The growth of the common two-banded seabream, Diplodus vulgaris (Teleostei, Sparidae), in Canarian waters, estimated by reading otoliths and by back-calculation

The yearly nature of increment formation in the otoliths of 1–9‐year‐old seabream, Diplodus vulgaris (E. Geoffrey Saint‐Hilaire 1817), from the Canary Islands was validated. The marginal increment method showed that the opaque rings were formed in summer, and the translucent rings in winter. The Brody Proportional Hypothesis and the power length–radius relationship used to back‐calculate the growth trajectories of D. vulgaris showed that this growth model could provide reasonable growth estimates in this species. Growth back‐calculation and growth estimates obtained by direct otolith readings were similar. Data on age and size used to estimate the parameters of the von Bertalanffy growth model for D. vulagris from the Canary Islands showed that males and females had similar growth rates.     

Immune response of turbot, Psetta maxima (L.) (Pisces: Teleostei), to formalin-killed scuticociliates (Ciliophora) and adjuvanted formulations

The increasing frequency of scuticociliatosis in turbot culture has stressed the need of knowledge on the immune responses to these parasites, for further developing of prevention and control strategies. The immune response of turbot to killed parasites, alone (Ag) or in combination with Montanide ISA 763A (MON), was studied in a laboratory-scale experiment. The variations of several innate immune factors and the antibody response were analysed in immunized vs. non-immunized fish at different times after immunization, and also after a challenge with live ciliates. Amongst innate immune factors, serum lysozyme increased progressively in all inoculated groups. Differences in innate immune factors in Ag and Ag-MON fish with respect to controls were mainly evidenced after challenge, especially for serum complement. Serum antibody levels increased in immunized fish after booster and particularly after challenge. In addition, certain protection was obtained for immunized groups compared to controls or to fish receiving MON alone, and the levels of specific antibodies were also the highest in immunized groups. The obtained information could be useful for further design of immunoprophylactic formulations against scuticociliatosis.     

Absence of population structure of turbot (Psetta maxima) in the Baltic Sea

We found low, albeit significant, genetic differentiation among turbot (Psetta maxima) in the Baltic Sea but in contrast to earlier findings we found no evidence of isolation by distance. In fact temporal variation among years in one locality exceeded spatial variation among localities. This is an unexpected result since adult turbot are sedentary and eggs are demersal at the salinities occurring in the Baltic. Our findings are most likely explained by the fact that we sampled fish that were born after/during a large influx of water to the Baltic Sea, which may have had the consequence that previously locally and relatively sedentary populations became admixed. These results suggest that populations that colonize relatively variable habitats, like the Baltic, face problems. Any adaptations to local conditions that may build up during stable periods may quickly become eroded when conditions change and/or when populations become admixed. Our results indicate that the ability of turbot to survive and reproduce at the low salinity in the Baltic is more likely due to phenotypic plasticity than a strict genetic adaptation to low salinity.     

Allozyme variation in turbot (Psetta maxima) and brill (Scophthalmus rhombus) (Osteichthyes, Pleuronectoformes, Scophthalmidae) throughout their range in Europe

Two species of coastal flatfish (brill and turbot, Scophthalmidae) were analysed electrophoretically at 17 common enzymatic loci in samples taken from 11 sites representing the species ranges in Europe. Brill showed a mean heterozygosity ( H ) of 0·11 while that of turbot was 0·02. The virtual absence of genetic diversity in turbot is probably due to a very low evolutionary rate, and provides little evidence for population substructure even if various signs indicate the possibility of a hidden differentiation (presence of the taxon maoetica in the Black Sea and differentiation of a species-specific cestode parasite on either side of the Strait of Gibraltar). On the other hand, the weak geographic structure in brill seems to result from rapid recolonization following the last ice age.     

