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 maturity of the yellownose skate Dipturus chilensis in the south‐eastern Pacific

The age and growth parameters of Dipturus chilensis were estimated by counting growth rings from thin sections of vertebral centra from 400 fish (246 females and 154 males), ranging from 23 to 124 cm total length (L_T), and backcalculating fish lengths at previous ages. Marginal increment analysis lent support to the hypothesis of annual deposition of band‐pairs, which formed during the winter months. The oldest female D. chilensis aged in this study was 21 years and 117 cm L_T, whereas the oldest male was 18 years and 93 cm L_T. A 4·7% index of average per cent error (I_APE) suggested that this is a precise method for calculating the age of D. chilensis. Observed L_T were lower than backcalculated L_T, which implies the influence of Lee's phenomenon. The von Bertalanffy growth equations, based on mean length‐at‐age data, were estimated as L_t = 128·3 (1 ? e^{?0·112 (t + 0·514)}) for females and L_t = 107·8 (1 ? e^{?0·134 (t + 0·862)}) for males where t is age (years). Growth was significantly different between sexes: females reached a larger adult size. Ages and lengths at 50% maturity were estimated at 14 years of age and 106 cm L_T for females and 11 years of age and 86 cm L_T for males. At c. 14 years, there was a decline in growth rates in females. The factor most likely responsible for this was sexual maturity, which caused a discontinuity in growth of female fish. These results show that this species is slow‐growing, long‐lived, relatively large and of delayed maturity, characteristics that make it vulnerable to exploitation.     

Population biology of the red gurnard (Aspitrigla cuculus L.; Triglidae) in the inshore waters of Eastern Anglesey and Northwest Wales

ICES has identified red gurnard Aspitrigla cuculus (L.) as a potential commercial species and recommended that monitoring programmes should be conducted to derive information on biological parameters for stock assessment purposes. In this paper, data on the population biology of red gurnard in the coastal waters of Northwest Wales and Eastern Anglesey are presented. Total length (TL) of fish sampled ranged from 15.4 to 35.0 cm (males) and 10.5 to 43.1 cm (females), with the majority of females between 20 and 30 cm TL (70.0%) and males between 20 and 30 cm TL (71.0%). TL/weight (W) relations were similar between immature and mature individuals for both sexes and between both sexes (all maturity stages combined), producing a combined data equation W = 0.005 TL^3.19. Age of fish ranged from 1 to 7 years and 1 to 6 years, respectively, for females and males, with the majority of females age 3 (37%) and the majority of males age 2 (49%). The age structures of female and male red gurnards were significantly different, with the older age classes consisting predominantly of female fish. Both males and females exhibited similar asymptotic growth patterns; the combined von Bertalanffy growth function was . Instantaneous rates of total mortality were calculated as 1.13 year^?1 for males and 0.98 year^?1 for females. The size (L₅₀) and age at first maturity (A₅₀) were estimated to be 26.3 cm TL and 3.6 years for males, 28.1 cm TL and 3.5 years for females and 25.6 cm TL and 3.7 years for both sexes combined.     

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.     

Population biology of grey gurnard (Eutrigla gurnardus (L.); Triglidae) in the coastal waters of Northwest Wales

The grey gurnard Eutrigla gurnardus (L.) has been identified by ICES as a potential commercial species in the NE Atlantic with recommendations made to derive information on population biology for stock assessment purposes. However, data on the population biology of this species is limited. In this study, data on the age, growth and maturity of grey gurnard were collected by otter trawling in the coastal waters of northwest Wales and Eastern Anglesey. Total length (TL) of fish sampled ranged between 2.1–33.0 cm (male) and 1.9–36.9 cm (female) with the majority of female (70.8%) fish between 11 and 20 cm TL and male fish (70.5%) between 11 and 18 cm TL. The percentage of fish >20 cm TL was larger for females (30.4%) compared to males (17.6%). Total weight (TW) for female and male grey gurnard in the stratified subsample ranged from 1.9 to 499.9 g for females and 2.1–390.0 g for males, with the majority of female (66.3%) and male (76.1%) fish between 10 and 60 g. TL/TW relations for male and female fish and both sexes combined were: TW = 0.006TL^3.07, TW = 0.007TL^3.03 and TW = 0.007TL^3.05 respectively. Age structure (based on otolith reading) ranged between 0.5 and 7.5 years old for females and 0.5 to 5.5 years old for male with the majority of female (41.7%) and male (46.0%) fish aged as 1.5 years old. The age structure of female and male grey gurnards was significantly different with the majority of older fish (>2.5 years) being female. The von Bertalanffy growth functions were calculated as L_t = 32.4[1 ? e^{?0.24(t + 1.41)}] for males, L_t = 45.9[1 ? e^{?0.16(t + 1.37)}] for females and L_t = 44.0[1 ? e^{?0.18(t + 1.20)}] for both sexes combined. Instantaneous rates of total mortality were similar for males and females and the combined Z value 1.00 year^?1 with the natural mortality rate estimated as 0.33 year^?1. The size at 50% maturity (L₅₀) was estimated to be 25.3 cm TL for males, females and for both sexes combined. Age at 50% maturity (A₅₀) was 3.2 years for both males and females. The results of this study provide the first information on the population biology of E. gurnardus in the Irish Sea, the first detailed study in the NE Atlantic since 1985 and helps to address the data gap identified by ICES in knowledge of the population biology of this species.     

