Age,growth, reproduction and feed of longnosed skate,Dipturus oxyrinchus (Linnaeus, 1758) in Saros Bay,the north Aegean Sea

The age, growth, reproduction, and feeding of longnosed skate (Dipturus oxyrinchus) were studied using 179 specimens from the Saros Bay (North Aegean Sea) between March 2005 and December 2007. Composition was 49.7% females and 50.3% males. Total length of females ranged from 14.9 to 100 cm (disc width, 9.8–65 cm), and of males from 15.2 to 86.5 cm (disc width, 10–57.5 cm). Total length‐weight and disc width‐weight relationships are described by the equations W = 0.0008*TL^3.35 and W = 0.0043*DW^3.29, respectively. The age data, derived from vertebrae readings, were used to estimate the growth parameters of the von Bertalanffy equation: L_∞ = 256.46 cm, K = 0.04 year^?1, t₀ = ?1.17year. The maximum age was 9 years. Males matured at 64–65 cm (disc width, 43.5 cm) and females at 82–83 cm TL (disc width, 53 cm). The stomach contained mainly Parapenaus longirostris, IRI: 93.47%.     

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.     

Age and growth of the Black Sea turbot, Psetta maxima (Linneaus, 1758) (Pisces: Scophthalmidae), estimated by reading otoliths and by back-calculation

Age and growth of the Black Sea turbot, Psetta maxima, were determined from a total of 1445 individuals collected along the eastern Black Sea coast between 1990 and 1996. Age was estimated by interpreting growth rings in whole and broken sagittal otoliths. The former method underestimated the age over 5 years, and a maximum age of 11 years was observed by the latter. Marginal increment analysis clearly showed that a single annulus is formed in early summer each year. Growth in length differed between sexes, and females attained a larger size than males at the same age. No significant difference was found between the mean observed total length (TL), the back‐calculated TL derived from radius measurements and the TL estimated from otolith size–fish size relationship. The von Bertalanffy growth parameters estimated by the length‐at‐age data were: L_∞ = 96.24 cm; K = 0.119 year^?1; t₀ = ?0.01 year for the entire population.     

Age, growth and mortality of painted comber, Serranus scriba (Linnaeus, 1758), in the Trogir Bay area (eastern mid-Adriatic)

Population dynamics of 1482 specimens of painted comber, Serranus scriba (Linnaeus, 1758), caught in the Trogir Bay area (eastern mid‐Adriatic) from June 2001 to May 2002 were studied to provide information on age, growth, length–weight relationship, mortality and exploitation rate of the species’ stock. Annuli on otholiths indicated the presence of seven age‐classes. Obtained von Bertalanffy growth parameters were: L_∞ = 30.36 cm, K = 0.192 year^?1 and t₀ = ?0.366.     

Age,growth and mortality of scaldfish (Arnoglossus laterna Walbaum, 1792) from the Adriatic Sea

The population dynamics parameters of scaldfish, Arnoglossus laterna, from the Adriatic Sea were studied. Specimens ranging from 4.5 to 17.1 cm in total length were collected from commercial bottom‐trawl catches (2000–2006). Spawning from April through the end of August with a peak in May, A. laterna is one of the non‐target species usually present in mixed bottom trawl catches. The overall male to female ratio was 1.00 : 0.61. The oldest individual was 6 years of age. Length–weight relationships showed positive allometric growth (b = 3.36 for males and b = 3.39 for females). Parameters of the von Bertalanffy growth equation were: L_∞ = 17.3 cm; K = 0.258 per year; t₀ = ?1.0026 year; R² = 0.925. The relatively low value of total mortality (Z = 0.90) and relatively high value of constant rate of natural mortality (M = 0.64) was estimated. Presumed calculated fishing mortality (F = 0.26) and the consequently estimated exploitation ratio (E = 0.29) indicated no danger of an over‐exploitation of this species in the study area at the current level of fishing pressure. The low T max and correspondingly high M suggest that this small benthic predator plays an important role in the Adriatic ecosystem as a prey species for large benthic predators. However, the estimates include uncertainties and require further confirmation, especially with regard to natural mortality.     