Genotyping and pathogenicity of viral hemorrhagic septicemia virus from free-living turbot (Psetta maxima) in a Turkish coastal area of the Black Sea

Viral hemorrhagic septicemia (VHS) is one of the most serious fish viral diseases for cultured rainbow trout (Oncorhynchus mykiss), although VHS virus (VHSV) seems to be ubiquitous among marine fishes. In the present study, VHSV isolation was performed with free-living and cultured turbot (Psetta maxima) in the Trabzon coastal area of the Black Sea to evaluate participation of VHSV in mass mortalities of seed-produced turbot larvae. VHSV was detected in 14 of 66 free-living spawners (positive ratio, 21.2%), 1 of 65 free-living immature fish (1.5%) and 7 of 40 cultured brood stock (17.5%), respectively. Based on a partial glycoprotein gene nucleotide sequence, Turkish VHSV isolates were classified into the class I-e of genotype I and were the most closely related to the GE-1.2 isolate (>98% identity), which was found >20 years ago in Georgia. Thus, it was revealed that Turkish VHSV isolates were not introduced from European countries, it could be an indigenous type of VHSV distributing in the Black Sea environment. In pathogenicity tests, the Turkish isolates did not induce mortality in turbot larvae and rainbow trout fingerlings. Mass mortalities at a rate of approximately 90% occurred in turbot larvae produced by experimental seeding, although VHSV was not detected in any dead fish. Thus, it was concluded that mass mortality in the seed-produced turbot larvae was not caused by VHSV infection.     

Age, growth and food composition of Scorpaena porcus (Linnaeus, 1758) in the southeastern Black Sea

Samples of 525 Scorpaena porcus (Linnaeus, 1758) were collected from the southeastern Black Sea between January 2002 and May 2003 for information on age, growth, length–weight relationships and stomach contents. Total length of sampled fish ranged from 4.6 to 22.9 cm and total weight from 1.3 to 220 g. The sex ratio (1 : 1.61) was biased toward females (P < 0.05). Positive allometric growth was determined in the collected samples. The length–weight relationship for all individuals was described by the parameters a  = 0.0149 and b  = 3.09, with r ² = 0.99. The sample was composed of five age-classes (0–7 years). Three growth models were used to identify the growth characteristics: von Bertalanffy,     ; logistic,     ; and Schnute and Richards,     . Among these, the Schnute and Richards model was best fitted to the data as     The diet was composed of Carcinus mediterraneus (18.2%), Crangon crangon (12.1%), unidentified crab species (10.6%), Gobius sp. (4.6%), Palaemon sp. (4.5%), Macropipus sp. (4.5%), Engraulis encrasicholus (1.5%), Gastropoda (1.5%), and unidentified remains (34.9%).     

Age and growth of stargazer (Uranoscopus scaber L., 1758) in the southeastern Black Sea

A sample of 346 Uranoscopus scaber (L., 1758) was collected from the southeastern Black Sea between January 2002 and May 2005 in order to provide information on age, growth, length–weight relationship, and stomach contents of this species. Total length and total weight of sampled fish ranged from 5.2 to 21.9 cm and from 2.0 to 182.5 g, respectively. The sex ratio (1 : 1.98) was biased toward females (P < 0.05). Isometric growth was determined in the population. Length–weight relationships for all individuals were described by the parameters: a = 0.0167, b = 3.00, with the r² = 0.99. The population was composed of five age‐classes (I–V years). The von Bertalanffy growth parameters (±SE) and confidence limit (CL, 95%) for the entire population were: L_∞ = 26.31 ± 0.838 cm (CL: 24.66–27.96), k = 0.339 ± 0.023 1/year (CL: 0.294–0.385), and t_o = 0.087 ± 0.0346 year (CL: 0.019–0.155) (r² = 0.96). Growth performance index (Φ) was 2.37. The diet was composed of Gobius sp. (2.2%),Trachurus trachurus (2.1%), Merlangius merlangus euxinus (4.3%) and unidentified fish species (17.4%); 39.1% were unidentified remains.     

