Growth, mortality and deformities evolution of the common cockle (Cerastoderma edule L.): suspended culture vs. natural sandflat culture
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1
Universidade de Vigo, Estación de Ciencias Mariñas de Toralla, Spain
The cockle Cerastoderma edule (Linnaeus, 1758) has traditionally been the most important shellfish resource in terms of biomass in Galicia (NW Spain). However, the high mortalities caused by marteiloisis from 2012 (Villalba et al., 2014) has drastically reduced the stock. This fact turned the cockle into a species of interest for aquaculture and seed supply. Although a great effort is being made to study cockle genetics, diseases and marteilia infestation, information about some biological aspects as growth or culture methodology and technology is scarce.
Maintaining seed bivalves in suspended growth systems optimises growth and allows providing seed for translating to grow areas or restocking in a short period of time. However, maintaining bivalve seed in suspended systems affect shell deposition and in turn shell growth and shape, resulting in the apparition of deformed individuals that are not marketable. Although previous studies concluded that obtain cockle seed of 22 mm in suspended system in one year is possible, the deformed individuals account for 27% (Hernández-Otero et al., 2015). As a result, other technologies are needed.
This study evaluates growth, mortality and shell deformation of normal and deformed cockles (size > 20 mm) cultured in suspended systems without substrate or in a natural sandflat. The aims of this work are 1) to improve the zoo technology of the species, 2) to identify the deformities that appear during C. edule culture, 3) to test the possible recuperation of deformed individuals in order to be commercialised in fresh or used for restocking and 4) to determine the best culture system in terms of growth, mortality and morphometry.
Juvenile cockles (2.7 mm, two months old) were produced at the hatchery facilities of the Estación de Ciencias Mariñas de Toralla (ECIMAT, Universidade de Vigo) and grown to a size of 26 mm in suspended culture system as described in Hernández-Otero et al. (2015). After one year, two hundred adult individuals (26 mm) were randomly selected, individually marked and divided into two sets: 100 morphometrically normal individuals and 100 morphometrically abnormal or deformed individuals. For each set, 50 specimens were kept in suspended culture system in the Illa de Toralla (42.20° N, 8.80° W) (Ría de Vigo, NW Spain) and 50 individuals were translated to two buried cages (62x47x33 cm) in an intertidal sandflat located in Cesantes (42.29° N, 8.61° W) (Ría de Vigo). Every month between June and October 2015, marked individuals were photographed and shell length (maximum length on the anterior-posterior axis), height (maximum length on the lateral axis) and width (maximum length on the dorsal-ventral axis) were measured in situ with electronic callipers to the nearest 0.01 mm. Cages were cleaned and dead individuals were removed. As no scale had previously been established for deformed bivalves, individuals were firstly described according to different qualitative descriptors (opening of the shell, presence of dented or spherical shape, presence of a protrusion at the end of the shell, etc.) and finally included into five stages: 1) normal shells (Figure 1A, B), 2) open shells (deformity 1, Figure 1C), 3) recently close shells with sharped edge or “sharped shells” (deformity 2, Figure 1D), 4) heart shape shells (deformity 3, Figure 1E) and 5) shells with a protrusion or “pointed shells” (deformity 4, Figure 1F). Evolution of each stage during the experiment was graphically represented. The morphometric relationships between shell length (SH) and shell height (SH), shell length and shell width (SW) were estimated for each stage by fitting a linear function to the data (Ricker, 1973). Paired t-tests were performed to determine any significant differences for the five stages (Zar, 2010). Adult growth data observed for the different stages and locations was plotted. With the aim to provide the complete C. edule growth curve length at age data for larval, postlarval and juveniles stages were obtained from Hernández-Otero et al. (2015) and graphically represented.
In contrast with the observed with deformed bivalves as Ruditapes philippinarum, where deformed individuals recovered the spherical shape after being seeded on a natural bed (Royo., A. et al. 2005a, b), deformed individuals did not recover the normal shape with any of the culture systems during the experiment (Figure 2). However, better results were obtained with individuals seeded on the sandflat. Thus 26% of normal individuals cultured on the suspended system without substrate acquired deformed shapes at the end of the experiment. Besides, 14% of deformed individuals with open shells (deformity 1) buried at the sandflat recovered the normal shape when the experiment finished. Although mortalities are very high at any location or any morphometric stage, probably due to the marteilia infestation described and the late translation of deformed individuals, survivorship attained at the sandflat (26%) was slightly higher than the observed at the suspended system (16%). Survivorship between deformities could not be compared since n is very small for stages 2-4 (Figure 2). In the light of these results, we recommend to seed deformed individuals before or avoid them for seeding.
