Pojava imposeksa kod vrste Bolinus brandaris (Gastropoda: Muricidae) duž gradijenta priobalno/otvoreno more u zaljevu Gabes (južni Tunis, središnji dio Sredozemnog mora)

The present study provides the first data available on imposex in a gastropod species caught offshore the Tunisian coast. Imposex was analysed in the purple dye murex (Bolinus brandaris) from ten collecting sites offshore the Gulf of Gabès (southern Tunisia, Central Mediterranean Sea). From a total of 584 individuals analysed, females outnumbered males, leading to a female-biased sex ratio (1 F:0.7 M). Among the 353 females analysed, 117 were affected by imposex. On the whole, these females presented low to moderate imposex incidence (I%=33.1) and severity (FPLI=0.3, RPLI=2.6 and VDSI=0.8). The study revealed that imposex is a widespread phenomenon in the Gulf of Gabès and identified a clear inshore/offshore gradient in the imposex indices of B. brandaris. Regression analysis detected highly significant negative correlations between imposex indices and the distance to the coastline and depth of the collecting sites. Principal components analysis highlighted the specific influence of the distance to the major harbours, either in number of calling vessels (commercial harbour of Sfax) or shipping tonnage (oil terminal of Skhira). This inshore/offshore gradient of imposex development in B. brandaris reflects marked spatial variation in pollution by organotin compounds associated to the shipping activity. Overall, the study provides valuable baseline data for assessing the future evolution of imposex in B. brandaris, and subsequently the spatial and temporal trends of pollution by organotin compounds offshore the Gulf of Gabès.U radu se iznose prvi podaci o pojavi imposeksa kod puževa uhvaćenih u otvorenom moru Tunisa. Imposeks je analiziran na jedinkama bodljikavog volka (Bolinus brandaris) prikupljenim na deset postaja u otvorenom moru zaljeva Gabes (južni Tunis, središnji dio Sredozemnog mora). Ukupno su analizirane 584 jedinke, a omjer spolova je bio u korist ženki (1 Ž: 0,7 M). Od 353 analizirane ženke, 117 ih je bilo pogođeno imposeksom. Općenito, učestalost imposeksa kod ženki je bila niska do osrednja (I%=33.1) i jačina (FPLI=0.3, RPLI=2.6 i VDSI=0.8). Studija je pokazala da je pojava imposeksa raširena u zaljevu Gabes te je utvrđen jasan gradijent pojavnosti imposeksa kod B. brandaris na relaciji priobalno/otvoreno more. Regresijskom analizom otkrivene su vrlo značajne negativne korelacije između pojavnosti imposeksa, udaljenosti od obalne linije te dubine na kojoj se uzorkovalo. Analiza glavnih komponenti (PCA) istaknula je određeni utjecaj udaljenosti od glavnih luka, i to ovisno o broju plovila (komercijalna luka Sfax) ili brodske tonaže (naftni terminal Skhira). Ovaj priobalno/otvoreno more gradijent razvoja imposeksa odražava značajne prostorne varijacije kod onečišćenja organskim spojevima kositra povezanih s pomorskom djelatnošću. Ova studija pruža vrijedne temeljne podatke za buduću procijenu razvoja imposeksa kod vrste B. brandaris, te prostorno i vremenskih trendova onečišćenja organskim spojevima kositra u otvorenom moru zaljeva Gabes

Raspodjela, brojnost i biološki parametri vrste Cerastoderma glaucum (Mollusca: Bivalvia) duž obale zaljeva Gabes (Tunis, središnji Mediteran)

