Summary:The reproductive cycle of the flat oyster, Ostrea edulis Linnaeus, 1758, in Homa Lagoon, Izmir Bay, Turkey was examined from August 2008 to July 2009. Gonad samples were analysed histologically in order to determine the sex ratio and gonad development stage. Overall, the sex ratio was recorded as 2.2% female, 42.6% male, 37% hermaphrodite and 17.9% inactive. Glycogen content showed considerable variations between August and February, but decreased gradually thereafter. However, glycogen did not directly affect the reproductive cycle. Total lipid content was positively correlated with temperature and inversely correlated with salinity. In addition, this parameter was influenced by the reproductive activity, which is correlated with the fluctuation of the condition index and gonad index (P<0.05). However, the relationship between the protein index and the gonad index was negative (P<0.05). The results of this study showed that protein was the major energy resource. The condition index varied between 2.69±0.91 (February) and 12.29±1.45 (April) during the year. With respect to meat yield, oyster quality changed from "fine" to "special", except in December and February.Keywords: flat oyster; Ostrea edulis; reproductive cycle; biochemical composition; Aegean Sea; Homa Lagoon.Variación estacional de la actividad reproductiva y de la composición bioquímica de ostra plana (Ostrea edulis) en Homa Lagoon, bahía de Izmir, Turquía Resumen: El ciclo reproductivo de la ostra plana, Ostrea edulis Linnaeus, 1758, en Homa Lagoon, Bahía de Izmir, Turquía, fue examinado entre agosto de 2008 y julio de 2009. Las gónadas se analizaron histológicamente para determinar la proporción de sexos y su estado de desarrollo. La proporción de sexos encontrada fue 2.2% hembras, 42.6% machos, 37% hermafroditas y 17.9% inactivos. El contenido de glucógeno mostró considerables variaciones entre agosto y febrero, pero después de estos meses se produjo un aumento gradual. Sin embargo el glucógeno no afectó directamente el ciclo reproductivo. El contenido total de lípidos se correlacionó positivamente con la temperatura e inversamente con la salinidad. Además, este parámetro estuvo influenciado por la actividad reproductiva, que se correlaciona con la fluctuación del índice de condición y del índice gonadal (P<0,05). Sin embargo la relación entre el índice de proteí-na y el índice gonadal fue negativa (P<0,05). Los resultados de este estudio mostraron que la proteína era la principal fuente de energía. El índice de condición varió entre 2.69±0.91 (febrero) y 12.29±1.45 (abril) durante el año. En lo que respecta a la producción de carne, la calidad de las ostras pasó de "fine" to "special", excepto en diciembre y febrero.

Several bivalve species produce byssus threads to provide attachment to substrates, with mechanical properties highly variable among species. Here, we examined the distal section of byssal threads produced by a range of bivalve species (Mytilus edulis, Mytilus trossulus, Mytilus galloprovincialis, Mytilus californianus, Pinna nobilis, Perna perna, Xenostrobus securis, Brachidontes solisianus and Isognomon bicolor) collected from different nearshore environments. Morphological and mechanical properties were measured, and biochemical analyses were performed. Multivariate redundancy analyses on mechanical properties revealed that byssal threads of M. californianus, M. galloprovincialis and P. nobilis have very distinct mechanical behaviours compared with the remaining species. Extensibility, strength and force were the main variables separating these species groups, which were highest for M. californianus and lowest for P. nobilis. Furthermore, the analysis of the amino acid composition revealed that I. bicolor and P. nobilis threads are significantly different from the other species, suggesting a different underlying structural strategy. Determination of metal contents showed that the individual concentration of inorganic elements varies, but that the dominant elements are conserved between species. Altogether, this bivalve species comparison suggests some molecular bases for the biomechanical characteristics of byssal fibres that may reflect phylogenetic limitations.

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The growth and mortality rate of different size of mussels, Mytilus galloprovincialis, were compared in Mersin bay, Izmir. Mussel sampling was performed on a monthly basis over 1 year, together with hyrobiological parameters. Water temperature, salinity, chlorophyll a, total particulate matter (TPM) and particulate organic carbon (POC) were determined. Average chlorophyll a, TPM and POC values were 3.88±1.62 μg L−1, 13.12±3.68 mg L−1 and 252±121.89 μg L−1 respectively. Initial mean lengths of mussels for each size group were 10 mm (9.91±0.25 mm), 20 mm (20.14±0.29 mm), 30 mm (30.66±0.21 mm), 40 mm (40.14±0.21 mm), 50 mm (50.62±0.21 mm), 60 mm (59.77±0.21 mm) and 70 mm (69.47±0.62 mm). Maximum growth in length occurred during the spring–summer months. The annual length increments of mussel size groups were 46.22, 41.42, 30.3, 28.03, 20.63, 16.34 and 12.03 mm from small to large size groups respectively. Small mussels grew faster than large mussels and reached commercial size at the same time. Mortality was <5% for all groups at the end of the experiment.

The carpet shell clam (Tapes decussatus Linnaeus, 1758) is a candidate species for aquaculture development in Turkish waters. Our study aimed to assess the efficiency of three different methods (i.e., net, box and fenced ground) to maximize clam production. Two different net materials (hard plastic net and polyamide net) were tested in the net method trials. Conducted over 1 year between October 2001 and October 2002, an initial calibrated clam population, characterized by a 26.25 ± 0.035 mm shell length and 3.85 ± 0.06 g total wet weight was sampled on a monthly basis to carry out the experiments. By the end of the rearing cycle, clams reached 34.13 ± 0.38 mm and 9.09 ± 0.27 g in shell length and total wet weight, respectively. Significant differences in shell length and total wet weight among culture methods (P < 0.05) were reported. Both maximum growth and total wet weight, as well as survival rate (64%) were obtained using the hard plastic net method. Those overall results were likely due to both limited algae accumulation and crab predation when using hard plastic net. Therefore, this method appears the most suitable to develop further larger experimental clam aquaculture trials. Additional studies required to develop clam culture in Turkish waters are discussed.