Are age-related variations in breeding performance greatest when food availability is limited?

Age-related improvements in reproductive performance in seabirds have been well documented, and may be explained by improvements in foraging efficiency or increased experience and reproductive effort with age. The interactive effects of parental age and food supply on reproductive performance, however, remain poorly understood. A widespread mass mortality of pilchards Sardinops sagax in southern Australian waters in 1998 provided a unique opportunity to investigate the effects of a sudden reduction in the availability of amajor prey species on Australasian gannets Morus serrator, an important local marine predator. Age-related differences in the breeding performance of gannets were evident in 1 year of reduced pilchard availability; when food was not limited, both young and experienced parents were equally capable of rearing chicks and had similar levels of breeding success. These data clearly demonstrate the interactive effects of parental age and food supply on breeding performance and suggest that such differences only become apparent when conditions become more stressful.

The comparative energetics and growth strategies of sympatric Antarctic and subantarctic fur seal pups at Iles Crozet

The period of maternal dependence is a time during which mammalian infants must optimise both their growth and the development of behavioural skills in order to successfully meet the demands of independent living. The rate and duration of maternal provisioning, post-weaning food availability and climatic conditions are all factors likely to influence the growth strategies of infants. While numerous studies have documented differences in growth strategies at high taxonomic levels, few have investigated those of closely related species inhabiting similar environments. The present study examined the body composition, metabolism and indices of physiological development in pups of Antarctic fur seals (Arctocephalus gazella) and subantarctic fur seals (Arctocephalus tropicalis), congeneric species with different weaning ages (4 months and 10 months, respectively), during their overlap in lactation at a sympatric breeding site in the Iles Crozet. Body lipid reserves in pre-moult pups were significantly greater (t₂₈=2.73, P<0.01) in subantarctic (26%) than Antarctic fur seals (22%). Antarctic fur seal pups, however, had significantly higher (t₂₆=3.82, P<0.001) in-air resting metabolic rates (RMR; 17.1±0.6 ml O₂ kg^-1 min^-1) than subantarctic fur seal pups (14.1±0.5 ml O2 kg^-1 min^-1). While in-water standard metabolic rate (SMR; 22.9±2.5 ml O2 kg^-1 min^-1) was greater than in-air RMR for Antarctic fur seal pups (t₉=2.59, P<0.03), there were no significant differences between in-air RMR and in-water SMR for subantarctic fur seal pups (t₁₂=0.82, P>0.4), although this is unlikely to reflect a greater ability for pre-moult pups of the latter species to thermoregulate in water. Pup daily energy expenditure was also significantly greater (t₂₇=2.36, P<0.03) in Antarctic fur seals (638±33 kJ kg^-1 day^-1) than in subantarctic fur seals (533±33 kJ kg^-1 day^-1), which corroborates observations that pups of the former species spend considerably more time actively learning to swim and dive. Consistent with this observation is the finding that blood oxygen storage capacity was significantly greater (t₉=2.81, P<0.03) in Antarctic (11.5%) than subantarctic fur seal (8.9%) pups. These results suggest that, compared with subantarctic fur seals, Antarctic fur seal pups adopt a strategy of faster lean growth and physiological development, coupled with greater amounts of metabolically expensive behavioural activity, in order to acquire the necessary foraging skills in time for their younger weaning age.

Ontogeny of body size and shape of Antarctic and subantarctic fur seals

Pre- and post-weaning functional demands on body size and shape of mammals are often in conflict, especially in species where weaning involves a change of habitat. Compared with long lactations, brief lactations are expected to be associated with fast rates of development and attainment of adult traits. We describe allometry and growth for several morphological traits in two closely related fur seal species with large differences in lactation duration at a sympatric site. Longitudinal data were collected from Antarctic (Arctocephalus gazella (Peters, 1875); 120 d lactation) and subantarctic (Arctocephalus tropicalis (Gray, 1872); 300 d lactation) fur seals. Body mass was similar in neonates of both species, but A. gazella neonates were longer, less voluminous, and had larger foreflippers. The species were similar in rate of preweaning growth in body mass, but growth rates of linear variables were faster for A. gazella pups. Consequently, neonatal differences in body shape increased over lactation, and A. gazella pups approached adult body shape faster than did A. tropicalis pups. Our results indicate that preweaning growth is associated with significant changes in body shape, involving the acquisition of a longer, more slender body with larger foreflippers in A. gazella. These differences suggest that A. gazella pups are physically more mature at approximately 100 d of age (close to weaning age) than A. tropicalis pups of the same age

The influence of age on reproductive success and diet in Australasian gannets (Morus Serrator) breeding at Pope's Eye, Port Phillip Bay, Victoria