Life‐history characteristics of the endangered Aristotle’s catfish (Silurus aristotelis Garman, 1890), Lake Pamvotis,north‐western Greece

The life history characteristics of Aristotle’s catfish, Silurus aristotelis (Agassiz 1856) were studied in Lake Pamvotis (northwestern Greece). Samples were collected on a monthly basis using gillnets, trammel‐nets and traps. Total lengths ranged from 11.1 to 36.7 cm. Sex ratio was biased toward females (F : M = 1.8 : 1) and was statistically different from unity (χ² = 46.94, P < 0.001). Spawning is from April to June. The relationship between total length and total weight showed positive allometric growth for males (TW = 0.0035 × TL^3.21, r² = 0.93, n = 198, P < 0.001) and females (TW = 0.0066 × TL^3.02, r² = 0.95, n = 363, P < 0.001). Age was determined on the annual growth marks formed on the spine of the pectoral fin. Based on cross‐section readings of the spine, lifespan of the Aristotle’s catfish was 5 years. Age classes 1 and 2 dominated the catches (39.1 and 40.0% of the total sample, respectively). Back‐calculated lengths at age showed a rapid increase in fish size during the first year of life, reaching 61.1% of maximum attainable length, and a declining growth rate thereafter. Growth parameters were calculated as L_∞ = 36.12 cm, K = 0.37 year^?1, t₀ = ?0.76 year based on the observed lengths at age and as L_∞ = 28.19 cm, K = 0.53 year^?1, t₀ = ?0.62 year based on the back‐calculated lengths at age. It seems that some of the life history traits (longevity, growth pattern, reproductive period) are influenced significantly by adverse effects of pollution and eutrophication on the lacustrine ecosystem.     

Age estimation and specific growth pattern of boxlip mullet,Oedalechilus labeo (Cuvier, 1829) (Osteichthyes,Mugilidae), in the eastern Adriatic Sea

The main objective of this study was to investigate boxlip mullet, Oedalechilus labeo (Cuvier, 1829), a species that lives in open, oligotrophic and stenohaline waters, exhibits slower growth rates and has a longer life span than other mugilids. A total of 1662 specimens ranging from 2.2 to 24.4 cm TL were obtained by beach seine in the eastern Adriatic Sea. The overall sex ratio was unbalanced in favour of females (1.0 : 1.3) and differed statistically from the expected 1 : 1. The reproductive season extended through summer and autumn. All specimens above 15 cm TL were sexually mature. Length‐weight relationship for males was TW (g) = 0.010 × TL (cm)^2.975 and TW (g) = 0.009 × TL (cm)^3.014 for females. The age study comprised 150 (38.5%) males, 192 (49.4%) females, and 47 (12.1%) immature O. labeo, for a total of 389 individuals. Age of the fish was determined by scale readings, with the maximum age of 10⁺ observed for both sexes. A predominance of age classes 1⁺ and 2⁺ (71.0%) in the total catch was noted. Parameters of the von Bertalanffy growth equation for combined samples were: L_∞ = 25.93 cm, k = 0.192 year^?1 and t₀ = ?1.427 year. The growth parameters showed that males grew at a slightly lower rate than females. The size and age frequency distributions of both sexes were not significantly different. When compared to other mugilids, O. labeo reaches the lowest maximum body length and has a relatively slower growth and a longer life span.     

Growth and length–weight relationship of the juvenile anchovy, Engraulis encrasicolus, in the nursery ground (Zrmanja River estuary–eastern Adriatic Sea)

Growth and length–weight relationships of 2564 juvenile specimens of anchovy, Engraulis encrasicolus (Linnaeus, 1758), were examined over a 2‐year period (August 1989 to April 1991) in the Zrmanja River estuary. Fish sizes ranged from 4.4 to 12.5 cm total length and 0.5 and 13.8 g, corresponding to age (in years) 0+ (98%) and 1+ (2%). Length–weight regression coefficient (b) varied between 2.95 and 3.42 and the regression constant (a) between 2.1 and 6.0 (×10^?3). The von Bertalanffy growth equation of juvenile anchovy was: l_t = 13.2 (1 ? e^?0.82(t+0.5)). Maturity was reached in June in males above 8.2 cm and females above 9.0 cm total length.     

