Saccular otolith shape and size were analysed for the first time in 120 adult individuals of D. vulgaris collected from two localities, the Bizerte and Ghar El Melh lagoons (north-east Tunisia). The objectives were (1) to examine the specific inter- and intra-individual variation in the otolith shape using elliptical Fourier analysis combined with measures of length (LO), width (WO) and area (AO); (2) to use the otolith shape and size analysis as a phenotypic-based approach to discriminate the stock structure of this species in the two localities to investigate whether they represent two separate stocks to inform on appropriate management procedures; and (3) to test for biases resulting from potential fluctuating asymmetry (FA) in the otolith size on the discrimination of stock structure. Discriminant function analysis performed with the normalized elliptical Fourier descriptors coefficients showed statistically significant differences (P < 0.0001) in the otolith contour shape, i.e. asymmetry, either between the left and right sides or between the same sides (left-left and right-right) within and among individuals of the two localities. Besides, a significant asymmetry (P < 0.05) was found in WO and AO among individuals within the Bizerte locality and in WO only within the Ghar El Melh locality. Moreover, significant FA was observed in the otolith size parameters among individuals of the two localities. This significant asymmetry detected in the otolith shape, as well as in the size due to FA, within and among individuals of D. vulgaris collected from the Bizerte and Ghar El Melh localities confirms that the two stocks could be discriminated from each other and should be managed separately. This asymmetry is discussed in light of the instability of development caused either by environmental stress associated with the variation in water temperature, salinity, depth, feeding conditions and pollutants that have led to abnormalities in the development of individuals or by the presence of poor living conditions for the larvae resulting from unfavourable environments.

Despite the high commercial value of the striped seabream Lithognathus mormyrus (Linnaeus, 1758) in the Gulf of Tunis, biological data on its age, growth and exploitation rate are lacking. With the aim of estimating growth parameters, 516 individuals, ranging from 6–27.5 cm total length and from 3.5–293.5 g total weight, were collected from the artisanal fishing fleet between February 2014 and July 2016. The somatic growth presented a positive allometry and was described by the equation TW = 6.54 10−3TL3.213. The monthly analysis of the marginal increment of the otoliths revealed that only one annulus was deposited per year. The estimated von Bertalanffy growth parameters were: L∞ = 30.18 cm, k = 0.303 year−1 and t0 = −1.42 years. Total and natural instantaneous rates of mortality were respectively Z = 0.784 year−1 and M = 0.698 year−1. Exploitation rate (E = 0.1) showed that the Gulf of Tunis stock of L. mormyrus is not overexploited. The estimated length class giving highest yield (Lopt) was 17.15 ± 1.71 cm.

For the first time, saccular otolith shape and size were analysed in 254 samples of the bogue Boops boops collected from the marine stations of Bizerte and Kelibia situated in north-east Tunisia. The objectives were (1) to examine the inter- and intra-population variation in the otolith shape and size, including length (Lo), width (Wo) and area (Ao) measurements, and (2) to assess the relationship between otolith mass asymmetry (OMA) and total fish length (TL). In addition, the impact of pollution present in these two stations on the shape and size of the otolith in relation to the TL was discussed. Analyses of the otolith shape and biometric data showed a statistically significant asymmetry in the otolith shape (P < 0.0001) between the right and left sides within the population of Bizerte, as well as between the otoliths from the same right-right and left-left sides between the populations of Bizerte and Kelibia. Similarly, a significant Wo asymmetry (P < 0.05) was recorded within the population of Kelibia. Conversely, a significant symmetry was detected in Lo and Ao (P > 0.05) between the right and left sides within the populations of Bizerte and Kelibia. Moreover, the level of asymmetry of Ao was higher than that of Lo and Wo in both populations. Nevertheless, Student's t-test showed no statistically significant differences (P > 0.05) for Lo, Wo and Ao in relation to the means of TL between the three groups of the populations of Bizerte and Kelibia, although significant differences (P < 0.05) were found by using box plots. Furthermore, no statistically significant relationship (P > 0.05) was detected between OMA and TL within and between the populations of Bizerte and Kelibia. The possible cause of fluctuating asymmetry (FA) in the otolith shape and size both within and/or between populations of the two stations has been discussed in relation to the instability of development induced by environmental stress associated with the variation in water temperature, salinity, depth, feeding conditions and pollutants present in these stations.