The influence of age on reproductive success and diet was examined in ‘old’ (experienced; 12 years and older) and ‘young’ (5–8 years of age) Australasian gannets (Morus serrator) breeding at Pope’s Eye, Port Phillip Bay, Victoria during the 2002–2003 breeding period. Although food availability, as indicated by commercial fish catches, throughout this breeding period was low, there were no significant differences in breeding success or chick growth between groups. Nevertheless, old birds tended to have higher reproductive success, replacing more lost eggs and fledging chicks of a greater mass. However, old birds also laid more eggs that failed to hatch. Five fish species, including jack mackerel (Trachurus declivis), barracouta (Thyrsites atun), redbait (Emmelichthys nitidus), anchovy (Engraulis australis) and red mullet (Upeneichthys vlamingii), were important in the gannet diet during this breeding period. There were no significant differences in dietary parameters, including range of species and size of prey, between old and young gannets, nor were there any differences between those of the chicks and their parents, suggesting that adults do not forage selectively for their chicks. This study showed that even during a period of presumed low food availability, when experienced (older) birds might be expected to have enhanced success, the differences between these and less experienced (younger) birds may not be apparent.

Milk consumption, body composition and pre-weaning growth rates of Australian fur seal

Pre-weaning growth rates, body composition, milk consumption and mass gain efficiency were measured in Australian fur seal Arctocephalus pusillus doriferus pups born in two consecutive breeding periods. Australian fur seals have the highest birth mass of any fur seal species (male 8.3 kg; female 7.2 kg). While their absolute pre-weaning growth rate (male 62 g·day⁻¹; female 53 g·day⁻¹) is similar to that of other temperate latitude fur seals, they have the longest birth-mass doubling time of any otariid species (134–136 days). Daily milk consumption increased from 400 g·day−1 (5 MJ·day−1) after birth to 675 g·day⁻¹ (13.7 MJ·day⁻¹) at age 210 day. However, mean mass-specific milk consumption (41 g·kg⁻¹) is substantially lower than in other otariid species (58–70 g·kg⁻¹) and, combined with a low mass gain efficiency (0.12 g·g⁻¹), contributes to the low mass-specific growth rates observed. There were no significant differences in either absolute or mass-specific milk consumption between the sexes. Significant differences, however, were found between the sexes in the body composition of pups with females generally having larger body lipid stores than males for any given mass. Peak milk yield by Australian fur seal females is estimated at 0.60 MJkg−0.75, substantially less than in Antarctic fur seals. The low level of maternal energy transfer in Australian fur seals may reflect the relatively low marine productivity of their foraging areas.

Environmental and senescent related variations in Weddell seal body mass : implications for age-specific reproductive performance

Recent studies have found age-specific variations in reproductive performance amongst Weddell seals, Leptonychotes weddellii, and we hypothesized age-related variations in maternal body mass as a mechanism linking maternal age and the observed patterns of reproductive performance. We evaluated the effects of maternal traits such as age and reproductive experience and the effects of environmental variations on maternal body mass at parturition. Maternal body mass at parturition showed substantial age- and environmental-related variations. Maternal body mass increased with age through the young and middle ages, and evidence of senescent declines in body mass was found amongst the oldest ages. Additionally, body mass at parturition was strongly influenced by environmental variations during the pregnancy period, specifically sea-ice extent and the state of the El-Niño Southern Oscillation. Patterns of age-specific variations in body mass were consistent with age-specific patterns of offspring survival probability, which supported our hypothesis that changes in body mass link maternal age and reproductive performance in the Weddell seal. Further, environmental conditions during pregnancy may be an important component of Weddell seal reproductive performance.

Technical efficiency in Australian textile and clothing firms: evidence from the business longitudinal survey

This paper estimates technical efficiency of Australian textile and clothing firms based on the data obtained from the Business Longitudinal Survey (BLS) conducted by the Australian Bureau of Statistics (ABS). Using a Cobb Douglas stochastic production frontier the paper examines firm level technical efficiency in the time varying inefficiency effect model with technical inefficiency effects assumed as an independently distributed truncated normal variable. Estimates of the production frontier revealed significant but small elasticities of labour and capital for textile and clothing firms, respectively, and a negative (but insignificant) Hicks neutral technical change for both. Estimated coefficients of the explanatory variables for inefficiency effects indicated that technical efficiency varied significantly according to firms’ age, size, capital intensity, proportion of non-production to total workers and type of legal status. Predicted firm specific efficiency varied from 16 per cent to 95 per cent and mean efficiency ranged between 30 to 70 per cent. In view of these results policies have been suggested to improve technical efficiency of the firms as well as productivity growth of the sub sectors.