Age and growth of the spotted goatfish, Pseudupeneus maculatus (Bloch, 1793) in Brazil, validated through marginal increment and oxytetracycline dyes in the sagittae

A sample composed of 4973 specimens of the spotted goatfish, Pseudupeneus maculatus (4.5–29.2 cm fork length) was collected off northeastern Brazil from 1999 to 2002. Sagittae (398) were analyzed for age and growth estimation using both annuli and microincrements. For the first approach, the mean monthly marginal increment ratio analysis suggested that one band is formed annually from May to June. With the microincrements analysis, 15 specimens were reared (3–71 days) for validation of periodicity using oxytetracycline. Fluorescent dyes were observed in 10 specimens (7.5–16.9 cm). After testing, one microincrement was found to form daily. Otolith sections were polished and analyzed using a light microscope (100–1200× magnifications). Individuals larger than 22.6 cm (4 years) showed heavily overlaid increments on the otolith edge, which hampered the counts. There was agreement on the size from counts on an annual and daily basis. The von Bertalanffy function provided the following parameters: L_∞ = 33.23 cm; K = 0.265; t₀ = 0.0883 year. The sample was composed of 0⁺ to >5‐year‐old specimens. Age at first maturity was 3.6 years (20 cm), whereas the recruitment age for fisheries was 3.9 years. Juveniles represented about half of the catch (48.7%), which may have implications for population equilibrium.     

Age, growth and reproductive characteristics of chub, Leuciscus cephalus (L., 1758) in the İkizcetepeler dam lake (Balikesir), Turkey

In this study, the population structure, growth and reproduction characteristics of 414 chub (Leuciscus cephalus L., 1758) from the ?kizcetepeler dam lake were investigated monthly between January and December 2000. Age groups ranged between I and VI for this species in the reservoir, with the second and third year‐classes dominating. Sex ratio was 1 : 1.4 (M : F), corresponding to 58.4% males and 41.6% females. Females attained greater size and age than males. The largest female captured was 24.8 cm FL, the largest male was 24.1 cm FL, both age VI. The von Bertalanffy growth equations and length–weight relationships were found as: L_t = 28.89[1 ?e^{?0.224(t+1.55)}] for females, L_t = 26.71[1 ? e^{?0.259(t+1.55)}] for males; W_t = 347.386[1?e^{?0.224h (t+1.55)}]^2.86 for females, W_t =286.48[1?e^{?0.259 (t+1.55)}]^2.92 for males; W = 0.0227 × L^2.87 for females and W = 0.0194 × L^2.92 for males. Significant statistical differences in condition factors between age classes and sexes were not found (P > 0.05, t‐test). Spawning period of this species in the lake was between April and May.     

Growth of pike Esox lucius L. in Lake Rubikiai (Lithuania)

The aim of the study was to determine the growth rate and growth parameters of pike Esox lucius L. in the mesotrophic Lake Rubikiai and to evaluate species growth in light of environmental conditions in Lithuanian lakes of different limnologic types. A total of 204 pike specimens were caught in two subsequent years, April 2005 and April 2006, in Lake Rubikiai. Six age classes (2–7 years of age) for males and 10 age classes (3–12 years of age) for females were identified by scale readings; 2‐ to 4‐year‐old males and 4‐ to 7‐year‐old females prevailed. Total length of pike ranged from 26.5 to 107 cm and weight from 106 to 7600 g. There were no statistically significant differences (Student’s t‐test, P > 0.1) between mean lengths and weights of males and females of the same age. Von Bertalanffy growth parameters for the entire population were: L_∞ = 131.7 cm, k = 0.1530 year^?1, t_o = ?0.0398 year. Calculated overall growth performance index ?′ was 3.42. The length‐weight relationship was described by the equation . The growth rate of pike in Lake Rubikiai was higher than in most other investigated Lithuanian lakes. Pike from Lake Rubikiai are characterized by average growth, compared to other populations from various geographical locations. No significant differences were established between the growth of pike in mesotrophic and eutrophic lakes. Pike growth rate did not correlate with lake surface area, maximum or mean depth, and negatively correlated with bogginess in mesotrophic lakes and limpidity and bogginess in eutrophic lakes (P < 0.05).     

Growth and length–weight relationships of Sander lucioperca (Linnaeus, 1758) in the Alcántara Reservoir,south‐western Spain: comparison with other water bodies in Eurasia

Growth parameters in pikeperch may be affected by several factors. The purpose of this study was to investigate the growth and length–weight of pikeperch in a reservoir in south‐western Spain and compare the results with previous published data. Age and growth are described for Sander lucioperca from the Alcántara Reservoir (south‐western Spain) from March to October 2009. A total of 285 fish were examined; the ratio of males to females was estimated as 0.78:1 and age ranges as 1–5 years. Total lengths ranged from 16.1 to 52.5 cm. The length–weight relationships were described as W = 0.00 462 TL^3.09 (r = 0.9865) for males and W = 0.00279 TL^3.16 (r = 0.9921) for females. Growth was expressed in length and the von Bertalanffy growth parameters were estimated as L∞ = 92.14 cm, k = 0.09, t₀ = ?1.05 for males and L∞ = 107.72 cm, k = 0.08, t₀ = ?1.16 for females. Growth performance indexes were also estimated as Φ’ = 2.88 for males and Φ’ = 2.96 for females. Differences in growth and length–weight relationships between sexes were not found.     

