A natural hybrid of Leuciscus cephalus (L.) and Chalcalburnus chalcoides (Güldenstädt)(Osteichthyes‐Cyprinidae) from Lake Tödürge (Sivas, Turkey)

Hybridization between Leuciscus cephalus and Chalcalburnus chalcoides was identified from biometrical features in 55 fish caught from Lake Tödürge, Sivas, Turkey, between April 1994 and November 1997. The hybrid index V _h for metric and meristic characters was intermediate ( V _h = 45·6) compared with their parents ( L. cephalus V _h = 0 or negative and C. chalcoides V _h ≥ 100). Morphological, metric and meristic features of L. cephalus  ×  C. chalcoides also resembled those of the parents. The majority presented an intermediate position which was best shown by the shape of mouth, caudal fin, gill rakers and pharyngeal teeth, and also by the caudal peduncle depth, head and interorbital width, predorsal and preanal distance, height of anal fin, length of anal base and other characters.     

Growth and reproduction of Mesopotamian spiny eel (Mastacembelus mastacembelus Banks & Solander, 1794) in Ataturk Dam Lake (Şanliurfa), Turkey

Age at length, growth and reproduction of 220 Mastacembelus mastacembelus specimens from the Atatürk Dam Lake were studied from July 2005 to July 2006. Total lengths and weights ranged from 7.0 to 85.0 cm and from 6 to 1100 g, respectively. Maximum age was 13 years. The regression model fitted to length and weight data was W  =   0.0228  L ^2.43 for males and W  =   0.0029  L ^2.95 for females. The von Bertalaffy growth equations for males and females were L _t  = 99.2 [1−e^{−0.11 ( t −0.12)}] and L _t  = 69.2 [1−e^{−0.26 ( t −0.35)}], respectively. Males dominated especially at an older age; the overall sex ratio was 1 : 0.63 (M:F). The breeding period was from May to July. Fecundity ranged from 2540 to 24 000 eggs per female.     

Assessing mortality changes from size‐frequency curves

The relationship between the instantaneous mortality rate ( Z ) and the instantaneous change in length‐frequency distribution of organisms per unit of animal size (μ _L ) takes the following form: Z  = μ _L k ( L _∞ −  L ) +  k , where k and L _∞ are coefficients of the von Bertalanffy equation, and L is organism size (length). Z and μ_L change coherently when they are measured for a specific size or age class. Therefore, observations of μ _L can provide information on the relative changes in mortality. This is useful when no precise information about animal growth is available and growth curve is assumed to be invariable. This method was tested on a heavily exploited population of St Peter's fish (mango tilapia) Sarotherodon galilaeus in Lake Kinneret, Israel, where large fluctuations in the size structure of the catch have occurred over the past few years. Analysis of the changes in the length‐frequency distributions showed that the changes in μ _L over multiple years estimated for fully exploited fish reflected the respective changes in Z .     

Relationship between opercular girth, maximum girth and total length of fishes caught in gillnets in the estuarine and lower river sections of Shatt al-Arab River (Basrah Province, Iraq)

In fisheries, the two morphological parameters of opercular and maximum girth are related to the effectivity of capture methods in gilled and wedged fish, respectively. The present work investigates the relationship between opercular ( G _ope) and maximum girths ( G _max) to total length ( L _t) for 10 fish species captured from Shatt al-Arab River, Basrah, Iraq. Data were collected October 2005 to December 2006. Cyprinids were the best represented family with six species; engraulids, silurids, heteropneustids and mugilids were each represented by one species. G _ope and G _max were found to increase linearly with total length of all species, all r ² values being greater than 0.73 and statistically significant (P < 0.01). When G _ope and G _max for all species were plotted against total length, two groups were identified ( G 1, G 2), corresponding to general girth-length relationships: (a) G 1 = −0.252 + 0.424 L _t and G 2 = −0.262  +  0.600 L _t for opercular girth and, (b) G 1 = 1.538 + 0.419 L _t and G 2  =  1.538  +  0.696 L _t for maximum girth. These groups correspond to different body shapes of fishes: G 1-round and G 2-compressed. These relationships have implications when using length data and mesh size to determine size selectivity of gill nets.     

