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1.
Abstract –  Previous studies have offered suggestive but sometimes conflicting glimpses at the range and patterns of seasonal and interannual variation in female darter life-history traits. The present study examined clutch-size and egg-size variation from a single Mississippi population of brighteye darters (Etheostoma lynceum ), collected at regular intervals over four sequential spawning seasons. Both life-history traits were significantly correlated with body size, and they both showed significant variation within and among breeding seasons. The overall intraseasonal trends in these traits involved an increase in clutch size (CS) and a decrease in egg size from early to late periods of the spawning season. Clutch size and egg size showed a weak but significant negative correlation, which was indicative of a trade-off between the two clutch parameters. Seasonal changes in temperature appear to be related to differing patterns of seasonal variation in egg size reported in the literature for darters. Inverse seasonal shifts in egg size and CS in the brighteye darter may represent adaptive phenotypic plasticity that allows females to produce larger, competitively superior offspring early in the reproductive season when there is low supply of food for them (parental investment hypothesis) or to produce larger eggs early in the reproductive season to ensure that each egg is adequately provisioned in the face of uncertainty (bet-hedging hypothesis) if the food available for the young is unpredictable early in the season. Consistent with theoretical predictions, egg size showed less phenotypic variability than CS.  相似文献   

2.
Abstract – Flagfin shiners, Pteronotropis signipinnis , were collected from Sweetwater Creek, a second-order blackwater stream in southeastern Mississippi, during each month of 1996. Analysis of length frequency histograms indicated a life span of 1 to 2 years. Sex ratio was not different from a 1:1 ratio. Adult males were larger and more heavily pigmented near the abdomen than females. Females were reproductive from April to mid-August. All females attained sexual maturity by 27 mm SL and produced multiple clutches of ova. Clutch size varied from 12 to 101 ova and was correlated with SL. Mean mature oocyte diameter was 0.88 mm (range 0.76–0.96). Despite the relationship between clutch size and body size, P. signipinnis may be selected to invest in early reproduction rather than growth. This idea is supported by the small size at maturity in this species and is consistent with an opportunistic life-history strategy. Note  相似文献   

3.
Abstract – The life history traits of breeding size, clutch size, egg size and relative clutch mass were examined for evidence of plasticity within a set of six annual samples of threespine stickleback, Gasterosteus aculeatus L., females from south-central Alaska, USA. Three samples (from 1992, 1996 and 1999) were of stickleback native to, and living within, a stream environment, while three (from 1995, 1996 and 1999) represented fish living within a pond environment recently colonized by the stream stickleback. Significant differences between stream and pond fish were found for all four traits. For most traits, pond-living females showed greater variation both across and within years than did stream-living females. Although extremely rapid evolution within the pond, or genetic drift caused by low founding population size, could not be completely ruled out, trait changes across years in both environments were interpreted as representing adaptive plasticity.  相似文献   

4.
Abstract –  Many populations of vertebrates display alternative reproductive strategies involving delays in maturation processes and migrations to more productive habitats. Notably for females, migratory patterns and diet could influence reproductive traits such as ova size and number. To test this hypothesis, we targeted anadromous and freshwater-resident female brown trout of various sizes during their return to spawn in tributaries, and carried out stable isotope analyses (δ15N and δ13C) on ova to identify their feeding areas and diet. The study was performed in the Oir River (France), a small coastal system where trout migrations to sea and within the river basin have been monitored for the last 20 years. General trends were observed in reproductive traits, such as the positive correlation between female fork length, fecundity and ova size. Fecundity was size-dependent whatever the migratory origin of females, but major divergences were seen for ova size and isotopic ratios. Freshwater residents displayed a constant increase in ova size and a 15N-enrichment in ova, suggesting an investment in larger ova and a shift to piscivory as the fish become larger and older. Conversely, anadromous females had smaller ova compared with freshwater-resident females of similar body size and achieved higher fecundity as they grew bigger. Our results suggest the existence of a continuum of reproductive traits for freshwater-resident females whereas anadromous females clearly show a break with this continuum. This major dissimilarity could be explained by the difference in growing environments in terms of food availability and quality.  相似文献   