Age,growth and sexual development of solenette,Buglossidium luteum (Risso, 1810), in the central Aegean Sea

Age, growth, spawning period and maturity of the solenette (Buglossidium luteum Risso, 1810) were studied in the central Aegean Sea to provide fisheries managers with essential data for science‐based management. A total of 1220 samples were collected by trawl hauls from July 2004 to June 2007 in ?zmir Bay (Turkey). Sample sizes ranging from 5.3 to 11.6 cm total length were composed of 46% females, 32% males and 22% immature individuals, with a female to male ratio of 1 : 0.7. Age composition stages of the females were from I to IV, and males between I and III. The length–weight relationship was calculated as W = 0.0101L^3.008 for all samples. Estimated von Bertalanffy growth parameters were L = 13.30 cm, t_o = ?0.440 year and k = 0.481 year^?1, with a growth performance index of 1.93 (?’). The spawning period began in April and continued until July. Lengths at first maturity of females and males were 8.1 and 7.9 cm total length, respectively. Both sexes matured at the age of 2 years.     

Age,growth and reproduction of the white seabream Diplodus sargus sargus (Linneaus, 1758) off the eastern coast of Algeria

The objective of this study was to determine the basic population‐specific parameters necessary for fish stock assessment in the area and to compare these with data from other Mediterranean regions. White seabream Diplodus sargus sargus (n = 449) were caught along the Algerian coast between December 2005 and December 2006. Total length ranged from 12.2 to 34.6 cm, representing age classes between 0 and 10 years. Validity of the otolith readings for estimating age and growth was supported using the back‐calculation method. The von Bertalanffy growth parameters for all fish were calculated as: TL = 36.3 cm, k = 0.154 year⁻¹, t₀ = −0.488 year. The growth performance index (φ) showed a relatively slow growth of the local population. The length‐weight relationship showed an isometric growth (b = 2.98; r = 0.98). Subspecies Diplodus sargus sargus was characterized as being a proterandric hermaphrodite. Overall ratio of males to females was 1 : 1.4, with males predominant in the smaller size intervals and females in the larger ones. The reproductive season extended from January to May, with a March–April peak in spawning activity. Fifty per cent maturity of the tested cohort was reached at a total length of 20.2 cm for males and 20.0 cm for females.     

Age and growth of the Randall’s threadfin bream Nemipterus randalli (Russell, 1986), a recent Lessepsian migrant in Iskenderun Bay,northeastern Mediterranean

Randall’s threadfin bream, Nemipterus randalli, first recorded in Iskenderun Bay in Turkey in 2008, seems to have increased in the region. The species, widespread in the western Indian Ocean and with a rapid expansion, appears to have migrated to the bay via the Red Sea. Although its presence in the region has been published, there has been little or no information as to age and growth parameters of this Lessepsian migrant in its new habitat. The present study aims to determine the basic age and growth parameters of the species colonized in the region. A total of 379 collected individuals were studied from November 2007 to October 2008. Total specimen lengths ranged from 4.80 to 21.50 cm, and weights from 1.10 to 138.36 g. Maximum age was 3 years for both sexes. The length–weight relationship was described as W = 0.0011 × L^3.061 (r² = 0.982). The von Bertalanffy growth parameters were: L_∞ = 34.96 cm; K = 0.214 year^?1; t₀ = ?1.244 year for the entire population. These data were compared with results from studies made in other geographic areas.     

Age,growth and feeding habits of the bluemouth rockfish,Helicolenus dactylopterus dactylopterus (Delaroche 1809) in the central Mediterranean (southern Tyrrhenian Sea)

This paper provides data on age, growth and diet of the bluemouth rockfish, Helicolenus dactylopterus dactylopterus (Scorpaenidae), central Mediterranean Sea. Estimated by otolith readings, ages ranged from 0 to 21 years. Parameters of the von Bertalanffy growth curves were L_inf = 26.1 cm, k = 0.14 year^?1, t₀ = ?1.92 years and the growth performance index was Φ = 1.98. The weight‐length relationship, W = 0.016 TL^2.99; R² = 0.99, described an isometric growth of the species. This species is a carnivore focusing mainly on the crustaceans Goneplax rhomboides and Lophogaster typicus. Statistical analysis showed an ontogenetic shift between small (4.0–6.3 cm) and larger fishes. Significant differences were also found in relation to the sampling depth.     

