Seasonal changes in the biochemistry of lake seston

1. The quantity of seston was measured and the elemental carbon, nitrogen and phosphorus (C, N, P) and biochemical composition (carbohydrate, protein, lipid) of the < 53 μm size fraction in three temperate lakes during one year was analysed. The lakes differed in nutrient concentration and were characterized as oligotrophic, mesotrophic and eutrophic. Linear regression analyses defined associations between seston composition and either lake trophic status, depth or season. 2. The concentration of particulate organic seston was greatest during spring and autumn and lowest during the clear water period in early summer. Seasonal patterns in seston elemental and biochemical percentage composition (quality) were observed to be independent of differences in seston quantity. 3. Concentrations of seston C, N and P were high in most cases in the spring and autumn and low in summer. Concentrations of P were particularly high during late summer and early autumn in the metalimnion, perhaps because of recovery of P from anaerobic sediments and hypolimnetic waters. Because seston C and N did not increase as markedly as P, C : P and N : P ratios both declined in the autumn. Primary production was thought to be co-limited by N and P in all three of these lakes; however, the data suggested that N might be more important as a major limiting nutrient in the eutrophic lake as the metalimnion increased in depth in late summer and autumn. 4. Concentrations of protein, carbohydrate, polar lipid and triglyceride generally increased with lake type as expected (greatest in the eutrophic lake), but showed no relationship with water depth. As the year progressed, no significant changes were measured in protein and carbohydrate concentrations; however, the concentration of polar lipid decreased and triglyceride increased significantly with time of year. 5. The biochemical composition of seston varied during the year and among lakes; for example, in Lake Waynewood the proportion of protein composing the seston (percentage protein by weight) varied from < 10% to > 40%. No statistically significant patterns in the percentage protein or carbohydrate were found. However, the proportion of seston comprised of triglyceride decreased with lake type and increased during the year; whereas the proportion of seston as polar lipid increased with lake type and decreased during the year. Triglyceride comprised most of the lipid. Both protein : lipid and protein : carbohydrate ratios tended to be greatest in summer and lowest in the spring and autumn. 6. Relationships between samples and biochemical composition analysed by Canonical Correspondence Analysis (Canoco) indicated similar patterns in seasonal changes in seston biochemistry for the three lakes, with samples separated primarily by vectors for lake type (oligotrophic to eutrophic) and the percentage polar lipid (proportion of total lipid) and secondarily by vectors for date and water depth (epilimnion or metalimnion). 7. These seasonal biochemical changes in the seston food base were compared with biochemical changes known to occur in algae grown under N-or P-limited conditions in the laboratory, and the resultant quality of this algal food for suspension-feeding consumers (zooplankton). It was concluded that zooplankton were likely to be physiologically challenged by these distinct seasonal shifts in the quality of lake seston.     

Contrasting bacterioplankton community composition and seasonal dynamics in two neighbouring hypertrophic freshwater lakes

We characterized the bacterioplankton community and its seasonal dynamics in two neighbouring hypertrophic lakes by denaturing gradient gel electrophoresis (DGGE) analysis of short (193 bp) 16S ribosomal DNA polymerase chain reaction (PCR) products obtained with primers specific for the domain Bacteria. Lake Blankaart is turbid and has a high phytoplankton biomass and episodic cyanobacterial blooms, whereas biomanipulated Lake Visvijver is characterized by clearwater conditions and the establishment of a dense charophyte vegetation. Both lakes were dominated by bacterial groups commonly found in freshwater habitats (e.g. ACK4 cluster of Actinomycetes; ACK stands for clones isolated from the Adirondack mountain lakes) . Yet, cluster analysis and principal components analysis (PCA) revealed that taxon composition of the bacterioplankton community of the two lakes differs substantially and consistently throughout the season. During the study year (1998), the bacterioplankton community of both lakes showed a distinct seasonal pattern. Lake Blankaart showed a clear differentiation between winter, spring, summer and autumn. In Lake Visvijver, summer samples differed greatly from spring, autumn and winter samples. We hypothesize that the contrasting bacterioplankton in the two neighbouring shallow lakes is determined largely by the presence or absence of macrophytes.     