Age, growth and reproduction of the barrelfish Hyperoglyphe perciformis (Mitchill) in the western North Atlantic

Otoliths ( n = 847) and gonads ( n = 817) were collected from barrelfish Hyperoglyphe perciformis that were captured by commercial fishermen in the waters off South Carolina and Georgia in 1995, 1997 and 2001–2006. Of the otoliths collected, 97% were aged successfully, and specimens sampled ranged from 5 to 85 years, with a median age of 12 years. The von Bertalanffy growth parameters yielded the equation: L_t = 857·8{1 − e^{−0·0985[ t −(−8·95)]}}, where L_t is fork length ( L _F) at time t . Through histological examination, 94% of the gonads assessed were assigned to a sex and reproductive class. Females spawned from September to May with a peak from November to January. Males spawned year round, but had a peak from September to April. The sex ratio (M:F) for this population was 1:1·34. The smallest mature female was 605 mm L _F and the youngest immature female was 697 mm L _F. Estimates of L _F and age at 50% maturity ( L ₅₀ and A ₅₀) for females were 660 mm L _F (95% CI = 633–667 mm L _F) and 6·08 years (95% CI = 3·50–7·27 years), respectively. The youngest mature male was 575 mm L _F and the oldest immature male was 762 mm L _F, and no estimates of L ₅₀ or A ₅₀ were made for males. It was determined that barrelfish exhibit the typical characteristics of long life span, slow growth and high age at maturity seen in other deepwater fishes, and that care should be taken to manage this species accordingly.     

Age, growth and mortality of the Mediterranean amberjack Seriola dumerili (Risso 1810) from the south-eastern Adriatic Sea

The age, growth and mortality of the Mediterranean amberjack Seriola dumerili (Risso 1810) were determined in 298 specimens collected in the south-eastern Adriatic Sea (Donji Molunat Bay) from 17 May to 26 June 1997. The total length ranged from 32.0 to 160.0 cm and weight from 0.5 to 46.5 kg. Ten age classes, ranging from 1° to 10° years were defined by scale readings. Mean total length and weight-at-age data were used to estimate the growth parameters of the von Bertalanffy equation: L _∞=174.6 cm, K =0.190, t ₀=–0.314; W _∞=79.01 kg, K =0.139 and t ₀=–0.746. The length–weight relationship was estimated at: W =0.000123 ×  L ^2.847. The overall sex ratio was 1 : 1.06 in favour of males. Total ( Z ) and natural ( M ) mortality were found to be 0.41 years⁻¹ and 0.30 years^–1, respectively. The exploitation ratio ( E =0.27) indicates that the fishing pressure on the Mediterranean amberjack was low in the investigated region.     

Age and growth of eels Anguilla japonica in a Chinese river

Age and growth of Anguilla japonica sampled from the Qiulu River in southern China were studied. Mean body lengths and weights of the eels at each age were back-calculated from their otoliths. The growth parameters for the von Bertalanffy function gave L _∞= 98–2cm, K =0·07 and t ₀=− 1·94. Scales were observed to form firstly at the middle part of the lateral line, at a minimum body length of 160 mm and were inappropriate for ageing.     

Morphological development and allometric growth patterns in the juvenile seahorse Hippocampus kuda Bleeker

The morphological development and allometric growth patterns in the juvenile spotted seahorse Hippocampus kuda were studied under hatchery rearing conditions. Newborn spotted seahorses [mean ± s.d . standard length ( L _S) 9·33 ± 0·79 mm] were raised till the age of 124 days (119·35 ± 6·04 mm). Growth was characterized by three stages with two inflexion points occurring at day 21 and 76. The mean growth rates in the first, second and third stages were 0·68, 1·16 and 0·71 mm day⁻¹, respectively. The growth rate was most rapid in the second stage and was probably influenced by a behavioural shift from pelagic to benthic form. The mass ( M ) and L _S relationship was exponential ( M = 7·14 × 10⁻⁶ L _S^2·76), but the slope, b = 2·76, reflected negative allometric growth. Sexes could be distinguished at c. 110 days, and the sex ratio was unbiased. The L _S in males and females did not differ significantly. Morphological stageing series is proposed, which divides H. kuda juvenile development into eight stages based on the development of coronet, cheek and eye spines, keel and pigmentation. The morphometric ratios for all the body parts, except trunk length, showed considerable changes at a transition point occurring at c. 25 mm L _S. The high proportional growth in head length, head depth, pectoral fin base length, dorsal fin base length, snout length, snout depth and eye diameter at the initial stages, and the abrupt increase in tail length only after the first 2 weeks, possibly reflect development priorities during early development where important organs are being developed first for the enhancement of juvenile survival.     

