RESUMO
We examined the influence of the reproductive cycle and environmental factors on variations of the condition index (CI), tissue dry mass, shell size, total lipid content, and relative percent of fatty acids in the mussel, Perna perna. Spat or juveniles were reared to commercial size (70 mm) in suspension culture in the Golfo de Cariaco, Venezuela between May and October 2004. The dry mass of soft tissues and shell, a visual assessment of gonadal status and the organism lipid profile were established every fortnight. In parallel, we measured the environmental conditions, following chlorophyll a, salinity, temperature and seston levels. After an initial decrease, the CI rose and remained high until August after which it decreased continuously until October. Total lipid values also decreased initially, after which they showed two periods of rapid recuperation and depletion, the first between May and August and the second between August and October. Similar tendencies were noted in the fatty acids, C18:3n-3, C18:4n-3 and C22:6n-3. Correlation analysis found no significant relationships between environmental parameters and the variations in total lipids. However, significant correlations were noted between fatty acids and specific environmental parameters. In particular, temperature was inversely correlated with C14:0, C16:1n-7, C18:0, C18:1n-9 and 20:5n-3. Chlorophyll a was positively correlated with C14:0, C16:1n-7, C18:1n-7, C18:4n-3 and 20:4n-6. On the other hand, gametogenesis had an effect on C14:0, C16:1n-7, C18:1n-9 and C18:1n-7, while spawned and gonadal regression states had an effect on fatty acid 20:4n-6. Temperature and chlorophyll a levels strongly influenced the proportion of mussels spawning, suggesting that their influence upon lipid composition may be secondary to their impact upon reproduction. Despite the thermal stability of this tropical system, the lipid composition of mussels changed markedly during the study, reflecting the central role of diet and reproductive investment upon lipid composition.
Assuntos
Aquicultura/métodos , Ácidos Graxos/metabolismo , Perna (Organismo)/metabolismo , Animais , Meio Ambiente , Ácidos Graxos/análise , Perna (Organismo)/química , Perna (Organismo)/crescimento & desenvolvimento , Perna (Organismo)/fisiologia , Reprodução , Sobrevida , VenezuelaRESUMO
Se evaluó la abundancia de juveniles de Pinna carnea, el crecimiento y su relación con factores ambientales en cultivo suspendido en Turpialito, Golfo de Cariaco, Venezuela. La abundancia se determinó usando colectores suspendidos a 8 m de profundidad en "long line" durante 16 meses. El crecimiento se determinó en cestas de cultivo en un "long line" a 8 m de profundidad y la temperatura y disponibilidad de alimento fueron registrados durante 15 meses. Todos los componentes del cuerpo se incrementaron rápidamente durante los primeros cuatro-cinco meses, posteriormente la masa de todos los tejidos somáticos muestran disminución y gran variabilidad en el crecimiento, coincidiendo con el primer período de desove, lo cual sugiere una influencia negativa de la gametogénesis en el crecimiento somático. Un análisis de regresión múltiple indicó una alta relación del crecimiento y la disponibilidad de alimento. Aunque se determinó una adecuada abundancia de juveniles (máximo 80 por colector-30x60 cm), la recolecta no fue continua. Esta característica, junto con la alta variabilidad del crecimiento y la influencia negativa de los factores ambientales en períodos desfavorables, además de la obtención de músculos de talla comercial en 14 meses, sugieren que la especie no es apropiada para la producción de músculos. Sin embargo, la elevada masa total de sus tejidos comestibles (21 g) y la alta sobrevivencia (96%), sugieren a P. carnea para ser cultivada.
Assuntos
Animais , Bivalves , Pesqueiros , Água do Mar , Oceano Atlântico , Alimentos , Densidade Demográfica , Análise de Regressão , Estações do Ano , VenezuelaRESUMO
The effect of culture density on growth and survival of juveniles was studied in the scallop Lyropecten nodosus with intermediate hanging cultures in Golfo de Cariaco, Sucre state, Venezuela, from December 1993 to July 1994. Six spat-densities (7, 15, 30, 60, 125 and 250 scallops/nets) were evaluated. The initial shell height and dry mass tissue were 9.4 +/- 0.18 mm and 0.007 +/- 0.0026 g, respectively. The specimens were placed into pearl nets and suspended in a long line at 8 m depth. Growth patterns of somatic tissue were similar, but with different magnitudes and inverse proportionality to culture density. No effect of density was observed on survival. These results suggest that intraspecific competition of cultivated scallops cause stress, which affects growth but not survival. We suggest as strategy for the management of culture density, successive density reductions, to obtain in a six months culture (intermediate culture) specimens of 50 mm in shell height in order to start the final culture period.
Assuntos
Pesqueiros , Moluscos/crescimento & desenvolvimento , Água do Mar , Animais , Densidade Demográfica , VenezuelaRESUMO
We quantified the abundance of juvenile Pinna carnea at Turpialito, Golfo de Cariaco, Venezuela, using collectors suspended at 8 m depth for 16 months and then evaluated their subsequent growth in suspended enclosures over 14 months in relation to concurrent measures of temperature and planktontonic food availability. All body components showed a rapid increase during the first four-five months. There was a decrease in somatic tissue mass and great variability in growth coincident at first spawning, suggesting a negative effect of gonadal production on somatic growth. A multiple regression analysis indicated a strong relationship between tissue growth and food availability as measured by organic sestonic matter. Although we determinated an adequated spat abundance for culture activities (80 spat per collector-30 x 60 cm), spat collection was limited, mainly from February through April. In addition to high variability in growth and negative influence of environmental factors during unfavorable periods, the muscles production required in 14 months, suggesting that P. carnea is not appropriate for commercial production of muscle. However, the high weight of all edible tissues mass attained (21 g) and the high survival rate in all experimentation (> 96%) suggests that P. carnea is fit for aquaculture.
Assuntos
Bivalves/crescimento & desenvolvimento , Pesqueiros , Água do Mar , Animais , Oceano Atlântico , Alimentos , Densidade Demográfica , Análise de Regressão , Estações do Ano , VenezuelaRESUMO
The incidence of bacteria as etiological agents of diseases in larvae of bivalve mollusks, is well documented in the literature. In this study, a series of test were performed to identify and estimate pathogenic level of marine bacteria isolated during an epizootic in a larval culture system of the tropical scallop Euvola ziczac. Such bacteria was identified as Pseudomonas sp. belonging to the group alcaligenes. The bacterium produced not only lethal effects on the scallop larvae through infection (invasive action), but also a possible pathogenic activity through endotoxins associated to bacterial cell-wall. In addition, it is possible that the isolated bacteria could act as a pathogen with members of the genus Vibrio, which was also present during the epizootic outbreak in the culture system. Susceptibility of Pseudomonas sp. to commercial antibiotics was remarkable.
