Host-parasite relationships: occurrence and effect of the parasitic isopod Mothocya epimerica on sand smelt Atherina boyeri in the Mesolongi and Etolikon Lagoons (W. Greece)

The parasite-host relationship between Mothocya epimerica, Costa 1851 (Isopoda: Flabellifera: Cymothoidae) and sand smelt Atherina boyeri (Osteichthyes: Atherinidae) fish populations were studied in the Mesolongi and Etolikon Lagoons (W. Greece). Prevalence varied during the year from 12.5% in November to 52.5% in September; overall mean prevalence was 41.9%. Parasite size increased with host size. Infections did not have a significant effect on the host's body condition, such as length-weight relationship, gonadosomatic index, hepatosomatic index and relative condition factor. Histological damage to the host was observed on the gills (especially in the second and third and arches upon which the female parasite rests her abdomen). The physiological cost resulting from this infection seems to be little and probably does not constitute a serious threat for individual host survival.     

On the reproductive biology of the sand smelt Atherina boyeri Risso (Pisces: Atherinidae) and its evolutionary potential

The small, typically estuarine fish Atherina boyeri Risso forms local populations which can differ greatly in their population biology and morphology; this species is viewed as being on the brink of speciation. This analysis of the reproductive strategy shows that A. boyeri can rapidly adapt its life history and morphology to environments ranging from freshwater to polyhaline coastal lagoons and oceanic waters. The optimum strategy is shown to be tied to temperate seasonality: the cold winters act to lengthen the life cycle, and result in cyclic switching of energy between reproduction, somatic growth and fat storage. The adaptability of the fish to a range of environmental characters is viewed as being due to natural selection acting to produce a genotype capable of a flexible phenotypic response. This flexibility is essential for survival in the highly variable inshore/brackish habitat. It is argued that such preadaptive plasticity, coupled with the potential for populations to become isolated, produces ideal conditions for speciation. The importance of the coastal, estuarine and lagoonal environment as a springboard for teleost evolution is discussed.     

Acanthocephalan infections in Atherina boyeri (Pisces: Atherinidae) from Tirso.

Infections by the acanthocephalan Telosentis exiguus (Von Linstow, 1901) and another unknown acanthocephalan were studied in the sand smelt Atherina boyeri (Risso, 1810) from the Tirso River mouth in Sardinia. Only a few specimens of T. exiguus (1 male and 2 cystacanths) were found in the host digestive tract; some larvae of an unidentified acanthocephalan encysted in the liver of A. boyeri were also found and are described.     

Age and Growth of Atherina Atherina boyeri (Atherinidae) from Southwestern Crimea (Black Sea)

Journal of Ichthyology - The size and age structure and growth of Atherina boyeri from southwestern Crimea were studied. The ratio of males and females was 1.00 : 1.38, the proportion of males...     

Feeding habits of sand smelt (Atherina boyeri, Risso 1810) in Trichonis Lake (Western Greece)

The feeding habits of sand smelt (Atherina boyeri, Risso, 1810) from Trichonis Lake (Western Greece) were investigated. Stomach contents were analyzed from 240 specimens with total lengths ranging from 35 to 112 mm. Samples were taken at monthly intervals (January–December 1997). Of the total number of stomachs examined, 53 were empty (22.1%). However, values varied greatly with season (maximum in January: 50%; minimum in August: 7.6%). Prey analyses of stomach contents identified 15 important items (%Rn > 0.05) belonging to six major groups: crustacean (copepods, cladocera), mollusca (bivalve: larvae), insects (larvae), cestode worms and finfish (fry and eggs). Dominant prey were larvae of the bivalve Dreissena polymorpha (%Rn = 33.8), the copepods Eudiadomus drieschi (%Rn = 26.4) and the cladocera Diaphanosoma brachyurum (%Rn = 24.2). The importance of cladocera and copepods decreased with increasing size of the sand smelt, while the importance of bivalve larvae, fish eggs and finfish fry increased with increasing sand smelt size. Seasonal changes in diet composition and prey abundance in sand smelt stomachs were recorded as coinciding with the seasonal composition and abundance of the zooplankton community in the surface layers of Trichonis Lake. Bivalve larvae were the dominant prey of A. boyeri during January to May, while copepods and cladocera dominated from June to December.     

