Life‐history traits of the long‐nosed skate Dipturus oxyrinchus

This work investigates life‐history traits of the long‐nosed skate Dipturus oxyrinchus, which is a common by‐catch in Sardinian waters. The reproductive variables were analysed from 979 specimens sampled during scientific and commercial hauls. Females (10·4–117·5 cm total length, L_T) attained larger sizes than males (14·5–99·5 cm L_T). To evaluate age and growth, a sub‐sample of 130 individuals (76 females and 54 males) were used. The age was estimated by annuli counts of sectioned vertebral centra. Four models were used for the length‐at‐age data: the von Bertalanffy, the exponential, the Gompertz and the logistic functions. According to the Akaike's information criterion, the Gompertz model seemed to provide the best fitting curve (L_∞ mean ± s.e. : 127·55 ± 4·90 cm, k: 0·14 ± 0·09, IP: 3·97 ± 0·90 years). The oldest female and male were aged 17 (115·5 cm L_T) and 15 years (96·0 cm L_T), respectively. Lengths at maturity were 103·5 cm for females and 91·0 cm for males, corresponding to 90% of the maximum observed length in both sexes. The monthly distribution of maturity stages highlighted an extended reproductive cycle, with spawning females and active males being present almost throughout the year, as confirmed by the gonado‐somatic index. Ovarian fecundity reached a maximum of 26 yolked follicles with a mean ± s.e. size of 19·7 ± 6·5 mm.     

Effects of age‐based movement on the estimation of growth assuming random‐at‐age or random‐at‐length data

Simulation methods were used to generate paired data from a simulated population that included the age‐based process of movement and the length‐based process of gear selection. The age‐based process caused bias in the estimates of growth parameters assuming random at length, even when relatively few age classes were affected. Methods that assumed random at age were biased by the subsequent inclusion of the length‐based process of gear selection. Additional knowledge of the age structure of the sampled area is needed to ensure an unbiased estimate of the growth parameters when using the length‐conditional approach in the presence of age‐based movement. Estimates of the variability in the length‐at‐age relationship were better estimated with the length‐conditional than the traditional method even when the assumptions of random at length were violated. Inclusion of paired observations of length and associated age inside the population dynamics model may be the most appropriate way of estimating growth.     

Life‐history strategies of the rock hind grouper Epinephelus adscensionis at Ascension Island

Epinephelus adscensionis sampled from Ascension Island, South Atlantic Ocean, exhibits distinct life‐history traits, including larger maximum size and size at sexual maturity than previous studies have demonstrated for this species in other locations. Otolith analysis yielded a maximum estimated age of 25 years, with calculated von Bertalanffy growth parameters of: L_∞ = 55·14, K = 0·19, t₀ = ?0·88. Monthly gonad staging and analysis of gonad‐somatic index (I_G) provide evidence for spawning from July to November with an I_G peak in August (austral winter), during which time somatic growth is also suppressed. Observed patterns of sexual development were supportive of protogyny, although further work is needed to confirm this. Mean size at sexual maturity for females was 28·9 cm total length (L_T; 95% C.I. 27·1–30·7 cm) and no females were found >12 years and 48·0 cm L_T, whereas all confirmed males sampled were mature, >35·1 cm L_T with an age range from 3 to 18 years. The modelled size at which 50% of individuals were male was 41·8 cm (95% C.I. 40·4–43·2 cm). As far as is known, this study represents the first comprehensive investigation into the growth and reproduction of E. adscensionis at its type locality of Ascension Island and suggests that the population may be affected less by fisheries than elsewhere in its range. Nevertheless, improved regulation of the recreational fishery and sustained monitoring of abundance, length frequencies and life‐history parameters are needed to inform long‐term management measures, which could include the creation of marine reserves, size or temporal catch limits and stricter export controls.     

Age and growth parameters of shark‐like batoids

Estimates of life‐history parameters were made for shark‐like batoids of conservation concern Rhynchobatus spp. (Rhynchobatus australiae, Rhynchobatus laevis and Rhynchobatus palpebratus) and Glaucostegus typus using vertebral ageing. The sigmoid growth functions, Gompertz and logistic, best described the growth of Rhynchobatus spp. and G. typus, providing the best statistical fit and most biologically appropriate parameters. The two‐parameter logistic was the preferred model for Rhynchobatus spp. with growth parameter estimates (both sexes combined) L_∞ = 2045 mm stretch total length, L_ST and k = 0·41 year^?1. The same model was also preferred for G. typus with growth parameter estimates (both sexes combined) L_∞ = 2770 mm L_ST and k = 0·30 year^?1. Annual growth‐band deposition could not be excluded in Rhynchobatus spp. using mark‐recaptured individuals. Although morphologically similar G. typus and Rhynchobatus spp. have differing life histories, with G. typus longer lived, slower growing and attaining a larger maximum size.     