Impact of fish predation on cladoceran body weight distribution and zooplankton grazing in lakes during winter

1. It is well accepted that fish, if abundant, can have a major impact on the zooplankton community structure during summer, which, particularly in eutrophic lakes, may cascade to phytoplankton and ultimately influence water clarity. Fish predation affects mean size of cladocerans and the zooplankton grazing pressure on phytoplankton. Little is, however, known about the role of fish during winter. 2. We analysed data from 34 lakes studied for 8–9 years divided into three seasons: summer, autumn/spring and winter, and four lake classes: all lakes, shallow lakes without submerged plants, shallow lakes with submerged plants and deep lakes. We recorded how body weight of Daphnia and then cladocerans varied among the three seasons. For all lake types there was a significant positive correlation in the mean body weight of Daphnia and all cladocerans between the different seasons, and only in lakes with macrophytes did the slope differ significantly from one (winter versus summer for Daphnia). 3. These results suggest that the fish predation pressure during autumn/spring and winter is as high as during summer, and maybe even higher during winter in macrophyte‐rich lakes. It could be argued that the winter zooplankton community structure resembles that of the summer community because of low specimen turnover during winter mediated by low fecundity, which, in turn, reflects food shortage, low temperatures and low winter hatching from resting eggs. However, we found frequent major changes in mean body weight of Daphnia and cladocerans in three fish‐biomanipulated lakes during the winter season. 4. The seasonal pattern of zooplankton : phytoplankton biomass ratio showed no correlation between summer and winter for shallow lakes with abundant vegetation or for deep lakes. For the shallow lakes, the ratio was substantially higher during summer than in winter and autumn/spring, suggesting a higher zooplankton grazing potential during summer, while the ratio was often higher in winter in deep lakes. Direct and indirect effects of macrophytes, and internal P loading and mixing, all varying over the season, might weaken the fish signal on this ratio. 5. Overall, our data indicate that release of fish predation may have strong cascading effects on zooplankton grazing on phytoplankton and water clarity in temperate, coastal situated eutrophic lakes, not only during summer but also during winter.     

High swimming and metabolic activity in the deep-sea eel Synaphobranchus kaupii revealed by integrated in situ and in vitro measurements

Several complementary studies were undertaken on a single species of deep-sea fish (the eel Synaphobranchus kaupii) within a small temporal and spatial range. In situ experiments on swimming and foraging behaviour, muscle performance, and metabolic rate were performed in the Porcupine Seabight, northeast Atlantic, alongside measurements of temperature and current regime. Deep-water trawling was used to collect eels for studies of animal distribution and for anatomical and biochemical analyses, including white muscle citrate synthase (CS), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), and pyruvate kinase (PK) activities. Synaphobranchus kaupii demonstrated whole-animal swimming speeds similar to those of other active deep-sea fish such as Antimora rostrata. Metabolic rates were an order of magnitude higher (31.6 mL kg(-1) h(-1)) than those recorded in other deep-sea scavenging fish. Activities of CS, LDH, MDH, and PK were higher than expected, and all scaled negatively with body mass, indicating a general decrease in muscle energy supply with fish growth. Despite this apparent constraint, observed in situ burst or routine swimming performances scaled in a similar fashion to other studied species. The higher-than-expected metabolic rates and activity levels, and the unusual scaling relationships of both aerobic and anaerobic metabolism enzymes in white muscle, probably reflect the changes in habitat and feeding ecology experienced during ontogeny in this bathyal species.     

Homogenisation of water and sediment bacterial communities in a shallow lake (lake Balihe,China)

1. Planktonic and benthic bacterial communities hold central roles in the functioning of freshwater ecosystems and mediate key ecosystem services such as primary production and nutrient remineralisation. Although it is clear that such communities vary in composition both within and between lakes, the environmental factors and processes shaping the diversity and composition of freshwater bacteria are still not fully understood.
2. In order to assess seasonal and spatial variability in lake bacterial communities and identify environmental factors underpinning biogeographical patterns, we performed a large-scale sampling campaign with paired water and sediment sample collection at 18 locations during four seasons in Lake Balihe, a subtropical shallow fish-farming lake in mid-eastern China.
3. Pelagic and benthic bacterial communities were distinctly different in terms of diversity, taxonomic composition and community structure, with Actinobacteria, Bacteroidetes, Cyanobacteria and Alphaproteobacteria dominating lake water, and Acidobacteria, Bacteroidetes, Chloroflexi, Gammaproteobacteria and Deltaproteobacteria dominating sediment. Nevertheless, these two communities had stronger spatial concordance and overlap in taxa during spring and autumn seasons. Together, the main drivers of both the spatial and temporal variations in Lake Balihe bacterial communities were identified as water temperature, turbidity, nitrogen and phosphorus availability, and thermal stratification controlled by wind-mixing and activity of the dense farmed fish populations. Notably, populations affiliated with Firmicutes, known to be abundant in fish gut microbiome, were especially abundant in the summer season and locations where high fish biomass was found, suggesting a potential link between fish gut microbiome and the pelagic bacterial communities.
4. Our findings demonstrated seasonal homogenisation of pelagic and benthic bacterial communities linked to marked shifts in a set of seasonally-driven environmental variables including water temperature and nutrient availability.

