Brill Scophthalmus Rhombus Research Articles

Characterization of Aliivibrio fischeri strains associated with disease outbreak in brill Scophthalmus rhombus.

Three bacterial isolates were recovered from a disease outbreak with high mortality affecting brill Scophthalmus rhombus (Linnaeus, 1758). Moribund fish showed no external signs of disease, but plentiful haemorrhages were observed in liver. On the basis of phenotypic and genotypic characterization, the isolates were identified as Aliivibrio fischeri. The phenotypic profile of the isolates was basically similar to that of the type strain of this species, although some discrepancies were observed, mainly in the BIOLOG GN profile. The main cellular fatty acids of strain a591 were also consistent with this species. The highest 16S rDNA sequence similarities were recorded with the type strain of A. fischeri (99.07%); other Aliivibrio species showed similarity values below 96%. The highest sequence similarities with gyrB, rpoD and recA genes were also recorded with A. fischeri type strain (99.31, 98.99 and 95.29% similarity, respectively). DNA-DNA hybridization assays confirmed that these isolates belong to A. fischeri; levels of DNA relatedness were 73.5 to 86.2% with isolate a591 (reciprocal values of 86.9 to 99.04%). Finally, a virulence evaluation of the isolates using Senegalese sole fry was also performed; significant mortalities (100% mortality within 5 d) were recorded by intraperitoneal injection, but only with high doses of bacteria (2 × 106 cfu g-1 body weight).

The timing of early life events and growth rate estimates of age‐0 year group brill Scophthalmus rhombus along the west coast of Ireland

The timing of spawning and hatching, larval durations and growth exhibited by juvenile brill Scophthalmus rhombus captured along the Irish west coast were estimated using otolith microstructure analysis. Scophthalmus rhombus were estimated to have hatched between February and May, with fish settling onto nursery grounds between March and June. Fish collected later on in the season exhibited higher otolith growth rates in comparison to earlier collected fish. This is the first study to describe the early life history of a commercially valuable but understudied flatfish species.

Sperm production and quality in brill Scophthalmus rhombus L.: relation to circulating sex steroid levels

The aims of the present study were to characterize sperm quality and to quantify seasonal changes in sexual hormone (testosterone [T], 11-ketotestosterone [11-KT] and 17,20β-dihydroxypregn-4-en-3-one [17,20β-P]) levels in male brill (Scophthalmus rhombus) plasma, as well as to test a more intensive sampling strategy to establish relationships between sex steroid levels and sperm production parameters. Sperm concentration ranged from 0.5 to 3.1 × 10(9) spermatozoa mL(-1), and changes in sperm quality parameters depending on sampling date were observed. Plasma sexual steroid levels remained high and changed in parallel during the spawning season and afterwards decreased to very low levels in summer. The analysis of annual changes of 11-KT and T ratios suggests that 11-KT can be the main circulating androgen for stimulating spermatogenesis in S. rhombus and that T could be involved in the beginning of spermatogenesis through the positive feedback on brain-pituitary-gonad axis. Finally, daily 11-KT and T levels showed similar patterns of variation in males sampled, whereas 17,20β-P amounts showed somewhat opposite trends. These differences could be related with the different role of androgens and progestin during the spermatogenesis.

The feeding ecology of 0 year-group turbot Scophthalmus maximus and brill Scophthalmus rhombus on Irish west coast nursery grounds

On sandy beach nursery grounds along the west coast of Ireland, 0 year-group turbot Scophthalmus maximus were found to consume six types of crustaceans, in addition to polychaetes. The 0 year-group brill Scophthalmus rhombus fed almost exclusively on mysids, even though nine taxonomic prey groups were identified in the sediment across the investigated beaches. Both species avoided non-motile organisms such as gastropods and bivalves, which were present in high abundances in the sediment and their growth and condition was not significantly related to the quantity or type of prey consumed, temperature or salinity. A high incidence of feeding was detected for both species over the duration of the study, suggesting that food was not limiting on west of Ireland nursery grounds. Temporal partitioning of settlement was detected between S. maximus and S. rhombus, indicating that inter-specific competition for food does not occur between these two flatfish species on west of Ireland nursery grounds.

