Maturity and growth of Paralonchurus brasiliensis females in southern Brazil (Teleostei, Perciformes, Sciaenidae)

Samples of Paralonchurus brasiliensis Steindachner, 1875 (627 females; no males) were taken monthly from June 1997 to May 1998 at the fishing pier of Cidreira – Rio Grande do Sul (30°08′S; 50°11′W) in southern Brazil. The fish were captured by sport fishermen using different sizes of hook‐and‐line. The reproductive period of P. brasiliensis extends from August to March, presenting greater activity from October to February. Females reach first maturation at 15.4 cm total length (TL). Of the 466 scales analyzed, one to six annuli were found. Growth annuli are formed between June and August, corresponding to the winter period (southern hemisphere), with the first visible annulus being formed when the fish are 1.5 years old. The length growth curve for P. brasiliensis females is described as: L_t = 20.0 (1 ? e^?0.564×t), TL in centimeters and age in years. The undersize asymptotic length may be a result of excessive fishing mortality on the studied population.     

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.     

Reproduction, growth, mortality and yield of Tilapia mariae Boulenger 1899 (Cichlidae) in a Nigerian rainforest wetland stream

The biology and fisheries of Tilapia mariae, the only tilapiine cichlid fish in the Iba Oku (Uyo, Nigeria) wetland stream was studied. There were more females than males in the population. The smallest sexually mature female fish was 11.0 cm total length (TL) while the size at 50% maturity was 17.1 cm TL. Absolute fecundity (F_e) ranged from 953 to 3200 eggs and was positively correlated with TL. The fish bred year‐round with peaks in November, March–April and July–September. The seasonalized von Bertalanffy growth function (VBGF) was fitted to the 12 consecutive months length–frequency data (n = 2439) to obtain a VBGF with the following parameters: L∞ (asymptotic length) = 30.4 cm TL, K (growth coefficient) = 0.4 year^?1, C (amplitude of growth oscillation) =0.4, and WP (winter point) = 0.9. The seasonalized length‐converted catch curve method gave Z (instantaneous total mortality coefficient) as 1.75 year^?1, M (instantaneous natural mortality coefficient) was 0.99 year^?1 while F (instantaneous fishing mortality coefficient) was 0.76 year^?1 and E (=F/Z the current exploitation rate) was 0.43. Length at first capture (Lc) was 17.7 cm TL. The fish was recruited to the fishery year‐round with two pulses. From the Beverton and Holt relative yield per recruit analysis via the selection ogive procedure, E_max (predicted maximum exploitation rate) was 0.54. The stock was not overexploited, since E < E_max. This study also showed that the fish is an r‐selected species with a few K‐selected traits.     

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.     

Population structure and reproductive biology of a freshwater fish,Labeo boggut (Sykes, 1839), from two perennial rivers of Yamuna basin

Population structure and reproductive biology of an important and less studied freshwater carp, Labeo boggut (Sykes, 1839), from two perennial rivers of Central India were studied between January 2008 and December 2009. Maximum three annual rings were found and used to assess growth data in samples representing 0 to 3+ year classes. LWR indicated positive allometric growth in males and females of both rivers. Asymptotic length (L_∞) and growth co‐efficient (K) were 22.5 cm and 0.5 year^?1 for the Betwa River; and 23.6 cm and 0.6 year^?1 for the Ken River. Growth performance index (ø’) was higher in the Ken than in the Betwa. Reproduction was between June and September and GSI of both sexes were maximal in mid‐June, thereafter declining until September. Mean size at first sexual maturity was 12.2 cm (n = 12) for females and 13.2 cm (n = 8) for males in the Betwa, and 12.5 cm (n = 13) TL for females and 13.1 cm (n = 9) TL for males in the Ken. The exploitation level (E) and maximum allowable exploitation (E_max) limit of L. boggut was 0.23 and 0.36 in the Betwa, whereas it was 0.33 and 0.37 in the Ken. These presented biological traits and population characters of L. boggut from both rivers provide first basic information for use in future assessment and conservation planning.     

