Somatic Energy Research Articles

Migratory costs and the evolution of egg size and number in introduced and indigenous salmon populations.

The trade-off between reproductive investment and migration should be an important factor shaping the evolution of life-history traits among populations following their radiation into habitats with different migratory costs and benefits. An experimentally induced difference in migratory rigor for families of chinook salmon (Oncorhynchus tshawytscha), of approximately 86 km and 413 m elevation, exacted a cost to somatic energy reserves (approximately 17% reduction in metabolizable mass) and ovarian investment (13.7% reduction in ovarian mass). This cost was associated with a reduction in egg size and paralleled the phenotypic pattern of divergence between two introduced New Zealand populations of common origin, presently breeding at sites with different migration distances. The genetic pattern of divergence of these same populations, detected under common rearing, was consistent with compensation for migratory costs (the population that migrates farther invested more in ovarian mass), but egg number more than egg size was associated with this evolution. These evolutionary patterns are consistent with what is known of the inheritance of these traits and with trade-offs and constraints favoring initial evolution in offspring number over offspring size. Analysis of egg number-size patterns of other Pacific salmon populations in their native range supported the hypothesis that migration strongly influences patterns of reproductive allocation, favoring a higher ratio of egg number to egg size with greater migration distance.

Aspects of the reproductive biology of the toadfish, <i>Halobatrachus didactylus</i> (Schneider, 1801) (Pisces: Batrachoididae)

The biology of Halobatrachus didactylus has received special attention during recent years because of its use as an experimental species in toxicology and cardiology experiments. The object of the present work is to supply basic information about the reproductive biology of this species. Samples were collected in Cadiz Bay between February 1999 and March 2000. A total of 901 specimens (440 females and 461 males) were examined. Sex ratio did not differ from the theoretical 1:1, except in May 1999, and February 2000. Minimum size at maturity was 191 mm total length for females and 160 mm total length for males. Approximately 50 % of the population matured at 262 mm for females and 302 mm for males. The spawning season extends from March to August, with a peak in May-June. Fecundity ranged from 227 to 1233 eggs/female, and was related to body length and weight. Length-weight relationship for the sexes differed, and showed positive allometry. The condition factor showed a minimum in the spawning season, which is interpreted as the result of mobilization of somatic energy reserves needed for reproductive development, and/or the use of reserves stored in the body as a source of energy in spawned fish, influenced by reduced feeding during this period.

Energy reserves and reproductive investment in male three‐spined sticklebacks, Gasterosteus aculeatus

Abstract – In a 6‐month study of male sticklebacks from a single cohort of an annual population, energy reserves (carbohydrate, lipid and protein) in the carcass and gonad were found to increase from December to May. Energy reserves in the liver increased from December to March before declining between March and April, a period of marked gonadal growth in this population. Examination at the individual level of the interrelationships among the various components of the energy store (corrected for differences in body size) identified overall body condition as a major component of variation and highlighted a negative relationship between energetic investment in gonadal tissue and energy reserves in various somatic compartments. Early in the season, relative gonadal weight was largely unrelated to somatic energy reserves, but from March onwards there was a negative correlation between these two variables. These data suggest that a significant flux of glycogen and lipid from the somatic to the gonadal tissue occurs in male sticklebacks in the period just prior to the breeding season, with the extent of gonadal growth varying between individuals and occurring at the expense of overall nutritional status.Note

Energetic consequences of reproduction in Atlantic cod (Gadus morhua) in relation to spawning level of somatic energy reserves

The influence of a lower condition on reproductive investment, somatic energy losses, and postspawning condition of Atlantic cod (Gadus morhua) was examined under the hypothesis that females, in response to lower available energy reserves, would reduce reproductive investment in order to limit somatic energy losses. Laboratory experiments revealed that female cod with high prespawning condition factors ended reproduction in better condition than females with low prespawning condition factors. Fecundity and total egg dry weight were significantly lower in poor-condition females. The loss in somatic mass and energy in these poor-condition females was nevertheless higher, in relative terms, than the losses experienced by females in good condition. Consequently, energy reserves invested in reproduction by poor-condition females increase their risk of mortality. In the northern Gulf of St. Lawrence during the early 1990s, reproductive females had lower fecundities and were in worse prespawning and postspawning condition. The condition of spent females suggested a greater impact of changes in environmental conditions on adult than on immature cod. Reproductive potential and possibly recruitment may have suffered from that situation and could have contributed to the failure of that stock to recover despite the moratorium on commercial fishing.

