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Age and growth of the horse mackerel Trachurus trachurus, caught in the two sides of the Strait of Sicily, central Mediterranean Sea (Italy: GSA16 and Tunisia: GSA13), were estimated by length-frequency analysis using FISAT II software. The estimated Von Bertalanffy growth parameters, compared with likelihood ratio test showed significant differences in horse mackerel growth, caught from the two areas. Trachurus trachurus from Tunisia tended to be greater in size than those from Italy. Satellite sea surface temperature revealed a constant higher temperature regime in Tunisian waters, which resulted 1°C warmer than Italian waters. Chlorophyll a concentration showed a higher primary production (+ 12%) in the Italian waters compared to Tunisian waters. Relationships between growth and geographical distribution denote the effect of environmental conditions on growth especially water temperature and primary production, although the role of other factors could not be excluded, among them genetic and/or epigenetic ones.

The Workshop on age validation studies of small pelagic species (WKVALPEL) fo-cused on validating ageing criteria for small pelagic species (anchovy, horse mackerel, chub mackerel, mackerel and sardine). The aim of the workshop was to collate information on existing ageing protocols and to use these to support development of a validated protocol to better standardize age estimates. One of the main sources of error affecting ageing precision is the discrimination bet-ween the false ring and annulus. An ageing process follows a number of typical steps. First, an ageing methodology is established, based on scientific information, to obtain age data for a particular species. Once age results are available, some analysis is re-commended to improve precision among different readers and/or readings. The next step is to perform other studies that offer independent results used to support, or not, an accepted ageing methodology. Several matching and independent results help to corroborate certain ageing criteria. Each study determines how precision and/or trueness are enhanced. In general, these methods are included in indirect or semi-direct validation categories, as true ages are not actually known in any of them. Some other methodologies, usually more complex and costly, are considered strictly as validation experiments, as results approach to real ages. Tagging-recapture experiments and rearing in captivity are included within this category. The latest available information on ageing data (precision and/or validation studies) was presented for a number of different species of small pelagics. Methods highlighted included marginal increment analysis (MIA), marginal analysis (MA), length frequency distribution analysis (LFDA) and back calculation (BC). A synthesis table of the last annual growth workshops and exchanges by species is also presented. The goal, for each species (Engraulis encrasiculus, Sardina pilchardus, Clupea ha-rengus, Sprattus sprattus, Scomber scombrus, Scomber colias, Trachurus trachurus, Trachurus mediterraneus, Trachurus picturatus, Micromesistius potassou), was to add information on the exchange or workshop and to present the major difficulties that caused low Percentage of Agreement between the age readers as well as to recommend some guidelines to overcome those difficulties. Given that several methods exist for validation of age readings of calcified structures, a summary table of age validation methods used for all small and medium pelagic species in European waters was developed with a focus on the feasibility for the small pelagic species and validation strength of the folowing methods: BC, LFDA, Weight frequency distribution (WFD), Progression of strong year-classes, MIA, MA, daily growth increments (DGI), Daily increments widths, Tagrecapture analysis and Captive rearing.

This study estimated the age of Hexaplex trunculus (Gastropoda: Muricidae) by analysing operculum growth marks. Surface striae and adventitious layers were counted in opercula of H. trunculus from the Ria Formosa Lagoon (southern Portugal) and from the Bizerte Lagoon (northern Tunisia), and in aquacultured individuals used for validation of the ageing technique. Operculum growth features were also compared between H. trunculus populations under contrasting environmental conditions (namely seawater temperature). Despite high inter-individual variability, all H. trunculus populations displayed a clear increasing trend in the number of striae and layers with increasing specimen size. The operculum marginal growth revealed that opercular deposition is not annual. Instead, a few growth marks are formed in the operculum each year, which was confirmed with reared specimens. In both ageing methods, considerable variation in the number of counts at a determined shell length indicates that operculum growth marks should be interpreted cautiously because they might not correspond accurately with individual age. Because of the subjectivity inherent to either method, counting striae and layers in opercula only provides rough age estimates of H. trunculus. published

