Observational evidence of risk-sensitive reproductive allocation in a long-lived mammal

Organisms should adopt a risk-sensitive reproductive allocation when summer reproductive allocation competes with survival in the coming winter. This trade off is shown through autumn female body mass, which acts as an insurance against unpredictable winter environmental conditions. We tested this hypothesis on female reindeer in a population that has experienced a time period of dramatic increase in abundance. Environmental conditions during winter were fairly stable (with the exception of 1 year). We conclude that increased population abundance (perhaps in interaction with winter environmental conditions) could have represented a worsening of winter environmental conditions as both autumn offspring and spring female body mass decreased during the course of the study. Moreover, we found that the cost of reproduction was related to environmental conditions as: (1) autumn body mass was larger for barren than for lactating females, and this difference was temporally highly variable; (2) lactating females produced smaller offspring than barren ones in the following year; and (3) reproductive output (offspring size) decreased over time. We also found evidence of quality effects as lactating females had a higher reproductive success in the following year. In sum, a worsening of winter conditions lead to: (1) decreased reproductive output; (2) lowered autumn body mass for lactating females; and (3) increased body mass for barren females. Since females reduce their reproductive allocation as winter conditions becomes more severe, we conclude that reindeer have adopted a risk-sensitive reproductive allocation.     

Density-dependence vs. density-independence - linking reproductive allocation to population abundance and vegetation greenness

1. Recent studies have shown that optimal reproductive allocation depends on both climatic conditions and population density. We tested this hypothesis using six years of demographic data from eight reindeer (Rangifer tarandus) populations coupled with data on population abundance and vegetation greenness [measured using the Enhanced Vegetation Index (EVI)]. 2. Female spring body mass positively affected summer body mass gain, and lactating females were unable to compensate for harsh winters as efficiently as barren ones. Female spring body mass was highly sensitive to changes in population abundance and vegetation greenness and less dependent on previous autumn body mass and reproductive status. Lactating females were larger than barren females in the spring. Moreover, female autumn body mass was positively related to female autumn body mass and reproductive success and was not very sensitive to changes in vegetation greenness and population abundance. 3. Offspring autumn body mass was positively related to both maternal spring and autumn body mass, and as predicted from theory, offspring were more sensitive to changes in vegetation greenness and population abundance than adult females. A lagged cost of reproduction was present as larger females who were barren, the previous year produced larger offspring than equally sized females that successfully reproduced the previous year. 4. Reproductive success was negatively related to female autumn body mass and positively related to female spring body mass. Moreover, females who successfully reproduced the previous year experienced the highest reproductive success. The fact that negative density-dependence was only present for females that had successfully reproduced the previous year further support the hypothesis that reproduction is costly. 5. This study shows that female reindeer buffer their reproductive allocation according to expected winter conditions and that their buffering abilities were limited by population abundance and a lagged cost of reproduction and enhanced by vegetation greenness.     

Voles on small islands: effects of food limitation and alien predation

Ecosystems of three trophic levels may be bottom-up (by food-plant availability) and/or top-down (by predators) limited. Top-down control might be of greater consequence when the predation impact comes from an alien predator. We conducted a replicated two-factor experiment with field voles (Microtus agrestis) during 2004-2005 on small islands of the outer archipelago of the Baltic Sea, south-west Finland, manipulating both predation impact by introduced American mink (Mustela vison) and winter food supply. In autumn 2004, we live-trapped voles on five islands from which mink had been consistently removed, and on four islands where mink were present, and provided half of these islands with 1.8 kg oats per vole. Body mass of female voles increased as a response to supplementary food, whereas both food supplementation and mink removal increased the body mass of male voles in subsequent spring. During winter, there was a positive effect of supplementary food, but in the subsequent summer, possible positive long-term impacts of food supplementation on field voles were not detected. Mink removal appeared not to affect density estimates of field voles during the winter and summer immediately after food addition. Trapping data from 2004 to 2005 and 2007 suggested, however, that in two out of three summers densities of voles were significantly higher in the absence than in the presence of mink. We conclude that vole populations on small islands in the archipelago of the Baltic Sea are mainly bottom-up limited during winter (outside the growing season of food plants), when food availability is low, and limited by mink predation during summer which slows population growth during the reproductive season of voles.     