Energetic consequences of reproduction in Atlantic cod (<i>Gadus morhua</i>) in relation to spawning level of somatic energy reserves

The influence of a lower condition on reproductive investment, somatic energy losses, and postspawning condition of Atlantic cod (Gadus morhua) was examined under the hypothesis that females, in response to lower available energy reserves, would reduce reproductive investment in order to limit somatic energy losses. Laboratory experiments revealed that female cod with high prespawning condition factors ended reproduction in better condition than females with low prespawning condition factors. Fecundity and total egg dry weight were significantly lower in poor-condition females. The loss in somatic mass and energy in these poor-condition females was nevertheless higher, in relative terms, than the losses experienced by females in good condition. Consequently, energy reserves invested in reproduction by poor-condition females increase their risk of mortality. In the northern Gulf of St. Lawrence during the early 1990s, reproductive females had lower fecundities and were in worse prespawning and postspawning...

Secondary sexual characters, energy use, senescence, and the cost of reproduction in sockeye salmon

Reproductive development and energy stores were characterized for sockeye salmon (Oncorhynchus nerka) maturing in the wild (Pick Creek, Bristol Bay, Alaska). Between freshwater entry and the start of spawning, ovaries increased in mass by 87.1% and secondary sexual characters increased in linear dimension by 13.0-47.4%. Between the start of spawning and death, secondary sexual characters decreased in relative size by 3.3-12.7%. Mass-specific somatic energy declined from freshwater entry (6.7% fat, 20.6% protein, 6.6 kJ·g-1) to the start of spawning (1.6% fat, 18.0% protein, 4.5 kJ·g-1) and finally to death (0.1% fat, 14.4% protein, 2.9 kJ·g-1). Stored fat appeared to be used primarily for upriver migration and egg production, whereas stored protein appeared to be used primarily for the development of secondary sexual characters and metabolism during spawning. Most development of secondary sexual characters occurred late in maturation, perhaps to forestall deterioration of muscle tissue. Relative to populations with long freshwater migrations, Bristol Bay sockeye salmon stored less fat before entering fresh water and used less fat before death. The total energy cost of reproduction (freshwater entry until death, including gonad investment) was 74.1% for females and 66.1% for males, higher than levels typically reported for iteroparous salmonids.

Winter Feeding and Changes in Somatic Energy Content of Age-0 Pacific Herring in Prince William Sound, Alaska

Abstract During the winter of 1996–1997, somatic energy content and diets of age-0 Pacific herring Clupea pallasi from Prince William Sound, Alaska, were examined. From October to March, the standard length of age-0 recruits continued to increase, indicating either growth or mortality of smaller fish. The whole-body energy content averaged 4.4 kJ/g wet weight for fish captured in October and increased to 5.0 kJ/g wet weight in November. Thereafter, somatic energy continually declined, reaching 3.9 kJ/g wet weight in March. The December–March decline in nutritional status of the recruits verified that the energy derived from feeding was not enough to meet metabolic needs. The energy density of taxa found in the diets remained steady through the winter and increased in March. Total zooplankton biomass, however, decreased as the mean water temperature decreased. Estimated assimilation rates were lower for smaller fish than larger fish and decreased as winter progressed. We concluded that juvenile herring rel...

Changes in proximate composition and somatic energy content for Pacific sand lance (Ammodytes hexapterus) from Kachemak Bay, Alaska relative to maturity and season

Mean dry-weight energy values of adult Pacific sand lance (Ammodytes hexapterus) peaked in spring and early summer (20.91 kJg−1 for males, 21.08 kJg−1 for females), then declined by about 25% during late summer and fall (15.91 kJg−1 for males, 15.74 kJg−1 for females). Late summer declines in energy density paralleled gonadal development. Gender differences in energy density (males<females) were only apparent from August to October. Adult sand lance spawn in October, entering the winter with close to their minimum whole body energy content. Juvenile sand lance exhibited a relatively constant protein to lipid ratio until they reached 80 mm fork length. Thereafter, relative proportions of protein remained constant while lipid proportions increased significantly. Dry weight energy densities of juveniles increased from a minimum 16.67 kJg−1 to a maximum of 19.68 kJg−1, and (per g) are higher than adults in late summer. The seasonal food value of adult sand lance to predators varies markedly, but maximum energetic value coincides with important feeding periods for marine mammals, fish, and seabirds.