The reproductive strategy of red spiny lobster Palinurus elephas from the north coast of Tunisia was investigated. We examined oogenesis of P. elephas by studying the histology of the ovaries. Seven growth substages of oocytes were distinguished: 1) early primary oocyte, St1; 2) late primary oocyte, St2; 3) primary vitellogenic oocyte, St3; 4) early secondary vitellogenic oocyte, St4; 5) late secondary vitellogenic oocyte, St5; 6) hyaline oocyte, St6; and 7) atretic oocyte, Atr. The kinetics of oogenesis of females is characterized by six successive ovarian development phases: Juvenile, sexual resting, beginning of vitellogenesis, vitellogenesis, spawning and post-spawning and recuperation. The oocyte diameter frequency distributions were established for each mature female sampled and fitted by a Weibull function: . At the mature ovarian phases, two populations of oocytes were distinguished; a fairly synchronous population of large vitellogenic oocytes (St3 or St4 or St5), and a heterogeneous pop...

Utilisation de la chimie des otolithes pour déterminer la structure du stock de Sardina pilchardus et d'Engraulis encrasicolus des côtes tunisiennes. La sardine Sardina pilchardus et l'anchois Engraulis encrasicolus ont un grand intérêt économique pour la Tunisie. Cependant peu est connu sur la structure de leurs stocks. L'analyse des signatures chimiques des otolithes va tenter de discriminer les populations de sardines et d'anchois des zones côtières et hauturières du Golfe de Gabès. La composition chimique des otolithes entiers a été analysée par spectrométrie de masse à torche à plasma inductif (ICPMS). L'analyse linéaire discriminante a permis de classer correctement 97% des anchois et 94 % des sardines à leurs groupes d'appartenances : zones côtières et hauturières. Par ailleurs, lorsqu'on associe ensemble les données des deux espèces dans chaque zone (côtière/hauturière), la discrimination est aussi correcte atteignant un succès de bien classé de 88%, en se basant sur le P, le Fe, le Li et le Mg. Les résultats obtenus révèlent une bonne discrimination des groupes de petits pélagiques des zones côtières et hauturières. Ce type d'information aura sans doute de fortes implications sur l'aménagement des pêcheries de sardine et d'anchois des côtes tunisiennes.

This document reviews and compiles the scientific information on some demersal crustaceans relevant for fisheries target species in the south-central Mediterranean Sea: Aristaeomorpha foliacea; Melicertus (Penaeus) kerathurus; Metapenaeus monoceros; Nephrops norvegicus; Palinurus elephas and Parapenaeus longirostris. The document provides a description of each species including bio-ecology, life history parameters, fishery exploitation and fishing gear selectivity information. Scientific information was organized to provide a synthetic outline on each species, including meristic description, ecology (geographical distribution, habitats), biogical information (maximum size, spawning activity, length at first maturity, recruitment at habitat and nurseries, sex ratio, length-weight relationship, maximum age and natural mortality, von bertalanffy growth function, feeding behaviour, stock units). Information on stock status and exploitation when available (abundance indices from trawl surveys, strength of recruitment, stock assessment, fisheries, fishing zones and seasons, yield, fishing and discards) is also provided per species. This work is the result of international scientific cooperation among the fishery research institutions participating in the FAO-MedSudMed Project., peer-reviewed

This study estimated the age of Hexaplex trunculus (Gastropoda: Muricidae) by analysing operculum growth marks. Surface striae and adventitious layers were counted in opercula of H. trunculus from the Ria Formosa Lagoon (southern Portugal) and from the Bizerte Lagoon (northern Tunisia), and in aquacultured individuals used for validation of the ageing technique. Operculum growth features were also compared between H. trunculus populations under contrasting environmental conditions (namely seawater temperature). Despite high inter-individual variability, all H. trunculus populations displayed a clear increasing trend in the number of striae and layers with increasing specimen size. The operculum marginal growth revealed that opercular deposition is not annual. Instead, a few growth marks are formed in the operculum each year, which was confirmed with reared specimens. In both ageing methods, considerable variation in the number of counts at a determined shell length indicates that operculum growth marks should be interpreted cautiously because they might not correspond accurately with individual age. Because of the subjectivity inherent to either method, counting striae and layers in opercula only provides rough age estimates of H. trunculus.