The influence of local environment on the aging and mortality ofAedes aegypti (L.): Case study in Fortaleza‐CE,Brazil

It is generally assumed that the daily probability of survival of mosquitoes is independent of age. To test this assumption we have conducted a three‐year experimental fieldwork study (2005–2007) at Fortaleza‐CE in Brazil, determining daily survival rates of the dengue vector Aedes aegypti (L.). Survival rates of adult Ae. aegypti may be age‐dependent and the statistical analysis is a sensitive approach for comparing patterns of mosquito survival. The mosquito survival data were better fit by a Weibull survival function than by the more traditionally used Gompertz or logistic survival functions. Gompertz, Weibull, or logistic survival functions often fit the survival, and the tails of the survival curves usually appear to fall between the values predicted by the three functions. We corroborate that the mortality of Ae. aegypti in semi‐natural conditions may no more be considered as a constant phenomenon during the life of adult mosquitoes but varies according to the age and environmental conditions under a tropical climate. This study estimates the variability in the survival rate of Ae. aegypti and environmental factors that are related to such variability. The statistical analysis shows that the fitting ability, concerning the hazard function, was in decreasing order: Seasonal Cox, the three‐parameter Gompertz, and the three‐parameter Weibull, that was similar to the three‐parameter logistic. The advantage of using the Cox model is that it is convenient for exploring the relationship between survival and several explanatory variables. The Cox model has the advantage of preserving the variable in its original quantitative form and of using a maximum of information. The survival analyses indicate that mosquito mortality is both age‐ and environment‐dependent.     

Slow growth of the overexploited milk shark Rhizoprionodon acutus affects its sustainability in West Africa

Age and growth of Rhizoprionodon acutus were estimated from vertebrae age bands. From December 2009 to November 2010, 423 R. acutus between 37 and 112 cm total length (L_T) were sampled along the Senegalese coast. Marginal increment ratio was used to check annual band deposition. Three growth models were adjusted to the length at age and compared using Akaike's information criterion. The Gompertz growth model with estimated size at birth appeared to be the best and resulted in growth parameters of L_∞ = 139·55 (L_T) and K = 0·17 year^?1 for females and L_∞ = 126·52 (L_T) and K = 0·18 year^?1 for males. The largest female and male examined were 8 and 9 years old, but the majority was between 1 and 3 years old. Ages at maturity estimated were 5·8 and 4·8 years for females and males, respectively. These results suggest that R. acutus is a slow‐growing species, which render the species particularly vulnerable to heavy fishery exploitation. The growth parameters estimated in this study are crucial for stock assessments and for demographic analyses to evaluate the sustainability of commercial harvests.     

Age,growth and maturity of the pelagic thresher Alopias pelagicus and the scalloped hammerhead Sphyrna lewini

Indonesia has the greatest reported chondrichthyan catches worldwide, with c.110,000 t caught annually. The pelagic thresher (Alopias pelagicus) and scalloped hammerhead (Sphryna lewini) together comprise about 25% of the total catches of sharks landed in Indonesia. Age and growth parameters were estimated for A. pelagicus and S. lewini from growth‐band counts of thin‐cut vertebral sections. Alopias pelagicus (n = 158) and S. lewini (n = 157) vertebrae were collected from three Indonesian fish markets over a 5 year period. A multi‐model analysis was used to estimate growth parameters for both species. The models of best fit for males and females for A. pelagicus was the three‐parameter logistic (L_∞ = 3169 mm L_T, k = 0·2) and the two‐parameter von Bertalanffy models (L_∞ = 3281 mm L_T, k = 0·12). Age at maturity was calculated to be 10·4 and 13·2 years for males and females, respectively, and these are the oldest estimated for this species. The samples of S. lewini were heavily biased towards females, and the model of best fit for males and females was the three‐parameter Gompertz (L_∞ = 2598 mm L_T, k = 0·15) and the two‐parameter Gompertz (L_∞ = 2896 mm L_T, k= 0·16). Age at maturity was calculated to be 8·9 and 13·2 years for males and females, respectively. Although numerous age and growth studies have previously been undertaken on S. lewini, few studies have been able to obtain adequate samples from all components of the population because adult females, adult males and juveniles often reside in different areas. For the first time, sex bias in this study was towards sexually mature females, which are commonly lacking in previous biological studies on S. lewini. Additionally, some of the oldest aged specimens and highest age at maturity for both species were observed in this study. Both species exhibit slow rates of growth and late age at maturity, highlighting the need for a re‐assessment of the relative resilience of these two globally threatened sharks at current high levels of fishing mortality throughout the eastern Indian Ocean.     