The cockle Cerastoderma glaucum (poiret, 1789) represents one of the most common marine mollusc species present in soft bottom infralittoral assemblages in Tunisian waters. The status of the species is still poorly known and there is a knowledge gap about its distribution, abundance and biological parameters. The significant ecological role of C. glaucum in the ecosystem and its possible future commercial interest requires a better knowledge of its stock. This study aimed to investigate the distribution, abundance and biology of these cockles along the Gabes coast. Cockles were collected, treated and data were analysed. In terms of geographical occupation, maps of the population distribution were drawn. The results showed a scattered distribution pattern of the species according to location ranging between 0 and 270 individuals per square meter. The consequence was a remarkable biomass which represented 1290±326 tons of total fresh weight and high abundance levels reaching over 403±104 million individuals estimated in the area of 3723 hectares. The distribution of the species has also been investigated in consideration with the size which varied markedly according to location, while the shell length ranged between 5 and 37 mm. Samples presented a balanced sex ratio, with males dominating among smaller individuals and females predominating in larger size-classes contrary to previous findings on this species. The size at which 50% of the population reached maturity was 14.29 and 16.59 mm SL for males and females, respectively. Findings of the current study suggest that C. glaucum well proliferates in southern Tunisian waters.Srčanka Cerastoderma glaucum (poiret, 1789) predstavlja jednu od najčešćih vrsta morskih mekušaca prisutnih u infralitoralnim zajednicama mekog dna u vodama Tunisa. Status ove vrste je još uvijek nedovoljno poznat te postoje praznine u znanju o njenoj raspodjeli, brojnosti i biološkim parametrima. značajna ekološka uloga vrste C. glaucum u ekosustavu i mogući budući komercijalni interes zahtijevaju bolje znanje o njenom stoku. Ova studija je usmjerena na istraživanje raspodjele, brojnosti i biologije srčanki duž obale zaljeva Gabes. Srčanke su sakupljane, obrađene i analizirani su podatci. u pogledu geografske rasprostranjenosti, nacrtane su karte raspodjele populacije. rezultati su pokazali raspršeni uzorak raspodjele vrste prema lokaciji u rasponu od 0 do 270 jedinki po kvadratnom metru. posljedica je bila izvanredna biomasa koja je predstavljala 1290±326 tone ukupne svježe mase i visoke razine brojnosti koje dosežu preko 403±104 milijuna jedinki procijenjenih na području od 3723 hektara. raspodjela vrste također je bila istraživana s obzirom na veličinu koja značajno koleba ovisno o lokaciji, dok je dužina ljušture bila u rasponu između 5 i 37 mm. primjerci su predstavili uravnotežen omjer spolova, sa mužjacima koji prevladavaju među manjim jedinkama i ženkama koje prevladavaju u razredima veće veličine, suprotno prijašnjim saznanjima za ovu vrstu. veličina kod koje 50% populacije doseže zrelost bila je između 14,29 i 16,59 mm Sl (shell length - dužine ljušture) za mužjake i ženke. Saznanja ove studije navode na to da se vrsta C. glaucum uspješno razmnožava u vodama južnog Tunisa

Starost i rast glavoča travaša Zosterisessor ophiocephalus Pallas, 1811 u zaljevu Gabes (Tunis, središnji Mediteran)