AGE,GROWTH, AND REPRODUCTIVE PATTERNS OF DALL'S PORPOISE (PHOCOENOIDES DALLI) IN THE CENTRAL NORTH PACIFIC OCEAN

Life history parameters were estimated for Dall's porpoise, Phocoenoides dalli, from biological specimens collected in the western Aleutian Islands, during 1981–1987. Of 2,033 males and 3,566 females examined, reproductive data were available for 1,941 males and 1,906 females; ages were determined for 813 males and 1,297 females. Female sexual maturity was based on the presence of one or more corpus on either ovary; 845 were sexually immature and 1,061 were sexually mature. Two estimates of female average age at sexual maturity (ASM) were 3.8 and 4.4 yr; average length at sexual maturity (LSM) was 172 cm. Males were considered sexually mature when evidence of spermatogenesis was detected; 1,136 were sexually immature and 805 were sexually mature. Two estimates of male ASM were 4.5 and 5.0 yr; LSM was 179.7 cm. Physical maturity was assessed for 246 males and 446 females by examining the degree of fusion in thoracic vertebral epiphyses. For both sexes, the average age at physical maturity was 7.2 yr. Average length at physical maturity was 202.6 cm for males and 192.7 cm for females. Average lengths of physically mature males (x?= 198.1 cm, SE = 0.8566) and females (x?= 189.7 cm, SE = 0.4002) were significantly different(P < 0.0001). Early postnatal growth was rapid in both sexes. A secondary growth spurt in both mass and length was characteristic for both sexes; the increase in length preceded the mass increase by 1–2 yr. Average length at birth (LOB) was approximately 100 cm; birth mass averaged 11.3 kg (SE = 0.0772). By the time the umbilicus had healed (<2 mo), the average length and mass had increased to 114.1 cm and 23.8 kg, respectively. Gestation period based on projections using LOB was 12 mo, but this was considered an overestimate. Calving was modal, centered in early July; an annual reproductive interval was indicated. Among the sexually mature females, 120 were pregnant, 55 were pregnant and lactating, 321 were pregnant with colostrum, and 33 were “resting.” By 3 July (95% CI =x? 1 d), 50% of births had occurred, during each of the seven years sampled. The ovulation rate was estimated at 0.914 ovulations per average reproductive year. Enlarged follicles and recent ovulations were observed in postpartum females in late July.     

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.     

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 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-based life history of humpback red snapper,Lutjanus gibbus,in New Caledonia

This paper examines the life history of humpback red snapper Lutjanus gibbus, an important fishery species for coastal communities across the Indo-Pacific, in southern New Caledonia, where the species is lightly exploited. A total of 243 L. gibbus were sampled between January 2013 and December 2016 from occasional harvests of commercial fishers. Examination of sectioned otoliths revealed that opaque increment formation occurred annually between November and March, coinciding with the species' spawning season. Estimates of maximum age were similar between sexes, with observed ages of 38 and 36 years for females and males, respectively, extending the reported longevity of this species by at least 11 years. Growth differed significantly between sexes, with males reaching greater length at age and greater asymptotic length than females (38.88 v. 31.46 cm fork length (L_F). Total mortality for all samples was estimated as 0.13 and was slightly higher for males (0.16) than females (0.11). Estimates of natural and fishing mortality were low and slightly higher for males than females. Male L. gibbus were found to mature at slightly greater lengths and younger ages than females, with the length and age at which 50% of individuals attained maturity estimated to be 25.8 cm L_F and 3.9 years of age for females and 26.8 cm L_F and 3.4 years of age for males. The results provide key baseline information from which to assess the effect of fishing on the species for populations in New Caledonia and adjacent locations and, when viewed with those of other studies, highlight the importance of understanding spatial patterns in demography of harvested fish species across gradients of exploitation and environmental influences.     