     

Seasonal variation in phytoplankton composition and physical-chemical features of the shallow Lake Doïrani,Macedonia, Greece

Phytoplankton species composition, seasonal dynamics and spatial distribution in the shallow Lake Doïrani were studied during the growth season of 1996 along with key physical and chemical variables of the water. Weak thermal stratification developed in the lake during the warm period of 1996. The low N:P ratio suggests that nitrogen was the potential limiting nutrient of phytoplankton in the lake. In the phytoplankton of the lake, Chlorophyceae were the most species-rich group followed by Cyanophyceae. The monthly fluctuations of the total phytoplankton biomass presented high levels of summer algal biomass resembling that of other eutrophic lakes. Dinophyceae was the group most represented in the phytoplankton followed by Cyanophyceae. Diatomophyceae dominated in spring and autumn. Nanoplankton comprised around 90% of the total biomass in early spring and less than 10% in summer. The seasonal dynamics of phytoplankton generally followed the typical pattern outlined for other eutrophic lakes. R-species (small diatoms), dominant in the early phase of succession, were replaced by S-species (Microcystis, Anabaena, Ceratium) in summer. With cooling of the water in September, the biomass of diatoms (R-species) increased. The summer algal maxima consisted of a combination of H and M species associations (sensu Reynolds). Phytoplankton development in 1996 was subject to the combined effect of the thermal regime, the small depth of mixing and the increased sediment-water interactions in the lake, which caused changes in the underwater light conditions and nutrient concentrations.     

Yangtze finless porpoises along the main channel of Poyang Lake,China: Implications for conservation

Poyang Lake is the largest freshwater lake in China and flows into the Yangtze River. It is a traditional habitat for the endangered Yangtze finless porpoise, which has not been well investigated. To reveal the distribution of the porpoise in Poyang Lake, 12 passive acoustic surveys were conducted along 123 km of the main channel of the lake during different seasons (spring transition season, wet season, autumn transition season, and dry season) from 2008 to 2012. We counted the number of phonating porpoises encountered and calculated the detection rate (encountered individuals detected per kilometer). The median porpoise detection rates ranged from 0 to 0.65 individuals per kilometer during the different surveys. The highest median detection rate of 0.50 was detected in the autumn transition season. The seasonal shrinking of the lake during the dry season may cause a concentration of porpoises in the narrow channels and a high incidence of collisions with cargo ships and fishing boats. Conservation actions should be focused on the main channel of the lake during the dry and transition seasons. In addition, the expansion of the existing reserve to include areas with high porpoise detection rates is necessary.     

Digestive capacities,inbreeding and growth capacities in juvenile Arctic charr Salvelinus alpinus

Genetic variation in growth performance was estimated in 26 families from two commercial strains of Arctic charr Salvelinus alpinus. Physiological determinants of growth and metabolic capacities were also assessed through enzymatic assays. A relatedness coefficient was attributed to each family using parental genotypes at seven microsatellite loci. After 15 months of growth, faster growing families had significantly lower relatedness coefficients than slower growing families, suggesting their value as indicators of growth potential. Individual fish that exhibited higher trypsin activity also displayed higher growth rate, suggesting that superior protein digestion capacities can be highly advantageous at early stages. Capacities to use amino acids as expressed by glutamate dehydrogenase (GDH) activities were lower in the liver of fast‐growing fish (13–20%), whereas white muscle of fast‐growing fish showed higher activities than that of slow‐growing fish for amino acid metabolism and aerobic capacity [22–32% increase for citrate synthase (CS), aspartate aminotransferase (AAT) and GDH]. The generally higher glycolytic capacities (PK and LDH) in white muscle of fast‐growing fish indicated higher burst swimming capacities and hence better access to food.     