Zosterisessor ophiocephalus is currently an important component of the eastern Mediterranean inshore fisheries. In Tunisia it was recorded for the first time in the Gulf of Gabes in 1993, where it is now an important fished species. In this study age and growth parameters were determined in the Gulf of Gabes (southeast of Tunisia) based on otolith analysis of 824 specimens caught between September 2006 and August 2007. Monthly changes in marginal increments, determined from alternation of macroscopic opaque and translucent bands, of Zosterisessor ophiocephalus sagittae were examined. These results allowed us the estimation of the approximate age to the appearance of each annulus. The observed age was 6 years old for both sexes. Von Bertalanffy parameters based on length at age data were TL∞ = 24.83 ± 1.69 cm, K = 0.19 ± 0.03 year-1 and t0 = - 0.91 ± 0.12 for males and TL∞ = 24.13 ± 1.17 cm, K = 0.20 ± 0.02 year-1 and t0 = - 0.80 ± 0.09 for females. The length-weight relationship for both sexes of Zosterisessor ophiocephalus is Wt = 0.021 TL 2.789. The size at which 50% of females and males matured was respectively 12.65 cm and 13.91 cm total length (TL). The age at which 50% of females and males matured was respectively 2.9 and 3.5 years.Zosterisessor ophiocephalus je trenutno važna komponenta priobalnog ribolova istočnog Mediterana. U Tunisu je prvi put zabilježen u zaljevu Gabes 1993. godine, gdje je sada važna ribolovna vrsta. U ovoj studiji određivani su parametri starosti i rasta u zaljevu Gabes (jugoistočno od Tunisa) na temelju analize otolita 824 primjerka, ulovljenih između rujna 2006. i kolovoza 2007. godine. Starost je utvrđena na temelju fosilnih naraštajnih prstenova na otolitima (sagitta) vrste Zosterisessor ophiocephalus. Ovi rezultati su nam omogućili procjenu približne starosti pojavom svakog prstena kruga /annulus. Utvrđene su najstarije jednike koje su imale 6 godina za oba spola. Von Bertalenffyjevi parametri zasnovani na podatcima o duljini pri određenoj starosti bili su; TL∞ = 24.83 ± 1.69 cm, K = 0.19 ± 0.03 godina-1 i t0 = - 0.91 ± 0.12 za mužjake i TL∞ = 24.13 ± 1.17 cm, K = 0.20 ± 0.02 godina-1 i t0 = - 0.80 ± 0.09 za ženke. Dužinsko-maseni odnos za oba spola vrste Zosterisessor ophiocephalus je Wt = 0,021 TL 2.789. Veličina kod koje 50% ženki i mužjaka sazrijeva bila je 12,65 cm i 13,91 cm ukupne duljine (TL). Dob kod koje 50% ženki i mužjaka sazrijeva je između 2,9 i 3,5 godina starosti

Neki biološki parametri trlje blatarice Mullus barbatus L., 1758, u tuniskom zaljevu

The red mullet, Mullus barbatus L. 1758 is one of the main target species of the trawl fishing industry along the continental shelf off the Tunisian Gulf. The reproductive biology of this species has been studied based on statistical sampling conducted between February 2003 and January 2004. Length frequency distribution according to sex revealed that the females were highly represantative in the majority of size classes. Monthly variations in the gonadosomatic index (GSI) showed that males spawn from April to July, whereas the reproductive activity of the females occurs in the late spring and summer (May and July). The estimated lengths at maturity (Lm50) were 13.87 cm for males and 13.94 cm for females. According to the length-weight relationship, positive allometry was confirmed for males, females and pooled sexes.Trlja blatarica, Mullus barbatus L. 1758 je jedna od najvažnijih komercijalnih vrsta koćarskog ribarenja duž obale tuniskog zaljeva. Reprodukcija ove vrste je istraživana na ulovljenim primjercima tijekom uzorkovanja od veljače 2003. do siječnja 2004. Ustanovljena učestalost prema duljini i spolu ukazuje da su ženke rasprostranjenije i u većini u svim razredima. Mjesečna kolebanja gonadosomatskog indeksa (GSI) pokazuju da se mužjaci mrijeste od travnja do srpnja, dok su ženke reproduktivno aktivne u kasno proljeće i ljeto (svibanj, lipanj i srpanj). Duljina pri spolnoj zrelosti (Lm50) iznosila je 13.87 cm za mužjake i 13.94 cm za ženke. Prema duljinsko-masenom odnosu, pozitivna alometrija je ustanovljena za mužjake, ženke i ukupni uzorak

Reproduktivna biologija vrste Diplodus vulgaris (Teleostei, Sparidae) u vodama južnog Tunisa (središnji Mediteran)

The reproduction of the common-two banded seabream (N=916), Diplodus vulgaris, was studied in the Gulf of Gabes (Tunisia). The length at the first maturity averages 13.64 ± 0.18 cm for males and 13.84 ± 0.17 cm for females. Macroscopic examination of gonads and gonad-somatic index indicated that spawning occurs once a year between November and February with peak activity in November and December. Fecundity estimates ranged from 8 400 to 30 800 oocytes.Razmnožavanje fratra (N=916) Diplodus vulgaris, istraživano je u zaljevu Gabes (Tunis). Dužina prve spolne zrelosti je u prosjeku između 13,64 ± 0,18 cm za mužjake i 13,84 ± 0,17 cm za ženke. Makroskopsko ispitivanje gonada i gonadsko-somatskog indeksa pokazuje da se mriješćenje odvija jednom godišnje, između siječnja i veljače sa vrhuncem u studenom i prosincu. Procjene fekunditeta su u rasponu od 8 400 do 30 800 oocita