Evolutionary responses to a changing climate: Implications for reindeer population viability

If we want to understand how climate change affects long‐lived organisms, we must know how individuals allocate resources between current reproduction and survival. This trade‐off is affected by expected environmental conditions, but the extent to which density independent (DI) and density dependent (DD) processes interact in shaping individual life histories is less clear. Female reindeer (or caribou: Rangifer tarandus) are a monotocous large herbivore with a circumpolar distribution. Individuals that experience unpredictable and potentially harsh winters typically adopt risk averse strategies where they allocate more resources to building own body reserves during summer and less to reproduction. Such a strategy implies that the females do not reproduce or that they produce fewer or smaller offspring. A risk averse strategy thus results in females with large autumn body reserves, which is known to increase their survival probabilities if the coming winter is harsh. In contrast, females experiencing predictable winters may adopt a more risk prone strategy in which they allocate more resources to reproduction as they do not need as many resources to buffer potentially adverse winter conditions. This study uses a seasonal state‐dependent model showing that DD and DI processes interact to affect the evolution of reproductive strategies and population dynamics for reindeer. The model was run across a wide range of different winter climatic scenarios: One set of simulations where the average and variability of the environment was manipulated and one set where the frequency of good and poor winters increased. Both reproductive allocation and population dynamics of reindeer were affected by a combination of DI and DD processes even though they were confounded (harsh climates resulted in lowered density). Individual strategies responded, in line with a risk sensitive reproductive allocation, to climatic conditions and in a similar fashion across the two climatic manipulations.     

Adaptive regulation of body reserves in reindeer, Rangifer tarandus: a feeding experiment

The costs and benefits of body reserves fluctuate according to predictable factors such as season and life-cycle stage. Theory suggests that individuals at any time should regulate their body reserves according to the current balance between costs and benefits. Most studies on adaptive body mass regulation have been done on small passerine birds. In large vertebrates the costs associated with body reserves are assumed to be small and the reserves of these species are therefore thought to be dictated by environmental limitations. In this study we present experimental evidence for adaptive body mass regulation in female semi-domesticated reindeer ( Rangifer t. tarandus ). The risk of starvation in this species is highest in late winter. During snow melt this risk is reduced and the females should direct their effort towards the protection of their new born calf. To test how these seasonal and life-cycle changes are related to body mass regulation, we conducted a crossed experiment with two treatments where females were fed ad libitum during winter and spring respectively. During winter, the females from the fed group gained on average 12% of their initial body weight while the females from natural pastures lost on average 6% of their initial body weight. This strong response to winter feeding had no effect on reproductive performance, and the previously fed females lost their excess of body reserves during feeding in spring. This suggests that body reserves during winter primarily is used as an insurance against stochastic periods of starvation and that the females regulate their body reserves down to a set point in spring when the risk is reduced. We found however a positive correlation between initial female body weight and reproductive performance suggesting a close relationship between body weight and intrinsic individual qualities.     

Offspring growth, survival and reproductive success in the bank vole: a litter size manipulation experiment

To estimate the optimality of brood size, it is essential to study the effects of brood size manipulation on offspring survival and reproductive success. Moreover, testing the generality of the hypothesis of reproductive costs requires experimental data from a diversity of organisms. Here I present data on the growth, survival and reproductive success of bank vole Clethrionomys glareolus individuals from manipulated litters. Furthermore, the survival of mothers whose litter size was manipulated was studied. At weaning, the mean weight of pups from enlarged litters was lower and from reduced litters higher compared to control litters. After winter, at the start of the breeding season, individuals from enlarged litters, especially males, were still lighter than individuals from the other two treatments. Litter enlargements did not increase the number of reproducing female offspring per mother, nor did the litter sizes of female offspring differ between treatments. There were no differences between treatments in winter survival of offspring after weaning, but among female offspring, weaning weight explained the survival probabilities over winter. A higher weight of females at winter determined the probability of starting to reproduce in spring. The survival of mothers did not seem to be influenced by litter manipulation performed the previous year. According to the results, mothers nursing enlarged or reduced litters do not gain any fitness benefits in terms of number of offspring surviving to breeding. The results are consistent with the majority of experiments conducted in birds, which have found costs of enlarged brood appearing as offspring trade-offs rather than parent trade-offs. Received: 14 December 1997 / Accepted: 1 March 1998     

Reproductive biology of Philodryas patagoniensis (Snakes: Dipsadidae) in south Brazil: Female reproductive cycle