Age and growth of a sub-Antarctic notothenioid, Patagonotothen ramsayi (Regan 1913), from the Falkland Islands

The Falklands’ rockcod Patagonotothen ramsayi was aged successfully using whole and sectioned otoliths. Marginal increment analysis showed that one opaque and one translucent zone were laid down each year. Counting daily rings in juvenile fish and back calculating to their assumed hatch dates validated the first annulus. Readings taken from scales and otoliths showed good agreement with no significant difference between them (P>0.05). Inter- and intra-reader comparisons also showed good agreement. The maximum estimated age was found to be 14 years and the calculated von Bertalanffy growth curve L _T =33.77(1−e ^{−0.25year(t+1.07)}) showed that P. ramsayi is a relatively slow growing fish that attains 5–6 cm L _T in its first year and after which grows approximately 3 cm per year until 4 years. Males seemed to have a slightly lower growth rate but attained a greater maximum size than females. The formation of annuli in the otoliths of P. ramsayi seems to coincide with periods of high reproductive activity with both peaks in GSI and the prevalence of translucent margins occurring in July.     

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.     

Age, growth, mortality and sex ratio of sand smelt, Atherina boyeri Risso, 1810 (Pisces: Atherinidae) in the estuary of the Mala Neretva River (middle-eastern Adriatic, Croatia)

The present study investigated the age, growth, mortality and morphometry of the sand smelt, Atherina boyeri, in the Mala Neretva River estuary (mid‐eastern Adriatic Sea). The study of scale annuli showed that the population is up to 4 years of age. However, most sand smelt are in their first and second year; the numbers of older individuals are very low because they migrate upstream and are heavily fished. The von Bertalanffy parameters for the total sample of sand smelt were found to be L_∞ = 13.5 cm, K = 0.37 year^?1 and t₀ = ?0.97. Overall total mortality was estimated at 1.81 year^?1, natural mortality was 0.90 year^?1 and fishing mortality was 0.91 year^?1.     

The growth ofOreochromis andersonii (Pisces: Cichlidae) from the Okavango Delta,Botswana, and a comparison of the scale and otolith methods of ageing

Synopsis Otoliths and scales were used for age and growth determination ofOreochromis andersonii from the Okavango Delta, Botswana. Marginal increment analysis showed that an annulus was formed in both the scales and otoliths during the dry summer period. Using scales, the growth ofO. andersonii was described by L_t = 285.27(1-e^{-0.26(t+2.02)}) mm SL and using otoliths by the equation L_t = 267.48(1-e^{-0.25(t+2.18)}) mm SL. Maximum age estimates of 10 years using scales and 13 years using otoliths were obtained and the growth curves were significantly different (p < 0.01). Age estimation using scales tended to over-emphasise growth inO. andersonii resulting in larger predicted lengths-at-age. For this reason, otoliths are considered to be more reliable and suitable than scales in determining the age and growth of this species.     

Age and growth of Atlantic bluefin tuna, Thunnus thynnus (Osteichthyes: Thunnidae), in the Mediterranean Sea

The objective of the study was to describe the biometry of Mediterranean bluefin tuna, Thunnus thynnus, the biology of which is not yet well understood. A total of 504 specimens was collected from 1998 to 2005 in the central part of the Mediterranean basin. They were sexed and measured; fork lengths (FL) ranged from 51.0 to 255.0 cm while body weights (W) ranged from 2.6 to 247.0 kg. The first spiniform ray (spine) of the first dorsal fin was removed and cross‐sectioned near the condyle base in order to count annuli for age estimation. The regression coefficient (b) of the female FL–W relationship was significantly higher than that of the male, and both sexes displayed a negatively allometric growth (b < 3); male regression equation: ln W = ?2.942 + 2.730 ln FL; female regression equation: ln W = ?3.660 + 2.878 ln FL. Based on counts of the translucent zones in the sections of the first ray of the first dorsal fin, estimated ages ranged from 1 to 15 years for males and 1 to 14 years for females. The correlation between the spine ray (R) and FL fit the allometric model best; the R–FL regression equations of the two sexes did not differ significantly and the overall equation was: ln FL = 3.721 + 0.851 ln R. Due to the R–FL allometric correlation, estimates of fork lengths at previous ages, FL_i, were back‐calculated with a body proportional hypothesis. Von Bertalanffy growth equations were derived from both observed and back‐calculated FLs‐at‐age, which did not differ significantly. Moreover, no significant difference was found between the growth equations of the two sexes; the overall equation was FL_t = 373.08 [1?e^{?0.07(t + 1.76)}]. Weight‐at‐age values were derived from the von Bertalanffy predicted FLs‐at‐age by the FL–W correlation equations for males and females. The paper represents the first comprehensive study on the biometry, including age and growth, of bluefin tuna captured in the Mediterranean Sea.     

