Characterization of microsatellite loci for the redbanded seabream,Pagrus auriga (Teleostei,Sparidae)

The redbanded seabream Pagrus auriga (Teleostei, Sparidae) is a species of a high commercial value in Spain. There is currently little information available about the genetic characteristics of both wild and cultured populations. In this survey, we have developed eight polymorphic microsatellites for the redbanded seabream using an enriched genome library protocol. All of them were polymorphic in the 64 individuals tested, 22 of which were wild specimens, and 42 were individuals from a captive reproductive broodstock. These markers can potentially be useful tools for use in population genetic studies.     

Reproduction, age, growth and mortality of axillary seabream, Pagellus acarne (Sparidae), from the Canarian archipelago

Axillary seabream Pagellus acarne (Risso 1826) caught off the Canary Islands from January 1991 to December 1994 were studied. The length range of the catches was between 11 and 31 cm, with a modal distribution between 17 and 21 cm. The overall ratio of males to females was 1:1.74. Males were observed up to a length of 24 cm. Hermaphrodites were recorded at lengths between 15 and 23 cm. The species was characterized by protandric hermaphroditism. The reproductive season extended from October to March, with a peak in spawning activity in December–January. The size at sexual maturity was 15.8 cm total length (2 years old) for males and 19.4 cm total length (3 years old) for females. The total length–total weight relationship for the entire population is described by the parameters a = 0.0068, and b = 3.2401. Otolith age readings showed that the population exploited consisted of 10 age groups (1–10 years), including a very high proportion of individuals between 1 and 4 years old. The von Bertalanffy growth parameters for all individuals were L_∞ = 32.98 cm, k = 0.22 years⁻¹, and t₀ = −0.87 years. Males grew comparatively slower than females. The instantaneous rates of mortality for all fish were Z = 0.96 years⁻¹, M = 0.30 years⁻¹, and F = 0.66 years⁻¹. The exploitation ratio and the length at first capture were, respectively, E = 0.69 and LC₅₀ = 16.1 cm. The stock is overexploited, therefore measures such as closed seasons or changes in fishing patterns would be desirable to safeguard the spawning stock and recruits.     

Basic characteristics of the population dynamic and state of exploitation of Moroccan white seabream Diplodus sargus cadenati (Sparidae) in the Canarian archipelago

Moroccan white seabream Diplodus sargus cadenati (n = 603) were caught off the Canary Islands from April 2000 to March 2001. Total length ranged from 46 to 404 mm. The subspecies was characterized as being dygynous with partial protandry. Overall ratio of males to females was 1 : 2.9. The reproductive season extended from December to May, with a peak in spawning activity in January–February. Fifty per cent maturity was reached at 201 mm total length in males and 216 mm in females. The length–weight relationship for all individuals was described by the following parameters: a = 0.000023, and b = 2.96, when length is given in millimeters and weight in grams. Fish of 0–12 years in age were found. The von Bertalanffy growth parameters for the entire population were: L_∞ = 467 mm, k = 0.143 year^?1 and t₀ = ?2.14 year. Growth parameters differed between males and females. For all fish, instantaneous rates of mortality were Z = 0.68 year^?1, M = 0.31 ± 0.6 year^?1 and F = 0.37 ± 0.6 year^?1; the exploitation ratio was E = 0.54 ± 0.9. Length at first capture for all individuals was 173 mm. The stock exploited above is an assumed optimum.     

Reproductive characteristics of the benthic coastal fish Diplodus vulgaris (Teleostei: Sparidae) in the Canarian archipelago, northwest Africa

Diplodus vulgaris is characterized by a rudimentary hermaphroditism, with a low proportion of protandrous sex reversal. Male : female ratio is slightly unbalanced in favour of females (1 : 1.17), although no significant difference of the relation 1 : 1 was found. Both sexes have similar size distributions, with females predominating in larger sizes; a low proportion of intersexual individuals are distributed among the middle sizes. A protracted winter spawning season has been identified from November to March, with a peak in spawning activity in December–January. Size of maturity for males and females is attained in the second year of life.     

