RFLP Analysis of Mitochondrial DNA to Evaluate Genetic Variation in Striped Red Mullet (Mullus surmuletus L.) and Red Mullet (Mullus barbatus L.) Populations

The genetic differentiation of striped red mullet (Mullus surmuletus) and red mullet (Mullus barbatus) was investigated in 6 Mediterranean populations of each species by means of restriction fragment length polymorphism analysis of mitochondrial DNA. Three segments amplified by polymerase chain reaction (control region, COI, and 12S–16S ribosomal RNA) were digested with 20 restriction endonucleases, revealing 71 haplotypes for M. surmuletus and 30 for M. barbatus. For the two species nucleotide diversity was equally distributed within and among populations, leading to N _ST values of 0.545 and 0.500 for M. surmuletus and M. barbatus, respectively. However, intrapopulation and interpopulation genetic structuring appeared to be much higher for M. surmuletus than for M. barbatus (1.88% vs. 0.46% of mean intrapopulation nucleotide diversity; 1.94% vs. 0.47% of mean interpopulation nucleotide diversity; 0.055% vs. 0.002% of net interpopulation divergence). Furthermore, 81.69% of the haplotypes observed for M. surmuletus were unique, whereas 70.29% of M. barbatus individuals were grouped in 3 common haplotypes. Given that fishing pressure and population sizes are similar for both species, this differentiation could be attributed to differences in biological parameters and life histories between the two species, coupled with oceanographic conditions prevailing in the studied area. Received July 25, 2000; accepted December 29, 2000     

First Microsatellite Loci of Red Mullet (<Emphasis Type="Italic">Mullus barbatus</Emphasis>) and Their Application to Genetic Structure Analysis of Adriatic Shared Stock

In order to study the genetic structure of the Adriatic shared stock of red mullet (Mullus barbatus), we developed a set of dinucleotide microsatellite markers. A dinucleotide-enriched genomic library was obtained, and 6 polymorphic dinucleotide loci were successfully optimized. The markers showed high expected heterozygosity (from 0.68 to 0.92) and allele number (from 12 to 33); thus they appear to be suitable for detecting genetic differences in the population of red mullet. Four Adriatic samples were subsequently analyzed for microsatellite variation, and the results showed subtle but statistically significant genetic differentiation, indicating that the Adriatic red mullet may group into local, genetically isolated populations. No correlation between geographic distance and genetic differentiation was observed. In addition, the evidence of recent bottlenecks in the Adriatic samples indicates that the observed population subdivision might reflect random local allelic variations, generated by reproductive success, survival rates, or fishing pressure.     

Environmental influences on the spatial distribution of European hake (Merluccius merluccius) and red mullet (Mullus barbatus) in the Mediterranean

Generalised additive models (GAMs) were used to test the hypotheses that red mullet (Mullus barbatus) and hake (Merluccius merluccius) abundances are related to the bathymetry, spatial location and the temperature-based variability of the NE Mediterranean. Data were collected during a 2-year period (1996–1997) of quasi-synoptic sampling using demersal trawl surveys in the northern Aegean Sea. The results of this study supported these hypotheses. It was found that geographic position and sea bottom characteristics influence the temporal distribution patterns of red mullet and hake. Data are presented that reveal species-specific aggregation patterns and an important habitat utilisation of the area. The modelled species’ abundances showed a strongly non-linear dependence on the explanatory covariates. This study, although not directly dealing with spawning, also provided evidence that red mullet and hake demonstrate environmental and bathymetric preferences in the months posterior to spawning. Mean red mullet abundance was consistently highest in areas with warmer bottom waters in the east and west than in the centre, these areas having shallower depths (35–60 m) and bottom temperatures around 19°C. The red mullet appeared to avoid the cold bottom waters (<16°C) of the deeper regions. Results indicated that areas with the highest hake abundances were located in waters of ∼160 m having bottom temperature of ∼16°C and avoided the shallower waters (<70 m) regardless of their bottom temperature. The present findings also suggested that colder bottom waters at all depths were associated with lower-than-average hake abundance. Red mullet and hake preferences for areas with specific bathymetric and ocean environmental conditions are believed to be linked to the oceanography of the NE Mediterranean ecosystem.     