Diet and niche overlap of southern populations of brill Scophthalmus rhombus and turbot Scophthalmus maximus

The diets of adult brill Scophthalmus rhombus and turbot Scophthalmus maximus from the Portuguese coast relied mostly on fishes. There was a higher diversity of food items compared to their northern counterparts, and several of the identified prey are the first records of these species, including a brown alga, echinoderms, nematodes, oligochaetes, gastropods, bivalves and various fish species. The diet of the two species was significantly different and niche overlap was low.

Reduction of flatfish habitat as a consequence of the proliferation of an invasive mollusc

Coastal bays provide habitats for juveniles and adults of many marine species. Mont Saint-Michel Bay (MSMB, France) hosts a highly diversified fish community and constitutes one of the most important nursery grounds for many commercially exploited marine species, such as sea bass, flatfish, clupeids and rays in the English Channel. Besides, MSMB also suffers from the massive invasion of an exotic mollusc, the American slipper-limpet ( Crepidula fornicata, L.). This species arrived four decades ago and now represents the main filter-feeder biomass in the bay (150 Mt), an order of magnitude larger than local farmed and natural shellfishes. Recent analyses underlined the impact of this small gastropod on the trophic structure of this bay and its negative influence on juvenile sole densities in the nursery grounds. The present study uses a geostatistical approach to explore the effect of the extension of the slipper-limpet on flatfish (common sole Solea solea, L.; plaice Pleuronectes platessa, L.; brill Scophthalmus rhombus, L. and flounder Platichthys flesus, L.) spatial distribution. Data collected during survey of the MSMB at the end of the 1970s and three decades later have been used to build interpolated maps of (1) slipper-limpet and (2) flatfish spatial distributions. Slipper-limpets were concentrated in a small area, in the western part of the MSMB, in the 1970s while today they occupy half of the bay. This rapid proliferation led to the decrease of available surface for flatfishes, which previously occupied the whole bay and are now restricted to its eastern part. The present study highlighted that the negative influence on fish habitat in MSMB is apparently more related to changes in the substratum than to trophic interactions. This invasion has possible consequences on flatfish population renewal at a large scale and may also damage other benthic or demersal species, such as rays.

Variation in fin ray counts of 0-group turbot ( Psetta maxima) and brill ( Scophthalmus rhombus) on the west coast of Ireland: 2006–2009

Recently settled turbot Psetta maxima and brill Scophthalmus rhombus are difficult to distinguish, as they are almost identical in appearance and lack the diagnostic adult characteristics. Fin ray counts, which can be used as an aid in the identification of flatfish juveniles, are reported to show some overlap between turbot and brill. 0-group flatfish were collected from sandy beaches along the west coast of Ireland by beach seining in 2009. When counted and plotted, the dorsal and anal fin ray counts clearly separated the specimens into two groups. The two groups were assumed to be brill and turbot on the basis of literature data, suggesting higher dorsal and anal fin ray counts occur in brill. This confirmed that fin ray counts can probably be used as a diagnostic tool in these 0-group flatfish from west of Ireland waters. Additionally, temporal and spatial variability in fin ray counts was also revealed in the present study, emphasizing that regional difference need to be taken into account when using this diagnostic method.

Total lipid and fatty acid composition of brill eggs Scophthalmus rhombus L. relationship between lipid composition and egg quality

The present study examines the total lipid (TL) and fatty acid (FA) composition in eggs of brill Scophthalmus rhombus L. and the possible relationships with their quality parameters. Wild broodstocks were caught and maintained in captivity until eggs were collected. A lipid characterization of each egg batch was conducted in TL, lipid classes (LC) and FA of TL. The TL content was lower than the values reported for other flatfish species, showing high levels of sterol esters (SE). High viability rates were related to higher lipid reserves. Higher cholesterol (CHO) was linked to higher egg viability, whereas SE could have an opposite effect. Comparison of female quality showed that lipid composition was more related to egg batches than to individual females. However, multivariate analysis did not show a clear correlation between lipid composition and brill egg quality, neither as individual components nor as a whole profile of LC or FA. Our results suggest that some lipid components (phosphatidylcholine, CHO, SE, monounsaturated, eicosapentaenoic acid) could be related to differences in spawning quality, although these were not the only factors involved in these differences. Thus, these lipid components could be considered to be descriptors of the differences found in the rates of brill quality.