Age and growth of the sand smelt, Atherina boyeri (Risso 1810), in the Mar Menor coastal lagoon (SE Iberian Peninsula)

The age and growth of sand smelt, Atherina boyeri (Risso 1810), in the Mar Menor (SE Iberian Peninsula) were studied in samples taken from catches of local fishermen obtained between November 1997 and September 1998. The maximum lengths were 94 mm (FL, fork length) in females and 87 mm (FL) in males. Age determination based on scale readings and validated by length frequency analysis shows that the population has a 3‐year life cycle. Females were significantly longer than males in each of the age classes. Both sexes of the sand smelt grow allometrically (b = 3.113 males; b = 3.043 females) and attain approximately 56.2% of their maximum fork length in their immature first year, after which the annual growth rate drops quickly. The highest growth rate was observed from winter to spring (G_L = 16.01 males 1+; G_L = 11.25 males 2+; G_L = 17.18 females 1+; G_L = 9.62 females 2+). The condition cycles were similar for both sexes, with a minimum in June–July and two maximums in April and November.     

Ecology and exploitation pattern of a landlocked population of sand smelt, Atherina boyeri (Risso 1810), in Trichonis Lake (western Greece)

Age, growth, mortality and exploitation pattern of sand smelt, Atherina boyeri (Risso 1810), in Trichonis Lake (western Greece) were studied from samples taken from catches of local fishermen. Individuals ranged between 44 and 109.53 mm in total length (TL). Age determinations based on scale readings show that the population has a 4-year life cycle. Sand smelt grows allometrically (b=3.18) and relatively rapidly, achieving 52.3% of the growth during the first year; thereafter the annual growth rate drops quickly. The von Bertalanffy growth parameters for all individuals are: L_∞=112.40 mm, k= 0.42 years⁻¹και t_o=−0.40 years. The total mortality rate was Z=1.65 years⁻¹ and the natural mortality rate M=1.07 years⁻¹. The exploitation rate indicates that the population is rather underexploited (E=0.35).     

Phylogenetic relationships of Atherina hepsetus and Atherina boyeri (Pisces: Atherinidae) populations from Greece, based on mtDNA sequences

The genetic divergence and the phylogenetic relationships of six Atherina boyeri (freshwater and marine origin) and five Atherina hepsetus populations from Greece were investigated using partial sequence analysis of 12s rRNA, 16s rRNA and control region mtDNA segments. Three different well divergent groups were revealed; the first one includes A. boyeri populations living in the sea, the second includes A. boyeri populations living in the lakes and lagoons whereas the third one includes all A. hepsetus populations. Fifty-seven different haplotypes were detected among the populations studied. In all three mtDNA segments examined, sequence analysis revealed the existence of fixed haplotypic differences discriminating A. boyeri populations inhabiting the lagoon and the lakes from both the coastal A. boyeri and the A. hepsetus populations. The genetic divergence values estimated between coastal (marine) A. boyeri populations and those living in the lagoon and the lakes are of the same order of magnitude as those observed among coastal A. boyeri and A. hepsetus populations. The results obtained by different phylogenetic methods were identical. The deep sequence divergence with the fixed different haplotypes observed suggests the occurrence of a cryptic or sibling species within A. boyeri complex.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 151–161.     

Histopathology in Atherina boyeri (Pisces: Atherinidae) resulting from infection by Telosentis exiguus (Acanthocephala)

The histopathology developing in the sand smelt Atherina boyeri Risso 1810 from Northern Italy as the result of a natural infection by Telosentis exiguus Von Linstow 1901 (Acanthocephala) was studied and described. Microscope examination of sections of intestinal tissues showed that the parasites did not penetrate through all intestinal layers, and that damage was mostly limited to the epithelium.     

