Diplostomiasis in the sand smelt, Atherina presbyter (Cuvier), population at Fawley Power Station

Diplostomiasis, or black spot, is a disease of teleost fish, which results from the encystment of metacercarial larvae of digenean trematodes in the skin of the fish. This parasite occurs on sand smelt, Atherina presbyter , and pout, Trisopterus luscus , at Fawley. Since the debilitating effects of disease or parasitism may be a factor influencing fish impingement, the incidence of black spot in the Fawley sand smelt population has been studied. Fish 3 months old can be infected, and an average of 9% of the population up to 2 years old is infected. There is a rapid size-correlated rise in infection in 2 + fish, associated with their migratory habit. The metacercarial morphology has been examined, and it is tentatively identified as a species of Neodiplostomum . There is a greater settlement of metacercaria on the fins and the eye of the sand smelt than on the scaled parts of the body. No seasonality or change in levels of infection over the years 1977 to 1981 were found. The incidence of the parasite has no effect on the impingement of sand smelt at Fawley; the reasons for this are discussed. Models of the changing rate of infection with migration imply that the population associated with the power station is less infected than surrounding natural populations. The infection rates of diplostomiasis in separate populations of host fish may prove useful in distinguishing the origins of individuals in a mixed impingement on the power station screens.     

Diplostomiasis in sand smelt, Atherina presbyter Cuvier, from the Fleet, Dorset and its use as a population indicator

The population of sand smelt, Atherina presbyter , breeding in the Fleet, Dorset, shows a high infection of diplostomiasis. The population was studied in 1983 to clarify aspects for this parasitic condition previously analysed for the sand smelt population at Fawley, Southampton Water. All age classes showed a higher percentage infection and mean number of metacercaria per fish than at Fawley. Analysis of postlarvae and juveniles showed that infection can occur at 1 week old, and verified the hypothesis that the scales of older fish inhibit cercarial settlement. Circumstantial evidence suggests that Potamopyrgus jenkinsi may be the first vector host for this parasite, and the densities of this species and of nesting little tern colonies would account for the differential infection between these two sand smelt populations. The increase in infection of 2 fish at Fawley cannot be attributed to mixing with the Fleet population, and the different infection levels demonstrate population isolation. High levels of infection are limited to this part of the English Channel: sand smelt samples from around the coasts of the British Isles show minimal infection rates elsewhere and suggest a southerly distribution of the parasite, away from Atlantic oceanic waters.     

Biology of the sand-smelt (Atherina presbyter Valenciennes) around Fawley power station

Past studies of fish impingement at Fawley power station have shown that sand-smelts, Atherina presbyter Valenciennes, are susceptible to impingement and may be a useful species for examining effects of impingement mortalities on population size and structure. A 21 month study of populations in the vicinity of Fawley power station was carried out to obtain data on the biology of the species for future population dynamics modelling studies. Aspects included in the study were growth, sex ratio, reproduction, survival and mortality rates and diet. Differences in apparent and true rates of growth indicated some size-selective mortality towards younger age groups, possibly caused by the power station. A seasonallyoscillating von Bertalanffy growth equation is given to predict mean length-at-age. Most female sand-smelts (73%) matured at the end of their first year of life, fecundities ranging on average from 1394 eggs per female for 1+ group fish to 6872 for III+ fish. The sex ratio was even (1 : 1). An annual survival rate of 10–8% was estimated for mature fish, and the consequent age structure of the population indicates that the bulk of egg production lies with the smaller (1+ group) fish. Since smaller fish are generally more vulnerable to impingement this factor may render populations sensitive to impingement mortalities. Gut content analysis indicated that sand-smelts probably actively select zooplankters from the general plankton when young and, once larger than 104 mm in length, increasingly feed upon natant macrofaunal species.     

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.     

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.     

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.     

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.     

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.     

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.     

The critical swimming speed of Iberian barbel Barbus bocagei in relation to size and sex

The swimming capacity of Barbus bocagei was measured with the critical swimming speed (U_crit) standard test in a modified Bla?ka‐type swim tunnel. Sixty B. bocagei were tested and they exhibited a mean ±s .d . U_crit of 0·81 ± 0·11 m s^?1 or 3·1 ± 0·86 total lengths per second (L_T s^?1). Sex had no effect on U_crit but significant differences were found between the swimming performance of fish with distinct sizes.     

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).     

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.     

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.     

Morphological variation in British Atherinids, and the status of Atherina presbyter Guvier (Pisces: Atherinidae)

A series of morphometric and meristic analyses conducted on specimens of sand smelt, Atherina , from populations around the British Isles, and including classic A. boyeri and A. presbyter forms, has shown that the characteristics variously used in the past to distinguish these two species are invalid. Multivariate analyses showed no significant splitting of the material into two groups which might correlate to these two species; classic A. boyeri and the very large Atlantic coast A. presbyter individuals represent the tails of a continuum of form. From these and published data, it is concluded that the A. boyeri morphology varies under the influence of conditions of temperature and salinity during embryo development, and the isolation of populations maintains comparative morphological distinctions resulting from local selection and random genetic drift.     

