Phenotypic plasticity of life-history traits in clonal and sexual fish (Poeciliopsis) at high and low densities

Models of resource allocation strategies predict an array of life-history responses of individuals living in resource-stressed versus non-stressed environments. I tested a number of these predictions using three fish strains (a sexual and two clonal strains) in high and low density treatments. To examine the plasticity of life-history traits in females raised in these two environments, I measured survival, growth, egg production, egg size, and proportion mature at 10 weeks of age. Survival was not affected by density treatment. However, both growth and overall egg production were lower in females from the high density treatments, and reproductive maturity was significantly delayed at the high density for all strains. Egg production per unit size was not affected by density in any strain, signifying that differences in the numbers of eggs produced was merely a reflection of the differences in size of fish in the two density treatments. Egg size was also unaffected by density in all strains. These results are related to models of resource allocation in stressful environments. There was a consistent pattern of increased reproductive investment in the sexual strain relative to the two clonal strains. The sexual strain matured earlier, produced more eggs per unit body weight, and had larger eggs than either clone at both densities. These results are interpreted by considering the predicted adaptive responses of these three strains to the long-term environmental differences in their natural habitats.     

Effects of food stress and density in different life stages on reproduction in a butterfly

Availability of adequate nutrition and (rearing) density are among the most important factors affecting growth, development and reproduction in animals. In holometabolous insects diets and energetic needs change between life stages, with storing of larval resources, adult feeding and reproduction being linked strategies. Nevertheless, studies investigating nutritional (and density) effects across metamorphic boundaries are largely lacking. We aim at disentangling the functional basis of reproductive patterns by independently manipulating larval and adult (1) density and (2) access to food, respectively, in the tropical butterfly, Bicyclus anynana. (1) A high larval rearing density had, contrary to common wisdom, very little impact on body size, but reduced larval development time through increased growth rates. The latter is thought to be an adaptation to high densities, driven by the risk of larval food resources becoming exhausted before reaching metamorphosis. Larval density and male company during oviposition (i.e. adult density) had no detectable effects on female reproduction. (2) Larval food stress prolonged larval development time and reduced larval growth rate, body size, fecundity and reproductive investment. Detrimental effects on female reproduction were mediated through a reduction in body size. Additional negative effects of adult food stress on fecundity were largely confined to females being fed as larvae ad libitum, while those being previously starved showed reduced performance regardless of adult income. Effects on egg size were inconsistent and, overall, marginal. Our results show that restricted food access in different developmental stages may set different limits to reproduction, either posed by shortage of larval‐derived storage reserves (i.e. nitrogenous compounds) or adult income (i.e. carbohydrates). Thus, one should be cautious when stating that one or the other type of nutrients is ultimately limiting to reproduction. Rather, our findings highlight the importance of resource congruence and of considering both, larval‐ and adult‐derived resources for reproduction.     

SEVERE COSTS OF REPRODUCTION PERSIST IN ANOLIS LIZARDS DESPITE THE EVOLUTION OF A SINGLE‐EGG CLUTCH

A central tenet of life‐history theory is that investment in reproduction compromises survival. We tested for costs of reproduction in wild brown anoles (Anolis sagrei) by eliminating reproductive investment via surgical ovariectomy and/or removal of oviductal eggs. Anoles are unusual among lizards in that females lay single‐egg clutches at frequent intervals throughout a lengthy reproductive season. This evolutionary reduction in clutch size is thought to decrease the physical burden of reproduction, but our results show that even a single egg significantly impairs stamina and sprint speed. Reproductive females also suffered a reduction in growth, suggesting that the cumulative energetic cost of successive clutches constrains the allocation of energy to other important functions. Finally, in each of two separate years, elimination of reproductive investment increased breeding‐season survival by 56%, overwinter survival by 96%, and interannual survival by 200% relative to reproductive controls. This extreme fitness cost of reproduction may reflect a combination of intrinsic (i.e., reduced allocation of energy to maintenance) and extrinsic (i.e., increased susceptibility to predators) sources of mortality. Our results provide clear experimental support for a central tenet of life‐history theory and show that costs of reproduction persist in anoles despite the evolution of a single‐egg clutch.     

