SEASONAL VARIATION OF THE GLOBAL CHEMICAL COMPOSITION OF FISH: ANNULAR SEA BREAM DIPLODUS ANNULARIS (L, 1758)

Abstract Seasonal variation of the global chemical composition of the annular sea bream species of the coastal catch fish of the Gulf of Gabes (Tunisia) was studied between October 2007 and September 2008. The period of reproduction of Diplodus annularis occurs from April to June. This sexual maturity (RGS, RHS) is in strong correlation with the fat content. The fat content is negatively correlated with moisture content R= 0.83, P<10 ). The variance analysis of moisture, protein, fat and ash in the whole muscle shows that only the factor months has significant effect on the muscles chemical composition (P<10 )

Estudio taxonómico de Squalus megalops (Macleay, 1881) y Squalus blainvillei (Risso, 1827) (Chondrichthyes: Squalidae) en aguas de Túnez (Mediterráneo central)

Two species of spurdog of the genus Squalus occur in the Gulf of Gabès (southern Tunisia, central Mediterranean): the longnose spurdog Squalus blainvillei (Risso, 1827) and a short-snout spurdog of the Squalus megalops-cubensis group. Morphometric and meristic data as well as a genetic analyses (DNA inter-simple sequence repeat markers and molecular barcoding methods) support the assignation of this short-snout spurdog to Squalus megalops (Macleay, 1881). Squalus megalops occurs commonly in temperate and tropical Australian waters, and is also thought to occur in the eastern Atlantic, southern Indian Ocean and western North Pacific although these records need to be confirmed. Our study confirms that it occurs in the Mediterranean Sea. Populations of both S. blainvillei and S. megalops are described based on Tunisian material.En el golfo de Gabès (sur de Túnez, Mediterráneo central) se encuentran dos especies del género Squalus: el galludo Squalus blainvillei (Risso, 1827) y otra de morro más corto perteneciente al grupo Squalus megalops-cubensis. Los datos morfométricos y merísticos junto con el análisis genético (ADN Inter Simple Sequence Repeats markers y métodos moleculares Barcoding) apoyan la identificación de esta última especie como Squalus megalops (Macleay, 1881). Squalus megalops se encuentra en aguas australianas templadas y tropicales, y se piensa que habita también en el Atlántico este, en el océano Índico sur y en el Pacífico noroccidental, aunque estos registros deben ser confirmados. Nuestro estudio confirma su presencia en el mar Mediterráneo. La descripción tanto de S. blainvillei como de S. megalops está basada en especímenes capturados en aguas tunecinas

Biología de la bacoreta Euthynnus alletteratus del Golfo de Gabes, Sur de Túnez (Mar Mediterráneo Central)

Biological features known as sex-ratio, Gonad-Somatic Index (GSI), Hepatic-Somatic Index (HSI) and size at first sexual maturity, and the length-weight relationships (LWR) were studied in little tunny, Euthynnus alletteratus, caught in the Gulf of Gabes (Southern Tunisia). A total of 397 little tunny (244 females and 153 males) were analysed. Fish length ranged between 36.7 and 97.8 cm, average 52.29 ± 5.87 cm. Samples were monthly fished from January 2008 to December 2009. Sixty one percent of the specimens caught were females. The high GSI suggest that the spawning period runs from June to September. Fish in spawning condition are to be observed in August since GSI reaches the peak in July. Negative allometry was found in little tunny. Fork length at first sexual maturity in males (42.8 cm) was smaller than in females (44.8 cm).Se describen algunos parámetros biológicos de la bacoreta Euthynnus alletteratus en el Golfo de Gabes (sur de Túnez), tales como la proporción de sexos, el Índice Gonado-Somático (IGS), el Índice Hepato-Somático (IHS), la longitud de primera madurez sexual, y la relación longitud-peso. Se analizó un total de 397 specímenes (244 hembras y 153 machos) entre los 36,7 y 97,8 cm de longitud, con un promedio 52,29 ± 5,87 cm. Las muestras se recolectaron mensualmente, entre enero de 2008 y diciembre de 2009. El 61% de los ejemplares fueron hembras. El periodo de desove se extiende de junio a septiembre, calculado a partir de los altos valores de IGS. Las relaciones longitud-peso revelaron que la bacoreta presenta una alometría negativa. La longitud promedio de primera madurez de las muestras tomadas en el Golfo de Gabes fue de 44,8 cm de longitud de horquilla para las hembras y 42,8 cm para los machos

Rearing of Fabrea salina Henneguy (Ciliophora, Heterotrichida) with three unicellular feeds