Validating annulus formation and examining the potential use of pectoral spines for age determination in Aristotle’s catfish (Silurus aristotelis)

The potential use of pectoral fin spines for ageing purposes was examined in Aristotle’s catfish (Silurus aristotelis) and validated for growth proportionality and growth mark periodicity. Monthly samples (n = 436, total length range: 11.10–36.70 cm) were collected in Lake Pamvotis, Greece from November 2002 to December 2003. Marginal increment analysis showed that the spine width (SW) radius grew proportionally to total body length (TL) (TL = 9.581 + 6.83SW, r² = 0.66, n = 431, P < 0.01), and was at a minimum in January and February, indicating a single growth mark formation per year (i.e. annulus). Further analyses showed that the morphometric characteristics of the spines did not differ significantly (r² > 0.80 in all cases) when removed from one side of the fish or the other. The procedure was based on individuals no older than 5 years of age; extrapolation to higher age classes may be critical.     

Growth characteristics of Uranoscopus scaber Linnaeus 1758, inhabiting the Iskenderun Bay (Northeastern Mediterranean)

This study aimed to determine the age and some growth characteristics of Atlantic stargazer (Uranoscopus scaber) from Iskenderun Bay (Northeastern Mediterranean). For this purpose, a total of 150 Atlantic stargazer ranging in size from 9.1 to 28.0 cm in total length (weight: 11.7–345.7 g) were collected as by-catch from a commercial trawl fishing boat at a depth of 80–100 m between May 2015 and January 2016. The bottom trawl gear used was equipped with a 44 mm stretched mesh size net at the cod-end. The percentage of females and males were 46.7% and 53.3% respectively. The total length–weight relationships equation with coefficient of determination (R²) were found as W = 0.011*TL^3.131, R² = .9728, for all individuals, W = 0.015*TL^3.021, R² = .9512 for females and W = 0.0102*TL^3.136, R² = .9553 for males. By using the von Bertalanffy equation, the growth parameters of Atlantic stargazer were estimated to be L_∞ = 42.35 cm, k = 0.098, t₀ = −1.8474 for all individuals; L_∞ = 36.92 cm, k = 0.138, t₀ = −1.2693 for females and L_∞ = 38.77 cm, k = 0.1, t₀ = −2.334 for males. In this study, age reading was done by two independent readers and index of average percentage error (IAPE) was calculated as 6.1%. The highest condition factor value calculated as 1.81 in the age group 6 and the lowest condition factor value was calculated as 1.48 in the age group 1.     

Reproduction,growth and feeding habits of stout beardfish Polymixia nobilis (Polymixiidae) off the Canary Islands (NE Atlantic)

The present study provides fisheries biology knowledge which will allow the implementation of regulatory measures contributing to the sustainability of the fisheries and the conservation of the stout beardfish Polymixia nobilis Lowe, 1838 off the Canary Islands, north eastern Atlantic Ocean. Males ranged between 16.5 and 38.4 cm fork length (FL) and females from 14.2 to 46.5 cm FL. Sex ratio by size classes provided significant differences in classes higher than 36 cm, being clearly unbalanced in favour of females. Individuals in maturing and mature stages were present during all months sampled, although a spawning peak is evident between April and June. Size at first maturity was estimated as 26 cm FL for females and 30 cm FL for males. Age was determined from annuli in whole otoliths. Age range was found to be 0–14 years for fish measuring 14.2 to 46.5 cm FL. It is a slow‐growing and long‐lived species. Significant differences in the growth parameters between sexes were detected. The von Bertalanffy growth parameters estimated for females (n = 213) were L_∞ = 45.92 cm LF, k = 0.16 years^?1 and t₀ = ?2.84 years; and for males (n = 186) L_∞ = 36.44 cm LF, k = 0.26 years^?1 and t₀ = ?2.16 years. Stomach analysis indicated some variations in the feeding habits with growth: individuals of small and medium sizes preyed on crustaceans and fishes, while large specimens preyed mainly on fishes.