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The effect of winter period, gametogenesis and spawning on the calorific content of soft parts in Mytilus chilensis
Aquaculture, 32 (1983) 419-422 Elsevier Science Publishers B.V., Amsterdam
419 - Printed
in The Netherlands
Short Communication THE EFFECT OF WINTER PERIOD, GAMETOGENESIS AND SPAWNING ON THE CALORIFIC CONTENT OF SOFT PARTS IN MYTILUS CHILENSIS
O.R. CHAPARRO
and J.E. WINTER
Centro de Inuestigaciones Marinas, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia (Chile) (Accepted
1 September
1982)
ABSTRACT Chaparro, O.R. and Winter, J.E., 1983. The effects of winter period, gametogenesis and spawning on the calorific content of soft parts in Mytilus chilensis. Aquaculture, 32 : 419422. Calorific values of the soft parts of Mytilus chilensis were determined monthly over a l-year period. The fluctuations in the calorific values of the meat of raft-cultured mussels reflected (a) poor food conditions during winter, (b) accumulation of high energetic compounds in the gonads during gametogenesis, and (c) the expulsion of high energy material in the form of gametes during the spawning period. The highest calorific values were obtained in September-October, just before spawning (November). Recommendations are made for harvesting and marketing these mussels in Chile.
INTRODUCTION
Preliminary studies carried out by Duarte et al. (1980) on the Chilean mussel, Mytilus chilensis, revealed that mussels from natural banks showed typical seasonal variations in the calorific content of their soft parts due to low food conditions during the winter, and the processes of gametogenesis and spawning during spring. As M. chilensis is important to the development of aquaculture in Chile, the seasonal fluctuations in the calorific content of the meat should be used to indicate the optimal period of the year for harvest and marketing. As most mussels marketed in Chile are cultured from rafts, the purpose of the present investigation is to quantify the fluctuations in the calorific content of raft-cultured mussels to assess the importance of such changes to culture practices, and to establish the optimal time for harvest and marketing. MATERIAL
AND METHODS
Specimens
of Mytilus chilensis were collected
0044-8486/83/$03.00
0 1983 Elsevier
Science
Publishers
from culture B.V
rafts in
420
Yaldad Bay in the South of Chile (lat. 43”08’S; long. 73”44’W). They were divided into three experimental size classes, of 22.0 mm (size class I), 31.5 mm (size class II) and 61.5 mm (size class III) average shell length, respectively. The three size classes were kept separately in suspended culture from May 1979 to February 1980. Each month, 20 to 30 individuals from each size class were analysed in the laboratory to determine the calorific content of their soft parts. The whole soft parts of each size class were dried (90°C 24 h), ground, homogenized and pelletized. The calorific determinations were made in a Parr adiabatic oxygen bomb calorimeter, as described by Duarte et al. (1980). Replicate values of each size class were averaged and expressed in Cal/g dry meat. RESULTS
AND DISCUSSION
In general, the results for the three size classes were similar (Fig. lA, B and C). Low calorific values were recorded for all size classes during winter. From September onward there was a rapid increase due to gametogenesis Cal/g
dry moot
ml/g
5500
1979
dry
moot
1
C
Size
class
III
1980
Fig. 1. Mytilus chilensis. Seasonal fluctuations in the calorific content of the meat of raft-cultured mussels from Yaldad Bay (A-C) and of natural bank mussels from Valdivia estuary (D; after Duarte et al., 1980). Arrows indicate the beginning of spawning.
421
which reached its maximum at the end of October. In the early summer months, November-December, the calorific content of the meat again decreased rapidly due to spawning activity. This was also reflected by the condition index (dry meat weight, in g, expressed as percentage of inner shell volume, in ml) which coincides with the seasonal fluctuations of the calorific values for all size classes tested. The low calorific values during winter are the result of the utilization of reserves by the mussels due to the poor food conditions during this season (Taylor and Venn, 1979). Gametogenesis produced significant changes in the biochemical components of the gonads (Taylor and Venn, 1979;Tarifeno and Zamora, 1981). This in turn affected the calorific content of the soft parts of the mussels. Gabbott (1976) showed that these changes were associated with an increase in the protein and lipid content of the gonads. The highest calorific values recorded for M. chilensis by Duarte et al. (1980) were obtained just before spawning. Thus, the fluctuations of the calorific content depend principally on the formation and liberation of the gametes (Tyler, 1973). The spawning period noted during the present investigation (November to March) confirmed the observations by Winter et al. (1982) for M. chilensis from southern Chile. The relatively long spawning period of this species explains the low calorific values from November to February. The calorific levels of raft-cultured mussels from Yaldad Bay were compared with those from natural banks in Valdivia estuary recorded by Duarte et al. (1980). Both populations were influenced similarly by the poor food conditions during winter, the processes of gametogenesis, and the spawning activity (Fig. 1D). The difference in time of the two calorific curves was probably due to the local variations in environmental conditions (for example, food availability: Chaparro, 1981; Winter et al., 1982) rather than intrinsic factors of the two different populations. For successful marketing, high calorific values combined with high meat content are important. For raft-cultured mussels, the best marketing conditions (principally for canned products) occur during September--October; for natural populations of mussels, condition is the best in October and November. However, as the optimal marketing condition coincides with the optimal period of reproduction, it is important to retain large stocks of adult mussels to continue new seed production. ACKNOWLEDGEMENTS
The authors reviewing the C-77-14-2 and Desarrollo de
are grateful to Prof. C. Moreno and Prof. C. Varela for manuscript. The present work was supported by grants S-81-09 made available by the Direction de Investigation la Universidad Austral de Chile, Valdivia.