L’étude la croissance est fondamentale dans l’évaluation d’un stock et sa gestion. Ceux-ci ont été estimés pour Palinurus elephas tunisienne par la méthode de l’analyse des fréquences de taille. Actuellement, cette méthode est notre seule recours. La méthode de marquage-recapture, la plus conseillée dans l’étude de la croissance chez les grands crustacés, n’a pas donné pour différentes raisons des résultats satisfaisants. Le programme ELEFAN I a été appliqué pour estimer LC∞, K, to, C et WP. Ils sont respectivement de l’ordre de 155,84 mm de LC, 0,22 ans-1, -0,25 ans, 0,3 et 0,5 chez les femelles et de l’ordre de 201,56 mm de LC, 0,16 ans-1, -0,27 ans, 0,3 et 0,5 chez les mâles. La modélisation a été réalisée par le modèle de Von Bertalanffy avec et sans saisonnalité de la croissance. Une représentation graphique de la croissance en escalier a pu être effectué en tenant compte à la fois de la croissance relative (lors de la mue) et de la croissance absolue décrite par le modèle de Von Bertalanffy. Les données présentées ici devraient fournir un point de départ utile pour l’évaluation de l’état d’exploitation, l’aménagement et la gestion du stock de Palinurus elephas dans les eaux tunisiennes, une ressource marine vivante socio-économiquement très importante qui subit une pression de pêche excessive pouvant entrainer sa surexploitation. These have been estimated for Palinurus elephas by the size frequencies analysis method. The method of marking-recaptures, the more counseled in the growth survey for big crustaceans, didn't give for different reasons a satisfactory results. ELEFAN I program was applied to estimate LC∞, K, to, C and WP. They are respectively 155,84 mm of LC, 0,22 year-1, -0,25 years, 0,3 and 0,5 for females and 201,56 mm of LC, 0,16 year- 1, -0,27 years, 0,3 and 0,5 for males. The modeling was achieved by the model of Von Bertalanffy with and without seasonality of the growth. A graphic representation of the growth in staircase has been done according to the relative growth (during molt) and the absolute growth described by the model of Von Bertalanffy. The data presented here provide a useful starting point for the assessment and the management of Palinurus elephas stock in Tunisian waters. This resource socioeconomically very important undergoes an excessive fishing which can cause its overexploitation. Published Palinurus elephas; stock assessment; growth; growth seasonality; Von Bertalanffy model; markingrecapture; ELEFAN I.

Age and growth of the sardine Sardina pilchardus, caught in the northern and southern areas along the Tunisian coast, were determined by otolithometry. In the two areas, sardines showed a positive allometry. However, at the same length, sardines of the off-shore area (north area) were heavier than those of the coastal water (south area), showing that trophic off-shore regions are more suitable for this species. In both areas, the sardines have short life-spans and grow fast. No growth difference was recorded between males and females in the same area. However a different growth pattern was found between the sardines from the north that have on average a statistically greater size at the same age than those from the south area. The corresponding von Bertalanffy growth equations were in the north area: LF = 20.1[1 - exp (-0.28 (t+2.04))] and in the south area: LF = 17.8[1 - exp (-0.26 (t+2.46))]. Abiotic and/or genetic factors could be involved to explain the growth differences observed between the two areas.