Life history traits of the striped seabream Lithognathus mormyrus (Pisces,Sparidae) from two coastal fishing grounds in the Strait of Sicily

Striped seabream Lithognathus mormyrus [n = 1269; total lengths (TLs) = 112–350 mm] were investigated in two coastal Sicilian fishing grounds (central Mediterranean Sea). Samples were collected from the two landing harbours, Licata and Selinunte, between October 1999 and September 2000. Seasonal and spatial variations in population structure, age, growth, reproduction and mortality were studied. It was found that seasonal differences in the main modes of length–frequency distributions corresponded well with the seasonal growth. The recruits in Licata grew faster and attained a larger size (by 10–20 mm) at ages up to 2 years than in Selinunte. Growth thereafter was relatively slow, with Selinunte specimens growing at a slightly faster rate. Spawning occurred between June and August. Length at the first maturity was different between females and males in the Selinunte (190–181 mm) and Licata (183–171 mm) fishing grounds. The species displayed protandrous hermaphroditism, and somatic growth practically ceased during the period of sex inversion. Total fishing mortality was considerably higher in Licata (F between 0.53 and 0.63 per year) than in Selinunte (F between 0.22 and 0.29 per year). Therefore it is suggested that the striped seabream population in Licata is more vulnerable to overfishing than that in Selinunte.     

Spatial distribution and life‐history aspects of blackspot seabream Pagellus bogaraveo (Osteichthyes: Sparidae)

Spatial distribution and life history aspects of Pagellus bogaraveo in the eastern Ionian Sea were investigated using the data from 13 different studies carried out in the area from 1983 to 2010. The spatial patterns of the abundance, biomass and mean size showed that the species inhabits the shallow waters of the shelf (<170 m depth) as juveniles up to a certain size (<180 mm total length, L_T), moving to deeper waters of the slope (mainly 400–500 m depth) as adults. The spatial pattern of abundance indicated a continuous distribution of the species in deep waters, with hot‐spot areas of high values, whereas in shallow waters distribution was more discontinuous, with higher concentrations of juveniles in estuaries and brackish waters. The study of biological aspects of the species revealed (1) a difference in the increase in mass between males and females, (2) protandrous hermaphroditism, accompanied by the presence of primary females and males that do not change sex, (3) a sex ratio in favour of females >250 mm L_T, (4) the presence of hermaphrodites between 200 and 370 mm, (5) a long reproduction period from June to March, (6) a size at first maturity around 300 mm and (7) a diet composition of adults based mainly on fishes, and also on opportunistic behaviour in the food scarce environment of deep waters. The results suggest that the species' distribution and feeding strategies are the most appropriate for the oligotrophic eastern Ionian waters and that these conditions result in smaller sizes of the species in the east Mediterranean Sea compared to the west basin and the east Atlantic Ocean, with implications for the growth and reproductive biology of the species.     

Aspects of the Life History of the Salema, Sarpa salpa (Pisces, Sparidae), off the Canarian Archipelago (Central-East Atlantic)

Life history of the salema, Sarpa salpa, off the Canarian archipelago was studied from samples collected between January 1998 and December 1999. Fish ranged from 119 to 452 mm in total length and from 24.9 to 1491.7 g in weight. The species was characterized by a protandric hermaphroditism. The overall sex ratio was unbalanced in favour of males (1 : 0.41). The reproductive season extends from September to March, with a peak in spawning activity in December–January. Males reached maturity at a smaller length (226 mm, 2 years old) than females (294 mm, 3 years old). Males, females and all fish showed an isometric growth. The morphometric relationship between length and mass for the whole population was described by the parameters: a = 0.0000134 and b = 3.01. A concentric pattern of opaque and translucent zones was readily distinguishable on the otoliths. Two rings, one opaque and one translucent, were laid down each year on the otoliths; the opaque zone was formed during the summer months, and the translucent zone during the winter months. Individuals aged 0 to 11 years were found. The parameters of the von Bertalanffy growth equation for all individuals were: L = 479 mm, k = 0.212 year^–1, and t₀ = –1.08 year.     

Age,Growth and Maturity of Red Porgy Pagrus pagrus (Sparidae) from Southeastern Brazil

Journal of Ichthyology - Age, growth and length-at-maturity of the red porgy Pagrus pagrus were studied off the southeastern coast of Brazil. A total of 798 otoliths from specimens sampled from the...     

Waterborne copper disrupts circadian rhythm in red seabream (Pagrus major)

We investigated the effect of copper (Cu) on circadian rhythms in red seabream, Pagrus major, under various concentrations of Cu (10, 20, 30 and 40 μg/L). To examine variability in circadian rhythms, we measured changes in the period 2 (Per2), cryptochrome 1 (Cry1), serotonin and arylalkylamine N-acetyltransferase (AANAT2) proteins. We found that circadian rhythm-related plasma proteins were significantly lower in a high-Cu environment (30–40 μg/L) than in low-Cu concentration (0, 10, or 20 μg/L). Our results indicate that environmental Cu at concentrations greater than 30 μg/L can have deleterious effects on fish circadian rhythms.     