Isolation, characterization and cross-species testing of microsatellites obtained from a sand smelt (Atherina boyeri) genomic library

This study reports the isolation and characterization of 11 polymorphic microsatellites from a sand smelt (Atherina boyeri) genomic library. Enrichment was performed with di-, tri- and tetranucleotide motifs following the FIASCO procedure (fast isolation by AFLP of sequences containing repeats). All loci were found to be in linkage and in Hardy-Weinberg equilibrium. This represents the first microsatellite isolation for the family Atherinidae and the isolated loci were accordingly tested on four additional species of the family: two recognized (A. presbyter and A. hepsetus) and two proposed ('punctata' and 'non-punctata' forms). Moreover their cross-species suitability on Menidia menidia, belonging to the same order but to the family Atherinopsidae, was also tested.     

Age,growth and reproduction of the sand smelt Atherina boyeri Risso, 1810 in Mellah Lagoon (Eastern Algeria)

This aim of this paper was the study of the reproductive biology and growth of the sand smelt, Atherina boyeri, in Mellah Lagoon (Algeria). These data are important for the sustainable exploitation of the stocks of this species. Examined was a total of 1402 Atherina boyeri specimens captured monthly from March 2010 to March 2011, in a population with a 3‐year life cycle. Length–weight relationship was estimated as W = 0.0047 L^3.077 (r² = 0.935) for males and W = 0.0047 L^3.176 (r² = 0.935) for females. Using scales, the von Bertalanffy growth function fitted to back‐calculated size‐at‐age data was Lt = 9.49 [1 ? e^{?0.316 (t + 0.928)}] for males, and Lt = 11.67 [1 ? e^{?0.179 (t + 1.514)}] for females; using otoliths this was Lt = 9.68 [1 ? e^{?0.3 (t + 1.02)}] for males, and Lt = 11.93 [1 ? e^{?0.171 (t + 1.55)}] for females. The growth performance index (Φ) indicated that males (Φ_scales = 3.34, Φ_otoliths = 3.33) grew at the same rate as females (Φ_scales = 3.19, Φ_otoliths = 3.24), with a sex ratio of 1 : 1.6 in favor of females. The reproductive season extended from February to June. Individual length at first sexual maturity was 4.20 cm for 1‐year‐old males and 4.35 cm for 1‐year‐old females.     

Age, growth and mortality of a semi-isolated lagoon population of sand smelt, Atherina boyeri (Risso, 1810) (Pisces: Atherinidae) in an estuarine system of northern Greece

Age, growth and mortality of the sand smelt, Atherina boyeri (Risso, 1810), were studied in the Vistonis estuarine system in northern Greece from February 1989 to August 1990. Overall male : female sex ratio was 1 : 2.5, statistically different from unity. Total lengths ranged between 13 and 105 mm. Age determination based on scale readings showed that the population comprised five age‐groups. Sand smelt grew allometrically (b = 3.22) and rapidly during the first year, achieving 60% of their growth. Growth parameters of the population were: L_∞ = 116.97 mm, K = 0.35 year⁻¹ and t_o = −0.99 years. Growth index ϕ′ was 3.69 of all individuals studied. The mean growth index was significantly lower for the Mediterranean lagoon (ϕ′ = 3.73, SD = 0.1) than for Atlantic populations (ϕ′ = 3.92, SD = 0.06). Total mortality rate was Z = 1.29 year⁻¹ and natural mortality M = 0.95 year⁻¹. Males had a lower life span than females, the latter dominating length classes >60 mm. Exploitation rate of the studied population was E = 0.26, suggesting that stock size might increase and generate improved possibilities for exploitation.     