Estimating age‐dependent survival when juveniles resemble females: Invasive ring‐necked parakeets as an example

Many species only show sexual dimorphism at the age of maturity, such that juveniles typically resemble females. Under these circumstances, estimating accurate age‐specific demographic parameters is challenging. Here, we propose a multievent model parameterization able to estimate age‐dependent survival using capture–recapture data with uncertainty in age and sex assignment of individuals. We illustrate this modeling approach with capture–recapture data from the ring‐necked parakeet Psittacula krameri. We analyzed capture, recapture, and resighting data (439 recaptures/resightings) of 156 ring‐necked parakeets tagged with neck collars in Barcelona city from 2003 to 2016 to estimate the juvenile and adult survival rate. Our models successfully estimated the survival probabilities of the different age classes considered. Survival probability was similar between adults (0.83, 95% CI = 0.77–0.87) and juveniles during their second (0.79, 95% CI = 0.58–0.87) and third winter (0.83, 95% CI = 0.65–0.88). The youngest juveniles (1st winter) showed a slightly lower survival (0.57, 95% CI = 0.37–0.79). Among adults, females showed a slightly higher survival than males (0.87, 95% CI = 0.78–0.93; and 0.80, 95% CI = 0.73–0.86, respectively). These high survival figures predict high population persistence in this species and urge management policies. The analysis also stresses the usefulness of multievent models to estimate juvenile survival when age cannot be fully ascertained.     

Age estimates based on aspartic acid racemization for bowhead whales (Balaena mysticetus) harvested in 1998–2000 and the relationship between racemization rate and body temperature

Fifty‐two eyes were collected and analyzed to estimate ages of 42 bowhead whales using the aspartic acid racemization aging technique. Between‐eye and within‐eye variance components for the ratio of the D and L optical isomers (D/L ratio) were estimated via analysis of variance using multiple measurements from nine whales with both eyes sampled and analyzed. For whales with more than one (D/L)_act value, an inverse variance weighted average of the values was used as (D/L)_act for the whale. Racemization rate (k_Asp) and D/L ratio at birth (D/L)₀ were estimated using (D/L)_act from 27 bowhead whales with age estimates based on baleen or ovarian corpora data and two term fetuses. The estimates were k_Asp = 0.977 × 10^?3/yr and (D/L)₀ = 0.0250. The nonlinear least squares analysis that produced these estimates also estimated female age at sexual maturity as ASM = 25.86 yr. SE(age) was estimated via a bootstrap that took into account the SE of (D/L)_act and the variances and covariance of k_Asp and (D/L)₀. One male exceeded 100 yr of age; the oldest female was 88. A strong linear relationship between k_Asp and body temperature was estimated by combining bowhead data with independent data from studies of humans and fin whales. Using this relationship, we estimated k_Asp and ASM for North Atlantic minke whales.     

Growth and mortality of larval Myctophum affine (Myctophidae,Teleostei)

The growth and mortality rates of Myctophum affine larvae were analysed based on samples collected during the austral summer and winter of 2002 from south‐eastern Brazilian waters. The larvae ranged in size from 2·75 to 14·00 mm standard length (L_S). Daily increment counts from 82 sagittal otoliths showed that the age of M. affine ranged from 2 to 28 days. Three models were applied to estimate the growth rate: linear regression, exponential model and Laird–Gompertz model. The exponential model best fitted the data, and L₀ values from exponential and Laird–Gompertz models were close to the smallest larva reported in the literature (c. 2·5 mm L_S). The average growth rate (0·33 mm day^?1) was intermediate among lanternfishes. The mortality rate (12%) during the larval period was below average compared with other marine fish species but similar to some epipelagic fishes that occur in the area.     