Oocytes development,maturity classification,maturity size and spawning season of the red mullet (Mullus barbatus barbatus Linnaeus, 1758)

The present study was designed to identify maturity of female red mullet, Mullus barbatus barbatus, using microscopic criteria, offering an accurate determination of the ovarian cycle and estimation of maturity size. Histological analysis of 499 females from 13 monthly samplings was applied (Thermaikos Gulf, N. Aegean Sea, Greece). Oocyte development was divided into five stages, with a mean oocyte size range from 56 to 363 μm in diameter. Ovarian maturity was defined by the maturation stage of the most advanced oocytes and divided into four phases. By using the monthly changes in the percentage frequency of ovarian phases, the ovarian cycle of M. barbatus was divided into three periods: a long period of early oogenesis (November to February), a short period of vitellogenesis (February to April) and a spawning period from April through June with peak activity in May. Both gonadosomatic (up to 7.5%) and hepatosomatic indices (up to 2%) can be used together to predict the spawning period. Red mullet should be classified as a multiple spawning species. Females reached 50% maturity (Lm₅₀) at 11.4 cm and 95% maturity (Lm₉₅) at 15.5 cm TL. The Lm₅₀ values for female red mullet populations across the Mediterranean Sea tended to show differences ranging from 11 to 14.4 cm FL or 11.4–14 cm TL. The current European Union fisheries management plan stipulates a minimum landing size (MLS) of 11 cm TL for Mullidae spp. fisheries in the Mediterranean. This MLS is at the lower part of the Lm₅₀ range, thus allowing an extensive removal of immature juveniles. A revision of this MLS value is recommended to help ensure that red mullet stocks remain within safe biological limits.     

Sorting grid trials to improve size selectivity of red mullet (Mullus barbatus) and annular sea bream (Diplodus annularis) in Turkish bottom trawl fishery

Sorting grids with two different bar spacings (12 mm and 14 mm) were tested to improve size selectivity of the commercially important fish species, red mullet (Mullus barbatus) and annular sea bream (Diplodus annularis), in Turkish bottom trawl fishery. Fishing trials were carried out with R/V ‘Egesüf’ between April and May 2003 in Izmir Bay, Aegean Sea, using a traditional bottom trawl. Selectivity data were collected by the top cover method and analyzed by means of a logistic equation with the maximum likelihood method. Selectivity parameters for individual hauls were obtained with the software program cc 2000 . Mean selectivity was also estimated and compared using the EC Model software that takes between‐haul variations into account. The codend catch size as an additional explanatory variable was used in the comparison. The Kolmogorov–Smirnov (K–S) test was also applied to detect differences between length‐frequency distributions in the upper and lower bags of the 12 and 14 mm bar spacings for red mullet and annular sea bream. The mean L₅₀ values of red mullet were 8.7 and 10.0 cm with the 12 and 14 mm grids, respectively. The L₅₀ value of 14 mm was comparable with the L₅₀ value of the codend mesh size; however, the 12 mm value was rather low. The mean L₅₀ values of 12 and 14 mm bar spacings were 8.8 and 10.4 cm for annular sea bream, respectively; the value of 14 mm bar spacing was very close to 50% size at sexual maturity of the species (10.5 cm). The K–S test indicated length distributions of red mullet and annular sea bream in the 12 and 14 mm upper and lower bags as significantly different (P < 0.05). These results show that improving the size selectivity in a multi‐species fishery using a single selective device is rather difficult. However, higher size selectivity can be obtained when considering the minimum landing size or the 50% sexual maturity size for a given species.     