Age and growth of Blue runner Caranx crysos from the Gulf of Gabes (Tunisia)

Ce travail entre dans le cadre des programmes de recherche réalisés pour la gestion durable des ressources pélagiques en Tunisie par l’estimation des biomasses exploitables, l’établissement des paramètres biologiques et l’analyse de l’exploitation. L’étude est basée sur la lecture des otolithes de 1238 spécimens pour déterminer l’âge et la croissance de Caranx crysos du golfe de Gabès dans le Sud-Est de la Méditerranée. La croissance en longueur a montré que la formation de l’anneau d’arrêt de croissance est marquée en hiver (janvier). Le comptage des anneaux d’arrêt de croissance révèle huit groupes d’âge pour les deux sexes (0+ à 7+). Les équations de croissance en longueur selon le modèle de von Bertalanffy sont : LT = 46,67 (1- e – 0,17 (t +1,92)) pour les femelles et LT = 47,66 (1-e0,17 (t+1,86)) pour les mâles. La relation taille-masse a montré que la nature de l’allométrie diffère selon le sexe. Le calcul de la masse maximale théorique (Mp∞) s’exprime par les formules suivantes : Mpt = 1244,98 (1- e – 0,17 (t + 1, 92)) 3,01 pour les femelles et Mpt = 1372,46 (1- e – 0,17 (t + 1,86)) 3,06 pour les mâles. L’âge de la première maturité sexuelle (t50) est estimé à 2,8 ans pour les femelles et 2,4 ans pour les mâles. L’âge théorique maximal (tmax) ou longévité atteint 15,5 ans et 15,6 ans pour les femelles et les mâles, respectivement.This work was executed for the research programs carried out for the sustainable management of pelagic resources in Tunisia by estimating exploitable biomasses, establishing biological parameters and analysing the exploitation. The study was based on reading the otoliths of 1238 specimens to determine the age and growth of Caranx crysos from the Gulf of Gabes in Southeastern Mediterranean. Marginal increment analysis showed a single annual minimum during winter (January). Eight age classes, ranging from 0+ to 7+ years, were determined for both sexes. Growth was modelled using standard and generalized von Bertalanffy equations. The relationship between observed total length TL and age « t » was described by the following standard equations: TL = 46.67 (1- e – 0.17 (t + 1.92)) for females and TL = 47.66 (1- e – 0.17(t + 1.86)) for males. Relationships between body mass (W) and total length (L) showed difference of nature of allometry according to sex. The calculation of the theoretical maximum mass (Mp∞) used the formulas: Mpt = 1244,98 (1- e – 0,17 (t + 1, 92)) 3,01 for females et Mpt = 1372,46 (1- e – 0,17 (t + 1,86)) 3,06 for males. The age at first sexual maturity (t50) was 2.8 years for females and 2.4 years for males. The maximum theoretical age (tmax) or longevity reached 15.5 years and 15.6 years for females and males, respectively

Raspodjela, brojnost i biološki parametri vrste Cerastoderma glaucum (Mollusca: Bivalvia) duž obale zaljeva Gabes (Tunis, središnji Mediteran)