In this study, we describe the female reproductive cycle of Philodryas patagoniensis in south Brazil, which was described through morpho‐anatomical and histological analyses. The peak of secondary vitellogenesis occurred during winter–spring (July–December), ovulation in spring (October–December), mating and fertilization in spring–summer (October–February), oviposition in spring–autumn (October–May) and births from late spring to autumn (December–July). The diameter of vitellogenic follicles/eggs was larger in winter–spring than in other seasons. The diameter of the shell glands was also larger in winter–spring. In spite of the clear reproductive peak, gonads only showed reduced activity in the autumn. Therefore, at the individual level, females have a discontinuous cyclical reproduction; in the populational level, the reproductive cycle is seasonal semisynchronous. We support the hypothesis that P. patagoniensis have the ability to produce multiple clutches with long‐term stored sperm. Sexual dimorphism in body size was evident, and females are significantly larger and heavier than males. Larger females were able to produce follicles and eggs in larger amount and size. The maternal body size was positively related to the reproductive effort and fecundity. To conclude, we deliberated about the proximal and distal causes that influence the reproductive traits and patterns of P. patagoniensis.     

Determinants of reproductive success in female Columbian ground squirrels

Summary We studied the reproductive success of female Columbian ground squirrels (Spermophilus columbianus) in southwestern Alberta for nine years. We defined reproductive success as the number of offspring surviving their first hibernation, classified as yearlings. The number of weaned juveniles explained one third of the variance in number of yearlings at emergence from their first hibernation the following spring, and much of the variance in individual reproductive success originated after weaning. Weight of adult females at emergence from hibernation was correlated with annual reproductive success. The mother's survival beyond weaning and the subsequent winter's snow accumulation had positive effects on annual reproductive success, whereas population density and summer temperature had negative effects. We found no effects on annual reproductive success of date of litter emergence, weight at emergence as a yearling, presence or absence of adult kin, distance from the natal site, location within the study area, winter temperature or summer precipitation. Age of first breeding did not affect lifetime reproductive success, which ranged from 0 to 19 yearlings produced over a lifetime. The greatest source of variation in lifetime reproductive success for females surviving to breeding age was offspring survival, followed by reproductive lifespan.     

Influences of weather on reproductive function in female Song sparrows, Melospiza melodia

Prolonged and severe periods of inclement weather can retard gonadal development in early spring or disrupt the breeding cycle in summer. Previous investigations on the endocrine responses of free-living avian species to storms have been restricted almost entirely to males. This communication presents the endocrine responses of free-living female Song sparrows, Melospiza melodia, during gonadal recrudescence after a severe winter, and during storms in early spring and summer. As in males, gonadal recrudescence was delayed by the severe winter weather, and this effect was exacerbated by an aseasonal snow storm in early spring. Unlike males, female Song sparrows did appear to be stressed by this snow storm, since body mass and fat deposit decreased, and plasma levels of corticosterone increased. A second storm in early summer did not, however, prove to be stressful to females, although males were apparently stressed by the same storm. At the time the early summer storm occurred, young had been fledged and were being fed mostly by the male. Females begin preparing for a second clutch of eggs and do not feed fledglings to the same extent as males. Thus it is possible that males are stressed by storms at this time, because they are feeding several young as well as themselves during a period of reduced availability of food, whereas females are feeding themselves only. These data suggest that, not only do the endocrine responses to inclement weather vary in relation to stage in the reproductive cycle when storms strike, but also that there are sex differences in those responses.     

Long-term fitness benefits of polyandry in a small mammal, the bank vole Clethrionomys glareolus

Polyandry, i.e. mating with multiple males within one reproductive event, is a common female mating strategy but its adaptive function is often unclear. We tested whether polyandrous females gain genetic benefits by comparing fitness traits of monandrous (mated twice with a single male) and polyandrous (mated twice with two different males) female bank voles Clethrionomys glareolus. We raised the offspring in the laboratory until adulthood and measured their body size, before releasing them to outdoor enclosures to overwinter. At the onset of the breeding season in the following spring, we found that offspring of polyandrous females performed significantly better at reproduction than those of monandrous females. This was mainly due to sons of polyandrous females producing significantly more offspring than those of monandrous females. No significant differences were found for offspring body mass or winter survival between the two treatments. Our results appear to provide evidence that bank vole females gain long-term benefits from polyandry.     