Evaluation of weaning strategies for intensively reared Australian fish, Murray cod, Maccullochella peelii peelii

The Australian Murray cod supports a growing national industry. However, with regard to the process of weaning fry, there is a lack of information and optimal procedures need to be developed. The aim of the present investigation was to test the biological and economic efficacy of different weaning strategies for Murray cod. Three weaning strategies were tested on triplicate groups of fish: (1) only Artemia for 5 d, 7 d on Artemia plus starter diet, and 14 d on dry diet only; (2) 12 d on Artemia plus starter diet and 14 d on dry diet only; and (3) directly to dry diet for the entire experimental period. No significant differences were recorded in the growth and feed efficiency, while significantly higher mortality (38.4 ± 0.35%) was recorded in fish weaned directly onto dry diet. Fish subjected to the first 5 d on Artemia only showed a growth reduction during this period, which was compensated by a phase of enhanced growth during the dry-diet phase. No significant differences were noted in the proximate composition of fish under the different treatments. The economic evaluation suggested that the treatment with the simultaneous supply of Artemia and starter diet is preferable.

The physiological and behavioural development of diving in Australian fur seal (Arctocephalus pusillus doriferus) pups

The physiological and behavioural development of diving was examined in Australian fur seal (Arctocephalus pusillus doriferus) pups to assess whether animals at weaning are capable of exploiting the same resources as adult females. Haematocrit, haemoglobin and myoglobin contents all increased throughout pup development though total body oxygen stores reached only 71% of adult female levels just prior to weaning. Oxygen storage components, however, did not develop at the same pace. Whereas blood oxygen stores had reached adult female levels by 9 months of age, muscle oxygen stores were slower to develop, reaching only 23% of adult levels by this age. Increases in diving behaviour corresponded to the physiological changes observed. Pups spent little time (<8%) in the water prior to moulting (age 1–2 months) whereas following the moult, they spent >27% of time in the water and made mid-water dives (maximum depth 35.7 ± 2.9 m) with durations of 0.35 ± 0.03 min. By 9 months (just prior to weaning), 30.5 ± 9.3% of all dives performed were U-shaped benthic dives (maximum depth 65.0 ± 6.0 m) with mean durations of 0.87 ± 0.25 min, significantly shorter than those of adult females. These results suggest that while Australian fur seal pups approaching the age of weaning are able to reach similar depths as adult females, they do not have the physiological capacity to remain at these depths for sufficient durations to exploit them to the same efficiency.

Synchronized group association in little penguins, Eudyptula Minor.

Most seabirds form groups on land and at sea, but there is little information whether seabird groups are formed deliberately or randomly. We investigated whether little penguins formed groups composed of the same individuals when they crossed the beach each day over four breeding seasons (2001–2004) using an automated penguin monitoring system (APMS). We used an association matrix to determine the number of times any two birds crossed the APMS in the same group. The number of these group associations or ‘synchronized parade’ behaviour was determined for every possible pair of individuals, giving a total association value for each pair of birds during the postguard stage of the reproductive cycle. We concluded that a penguin group was composed of 5–10 individuals within 40-s intervals. Penguin groups were formed nonrandomly in years of high breeding success (2002 and 2003), but not in years of low breeding success (2001 and 2004). Age of birds was a significant factor in composition of groups. Little penguins with higher association values shared similar characteristics or ‘quality’, which in turn may increase the functional efficiency of their groups, especially if they are also foraging together. However, low association indices indicated that seeking the same associates was not a priority. It is costly for any animal to synchronize their attendance with the same individuals, so it could be beneficial to display synchronized parade behaviour in good breeding years but it could result in intraspecific competition for food during poor breeding years.

Measurement of the economic impact of visual impairment from age-related macular degeneration in Australia

The purpose of this report was to: (i) outline the potential value of health economic studies into age-related macular degeneration (AMD); (ii) provide an overview of health economic studies pertinent to AMD; and (iii) outline the basic frame work of cost-of-illness studies (a useful first step in applying economic methods). The detection and management of sensory loss in the elderly plays a key role in the Australian Government's Healthy Ageing Strategy. Age-related macular degeneration is currently the leading cause of blindness in elderly Australians. Although a large proportion of AMD cases remain untreatable, the introduction of photo­dynamic therapy provides a relatively expensive and possibly cost-effective innovation for others. Antioxidant therapy has also been proven effective in reducing progression of early to late disease. The discipline of economics can contribute to an understanding of AMD prevention and treatment through: (i) describing the current burden of disease; (ii) predicting the changes in the burden of disease over time, and (iii) evaluating the efficiency of different interventions. Cost-of-illness studies have been performed in many fields of medicine. Little work, however, has been done on describing the economic impact from AMD. A number of different economic evaluation methods can be used in judging the efficiency of possible interventions to reduce the disease burden of AMD. Although complementary in nature, each has specific uses and limitations. Studies of the economic impact of eye diseases are both feasible and necessary for informed health care decision-making.