The cockle Cerastoderma glaucum (poiret, 1789) represents one of the most common marine mollusc species present in soft bottom infralittoral assemblages in Tunisian waters. The status of the species is still poorly known and there is a knowledge gap about its distribution, abundance and biological parameters. The significant ecological role of C. glaucum in the ecosystem and its possible future commercial interest requires a better knowledge of its stock. This study aimed to investigate the distribution, abundance and biology of these cockles along the Gabes coast. Cockles were collected, treated and data were analysed. In terms of geographical occupation, maps of the population distribution were drawn. The results showed a scattered distribution pattern of the species according to location ranging between 0 and 270 individuals per square meter. The consequence was a remarkable biomass which represented 1290±326 tons of total fresh weight and high abundance levels reaching over 403±104 million individuals estimated in the area of 3723 hectares. The distribution of the species has also been investigated in consideration with the size which varied markedly according to location, while the shell length ranged between 5 and 37 mm. Samples presented a balanced sex ratio, with males dominating among smaller individuals and females predominating in larger size-classes contrary to previous findings on this species. The size at which 50% of the population reached maturity was 14.29 and 16.59 mm SL for males and females, respectively. Findings of the current study suggest that C. glaucum well proliferates in southern Tunisian waters.Srčanka Cerastoderma glaucum (poiret, 1789) predstavlja jednu od najčešćih vrsta morskih mekušaca prisutnih u infralitoralnim zajednicama mekog dna u vodama Tunisa. Status ove vrste je još uvijek nedovoljno poznat te postoje praznine u znanju o njenoj raspodjeli, brojnosti i biološkim parametrima. značajna ekološka uloga vrste C. glaucum u ekosustavu i mogući budući komercijalni interes zahtijevaju bolje znanje o njenom stoku. Ova studija je usmjerena na istraživanje raspodjele, brojnosti i biologije srčanki duž obale zaljeva Gabes. Srčanke su sakupljane, obrađene i analizirani su podatci. u pogledu geografske rasprostranjenosti, nacrtane su karte raspodjele populacije. rezultati su pokazali raspršeni uzorak raspodjele vrste prema lokaciji u rasponu od 0 do 270 jedinki po kvadratnom metru. posljedica je bila izvanredna biomasa koja je predstavljala 1290±326 tone ukupne svježe mase i visoke razine brojnosti koje dosežu preko 403±104 milijuna jedinki procijenjenih na području od 3723 hektara. raspodjela vrste također je bila istraživana s obzirom na veličinu koja značajno koleba ovisno o lokaciji, dok je dužina ljušture bila u rasponu između 5 i 37 mm. primjerci su predstavili uravnotežen omjer spolova, sa mužjacima koji prevladavaju među manjim jedinkama i ženkama koje prevladavaju u razredima veće veličine, suprotno prijašnjim saznanjima za ovu vrstu. veličina kod koje 50% populacije doseže zrelost bila je između 14,29 i 16,59 mm Sl (shell length - dužine ljušture) za mužjake i ženke. Saznanja ove studije navode na to da se vrsta C. glaucum uspješno razmnožava u vodama južnog Tunisa

Distribución y abundancia de los primeros estadios de desarrollo de Sardina pilchardus en el golfo de Túnez (Mediterráneo central) en relación con los factores ambientales

Four seasonal surveys were carried out in the Gulf of Tunis between summer 2002 and spring 2003 to study the abundance and distribution of Sardina pilchardus eggs and larvae in relation to environmental parameters. In the Gulf of Tunis, Sardina pilchardus begins spawning in autumn (23 eggs/10 m²) and attains its peak in winter (257 eggs/10 m²) when the mean SST is lowest (13.4°C). Sardine reproduction seems to be triggered by the decrease in the SST. In winter, the main spawning areas were located to the south of Zembra Island and the north of Cape Bon. Larvae were more abundant in winter (38 larvae/10 m²), while lower densities were collected in autumn and spring (1 larva/10 m²). The highest abundance of larvae (288 larvae/10 m²) was recorded southwest of Zembra Island. Eggs and larvae were mainly concentrated in the relatively warmer and saltier waters with high zooplankton abundance and, inversely, with a low concentration of nitrate and chlorophyll a and a low diatom abundance.Se llevaron a cabo cuatro campañas en el golfo de Túnez, entre verano del 2002 y primavera del 2003, con el objetivo de estudiar la abundancia y distribución de los huevos y larvas de Sardina pilchardus en relación con parámetros ambientales. En el golfo de Túnez Sardina pilchardus inicia la freza en otoño (23 huevos/10 m²), alcanzando el pico de puesta en invierno (257 huevos/10 m²), cuando la temperatura superficial media (SST) es mínima (13.4°C). La reproducción de la sardina se dispara al parecer por el descenso de la SST. En invierno, las principales áreas de puesta se localizaron al sur de la isla de Zembra y en el norte del Cabo Bon. Las larvas fueron más abundantes en invierno (38 larvas/10 m²); mientras que se recogieron menores densidades en otoño y primavera (1 larva/10 m²). La mayor abundancia larvaria (288 larvas/10 m²) fue observada en el suroeste de la isla de Zembra. Los huevos y larvas se concentraron principalmente en las aguas relativamente más cálidas y salinas, con altas abundancias de zooplancton, e inversamente bajas concentraciones de nitrato, clorofila a y abundancia de diatomeas