Feeding habits of horse mackerel, Trachurus trachurus (Linneaus, 1758), from the central Adriatic Sea

The feeding habits of the horse mackerel, Trachurus trachurus, from the central Adriatic Sea were investigated with respect to fish size and season. Stomach contents of 1200 specimens 12.9–37.6 cm total length (TL) taken at monthly intervals (January–December 1995) were analyzed. Of the total number of stomachs examined, 597 were empty (49.7%). This percentage varied significantly with season; the maximum number of empty stomachs was observed during January (80%) and February (82%) and a minimum number observed during July (15%) and August (19%). A total of 30 different prey species belonging to five major groups: Crustacea (Euphausiacea, Mysidacea, Decapoda), Cephalopoda, and Teleostei was identified in the stomach contents. Euphausiids were the most important ingested prey in all seasons as well as in small‐ and medium‐size classes (<28 cm TL). Two species of euphausiids, Nyctiphanes couchii (%IRI = 36.0) and Euphausia krohni (%IRI = 12.9), were the most frequent prey. The proportion of teleosts in stomach contents increased with the increasing size class of horse mackerel and was 15.5% IRI in >30 cm TL individuals. The mean weight of stomach contents increased significantly for fish larger than 24.1 cm TL, while the mean number of prey items significantly declined in the large‐size classes.     

Age, growth and reproduction of the black scorpionfish, Scorpaena porcus (Pisces, Scorpaenidae), on the Black Sea coast of Turkey

Age, growth and reproduction of the black scorpionfish, Scorpaena porcus were studied in specimens from the coast of the Sinop Peninsula (Black Sea) between March 2002 and April 2003 in order to characterize these population parameters in comparison to specimens from populations of nearby regions. A total of 1086 specimens was captured by beam trawl at the depths between 0 and 30 m. The total number of females (510) was significantly higher than that of males (373). Total length of males and females ranged between 5.7 and 23.6 cm, and 4.9 and 31.7 cm, respectively. The length–weight relationship showed a positive allometric growth. Females grew faster and reached a larger size at age than males ( L _∞ = 111.9 cm, K  = 0.035 year⁻¹, φ' = 2.64 for females, and L _∞ = 74.6 cm, K  = 0.054 year⁻¹, φ' = 2.49 for males). The age range estimated was up to 8 years for females and 5 years for males. Reproduction likely occurs between June and September. Sex ratio varied greatly with season, perhaps indicating different seasonal migratory patterns in adults of different sex. An inverse correlation between gonadosomatic index (GSI) and hepatosomatic index (HSI) was evident during the reproduction seasons. The mean size at first sexual maturity was 17.5 cm TL for females, and 16.7 cm TL for males.     

Effect of diet composition and lysine supply on growth and body composition in juvenile turbot (Psetta maxima)

A 10-week feeding trial was conducted to study the effect of feeding level and dietary lysine concentration on growth, protein and lysine retention, and body composition in juvenile turbot. Maintenance requirement for lysine and the efficiency of lysine utilisation were determined as well. Two experimental diets were formulated based on fishmeal or wheat gluten as main protein sources, containing 6.4 g (Diet A, control) and 4.5 g lysine per 100 g CP (Diet B), respectively. Diets were fed once daily at six feeding levels (per day 0.3%, 0.6%, 0.9%, 1.2%, and 1.5% of body weight [BW] and ad libitum) to a total of 432 fish of 48 g initial BW. No differences in the growth parameters were observed between diets at the same feeding level, except a lower feed to gain ratio (p < 0.05) at the highest feeding level at Diet B. Whole-body composition was not affected by diet, whereas muscle protein concentration was significantly lower for fish fed Diet B. Amino acid concentration in whole-body protein was affected by dietary treatment and fish fed Diet B showed lower concentrations of all essential amino acids. In fish muscle protein, lysine, methionine, leucine, isoleucine, and valine concentrations were significantly lower in Diet B. Efficiency of lysine utilisation for growth (k_lys) was determined by linear regression analysis and amounted for 0.69 for Diet B. The maintenance lysine requirement defined at zero lysine retention was 6.5 mg · kg^?0.8 · d^?1. Lysine intakes at zero protein retention were 13.0 mg and 12.9 mg · kg^?0.8 · d^?1 for Diet A and B, respectively. Growth and nutrient retention were similar for both diets and, therefore, a lysine deficiency in Diet B did not occur. In conclusion, a proportion of 330 g wheat gluten per kg feed did not influence growth performance and maintenance requirement for lysine in juvenile turbot. However, the effect of diet composition on the amino acid profile of body protein might be relevant for the derivation of the amino acid requirement from protein retention.     