Assessing the capacity for compensatory growth in growth‐hormone transgenic coho salmon Oncorhynchus kisutch

The effect of feed cycling (consisting of periods of starvation followed by periods of refeeding to satiation) on compensatory growth was evaluated in growth hormone transgenic and non‐transgenic wild‐type coho salmon Oncorhynchus kisutch. The specific growth rate (G_SR) of feed‐restricted non‐transgenic O. kisutch was not significantly different from the G_SR of fully‐fed non‐transgenic O. kisutch during two refeeding periods, whereas the G_SR of feed‐restricted transgenic O. kisutch was significantly higher in relation to the G_SR of fully‐fed transgenic O. kisutch during the second refeeding period, but not during the first, indicating that growth compensation mechanisms are different between non‐transgenic and growth‐hormone (GH)‐transgenic O. kisutch and may depend on life history (i.e. previous starvation). Despite the non‐significant growth rate compensation in non‐transgenic O. kisutch, these fish showed a level of body mass catch‐up growth not displayed by transgenic O. kisutch.     

Climate‐driven vital rates do not always mean climate‐driven population

Current climatic changes have increased the need to forecast population responses to climate variability. A common approach to address this question is through models that project current population state using the functional relationship between demographic rates and climatic variables. We argue that this approach can lead to erroneous conclusions when interpopulation dispersal is not considered. We found that immigration can release the population from climate‐driven trajectories even when local vital rates are climate dependent. We illustrated this using individual‐based data on a trans‐equatorial migratory seabird, the Scopoli's shearwater Calonectris diomedea, in which the variation of vital rates has been associated with large‐scale climatic indices. We compared the population annual growth rate λ_i, estimated using local climate‐driven parameters with ρ_i, a population growth rate directly estimated from individual information and that accounts for immigration. While λ_i varied as a function of climatic variables, reflecting the climate‐dependent parameters, ρ_i did not, indicating that dispersal decouples the relationship between population growth and climate variables from that between climatic variables and vital rates. Our results suggest caution when assessing demographic effects of climatic variability especially in open populations for very mobile organisms such as fish, marine mammals, bats, or birds. When a population model cannot be validated or it is not detailed enough, ignoring immigration might lead to misleading climate‐driven projections.     

Age‐specific mortality analysis of the dry forest kissing bug,Rhodnius neglectus

Age‐specific mortality patterns can be very different across insects with different life histories. Some holometabolous insects (like mosquitoes, fruit flies) show a pattern where mortality rate decelerates at older ages, whereas other holometabolous insects (bruchid beetles) and hemimetabolous insects (cotton stainers, milkweed bugs, and kissing bugs) show an age‐specific mortality pattern that increases through all ages. Kissing bugs are strictly hematophagous and are vectors of Trypanosoma cruzi Chagas, the etiologic agent of Chagas disease. Here, we tested whether cohort data from the dry forest kissing bug, Rhodnius neglectus Lent (Hemiptera: Reduviidae), supports an increase of mortality rate that decelerates with age. We analyzed the age‐specific mortality pattern of a cohort of 250 individuals of R. neglectus. We used a suite of seven models with different degrees of complexity, to model age‐dependent forms of change in mortality rate increase in R. neglectus in the laboratory. We used the Akaike model selection criterion to choose between models that consider absence or presence of mortality deceleration. Five of the seven models (logistic, Gavrilovs, Gompertz, DeMoivre, and exponential) showed a statistically significant fit to the mortality rate. Weak late‐age mortality deceleration in R. neglectus was supported by the best fit (logistic model), and this result is consistent with predictions of the disposable soma theory of senescence.     

Daily growth patterns and age‐at‐recruitment of the anchoveta Engraulis ringens as indicated by a multi‐annual analysis of otolith microstructure across developmental stages