Aggregation dynamics and foraging behaviour of striped red mullet Mullus surmuletus in the western Mediterranean Sea

Habitat‐related heterogeneity of striped red mullet Mullus surmuletus heterospecific foraging assemblages was examined off the coast of Spain. Video‐based focal‐follows conducted on 122 M. surmuletus assemblages (446 total individuals) revealed an array of attendant species (n = 7) with composition linked to benthic habitat complexity; bare sandy substrata were characterized by homospecific groups of M. surmuletus, while habitats with rock and vegetation attracted a variety of scrounging labrids and sparids. Although the nature of the relationship between M. surmuletus and attendants requires further exploration, the present study indicates that substratum composition can be a driving factor explaining the dynamics of this heterospecific assemblage.     

Morphological variation between red mullet populations in Greece

Morphometric variation in 15 characters of the red mullet Mullus barbatus samples from seven Greek localities was examined using multivariate analysis. ANOVA, stepwise discriminant analysis and cluster analysis revealed a rather high morphological variability between the populations studied. The discriminant analysis revealed that about 80% of the examined fish could be correctly classified into the seven areas. This variability could be explained in terms of genetic structuring of the populations and/or environmental conditions prevailing in each geographic area in combination with fish migration and egg/larvae transportation from one area to another. The results suggest that multivariate analysis when combined with other important biological parameters of red mullet may have important implications for the management of the Greek demersal fish resources.     

The effects of sex and season on the metal levels and proximate composition of red mullet (Mullus barbatus Linnaeus 1758) caught from the Middle Black Sea

The effects of seasonal and sexual differences on the levels of macro, trace element, and toxic metal levels in Mullus barbatus were investigated using the ICP-MS. The quantity relationships of macro elements were found as K>P>Na>Ca>Mg for male, P>K>Na>Ca>Mg in female; the quantity relationships of trace elements were determined as Fe>Zn>Mn>Mo>Se>Cu>Ni>Co in male, Fe>Zn>Mn>Se>Cu>Ni>Mo>Co in female; and the quantity relationship of toxic elements were found as As>Pb>Cd in both male and female. Macro, trace, and toxic metal levels showed no significant differences (p > .05) in terms of sexuality, but demonstrated seasonal differences (p > .05). Overall, the highest level of macro elements was determined in the autumn, while the high level of trace elements was measured in the winter. The As, Cd, and Pb levels in the muscle tissue of red mullet fish were higher than acceptable limits. However, when the Estimated Daily Intake (EDI) and Estimated Weekly Intake (EWI) of both toxic metals are considered, they appear to be below acceptable limits. As a result, it was determined that the red mullet had been contaminated with toxic metals (Cd and Pb) but their levels according to EDI and EWI were below the limit.     

Biology of red mullet,Mullus barbatus (L. 1758), in the Gulf of Castellammare (NW Sicily,Mediterranean Sea) subject to a trawling ban

Under‐or non‐exploited areas are useful to aid in evaluating the potential productivity of fish stocks for sustainable fisheries. The Gulf of Castellammare (NW Sicily), where trawling has been banned since 1990, is a good site to study the biology and dynamics of low impacted fish populations. A total of 661 (595 female and 66 male) specimens of red mullet Mullus barbatus (95–245 mm total length, TL) obtained by monthly sampling from trammel net artisanal fishery, was collected in the Gulf of Castellammare from April 2006 to June 2007. Mature females occurred from April to September, with a peak in May. The mean Gonado‐somatic index (GSI) also showed a May peak for both sexes. From Sagittae (642) readings the age structure ranged from age class I to VII in females and I to V in males. Female growth parameters, estimated according to the classic von Bertalanffy model, were: L_∞ = 221.2 ± 11.51 mm standard error (SE), k_y^?1 = 0.38 ± 0.09 SE, t₀y = ?0.94 ± 0.38 SE. The growth performance index (ø’ = 2.27) was included in the range of values obtained by hard structure readings in the Central Mediterranean. Natural mortality (M_y^?1) of females estimated by different methods ranged between 0.62 and 0.87 (mean value = 0.71 ± 0.06 SE).     