Cryopreservation of yellowfin seabream (Acanthopagrus latus) spermatozoa (Teleost, Perciformes, Sparidae)

The effects of both osmolality and cation in the initiation of sperm motility were examined in yellowfin seabream, Acanthopagrus latus. Various factors involved in the cryopreservation of yellowfin seabream spermatozoa on motility are discussed. Extender containing only glucose proved to be a suitable medium for freezing yellowfin seabream spermatozoa to -196 degrees C. Glycerol seems to have a direct osmotic effect on yellowfin seabream sperm cells, and it induced sperm motility before freezing and during thawing. However, this exhausted the energy needed for sperm motility for fertilization. Dimethyl sulfoxide (DMSO) proved superior to ethylene glycerol, propylene glycerol, glycerol and methanol as a cryoprotectant. Prolonged equilibration time had a detrimental effect on both prefreezing and post-thawing sperm motility. The estimated optimum freezing rate was in the range of -20 to -154 degrees C/min. More frozen-thawed than fresh spermatozoa are required to achieve comparable fertilization rates.     

Flow cytometry and ultrastructure of cryopreserved red seabream (Pagrus major) sperm

The objectives were to assess motility, fertilizing capacity, structural integrity, and mitochondrial function in fresh versus frozen-thawed (15% DMSO was used as a cryoprotectant) sperm from red seabream (Pagrus major). Mean (+/-S.D.) rates of motility, fertilization and hatching of frozen-thawed sperm were 81.0+/-5.4, 92.8+/-1.9, and 91.8+/-5.2%, respectively; for fresh sperm, they were 87.5+/-7.7, 95.8+/-2.4, and 93.8+/-4.2%. Although motility was lower in frozen-thawed versus fresh sperm (P<0.05), there was no effect (P>0.05) of cryopreservation on fertilization or hatching. Based on scanning and transmission electron microscopy, 77.8+/-5.6% of fresh sperm had normal morphology, whereas for frozen-thawed sperm, 63.0+/-7.2% had normal morphology, 20.6+/-3.1% were slightly damaged (e.g. swelling or rupture of head, mid-piece and tail region as well as mitochondria), and 16.4+/-4.2% were severely damaged. Sperm were stained with propidium iodide and Rhodamine 123 to assess plasma membrane integrity and mitochondrial function, respectively, and examined with flow cytometry. For fresh sperm, 83.9% had an intact membrane and functional mitochondria, whereas for frozen-thawed sperm, 74.8% had an intact membrane and functional mitochondria, 12.7% had a damaged membrane, 9.9% had nonfunctional mitochondria, and 2.6% had both a damaged membrane and nonfunctional mitochondria. In conclusion, ultrastructure and flow cytometry were valuable for assessment of frozen-thawed sperm quality; cryopreservation damaged the sperm but fertilizing ability was not significantly decreased.     

Molecular characterization of the aryl hydrocarbon receptors (AHR1 and AHR2) from red seabream (Pagrus major)

The aryl hydrocarbon receptor (AHR) mediates the toxic effects of planar halogenated aromatic hydrocarbons (PHAHs). Bony fishes exposed to PHAHs exhibit a wide range of developmental defects. However, functional roles of fish AHR are not yet fully understood, compared with those of mammalian AHRs. To investigate the potential sensitivity to PHAHs toxic effects, an AHR cDNA was initially cloned and sequenced from red seabream (Pagrus major), an important fishery resource in Japan. The present study succeeded in identifying two highly divergent red seabream AHR cDNA clones, which shared only 32% identity in full-length amino acid sequence. The phylogenetic analysis revealed that one belonged to AHR1 clade (rsAHR1) and another to AHR2 clade (rsAHR2). The rsAHR1 encoded a 846-residue protein with a predicted molecular mass of 93.2 kDa, and 990 amino acids and 108.9 kDa encoded rsAHR2. In the N-terminal half, both rsAHR genes included bHLH and PAS domains, which participate in ligand binding, AHR/ARNT dimerization and DNA binding. The C-terminal half, which is responsible for transactivation, was poorly conserved between rsAHRs. Quantitative analyses of both rsAHRs mRNAs revealed that their tissue expression profiles were isoform-specific; rsAHR1 mRNA expressed primarily in brain, heart, ovary and spleen, while rsAHR2 mRNA was observed in all tissues examined, indicating distinct roles of each rsAHR. Furthermore, there appeared to be species-differences in the tissue expression profiles of AHR isoforms between red seabream and other fish. These results suggest that there are isoform- and species-specific functions in piscine AHRs.     