5.
Abstract – We examined the reproductive characteristics of 38 female longnose dace ( Rhinichthys cataractae ) from one of the southernmost populations of this species during two sampling periods in 1999 (ES=March 1999, LS=June 1999). Our data indicated that ES fish had not spawned, whereas LS fish had begun spawning. The smallest mature female captured was 56 mm SL (age 1+). Mean potential fecundity differed significantly between ES (mean±1 SD=1832±572 oocytes) and LS (mean±1 SD=775±415 oocytes) specimens. Potential fecundity was positively correlated with both standard length and somatic mass for both ES and LS specimens. Oocyte diameter frequency histograms indicated that ES specimens possessed two modes of oocytes, whereas LS fish contained two or three modes. Female longnose dace appeared to spawn more than once during a reproductive season. Oocyte number varied substantially both among individuals within periods and between periods. The number of Mode II oocytes in ES fish was positively correlated with both length and somatic mass. Female longnose dace appeared potentially capable of spawning 6+ clutches per year. GSI values for longnose dace ranged from a high of 21.4% (LS specimen) to 2.4% (ES specimen). Regression analysis demonstrated that there was no evidence of differential reproductive effort between longnose dace of different size in this population.  相似文献   

6.
Abstract –  Pacific salmon develop many sexually dimorphic features at maturity, and the extent of development varies among populations. In this study, we compared a suite of traits including body length, body depth, jaw length, tooth size and skin mass in male and female sockeye salmon breeding in beach and creek habitats. Both tooth size and skin mass varied positively with body length. Within each of the breeding habitats, males had longer teeth than females, and within each sex, beach spawners had longer teeth than creek spawners. Males also had heavier skin than females in each habitat but, unlike the case with tooth size, creek spawners showed a much stronger relationship between skin mass and body length than did beach spawners. Tooth length was positively related to jaw length and skin mass among individuals within a given sex and habitat. Taken together, these results suggested that variation in tooth size parallels variation in other sexually dimorphic traits. Males and beach spawners tend to exhibit large trait values relative to females and creek spawners, and 'well-endowed' individuals displayed high values of all traits rather than a trade-off as might occur if investment in one trait compromised investment in others. However, the finding that creek fish tended to have thicker skin for a given body length than did beach fish suggested that factors other than merely defense against conspecifics during battle, such as abrasion and desiccation resistance in small streams, may influence the evolution of skin mass in mature sockeye salmon.  相似文献   

7.
Abstract– I collected bluntface shiners, Cyprinella camura , once or twice monthly from February to November 1991 in Morganfork Creek, southwestern Mississippi. Examinations of mean largest oocyte diameter (LOD), female mean relative gonadal index (RGI), ovarian developmental condition, and male secondary sexual characteristics indicated that C. camura spawned from late March through mid-August. There were significant positive correlations between mean LOD and mean daylength, mean maximum temperature, and mean minimum temperature (environmental variable means were calculated for the 28 day period prior to each sampling date). Mean day length and mean RGI were significantly positively correlated, but there was no significant relationship between mean maximum and minimum temperatures and mean RGI. Clutch size, RGI, and mean mature oocyte diameter (MMOD) of mature females were significantly correlated with length (standard length). Mean length, clutch size, and RGI of mature females in individual collections decreased significantly over the reproductive season. The corresponding decrease in mean MMOD was not significant.  相似文献   

8.
I examined the age, growth, maturity, mortality, and body condition of walleye pollock, Theragra chalcogramma, in the northeastern Japan Sea (northern Japan Sea population) and evaluated their resilience to exploitation. Walleye pollock were collected in pre-spawning (October 1991-1995) and post-spawning (April 1990-1996) seasons. Estimated ages ranged from 3 to 18 years for both sexes. A von Bertalanffy growth model showed that females had longer asymptotic fork length (460 mm) than males (425 mm). Fifty percent of females and males were mature at 348 mm (4.6 years) and 322 mm (3.9 years), respectively. The instantaneous natural mortality rate was estimated to be 0.22. These life-history traits in the northern Japan Sea population were compared to those in the Bering Sea, the Gulf of Alaska, and the Japan Pacific populations. As a result, female walleye pollock in this population matured at small body sizes, grew rapidly toward small maximum sizes, and had short reproductive lifespans with low size-specific fecundity and poor body condition. Low prey availability and habitat temperatures are considered as a possible mechanism for the small maximum sizes in this population. The potential rate of population increase of both the northern Japan Sea population and other pollock populations tended to be lower than other exploited populations of non-viviparous marine fishes, suggesting potentially lower resilience to exploitation in this population and walleye pollock populations in general.  相似文献   