Reproductive success and failure: the role of winter body mass in reproductive allocation in Norwegian moose

A life history strategy that favours somatic growth over reproduction is well known for long-lived iteroparous species, especially in unpredictable environments. Risk-sensitive female reproductive allocation can be achieved by a reduced reproductive effort at conception, or the subsequent adjustment of investment during gestation or lactation in response to unexpected environmental conditions or resource availability. We investigated the relative importance of reduced investment at conception compared with later in the reproductive cycle (i.e. prenatal, perinatal or neonatal mortality) in explaining reproductive failure in two high-density moose (Alces alces) populations in southern Norway. We followed 65 multiparous, global positioning system (GPS)-collared females throughout the reproductive cycle and focused on the role of maternal nutrition during gestation in determining reproductive success using a quasi-experimental approach to manipulate winter forage availability. Pregnancy rates in early winter were normal (≥0.8) in all years while spring calving rates ranged from 0.4 to 0.83, with prenatal mortality accounting for most of the difference. Further losses over summer reduced autumn recruitment rates to 0.23–0.69, despite negligible predation. Over-winter mass loss explained variation in both spring calving and autumn recruitment success better than absolute body mass in early or late winter. Although pregnancy was related to body mass in early winter, overall reproductive success was unrelated to pre-winter body condition. We therefore concluded that reproductive success was limited by winter nutritional conditions. However, we could not determine whether the observed reproductive allocation adjustment was a bet-hedging strategy to maximise reproduction without compromising survival or whether females were simply unable to invest more resources in their offspring.     

四川荥经县赤腹松鼠体重及脏器湿重的性别与季节差异

以2015年1月至12月捕自四川荥经县的310只成体赤腹松鼠(Callosciurus erythraeus,雄鼠174只,雌鼠136只)为研究对象,分析了其体重及7种内脏器官湿重的性别和季节差异,以及妊娠对内脏器官湿重的影响。1)雌、雄鼠的体重无性别和季节差异。2)心湿重雌、雄鼠差异显著,春季雄性大于雌性,夏季相反;肝、脾、肺和肾的湿重均无性别差异。3)肝湿重夏、冬季高于春、秋季;脾湿重秋季高于冬季和春季;肺湿重春季最高,夏季最低;肾湿重冬、春季高于夏季;心湿重雄鼠秋季高于夏、冬季,雌鼠夏、秋季高于冬季;睾丸和子宫湿重都在春季最高,秋季最低。4)妊娠鼠肝、肺和肾湿重均高于未妊娠鼠。结果表明,随着季节更替赤腹松鼠的体重维持稳定,雌、雄鼠心湿重差异显著,且器官湿重表现出了一定的弹性,这可能与雌、雄鼠的繁殖状态及季节性环境的多样性变化有关。     

Ovarian cycle and egg production of the western swamp tortoise Pseudemydura umbrina (Testudines: Chelidae) in the wild and in captivity

The reproductive organs of logn-term captive females and of wild females of the western swamp tortoise, Pseudemydura umbrina , which were taken temporarily into captivity, were studied over several years by ultra-sound scanning. Pseudemydura umbrina , a critically-endangered species, is active during winter and spring when the ephemeral swamps it inhabits contain water and aestivates during summer and autumn (November to May/June) when the swamps are dry. The vitellogenic growth of ovarian follicles commences during aestivation in summer and continues during autumn and winter. The timing of the vitellogenic cycle is remarkably similar to that of many other Australian chelids and that of many other chelonians of temperate and subtropical regions, but the patterns of energy harvest, storage and allocation to ovarian follicles is different. Ovulation occurs between late September and early November and is preceded by a feeding bout and a sharp increase in female body mass. One clutch of 3–5 eggs (exceptionally of one or two) is laid in November/December. Sub-adult females show cycles of follicular growth, followed by atresia, for several years before ovulating and laying eggs. Females taken into captivity may miss the following vitelogenic cycle, but captivity does not generally affect vitellogenic cycles. Ovulation and egg production of captive animals is easily suppressed, however, under stress or sub-optimal food intake in spring. The sensitivity of ovulation to sub-optimal conditions and the subsequent reabsorption of the yolk material may enhance survival of the reproducing individual during long dry periods in an unpredictable environment.     