Size-Based Variation in Somatic Energy Reserves and Parental Expenditure by Male Smallmouth Bass, Micropterus dolomieu

Size-Based Variation in Somatic Energy Reserves and Parental Expenditure by Male Smallmouth Bass, Micropterus dolomieu

The allometry of energy reserve depletion: test of a mechanism for size-dependent winter mortality.

We experimentally tested the hypothesis that energy reserve depletion varies inversely with size in the fish Menidia menidia, an estuarine fish known to exhibit size-dependent winter mortality. Individuals in two size groups were starved at two winter temperatures (4°and 8°C) and sacrificed at a range of time intervals (up to 127 days). Lipid levels and lean tissue were analyzed to estimate somatic energy storage. As predicted, energy depletion was greater at high temperatures, and proportionally greater in small than in large fish. After 60 days of starvation at 4°C, small fish retained an average of 67% of their original energy reserves (vs 53% at 8°C), while large fish retained an average of 80% (vs 66% at 8°C). At 4°C, fish that were fed depleted their energy reserves as rapidly as unfed fish, but at 8°C, fish that were fed maintained reserves at higher levels than unfed fish. A high proportion of unfed fish (56% at 4°C, 27% at 8°C) died before they were to be sacrificed. Survival probability did not vary with size, nor was it influenced by the amount of energy reserves. The rate of energy depletion (equivalent to routine metabolic rate) decreased gradually over time, particularly in small fish. Routine metabolism did not conform to a single scaling relationship. Within each temperature-size group, the routine rate declined more rapidly than metabolically active mass (lean mass). At 8°C, the difference between size groups in energy depletion rate conformed closely to the expected allometry exponent of 0.8. In contrast, at 4°C, the estimated allometry exponent increased over the experiment (-0.19 to 2.5). We conclude that strategies to minimize energy loss may often modify bioenergetic scaling relationships.

Condition Dependence and Adaptation-by-Time: Breeding Date, Life History, and Energy Allocation within a Population of Salmon

Correlations between breeding date and the life history or energy stores of individuals might stem from a combination of two different mechanisms. The conventional view is that individual size and condition influence breeding date (i.e., condition dependence). A different view is that heritable maturation schedules allow temporally separated population components to adapt to selective regimes associated with particular breeding times (i.e., adaptation-by-time). Considering each of these hypotheses, we examined a population of sockeye salmon (Oncorhynchus nerka) for evidence of correlations among life history traits (age, body size, egg size, and reproductive life span), patterns of energy allocation (somatic energy stores and gonadal investment), and breeding date. Life history traits were measured for 705 individually tagged adult salmon monitored from the onset of breeding until death. Energy stores were quantified for 60 fish collected when they entered the stream and 46 fish collected at death. Multiple regression models revealed that most of the variation could be explained by simple linear relationships among traits; older fish were larger, and larger lish had larger gonads, larger eggs, and more available energy when they started breeding. Condition dependence did not appear relevant to breeding date because fish that started breeding early were similar in size and did not have more stored energy than fish that would breed later. Similarly, adaptation-by-time had little influence on variation in body size or egg size (predicted relationships were significant but very weak). In contrast, adaptation-by-time appeared very important to variation in reproductive life span and patterns of energy allocation. Early-breeding fish lived considerably longer than late-breeding fish (females, R 2 =0.525; males. R 2 =0.533). This pattern arose because late-breeding fish expended more energy before breeding, and because late-breeding females invested more energy into egg production and retained less for metabolism during breeding. Adaptation-by-time may play an important role in life history evolution within some species, particularly those with breeding systems characterised by semelparity, capital breeding, and heritable breeding times.