Is oxidative stress a physiological cost of reproduction? An experimental test in house mice

Investment in reproduction is costly and frequently decreases survival or future reproductive success. However, the proximate underlying causes for this are largely unknown. Oxidative stress has been suggested as a cost of reproduction and several studies have demonstrated changes in antioxidants with reproductive investment. Here, we test whether oxidative stress is a consequence of reproduction in female house mice (Mus musculus domesticus), which have extremely high energetic demands during reproduction, particularly through lactation. Assessing oxidative damage after a long period of reproductive investment, there was no evidence of increased oxidative stress, even when females were required to defend their breeding territory. Instead, in the liver, markers of oxidative damage (malonaldehyde, protein thiols and the proportion of glutathione in the oxidized form) indicated lower oxidative stress in reproducing females when compared with non-reproductive controls. Even during peak lactation, none of the markers of oxidative damage indicated higher oxidative stress than among non-reproductive females, although a positive correlation between protein oxidation and litter mass suggested that oxidative stress may increase with fecundity. Our results indicate that changes in redox status occur during reproduction in house mice, but suggest that females use mechanisms to cope with the consequences of increased energetic demands and limit oxidative stress.     

Opposing effects of heat stress on male versus female reproductive success in Bicyclus anynana butterflies

In ectothermic organisms, reproductive success and survival are vitally affected by temperature. Here, we analyzed the effects of a short-time exposure to heat stress (1 h at 40 °C versus controls) on reproductive success and longevity in Bicyclus anynana butterflies. After having applied heat stress or a control treatment, individuals were mated in all four possible sexes by treatment combinations. Heat exposure of females caused a subsequent reduction in longevity, fecundity, egg size and concomitantly reproductive investment. Heat exposure of males also reduced longevity, but had in general little effect on the reproduction of female mates. However, females having mated with heat-stressed males showed surprisingly an increased rather than decreased early fecundity, which may indicate an increased investment in current reproduction in stressful environments. Heat stress had no significant effect on egg hatching success, time to copulation and copulation duration. Our results suggest that a short period of heat stress may substantially reduce longevity and reproductive output, with striking differences among sexes. We found no evidence for males being more strongly affected by heat stress than females.     

Density effects on life-history traits of an island lizard population

Long-term monitoring of life-history traits and the effects of density upon them were studied in an island population of the lizardEumeces okadae. Although life-history traits such as clutch size, egg size and the proportion of mature reproductive females varied little over 7 years in the intact population, manipulation of density to simulate decreased population density enhanced juvenile growth rate, age at first reproduction, frequency of female reproduction and size-specific clutch mass. In particular, the proportion of mature females reproducing annually increased almost 10 times from 5.6% to 53.8% after the removal of some lizards. However, body size at first reproduction and egg size were almost identical under both high and low density conditions. This study suggests that there were strong density-dependent effects on several life-history traits and thatE. okadae attained a density close to the carrying capacity of the environment.     

Optimal resource allocation of the marine bivalve Yoldia notabilis: The effects of size-limited reproductive capacity and size-dependent mortality

The effects of the morphological constraint of maximum reproductive output (reproductive capacity) and the size at which individuals can avoid heavy mortality (refuge size) on the resource allocation pattern between growth and reproduction are investigated using a dynamic modelling approach for a population of Yoldia notabilis (Mollusca: Bivalvia) in Otsuchi Bay, northeastern Japan. A state variable model is developed using field data on shell length, somatic weight, production, survivorship and reproductive capacity of the bivalve. The optimal allocation pattern is characterized by sudden switching from growth to reproduction without the assumption of reproductive capacity, while simultaneous investment in growth and reproduction becomes optimal when maximum reproductive output is limited by reproductive capacity. Size-specific reproductive effort, size at maturity and the growth curve predicted by the latter model fit more closely to the field data, suggesting that size-limited reproductive capacity can play an important role in the evolution of the observed resource allocation pattern. The mortality pattern affects optimal size at maturity, but not size-specific reproductive effort after maturity. When refuge size is fixed, optimal size at maturity increases with survivorship above refuge size. Optimal size at maturity changes in a more complex way with changes in refuge size. Size at maturity remains constant when refuge size is small, increases when it is intermediate, and decreases when it is large. The results suggest that refuge size is an important factor in the evolution of size at maturity, although its contribution varies depending on the values of other factors, such as size-dependent production and survivorship above refuge size. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reassessing Breeding Investment in Birds: Class-Wide Analysis of Clutch Volume Reveals a Single Outlying Family