9.
The effect of selection for greater growth rate in the GIFT strain on traits related to female reproduction (weight at spawning, number of eggs, number of fry, total weight of fry and number of dead fry) was studied. Available records comprised 10 generations of data from a total of 935 breeding females with known pedigree. Female body weight at spawning was 255 g, whereas the averages for number of eggs, number of live fry at hatching, number of dead fry and total fry weight per spawning were 1444, 908, 64.90, and 7.24 g respectively. Heritabilities for reproductive traits were low to moderate (0.20 for number of eggs, 0.16 for number of hatched fry and 0.11 for fry weight per female at spawning). The genetic correlations between female body weight at spawning and reproductive traits were very low to low (0.01 to 0.31) and not significantly different from zero. The genetic correlations among reproductive traits (i.e. number of eggs, number of hatched fry and fry weight) were high (0.75 to 0.92). Phenotypic correlations were consistent with the genetic correlations, ranging from 0.56 to 0.85. Correlated responses in reproductive traits measured as differences in least squares means between Selection and Control lines were positive and significant (except for the number of dead fry) when age of females at spawning was fitted as a covariate. However, there were no significant differences in all studied traits when body weight of the female at spawning was fitted as a covariate within lines. This indicates that the greater reproductive rate was due to the greater size of females in the Selection line, but the efficiency of reproduction per unit weight of female did not change as a consequence of selection for growth.  相似文献   

10.
Salmonid females invest heavily in reproduction, through gamete production, habitat selection and maternal care. Habitat selection and maternal care are expected to provide shelter for eggs against scouring and predators. However, females also tend to produce variable egg sizes, and this trait may interact with habitat quality to influence the survival of offspring. In this study, we aimed at evaluating the role of female habitat selection on egg survival conditional on individual egg size and female body size. We monitored female reproductive activity in two natural rivers for 3 years, in order to relate nest characteristics to female body size. Bigger females dug deeper nests at lower shear stress force. Right after the end of nest construction, we sampled a part of the eggs laid by each female, measured them individually, and placed them back using capsules within their original position in the nest. At time of hatching, the capsules within the nest were collected and individual egg mortality was assessed. Our results indicate that scouring was the main driver for mortality (75%) and that nest burial depth and shear stress force above the nest both influenced scouring. However, subsequent survival was influenced by neither nest characteristics, individual egg size, nor the interaction between both. It is therefore expected that traits or tactics that reduce nest scouring probability should be under strong selection.  相似文献   

11.
Life‐history theory predicts that the optimal strategy in the trade‐off between egg size and number varies in relation to resource availability and environmental disturbance. We assessed interspecific differences in egg size, fecundity and other life‐history traits in a species complex of stream‐resident galaxiid fish, which are distributed across a range of contrasting habitat types on the South Island, New Zealand. Oocyte size, fecundity and reproductive effort were measured from gravid females collected immediately before spawning. Proxy measures of stream productivity, flow variability and predation pressure were extracted from modelled data sets. A suite of different egg sizes were identified across species within the Galaxias vulgaris complex, with mean oocyte volume differing by up to 133% between species. The species with the smallest eggs showed mean size‐relative fecundities 246% higher than the species with the largest eggs. A significant negative relationship was found between species’ mean egg size and size‐relative fecundity, suggesting a trade‐off between these traits. Species with larger eggs had larger maternal body size, lower reproductive effort and delayed maturity compared to ‘small‐egg’ species. Consistent with the predictions of life‐history theory, species with larger eggs, lower size‐relative fecundity, lower reproductive effort and delayed maturity were associated with low productivity, stable streams, whereas species exhibiting the opposite set of traits occurred in relatively productive but disturbed systems.  相似文献   

12.
The reproductive performance of three domesticated rainbow trout broodstocks spawning at 2 years of age was analysed using data collected over a period of 5 years. Data were collected for post-spawning body weight, volume of eggs spawned, egg size, egg number and fertility to the eyed egg stage. There were significant differences among the stocks attributable to both genetic and environmental causes. In addition, there were marked differences between year-classes, isolated from each other due to 2-year spawning. The differences appeared to be genetic in origin and demonstrated the effect of sampling the original parents.Heritabilities estimated from full-sib comparisons indicated male weight was more influenced by environmental stress at spawning than was female weight. Heritability estimates for egg volume, egg size and egg number ranged from 0.05 to 0.76 for individual stocks, but when averaged for the three stocks the range was from 0.32 to 0.52. Egg size was found to have the lowest heritability of the three traits. The heritability of fertility was found to be low and was the lowest for the stock with the poorest fertility.Genetic and phenotype correlations among the traits were also estimated. The relationship between body weight and egg volume and size were both positive as was that between egg volume and egg size. It was determined that egg volume was the principal determinant of egg number and that the relationship of number to size could be negative. The latter evidence was obtained by artificially adjusting the egg production traits to a constant female body size. The result suggested that females that produce larger numbers of eggs are likely to produce smaller eggs unless the change is associated with a marked increase in body weight. It is recommended that selection for egg size be included in all selection programs and that egg number be ignored in any selection program designed to increase body size.  相似文献   