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.     

Ultrastructure of Pagrus major and Rhabdosargus sarba spermatozoa (Perciformes: Sparidae: Sparinae)

Transmission and scanning electron microscopy were used to investigate the ultrastructure of spermatozoa in two Sparinae species Pagrus major and Rhabdosargus sarba. Ultrastructurally, the spermatozoa of P. major and R. sarba both consist of a spherical, homogeneously electron-dense nucleus with a deep axial nuclear fossa, and an unusual notch, in the nuclear region. The midpiece contains two spherical mitochondria in R. sarba and one in P. major. The comparison of spermatozoal ultrastructure of these two species of Sparidae shows that they closely resemble one another and suggests that they are closely related. Variation in the geometry and dimensions of the mitochondrion and nucleus is substantial in these two Sparidae species. It is concluded that the spermatozoa of both species are of primitive type, and they are distinguished by several unique features which may provide useful systematic characteristics.     

Effect of cryoprotectants on hatching rate of red seabream (Pagrus major) embryos

The objectives were to investigate the effect of cryoprotectants on the hatching rate of red seabream embryos. Heart-beat embryos were immersed in: five permeable cryoprotectants, dimethyl sulfoxide (DMSO), glycerol (Gly), methanol (MeOH), 1,2-propylene glycol (PG), and ethylene glycol (EG), in concentrations of 5-30% for 10, 30, or 60min; and two non-permeable cryoprotectants: polyvinylpyrrolidone (PVP), and sucrose (in concentrations of 5-20% for 10 or 30min). The embryos were then washed and incubated in filtered seawater until hatching occurred. The hatching rate of the embryos treated with permeable cryoprotectants decreased (P<0.05) with increased concentration and duration of exposure. In addition, PG was the least toxic permeable cryoprotectant, followed by DMSO and EG, whereas Gly and MeOH were the most toxic. At a concentration of 15% and 30min exposure, the hatching rate of the embryos immersed in PG was 93.3+/-7.0% (mean+/-S.D.), however, in DMSO, EG, Gly, and MeOH, it was 82.7+/-10.4, 22.0+/-5.7, 0.0+/-0.0, and 0.0+/-0.0%, respectively. Hatching rate of embryos treated with PVP decreased (P<0.05) with the increase of concentration and exposure time, whereas for embryos treated with sucrose, there was no significant decrease in comparison with the control at the concentrations used.     

Evidence of daily spawning in natural populations of the New Zealand snapper Pagrus auratus (Sparidae)

Synopsis New Zealand snapper, Pagrus auratus, were captured by trawling from NE New Zealand over two successive spawning seasons, and examined for acute temporal changes in gonad condition. Fish with oocytes completing final oocyte maturation predominated during the morning, with a peak in ovulated fish occurring just after midday. Afternoon catches were dominated by fish in which the most advanced oocytes had yet to begin final maturation. This suggests that ovulation is synchronised to occur soon after midday, and the high proportion (up to 100% of the catch) of fish with particular gonad stages captured at any one time indicates that daily spawning involves most of the population. Diurnal changes in oocyte diameter support a daily spawning rhythm, with numbers of large hydrated oocytes peaking in the late morning, followed by the disappearance of these oocyte stages in the afternoon. Snapper captured alive by longlining were returned to the laboratory to examine the relationship between ovulation and probable time of spawning. Unovulated fish generally ovulated close to midday on the day of capture (morning captures), or the following day (afternoon captures). The viability of ovulated eggs (proportion undergoing division after fertilization) decreased markedly after oviduct residence times of over 8 hours. This suggests that natural spawning occurs before the late evening. The results of this study are consistent with anecdotal evidence suggesting that spawning occurs every day during the late afternoon or early evening, and is similar to the reproductive patterns displayed by a number of closely related sparids. Department of Zoology, University of Otago, PO Box 56, Dunedin, New Zealand     

Interannual variation in the reproductive cycle of the New Zealand snapper Pagrus auratus (Bloch & Schneider) (Sparidae)

Changes in reproductive condition in the New Zealand snapper Pagrus auratus (Bloch & Schneider) were monitored in a wild population over three successive years. Recrudescence occurred in spring with spawning beginning in October and continuing for 3 to 5 months. The initiation of spawning varied by up to 3 weeks and was associated with sea surface temperatures of 15–16° C. Theconclusion of spawning was associated with temperatures of 19–21° C but showed greater interannual variation than the onset of spawning. Changes in the gonadosomatic index were accompanied by parallel changes in hepatosomatic index in females but not males, reflecting the role of the liver in vitellogenesis in females.