Long-term reproductive success of Australasian gannets (Morus serrator)

Life history theory predicts that individuals make trade-offs between investment in current reproduction, future reproductive potential and success in order to maximise lifetime reproductive success (LRS). Factors that may influence LRS in seabirds include delayed maturity, small clutches, high adults survivorship and long life spans. Studies have shown that reproductive success of seabirds increases with age and experience. Australasian gannets are long-lived seabirds that typically commence breeding at five or six years of age. A small colony of gannets was monitored over 12 years. This study aimed to identify patterns of long-term individual breeding biology. Results indicate that nest site, pair bond duration, age and breeding experience are all important factors in reproductive success. Relationships were found between breeding success and several variables including breeding experience, pair bond duration and nest site quality. Identifying and understanding the factors that contribute to individuals’ reproductive success is of critical importance for future conservation and management of seabird species.

Human sarcopenia reveals an increase in SOCS-3 and myostatin and a reduced efficiency of Akt phosphorylation

Age-related skeletal muscle sarcopenia is linked with increases in falls, fractures, and death and therefore has important socioeconomic consequences. The molecular mechanisms controlling age-related muscle loss in humans are not well understood, but are likely to involve multiple signaling pathways. This study investigated the regulation of several genes and proteins involved in the activation of key signaling pathways promoting muscle hypertrophy, including GH/STAT5, IGF-1/Akt/GSK-3β/4E-BP1, and muscle atrophy, including TNFα/SOCS-3 and Akt/FKHR/atrogene, in muscle biopsies from 13 young (20 ± 0.2 years) and 16 older (70 ± 0.3 years) males. In the older males compared to the young subjects, muscle fiber cross-sectional area was reduced by 40–45% in the type II muscle fibers. TNFα and SOCS-3 were increased by 2.8 and 1.5 fold, respectively. Growth hormone receptor protein (GHR) and IGF-1 mRNA were decreased by 45%. Total Akt, but not phosphorylated Akt, was increased by 2.5 fold, which corresponded to a 30% reduction in the efficiency of Akt phosphorylation in the older subjects. Phosphorylated and total GSK-3β were increased by 1.5 and 1.8 fold, respectively, while 4E-BP1 levels were not changed. Nuclear FKHR and FKHRL1 were decreased by 73 and 50%, respectively, with no changes in their atrophy target genes, atrogin-1 and MuRF1. Myostatin mRNA and protein levels were significantly elevated by 2 and 1.4 fold. Human sarcopenia may be linked to a reduction in the activity or sensitivity of anabolic signaling proteins such as GHR, IGF-1, and Akt. TNFα, SOCS-3, and myostatin are potential candidates influencing this anabolic perturbation.

Age-related changes in ovarian characteristices, plasma sex steroids and fertility during pubertal development in captive female Murray cod Maccullochella peelii peelii

Age-related changes in ovarian development characteristics and plasma sex steroids in female Murray cod were examined throughout their second, third and fourth years of life to better understand the physiological and endocrine processes associated with puberty in this species in captivity. Spawning performance of 2+ and 3+ year old females was also assessed to identify ontogenetic differences in egg fertility. Puberty was acquired in 38% of 1+ year old females and 100% of age 2+ females. By age 3+, all females had developed full (adult) reproductive function. Ovarian development in pubertal fish was characterised by a rapid transition between cortical alveoli and lipid droplet oogenic phases, coinciding with significantly lower plasma 17β-oestradiol in age 2+ females (p < 0.05). Mean mature oocyte diameter (2.44 mm), post-fertilisation viability (30.80%) and hatchability (0.99%) of eggs from age 2+ females were significantly reduced relative to age 3+ adults (2.81 mm, 84.89% and 23.58%, respectively). Ovaries of pubertal Murray cod exhibited both vitellogenic and ovulatory capacities, yet functional abnormalities during secondary oocyte growth are likely to have contributed to poor egg fertility and consequently, evaluations of age-at-first maturity based on the presence of advanced ovarian stages may overestimate the reproductive potential of younger broodstock populations.

Age, growth and reproduction of deepwater dogfishes from southeastern Australia

The productivity of six deepwater dogfishes was investigated by examining their age, growth and reproductive biology. A new method of ageing was developed, and compared with existing techniques. Some species live greater than 50 years, and populations may not sustain commercial fisheries.