The anchoveta (Engraulis ringens ) plays a key role in the ecology of the Humboldt Current System and is of major economic importance; however, many aspects of its early life history are still poorly understood. In this study, an analysis of daily age and length patterns was carried out using the sagittal otoliths from wild larvae (0–0.2 cm standard length, L _S), pre‐recruits (3–6 cm total length, L _T), recruits (7–12 cm L _T) and young adults (12–15 cm L _T). Additionally, variability in growth and age at recruitment (A _R) were evaluated for recruits caught in northern Chile in 1973, 1982, 2009, 2010, 2012, 2013, 2014 and 2015. The age–length relationship showed four allometric patterns that were well described by Laird‐Gompertz models. The absolute growth rates at the inflexion point (G _AR) were 0.56, 0.75, 1.22 and 1.16 mm d^?1 for larvae, pre‐recruits, recruits and young adults, respectively. At the interannual scale, G _AR values were always >1 mm d^?1 (mean ± S.D . 1.37 ± 0.21 mm d^?1; range 1.12–1.64 mm d^?1), irrespective of the season of hatching (i.e. winter v. spring); additionally, in most cases, G _AR values were reached before the second month of life (mean ± S.D . 50.47 ± 9.73 days) at c. 4 cm L _T (mean ± S.D . 4.22 ± 0.29 cm). Mean A _R was < 150 days (112 ± 29 days; range 75–149 days); in contrast, estimates of A _R were higher and growth rates were lower in 1973, 1983 and 2000. These results demonstrate very fast growth and early A _R of anchoveta in northern Chile, suggesting most fish are removed by the fisheries at very early ages. An evaluation of the implications of these results on stock assessment and management of this species is highly recommended.     

Daily age determination and growth rates of freshwater fish throughout a regulated lotic system of the Murray‐Darling Basin Australia

To facilitate future research in freshwater fish recruitment response to environmental flow delivery, size‐at‐age and growth models are presented for eight fish species occurring in south‐eastern Australia; three small‐bodied species and the juvenile 0+ age classes of five large‐bodied species. Otolith increments were used to estimate the daily age of golden perch Macquaria ambigua, bony bream Nematalosa erebi, common carp Cyprinus carpio; Murray cod Maccullochella peelii, freshwater eel‐tailed catfish Tandanus tandanus, Australian smelt Retropinna semoni, un‐specked hardyhead Craterocephalus stercusmuscarum fulvus and Murray–Darling rainbowfish Melanotaenia fluviatilis. Linear growth models provided the best fit for length‐at‐age data of juvenile 0+ age large‐bodied species; whereas von Bertalanffy growth functions provided the best fit to length‐at‐age data of small‐bodied species. The results provide novel baseline data for future research in this area.     

Extreme longevity in freshwater mussels revisited: sources of bias in age estimates derived from mark–recapture experiments

1. There may be bias associated with mark–recapture experiments used to estimate age and growth of freshwater mussels. Using subsets of a mark–recapture dataset for Quadrula pustulosa, I examined how age and growth parameter estimates are affected by (i) the range and skew of the data and (ii) growth reduction due to handling. I compared predictions from von Bertalanffy growth models based on mark–recapture data with direct observation of mussel age and growth inferred from validated shell rings. 2. Growth models based on a dataset that included observations from a wide range of length classes (spanning ≥ the upper 50% of the population length range) produced only slightly biased age estimates for small and medium‐sized individuals (overestimated by 1–2 years relative to estimates from validated shell rings) but estimates became increasingly biased for larger individuals. Growth models using data that included only observations of larger animals (< the upper 50% of length range) overestimated age for all length classes, and estimated maximum age was two to six times greater than the maximum age observed in the population (47 years). Similarly, growth models using a left‐skewed dataset overestimated age. 3. Reductions of growth due to repeated handling also resulted in overestimates of age. The estimated age of mussels that were handled in two consecutive years was as much as twice that of mussels that were handled only once over the same period. Assuming a constant reduction in the annual rate of growth, handling an individual for five consecutive years could result in an estimated age that is five times too high. 4. These findings show that mark–recapture methods have serious limitations for estimating mussel age and growth. A previous paper (Freshwater Biology, 46, 2001, 1349) presented longevity estimates for three mussel species that were an order of magnitude higher than estimates inferred from shell rings. Because those estimates of extreme longevity were based on mark–recapture methods and subject to multiple, additive sources of bias, they cannot be considered accurate representations of life span and cannot be used to conclude that traditional methods of bivalve ageing by interpretation of shell rings are flawed.     