La biologie reproductive, la relation taille-masse ainsi que la condition relative de l’anchois Engraulis encrasicolus et de la sardine Sardina pilchardus ont été étudiées le long des régions Nord, Golfe de Tunis, la région Est et la région Sud des côtes tunisiennes durant la période 2000-2002. Pour l’anchois et la sardine, la sex-ratio globale pour toutes les côtes tunisiennes est voisine de 1,0. L’acquisition de la taille de première maturité sexuelle semble être influencée par la température de l’eau dans les quatre régions. Les périodes de reproduction ont lieu dans les quatre régions d’avril à octobre pour l’anchois et d’octobre à mars pour la sardine. Dans les eaux tunisiennes, l’anchois et la sardine ont une allométrie majorante et une condition qui passe par deux périodes distinctes de bonne et de mauvaise conditions. يهتم هذا العمل بدراسة بيولوجيا التكاثر، علاقة الطول بالوزن والحالة النسبية لأسماك الأنشوة Engraulis encrasicolus و السردينة Sardina pilchardus بالمنطقة الشمالية، بخليج تونس، بالجهة الشرقية و بالجهة الجنوبية للسواحل التونسية خلال الفترة 2000-2002. بالنسبة لجملة عينات الأنشوة والسردينة يتساوى عدد الإناث والذكور. يبدو أن بلوغ الطول عند النضج الجنسي الأول يتأثر بحرارة الماء بغض النظر عن الجهة. تمتد فترة تكاثر الأنشوة في الجهات الأربع من أفريل إلى أكتوبر وبالنسبة للسردينة من أكتوبر إلى مارس. في المياه التونسية تنمو الأنشوة والسردينة نسبيا في الطول أكثر من الوزن. كما تمرا خلال السنة بفترتين واحدة تعكس الحالة النسبية الجيدة والأخرى الحالة النسبية السيئة. The reproductive biology, the length-weight relationships and the relative condition of the anchovy Engraulis encrasicolus and the sardine Sardina pilchardus were studied in the North area, the Gulf of Tunis, the East area and the South area along the Tunisian coasts during the 2000-2002 periods. For the anchovy and the sardine, the overall ratio of male and female along the Tunisian coasts was of 1.0. The occurrence of the first maturity was influenced by the sea temperature in the four areas. The spawning periods took place, in the four areas, from april to october for the anchovy and from october to march for the sardine. Along the Tunisian coast, the anchovy and the sardine showed a positive allometry and a condition characterized by two distinct periods; a good and a hard one. Published Engraulis encrasicolus, Sardinops, Sardina pilchardus, Engraulis encrasicolus, Sardinops, Sardina pilchardus

Age and growth of the European anchovy Engraulis encrasicolus, caught in the Northern and Southern areas along the Tunisian coasts, were determined by otolithometry. Analyses of the otolith marginal zone indicate that a hyaline zone is deposited yearly from November/December to March. In both areas, the anchovies have short lives and grow fast. Their growth was almost achieved during the first year of life and no growth difference was recorded between males and females in the same area. However a different growth pattern was found between the anchovies from the North (open sea) that have on an average a statistically greater size at the same age than those from the South area (inshore coastal water). The corresponding von Bertalanffy growth equations were in the North area: FL = 19.16(1 - e-0.32(t + 1.68)) and in the South area: FL = 17.19(1 - e-0.36(t + 1.01)). Abiotic and/or genetic factors could be involved to explain the growth differences observed between the two areas.

The age and growth of bogue (Boops boops), collected in four areas off the Tunisian coast, were determined by studying growth marks on cross-sectioned otoliths. This calcified structure was chosen because the legibility and regularity of its growth mark patterns appeared to be more reliable than those of other skeletal elements. Opercula and fin rays were rejected because of intense bone remodeling, vertebrae because of numerous minute marks unrelated to cyclic events, and scales because counting of annuli seemed very unreliable, particularly in old specimens. Scales consistently had the highest average percent of error. Marginal zone analysis indicated that the hyaline zone in bogue otoliths was deposited yearly from November to April. Increase of length was determined and length-age data were fitted to Von BERTALANFFY equations. Comparisons of length increases of specimens from the four areas suggest two growth pools with greater increases in the north and east than in the Gulf of Tunis and the south. Relationships between growth and geographical distribution indicated the importance of environmental conditions especially water temperature and food availability, although the role of genetic and/or epigenetic factors could not be excluded.