Synaptonemal complex analysis in spermatocytes and oocytes of turbot, Scophthalmus maximus (Pisces, Scophthalmidae).

A surface-spreading synaptonemal complex (SC) technique was used to analyze spermatocytes and oocytes of turbot (Scophthalmus maximus) to visualize the process of chromosome synapsis. The total SC length was 205 +/- 12 microm in males and 172 +/- 29 microm in the only female analyzed. A representative SC karyotype of turbot was obtained. Each SC showed lateral elements of equal length. No bivalent exhibiting atypical synaptic behaviour that could be associated with heteromorphic sex chromosomes was observed, either in males or in the female. The DNA content of turbot was evaluated in eight individuals of both sexes by flow cytometry analysis. The 2C mean DNA content of turbot (1.308 +/- 0.009 pg/cell) was among the lowest observed within fishes. No statistical differences in DNA content were revealed between the sexes [Wilcoxon/Mann-Whitney test; P(W(x) = 0.243)]. The SC/DNA content ratio observed in turbot was the highest reported to date in bony fishes (Osteichthyes).     

Morphological,immunohistochemical and ultrastructural characterization of the skin of turbot (Psetta maxima L.)

This study was undertaken to identify the normal morphologic, immunohistochemical and ultrastructural features of skin of the turbot (Psetta maxima L.). In the turbot skin, three morphologically distinct layers were identified: epidermis, dermis and hypodermis. The epidermis was non-keratinizing, stratified squamous epithelium that varies in thickness from 5 to 14 cells and 60 to 100 μm in size. Goblet cells were seen randomly distributed between malpighian cells in the epidermal layer. These mucous cells were mainly located in the upper third of the epidermis and displayed a spherical to elongated morphology. Dermis was divided in two well-differentiated layers, the superficial stratum laxum and the deeper stratum compactum. Hypodermis was a loose layer mainly composed by adipocytes but we could observe variable amounts of fibroblast, collagen and blood vessels. In turbot two pigmentary layers could be identified: the pigmentary layer of dermis was located between basement membrane and dermis and the pigmentary layer of hypodermis immediately above the muscular layer. Three different types of chromatophores were present: melanophores, iridophores and xanthophores. The main differences observed between groups of fish with different colouration were in the amount of melanophores and xanthophores. The purpose of this article is to provide an overview of normal cutaneous biology prior to consideration of specific cutaneous alterations and diseases in turbot.     

Age, growth and mortality of brown comber, Serranus hepatus (Linnaeus, 1758) (Pisces: Serranidae), in the eastern Adriatic (Croatian coast)

Age, growth and mortality were analysed for brown comber, Serranus hepatus, collected in the eastern Adriatic from May 2002 to June 2003. Fish aged 2–7 years were present in the samples. Growth in length including both sexes was expressed using the von Bertalanffy equation, L_∞ = 14.82, K = 0.217 and t₀ = −1.672. Age class 2, ranging in length from 5.8 to 9.0 cm TL, dominated the sample (29.3%). Total and natural mortality were Z = 1.73 year⁻¹ and M = 0.63 year⁻¹, respectively. The exploitation rate, E = 0.64, revealed a high fishing pressure on the stock in the studied area.     

Age and growth of Trisopterus luscus (Linnaeus, 1758) (Pisces,Gadidae) off the coast of Asturias

The age and growth of an Asturian population of the bib Trisopterus luscus L. were studied based on 990 bibs from monthly catches from October 1986 until October 1988.Using the estimates of age taken from otolith readings, it was possible to construct a growth curve for the whole range of ages and demonstrate that most growth takes place during the first two years of life. The maximum age was found to be 5 years. The largest fish caught during the investigation measured 430 mm in standard length.The different growth rates of males and females show that in most cases the mean standard length of females was equal to or greater than that of the males.     