Age, growth, mortality and sex ratio of sand smelt, Atherina boyeri Risso, 1810 (Pisces: Atherinidae) in the estuary of the Mala Neretva River (middle-eastern Adriatic, Croatia)

The present study investigated the age, growth, mortality and morphometry of the sand smelt, Atherina boyeri, in the Mala Neretva River estuary (mid‐eastern Adriatic Sea). The study of scale annuli showed that the population is up to 4 years of age. However, most sand smelt are in their first and second year; the numbers of older individuals are very low because they migrate upstream and are heavily fished. The von Bertalanffy parameters for the total sample of sand smelt were found to be L_∞ = 13.5 cm, K = 0.37 year^?1 and t₀ = ?0.97. Overall total mortality was estimated at 1.81 year^?1, natural mortality was 0.90 year^?1 and fishing mortality was 0.91 year^?1.     

Some biological parameters of the Mediterranean sand smelt Atherina (Atherina) hepsetus, Linnaeus, 1758 (Pisces: Atherinidae) from the middle eastern Adriatic (Croatian coast)

Data on the length–weight relationship, age, growth, sex ratio and mortality were analysed for the Mediterranean sand smelt, Atherina (Atherina) hepsetus L. (total = 2805; males = 1258; females = 1547) collected in the eastern middle Adriatic island area during the reproductive period (February to April) in 2002. The total length of sampled specimens ranged from 3.8 to 14.5 cm and the weight from 0.28 to 22.39 g. The overall sex ratio was 1.23 : 1 in favour of females, significantly different from the expected 1 : 1 ratio (χ² = 29.76; P < 0.05). All individuals >13.4 cm were females. The oldest collected male and female specimens were 5 years old. The von Bertalanffy growth formula was estimated for females (L_∞ = 15.79 (1−e^{−0.43(t+0.049)}) and males (L_∞ = 15.25 (1−e^{−0.43(t+0.018)}). The power values (b) of the length–weight relationship were very similar for both sexes (b = 3.14) and indicated a slightly allometric growth. The instantaneous rates of mortality for all collected fish were Z = 1.44 year⁻¹; M = 0.94 year⁻¹ and F = 0.50 year⁻¹. The exploitation ratio was E = F/Z = 0.35. The value for M is highly uncertain, however, as well as those values for F and E.     

New record and range extension of the big‐scale sand smelt Atherina boyeri Risso, 1810 (Atherinidae) in the Devegecidi Dam Lake,Tigris River basin,Turkey

The big‐scale sand smelt, Atherina boyeri, is recorded from the Devegecidi Dam Lake in 2016, the first record of this invasive species in the Tigris River basin, with potential to extend to all countries in the Middle East. The smelts were caught with a trawl net mesh size of 6 mm. The captured specimens are described and compared. Records of A. boyeri from Turkish inland waters are summarised from the literature.     

Size-selective overwintering mortality in the sand smelt, Atherina boyeri Risso, and its role in population regulation

The fat laid down as a winter reserve by O-group sand smelt, Atherina boyeri , was found to be size-dependent. The larger, earlier-spawned fish lay down more fat prior to the onset of winter. During the winter the fish do not feed for some 100 days and rely on this fat for energy; laterspawned O-group fish (<59 mm s.l. in November) have insufficient fat reserves and starve to death in a normal winter. This loss of the smallest 46% of the O-group is shown as an increase in the mean size of the O-group over the winter period. Older sand smelt age classes have more than sufficient fat reserves for overwintering. There is thus a clear advantage in spawning early in the season, and any restriction on spawning ground availability at that time will result in overall population regulation. This conclusion supports the hypothesis that the density-dependent control on population size in the sand smelt is a limitation on the number of fish which can spawn at the optimum time.     