Larval organogenesis of flatfish brill Scophthalmus rhombus L: Histological and histochemical aspects

The present tabular overview of organogenesis in larvae of the flatfish brill Scophthalmus rhombus (L.) provides valuable information on its structural status during ontogeny, and it can be useful for establishing the functional systemic capabilities and physiological requirements of larvae for optimal welfare and growth. The organogenesis of the brill larvae was studied during the first month of larval life by means of zootechnical, histological, and histochemical approaches. Based upon its feeding mode, and analysing the main morphohistological characteristics of the organs and systems, larval development in brill was divided into four stages from hatching: Stage 1: 0–1 days after hatching (DAH); Stage 2: 2–9 DAH; Stage 3: 10–22 DAH and Stage 4 from 23 DAH onwards. As in most marine fish species, brill larvae at hatching had an undifferentiated digestive tract composed of monostratified epithelium cells, each containing a basal nucleus and evident apical microvilli. At the beginning of stage 2, both the mouth and the anus opened in conjunction with the differentiation of the digestive tract. During stages 2 and 3, the digestive tract differentiated and buccopharyngeal cavity, oesophagus, incipient stomach, and anterior, mid- and posterior intestine became distinguishable. At this time, prey capture began and the digestive processes continued to develop (e.g. gut mucosa folds, lipid infranuclear vesicles and protein supranuclear inclusions). The first taste buds appeared at the onset of the exotrophic stage, at 8 DAH, while the first pharyngeal and mandibular teeth were apparent at 4 DAH. Histological and histochemical observations suggest that digestive tract development of the brill larvae, involving the presence of functional liver (glycogen lipids), exocrine pancreas (proteins) and gall bladder, enabled early larvae (from 4 DAH) to ingest, digest, and assimilate the first exogenous food, even before endogenous reserves were completely resorbed. The appearance of the digestive mucous cells (from 3 DAH), containing neutral and/or acid mucosubstances, and the functional gastric gland differentiation (23 DAH) resembled such developments in other flatfish species. The most critical ontogenetic events occurred at stage 2. Primordial gills were detected at 2 DAH while gill filament, vascular structures, and lamellae differentiated from 6 DAH. At the beginning of stage 2, four defined cardiac cavities (sinus venosus, atrium, ventricle, and bulbus arteriosus) were discernible. The primordial swim bladder was differentiated from the dorsal wall of the digestive tube at 2 DAH and at this time renal tubules between interstitial kidney tissue were detected. Endocrine elements (Langerhans islets and thyroid follicles) were also evident at stage 2. From stage 3 onwards, most organs essentially exhibited an increase in tissue structure number and size.

Reproductive performance and seasonal plasma sex steroid and metabolite levels in a captive wild broodstock of brill Scophthalmus rhombus L.

14 paginas, 9 figuras, 2 tablas. The definitive version is available at www.blackwell-synergy.com

Feeding ecology of juvenile flatfishes of the surf zone of a sandy beach

Prey items of 0‐ and 1‐group plaice Pleuronectes platessa, sole Solea solea, brill Scophthalmus rhombus, turbot S. maximus and dab Limanda limanda of the surf zone of a Belgian sandy beach, included hyperbenthic (e.g. mysids), endobenthic (e.g. polychaetes) and epibenthic (e.g. shrimps) species. Little dietary overlap was observed. If diet overlap did occur, it mainly involved prey species that are dominant in the surf zone of Belgian beaches, such as shrimps and mysids. These results suggest an opportunistic utilization by flatfish of the available food resources in surf zone ecosystems. Also, two strategically different feeding habits could be distinguished between the five flatfish species. Turbot and brill mainly fed on large, highly mobile prey (e.g. fish, mysids) and had a rather narrow prey spectrum, whereas plaice, dab and sole ate more benthic prey (e.g. polychaetes) and had a broader prey spectrum.