Crenidens macracanthus was originally described in 1874 based on a single specimen collected from Chennai (Madras), south-east coast of India. In 1875, the species was synonymized with C. indicus without citing any valid reason. Since then, no taxonomic studies have been attempted for the genus Crenidens, except in 2013 the species was resurrected from synonymy and redescribed as a valid species based on the holotype and non-type specimen. In view of the fact that C. macracanthus is a poorly known species, it is redescribed based on examination of 30 additional specimens of 105.8–162.2 mm SL, collected from Puri, Odisha, north-east coast of India (Bay of Bengal) from 2017–2019, using morphological and molecular examinations. Our study provides a detailed morphological description, first colour photographs and phylogenetic analysis using COI barcodes of the species. The study has expanded the range in several morpho-meristic characters in comparison with the type and non-type specimens described earlier. The species in fresh condition can be easily distinguished from its two congeners (C. crenidens and C. indicus) by the yellowish tip of the lower caudal-fin lobe. Our study has also extended the distribution range of C. indicus (previously known only from the north-eastern Arabian Sea) to the eastern Indian Ocean, based on examination of a preserved specimen collected from Tuticorin, Tamil Nadu.

Fossil fishes are among the rarest in volcanic oceanic islands, their presence providing invaluable data for the understanding of more general (palaeo)biogeographical patterns and processes. Santa Maria Island (Azores Archipelago) is renowned for its palaeontological heritage, with representatives of several phyla, including the Chordata. We report on the fossil fishes, resulting in an increase in the number of Pliocene fishes from the Azores to 11 taxa: seven Chondrichthyes and at least four Actinopterygii. The genus Sparisoma is reported for the first time in the fossil record. The presence of fossil remains of the parrotfish Sparisoma cretense in Last Interglacial outcrops is significant, because it posits a setback for the theory that most of the present-day Azorean marine species colonized the area after the last glacial episode. Our multidisciplinary approach combines palaeontological data with ecological and published genetic data, offering an alternative interpretation. We suggest that most of the Azorean shallow-water subtropical and temperate marine species living in the archipelago during the Last Interglacial were not affected by the decrease in sea surface temperatures during the last glacial episode. We also predict low genetic diversity for fish species presently living in the Azores and ecologically associated with fine sediments, as a result of the remobilization and sediment transport to abyssal depths, during the Last Glacial episode; these are viewed as post-glacial colonizers or as ‘bottleneck’ survivors from the Last Glaciation.

The first record of albinism in salema (Sarpa salpa (Linnaeus, 1758)) observed in Cabo de Palos, Western Mediterranean, is reported here. The adult specimen showed an overall lack of pigmentation, presented normally coloured eyes and a further local dyspigmentation, being, therefore, classifiable as a partial albino. No noticeable changes in size nor morphology were detected.

Myxozoans are metazoan parasites which are highly pathogenic in commercially importantfish, particularly in aquaculture. Enteromyxosis is an economically significant diseasecaused by the myxosporean parasite Enteromyxum leei.Presently, early diagnosis of enteromyxosis in sharpsnout seabream was achieved bymonitoring fish on a time-scale scheduled basis in combination with a validated moleculardiagnostic technique. Two different successive fish batches of a commercial fish farm weremonitored starting from the first month of on-growing in sea cages until fish reachedcommercial size. Fish weight and water temperature differentially ranged between them.E. leei detection was performed both by classical microscopicobservation of fresh smears and by quantitative polymerase chain reaction (qPCR) whileprevalence, mean intensity and mortality rate were calculated. In total, 520 fish werescreened; 320 from the first batch and 200 from the second one. Parasitosis illustrated aseasonal occurrence pattern (spring and summer). When qPCR was used as a diagnosticmethod, enteromyxosis was diagnosed earlier with more increased prevalence compared to themicroscopic observation. In this case, the parasite was detected at the lowest watertemperature that has ever been recorded (14.7 °C), during the first month of on-growing in sea cages. The two-factorcombination of water temperature and fish weight proved to be the most significant factorthat could determine the emergence and development of parasitosis and smaller fish provedto be more susceptible. Mortality was influenced by both prevalence and intensity ofparasitosis. An earlier diagnosis and identification of all developmental stages of theparasite throughout its life cycle was verified with qPCR, significantly before anyoutbreak occurred. The latter could become a key diagnostic tool for the control ofenteromyxosis, allowing stakeholders and fish farmers to adopt all necessary precautionarymeasures minimizing economic loss in sharpsnout seabream intensive farming.