13.
Abstract – Body length, age, egg size, embryo salinity tolerance and length at hatching of the freshwater (salinity <0.1 ppt, Lake Peipsi) and brackish-water (salinity 2–6 ppt, Pärnu and Matsalu Bay) ruffe, Gymnocephalus cernuus (L.), were examined to reveal their reproductive success in moderate salinity. Eggs of females originating from brackish water were significantly larger than eggs of freshwater females. No correlation between egg size and female size and age was found in brackish-water populations. In the freshwater population there was a small negative correlation between egg size and female size, but no correlation with female age. Fertilisation by sperm of males of different origin (brackish water or freshwater) produced no significant differences at any critical developmental stage (fertilisation, gastrulation, hatching) in the development of eggs from brackish-water or freshwater females at 3.3, 5.5, 7.7 and 9.9 ppt salinity. Survival rates in different salinity depended only on female origin; embryonic salinity tolerance was higher in ruffe inhabiting brackish water. Obviously, embryo salinity tolerance in ruffe is determined by egg qualities.  相似文献   

14.
The reproductive biology of female Pasiphaea japonica, including the minimum size of females carrying embryos, spawning and hatching seasons, and brood size, was examined in Toyama Bay, central Japan, during 2004 through 2007. Sampling was conducted onboard a commercial seiner and a fisheries research vessel. The minimum size of ovigerous females was 47.7 mm body length. The percent occurrence of ovigerous females increased with body size, reaching 50% at 57.9 mm body length. Ovigerous females occurred all year round with a seasonal change in percent occurrence, ranging between 41.5 and 94.3% of the total observed females. Consequently, reproduction in females seems to occur throughout the year in Toyama Bay, with seasonal differences in reproductive intensity. Spawning intensity was high during April–July and October–January based on the occurrence of the early developmental stage of embryos, while hatching intensity was high in October–May based on the occurrence of embryos just before hatching. Brood sizes were similar at the same size of body length regardless of embryo stage, except just after spawning.  相似文献   

15.
This study investigates the effect of a predation gradient on the female life history traits of the poeciliid live‐bearing fish Phalloceros harpagos from a tropical stream in Brazil. Females’ length at maturity, somatic dry mass, reproductive allotment and fecundity varied significantly among predation sites. Phalloceros harpagos from the high‐predation site showed smaller size at maturity and somatic dry mass, greater reproductive allotment and higher fecundity than the nonpredation site. In all sites, we observed superfetation: pregnant females with two broods at different developmental stages. The presence of superfetation was not observed before in other congeneric species, and it may represent an additional independent evolutionary origin of superfetation in the fish family Poeciliidae. Matrotrophy, the postfertilisation maternal provisioning of nutrients to developing embryos throughout gestation, was observed in all three sites, with values of the matrotrophy index above two. The population under high predation pressure showed the highest degree of matrotrophy (embryos quadruplicate their dry mass during development) and the greatest percentage of females with superfetation (44.4%). Some life history traits responded more strongly to predators’ presence and others to predator density. These results suggest that different predation regimes shape female life history traits, increasing fecundity in high‐predation sites. The results also suggest a link between the cost of reproduction and the evolution of matrotrophy and superfetation, potentially to reduce the risk of predation without reducing fecundity.  相似文献   

16.
Abstract – Life history traits can vary among populations of the same fish species in response to selective pressures exerted by the local environment. Here we used inter-population comparisons to investigate the effects of parasitism and variability in water temperature on life history traits in a New Zealand freshwater fish, the upland bully. Although age and size at maturity varied among populations, they were not significantly related to either temperature regime or average parasite load. Trade-offs between egg size and clutch size were only apparent in one of the seven populations when populations were analyzed separately but became clear when all data were pooled. However, neither average population clutch size or egg size was related to the population's mean parasite load or the local temperature regime. Although the latter two parameters may influence other life history variables, such as the number of clutches produced per season and the partitioning of eggs among clutches, there was no evidence that they influenced life history strategies of the upland bully populations investigated here. Note  相似文献   