Assessing the role of body mass and sex on apparent adult survival in polygynous passerines: a case study of cetti's warblers in central Portugal

Adult survival, an important fitness component, is usually 1) lower in lighter individuals due to their reduced ability to survive winter conditions compared to heavier ones, especially in resident species at northern temperate latitudes and 2) lower in females compared with males due to higher reproductive costs incurred by females. In this paper, a capture–mark–recapture dataset of 649 cetti's warblers Cettia cetti ringed seasonally at two wetlands in central Portugal over an 11‐yr period (2000–2010) was modelled in a multi‐state framework to examine the influence of these individual covariates on apparent adult survival, while controlling for the presence of transient individuals in our study area. The probability of change in mass state (ψ_{Light→Heavy}, ψ_{Heavy→Light}) during the annual cycle was also estimated. Overall, birds survived better during spring–summer (breeding/moulting periods) compared with autumn–winter, but there was no effect of body mass on apparent adult survival probability. The modelling detected a significant interaction between sex and season, in which resident females survived better than resident males in spring–summer (?_RF= 0.857 ± 0.117 and ?_RM= 0.698 ± 0.181) while the opposite pattern was found in autumn–winter (?_RM= 0.440 ± 0.086 and ?_RF= 0.339 ± 0.084). In addition, cetti's warblers had a tendency to lose mass in spring–summer (ψ_{Heavy → Light}= 0.560 ± 0.063) and to regain mass in autumn–winter (ψ_{Light→Heavy}= 0.701 ± 0.069). This pattern of body mass change during the annual cycle may reflect energetic costs to reproduction and moulting, and/or a response to increased starvation risk during winter. High body mass, however, did not increase adult survival in this population presumably due to the relatively mild winter weather prevailing in central Portugal. Survival estimates are more likely to be explained by important ecological and behavioural differences between the two sexes in polygynous passerines. Our results highlight that studies aiming to identify the main factors shaping survival and individual fitness in polygynous species should be conducted during different phases of their annual cycle.     

Seasonal variation in haematological parameters in male and female Tinca tinca

This study was designed to investigate any seasonal (spring, summer, autumn and winter) changes in haematological parameters in the blood of Tinca tinca measuring the number of red blood cells (RBC), haematocrit, white blood cells, and total plasma proteins.The results show significant changes in RBC and haematocrit in males comparing spring and summer with autumn and winter, whereas in females the RBC remained constant for all 4 seasons but the haematocrit decreased in autumn and winter compared to spring and summer. The white blood cells of male and female animals were significantly lower in spring and winter compared to summer and autumn. In male fish total protein contents significantly decreased in autumn and winter compared to spring and summer, whereas in females protein output significantly decreased in winter compared to the other seasons. The results indicate marked seasonal variation in the blood of male and female Tinca tinca. This variation may play a important protective role for the survival of the animals.     

Determinants of reproductive success in voles: space use in relation to food and litter size manipulation

Spacing behaviour of female mammals is suggested to depend on the distribution and abundance of food. In addition, food limitation has been found to constrain the reproductive success of females. However, whether females maximize their reproductive success by adjusting space use in relation to current food availability and reproductive effort (e.g. litter size) has not been experimentally studied. We examined these questions by manipulating simultaneously food resources (control vs. food supplementation) and litter sizes (control vs. plus two pups) of territorial female bank voles (Clethrionomys glareolus) in large outdoor enclosures. Females with supplementary food had smaller home ranges (foraging area) and home range overlaps than control females, whereas litter size manipulation had no effect on space use. In contrast, the size of territory (exclusive area) was not affected by food supplementation or litter size manipulation. As we have previously shown elsewhere, extra food increases the reproductive success of bank vole females in terms of size and proportion of weaned offspring. According to the present data, greater overlap of female home ranges had a negative effect on reproductive success of females, particularly on survival of offspring. We conclude that higher food availability increases the reproductive success of bank vole females, and this effect may be mediated through lower vulnerability of offspring to direct killing and/or detrimental effects from other females in the population. Moreover, it seems that when density of conspecifics is controlled for, home range sizes of females, but not territoriality, is related to food resources in Clethrionomys voles.     

Chicken or egg? Outcomes of experimental manipulations of maternally transmitted hormones depend on administration method – a meta‐analysis