Reproductive investment is typically considered in terms of size and number of propagules produced. Compared with a thorough understanding of the overall patterns and ecological correlates of avian clutch size, egg size has received less attention and the total effort invested in laying a clutch of eggs is rarely considered. We used clutch volume as an alternative estimate of reproductive investment and present the first class-level analysis of clutch volume in birds using 1,364 randomly-selected species in 204 families. The relationship between body mass and egg volume was very strong (r² = 0.946), validating previous studies identifying four families (Apterygidae, Pelecanoidiididae, Sternidae and Dromadidiae) with disproportionately large eggs. Clutch volume was also closely related to body mass (r² = 0.909) and all but one of the taxa with disproportionately large eggs conformed to the overall relationship, their greater egg dimensions compensated by diminished clutch size. The only family which departed significantly from the relationship between body mass and clutch volume was the mound builders (Megapodiidae)—the only group of birds that do not rely on body heat for incubation. Although previously known for laying large clutches of large eggs containing disproportionately large yolks, the remarkable investment of megapodes in reproduction (more than seven times greater than other birds of comparable mass) has been hitherto overlooked. We consider the evolutionary basis and ecological implications of this finding, suggesting that energetic costs associated with incubation act as an upper limit on reproductive output of other birds. We recommend clutch volume as a sensitive, fine-grained measure of reproductive effort for research at a wide range of scales and advocate further analysis of ecological correlates of clutch volume in birds and amniotes generally.     

Is There Adaptive Value to Reproductive Termination in Japanese Macaques? A Test of Maternal Investment Hypotheses

Evolutionary biologists often argue that menopause evolved in the human female as the result of selection for a postreproductive phase of life, during which increased maternal investment in existing progeny could lead to enhanced survivorship of descendents. Adaptive theories relating menopause to enhanced maternal investment are known as the mother (first-generation) and grandmother (second-generation-offspring) hypotheses. Although menopause—universal midlife termination of reproduction—has not been documented in primates other than humans, some researchers have argued that postreproductive alloprimates also have a positive impact on the survivorship of first and second generation progeny. We tested the maternal investment hypotheses in Japanese macaques by comparing the survivorship of offspring, final infants, and great-offspring of females that terminated reproduction before death with females that continued to reproduce until death. SURVIVAL analyses revealed no significant difference in the survivorship of descendents of postreproductive and reproductive females, though final infants of postreproductive females were 13% more likely to survive than final infants of females that reproduced until death were. We also explored possible differences between these two groups of females, other than survivorship of progeny. We found no difference in dominance rank, matrilineal affiliation, body weight, infant sex ratio, age at first birth, fecundity rate or lifetime reproductive success. However, postreproductive females are significantly longer-lived than reproductive females and as a result experienced more years of reproduction and produced more infants in total. Apart from final infants, offspring survival is marginally lower in postreproductive females. Since offspring survival is not significantly enhanced in postreproductive females, the greater number of infants produced did not translate into greater lifetime reproductive success. Our findings fail to support the maternal investment hypotheses and instead suggest that reproductive termination in this population of Japanese macaques is most closely associated with enhanced longevity and its repercussions.     

Thermal dependence of reproductive allocation in a tropical lizard

In ectotherms, environmental temperature is the most prominent abiotic factor that modulates life-history traits. We explored the influence of environmental temperature on reproduction in the Madagascar ground gecko (Paroedura picta) by measuring reproductive traits of females at constant temperatures (24, 27, 30 °C). Females of this species lay clutches of one or two eggs within short intervals. For each female, we measured egg mass for the first five clutches. For one clutch, we also measured the energetic content of eggs via bomb calorimetry. Temperature positively influenced the rate of egg production, but females at 30 °C laid smaller eggs than did females at either 24 or 27 °C. Dry mass of eggs scaled allometrically with wet mass, but this relationship was similar among thermal treatments. Females at all temperatures produced eggs with similar energy densities. Females at 24 °C allocated less energy per time unit (≈8 mW) to reproduction than did females from higher temperatures (≈12 mW). However, females at either 24 or 27 °C allocated significantly more energy per egg than did females at 30 °C. Our results demonstrate that a complex thermal sensitivity of reproductive rate can emerge from distinct thermal sensitivities of egg size, egg composition and clutch frequency.     