17.
Hogfish, Lachnolaimus maximus (Walbaum), have multiple traits that confound measuring reproductive potential: they are protogynous, relatively long‐lived harem‐forming fish that spawn daily for months. Additionally, recent evidence demonstrates that size, age and timing of sex change vary on a spatial scale within the study area (West Florida shelf, USA). This study investigates the effect of this spatial variation on hogfish reproductive potential by evaluating spawning seasonality, spawning frequency and batch fecundity using an indeterminate egg production model. Offshore females were larger than nearshore females, and batch fecundity was related in a log‐linear manner to female size. Gonad histology demonstrated a more protracted reproductive period for females offshore (8 months) than nearshore (4 months). Spatial variations in size coincide with ontogeny because hogfish move offshore with growth; however, even after accounting for fish size, offshore females spawned more. In areas where male removal rates are elevated, spawning harems are disrupted; thus, greater fishing effort nearshore may further reduce the reproductive potential of these females. These nearshore and offshore spawning components of the population are not genetically distinct, but instead represent two contingent spawning strategies that likely enhance total population stability and resilience of this stock in the eastern Gulf of Mexico.  相似文献   

18.
ABSTRACT: The dolphin fish, Corphaena hippurus Linnaeus, is one of the most important migratory fishes on the east coast of Taiwan. Present results are based on an investigation of 1439 specimens caught using long-line and driftnet, and set net collected monthly between September 1996 and September 1997. The sex ratio of female to male and female combined was 65%, demonstrating a female predominance. Oocytes became mature and transparent when they attained 1.0 mm in diameter. The total number of oocytes per ovary was estimated to range from 2.78 × 105 to 23.48 × 10>5, but batch fecundity was noticeably lower than the total number of ovarian eggs, ranging 5.3–32.7% (average 30.1%), and the relative fecundity ranging 10–344/g bodyweight (mean 111/g bodyweight). Minimum body size at sexual maturity was estimated to be 51 cm for both sexes. Dolphin fish spawned throughout the year with reproductive activity peaking in February to March. It is suggested that the dolphin fish has an extended spawning season, during which it lays eggs almost continuously.  相似文献   

19.
This study selected small (100–120 μm) egg-bearing females from a local Thai ss population and characterized their first offspring's life history in an attempt to produce small-size rotifers. Mean lorica length of selected small adult females was 120 ± 6 μm at the time of collection, and this mean length did not increase over their lifetime. While their first offspring life span was only 5.11 ± 0.35 d, the reference population longevity was higher, 9.65 ± 0.4 d. The length of reproductive period of offspring from the small-size egg-bearing female was 2.58 ± 0.38 d, shorter than that of reference population 6.83 ± 0.58 d. Although the rate of egg production was not different between small egg-bearing female and reference population, the total number of eggs produced by the small egg-bearing female's first offspring was lower (4.78 ± 0.60) compared to the reference population (11.83 ± 1.26). The small egg-bearing female's first offspring had a higher egg to lorica length ratio (76.1 ± 1.64%) than the reference population (56.6 ± 1.3%), indicating a relatively high investment in reproduction. The small egg-bearing female's first offspring reached only 125 ± 6 μm in 36 h, and further culture of their offspring over 35 d resulted in a mean offspring size, 163 ± 11 μm, similar to the reference population (159 ± 16 μm). This shows that population mean size reduction is not likely to result from selecting small egg-bearing females within a single generation. The unique reproductive characteristics of small egg-bearing female place it in its own category.  相似文献   

20.
Maternal effects have been observed to interact with genotypic and environmental influences to structure offspring phenotypes across a wide variety of taxa. In fishes, maternal effects may be especially important due to their potential influence on development and survival during early ontogeny – a period with high potential for population regulation. While previous studies have confirmed that maternal effects on offspring phenotype are common in fishes, the consistency with which they positively affect offspring fitness throughout early ontogeny remains largely unknown. We examined maternal effects on offspring fitness by quantifying relationships between maternal (length, mass and age), egg (diameter, mass and density) and larval traits (length, yolk‐sac volume and survival) in yellow perch (Perca flavescens). Consistent with several past studies, positive relationships among maternal and egg traits were evident. While egg mass was positively related to larval size at hatching, direct relationships between maternal and larval metrics were not apparent. Larval survival appeared to have two critical periods; in contrast with expectations, survival in the first 5 days posthatch was strongly negatively related to female size and age, while survival over the following 9 days was unrelated to maternal traits. Throughout the study, survival was positively related to yolk‐sac volume. Our unexpected observation of a negative relationship between maternal size and age and initial larval survival indicates that maternal effects may not be consistent throughout larval ontogeny. In fact, maternal effects appear to be dynamic influences on offspring fitness, and may have complex effects on individual‐ and population‐level reproductive success.  相似文献   

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