Seasonal changes in morphometric and biochemical endpoints in northern pike (Esox lucius), burbot (Lota lota) and slimy sculpin (Cottus cognatus)

1. Morphometric and biochemical endpoints were used to assess growth and energetics in young‐of‐the‐year (YOY) northern pike (Esox lucius), YOY burbot (Lota lota) and slimy sculpin (Cottus cognatus) collected upstream and downstream of a uranium mining operation in northern Saskatchewan, Canada. 2. Water sampled at sites downstream of uranium mining and milling effluent discharge was higher in certain trace metals (arsenic, molybdenum), ions (conductivity, hardness, ammonia and sulphate) and total dissolved solids compared with ecologically similar reference sites. 3. Overwinter survival potential was estimated by determining total body lipids and total body triglycerides in fishes collected in late autumn and early spring. Two‐factor anova indicated no site or season differences in total body lipids or triglycerides in YOY northern pike. In spring, burbot collected from the exposure site were higher in total body lipids and triglycerides compared with the previous autumn and compared with fish collected from the reference site. Slimy sculpin from both exposure and reference sites had lower total body lipid and triglyceride content in spring compared with the previous autumn. In addition, sculpin from the exposure site had lower total body lipids and triglycerides in spring compared with fish collected from the reference site. 4. Biochemical estimates of fish growth (muscle RNA/DNA ratio and muscle protein concentration) exhibited clear seasonal differences, with consistent decreases in this endpoint for all fish species in spring relative to the previous autumn at both exposure and reference sites. 5. Results for total body lipids and triglycerides were inconclusive and inconsistent between species and exposure scenarios. However, all species exhibited a similar seasonal decrease in muscle protein and to a lesser extent, muscle RNA/DNA ratio.     

Interplay between temperature,fish partial migration and trophic dynamics

Whereas many studies have addressed the mechanisms driving partial migration, few have focused on the consequences of partial migration on trophic dynamics, and integrated studies combining the two approaches are virtually nonexistent. Here we show that temperature affects seasonal partial migration of cyprinid fish from lakes to predation refuges in streams during winter and that this migration in combination with temperature affects the characteristics and phenology of lower trophic levels in the lake ecosystem. Specifically, our six‐year study showed that the proportion of fish migrating was positively related to lake temperature during the pre‐migration growth period, i.e. during summer. Migration from the lake occurred later when autumn water temperatures were high, and timing of return migration to the lake occurred earlier at higher spring water temperatures. Moreover, the winter mean size of zooplankton in the lake increased with the proportion of fish being away from the lake, likely as a consequence of decreased predation pressure. Peak biomass of phytoplankton in spring occurred earlier at higher spring water temperatures and with less fish being away from the lake. Accordingly, peak zooplankton biomass occurred earlier at higher spring water temperature, but relatively later if less fish were away from the lake. Hence, the time between phyto‐ and zooplankton peaks depended only on the amount of fish being away from the lake, and not on temperature. The intensity of fish migration thereby had a major effect on plankton spring dynamics. These results significantly contribute to our understanding of the interplay between partial migration and trophic dynamics, and suggest that ongoing climate change may significantly affect such dynamics.     

Seasonal changes in the biomass,distribution, and patchiness of zooplankton and fish in four lakes in the Sierra Nevada,California

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Growth chronologies of white sucker, Catostomuscommersoni, and lake trout, Salvelinusnamaycush: a comparison among lakes and between trophic levels

A growth chronology index was used to determine whether changes in ecosystem structure and function in lakes could be associated with fish growth histories. Growth chronologies were compared for white suckers, Catostomus commersoni, from Little Moose (oligotrophic), Oneida (eutrophic), and Cayuga (mesotrophic) lakes (New York) from opercular bone growth increments, and for lake trout, Salvelinus namaycush, from Little Moose Lake using otolith growth. The longevity of these species allowed the development of chronologies from 17 to 33 years in length using only contemporary collections. We used these chronologies to examine whether fish growth histories could be used as an index for ecosystem-scale changes. Specifically, we examined whether zebra mussel, Dreissena polymorpha, invasion in Oneida and Cayuga lakes in the early 1990s, and treatment of sewage effluent from dwellings around Little Moose Lake beginning during the late 1980s could be detected in white sucker and lake trout growth chronologies. White sucker growth in Oneida and Cayuga Lakes did not differ before and after zebra mussel invasions. Neither white sucker nor lake trout growth chronologies from Little Moose Lake reflect changes in growth expected with reduced productivity levels associated with improved sewage treatment. Growth chronologies of these two species did not detect the ecosystem-scale changes that occurred in the study lakes.     