The potential use of scales for estimating age and growth of Mediterranean albacore (Thunnus alalunga)

The ability to accurately estimate the age of fishes is critical for conducting stock assessments and developing fishery management policies. Scales were collected from albacore, Thunnus alalunga, caught in the Mediterranean Sea during the years 1989–1995 to estimate their age and growth. Ages, which ranged from 1+ to 6+ years, were estimated from the interpretation of the concentric rings on the scales of 473 individuals that ranged in fork length from 55.5 to 89 cm. Males reached a greater size and age than females. The relatively close agreement in the mean lengths at ages estimated by scales and other techniques constituted a preliminary verification of the method. The von Bertalanffy growth model was fitted to mean lengths at estimated ages, resulting in the following growth parameters for the combined sexes: L_∞ = 86 cm, K = 0.4, t_o = ?0.8 years. Parameter estimates were in agreement with what is known about life history of the species in the Mediterranean. Moreover, the growth rates were consistent with length increment observations from five tag returns, which lend support to our working hypothesis that the scale‐rings are annual structures. When the Mediterranean albacore growth parameters were compared with those of Atlantic Ocean albacore using scale age estimates, there were significant differences between the two populations, and Mediterranean albacore remain significantly smaller than Atlantic Ocean albacore.     

Growth pattern of the endemic Neretvan roach,Rutilus basak (Heckel, 1843) in the Hutovo Blato wetlands

The growth pattern of the endemic Neretvan roach, Rutilus basak from the Hutovo Blato wetlands was analyzed. A total of 441 specimens ranging from 6.0 to 21.7 cm TL were obtained by electro fishing between December 2007 and November 2008. The male:female ratio for all fish combined was 0.34 : 1.00 but changed across length classes. The spawning period extended from February to April, with a peak in the first half of March. Maximum observed age was 10 years. Predominance of age classes 1–5 in the catch (77.0% of individuals) was noted. The length–weight relationship showed a positive allometric growth (b = 3.321; R² = 0.957). Parameters of the von Bertalanffy equation were: L_∞ = 20.201 cm; K = 0.257 per year; t₀ = ?1.554 year; R² = 0.977. This study revealed that R. basak invests energy in reproduction rather than in body size and thus has a relatively fast growth, short life span and precocious maturity. Moreover, elementary biological population parameters are provided that can be used for conservation purposes.     

Using scales to clarify the transition from blue-phase to brown-phase fingerling in Notothenia rossii from the South Shetland Islands

Scales and whole otoliths were read for age determination in early stages of Notothenia rossii caught in Potter Cove, South Shetland Islands, in summer seasons 2003–2006 and 2008. The sample comprised blue-phase pelagic fingerlings of 7.0–7.6 cm (TL) of age group 0 year and demersal brown-phase fingerlings/juveniles of 8.5–20.9 cm and predominant age groups 1–2 years. Counting of sclerites facilitated the interpretation of the rings, particularly in the central scale. To clarify two previous issues of controversy, we deduce that the duration of the offshore pelagic blue-phase fingerling stage is less than one year before migration to the nearshore demersal habitat. Furthermore, the first well-defined ring in scales corresponded to the first annulus, while a contiguous ring was a secondary ring sometimes deposited after the first winter during the second year of life, attributable to a shift of habitat from pelagic to demersal. A von Bertalanffy growth curve was computed by combining age/length data of the juvenile phase of N. rossii from this and a previous study at Potter Cove with literature data from the offshore adult population, resulting in the following equation: L_t = 8 6. 9  ( 1- \texte ^{- 0. 0 9 1 (t - 0. 6 6 8 )} ) L_{t} = 8 6. 9 \,\left( { 1- {\text{e}}^{{ - 0. 0 9 1 (t - 0. 6 6 8 )}} } \right) _.     

Age and growth estimates of the bull shark,Carcharhinus leucas,from the northern Gulf of Mexico

Synopsis Length at age and growth rates for 59 bull sharks, Carcharhinus leucas, collected from the northern Gulf of Mexico were estimated from the band patterns formed seasonally in the vertebral centra. The combined age at length data for both sexes were applied to a von Bertalanffy growth model producing parameter estimates of L = 285 cm TL, K = .076, t₀ = –3.0 yr. Lengths at age for males and females were similar except that males did not attain as great a length as females. Growth was apparently slow and varied among individuals, but in general, was estimated to be 15–20 cm yr^–1 for the first five years, 10 cm yr^–1 for years 6–10, 5–7 cm yr^–1 for years 11–16, and less than 4–5 cm yr^–1 thereafter. Males mature at 210–220 cm TL or 14–15 yr of age; females mature at>225 cm TL or 18+ yr of age. The largest male (245 cm TL) was 21.3 yr old; the largest female (268 cm TL) was 24.2 yr old.     

