Spatial and Temporal Structures of the Macrozoobenthos from the Intertidal Zone of the Kneiss Islands (Central Mediterranean Sea)

The present study analyses the spatio-temporal variability of the macrozoobenthos from the intertidal zone of the Kneiss Islands (Gulf of Gabès, Tunisia). Samples were collected once from 34 stations, while seasonal variations were studied by sampling four times at 12 stations over the period 2013-2014. A total of 159 macrobenthos taxa associated with intertidal Zostera noltei beds are identified from the 34 stations, with a taxonomic dominance of crustaceans (32%), molluscs (29%) and annelids (27%). Abundance varies from 9244 to 36,844 ind·m-2 with a mean value of 14,346 ind·m-2. Analysis of the trophic structure shows that the majority of stations are strongly represented by carnivores (41%), followed by the non-selective deposit feeders (16%). Cluster analysis and multidimensional scaling allow identification of three main benthic assemblages based on species abundance, corresponding to different sediment types and organic matter contents. The seasonal variability in abundance, diversity and community structure is mainly due to spring and summer recruitment. The biotic indices (i.e. AMBI, BO2A and BENTIX) show that the intertidal area of Kneiss Islands exhibits a good ecological status.

Metazoan Parasites of the Mediterranean Garfish <i>Belone belone gracilis</i>(Teleostei: Belonidae) as a Tool for Stock Discrimination

The aim of the present study was to provide a current survey of metazoan parasites of the Mediterranean garfish Belone belone gracilis Lowe, 1839 off Tunisian coast and their potential use as biological tags for discriminate stocks. Parasitological analysis of 453 specimens of B. b. gracilis along the eastern Tunisian coast revealed the presence of ten species of metazoan parasites: one monogenean Axine belones Abildgaard, 1794;four digeneansLecithostaphylus retroflexus (Molin, 1859), Tergestia acanthocephala (Stossich, 1887) Stossich, 1899, Aponurus laguncula Looss, 1907 and Condylocotyla pilodora(metacercaria) Pearson et Prévot, 1985;one copepod Bomolochus bellonesBurmeister, 1835;two isopods Irona nana Schioedte et Meinert, 1884 andNerocila orbignyi (Guérin-Méneville, 1832);1 acanthocephalan Telosentis exiguus (Von Linstow, 1901) and one nematod Anisakid larvae. Discriminant analysis using parasites as biological tags, allowed identifying two stocks ofB. b. gracilis. Digenea L. retroflexus, A. laguncula and Anisakid larvae were the most important species in determining the position of sampled fishes from the central coast off Tunisia. Metacercaria C. pilodora characterized specimens from the Southern coast off Tunisia. These results were corroborated by comparing parameters of prevalence and mean abundance between zones. Discriminant analysis used for the separation of B. b. gracilis between seasons in both localities showed that a seasonal variation affected mainly specimens from the center suggesting seasonal move of fishes.

Gonadal maturation and histological observations of the grey triggerfish Balistes capriscus Gmelin,1789(Teleostei:Balistidae)in the Gulf of Gabès,Tunisia

Objective:To determine the spawning activity using gonadosomatic index(GSI)and gonad histology the Balistes capriscus(Teleostei:Balistidae)of the Gulf of Gabès(Southern Tunisia,Central Mediterranean Sea).Methods:The reproductive biology of the species,based on 756(480 females and 276 males),collected from commercial catches at several fishing ports including Chebba,Kerkennah and Zarzis at respective GPS coordinates(34°14'N,11°06'E),(34°45'N,11°17'E),(33°41'N,11°48'E)was studied over 28 months(January 2008-April 2010)using GSI and gonad histology.Sizes used in this study ranged from 11.30 to 45.60 cm in fork length.Results:Both GSI and gonad histology suggest that spawning activity occurred mainly between July and mid-September with a peak in July,coinciding with summer time.The first maturation occurred at 20.26 cm fork length for females and 21.30 cm fork length for males.The monthly values of hepatosomatic index and condition factor(K)indicated that the liver is the main organ responsible for the mobilization process of the energizing reserves during the sexual cycle.Conclusions:It is the first inventory of gonadal maturation and histological observations of the grey triggerfish Balistes capriscus Gmelin,1789(Teleostei:Balistidae)in the Gulf of Gabès,(Southern Tunisia,Central Mediterranean Sea).

Parasitic inventory of Balistes capriscus(Teleostei:Balistidae)from the Gulf of Gabès(Southern Tunisia,Central Mediterranean Sea)

Objective:To investigate the parasitic inventory of Balistes capriscus(Teleostei:Balistidae)(B.capriscus)from the Gulf of Gabès(Southern Tunisia,Central Mediterranean Sea).Methods:A parasitological survey of the grey triggerfish B.capriscus(Gmelin,1788)from the Gulf of Gabès(Southern Tunisia,Central Mediterranean Sea)was conducted monthly from May 2007 to April 2009.A total of 480 fishes were collected from commercial catches by pelagic trawl net at different fishing ports at Chebba(34°14'N,11°06'E),Kerkennah(34°45'N,11°17'E)and Zarzis(33°41'N,11°48'E).The weight,the size,the sex,the date and the area of capture of each specimen were recorded.B.capriscus were then examined to search for ectoparasites and endoparasites.For each parasite species,parasitological indices were calculated.Results:Five species of parasites were identified,among which a new species of Digenea Hypocreadium caputvadum was discovered and two species of parasites were reported for the first time in the Mediterranean.Conclusions:It is the first inventory of the ecto and endoparasites of grey triggerfish collected from the Gulf of Gabès Mediterranean Sea.

Influence of season,size and sex on the dynamic of gill metazoan parasite infesting the Balistes capriscus(Teleostei:Balistidae)of the Gulf of Gabès(Tunisia)

Objective:To investigate the effects of season,size and sex on the dynamic of gill metazoan parasite infesting the Balistes capriscus(Gmelin,1788)(Teleostei:Balistidae)(B.capriscus)of the Gulf of Gabès(Southern Tunisia,Central Mediterranean Sea).Methods:A parasitological survey of the grey triggerfish B.capriscus from the Gulf of Gabès(Southern Tunisia,Central Mediterranean Sea)was conducted monthly from June 2011 to June 2012.A total of 1080 fish were collected from commercial catches by pelagic trawl net at different fishing ports at Chebba(34°14'N,11°06'E),Kerkennah(34°45'N,11°17'E)and Zarzis(33°41'N,11°48'E).The weight,size,sex,date and area of capture of each specimen were recorded.Then,B.capriscus was examined to search for ectoparasites.For each parasite species,parasitological indices were calculated.Results:The parasite species are indentified as two copepods:Naobranchia variabilis,Taneacanthus ballistae and a monogenean:Ancyrocephalus balisticus.The parasitological indices depend significantly on seasonality;the highest prevalence of Naobranchia variabilis,Taneacanthus ballistae and Ancyrocephalus balisticus(28.89%,35.93%and 55.56%respectively)was recorded during summer season(June–August),while the lowest prevalence of each(6.3%,4.44%,8.15%)recorded during winter season(December–February).Furthermore the parasitological indices depend significantly on the host size but not on host sex.Conclusions:Our data suggest that the dynamic of gill metazoan parasite infesting B.capriscus is a result of a complex of biotic and abiotic factors.It is the first study on the effects of season,size and sex on the dynamic of gill metazoan parasite infesting B.capriscus(Teleostei:Balistidae)of the Gulf of Gabès(Southern Tunisia,Central Mediterranean Sea).