y
422 REFERENCES Chaparro, O.R., 1981. Fijacibn, crecimiento, desprendimiento y mortalidad de Mytilus chilensis Hup& 1854, en tres mitiliculturas de Chiloe (Yaldad, Huildad y Tubildad), X RegiBn. Tesis Biblogo Marino, Universidad de ConcepciBn, Chile, 70 pp. Duarte, W.E., Jara, F. and Moreno, C.A., 1980. Contenido energetic0 de algunos invertebrados bent6nicos de la costa de Chile y fluctuaci6n anual de My tilirs chilensis Hupd 1854. Bolm. Inst. Oceanogr., S. Paulo, 29 (2): 273-278. Gabbott, P.A., 1976. Energy metabolism. In: B.L. Bayne (Editor), Marine Mussels. Cambridge University Press, Cambridge; pp. 293-355. Tarifefio, E. and Zamora, N., 1981. Variacik estacional de 10s contenidos de carbohidratos, lcpidos y proteinas en la macha Mesodesma donacium (Bivalvia, Mesodesmatidae). Jornadas de Ciencias de1 Mar, Chile: 77 (abstract). Taylor, A.C. and Venn, T.J., 1979. Seasonal variation in weight and biochemical composition of the tissues of the queen scallop, Chlamys opercularis, from the Clyde sea area. J. Mar. Biol. Assoc. U.K., 59: 605-621. Tyler, A.V., 1973. Calorific values of some North Atlantic invertebrates. Mar. Biol., 19: 258-261. Winter, J., Navarro, J., RomPn, C. and Chaparro, O., 1982. Programa de explotacidn de mitaidos. Investigacibn cientifica bhsica, II parte. A project report of the Corpora&on de Foment0 de la ProducciBn, Chile, 312 pp.
419 - Printed
in The Netherlands
Short Communication THE EFFECT OF WINTER PERIOD, GAMETOGENESIS AND SPAWNING ON THE CALORIFIC CONTENT OF SOFT PARTS IN MYTILUS CHILENSIS
O.R. CHAPARRO
and J.E. WINTER
Centro de Inuestigaciones Marinas, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia (Chile) (Accepted
1 September
1982)
ABSTRACT Chaparro, O.R. and Winter, J.E., 1983. The effects of winter period, gametogenesis and spawning on the calorific content of soft parts in Mytilus chilensis. Aquaculture, 32 : 419422. Calorific values of the soft parts of Mytilus chilensis were determined monthly over a l-year period. The fluctuations in the calorific values of the meat of raft-cultured mussels reflected (a) poor food conditions during winter, (b) accumulation of high energetic compounds in the gonads during gametogenesis, and (c) the expulsion of high energy material in the form of gametes during the spawning period. The highest calorific values were obtained in September-October, just before spawning (November). Recommendations are made for harvesting and marketing these mussels in Chile.
INTRODUCTION
Preliminary studies carried out by Duarte et al. (1980) on the Chilean mussel, Mytilus chilensis, revealed that mussels from natural banks showed typical seasonal variations in the calorific content of their soft parts due to low food conditions during the winter, and the processes of gametogenesis and spawning during spring. As M. chilensis is important to the development of aquaculture in Chile, the seasonal fluctuations in the calorific content of the meat should be used to indicate the optimal period of the year for harvest and marketing. As most mussels marketed in Chile are cultured from rafts, the purpose of the present investigation is to quantify the fluctuations in the calorific content of raft-cultured mussels to assess the importance of such changes to culture practices, and to establish the optimal time for harvest and marketing. MATERIAL
AND METHODS
Specimens
of Mytilus chilensis were collected
0044-8486/83/$03.00
0 1983 Elsevier
Science
Publishers
from culture B.V
rafts in
420
Yaldad Bay in the South of Chile (lat. 43”08’S; long. 73”44’W). They were divided into three experimental size classes, of 22.0 mm (size class I), 31.5 mm (size class II) and 61.5 mm (size class III) average shell length, respectively. The three size classes were kept separately in suspended culture from May 1979 to February 1980. Each month, 20 to 30 individuals from each size class were analysed in the laboratory to determine the calorific content of their soft parts. The whole soft parts of each size class were dried (90°C 24 h), ground, homogenized and pelletized. The calorific determinations were made in a Parr adiabatic oxygen bomb calorimeter, as described by Duarte et al. (1980). Replicate values of each size class were averaged and expressed in Cal/g dry meat. RESULTS
AND DISCUSSION
In general, the results for the three size classes were similar (Fig. lA, B and C). Low calorific values were recorded for all size classes during winter. From September onward there was a rapid increase due to gametogenesis Cal/g
dry moot
ml/g
5500
1979
dry
moot
1
C
Size
class
III
1980
Fig. 1. Mytilus chilensis. Seasonal fluctuations in the calorific content of the meat of raft-cultured mussels from Yaldad Bay (A-C) and of natural bank mussels from Valdivia estuary (D; after Duarte et al., 1980). Arrows indicate the beginning of spawning.
