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Incidence of bonamiasis in flat oyster, Ostrea edulis L., cultured in Galicia (N.W. Spain)
Aguaculture, 107 (1992) 189-192 Elsevier Science Publishers B.V., Amsterdam
189
AQUA20019
Incidence of bonamiasis in flat oyster, Ostrea edulk L., cultured in Galicia (N.W. Spain) 1. Mantes, M.J. Carballal, MC. Lopez and S.G. Mourelle Cenrro
Experimenml
t
Vdarodn.
Vilogarcfa dedrouso.
Spmn
ABSTRACT Montn. J., Carballal, M.J., Lopez, M.C. and Mourelle, S.G., 1992. Incidence of bonamiash in flat 0yw.r. Oslrea eduhr L.. cultured in Gslicia (NW. Spain ). Aqwaculture,107: 189-I 95. In this study we repon on the prevalence of Bonnmia osmae in populations of flat oyster, Oslrea cdulis L., from different origins (natural setdement, Italy, France, England), cultured in several areas of the Calician coast (“rias*’of Onigueira. Sada. Arosa and Vi@) during 1988. Whereas B. oslrew was not detects* in Iwo stocks imp&d from llaly and France with a short duration of culture in Galicia (1 -2 months), the higbesl prevalence (45.2Ohof infestation) was obtained in a stoclkfrom Italy with a cdtnre period of I2 months.
The culture of flat oyster on intertidal beds as well as on rafts has been a traditional activity in Galicia (N.W. Spain). In the early 197Os, oyster production was reduced after mortalities probably caused by Marteilia refringens (Mass& 1978; Alderman, 1979). More recently, parasitism by B. oSIreae has been associated with mortality problems (Montes and Melendez, 1987). At present, the Galician oyster industry is based mainly on the importation of flat oyster (of different sizes) with the aim of raising them in the estuaries during a variable period of time untii they reach market size. This paper reports on the prevalence of B. ostreae during 1988 in oyster stocks (natural settlement and from importation) cultured in different areas of Galicia. MATERIAL AND METHODS
We studied three oyster populations obtained by natural capture (the “rias” of Ortigueira and Arosa in Galicia, and the zone of Murcia in the MediteriaCorrespundencelo: Dr. i. Mantes,Centro Experimental de Vilaxocin, Conselleria de Pesca, Aptdo. 208, Vilagarcia de Arousa, Pontevedra, Spain.
0044-8486/92/%05.00 0 199i
Elsevier
Science Publishers B.V. AU rights reserved.
LFig. I. Location
of the
NU@EiWsRzx
“rias” and culture areas.
nean Sea) and ten imported oyster stocks (seven from Italy, two from France and one from England). Whereas the natural populations were placed in intertidal beds in the “rias” oftirtigueira and Arosa, the imported oyster stocks were cultured in rafts in the “rias” of Sada, Arosa and Vigo (Fig. 1) (Table 1). The duration of culture until the oyster reached market size was variable, ranging between 1and 23 months (Table I ). A total of 441 oysters was analysed, using standard histopathological methods. The digestive gland and gill pieces of every specimen were examined. Davidson’s solution was used as fixative and embedding was in paraffm. Sections (6 pm) were stained with Prenant’s trichrome and Harris hematoxylineosin, and examined under the light microscope for diagnosis. RESULTS
AND DISCUSSION
As shown in Table 1,the parasite E. o~reae was found in different areas of culture in Galicia, and in all stocks of oysters (natural settlement and from
191 TABLE I
Slack number
Month
Origin
Cullure area
Type of culture
April
IlalY I& Italy NatUral settlement (RiaofArosa)
Ria of Sada Ria of Vigo Ria of Vigo Ria of Arosa
Rafts 2 4 Rafts Rafts 6 Intertidal 23 beds
Natural sertlemem (Ria of Ortigueira) NatIKll settlement (Mediterranean Sea)
RiaofOrligueira
lnrerudal beds
27
Ria ofOrtigueira
Intertidal beds
4
7128
25.0
Ria Arosa Ria of Arosa Ris of Sada Ria of Vigo Ria of Arwa Ria of Sada Ria of Aroaa Ria of Vigo Ria of Arosa
3 7 6 6 12 9
1130 2129 II30 4128 14131 9128 o/30 2/30 12/30
3.3 6.9 3.3 14.3 45.2 32.1 0 6.7 40.0
M=Y May May
5
May
6
J”“e
7 8 I’ 9 IO I’ II I2 13
JUIW
Italy
July August September D”ober NovemLcr December December December
Italy Italy Italy Italy Italy France Frnnce England
of
Raits R&S Rafts Rafts Rafts Rafts R&S Rafts Rafts
Duration of ev,ture in Galicia (months)
I
6 7
No. oynen Infection infested/ No. oysters rate sampled (*)
O/32 6129 8129 4129
0 20.7 27.6 13.8
42.8
except for stocks 1 and I I. The highest indexes of infestation were obtained in stocks 13 (from England), 5 (from natural settlement) and 10 (from Italy) which showed infection rates of 40-O%, 42.8% and 45.2% respectively. The absence of B. osfreue in stocks I and I 1can be considered normal, not only because the oysters were imported from diverse culture areas Jf France and Italy where the parasite has never been found, but also due to the short time of culture in Galicia (l-2 months). In fact, when stock 1 wa!, analysed after 6 and 9 months (stocks named I ’ and I ” respectively), we detected B. osrrcae with a clear increase in prevalence from the sixth (3.3%) to the ninth (32.1%) months (Table I ). Xoi;wer, wealso detected tl;e parasite in other stocks with a short period of culture (stocks 2,6 and 7). Ttns agrees with the iindings of Tig& and Grizel ( 1984), who demonstrated that oysters free of B. osfreue placed in contaminated areas became infested after 4-5 months. importations)