Effects of a food supplementation experiment on reproductive investment and a post-mating sexually selected trait in magpies Pica pica

Food availability is an important factor affecting breeding success in birds. Food supplementation experiments in birds have in general focused on the effects on reproductive success in terms of female investment (laying date, clutch size, egg size), however, it is also known that the estimation of mate quality based on sexually selected signals influences female reproductive investment. In the particular case of magpies, females use nest size, a post-mating sexually selected signal, to assess male's likelihood to invest in reproduction, and accordingly adjust reproductive investment (clutch size). Then, the possible effects of food supplementation on female reproductive investment could be mediated by other variables related to parental quality, such as nest size in magpies. In the present study, we explore if higher food availability in a magpie territory affected both male sexually selected traits (i.e. nest size) and female reproductive investment (laying date, egg size, clutch size). We performed a food supplementation experiment in which we experimentally increased food availability in several magpie territories, keeping others as controls. In food-supplemented territories, males built significantly larger nests and females significantly increased egg size by 4.1% compared to control females. Results suggest that the continuous provisioning of protein rich food allowed magpie females to increase egg size. However, laying date and clutch size did not differ between control and food-supplemented magpie pairs. Food availability also affected the relationship between female reproductive investment and nest size. In control territories, females decreased their egg size in response to a larger nest, whereas a tendency for the opposite relationship was revealed in food-supplemented territories. We discuss the possibility that magpie females adopt different strategies for reproductive investment according to food availability.     

Parents benefit from eating offspring: density-dependent egg survivorship compensates for filial cannibalism

Abstract Why should animals knowingly consume their own young? It is difficult to imagine many circumstances in which eating one's own young (i.e., filial cannibalism) actually increases an individual's fitness; however, filial cannibalism commonly co‐occurs with parental care in fishes. The evolutionary significance of filial cannibalism remains unclear. The most commonly accepted explanation is that filial cannibalism is a mechanism by which caring males gain energy or nutrients that they reinvest into future reproduction, thereby increasing net reproductive success. There is mixed support for this hypothesis and, at best, it can only explain filial cannibalism in some species. A recent alternative hypothesis suggests that filial cannibalism improves the survivorship of remaining eggs by increasing oxygen availability, and thus increases current reproductive success. This theory has received little attention as of yet. We evaluated the hypothesis of oxygen‐mediated filial cannibalism in the sand goby by examining the effect of oxygen and egg density on the occurrence of filial cannibalism, evaluating the effects of partial clutch cannibalism on the survivorship of remaining eggs, and comparing potential costs and benefits of filial cannibalism related to the net number of eggs surviving. Indeed, we found that oxygen level and egg density affected the occurrence of cannibalism and that simulated partial clutch cannibalism improved survivorship of the remaining eggs. Additionally, because increased egg survivorship, stemming from partial egg removal, compensated for the cost of cannibalism (i.e., number of eggs removed) at a range of cannibalism levels, filial cannibalism potentially results in no net losses in reproductive success. However, oxygen did not affect egg survivorship. Thus, we suggest a more general hypothesis of filial cannibalism mediated by density‐dependent egg survivorship.     

Effects of fatty acid and phosphorus content of food on the growth, survival and reproduction ofDaphnia

1. Mixtures of microencapsulated lipids and Scenedesmus quadricauda grown at different degrees of P limitation were used as food for Daphnia galeata in two growth experiments. Thereby, food quality in terms of ω3-fatty acid (ω3-FA) or phosphorus (P) content could be assessed without interference from other factors.
2. ω3-highly unsaturated fatty acids (ω3-HUFA), given to Daphnia as fish oil or eicosapentaenoic acid (EPA) together with non P-limited algae, decreased the time to first reproduction. When fed fish oil, somatic growth and survival were also enhanced. Linolenic acid also decreased the time to first reproduction but to a lesser extent than EPA.
3. Food quality depended to a large extent on the degree of P limitation of Scenedesmus , which is consistent with P limitation of Daphnia. The overall impact of P was always larger than the effect of ω3-FA. Growth, survival and reproduction were elevated when Daphnia were fed non P-limited Scenedesmus compared to treatments with P-limited algae.
4. The relative importance of ω3-HUFA and P content in the food changed over a C : P gradient, with stronger effects of ω3-HUFA at low C : P ratios.     