Early growth and juvenile population structure of lemon sharks Negaprion brevirostris in the Atol das Rocas Biological Reserve, off north‐east Brazil

Lemon sharks Negaprion brevirostris were sampled in the Atol das Rocas, a nursery area, on nine occasions from March 1999 to October 2003, during which 157 individuals were tagged and 35 were recaptured. The male : female sex ratio of captured individuals was 1 : 1·12. Mean ±  s . d . growth rates were 24·7 ± 3·4 cm year⁻¹ in total length ( L _T), 20·7 ± 3·2 cm year⁻¹ in fork length, and 19·5 ± 2·7 cm year⁻¹ in precaudal length. There was no significant difference in growth rates between males and females. Mean ±  s . d . increase in mass was 2565 ± 762 g year⁻¹. The von Bertalanffy growth parameters estimated by the Fabens method based on L _T were: k  = 0·077, L _∞ = 399·9 cm and t ₀ = −2·16. Despite the large variation of environmental conditions, particularly of tidal range and currents, and the lack of protective mangrove cover in the nursery area at Atol das Rocas, juvenile lemon sharks grew relatively faster than at other nurseries. Such rapid growth could be a response to abundant food availability or high risk of predation by adults that enter the nursery area.     

Lifetime consequences of variable 0 year group length in riverine populations of chub Leuciscus cephalus (L.)

The fork length ( L _F) of individual chub Leuciscus cephalus in English riverine populations at the end of their first growth season varied considerably, ranging from <25 to >70 mm. This had a significant influence on the subsequent growth of individuals over their lifetime. Chub of small L _F at age 1 year generally produced smaller annual growth increments throughout life than those of longer L _F at age 1 year, although they had the potential to attain greater ultimate L _F. This variability in L _F at age 1 year resulted, at least in part, from multiple spawning events over a protracted period, that caused variation in the growing seasons for 0 year group chub of the same year class. Since the adult population contained individuals that only attained L _F of <25 mm at the end of their first growing season, it is possible that L _F at age 1 year may not be such a major precursor to strong chub recruitment as previously thought.     

The reproduction, age and growth of the spotted rockling

Biology of the Macaronesian endemic rockling Gaidropsarus guttatus was studied in the Azores. The overall sex ratio from the samples was highly in favour of females (1 : 6·33). The growth parameters were L _∞ = 24·23, k  = 1·219 and t ₀ = −0·059. Fish matured at 15 cm L _T and the spawning season was strongly clustered in April.     

Mackerel icefish size and age differences and long‐term change at South Georgia and Shag Rocks

This study analysed the total length ( L _T)‐frequency distribution of mackerel icefish Champsocephalus gunnari at South Georgia and Shag Rocks from nine bottom trawl surveys at South Georgia and eight at Shag Rocks between 1987 and 2002. The estimated mean L _T of age‐classes 1+, 2+, 3+ and 4+ years during January were, respectively, 14·7, 23·5, 29·8 and 35·1 cm at South Georgia. Age‐classes 1+, 2+ and 3+ years were 18·3, 26·2 and 33·8 cm at Shag Rocks. The derived Bertalanffy growth parameters for South Georgia were: L _∞ = 51·7 cm, k  = 0·27 and t ₀ = −0·26. The mean L _T of each age‐class of C. gunnari at Shag Rocks was significantly larger than at South Georgia, equivalent to c . 5 months growth, although the annual growth in L _T was similar. This is further evidence that C. gunnari hatched earlier at Shag Rocks. At South Georgia, the mean L _T of age‐classes 1+ and 3+ years were correlated, and significantly decreased between 1987 and 2002, and were smaller following warmer summers. This decrease in the size of C. gunnari may be the result of reduced food availability linked to climate warming.     

