Growth performance and feed intake of the juvenile sea urchin Paracentrotus lividus fed on three diets
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1
Independent researcher, Spain
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2
Independent researcher, Spain
The progressive depletion of sea urchin populations, due to overfishing, habitat destruction and natural diseases, reinforces the need for effective aquaculture practices. This interest in sea urchin aquaculture increased in the last decades and produced an important number of studies aimed to improve the rearing conditions. However, most research attention was focused on the development of effective feeds for the grow out of adults promoting and enhancing the gonadal production. The feasibility of producing adult sea urchins is still hindered by the availability of excellent feeds, able to guarantee the fast growth of juveniles. Therefore, there is a great need for improving diets in order to accelerate somatic growth and reduce rearing time to market size.
Traditionally, the aquaculture of sea urchins have depended exclusively on seaweeds found locally. The macroalgae species are not permanently available throughout the year and their chemical composition change according to the season. Alternatively, formulated feed provide constant availability and nutritional composition. Feed formulations are essential to aquaculture but proteins from animal sources are relatively expensive and not sustainable. For these reasons, modern aquaculture is turning to alternative products, in particular land vegetable products, which are constantly available and more sustainable. Spinach has emerged as one of the best options for alternative ingredients. Its use as source of antioxidant has already been proved in gonadal growth, but its effectiveness has not been proved in somatic growth.
The aim of the present study was to evaluate the effect of three diets on feeding and growth rates of juveniles of the purple sea urchin Paracentrotus lividus. We tested three different diets: the first composed of the brown algae Saccorhiza polyschides, kelp fronds were collected on the beach and stored frozen until they were used; a second diet based on pellet normally used in aquaculture for abalone, and finally, a land vegetable diet based on spinach.
Hatchery produced P. lividus were reared at the Centro de Experimentación Pesquera in Asturias, Spain. In the study were used 360 six-month-old juveniles (14.9±0.9 mm; 1.7±0.3 g) from the same cohort. Sea urchins were starved for 3 weeks to ensure acclimatization and uniform nutritional status. Three diets were tested: a macroalgal diet (M) composed of frozen kelp fronds, a formulated diet (F) based on dry pellet, and a vegetable diet (V) based on fresh spinach leaves. Each one of the three diets was randomly assigned to triplicate batches and each batch was fed twice a week. The feed ration was adjusted depending on the absence or presence of non-ingested feed. The experiment was conducted for 18 weeks and biometric measurements of test diameter and body weight were taken for each sea urchin every 6 weeks. The food intake of the three diets was calculated once in each sampling period. Uneaten food was removed and dried in oven at 105ºC until a constant dry weight. Mean consumption per sea urchin per day (mg) and mean daily consumption as percentage of body weight (%) was calculated for the number of surviving sea urchins per treatment. The mean water temperature gradually increased from 15.2±1.2ºC in the first period to 16.5±1.1ºC in the last one.
All diets were well accepted by sea urchins and no significant difference was found in the survival between the different treatments. There was 100% survival in the three diets during the 18 weeks-experimental period. There were not significant differences in either diameter or weight of the sea urchins between treatments at the beginning of the experiment. But there were significant differences in both test diameter and wet weight in all subsequent sampling dates. The mean final test diameter was 20.8±1.5 mm (M), 21.1±1.4 mm (F) and 25.2±2.1 mm (V), with a significantly greater test diameter exhibited by sea urchins of V diet compared with M and F groups. No significant difference in the final test diameter was recorded between the sea urchins fed on M and F diets, but the sea urchins fed on formulated feed had a significantly higher final weight (4.4±0.8 g) than sea urchins fed on macroalgae (3.9±0.7 g). The highest final weight was obtained, once again, by sea urchins fed on spinach (6.3±1.4 g).
Feed intake, expressed in dry weight, varied substantially depending of the food provided. Overall, ingestion rates were greater with the artificial diet (F) than for the other two natural diets (M and V). The maximum rate of feeding was reached by F diet in the first sampling period, decreasing in subsequent periods. By contrast, daily comsumption of M and V diets increased progressively with the size of the sea urchins throughout the experimental period.
In the present study, the results demonstrate that the diet based on land vegetable was the most successful diet in promoting the growth of sea urchins. The good performance of the juveniles fed on spinach, regarding test diameter (81.75 µm day–1) and total wet weight (36.5 mg day-1), suggest that spinach is a very promising ingredient for sea urchin feed in order to maximize the somatic growth of P. lividus juveniles.
Acknowledgements
Thanks to the staff at the Centro de Experimentación Pesquera for their help during the experiment.
Keywords:
Paracentrotus lividus,
sea urchin,
Juveniles,
feeding,
Growth
Conference:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019.
Presentation Type:
Poster Presentation
Topic:
Fisheries, Aquaculture and Biotechnology
Citation:
De La Uz
S,
López
J,
Pérez
N and
Rodríguez
C
(2019). Growth performance and feed intake of the juvenile sea urchin Paracentrotus lividus fed on three diets.
Front. Mar. Sci.
Conference Abstract:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) .
doi: 10.3389/conf.fmars.2019.08.00095
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Received:
14 May 2019;
Published Online:
27 Sep 2019.
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Correspondence:
Ms. Silvia De La Uz, Independent researcher, Castropol, Asturias, Spain, silviadelauz@gmail.com