Reproductive strategy of the ghost shrimp Callichirus major (Crustacea: Axiidea: Callianassidae) from the southwestern Atlantic: sexual maturity of females,fecundity, egg features,and reproductive output

Reproduction and reproductive investment of females is an intriguing feature in axiidean shrimps. They have a cryptic behavior and great ecological importance in sediment turnover, and recycling of organic material and nutrient. Herein, we describe different aspects of the reproductive biology (size at sexual maturity of females, fecundity, egg characteristics, and reproductive output [RO]) of the ghost shrimp Callichirus major from the southeastern coast of Brazil. Females reached sexual maturity at sizes ≥11.85?mm dorsal oval length. Fecundity increased significantly with female size and varied between 1455 and 9931 eggs (average 4564 eggs). Individual egg volume almost doubled during embryogenesis, and average egg water content increased during the incubation period from 75.0 to 93.3%. The egg mass comprised on average 13.2% of the dry body weight of females. This relatively high RO value is probably compensatory to the relatively low number of ovigerous females in axiidean populations. The few published data on RO values suggest that female investment in reproduction of axiidean shrimps is somewhat higher than in other decapods. The high investment in egg production reflects most likely an effort to maximize the viability of the progeny. Studies with additional congeneric species will clarify whether there is a tendency of axiidean shrimps to have RO values at the upper end of the range reported for decapods.     

When to care for, abandon, or eat your offspring: the evolution of parental care and filial cannibalism

Parental care and filial cannibalism (the consumption of one's own offspring) co-occur in many animals. While parental care typically increases offspring survival, filial cannibalism involves the killing of one's young. Using an evolutionary ecology approach, we evaluate the importance of a range of factors on the evolution of parental care and filial cannibalism. Parental care, no care/total abandonment, and filial cannibalism evolved and often coexisted over a range of parameter space. While no single benefit was essential for the evolution of filial cannibalism, benefits associated with adult or offspring survival and/or reproduction facilitated the evolution of cannibalism. Our model highlights the plausibility of a range of alternative hypotheses. Specifically, the evolution of filial cannibalism was enhanced if (1) parents could selectively cannibalize lower-quality offspring, (2) filial cannibalism increased egg maturation rate, (3) energetic benefits of eggs existed, or (4) cannibalism increased a parent's reproductive rate (e.g., through mate attractiveness). Density-dependent egg survivorship alone did not favor the evolution of cannibalism. However, when egg survival was density dependent, filial cannibalism invaded more often when the density dependence was relatively more intense. Our results suggest that population-level resource competition potentially plays an important role in the evolution of both parental care and filial cannibalism.     

Intra-specific variations of egg size,clutch size and larval survival relatedto maternal size in amphidromous <Emphasis Type="BoldItalic">Rhinogobius</Emphasis> goby

Synopsis Newly hatched amphidromous Rhinogobius sp. CB (cross band type) larvae drift downstream to the sea to grow and develop before returning upstream as juveniles. Since larger and older individuals usually inhabit the upper reaches of rivers, larvae from larger females are more likely to suffer higher risks of starvation or predation during their longer migration to the sea. We examined the relationship between reproductive parameters (egg volume and clutch size) and maternal length. We collected adult Rhinogobius sp. CB along the course of the Aizu River (Wakayama Prefecture, Japan) and spawned them under laboratory conditions. We measured egg volumes and clutch sizes, as well as larval starvation tolerance. Both egg volume and clutch size increased with standard length or age of the maternal fish, while egg density in these clusters did not correlate with standard length. Gonad-somatic index (GSI) also tended to increase with maternal standard length. There was a significant positive correlation between egg size and the 72-h survival rate of unfed hatchlings. Intra-specific variation of egg volumes and clutch sizes in this species seems to be an adaptation for enhancing offspring survivorship during migration to the sea. Some females spawned a second time. Second spawned egg sizes were smaller than first spawned egg sizes, although there was no difference in clutch size between the two. Egg size variation between subsequent spawns may be an adjustment to the changes in seasonal environmental conditions.     