The Red pandora Pagellus bellottii was recorded for the first time in the south-eastern Mediterranean in Haifa Bay, Israel, on 20 January 2010. Apparently, this eastern Atlantic Ocean species has recently started to disperse into the eastern Mediterranean. After an initial record from Syria in 1992, this is the second record from the eastern Mediterranean, which indicates the possibility that small populations may have established themselves there.

The reproductive features of four commercially important species of the Diplodus genus were studied in the Gulf of Tunis to contribute to better fisheries management on the local scale. The study was specifically aimed to estimate sex-ratio and size at first maturity, to determine spawning season, to analyse hepatic and muscular energy reserve changes and to highlight possible regional difference over the Diplodus geographical distribution. A total of 570 Diplodus vulgaris (two-banded seabream), 428 Diplodus annularis (annular seabream), 350 Diplodus sargus sargus (white seabream) and 218 Diplodus puntazzo (sharpsnout seabream) were collected from the commercial catches of the artisanal fleet between October 2004 and June 2006. Male:female ratio was initially skewed in favour of females for the four Diplodus species and especially among larger-sized individuals. Length and age at first maturity was 17.4 ± 0.2 cm total length (TL) (4 years) for D. vulgaris, 9.7 cm TL (2 years) for D. annularis, 21.0 ± 0.3 cm TL (4 years) for D. s. sargus, 21.5 ± 0.2 cm TL (3 years) for D. puntazzo and a recommendation is made for the increasing of the captured length. According to the monthly succession of gonad maturity stages and the yearly gonadosomatic index (GSI) fluctuation, the spawning season of Diplodus species present a temporal succession along the year. The two-banded seabream has a winter spawning period, the white seabream is mainly a spring spawner, the annular seabream spawns essentially in summer months and the spawning of sharpsnout seabream takes place in autumn. Generally, hepatosomatic index presented an inverse trend to GSI in relation to the breeding activity. The condition factor showed significant monthly variations affected by the sexual cycle of the Diplodus species.

The silver porgy (Diplodus argenteus) is an occasional cleaner of two species of fish in the southern portion of the south-west Atlantic. We record herein for the first time this fish species associating with green turtles (Chelonia mydas) and cleaning their carapaces. Only juveniles were recorded cleaning turtles, scraping off microorganisms that fouled the carapace.

We investigated whether host specificity is linked to variability within species of Lamellodiscus monogeneans, which are gill ectoparasites of the Sparidae. We sampled fish parasites in the northeastern part of the Mediterranean Sea: 4 specialist species, using 1 single host species, and 3 generalist species, using 2 distinct host species. Intraspecific variability was assessed from 2 different datasets. Morphometric variability of the attachment organ, called the haptor, was estimated first from measurements of several sclerified haptoral parts on 102 individuals. Genetic variability was calculated based on comparisons of sequences derived from the first internal transcribed spacer (ITS-1) of nuclear ribosomal DNA of 62 individuals. Morphometric variances in the specialist versus generalist species were compared via principal component analysis and F-tests, and uncorrected genetic distances (p-distances) were estimated within each species. We showed that the inter-individual variance of morphometric characters, as well as p-distances, are clearly greater within generalist species than specialist ones. These findings suggest that a relative increase in morphological and molecular variability enhances the possibility to colonize new host species in monogeneans, and supports the hypothesis that intraspecific variability could be a potential determinant of host specificity.

We examined the patterns of composition and structure of parasite communities in the Mediterranean sparid fish Boops boops along a gradient of fish sizes, using a large sample from a single population. We tested the hypothesis that species forming the core of the bogue parasite fauna (i.e. species which have a wide geographical range and are responsible for recognizable community structure) appear early in the fish ontogeny. The sequential community development observed supported the prediction that core species appear in the fish population earlier than rare and stochastic species. There was also a strong correlation between the order of ‘arrival’ of the species and their overall prevalence. Six key species were responsible for recognizable community structure across size/age cohorts; the addition to this baseline community of key parasite species resulted in a nested structure that is linked to differential species abundance rather than fish size. Information on the life-cycles, distribution and host range of the parasites is used to explain the observed patterns of parasite community structure. We conclude that the small mouth size of B. boops coupled with suction feeding may provide a setting for passive sampling as a mechanism leading to non-random parasite community structure.