Application of a novel method for age estimation of a baleen whale and a porpoise

Eyeballs from 121 fin whales (Balaenoptera physalus) and 83 harbor porpoises (Phocoena phocoena) were used for age estimation using the aspartic acid racemization (AAR) technique. The racemization rate (k_Asp) for fin whales was established from 15 fetuses (age 0) and 15 adult whales where age was estimated by reading growth layer groups (GLGs) in the earplugs. The (k_Asp) for harbor porpoises was derived from 15 porpoises (two calves and 13 > 1 yr old) age‐estimated by counting GLGs in the teeth and two calves classified to age based on length. The (k_Asp) values were estimated by regression of GLGs against D/L ratios. For the fin whales an (k_Asp) of 1.15 × 10^?3/yr (SE ± 0.00005) and a D/L ratio at birth [(D/L)₀] of 0.028 (SE ± 0.0012) were estimated, which is in agreement with rates for other mysticeti. For the harbor porpoises a (k_Asp) of 3.10 × 10^?3/yr (SE ± 0.0004) and a (D/L)₀ value of 0.023 (SE ± 0.0018) were estimated, which is considerably higher than found for other cetaceans. Correlation between chosen age estimates from AAR and GLG counts indicated that AAR might be an alternative method for estimating age in marine mammals.     

Age,growth, maturity and extinction risk of an exploited and endangered skate,Atlantoraja castelnaui,from off Uruguay and northern Argentina

The spotback skate Atlantoraja castelnaui (Arhynchobatidae) is a large and threatened skate species subjected to fishing pressure, endemic to the Southwest Atlantic that occurs from Rio de Janeiro, Brazil, to San Jorge Gulf, Argentina. The age, growth, age at maturity and the maximum intrinsic rate of population increase r_max of A. castelnaui were studied using 152 specimens collected from off Uruguay and north Argentina (35°–42° S), between June 2013 and February 2020. Vertebrae from 143 individuals were used for ageing (females: n = 83, size range 404–1300 mm total length, TL; males: n = 60, size range 400–1270 mm TL). Maximum ages determined for females and males were 30 and 28 years, respectively. To fit growth models, non-linear and Bayesian estimation approaches were considered. For the first approach, a set of four candidate growth (size-at-age) models were fitted: three-parameter von Bertalanffy, two-parameter von Bertalanffy with fixed L₀, Gompertz and Logistic. In the second approach, von Bertalanffy, Gompertz and Logistic were fitted. For non-linear estimation, model selection indicated that the entire set of candidate growth models were supported by the data. The von Bertalanffy was selected as the best model for Bayesian estimation. There were no differences in growth between sexes. For the sexes combined, the von Bertalanffy growth model by Bayesian method was considered the most adequate to describe the growth of A. castelnaui (growth mean parameters ± S.D. : L_∞ = 1210.29 ± 40.68 mm; k = 0.12 ± 0.01 years⁻¹; L₀ = 179.20 ± 11.62 mm). The age at maturity was estimated at 16.21 and 14.04 years for females and males, respectively. The maximum intrinsic rate of population increase r_max was estimated as 0.252 years⁻¹. Life-history traits and r_max provided in the present study suggest that this species has a relatively low productivity and may be vulnerable to an intense fishing pressure.     

The influence of self‐fertilization and grouping on fitness attributes in the freshwater snail Physa acuta: population and individual inbreeding depression

The genetic structure, selfing rate and inbreeding depression of the hermaphroditic freshwater snail Physa acuta were jointly analysed in a population near Montpellier, France. Allozymic markers revealed moderate gene diversity (0.138), and no heterozygote deficiency. The mean outcrossing rate, estimated by using progeny arrays, was 0.9, with substantial variation among families. This also suggests that the number of fathers among outcrossed offspring of a given mother is low. Inbreeding depression was estimated over more than one generation using 83 first‐laboratory‐generation (G₁) families. The main parameters measured were parental (G₁) fecundity, offspring (G₂) survival and fecundity. Size and growth were also monitored. Parental fecundity was analysed under several conditions (isolation, pair and quadruplet outcrossing). The self‐fertilization depression, including parental fecundity, offspring survival and fecundity, was about 0.9 at the population level. The genetic data obtained in the same population indicate a value of about 0.3 using Ritland’s (1990) technique, suggesting that the depression over the whole life‐cyle might be even higher than 0.9. Grouping affected neither fecundity nor self‐fertilization depression. Substantial variation in depression for survival was detected among individuals, from no survival in some selfed families to better survival than that of outbred families in others. The overall result (outbred population structure, high outcrossing rate and high self‐fertilization depression) is consistent with what is expected in large outcrossing populations in which inbreeding depression is maintained by mutation‐selection balance.     

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.