Age and growth of pearly razorfish,Xyrichtys novacula (Linnaeus 1758), in the central Mediterranean Sea

Age and growth of pearly razorfish Xyrichtys novacula (Labridae) were determined in specimens caught on sandy bottoms by surrounding nets and lines (depth range 5–30 m) between January 2000 and December 2002. The study location was in the central Mediterranean Sea. For this purpose the annual growth increments (annuli) in sagittae were analysed. A total of 470 individuals of X. novacula, ranging from 49 to 200 mm TL (total length), were examined. Conversion between total length and standard length was calculated and represented by the relationship: . Edge analysis on otoliths was carried out to validate seasonality deposition. Seven age‐classes were determined from 0+ to 6+. The linear relationship between maximum otolith length (OL) and TL was summarized in the equation . The estimated parameters of the von Bertalanffy growth function were L = 175.05 mm, k = 0.80 year^?1, t₀ =?0.73 years and the growth performance index calculated as (Φ = 2.39). The length–weight relationship W = 0.0139 TL^2.9326 described an isometric growth for the species in this area.     

Age and Growth of the Black Scorpionfish Scorpaena porcus Linnaeus, 1758 (Scorpaeniformes: Scorpaenidae) under Anthropogenic Pressure in the Black Sea

Journal of Ichthyology - Age structure and growth dynamics are examined for the black scorpionfish Scorpaena porcus Linnaeus, 1758, from three sites characterized by different levels of pollution:...     

Quantitative and qualitative evaluation of iNOS expression in turbot (Psetta maxima) infected with Enteromyxum scophthalmi

Enteromyxum scophthalmi is the causative agent of turbot enteromyxosis, an intestinal parasitisation that produces severe desquamative enteritis leading to a cachectic syndrome and eventually the death. It is well known the importance of the innate immune response against parasites in fish, with the release of antimicrobial substances such as reactive oxygen and nitrogen species, produced by the inducible nitric oxide synthase (iNOS). This enzyme is mainly found in phagocytes, but also in structural cells from the intestinal mucosa. The aim of this study was to characterize iNOS in intestine and lymphohaematopoietic organs (spleen and anterior kidney) of turbot by means of immunohistochemistry in order to assess the possible changes of this enzyme through the infection. The presence of the enzyme was evaluated in control and E. scophthalmi-infected turbot. The results showed immunoreactivity in the apical border of enterocytes and mild staining of goblet cells in both control and infected turbot although it was more evident and widespread in infected turbot compared to control. Moderate numbers of iNOS+ cells were present in the lamina propria-submucosa of fish which presented moderate and severe inflammatory infiltrates at this level. In spleen and kidney, iNOS+ cells were scattered through the parenchyma and, in severely infected fish, tended to be allocated near the vascular structures and melano-macrophage centres. The number of positive cells at the lymphohaematopoietic organs was significantly higher in infected turbot and increased as infection progressed. The increase in the expression of iNOS in the tissues of E. scophthalmi-infected turbot was more evident in individuals with severer lesions. The measurement of the levels of iNOS during turbot enteromyxosis reveals a possibly delayed response that would not able to eliminate the parasites but would exacerbate mucosal injury.     

1H-NMR and (31)P-NMR analysis of energy metabolism of quiescent and motile turbot (Psetta maxima) spermatozoa

31P-NMR and (1)H-NMR were used to monitor changes of several compounds with high-energy bonds and metabolites prior to and after the initiation of motility of turbot spermatozoa (Psetta maxima). The obtained (31)P-NMR spectra revealed the presence of phosphomonoesters, phosphodiester, intracellular inorganic phosphate (Pi), phosphocreatine (PCr), and free nucleotide triphosphate. Following the activation of motility, the di- and tri-phosphate nucleotides, PCr, phosphomonoesters levels dropped while Pi levels increased. A significant increase of lactate was also seen at the end of the swimming phase. The compositions of seminal fluid and urine were also determined. Lipoproteins, formic acid, amino acid, and citric acid were detected in seminal fluid. Dimethyl amine, trimethylamine, and trimethylamine oxyde were found in urine. These data suggest that at least a part of the energy required during the swimming phase results from anaerobic fermentation and oxidative phosphorylation. J. Exp. Zool. 286:513-522, 2000.