保安湖水体细菌群落结构时空变化特征及驱动因子

为了探究保安湖水体细菌群落结构时空变化特征及驱动因子,研究于2019年春、夏、秋、冬四季采集保安湖水样,使用宏基因组测序技术对保安湖水体细菌群落的组成及多样性变化进行了研究。结果表明:(1)保安湖不同湖区细菌群落组成无显著差异(P>0.05);夏、秋季细菌丰富度、均匀度、香农及辛普森多样性指数均显著高于春、冬季(P<0.05),夏、秋季优势类群为变形菌门(Proteobacteria)、放线菌门(Actinobactetiota)、蓝藻门(Cyanobacteria),而春、冬季变形菌门(Proteobacteria)和放线菌门(Actinobactetiota)占主导地位;(2)温度、透明度、pH、溶解氧、高锰酸盐指数、叶绿素a及总磷等因素是保安湖水体细菌群落结构变化的重要驱动因子;(3)保安湖细菌群落构建过程在春、夏、秋季由随机性过程主导,在冬季由确定性过程主导;(4)保安湖细菌网络互作具有明显的季节特征,从春季到冬季,保安湖细菌种间相互作用逐渐紧密复杂。综上所述,保安湖水体细菌群落结构具有明显的季节变化特征,温度、透明度、pH、溶解氧、高锰酸盐指数等因素具有驱动水体细...     

A bioenergetic assessment of the influence of stocking practices on rainbow trout (Oncorhynchus mykiss) growth and consumption in a New Zealand lake

Summary

• 1 To investigate the carrying capacity and factors affecting growth of rainbow trout in Lake Rotoiti, we employed a bioenergetics model to assess the influence of stocking rates, timing of releases and prey abundance on growth and prey consumption. We hypothesised that stocking rates and prey abundance would affect growth and prey consumption by influencing per‐capita prey availability, and that the environmental conditions encountered by fish at the time of stocking would affect growth and consumption.
• 2 Prey consumption of stocked rainbow trout was calculated with the Wisconsin bioenergetics model. We calculated growth trajectories of released trout based on data from stocked trout that were released in spring and autumn from 1993 to 2009 and then re‐captured by anglers. Diet, prey energy density, body mass lost during spawning and lake temperature were measured locally.
• 3 Stocking timing had no effect on return rates to anglers or length or weight of caught fish. Although trout released in autumn were smaller than those released in spring, autumn‐released trout grew at a faster rate and had similar lengths and weights to spring cohorts after 2 years of growth in the lake. Modelled consumption parameters were negatively correlated with trout population size, suggesting that stocking rates (347–809 fish ha^?1 year^?1) caused density‐dependent effects on growth. Although common smelt (Retropinna retropinna) accounted for 85% of total prey consumption, no significant relationship was found between prey consumption by individual trout and adult smelt abundance, possibly because trout are targeting smaller smelt that our abundance estimate did not account for.
• 4 Releasing trout in autumn appears to be advantageous for growth, possibly because (i) temperature is more suitable for growth in autumn–winter than in spring–summer and (ii) prey for small trout is abundant in autumn. Mild winter conditions appear to enhance overwinter survival and growth of rainbow trout in warm‐temperate lakes compared to higher latitudes. This implies that moderately productive warm‐temperate lake ecosystems are highly suitable for trout growth in winter, but less so in summer, when lake stratification and high nutrient levels may create conditions suitable for algal blooms and hypolimnetic deoxygenation. High growth rates of trout in warm‐temperate lakes can therefore be supported by timing releases to coincide with favourable winter conditions.

     

不同季节高原鼢鼠乳酸脱氢酶活力和同工酶谱

目的:探讨高原鼢鼠对洞道低氧高二氧化碳环境的代谢适应机制。方法:用酶活力分析法,分析春季、夏季和秋季高原鼢鼠血清乳酸脱氢酶(LDH)活力、乳酸含量和组织LDH活力,用聚丙烯酰胺凝胶电泳法分析血清和组织LDH同工酶谱。结果:高原鼢鼠血清LDH活力在春夏秋三季具有明显的差异,春季高于夏季,夏季高于秋季,血清乳酸含量表现出同样的变化趋势;春季血清中五种同工酶条带都清晰可见,夏季血清中LDH5和LDH4清晰可见,秋季血清中只能看见LDH5带。骨骼肌、心肌和脑组织LDH活力较高,而且从春季到秋季显著降低;肝、肾和肺组织LDH活力较低,肝组织LDH活力春季显著高于夏季和秋季,夏秋两季之间没有明显差异;肾和肺组织LDH活力在春季与夏季之间没有明显差异,但秋季明显降低。心、肝、肺、肾、脑和肌肉组织LDH同工酶谱,在春夏秋三季都显示出五条带,并表现出明显的组织差异;各组织同工酶含量也有不同程度的季节差异。结论:高原鼢鼠体内糖酵解过程具有明显的季节性变化,从春季到秋季依次降低,这与它们的季节性活动特点和洞道中氧气和二氧化碳的季节性波动有关。     