Body composition and energy allocation in life‐history stages of brown trout

Energy contents of immature parr and smolts, and mature resident and anadromous brown troutSalmo truttasampled from a small stream in southern Norway were estimated from lipid, protein and carbohydrate concentrations. In immatures the lipid concentrations were highest in parr in the autumn. Mean lipid concentrations increased significantly with age in parr sampled in autumn (1·3% in age 0+ to 3·4% in age 3+), whereas they did not in smolts. The lipid concentrations of parr in spring were not significantly different from those of similarly aged smolts. By contrast, the relative water content (%) decreased with age in parr in the autumn and increased with age in smolts, mean values being slightly higher in smolts (78%) than in parr (77%). Protein and carbohydrate concentrations did not vary with age in the immature fish, mean protein concentrations being 18·0, 17·5 and 16·8% in parr in the autumn and spring, and in smolts, respectively. In residents, the concentrations of lipids were lower and of water higher, in age group 1 than in older fish, whereas there was no significant variation with age amongst anadromous trout. The energy concentration of 2+ smolts (349 kJ 100 g‐1) was similar to that of 0+ parr in the autumn. Mean somatic energy density in autumn was 1·1 times higher in freshwater residents than in parr at age 1+ (407 and 387 kJ 100 g‐1) and marginally different at age 2+ (462 and 426 kJ 100 g‐1, respectively). The energy contents per unit mass of residents were 1·3–1·6 times that of similar aged smolts. Mean somatic energy density of anadromous trout (504 kJ 100 g‐1) was higher than that of residents (455 kJ 100 g‐1). Somatic energy, lipid and protein concentrations were correlated highly with water contents of all life stages, age and sex groups.

Seasonal Changes in Whole-body Energy Content and Estimated Consumption Rates of Age 0 Walleye Pollock from Prince William Sound, Alaska

This study examined the somatic energy content and prey consumption needs of recruiting walleye pollockTheragra chalcogrammain one of Alaska's large estuaries to begin to evaluate the role of this species in the food-web. Age 0 pollock were collected from Prince William Sound in the fall and spring during 2 years. In the fall of 1995, few recruits <70mm standard length (SL) were present and the mean whole-body energy content (WBEC) was 3·6 (±0·2) kJg−1wet wt. In the following spring the 1995 year class survivors were ≥80mm SL and the mean WBEC was 4·0kJg−1(±0·5). In the fall of 1996 the age 0 pollock had an average WBEC of 3·6kJg−1(±0·2), identical to 1995, but smaller 60–70mm fish were common. In the spring of 1997 few fish <70mm were captured and WBEC averaged 3·4kJg−1(±0·4). In both years, recruits were generally able to maintain or improve their WBEC over the winter. There was marked variation in WBEC for fish from different collection sites.Changes in WBEC of the 1996 year class was monitored during their first year. On 13 June recently metamorphosed pollock had a SL of 34 (±5) mm and a mean WBEC of 2·7 (±0·2) kJg−1vs81 (±10) mm and 3·6 (±0·2) kJg−1on 6 October. Based on these mean values, growth rates for age 0 pollock during their first 119 days were 0·4mmday−1and 7·8Jg−1day−1. Modeling changes in body weight, energy content and metabolic demands for both active metabolism and growth allowed prediction of food intake over their first 270 days. Predicted wet wt of fish increased from an initial 0·37g to a high of 7·6g. Estimated food intake ranged from 0·21 to 1·29kJday−1.

Comparisons of whole body energy content of captive fasting age zero Alaskan Pacific herring ( Clupea pallasi Valenciennes) and cohorts over-wintering in nature

Changes in whole body energy content (WBEC) of captive age-0 Pacific herring ( Clupea pullasi Valenciennes) forced to fast during winter was measured and compared to cohorts collected in the field. Somatic energy content (kJ·g −1 wet wt) of fasting captives declined at a rate of 23 J·g −1 wet wt per day from 1 December 1995 to 25 January 1996 (56 days) at a mean temperature of 6.6°C. In another observation, fish captured on 1 December 1995 and held without feeding until 1 April 1996 (122 days) had an average WBEC that changed from 5.2 to 3.2 kJ·g −1 wet wt during captivity at about 5.2°C. Fish that died during fasts had WBEC values ranging from 2.8 to 3.6 kJ·g −1 wet wt. During March 1996 the WBEC of field collected age-0 herring averaged 3.8 kJ·g −1, with ≈40% having WBEC ≤3.6 kJ·g −1 wet wt. Thus, by March the average recruit had used most of its stored energy. These observations confirm that in the northern Gulf of Alaska region age-0 herring rely heavily on stored energy to survive their first winter.

