larvae are cultivated in aerated static water or in flow-through seawater with 100% daily water 
exchange. When a static system is used, a complete water exchange and thorough cleaning of the 
tanks is carried out every third day. A recent trial has, however, proven several advantages of using 
a flow-through system; notably larval survival was higher and labour required for hatchery 
production was reduced, ultimately increasing hatchery output (Carboni et al. 2013).
Larval Feeds
Sea urchin larvae at SAMS are usually fed the microalgae Dunaliella tertiolecta and 
Phaeodactylumtricornutum. Feeding is initiated once the larval stomach is formed (typically 48 
hafter fertilization) and feeding rates are increased with the acquisition of each pair of larval arms 
(Table 9.1.). The larvae are fed at each water exchange (every second or third day).
Larvae are cultured in a range of culture vessels, with the largest being 240 l. Algae are cultured in 
semi-continuous batch-systems (20 l vessels and 100 l polythene bags), where the algal culture is 
repeatedly fed and harvested once sufficient cells densities (>105 cells/ml)are achieved.
At SAMS, P. lividus and P. miliaris larvae have been successfully raised to settlement using the 
microencapsulated shrimp diets Lansy™ and Frippak™ as supplied by INVEfeeds (Liu et al. 
2007a, 2007b). 
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