421
which reached its maximum at the end of October. In the early summer months, November-December, the calorific content of the meat again decreased rapidly due to spawning activity. This was also reflected by the condition index (dry meat weight, in g, expressed as percentage of inner shell volume, in ml) which coincides with the seasonal fluctuations of the calorific values for all size classes tested. The low calorific values during winter are the result of the utilization of reserves by the mussels due to the poor food conditions during this season (Taylor and Venn, 1979). Gametogenesis produced significant changes in the biochemical components of the gonads (Taylor and Venn, 1979;Tarifeno and Zamora, 1981). This in turn affected the calorific content of the soft parts of the mussels. Gabbott (1976) showed that these changes were associated with an increase in the protein and lipid content of the gonads. The highest calorific values recorded for M. chilensis by Duarte et al. (1980) were obtained just before spawning. Thus, the fluctuations of the calorific content depend principally on the formation and liberation of the gametes (Tyler, 1973). The spawning period noted during the present investigation (November to March) confirmed the observations by Winter et al. (1982) for M. chilensis from southern Chile. The relatively long spawning period of this species explains the low calorific values from November to February. The calorific levels of raft-cultured mussels from Yaldad Bay were compared with those from natural banks in Valdivia estuary recorded by Duarte et al. (1980). Both populations were influenced similarly by the poor food conditions during winter, the processes of gametogenesis, and the spawning activity (Fig. 1D). The difference in time of the two calorific curves was probably due to the local variations in environmental conditions (for example, food availability: Chaparro, 1981; Winter et al., 1982) rather than intrinsic factors of the two different populations. For successful marketing, high calorific values combined with high meat content are important. For raft-cultured mussels, the best marketing conditions (principally for canned products) occur during September--October; for natural populations of mussels, condition is the best in October and November. However, as the optimal marketing condition coincides with the optimal period of reproduction, it is important to retain large stocks of adult mussels to continue new seed production. ACKNOWLEDGEMENTS
The authors reviewing the C-77-14-2 and Desarrollo de
are grateful to Prof. C. Moreno and Prof. C. Varela for manuscript. The present work was supported by grants S-81-09 made available by the Direction de Investigation la Universidad Austral de Chile, Valdivia.
y
422 REFERENCES Chaparro, O.R., 1981. Fijacibn, crecimiento, desprendimiento y mortalidad de Mytilus chilensis Hup& 1854, en tres mitiliculturas de Chiloe (Yaldad, Huildad y Tubildad), X RegiBn. Tesis Biblogo Marino, Universidad de ConcepciBn, Chile, 70 pp. Duarte, W.E., Jara, F. and Moreno, C.A., 1980. Contenido energetic0 de algunos invertebrados bent6nicos de la costa de Chile y fluctuaci6n anual de My tilirs chilensis Hupd 1854. Bolm. Inst. Oceanogr., S. Paulo, 29 (2): 273-278. Gabbott, P.A., 1976. Energy metabolism. In: B.L. Bayne (Editor), Marine Mussels. Cambridge University Press, Cambridge; pp. 293-355. Tarifefio, E. and Zamora, N., 1981. Variacik estacional de 10s contenidos de carbohidratos, lcpidos y proteinas en la macha Mesodesma donacium (Bivalvia, Mesodesmatidae). Jornadas de Ciencias de1 Mar, Chile: 77 (abstract). Taylor, A.C. and Venn, T.J., 1979. Seasonal variation in weight and biochemical composition of the tissues of the queen scallop, Chlamys opercularis, from the Clyde sea area. J. Mar. Biol. Assoc. U.K., 59: 605-621. Tyler, A.V., 1973. Calorific values of some North Atlantic invertebrates. Mar. Biol., 19: 258-261. Winter, J., Navarro, J., RomPn, C. and Chaparro, O., 1982. Programa de explotacidn de mitaidos. Investigacibn cientifica bhsica, II parte. A project report of the Corpora&on de Foment0 de la ProducciBn, Chile, 312 pp.