Leptin: A Molecule Integrating Somatic Energy Stores, Energy Expenditure and Fertility

The signaling of fat mass to central nervous system (CNS) regulators of food intake, energy expenditure and fertility has been inferred by experimental physiologists for over 75 years. The ability to modify such phenotypes based upon the status of body energy stores (fat) has critical survival value and, therefore, has been the object of potent selection pressure in evolution. The recent molecular cloning of the mouse ob mutation and the subsequent elucidation of the fundamentals of its regulatory physiology has identified a protein secreted by adipocytes, leptin, as a plausible candidate for a humoral signal with the requisite endocrinology and neurobiology.

Fall and spring somatic energy content for Alaskan Pacific herring ( Clupea pallasi Valenciennes 1847) relative to age, size and sex

During the fall of 1995 and spring of 1996, the whole body energy content (WBEC) of Pacific herring ( Clupea pallasi Valenciennes 1847) from Prince William Sound, Alaska, was examined. Somatic energy (kJ·g −1 wet wt.) exhibited a wide range of values relative to fish length. In the fall young of the year (YOY) recruits had an average of 5.7 kJ·g −1 wet wt. for whole body samples vs. 8.0 for age 1 and 9.4–10.2 kJ·g −1 for fish of ages 2 to 7. The following spring the 1995 year class which had just survived their first winter averaged 4.4 kJ·g −1 wet wt. for somatic samples, and age 1 fish had similar values, while herring ages 2 to 7 had WBEC>5 kJ·g −1. The difference in somatic energy content between adult male and female fish captured in fall and again in the spring just prior to spawning, was about 4 kJ·g −1 wet wt., or about a 40% change. The difference in mean values for somatic energy content for YOY herring was only about 1.4 kJ·g −1 suggesting either the recruits ate more food during the winter than the adults, had lower energetic needs, or only those with higher than average energy stores survived the winter. The fall measures of WBEC showed the YOY and age 1 fish stored markedly less energy to over-winter than older herring. Thus, energetically the recruiting year class, and those entering their second winter, are the most at risk of over-winter mortality.

Production of the Crab Elamenopsis kempiHymenosomatidae in the Garmat‐Ali Region, Basrah, Iraq

Abstract. The production of the hymenosomatid crab Elamenopsis kempi was calculated for a period of 18 months from a subtidal area of the Garmat‐Ali river, southern Iraq. The highest average individual somatic energy was attained in spring. Maximum population biomass and production were attained by the summer cohort and the minimum values were exhibited by the overwintering cohort. The fluctuations of the average population biomass were followed throughout the sampling period. Average total annual population production was 13.2 g DW · m‐2· a‐1 and the P/B ratio was 5.9. These values were compared with those of the most common crustaceans in the region.

Seasonal changes in condition, nutrition, gonad maturation and energy content in barbel, Barbus sclateri, inhabiting a fluctuating river

The objective of this study was to investigate the seasonal cycle of condition, nutrition and gonad development, as well as the magnitude of seasonal variations in energy content of somatic and gonad tissues in juveniles, males and females of Sclater's barbel, Barbus sclateri, from the upper Guadalete River (south Spain). The influence of reproductive cycle on somatic changes was also investigated and discussed. Measurements of condition factor (K), somatic index (SI), gonadosomatic index (GSI) and somatic and gonad energy content (J g-1 dw) were made in individual specimens taken from the Guadalete River monthly for 12 months. This freshwater ecosystem is characterised by strong seasonal fluctuations in water and flow level, temperature and food supply. It was found that in general juveniles, males and females of barbel exhibited a similar condition, nutrition and somatic energy cycle throughout the year, with the highest values in spring and the lowest in summer. Depletion of K, SI and somatic energy storage from spring until mid-summer seems to be associated with high metabolic demands during this period, and in adult fish also with spawning-related activity. The gonad index and energy content of the gonad were the highest in April and the lowest in summer for both sexes. Spawning took place during late spring – early summer, with fish quiescent by mid summer. The energy required for ovarian development (3970 J g-1 dw) was greater than the one for testes development (2763 J g-1 dw). Data on gonad energy content indicated a period (March to April) of intense energy accumulation (64% males and 37% females) which was related to the decline in the average somatic energy content in males and females. The somatic energy content was linearly related to K and SI. In the same way, GSI correlated positively with gonad energy. Linear trends were found between somatic parameters (K, SI and energy content) and gonad parameters (GSI and energy content).

