First assessment of the population structure and reproductive cycle of the sea urchin Sphaerechinus granularis (Lamarck 1816) in Madeira Island: a potential new candidate to echinoculture
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1
Agência Regional para o Desenvolvimento da Investigação Tecnologia e Inovação, OOM - Oceanic Observatory of Madeira, Portugal
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2
Direção Regional das Pescas da Região Autonoma da Madeira, Centro de Maricultura da Calheta, Portugal
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3
Centro de Ciências do Mar (CCMAR), Portugal
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4
Centro Interdisciplinar de Pesquisa Marine e Ambiental (CIIMAR), Portugal
Sea urchins play important roles in coastal ecosystems as key ecological species and as harvesting and aquaculture target species. Several species of sea urchin are drivers of coastal ecosystems structure and function and their impact depends of species density and grazing activity upon macrophytes and seagrasses. On the other hand, sea urchins gonads (or roe) are a culinary delicacy with high market value and global market demand of 60 000 tonnes per year. In Europe, the species more appreciated is Paracentrotus lividus but Strongylocentrotus droebachiensis and Sphaerechinus granularis are also consumed. In Portugal, the whole sea urchin trade intensified in the latest years with the weight of whole sea urchin traded in first sale auction increasing from 17 tonnes in 2015 to 67 tonnes in 2016. The high demand, high market value and the over-exploited status of most of the edible sea urchins’ populations are the main reasons for the development of aquaculture production for these species.
Madeira archipelago within the biogeographic region of Macaronesia (Atlantic Ocean 32°42'N 17°W) includes in its coastal fauna several species of sea urchins. The aim of this study was to evaluate the population structure and assess the reproductive season and roe characteristics of the purple sea urchin S. granularis off Madeira Island. Ultimately, the present study aimed at gathering information to evaluate the viability of producing the species throughout aquaculture. Therefore, during the year of 2017, monthly samples of 10 individuals were collected by scientific SCUBA diving from subtidal rocky reef bottoms in Funchal, every three months at Caniçal and twice a year (Summer and Autumn) in Porto Santo Island. Additionally, surveys to estimate abundance of the species, along the coasts of Madeira were carried out every three months and twice a year in Porto Santo island. Underwater visual census (UVC’s) were performed along strip transects, counting every sea urchin and all the macrofauna that can be identified as individual (e.g. starfish, crabs, etc.) occurring along the 25 m transect within one meter in each side of the line. The individuals collected were measured (test diameter and height) to the nearest 0.05 mm and weighted to the nearest 0.01 g. The sea urchin gonads were weighted individually to nearest 0.01 g, their colour was scored with a 4 stages colour scale and quantified by spectrophotometry. Gonads samples were preserved for histological and biochemical analysis.
The results obtained from our study reveal that the species S. granularis occur in low densities in the rocky reefs surveyed, always less than 0.1 individuals/m2 with no significant differences being recorded within seasons. The rocky reef surveyed in Porto Santo, showed the highest density (0.08 individuals/m2), yet too low to be compatible with harvesting the species in nature to feed aquaculture purposes. The sea urchins collected are, in average 65.61 ± 10.04 mm wide, weighting 138.17 ± 53.22 g with the following width — weigh relationship: Weight (g) = 0.002*width(mm)2.66, and their gonads weighted in average 5.69 ± 4.82 g. No statistical significant differences were found in the population morphometry between sampling sites, however there are monthly differences in the gonads size and gonadal index, indicating that spawning can occur during autumn (Figure 1). 43 % of the gonads presented a bright yellow or orange colour and 39 % presented a paler yellow or arrange colour, classified as acceptable colour for the commercial roe industry. The preliminary results showed that. in the Macaronesia region, this species presented gonad characteristics as weight and colour that can favour their production in captivity, however the densities found in its natural habitat is yet too low to be compatible with harvesting the species in nature to feed aquaculture purposes.
Acknowledgements
Ricardo José, Claudia Ribeiro and Pedro Neves were financially supported by the Oceanic Observatory of Madeira Project (M1420-01-0145-FEDER-000001-Observatório Oceanico da Madeira-OOM). Sílvia Lourenço was financially supported by a post-doctoral grant form ARDITI (Regional Agency for Development of Research, Technology and Innovation of Madeira), Project M1420-09-5369-FSE-000001.
Keywords:
Purple sea urchin,
Shaepherechinus granularis,
Reproduction,
harvest,
Aquaculture
Conference:
IMMR'18 | International Meeting on Marine Research 2018, Peniche, Portugal, 5 Jul - 6 Jul, 2018.
Presentation Type:
Oral Presentation
Topic:
Aquaculture
Citation:
José
R,
Ribeiro
C,
Neves
P and
Lourenço
S
(2019). First assessment of the population structure and reproductive cycle of the sea urchin Sphaerechinus granularis (Lamarck 1816) in Madeira Island: a potential new candidate to echinoculture.
Front. Mar. Sci.
Conference Abstract:
IMMR'18 | International Meeting on Marine Research 2018.
doi: 10.3389/conf.FMARS.2018.06.00133
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Received:
28 Apr 2018;
Published Online:
07 Jan 2019.
*
Correspondence:
Mr. Ricardo José, Agência Regional para o Desenvolvimento da Investigação Tecnologia e Inovação, OOM - Oceanic Observatory of Madeira, Funchal, 9020-105, Portugal, ricardo.jose@oom.arditi.pt