The reproduction parameters necessary for stock management and catch analysis of anchovy in the North region of Tunisia were studied. The global sex-ratio is close to 1, special caution should be taken using this parameter as it is size dependant. Mean reproduction period extends from April to October. However within this period individuals of population have different spawning and maturation. The size at first sexual maturity Lm50 is about 7.3cm. In the North region of Tunisia, the anchovy landings are lower than the exploitable biomass, therefore the anchovy is an under-exploitable species in this region Le present travail porte sur l'etude, chez l'anchois Engraulis encrasicolus de la region Nord de la Tunisie, des parametres de reproduction necessaires a la gestion des stocks ainsi qu'a l'analyse des debarquements. Le sex-ratio global est voisin de 1, cette valeur est a prendre avec precaution car ce parametre varie en fonction de la taille des individus. L'anchois se reproduit en moyenne d'avril a octobre, les individus de la population sont decales dans leur maturation et emissions. La taille de premiere maturite sexuelle Lm50 est de 7,3cm. Les debarquements d'anchois dans la region Nord de la Tunisie sont inferieurs a la biomasse exploitable. L'anchois est donc une espece sous exploitee dans la region Nord de la Tunisie. يهتم هذا العمل بدراسة معطيات التكاثر، الضرورية لحسن التصرّف في لسمك الأنشوة بالسواحل التونسية بالنسبة لجملة العينات يتساوى عدد الإناث والذكور مع العلم أنّ نسبة كل جنس تتغير حسب طول السمكة. يتكاثر سمك الأنشوة خلال الفترة الممتدة من أفريل إلى أكتوبر مع وجود إختلال بين الأفراد. يبلغ سمك الأنشوة نضجه الجنسي الأول لطول يناهز 7.3 صم. يفوق المخزون المتاح إستغلاله من سمك الأنشوة الكميات المنزلة بمواني الصيد البحري. تبعا لذلك فإنّ سمك الأنشوة بالشمال التونسي دون الإستغلال الأمثل.المخزون، وبتحليل إنتاج الصيد البحري Published

التكاثر والاستغلال - يهتم هذا العمل بدراسة معطيات التكاثر، الضرورية لحسن التصرف في المخزون، وبتحليل إنتاج الصيد البحري لسمك الأنشوة بالسواحل الشمالية لتونس. بالنسبة لجملة العينات يتساوى عدد الإناث والذكور مع العلم أن نسبة كل جنس تتغير حسب طول السمكة. يتكاثر سمك الأنشوة خلال الفترة الممتدة من أفريل إلى أكتوبر مع وجود اختلال بين الأفراد. يبلغ سمك الأنشوة نضجه الجنسي الأول لطول يناهز 7.3 صم. يفوق المخزون المتاح استغلاله من سمك الأنشوة الكميات المنزلة بمواني الصيد البحري، تبعا لذلك فإن سمك الأنشوة بالشمال التونسي دون الاستغلال الأمثل. Le présent travail porte sur l’étude, chez l’anchois de la région Nord de la Tunisie, des paramètres de reproduction nécessaires à la gestion des stocks ainsi qu’à l’analyse des débarquements. Le sex-ratio global est voisin de 1, cette valeur est à prendre avec précaution car ce paramètre varie en fonction de la taille des individus. L'anchois se reproduit en moyenne d’Avril à Octobre, les individus de la population sont décalés dans leur maturation et émissions. La taille de première maturité sexuelle Lm50 est de 7,3cm. Les débarquements d’anchois dans la région Nord de la Tunisie sont inférieurs à la biomasse exploitable. L'anchois est donc une espèce sous exploitée dans la région Nord de la Tunisie. The reproduction parameters necessary for stock management and catch analysis of anchovy in the North region of Tunisia were studied. The global sex-ratio is close to 1, special caution should be taken using this parameter as it is size dependant. Mean reproduction period extends from April to October. However within this period individuals of population have different spawning and maturation. The size at first sexual maturity Lm50 is about 7.3cm. In the North region of Tunisia, the anchovy landings are lower than the exploitable biomass, therefore the anchovy is an under-exploitable species in this region. Published Engraulis encrasicolus; Anchovy; Anchois; Nord de la Tunisie

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