In the Mediterranean Sea, the fish Sarpa salpa (Sparidae) is the only vertebrate grazer of Posidonia oceanica meadows. In order to gain knowledge about the behaviour of S. salpa and a better understanding of the meadow's primary production recycling, an original study was designed using ultrasonic telemetry to investigate activity patterns and space utilisation in the field. During June–September 2000, we compared diel movements of six adult S. salpa (249–317 mm FL and 313–633 g) in the Bay of Calvi. These fish were tagged by intraperitoneal insertion of ultrasonic transmitters. Their positions were recorded with a directional hydrophone from a small boat with an accuracy between 10 and 50 m, depending on the local environment. The tracking duration ranged from 3 to 22 days (average 11.8 ± 7.3). Locations were performed from at least dawn to dusk or early night, and one fish was tracked during the entire 24-h cycle. Fish were more mobile during the twilight periods, but statistical analysis indicated individual differences for the precise period of mobility. Two major behavioural patterns were observed: first, the fish remained in close vicinity of the harbour during the day and moved away to the north or the south at dusk to access nocturnal sites, occupying a home range of about 4.3 ha. The second behavioural pattern involved persistent occupation of the same sites during day and night within a relatively restricted home range (about 0.8 ha). Great variation in mobility was found and the same individual fish could show both kinds of behaviour.

A longline ‘métier’ using small hooks for ‘red’ sea breams (Pagellus acarne and Pagellus erythrinus) in the Algarve (south of Portugal) was studied. Experimental longlining was carried out with three sizes of "Mustad" round bend, flatted, spade end Quality 2316 DT hooks (numbers 11, 13 and 15) and two types of bait: razor shell (Ensis siliqua) and mud shrimp (Upogebia pusilla). A total of 3 328 fish and at least 36 species were caught with 33 600 hooks fished in 28 longline sets. Five species of sea breams (Sparidae) accounted for 79% of the catch: Pagellus acarne, Pagellus erythrinus, Diplodus vulgaris, Spondyliosoma cantharus, and Boops boops. High catch rates of 20-30 fish per 100 hooks were made in a number of 1 200 hook longline sets, with total catch weights of 40 to more than 60 kg per set. In general, the smallest hook (number 15) had the highest catch rate. Bait type did not significantly affect the catch size distributions. Although more fish were caught with the razor shell bait, higher catch rates of ‘red’ sea breams were obtained with mud shrimp. Catch rates were also affected by the location of the fishing grounds and the time of the set, with the highest catch rates obtained when the longline was set within two hours before sunrise. A wide size range was caught for each species, with highly overlapped catch size frequency distributions for the three hook sizes used. Except for Spondyliosoma cantharus, few illegal-sized fish were caught, even with the smallest hook. The logistic model fitted by maximum likelihood was used to describe hook selectivity for Diplodus vulgaris, Pagellus acarne, Pagellus erythrinus, and Spondyliosoma cantharus.

Juveniles of the common dentex (Dentex dentex) (2.4 g mean weight), were grown over a 6 week period, fed exclusively on a commercial sea bream diet or an isocaloric moist pellet diet, which was produced on site. Ambient temperature (24.4-26.2 °C) and oxygen content (4.8-5.9 mg/L), as well as the relatively low stocking density (max. 2.62 kg/m3) provided favourable rearing conditions. Survival (63.8% vs 51.6%), specific growth rates (6.1% vs 4.5%) and food conversion efficiency (115.8% vs 76.3%) were considerably elevated in the group fed on moist pellets. The growth performance parameters recorded are considered to be favourable for aquaculture requirements. Agonistic behaviour (particular biting of the tail) was found to be the main cause of the continuous mortality that occurred in both feed groups (78% and 64.8% of total mortality in the dry- and moist-pellet group, respectively). These biting attacks targeted the smallest individuals in a tank, whose mean individual weight made up 49-62% (with dry pellet diet) and 28.9-46.6% (with moist pellet diet) of the respective mean weights. The results indicate a strong relationship between nutrition, size variation and agonistic behaviour in the rearing of cornmon dentex juveniles.