Age and growth of the striped mullet, Mugil platanus (Actinopterygii, Mugilidae), in a southwestern Atlantic coastal lagoon (37°32'S–57°19'W): a proposal for a life-history model

Species of Mugilidae are an important economic resource supporting several small communities in Argentina and Brazil through fishing. The growth parameters of the von Bertalanffy model, age limit ( t _0.95) and natural mortality ( M ) for the striped mullet ( Mugil platanus ) Günther, 1880, in the Mar Chiquita coastal lagoon (37°32'S–57°19'W) were estimated. These results constitute the first estimated values for the species as: L _∞ (cm) = 563.82; K (years⁻¹) = 0.30; t ₀ (years) = −0.057 (age groups 1–8); t _0.95 = 10.07 years and M  = 0.30. Moreover, a hypothetical model is proposed for the life history of the adult stock of M. platanus from the Mar Chiquita coastal lagoon based on CPUE data, environmental parameters, ovarian maturity stages, gonadosomatic indexes, the allometric growth coefficient b and deposition of hyaline or opaque rings in the otholiths. Mugil platanus is therefore regarded as a species of moderate to rapid growth rate, with a relatively low longevity and a high natural mortality rate, compared to other species of Mugilidae.     

Biology of the salema, Sarpa salpa (L. 1758) (Pisces, Sparidae) from the middle-eastern Adriatic

Salema Sarpa salpa (Linnaeus, 1758), were caught in the middle-eastern Adriatic Sea from August to November 2004. Length range of the samples was between 10.3 and 43.9 cm, with mean values of 25.5 cm in males, 32.6 cm in females, and 11.4 and 20.2cm in immature and hermaphrodite specimens, respectively. Sex ratio (males : females) was 3.1 : 1. Males were observed up to 37 cm length. Hermaphrodites showed lengths between 18 and 21 cm. The species was characterized by protandric hermaphroditism. Size at sexual maturity was 20.6 cm (2 years old) for males. Total length-total weight relationship for the entire population is described by the parameters a  = 0.00893, and b  = 3.1055. Otolith age readings showed that the population consisted of 15 age groups (1–15 years), including a very high proportion of individuals 1–7 years old. The von Bertalanffy growth parameters were L _∞ = 33.11cm, k  = 0.514, and t ₀ = −0.392 years for males and L _∞ = 40.85cm, k  = 0.179, and t ₀ = −2.606 years for females. Survival rate of females ( S  = 0.870) was much greater than for males ( S  = 0.769).     

Reproduction, age and growth of Sillago maculata in south-eastern Australia

Sillago maculata is endemic to the east coast of Australia where it is harvested by recreational and commercial fishers; however, little is known of the important aspects of its biology and ecology to assist with fisheries management planning. This situation is redressed here by investigating aspects of the reproduction, age and growth of estuarine populations of S. maculata in south-eastern Australia. Gonadosomatic index (GSI) values indicated peak spawning occurred between September and February and that the estimated mean fork length at maturity (L₅₀) was 14.6 cm for males and 15.2 cm for females. Females displayed an asynchronous pattern of oocyte development, with individuals probably spawning multiple times in a spawning season. A validated aging protocol using thin sectioned otoliths was used to estimate the age of fish. The maximum ages for males and females were 9.5 and 12.0 years, respectively. Growth differed between sexes, with males ( L ∞ = 24.04, K  = 0.70, t ₀ = −0.09) attaining a smaller maximum length than females ( L ∞ = 25.01, K  = 0.72, t ₀ = −0.04). The age composition of gill-net and beach-seine samples mainly consisted of individuals aged 2–4 years, and there was evidence of variable recruitment. Management implications are also discussed.     

Population structure, growth, mortality and estimated stock size of the introduced tench, Tinca tinca (L.), population in Lake Beyşehir, Turkey

Population structure, growth, length–weight relationship, mortality and stock size of tench, Tinca tinca (L.), was studied in Lake Beyşehir, Turkey in 2005. Totals of 3360 tench (1865 males; 1795 females) were captured with gill- and trammel-nets of various mesh sizes. Male to female ratio was 1.04 : 1. The study covered length year classes. Fork lengths and total weights ranged from 9 to 37 cm and 13 to 815 g. For all individuals, the von Bertalanffy growth equation and length–weight relationship were L _t = 54.2[1−exp(−0.1350( t  + 1.0281)] and W  = 0.0151  L ^2.9993, respectively. Growth performance index and mean condition factor of the tench population were 2.598 and 1.513, respectively. Mortality rates were Z  = 1.97 year⁻¹, M  = 0.29 year⁻¹ and F  = 1.68 year⁻¹ for total, natural, and fishing mortality, respectively. The exploitation rate was E  = 0.85, and the percentage of surviving fish was 13.9%. Tench stock was assessed as about 6–7 million individuals and 1450–1500 tonnes in biomass. It was determined that maximum sustainable yield could be obtained with an 80% level of the current fishing effort.     