192
1. MONTES El-AL.
It is noteworthy that, regardless of the origin of the oyster stocks, month of sampling or tyne of culture, the parasite was detected in all the culture areas studied. The differences in the prevalence of bonamiasis among stocks in the present study could be due to the different depths of the areas where the oysters are situated, and the density and duration ofculture which are highly variable depending on the number of importations, as well as on market requirements. Moreover, we must take into consideration the possible selective mortalities in oysters by B. ostreue before sampling, which could give rise in certain samples to lower prevalence values than the real parasitic infestation of the area.
REFERENCES Alderman, D.J., 1979. Epizootiology of Maneilia refringensin Europe. Mar. Fish. Rev., 41: 6769. Mass4 J.M., 1978. La enfermedad de la glhdula digestiva de la ostra plana (Osrrea edulis L. ) enlasrias bajas. Bol. Inst. Esp. Ocen., 251: 125-140. Monks, J. and M&ndez, ML, 1987. Dam&es SUTla pa&me de Bonamia ostrtwcher l’huitre platede Galice. tote nerd-west de I’Espagne. Aquaculture, 67: 195- 198. Tigk, G. and Grizel, H., 1984. Essai de contamination dY%frm edulis L. par Bonamio ostwm (Pichot et al., 1979) en rivitre deCrach (Morbihan). Rev. Trav. Inst. P&hesMarit., 146(4): 307-314.
189
AQUA20019
Incidence of bonamiasis in flat oyster, Ostrea edulk L., cultured in Galicia (N.W. Spain) 1. Mantes, M.J. Carballal, MC. Lopez and S.G. Mourelle Cenrro
Experimenml
t
Vdarodn.
Vilogarcfa dedrouso.
Spmn
ABSTRACT Montn. J., Carballal, M.J., Lopez, M.C. and Mourelle, S.G., 1992. Incidence of bonamiash in flat 0yw.r. Oslrea eduhr L.. cultured in Gslicia (NW. Spain ). Aqwaculture,107: 189-I 95. In this study we repon on the prevalence of Bonnmia osmae in populations of flat oyster, Oslrea cdulis L., from different origins (natural setdement, Italy, France, England), cultured in several areas of the Calician coast (“rias*’of Onigueira. Sada. Arosa and Vi@) during 1988. Whereas B. oslrew was not detects* in Iwo stocks imp&d from llaly and France with a short duration of culture in Galicia (1 -2 months), the higbesl prevalence (45.2Ohof infestation) was obtained in a stoclkfrom Italy with a cdtnre period of I2 months.
The culture of flat oyster on intertidal beds as well as on rafts has been a traditional activity in Galicia (N.W. Spain). In the early 197Os, oyster production was reduced after mortalities probably caused by Marteilia refringens (Mass& 1978; Alderman, 1979). More recently, parasitism by B. oSIreae has been associated with mortality problems (Montes and Melendez, 1987). At present, the Galician oyster industry is based mainly on the importation of flat oyster (of different sizes) with the aim of raising them in the estuaries during a variable period of time untii they reach market size. This paper reports on the prevalence of B. ostreae during 1988 in oyster stocks (natural settlement and from importation) cultured in different areas of Galicia. MATERIAL AND METHODS
We studied three oyster populations obtained by natural capture (the “rias” of Ortigueira and Arosa in Galicia, and the zone of Murcia in the MediteriaCorrespundencelo: Dr. i. Mantes,Centro Experimental de Vilaxocin, Conselleria de Pesca, Aptdo. 208, Vilagarcia de Arousa, Pontevedra, Spain.
0044-8486/92/%05.00 0 199i
Elsevier
Science Publishers B.V. AU rights reserved.