International audienceThe growth rate of the ciliate Fabrea salina was studied in batch cultures in the presence of three feeds, tested separately from each other: the Prymnesiophyceae, Isochrysis galbana obtained from pure culture, the Chlorophyceae Dunaliella salina, and the commercially available yeast Saccharomyces cerevisiae. F. salina, and D. salina were harvested below the surface from the first evaporation pond and the crystallizer pond, respectively in multi-pond salterns (Sfax, Tunisia). The highest density of Fabrea was recorded with I. galbana (26 ind ml−1). However, the greatest length (243 μm) was recorded with Fabrea fed with D. salina. The lowest density, length and biovolume values were recorded with Fabrea fed with S. cerevisiae. The ANOVA test showed that density (F = 18, d.f. = 57), length (F = 33, d.f. = 57), and biovolume (F = 19, d.f. = 57) of Fabrea fed with yeast were significantly different (p <0.001) from those when Fabrea was fed with D. salina and I. galbana. The ciliate Fabrea encountered in the Sfax saltern (Tunisia) might be a valuable food source for Tunisian marine fish hatcheries

Trophic condition of seven mediterranean freshwater reservoirs : Environmental factors and zooplanktonic community

International audienc

Phytoplankton : Ecology, Aquaculture and Blooms

International audienc

Abundance and biomass of prokaryotic and eukaryotic microorganisms coupled with environmental factors in an arid multi-pond solar saltern (Sfax, Tunisia)

International audienceThe distribution of abundance and biomass of prokaryotes, flagellates, ciliates and phytoplankton, were studied in five ponds of increasing salinity in the Sfax solar saltern (Tunisia) coupled with environmental factors. The results showed that abundance of eukaryotic microorganisms decreased with increasing salinity of the ponds whereas prokaryotes (heterotrophic bacteria and Archaea) were abundant in the hyper-saline ponds. Phototrophic picoplankton was found in a large range of salinity values (70 and 200‰). Phototrophic non-flagellated nanoplankton which dominated in the first sampled pond was substituted by phototrophic flagellated nanoplankton in the other ponds. Heterotrophic nanoplankton dominated in the crystallizer pond but its quantitative importance declined in the less saline ponds. Diatoms and dinoflagellates were the major contributors to phytoplankton abundance in the first ponds (.90% of total abundance). Ciliated protozoa were found in all the ponds except in the crystallizer in which prokaryotes proliferated. Oligotrichida and Heterotrichida were the most abundant ciliate groups. Overall, species richness decreased with salinity gradient. We propose a simplified diagram of the Sfax saltern's food web showing the dominant role of the microbial loop along the salinity gradient

VARIATION DES TENEURS EN ELEMENTS MINERAUX DANS LE MUSCLE DE QUATRE ESPECES DE POISSONS

Abstract Les teneurs de neuf éléments minéraux (K, Mg, Na, Ca, Fe, Cd, Pb, Zn et Cu) dans le muscle dequatre espèces de poissons de la pêche côtière du golfe de Gabès (le sparaillon Diplodus annularis, le gobie Zosterisessor ophiocephalus, le mulet Liza aurata et le saurel caranx rhonchus) ont été déterminés dans le mois d&apos;avril 2008. La variation des teneurs en minéraux en fonction du sexe de poissons et des espèces a été examinée. Une grande variabilité entre les deux sexes est observée pour les éléments majeurs (K, Mg, Na, Ca). Pour les éléments mineurs (Cu, Cd et Pb) peu de variations

Age, growth, longevity, mortality and reproductive biology of Dipturus oxyrinchus, (Chondrichthyes: Rajidae) off the Gulf of Gabes (Southern Tunisia, central Mediterranean)

WOS:000353595500015The age, growth, longevity, mortality and reproductive parameters were estimated for Dipturus oxyrinchus from the Gulf of Gabes (Southern Tunisia, central Mediterranean Sea), collected monthly during 2007 from commercial fisheries. The present study provides the first data on age and growth of this species in Tunisian waters, as well as additional data on its reproduction. A total of 240 females (16.5-105 cm total length (T-L)) and 280 males (15.5-95 cm T-L) were examined to study the reproductive cycle. A subsample of 285 specimens (175 females and 110 males, ranging from 15.5 to 105 cm T-L) were analysed to study the age and growth. The oldest female in this study was 25 yr and 105 cm T-L, whereas the oldest male was 22 yr and 95 cm. The annual deposition of growth bands was verified by marginal increment and edge analysis. The von Bertalanffy growth parameters were L-infinity = 123.9 +/- 2.56 cm, K = 0.08 +/- 0.004 yr(-1) and t(0) = -1.26 +/- 0.04 10(-1) yr for females and L-infinity = 102.1 +/- 3.23 cm, K = 0.12 +/- 0.007 10(-3) yr(-1) and t(0) = -1.18 +/- 0.03 10(-1) yr for males. Growth was not significantly different between sexes. The maturity size was 72.05 cm for males and 82.1 cm for females. The maturity age was estimated to be 11.95 and 13.96 years, respectively, for males and females. Size and age at maturity were not significantly different between sexes. The estimated longevity was 26.18 and 38.84 yr for males and females, respectively. Based on life history parameters, natural mortality was estimated at 0.53 yr(-1) for females and 0.41 yr(-1) for males