Reproduction of Mothocya epimerica (Crustacea: Isopoda: Cymothoidae), parasitic on the sand smelt Atherina boyeri (Osteichthyes: Atherinidae) in Greek lagoons

The reproduction and growth pattern of Mothocya epimerica (Crustacea: Isopoda: Cymothoidae), a protandrous hermaphroditic gill parasite of Atherina boyeri (Osteichthyes: Atherinidae), were investigated in the Mesolongi and Etolikon lagoons. The parasite shows an extensive reproductive period. Gravid females were found between April and November, and juveniles between May and December. M. epimerica grew allometrically (slopes of the total weight-total length regressions were >3). Females were significantly heavier than males. The relationship between number of eggs or mancas larvae (F) and total length (TL) was investigated in gravid female parasites in which the marsupium was still closed; the relationship was clearly curvilinear: F = 0.128TL3.18. The number of eggs or mancas larvae held in the marsupia of females increased proportionally with female length, varying from 39 in an isopod of 6.3 mm length to 158 in one of 8.5 mm length. The average number of eggs or mancas larvae was 76.70 +/- 27.8.     

A multivariate morphometric investigation of Atherina boyeri Risso, 1810 and A. presbyter Cuvier, 1829 (Teleostei: Atherinidae): morphometric evidence in support of the two species

Two recently developed morphometric methodologies, multiple group principal components analysis (MGPCA) and the box truss method of body form transformation are used to re-address whether Atherina boyeri Risso, 1810 and A. presbyter Cuvier, 1829 are morphometrically distinct. The results revealed that morphometric differences are present between A. boyeri and A. presbyter , consistent with expectations of the existence of two species.
Females of the two species were clearly discriminated into two separate groups because the within-group covariances of several characters within populations of each species were different between species i.e., the covariances were heteroscedastic. The occurrence of heteroscedasticity within the data, although statistically invalidating the results of canonical variates anslysis, indicated there to be a large amount of morphological variation between females of the two species. Males were differentiated as a result of differences in body 'shape', particularly the relationship between head 'shape' and body 'shape'.
Several probable reasons are given for the failure of a previous study to differentiate the two species. The data rejects the synonymy of the two species in support of the continued use of the taxa A. boyeri Risso, 1810 and A. presbyter Cuvier, 1829.     

Cardiac function and critical swimming speed of the winter flounder (Pleuronectes americanus) at two temperatures

Using Transonic flow probes and a uniquely designed swimming flume, we directly measured cardiac parameters (Q, cardiac output; SV, stroke volume; and fH, heart rate) in winter flounder (Pleuronectes americanus) before and during critical swim speed (Ucrit) tests at 4 and 10 degrees C. Resting Q, SV and fH averaged 9.8 ml min(-1) kg(-1), 0.5 ml kg(-1) (1.0 ml g ventricle(-1)) and 21 beats min(-1) at 4 degrees C and 15.5 ml min(-1) kg(-1), 0.5 ml kg(-1) (0.95 ml g ventricle(-1)) and 34 beats min(-1) at 10 degrees C (Q10 values of 2.13, 0.91 and 2.35, for Q, SV and fH, respectively). Cardiac output, SV and fH increased by approx. 170%, 70% and 60% at both temperatures during the Ucrit test. However, cardiac parameters generally reached near maximal levels almost immediately upon swimming and remained at these levels until Ucrit (0.65 +/- 0.06 bl s(-1) at 4 degrees C and 0.73 +/ -0.07 bl s(-1) at 10 degrees C). This rapid rise in cardiac function to near maximal levels did not appear to be the result of stress alone, as Q only fell slightly when flounder were swum for 75 min at < 0.4 bl s(-1), speeds at which they appeared to swim comfortably. Our results suggest that both Q and Ucrit have been significantly overestimated in flatfishes, and that "lift-off"/slow swimming is energetically expensive. Furthermore, they show that maximum and resting stroke volume (per g of ventricle) are extremely high in the flounder as compared with other teleosts.     

Field evaluation of a sound system to reduce estuarine fish intake rates at a power plant cooling water inlet

An acoustic deterrent system producing 20–600 Hz sound was used to repel estuarine fishes away from a power station cooling water inlet. During sound emission, total fish impingement decreased by 60%. The avoidance response varied among species from no effect to highly efficient deflection. Lampetra fluviatilis and Pleuronectiformes were less affected by the sound system while the deflection of clupeoid species was particularly effective. Average intake rates of Clupea harengus and Sprattus sprattus decreased by 94·7 and 87·9%, respectively. The results were explained as a function of species‐specific differences in hearing ability and swimming performance. In general, species without swimbladders showed no or a moderate response while intake rates of species with accessory structures increasing the hearing abilities, such as a swimbladder or a functional connection between the swimbladder and the inner ear, were significantly reduced during test periods.     

An electrophoretic investigation of populations of Atherina boyeri Risso, 1810 and A. presbyter Cuvier, 1829 (Teleostei: Atherinidae): genetic evidence in support of the two species

The data obtained using electrophoresis strongly support the specific status of Atherina boyeri Risso, 1810 and A. presbyfer Cuvier, 1829, and thuscontradict the recently proposedsynonymyof the two species. Four populations of A. boyeri and six populations of A. presbyter were assayed for 11 enzymes and general protein using muscle and liver extracts. Eight of the 11 enzymes were shown to be polymorphic at the 95% level. Sixteen loci, encoding 40 putative alleles were consistently resolved in all 10 populations.
The two species were fixed for different alleles at the EST-3 locus. At the G3PDH locus. with the exception of two heterozygotes, all individuals of each species were also homozygous for different alleles. At the PGM locus the common allele was unique to each species.
The mean Nei's genetic distance ( ), over all loci, calculated between populations of A. boyeri (= 0.10 ± 0.06); between populations of A. presbyter ( = 0.02 0.02) and between populations of A. boyeri and A. presbyter ( = 0.42 0.09) indicated the separateness of the two species.
UPGMA cluster analysis based on genetic distances produced a dendrogram whose principal dichotomy resulted in the formation of two clusters. The ordination of populations in the UPGMA cluster analysis strongly reflected the geographic distribution of populations in both species.     

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.