Steroid hormones are important mediators of prenatal maternal effects in animals. Despite a growing number of studies involving experimental manipulation of these hormones, little is known about the impact of methodological differences among experiments on the final results expressed as offspring traits. Using a meta‐analytical approach and a representative sample of experimental studies performed on birds, we tested the effect of two types of direct hormonal manipulations: manipulation of females (either by implantation of hormone pellets or injection of hormonal solutions) and manipulation of eggs by injection. In both types of manipulation we looked at the effects of two groups of hormones: corticosterone and androgens in the form of testosterone and androstenedione. We found that the average effect on offspring traits differed between the manipulation types, with a well‐supported positive effect of egg manipulation and lack of a significant effect of maternal manipulation. The observed average positive effect for egg manipulation was driven mainly by androgen manipulations, while corticosterone manipulations exerted no overall effect, regardless of manipulation type. Detailed analyses revealed effects of varying size and direction depending on the specific offspring traits; e.g., egg manipulation positively affected physiology and behaviour (androgens), and negatively affected future reproduction (corticosterone). Effect size was negatively related to the dose of androgen injected into the eggs, but unrelated to timing of manipulation, offspring developmental stage at the time of measuring their traits, solvent type, the site of egg injection and maternal hormone delivery method. Despite the generally acknowledged importance of maternal hormones for offspring development in birds, the overall effect of their experimental elevation is rather weak, significantly heterogeneous and dependent on the hormone and type of manipulation. We conclude by providing general recommendations as to how hormonal manipulations should be performed in order to standardize their impact and the results achieved. We also emphasize the need for research on free‐living birds with a focus on fitness‐related and other long‐term effects of maternal hormones.     

Optimal allocation of reproductive effort: manipulation of offspring number and size in the bank vole

The number of offspring attaining reproductive age is an important measure of an individual's fitness. However, reproductive success is generally constrained by a trade-off between offspring number and quality. We conducted a factorial experiment in order to study the effects of an artificial enlargement of offspring number and size on the reproductive success of female bank voles (Clethrionomys glareolus). We also studied the effects of the manipulations on growth, survival and reproductive success of the offspring. Potentially confounding effects of varying maternal quality were avoided by cross-fostering. Our results showed that the number of offspring alive in the next breeding season was higher in offspring number manipulation groups, despite their smaller body size at weaning. Offspring size manipulation had no effect on offspring growth or survival. Further, the first litter size of female offspring did not differ between treatments. In conclusion, females may be able to increase the number of offspring reaching reproductive age by producing larger litters, whereas increasing offspring size benefits neither the mother nor the offspring.     

Risk‐sensitive reproductive allocation: fitness consequences of body mass losses in two contrasting environments

For long‐lived organisms, the fitness value of survival is greater than that of current reproduction. Asymmetric fitness rewards suggest that organisms inhabiting unpredictable environments should adopt a risk‐sensitive life history, predicting that it is adaptive to allocate resources to increase their own body reserves at the expense of reproduction. We tested this using data from reindeer populations inhabiting contrasting environments and using winter body mass development as a proxy for the combined effect of winter severity and density dependence. Individuals in good and harsh environments responded similarly: Females who lost large amounts of winter body mass gained more body mass the coming summer compared with females losing less mass during winter. Additionally, females experienced a cost of reproduction: On average, barren females gained more body mass than lactating females. Winter body mass development positively affected both the females' reproductive success and offspring body mass. Finally, we discuss the relevance of our findings with respect to scenarios for future climate change.     

黄海中南部细纹狮子鱼的生物学特征及资源分布的季节变化

根据2009年7—8月、10月和2010年1月、5月黄海中南部渔业生物底拖网调查数据,对该海域细纹狮子鱼的生物学特征及其分布的季节变化作了分析。结果表明,细纹狮子鱼平均体长和平均体重从春季(4.7 cm、3.3 g)到冬季(34.2 cm、764.9 g)呈显著增加,并且雄性个体平均体长显著大于雌性个体(P<0.05,春季除外)。性比(♀∶♂)随体长组和季节变化,体长越大趋向于雄性,反之趋向于雌性;夏季雄鱼居多(0.70∶1,P<0.05),秋季则为雌鱼居多(1.35∶1,P<0.05),而冬季(产卵群体)和春季性比接近于1∶1。细纹狮子鱼各季节摄食等级均在2.5以上,冬季雄性个体摄食等级显著大于雌性个体(P<0.05),但雄性个体肥满度为全年最低(1.52)。细纹狮子鱼相对资源量和贡献率从春季(0.17 kg/h,1.54%)到秋季(15.36 kg/h,33.05%)呈上升状态,而冬季(2.37 kg/h,5.60%)有所下降。相比2000年,夏秋季相对渔获量和贡献率提高明显。全年集中分布于7.8—13.6℃,3.20%—3.38%的水域,平均体重和水深有显著的相关性(秋季除外)。另外,根据性成熟个体分布区和稚幼鱼分布的相关历史资料分析发现,除海州湾外,黄海中部深水区可能是细纹狮子鱼的产卵场。