Energy allocation in polymorphic Brown Trout

1. To evaluate differences in energy allocation to gonadal development of resident and anadromous Brown Trout, Salmo trutta, we analysed tissue composition and energy contents of adults of the two morphs from three small streams in southernmost Norway. Somatic energy per unit mass of anadromous spawners (5·0 ± 0·6 kJ g–1 wet weight) was 1·1 times that of the residents. This difference was chiefly due to a 1·4 ‐times higher lipid content in anadromous (4·9 ± 1·5%) than resident trout. The somatic protein and carbohydrate contents per unit mass were higher in resident than anadromous fish. 2. Somatic energy content per unit mass increased linearly with body length in resident but not anadromous fish. This increase was due to a significant increase in lipid content with fish size in resident contrary to anadromous trout. 3. The mass‐specific energy content of the ovaries was higher for residents (8·4 ± 0·4 kJ g–1 wet weight) than anadromous (7·81 ± 0·5 kJ g–1 wet weight) trout. This was due to higher lipid and protein contents per unit mass in resident than anadromous females. In males, no similar differences between morphs were found (5·9 ± 0·8 kJ g–1 wet weight). The mass‐specific energy content of the ovaries was c. 1·4 higher than that of the testes, mainly caused by a 2·3–2·6 higher lipid content per unit mass of eggs. 4. The mean gonadosomatic index (kJ %) was higher in anadromous (34·0 ± 9·4) than resident (28·6 ± 5·5) females, but not in males (≈ 3%). In females, but not in males, gonadal energy increased linearly with increasing somatic energy of the fish. 5. Female gonadal energy at corresponding somatic energies was higher than that of males. On average, the energetic investment in gonads relative to soma of first‐time spawners in the year of maturation was estimated at 11% in males and 67% in females.

Changes in Proximate Composition and Estimates of Energetic Costs During Upstream Migration and Spawning in Atlantic Salmon Salmo salar

1. There were marked changes in the relative lipid content of somatic and visceral tissues during the course of upstream migration and spawning. The lipid content per 100 g wet tissue mass was high in maturing salmon in July (soma, pooled sexes: 12.1 g; viscera: 11.4g in males and 7.3 g in females) and decreased to a minimum after spawning in November (soma: 2.1 g; viscera: 1.6 g). Percentages of protein in the soma and viscera were relatively stable during the study period, ranging from 21.9 g (soma) and 16.3 g (viscera) 100 g -1 tissue in maturing fish in September-October, to 17.1 g (soma) and 16-1 g (viscera) in spent salmon. The carbohydrate content was relatively small, ranging between 0.27 and 2.4 g 100 g -1 wet tissue mass. 2. Application of energetic coefficients suggested that the somatic energy content decreased from 814 kJ 100 g -1 wet tissue mass in maturing salmon (pooled sexes) caught in coastal waters in July, to 370 kJ in spent fish in the river in November. Visceral energy density decreased in the same period, from 706 kJ in males and 570 kJ in females to 340 kJ and 360 kJ, respectively. 3. Mean gonadosomatic index (GSI) values, in terms of energy of males, in July and just prior to spawning were 0.4 and 3.2, respectively. The corresponding figures for females were 2.8 and 28.6. 4. Gonadal energy contents per unit tissue mass were estimated to be higher in females than males, except for spent fish. Prior to spawning energy content was 845 kJ 100 g -1 gonad wet mass in females and 375 kJ in males. After spawning the gonadal energy contents were 280 kJ and 385 kJ 100 g -1 wet mass, respectively. 5. The relative energy, lipid and protein contents of somatic, visceral and gonadal tissues were highly correlated with percentage tissue water. 6. Total energy loss due to migration and spawning was between 60% and 70% of the body reserves prior to upstream migration. It was similar for males and females, but higher in large than small salmon. Estimated energy investment due to reproduction correlated significantly with estimated survival rates in 12 Norwegian populations of Atlantic salmon.