Biometrics of Sardinella longiceps Val. in relation to upwelling in the Gulf of Aden

Growth, size composition, condition factor and gonad index of the oil sardine, Sardinella longiceps Val., oscillated over an annual cycle in relation to upwelling. Growth in length was modelled using the formula of Pauly & Gaschütz (1979): where L _t= length cm at age t years, L_∞= 23.8cm, K=0.97, t_o=0.70, C=1.08 and t_s=−0.08. The relationship of growth rate, spawning, and condition factor, to upwelling and plankton blooms is discussed.     

Population structure, growth and reproduction of roughhead grenadier on the Flemish Cap and Flemish Pass

Roughhead grenadier Macrourus berglax were collected during the Flemish Cap bottom survey (1991–2001, NAFO division 3M, depth of 200–720 m) and on commercial vessels (1998–2000, NAFO divisions 3L, M and N, depth of 700–1700 m). The abundance of roughhead grenadier, as well as their average size, increased with depth. Age and length composition of the catches showed clear differences between the sexes. The proportion of males in the catch declined in the larger length classes and there were no males in the largest length classes (25 cm). There were differences in the growth trajectories of the two sexes; both sexes grew similarly up to 9 years, but the male growth was slower thereafter. The pre-anal fin length at first maturity ( L _PA50) for roughhead grenadier females was 28·5 cm, whilst the age at 50% maturity was 15–16 years. Individual total fecundity varied between 8522 and 61 844 oocytes. Macrourus berglax had a prolonged life cycle and multi-aged population structure, with differences in growth and mortality between males and females, slow maturation and low fecundity.     

大鳍异鰔年龄与生长

于2013年11月至2014年9月, 在怒江、槟榔江和龙川江共采集大鳍异鲦(Creteuchiloglanis macropterus)230尾, 对其年龄与生长特征进行了研究。结果表明: 以胸鳍棘作为大鳍异鲦年龄鉴定材料, 鉴定结果与脊椎骨的吻合率为86.36%, 胸鳍棘是比较可靠的年龄鉴定材料。所采集样本年龄范围为1—9龄, 1—3龄为主, 占65.00%。雌雄个体生长不存在显著差异, 全长与胸鳍棘半径呈幂函数关系, L=2.0787·R_C0.6273(R2=0.8866, n=180)。各龄组实测体长均值和退算体长均值无明显差异(χ2=0.776, df=8, P=0.999)。雌雄群体实测全长与体重之间无明显差异, 拟合得体重与全长的关系式为: W=1E–4L2.4807(R2=0.8189, n=180), 其生长属异速生长类型。生长规律用von Bertalanffy方程表示, L_t=377.015·[1–e–0.0491(t+4.0195)], W_t=246.134·[1–e–0.0491(t+4.0195)]2.4807。生长拐点年龄为14.48龄, 拐点处的全长和体重分别为225.00 mm和68.40 g。大鳍异鲦个体出现小型化现象, 应合理捕捞、加强保护。     

Validation of roughhead grenadier (Macrourus berglax) otolith reading

Roughhead grenadier Macrourus berglax Lacépède 1802, is becoming an important commercial fish in the north-west Atlantic fisheries and reliable age information is needed for its assessment. Macrourus berglax has been aged by counting otolith growth zones assumed to represent anulli. Three validation methods were applied: back-calculation of length-at-age, length–frequency analysis, and analyses of the progression of the length mode of an exceptionally large year class. Results on size-at-age estimated by otolith growth zone counts, length–frequency analysis of pre-anal fin length and modal progression were internally consistent, but estimates by back-calculation were different. This latter method produces unrealistic growth curves for each sex due to the weak relationship between otolith size as measured and pre-anal fin length. Up to age 8–9 the size-at-age were the same for males and females; thereafter males were smaller than females. Male growth rate declined when pre-anal fin length reached 18 cm at around age 9, whereas the growth of females started to decline at about 30 cm at around age 16. The Von Bertalanffy growth model derived from otolith analysis was similar to that obtained by the Multifan length frequency analysis model, and gave realistic values of L _inf, close to the maximum anal fin lengths found in catches. The results showed that Macrourus berglax has a prolonged life cycle and differences in growth between males and females.