How an invasive alga species (<Emphasis Type="Italic">Caulerpa taxifolia</Emphasis>) induces changes in foraging strategies of the benthivorous fish <Emphasis Type="Italic">Mullus surmuletus</Emphasis> in coastal Mediterranean ecosystems

The foraging behaviour variability of three striped red mullet (Mullus surmuletus L. 1758) populations with respect to the vegetation cover was examined along the French Mediterranean coasts. We tested both the carrying capacity of different habitats and the hypothesis of a food segregation by the invasive alga Caulerpa taxifolia (Vahl) C. Agardh, on the functioning of benthic fish populations. The results indicated a significant site effect on M. surmuletus foraging behaviour and movements. The vegetation cover may play an important role in modifying the striped red mullet cost of foraging (sampling effort) and thus its strategy of prey capture. As long as the cover of marine phanerogams and/or macrophyte algae (Caulerpaceae) increases, the foraging budget and the distances covered in search of prey decrease significantly. Similarly, the striped red mullet increases the prospected sample periods to augment its foraging success, swimming above the bottom. These changes are related to the development of a dense superficial network of plagiotropic rhizomes and stolons, and to the reduction of space between fronds that limits the accessibility to resources and may increase intra-specific food competition. The role of C. taxifolia does not differ from that of other marine phanerogams but induces significant changes in the structure of Mullidae populations at the local level. The rapid expansion of Caulerpaceae in the Mediterranean Sea could constitute a real threat for the balance of the marine coastal biodiversity and the ecology of M. surmuletus, which is considered a flagship species for coastal Mediterranean demersal fisheries.     

Morphological variability of the shape of striped red mullet Mullus surmuletus in relation to stock discrimination between the Bay of Biscay and the eastern English Channel

Truss analysis and length measurements were made on 168 striped red mullet Mullus surmuletus. Multivariate statistical analyses with principal component analysis and partial redundancy analysis (pRDA) were used on these measurements to evaluate the influence of maturity, sex and geographical area distribution on body shape. Truss measurements were important to quantify and discriminate changing body shape, presumably due to changing environmental conditions. Sexual dimorphism was not observed and juveniles could be distinguished from adults based on their body shape. More importantly, M. surmuletus occurring in different geographical areas could be differentiated using this method. Based on pRDA, a significant difference of head morphological dimensions was observed between populations occurring in the eastern English Channel and those occurring in the Bay of Biscay, suggesting that fish from these areas could represent two subpopulations.     

Behavioural response of Mullus surmuletus to habitat modification by the invasive macroalga Caulerpa taxifolia

Densities of red mullet Mullus surmuletus have declined since 1996 at Cap Martin, Alpes‐Maritimes, France, following colonization by Caulerpa taxifolia . Foraging M. surmuletus were rarely observed over C. taxifolia or the seagrass Posidonia oceanica , but were observed over bare sand and endemic macroalgae. Within colonized sites (where the mean cover of C. taxifolia was 30–100%), fish were concentrated on areas with low cover of C. taxifolia (<21%). A difference in the frequency of observations of foraging groups (17%) was observed between sites with and without C. taxifolia . The observed patterns were probably due to a physical barrier to foraging that is presented by meadows of C. taxifolia . Changes to habitat structure that occur when the substratum is colonized by C. taxifolia influence the accessibility to benthic food resources, and consequently the foraging activities of fish that feed on benthic invertebrates. The decline in density of M. surmuletus at Cap Martin could be the result of fish emigration from colonized sites (unfavourable to the species) to uncolonized sites.     