Population biology and assessment of the white-spotted spinefoot, Siganus canaliculatus (Park, 1797), in the southern Arabian Gulf

The age, growth, mortality, reproduction and resource status of Siganus canaliculatus in the southern Arabian Gulf were investigated using a combination of size frequency, biological and size‐at‐age data. Defined structural increments consisting of alternating translucent and opaque bands in transverse sections of sagittal otoliths were validated as annuli. The maximum absolute age estimate was 7.8 years. Parameter values of the von Bertalanffy growth function fit to size‐at‐age data (males and females combined) were: k = 1.0, L_∞ = 24.8 cm (L_F), t_o = −0.1 years. Fish in spawning condition were only observed between April and July although patterns in gonadosomatic indices suggested a second but less well defined spawning event in November. The mean sizes and ages at first sexual maturity were 21.5 cm L_F (1.9 years) for males and 25.7 cm L_F (2.1 years) for females. Fish were fully recruited to the fishery at a size (L₁₀₀ = 19.7 cm L_F) that was smaller than the sizes at which sexual maturity was attained. The annual instantaneous rate of fishing mortality (F = 0.85 year⁻¹) (0.26–1.44 year⁻¹ 95% CI) was considerably greater than the target (F_opt = 0.33 year⁻¹) and limit (F_limit = 0.44 year⁻¹) biological reference points, indicating that the stock is overexploited.     

Age,growth and maturity of tub gurnard (Chelidonichthys lucerna Linnaeus 1758; Triglidae) in the inshore coastal waters of Northwest Wales,UK

The tub gurnard Chelidonichthys lucerna has been identified by ICES as a potential commercial species in the northeast Atlantic with recommendations made to monitor landings and discards and to derive information on population biology for stock assessment purposes, however, data are lacking for the species in the northeast Atlantic. Therefore, aims of this study were to provide data on the size/age‐structure and patterns of growth, maturity and mortality of C. lucerna in Northwest Wales, UK, and in doing so to provide data on the biological characteristics of the most northerly population studied to date for comparison with the existing data for southerly Mediterranean populations. Data on the age, growth and maturity of C. lucerna were collected by otter trawling (73 mm cod‐end stretched mesh size) in the coastal waters of Northwest Wales, UK in October (2000–2011, excluding 2006). Total length (TL) of fish sampled ranged between 10.5–41.0 cm (males) and 10.4–57.5 cm (females). The majority of the female fish were between 20–30 cm TL (60.2%) and the majority of the male fish between 20–30 cm TL (58.3%) respectively. TL/weight (W) relations for male and female fish were similar and the combined data was described by W = 0.0067 TL^3.10. Age of fish ranged between 1–7 years old for female fish and 1–5 years old for male fish respectively with the majority of female fish 3 years old (40%) and the majority of male fish 3 years old (37%). The age structures of female and male tub gurnards were not significantly different with the older age classes consisting predominantly of female fish. Both males and females exhibited similar asymptotic growth patterns and the combined von Bertalanffy growth function was TL_t = 51.6 (1 ? e ^{[?0.25(t + 0.41)]}). Instantaneous rates of total mortality were calculated as 1.04 year^?1 for males and 1.11 year^?1 for females. The size (L₅₀) and age at first maturity (A₅₀) were estimated to be 29.1 cm TL and 2.8 years for males, 27.7 cm TL and 2.7 years for females and 28.0 cm TL and 2.8 years for both sexes combined. The results of this study provide the first information on the biology and population dynamics of C. lucerna in the Irish Sea, the first data collected in the northeast Atlantic since 1985 and the most northerly population studied to date.     

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.     

Age and growth of Monopterus albus Zuiew, 1793 (Synbranchidae)

Age and growth of Monopterus albus (Zuiew, 1787) in Lake Nanhu, Wuhan, Hubei Province, China, were studied from January to December 2007. A total of 418 samples were collected ranging from 18 to 86 cm total length (TL). Among these samples, ages of female were 1 ⁺ –5 ⁺ years while males were 3 ⁺ –9 ⁺ years as estimated by basihyal. The length–weight relationships and the von Bertalanffy growth curve were described for all individuals as: W_T = (2 × 10^?7) TL^3.2366 and L_t = 104.1{1‐e^{?0.108 (t + 1.625)}}. To the best knowledge of the authors, this study presents the first reference on the relationship between age and growth of this species for the management of fishery resources.     

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.