Age and growth of damselfish Chromis notata (Temminck & Schlegel, 1843), Jeju Island,Korea

This study investigated the age and growth of damselfish, Chromis notate, from Jeju Island in Korea. Samples were collected monthly by lift net from September 2013 to August 2014. Total lengths of the damselfish ranged from 6.4 to 15.3 cm. The relationship between total length and wet weight was WW = 0.0125TL^3.1631 for females, and WW = 0.0091TL^3.2769 for males. The slopes in the relationship between length and weight were not significantly different between sexes, but were significantly different in the intercepts. There were more female than male specimens (1.3:1). Age determination was conducted using the otoliths. Marginal increment (MI) declined in summer and winter, which suggests that two rings are formed each year. Ages of sampled individuals ranged from 1 to 5 years. Length‐at‐age data were fitted using the von Bertalanffy growth model. The estimated growth functions were L_t = 19.93 [1 ? exp^{?0.21 (t + 0.811)}] total length and wet weight was females, and L_t = 16.47 [1 ? exp^{?0.32 (t + 0.499)}] for males.     

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.     

Patterns of reproduction and growth of the catfish Iheringichthys labrosus (Lütken, 1874) after a reservoir formation

This work contributes to the knowledge of the reproduction, growth parameters and mortality rates of Iheringichthys labrosus in a newly‐formed reservoir. A total of 554 males and 1227 females were collected over 12 consecutive months, 1998–1999, from sites in the Corumbá Reservoir, Brazil, using gillnets (meshes: 2.4–16 cm). Information on each individual, i.e. standard length (cm), weight (g), sex, and gonadal development phase was recorded. The pectoral spines were removed to estimate age. The number of juveniles and adults, males and females, reproductive sites and seasons were estimated. First maturation length was estimated using a likelihood function fitted by binomial distribution. Growth parameters were estimated using the von Bertalanffy equation. Total instantaneous mortality was obtained through a linearized catch curve method. Standard length varied from 6.0 to 20.5 cm. Growth showed negative allometry for both sexes. The reproduction period was August to December in all environments sampled and first maturation length was 11.5 cm. All individuals were adults with 17.0 cm standard length. Ages varied from zero to 7 years. Asymptotic length, growth coefficient and t₀ for the entire population were 27.79 cm, 0.12 and ?2.64, respectively. Instantaneous and annual mortality rates were 0.90 and 0.59, respectively.     

The population biology of the exploited crab Ucides cordatus (Linnaeus, 1763) in a southeastern Atlantic Coast mangrove area,Brazil

Ucides cordatus (Linnaeus, 1763), found in mangroves along the Brazilian coast, is an artisanal fishery resource harvested as a source of income and for subsistence. A 12?month study of U. cordatus was conducted in a mangrove area of the southeastern Brazilian coast to estimate the growth, longevity, sex ratio and population density of the crabs. A total of 1024 crabs (505 males and 519 females) were sampled. Carapace width (CW) ranged from 49 to 90?mm (mean?±?SD: 71.2?mm?±?6.0) for males and from 52 to 83?mm (69.3?mm?±?4.9) for females. Males dominated the largest CW classes. The asymptotic size (CW_∞) and the asymptotic weight (WW_∞) were estimated as 93.4?mm and 305.5?g, respectively, for males and as 87.1?mm and 221.5?g, respectively, for females. The estimated maximum longevities were 17.6?years for males and 15.7?years for females. The males (k?=?0.17, Φ?=?1.171) and females (k?=?0.19, Φ?=?1.159) showed similar growth rates. The mean density was 0.41?±?0.19?burrows?m^?2. Of this total mean density, 85.8% corresponded to the immediate harvesting potential and 14.2% to the future harvesting potential. Given that U. cordatus is a long-lived species that grows slowly, an appropriate strategy for the management is crucial to ensure the sustainable exploitation of this resource.     