Nuclear and mitochondrial phylogenetic analysis of big‐scale sand smelt Atherina boyeri complex in Greece

Genetic differentiation and phylogenetic relationships of big‐scale sand smelt Atherina boyeri specimens from 23 sampling sites in Greece and one from a lake in Turkey were investigated. A total of 2180 base pairs (bp) corresponding to the partial sequence of the mitochondrial gene cytochrome oxidase I (coI), cytochrome b (cytb) and control region, as well as of the nuclear protein‐coding gene rhodopsin (rh), were determined for the 143 specimens studied. Phylogenetic analysis of each gene segment separately and of the combined dataset revealed the existence of three different and well divergent lineages in Greece. The first corresponds to the lagoon form, in which a clear distinction between the Aegean and Ionian Sea was observed. The other two correspond to the punctuated and non‐punctuated marine forms that have been previously reported. The fact that in the present study a population without black spots on the flanks is clustered with the punctuated form and vice versa, however, suggests that differences in colour pattern do not seem to be a sufficient marker to discriminate the two marine forms. In contrast, the presence of a different length insertion between transfer RNA (tRNA) glutamic acid (tRNA^glu) and cytb genes in the lagoon and in one of the two forms of marine populations, and its absence from the rest marine‐form specimens confirms that this character is conserved and capable to be used for distinguishing the different forms. Even though the divergence values among the different forms were high, their phylogenetic relationships were not able to be resolved.     

The biology of Boyer's sand smelt, Atherina boyeri Risso in the Bardawil Lagoon on the Mediterranean coast of Sinai

The present study describes some aspects of the life history of Boyer's sand smelt Atherina boyeri in the hypersaline Bardawil Lagoon on the Mediterranean coast of the Sinai peninsula, Egypt. Monthly samples were collected with a small-mesh experimental beach-seine during the years 1973–1974. Age determinations were based on otoliths readings and length frequency distributions which indicate that the Bardawil Lagoon population consists mostly of 0-age group. The largest recorded fish was 63 mm in standard length (S.L.). Length-weight relationship has been calculated as: W = 13.7 × 10⁻⁶× L ^2.93 where W = weight (g) and L =S.L. (mm). Atherina boyeri mature at the length of 34 mm. Spawning takes place from March to September. The average number of eggs in the ovary of a ripe female at the beginning of the spawning season was found to be 522. Females of all sizes were more numerous than males. In immature fish, less than 34 mm long, females constituted 53% of the population. In larger fish the number of females was higher; in fish over 34 mm long females constituted 64% and in fish over 51 mm—96%. Atherina boyeri in the Bardawil Lagoon feeds on both zoobenthos and zooplankton, mainly amphipods and copepods. Polychaetes, mysidaceans, insects and fish were also represented. Atherina boyeri is the host of endoparasitic Trematoda, Acanthocephala and Nematoda. The examined fish were found to have metacercaria in their mesenteries and liver.     

Sand smelt (Atherina boyeri) migration within the water system of the Camargue,southern France

In the coastal lagoons of Southern France, sand smelt Atherina boyeri, is known as a sedentary species. However part of the sand smelt population living in the brackish water Vaccarès lagoon in the Camargue annually migrates to fresh waters. The movements of sand smelts within the watersystem of the Camargue were studied from 1986 to 1990. Fish traps and fyke nets were set and catches were standardised to Catch Per Unit Effort (CPUE). A Stepwise Multiple Correlation analysis was carried out to link fish abundance with various environmental factors. Between September and November, sand smelts living in the Vaccarès start to colonize fresh waters (drainage canals and then temporary marshes), until March. Spawning occurs from April to June, both in the shallow branches of the canal and in the marshes. From June onwards adults and young-of-the year leave the fresh waters and return to the Vaccarès lagoon where they remain until the next migration. This autumnal migration to freshwater habitats involves mainly fish less than 3 years old, the oldest individuals remaining all year in the Vaccarès. Water level and photoperiod contribute to 20.7% of the variation of CPUE within the drainage canal, while date, water temperature, and rainfall combined, only account for 2.5% of CPUE variations. Date and photoperiod contribute significantly to explaining the patterns of fish migrations between the canal and the marshes. The density of mature sand smelt in the marshes before spawning, varies between 4 and 4346 fish ha^–1. Fry mortality (against number of eggs spawned) over the first two months of life was assessed to vary between 97.5% and 99.9%. Physiological factors such as osmoregulation linked to water temperature are possibly the ultimate factors explaining these unusual annual migrations of sand smelt in the Camargue.