Isolation and charaterization of polymorphic microsatellite loci from so-iuy mullet (Mugil soiuy Basilewsky 1855)

The first set of polymorphic microsatellite markers were developed from so-iuy mullet (Mugil soiuy Basilewsky 1855). From a (GT)n-enriched genomic library, 53 microsatellites were selected for designing microsatellite primers, of which 36 gave working primer pairs. Ten of these loci were polymorphic in a test population of 24 individuals with alleles ranging from 3 to 9, and observed and expected heterozygosities from 0.2083 to 0.9167 and from 0.2651 to 0.8812, respectively. No significant linkage disequilibrium between pairs of loci was found, but two loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction. These polymorphic microsatellite loci should provide sufficient level of genetic diversity to investigate the fine-scale population structure and evaluate the breeding strategy in Mullet. Genbo Xu and Changwei Shao Contributed equally.     

Exploitation patterns of the European hake Merluccius merluccius, red mullet Mullus barbatus and striped red mullet Mullus surmuletus in the western Mediterranean

The exploitation patterns of three target species ( Merluccius merluccius , L. 1758 , Mullus barbatus , L. 1758, Mullus surmuletus , L. 1758) of the western Mediterranean demersal fisheries were compared. The study was carried out in five ports along the Italian and Spanish coasts. These three species are fished simultaneously or sequentially by a number of gears, their use during the year being different depending on the area. The trawl catches dominated the landings, both in number and weight, but varied greatly during the year. The size ranges of specimens in the catches were in their major part different among the types of gear. Artisanal methods (gillnet and long line for M. merluccius , trammel net for Mullus spp.), used seasonally, contributed primarily to landings of larger, adult specimens, whereas trawl catches consisted mainly of smaller sized individuals, recently recruited to the fishery. In M. merluccius, individuals of less than 20 cm total length accounted for 80 to 95% of the annual catch in numbers, and between 15 and 60% of the catch in weight, depending on the port. This situation indicates a substantial over-exploitation and a high risk of long-term unsustainability in stock development and production.     

Isolation and characterization of polymorphic microsatellite loci in Acanthoscelides obtectus Say (Coleoptera: Bruchidae)

Six microsatellite loci were isolated from the bruchid Acanthoscelides obtectus Say (Coleoptera: Bruchidae). Each locus was polymorphic, with the number of alleles ranging from 3 to 18. We found high levels of within‐population variation at most loci, with heterozygosities ranging from 0 to 0.75. Cross‐species amplification of these loci was tested in two other species of the genus Acanthoscelides, A. obvelatus Bridwell and A. argillaceus Sharp.     

The description of Gyrodactylus mulli sp. n. (Monogenea: Gyrodactylidae) from the Black Sea blunt-snouted mullet Mullus barbatus ponticus

A new species Gyrodactylus mulli sp. n. is described from the thorax fins of blunt-snouted mullet Mullus barbatus ponticus by the collections of B. E. Bychowsky made in 1947 near Karadag on the Black Sea. Gyrodactylus mulli sp. n. differs from G. alviga Dmitrieva et Gerasev, 2000 (described from blunt-snouted mullet too) in having another morphotype of the marginal hooks. The new species differs from G. proterorhini Ergens, 1967, which has the identical type of the marginal hooks, in having longer membrane of the ventral connective bar, longer point of the anchors, shorter marginal hooks, and lesser size of the cirrus.     

Fatty acid profile and proximate composition of fillets from Engraulis encrasicholus,Mullus barbatus,Merluccius merluccius and Sarda sarda caught in Tyrrhenian,Adriatic and Ionian seas