Population parameters and exploitation rate of Sarotherodon galilaeus galilaeus (Cichlidae) in Lakes Doukon and Togbadji,Benin

Growth, mortality, recruitment and relative yield per recruit of Sarotherodon galilaeus galilaeus from Lakes Doukon and Togbadji were studied. Data on total length, total weight and sex were recorded on a monthly basis between January and December 2013 for S. g. galilaeus captured by local fishers. The estimated asymptotic lengths L_∞ were 26.2 and 23.6?cm for Lakes Doukon and Togbadji, respectively, while the growth rate K was 0.73 in Lake Doukon and 0.87 in Lake Togbadji. Estimates of fishing mortality, 0.27 and 0.47 y^?1 for Doukon and Togbadji, respectively, were low relative to natural mortality, 1.51 and 1.74 y^?1, respectively. Sizes at first sexual maturity were 12.8 and 13.2?cm for females and males, respectively, in Lake Doukon, and 11.5 and 12.4?cm for females and males, respectively, in Lake Togbadji. The size at first capture was estimated at 13.3 and 12.7?cm for Lakes Doukon and Togbadji, respectively, which, in the light of the size at maturity estimates, indicates that fish spawn at least once before capture. The current exploitation rates of 0.15 for Lake Doukon and 0.21 for Lake Togbadji suggest that their stocks of S. g. galilaeus are not overexploited in either lake.     

Swimming behavior and morphometry of the file shell Limaria fragilis

Swimming has evolved in only a few orders of Bivalves. In this study, the behavior, morphometry, and mechanics of swimming in the file shell Limaria fragilis were characterized and compared to the better understood scallops. Absolute swimming speed (cm?sec^?1) increased with increasing shell height, although relative swimming speed (body lengths?sec^?1) did not covary with shell height. The increase in absolute swimming speed was due to an increase in the distance covered during each valve clap as clap distance (cm?clap^?1) also increased with shell height while clapping frequency (claps?sec^?1) did not covary with animal size. Limaria fragilis displayed a variety of morphological changes related to size. Shell length was negatively allometric with shell height indicating the shell became proportionately slimmer in larger animals. Dry shell mass was negatively allometric with shell height, while both dry adductor muscle mass and dry mantle + tentacle mass were positively allometric. Autotomy of mantle tentacles significantly decreased clap distance by 13% without affecting clapping frequency or swimming speed.     

Age,growth and mortality of invasive sharpbelly,Hemiculter leucisculus (Basilewski, 1855) in Erhai Lake,China

The sharpbelly Hemiculter leucisculus, an invasive species, has expanded its range throughout much of Asia and into the Middle East. However, little is known of its adaptive changes regarding life history traits such as age, growth and mortality that could possibly explain its success as an invasive species. A detailed study of the invasive sharpbelly was conducted based on 4539 samples collected from July 2009 to June 2011 in Erhai Lake, China. Standard length ranged from 4.3–19.1 cm for females and 4.6–12.3 cm for males. Length–weight relationships for females and males were significantly different and described as W = 0.0076SL^3.2608 and W = 0.0084SL^3.1901, respectively. Otoliths are ideal for age determination because of the single annulus formed each year. Based on marginal increment analysis, the total mean CV for age estimate between two readings was 3.55%. The von Bertalanffy growth curves computed by observed length‐at‐age data were expressed as L_t = 25.6 (1 ? e^{?0.176 (t + 1.347)}) for females and L_t = 16.4 (1 ? e^{?0.354 (t + 0.819)}) for males. According to the age, growth and mortality data, there are three possible reasons for H. leucisculus attaining such dominance within a short time in Erhai Lake. First, because of the simple age structure of this species: 97.58% of males were 1–2 years old with a maximum age of only 3 years; 93.14% of females were 1–3 years old, with a maximum age of 6 years. Second, females grew larger than males at any age. Third, instantaneous mortality rates were much higher for males (4.22 year^?1) than for females (1.17 year^?1).     

Population structure,spatial distribution and life‐history traits of blacktip reef sharks Carcharhinus melanopterus

During a survey of the population of blacktip reef shark Carcharhinus melanopterus in Moorea (French Polynesia) between 2007 and 2011, population structural characteristics were estimated from 268 individuals. Total length (L_T) ranged from 48 to 139 cm and 48 to 157 cm for males and females, respectively, demonstrating that the average L_T of females was larger than that of males. The C. melanopterus population at Moorea showed an apparent spatial sexual segregation with females preferentially frequenting lagoons and males the fore‐reefs. Mean growth rate was c. 6 cm year^?1. Males reached sexual maturity at 111 cm L_T. This study reports on the population characteristics of this widespread carcharhinid shark species and makes comparisons with other locations, confirming high geographic variability in the population structure of the species.