LFig. I. Location
of the
NU@EiWsRzx
“rias” and culture areas.
nean Sea) and ten imported oyster stocks (seven from Italy, two from France and one from England). Whereas the natural populations were placed in intertidal beds in the “rias” oftirtigueira and Arosa, the imported oyster stocks were cultured in rafts in the “rias” of Sada, Arosa and Vigo (Fig. 1) (Table 1). The duration of culture until the oyster reached market size was variable, ranging between 1and 23 months (Table I ). A total of 441 oysters was analysed, using standard histopathological methods. The digestive gland and gill pieces of every specimen were examined. Davidson’s solution was used as fixative and embedding was in paraffm. Sections (6 pm) were stained with Prenant’s trichrome and Harris hematoxylineosin, and examined under the light microscope for diagnosis. RESULTS
AND DISCUSSION
As shown in Table 1,the parasite E. o~reae was found in different areas of culture in Galicia, and in all stocks of oysters (natural settlement and from
191 TABLE I
Slack number
Month
Origin
Cullure area
Type of culture
April
IlalY I& Italy NatUral settlement (RiaofArosa)
Ria of Sada Ria of Vigo Ria of Vigo Ria of Arosa
Rafts 2 4 Rafts Rafts 6 Intertidal 23 beds
Natural sertlemem (Ria of Ortigueira) NatIKll settlement (Mediterranean Sea)
RiaofOrligueira
lnrerudal beds
27
Ria ofOrtigueira
Intertidal beds
4
7128
25.0
Ria Arosa Ria of Arosa Ris of Sada Ria of Vigo Ria of Arwa Ria of Sada Ria of Aroaa Ria of Vigo Ria of Arosa
3 7 6 6 12 9
1130 2129 II30 4128 14131 9128 o/30 2/30 12/30
3.3 6.9 3.3 14.3 45.2 32.1 0 6.7 40.0
M=Y May May
5
May
6
J”“e
7 8 I’ 9 IO I’ II I2 13
JUIW
Italy
July August September D”ober NovemLcr December December December
Italy Italy Italy Italy Italy France Frnnce England
of
Raits R&S Rafts Rafts Rafts Rafts R&S Rafts Rafts
Duration of ev,ture in Galicia (months)
I
6 7
No. oynen Infection infested/ No. oysters rate sampled (*)
O/32 6129 8129 4129
0 20.7 27.6 13.8
42.8
except for stocks 1 and I I. The highest indexes of infestation were obtained in stocks 13 (from England), 5 (from natural settlement) and 10 (from Italy) which showed infection rates of 40-O%, 42.8% and 45.2% respectively. The absence of B. osfreue in stocks I and I 1can be considered normal, not only because the oysters were imported from diverse culture areas Jf France and Italy where the parasite has never been found, but also due to the short time of culture in Galicia (l-2 months). In fact, when stock 1 wa!, analysed after 6 and 9 months (stocks named I ’ and I ” respectively), we detected B. osrrcae with a clear increase in prevalence from the sixth (3.3%) to the ninth (32.1%) months (Table I ). Xoi;wer, wealso detected tl;e parasite in other stocks with a short period of culture (stocks 2,6 and 7). Ttns agrees with the iindings of Tig& and Grizel ( 1984), who demonstrated that oysters free of B. osfreue placed in contaminated areas became infested after 4-5 months. importations)
192
1. MONTES El-AL.
It is noteworthy that, regardless of the origin of the oyster stocks, month of sampling or tyne of culture, the parasite was detected in all the culture areas studied. The differences in the prevalence of bonamiasis among stocks in the present study could be due to the different depths of the areas where the oysters are situated, and the density and duration ofculture which are highly variable depending on the number of importations, as well as on market requirements. Moreover, we must take into consideration the possible selective mortalities in oysters by B. ostreue before sampling, which could give rise in certain samples to lower prevalence values than the real parasitic infestation of the area.
REFERENCES Alderman, D.J., 1979. Epizootiology of Maneilia refringensin Europe. Mar. Fish. Rev., 41: 6769. Mass4 J.M., 1978. La enfermedad de la glhdula digestiva de la ostra plana (Osrrea edulis L. ) enlasrias bajas. Bol. Inst. Esp. Ocen., 251: 125-140. Monks, J. and M&ndez, ML, 1987. Dam&es SUTla pa&me de Bonamia ostrtwcher l’huitre platede Galice. tote nerd-west de I’Espagne. Aquaculture, 67: 195- 198. Tigk, G. and Grizel, H., 1984. Essai de contamination dY%frm edulis L. par Bonamio ostwm (Pichot et al., 1979) en rivitre deCrach (Morbihan). Rev. Trav. Inst. P&hesMarit., 146(4): 307-314.