The study examined the proximate composition, cholesterol content and fatty acid profile of fillet from the most important species captured in Italian seas and commonly consumed in the European Union, such as anchovy (Engraulis encrasicholus L.), red mullet (Mullus barbatus L.), European hake (Merluccius merluccius L.) and Atlantic bonito (Sarda sarda L.). The fish were caught in three different geographic areas of the Italian seas: south Tyrrhenian (ST), south Adriatic (SA) and Ionian (IO). Anchovy from the ST sea had the highest lipid content (2.27%) compared to fish captured in the SA (1.81%) and IO seas (1.91%) (P < 0.01). Red mullet captured in the SA exhibited the highest amount of lipid content (7.54%) compared to fish from the ST (1.82%) and IO seas (3.23%) (P < 0.01). The total cholesterol content of fish did not show significant differences from one geographic area to the other, particularly for European hake (from 98 to 66 mg per 100 g). The fatty acid profile of anchovy species was not affected by the geographical capture area. European hake caught in the ST sea showed the highest proportion of DHA (29.13%) in comparison to those captured in the SA (19.98%) and IO seas (19.84%). Atlantic bonito from the ST had the highest proportions of DHA (24.94%), compared to those from the SA (12.08%) and IO seas (13.83%). The SA bonitos contained a significantly lower proportion of EPA (3.31%) in comparison to fish from both the ST and IO seas (5.66 and 5.17%, respectively). Red mullet captured in the ST exhibited the highest proportions of DHA, n‐3 PUFA, and total PUFA, and significantly lower proportions of oleic acid and MUFA. The fish from the ST sea showed better nutritional traits than those from other geographical areas although they all had excellent nutritional traits due to the low fat content and very high n‐3 PUFA proportion.     

Evaluating the ability of Bayesian clustering methods to detect hybridization and introgression using an empirical red wolf data set

Bayesian clustering methods have emerged as a popular tool for assessing hybridization using genetic markers. Simulation studies have shown these methods perform well under certain conditions; however, these methods have not been evaluated using empirical data sets with individuals of known ancestry. We evaluated the performance of two clustering programs, baps and structure , with genetic data from a reintroduced red wolf (Canis rufus) population in North Carolina, USA. Red wolves hybridize with coyotes (C. latrans), and a single hybridization event resulted in introgression of coyote genes into the red wolf population. A detailed pedigree has been reconstructed for the wild red wolf population that includes individuals of 50–100% red wolf ancestry, providing an ideal case study for evaluating the ability of these methods to estimate admixture. Using 17 microsatellite loci, we tested the programs using different training set compositions and varying numbers of loci. structure was more likely than baps to detect an admixed genotype and correctly estimate an individual's true ancestry composition. However, structure was more likely to misclassify a pure individual as a hybrid. Both programs were outperformed by a maximum‐likelihood‐based test designed specifically for this system, which never misclassified a hybrid (50–75% red wolf) as a red wolf or vice versa. Training set composition and the number of loci both had an impact on accuracy but their relative importance varied depending on the program. Our findings demonstrate the importance of evaluating methods used for detecting admixture in the context of endangered species management.     

Relationships among fourteen species of Satureja growing wild in Iran detected with molecular markers

The genus Satureja is an important plant with a number of aromatic and medicinal properties. In this research, the relative efficiencies of amplified fragment length polymorphism (AFLP) and selectively amplified microsatellite polymorphic loci (SAMPL) were used to detect genetic relationships among 14 species of Satureja, growing wild in Iran. Eleven AFLP and 14 SAMPL primer combinations produced 999 and 1142 scorable bands, respectively, all of the fragments of which were found to be polymorphic. The average genetic similarity values based on Jaccard's coefficient were 0.24 and 0.21 for AFLP and SAMPL, respectively, indicating considerable distance and diversity in the studied germplasm. The correlation coefficients were statistically significant between both marker systems (r = 0.89). UPGMA derived from the combined binary data matrices of both markers depicted genetic distinctions among the studied species and clustered them into two main clusters and several groups. S. edmondi showed the maximum distance from other species and was placed into a single main cluster, while the maximum similarity was obtained between S. rechingeri and S. khuzistanica. Our results indicate that both marker systems are suitable for differentiating individuals and species of this genus.