Annual variations in the reproductive traits of Pomatoschistus microps in a Mediterranean lagoon undergoing environmental changes: evidence of phenotypic plasticity

The spawning period of the common goby Pomatoschistus microps from 1993 to 1997 in the Vaccarès lagoon did not vary, except in 1997 when it was longer due to the reproduction of the young-of-the-year. Egg size and number, and reproductive allocation varied greatly with one year to another. Female common gobies increased both their fecundity per spawning act and their egg size from 1993 to 1995. The annual variation in the reproductive effort suggests a high phenotypic plasticity of reproductive traits in P. microps , in the face of environmental perturbations. In winter 1993–1994, a centennial flood of the Rhône River caused major hydrological changes in the lagoon in less than 1 week, affecting many invertebrates and fish for several years. The reproductive investment of the common goby increased, possibly as a consequence of those environmental changes.     

The effect of flight on reproduction in an outbreaking forest lepidopteran

Post‐flight reproductive investment by female insects may be limited as a result of a trade‐off in resource allocation between flight and reproduction. Outbreaking forest pests reduce their habitat quality as a result of severe defoliation when population densities are high. Female relocation to better‐quality habitats can increase offspring survival but reduce their reproductive fitness through flight. In the present study, the effect of flight on the capacity of female Choristoneura conflictana (Walker) (Lepidoptera: Tortricidae) to mate and produce eggs is examined. Females are flown on flight mills, and the subsequent reproductive capacity of each moth is assessed through measures of mating success and egg production. There is no effect of flight on commencement or the duration of mating. Although flight does not affect egg production directly, energy expenditure as a result of flight (as measured by weight loss) shows a negative correlation to potential fecundity, possibly indicating the resorption of eggs in some females. The effect of female size on fecundity is dependent on mating status, suggesting that energy allocated to reproduction is not dependent on flight treatment. Female moth longevity also has a significant effect on egg production but is dependent on flight and mating treatments. There is a relationship between energy expenditure to flight and reproduction in C. conflictana. Females that fly away from dense populations may produce fewer offspring, although this cost may be mitigated by improved offspring survivorship in less defoliated habitats.     

Age at mating and male quality influence female patterns of reproductive investment and survival

The trade‐off between the allocation of resources toward somatic maintenance or reproduction is one of the fundamentals of life history theory and predicts that females invest in offspring at the expense of their longevity or vice versa. Mate quality may also affect life history trade‐offs through mechanisms of sexual conflict; however, few studies have examined the interaction between mate quality and age at first mating in reproductive decisions. Using house crickets (Acheta domesticus), this study examines how survival and reproductive trade‐offs change based on females’ age at first reproduction and exposure to males of varying size. Females were exposed to either a large (presumably high‐quality) or small male at an early (young), middle (intermediate), or advanced (old) age, and longevity and reproductive investment were subsequently tracked. Females mated at a young age had the largest number of eggs but the shortest total lifespans while females mated at older ages produced fewer eggs but had longer total lifespans. The trade‐off between age at first mating and eggs laid appears to be mediated through higher egg‐laying rates and shorter postmating lifespans in females mated later in life. Exposure to small males resulted in shorter lifespans and higher egg‐laying rates for all females indicating that male manipulation of females, presumably through spermatophore contents, varies with male size in this species. Together, these data strongly support a trade‐off between age at first reproduction and lifespan and support the role of sexual conflict in shaping patterns of reproduction.     

Life history patterns of a livebearing fish in contrasting environments

Summary The population dynamics and energy allocations of the Gila topminnow, a small livebearing fish, were studied in two contrasting environments, a spring run of constant characteristics and a fluctuating desert wash. Topminnows grew and matured in two basic patterns. First, many fish in both areas matured the year after their birth. Second, spring fish born early in the breeding season grew rapidly, bred within five months, and died by eight months of age. Although spring fish assimilated more energy, wash fish actually expended more calories for growth and reproduction, partly because of lower maintenance costs. Reproductive effort of long-lived spring fish varied with age between 3.1 and 6.5%; whereas efforts of short-lived spring and wash fish increased steadily with age to 5.2 and 9.8%, respectively. Although spring fish produced eggs of higher energy content, females in both areas varied their investment per offspring, apparently tracking seasonal changes in the availability of food for fry. When long-lived spring fish experienced food shortage, they allocated less energy to both growth and reproduction; in contrast, wash and short-lived spring fish under similar conditions reduced only their growth allocation. The reproductive mass in spring fish appeared to be limited by food availability, incompletely filled the abdominal space, and reflected no tradeoff between fecundity and investment per offspring. Reproduction by wash fish appeared to be limited by body space and was characterized by a tradeoff between fecundity and egg size.