Áreas de puesta y distribución larvaria de anchoa Engraulis encrasicolus en relación con las condiciones ambientales en el Golfo de Túnez (Mediterráneo Central)

Early life stages of anchovy were investigated in the Gulf of Tunis by means of four seasonal surveys carried out from summer 2002 to spring 2003. Anchovy eggs and larvae were found all year round, but they were much more abundant in spring and summer. In spring, the main spawning area was located in the north of the Gulf, to the west and southwest of Zembra Island. In summer, higher egg and larva abundances were also observed to the southwest of Zembra Island, but secondary spawning grounds were detected in the vicinity of the mouths of the Rivers Majreda and Meliane. No direct correlations between sea surface temperature (SST), salinity (SSS) and chlorophyll a and the horizontal distribution of eggs and larvae were observed. However, egg distributions in all seasons and larval distributions in summer and autumn were significantly related to depth. The temporal variation of temperature seems to control the spawning intensity and the beginning of spawning seems to be triggered by the increase in SST.Se estudiaron los huevos y larvas de anchoa en el Golfo de Túnez por medio de cuatro campañas estacionales llevadas a cabo entre verano del 2002 y primavera del 2003. Los huevos y larvas de anchoa se encontraron a lo largo de todo el año; pero fueron mucho más abundantes en primavera y verano. En primavera, la principal área de puesta se localizó en el norte del Golfo, al oeste y suroeste de la isla de Zembra. En verano, las mayores concentraciones de huevos y larvas también se encontraron en el suroeste de la isla de Zembra; pero se detectaron áreas de puesta secundarias cerca de las desembocaduras de los ríos Majreda y Meliane. No se encontraron correlaciones directas entre la temperatura superficial (SST), la salinidad (SSS) y la clorofila a y la distribución horizontal de huevos y larvas de anchoa. Sin embargo, la distribución de huevos, durante todo el año, y las distribuciones larvarias, en verano y otoño, se relacionaron de forma significativa con la profundidad. La variación temporal de la temperatura parece controlar la intensidad de la puesta y el inicio de la freza parece dispararse por el incremento de la SST

Reproduktivna biologija vrste Diplodus vulgaris (Teleostei, Sparidae) u vodama južnog Tunisa (središnji Mediteran)

The reproduction of the common-two banded seabream (N=916), Diplodus vulgaris, was studied in the Gulf of Gabes (Tunisia). The length at the first maturity averages 13.64 ± 0.18 cm for males and 13.84 ± 0.17 cm for females. Macroscopic examination of gonads and gonad-somatic index indicated that spawning occurs once a year between November and February with peak activity in November and December. Fecundity estimates ranged from 8 400 to 30 800 oocytes.Razmnožavanje fratra (N=916) Diplodus vulgaris, istraživano je u zaljevu Gabes (Tunis). Dužina prve spolne zrelosti je u prosjeku između 13,64 ± 0,18 cm za mužjake i 13,84 ± 0,17 cm za ženke. Makroskopsko ispitivanje gonada i gonadsko-somatskog indeksa pokazuje da se mriješćenje odvija jednom godišnje, između siječnja i veljače sa vrhuncem u studenom i prosincu. Procjene fekunditeta su u rasponu od 8 400 do 30 800 oocita