Regarding the allometric relationships, we were not able to differentiate the morphometric stages described between them, since linear regressions of SW/SL did not differed significantly between stages (p > 0.05) and, although linear regressions of SW/SL between deformities 3 (“heart shell”) and 4 (“pointed shells”) and the rest of the stages were significantly different (p < 0.01), due to the spherical shape characteristic of the deformity 3 and the pointed shape of the deformity 4, we could not differentiate the normal individuals and the deformities 1 (“opened shells”) and 2 (“sharped shells”) (Figure 3).
The growth pattern of C.edule obtained in this study is similar to the observed by other authors (e.g. Molares et al., 2001; Ramón, 2003; Rueda et al., 2005). Thus, C. edule was 19 mm at six months old, 22 mm at 1 year old and 31 mm when the experiment finished, 1.5 years after fertilisation (Figure 4). During winter, a growth cessation period was observed (Figure 4), probably do to a combination of downwelling conditions and low seawater temperature values, as regarded for most bivalves of template regions.
Acknowledgements
The authors thank ECIMAT staff and direction for supporting this work. We also acknowledge the cofradía (fishers’ guild) of Redondela and specially Sira Pereira, the Technical Assistant of the cofradía, for providing their facilities and sampling assistance.
References
Fraga, F. 1981. Upwelling off the Galician coast, northwest Spain. In: Richards FA (ed) Coastal upwelling. American Geophysical Union, Washington, DC, p: 176-182
Hernández Otero, A.; Martínez Casal, A.; Costoya, N.; González-García, M.D.M.; Costas, D. Crecimiento de semilla de berberecho Cerastoderma edule (L.) en cultivo suspendido. XV CNA (Congreso Nacional de Acuicultura) y I CIA (Congreso Ibérico de Acuicultura) (Poster). Huelva, 13 - 16 octubre 2015.
Molares, J., Caamaño, A., Leal, M.C.B., y Parada, J.M., 2001. Determinación dos parámetros da curva de crecemento, os coeficientes de mortalidade e a talla mínima comercial do berberecho (Cerastoderma edule) en Galicia. Consellería de Pesca e Asuntos Marítimos, CIMA, Memoria da actividade do ano 2001: 70-71.
Ramón, M., 2003. Population dynamics and secondary production of the cockle Cerastoderma edule (L.) in a backbarrier tidal flat of the Wadden Sea. Scientia Marina. 67: 429–443.
Ricker, W.E., 1973. Linear regressions in fishery research. Journal of the Fisheries Research Board of Canada 30, 409-434.
Royo, P. Ruiz Azcona y R. Navaja (2005a). Engorde de almeja japonesa Ruditapes philippinarum (Adams & Reeve, 1850) con deformaciones producidas en la etapa de preengorde. Bol. Inst. Esp. Oceanogr. 21 (1-4): 415-424
Royo, P. Ruiz Azcona y R. Navaja (2005b). Preengorde intensivo de almeja japonesa Ruditapes philippinarum (Adams & Reeve, 1850) en sustrato, en la zona intermareal. Bol. Inst. Esp. Oceanogr. 21 (1-4): 447-454
Rueda, J.L., Smaal, A.C., Scholten, H. 2005. A growth model of the cockle (Cerastoderma edule L.) tested in the Oosterschelde estuary (The Netherlands). Journal of Sea Research 54 (2005) 276–298
Villalba, A., Iglesias, D., Ramilo, A., Darriba, S., Parada, J.M., No, E., Abollo, E., Molares, J. y Carballal, M.J. 2014. Cockle Cerastoderma edule fishery collapse in the Ría de Arousa (Galicia, NW Spain) associated with the protistan parasite Marteilia cochillia. Diseases of Aquatic Organisms. 109(1): 55-80.
Zar, H., 2010. Biostatistical Analysis, Fifth Edition. Prentice Hall, NJ (944 p)
Keywords:
Cerastoderma edule,
Cockle,
culture,
Shell deformation,
Growth,
Suspended culture,
Ongrowing
Conference:
XIX Iberian Symposium on Marine Biology Studies, Porto, Portugal, 5 Sep - 9 Sep, 2016.
Presentation Type:
Poster Presentation
Topic:
4. FISHERIES, AQUACULTURE AND BIOTECHNOLOGY
Citation:
Martínez
A,
Hernández Otero
A,
Costoya
N,
González
M and
Costas
D
(2016). Growth, mortality and deformities evolution of the common cockle (Cerastoderma edule L.): suspended culture vs. natural sandflat culture.
Front. Mar. Sci.
Conference Abstract:
XIX Iberian Symposium on Marine Biology Studies.
doi: 10.3389/conf.FMARS.2016.05.00207
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Received:
30 Apr 2016;
Published Online:
03 Sep 2016.
*
Correspondence:
PhD. Alba Hernández Otero, Universidade de Vigo, Estación de Ciencias Mariñas de Toralla, Vigo, 36331, Spain, alba.hernandez@uvigo.es