Seasonal patterns in feeding ecology of three small fishes in the Biandantang Lake, China

Feeding ecology of three small fish species, Hypseleotris swinhonis, Ctenogobius giurinus and Pseudorasbora parva was studied seasonally in the Biandantang Lake, a small, shallow lake in central China. Gut length, adjusted for total body length, was significantly higher in spring than in other seasons for all the three species. Seasonal changes in gut length were not associated with changes in food quality. Weight of fore-gut contents, adjusted for body weight, was significantly higher in winter and spring than in summer and autumn in H. swinhonis and C. giurinus , and significantly higher in autumn than in spring and summer for P. parva. Percentage of empty fore-guts was highest in summer and lowest in spring for H. swinhonis and C. giurinus , and highest in winter and lowest in autumn for P. parva. Diet of the three small fishes showed apparent seasonal changes, and these changes reflected partly the seasonal fluctuations of food resources in environment. Diet breadth was high in winter and low in autumn for H. swinhonis , high in winter and low in spring and summer for C. giurinus , and high in autumn and low in spring for P. parva. Diet overlaps between pairs of species were biologically significant in most cases, except between H. swinhonis and P. parva in summer and autumn and between C. giurinus and P. parva in autumn.     

The plankton community of a young, eutrophic, Antarctic saline lake

A shallow, saline lake (Rookery Lake) close to the sea and surrounded by a penguin rookery was investigated during the austral spring and summer of 1996/1997. The proximity to the sea means that the lake is likely to have been formed recently during isostatic uplift. Inputs of carbon and nutrients from the penguin rookery have rendered Rookery Lake eutrophic compared with other brackish and saline lakes in the Vestfold Hills. Chlorophyll a concentration, bacterioplankton, heterotrophic nanoflagellate and phototrophic nanoflagellate abundances were all significantly higher than in other non-enriched lakes. The high productivity created seasonal anoxia during winter and spring below ice cover. The ciliate community resembled the marine community, and was dissimilar to that seen in older saline lakes within the Vestfold Hills. Thus Rookery Lake provides valuable evidence of the impact of natural eutrophication on an Antarctic lake, as well as of the evolution of the typical microbial community which dominates the older lakes of the Vestfold Hills. Accepted: 2 May 1999     

A wide window of migration phenology captures inter‐annual variability of favourable conditions: Results of a whole‐lake experiment with juvenile Pacific salmon

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Age and size-dependent variation in the seasonal timing and probability of reproduction among mature female pumpkinseed,Lepomis gibbosus

Synopsis In this study, we used pumpkinseed,Lepomis gibbosus, populations in two east-central Ontario lakes to test for age and size-dependent effects on the probability and timing of reproduction of mature females. Pumpkinseed body size characteristics differed in the two lakes; Little Round Lake harbours a stunted population and Beloporine Lake does not. Age-class distribution of mature females was determined by a maturity assessment on fish collected just prior to spawning and at the mid-spawning period, combined with an early-season capture-mark-recapture survey. Spawning females were collected throughout the breeding season to assess age and size-related temporal trends, and to compare their age and size distribution with that of mature females at large. The proportion of age 2 females in Little Round Lake that actually spawned was considerably lower than the proportion of mature age 2 females at large. Furthermore, age 2 females that spawned in this lake did not do so until late in the breeding season. In contrast, the proportion of young/small females spawning in Beloporine Lake was comparable to the proportion of young/small mature females at large, and both small and large females spawned throughout the breeding season. Small mature females in Little Round Lake may have had no other option but to spawn late in the season because of their poor body condition. In Beloporine Lake, condition factor early in the breeding season in age 2–4 females was higher than that of Little Round Lake females, suggesting that limited energy reserves in the spring may have prevented young Little Round Lake females from early spawning. Our results show that the likelihood and timing of reproduction are both age and size-dependent in some populations. Small individuals that delay seasonal maturation and spawn late in the summer probably contribute little to the population due to the restricted growth and reduced overwinter survival of their progeny.To whom correspondence should be addressed     

Brood predation pressure during parental care does not influence parental enzyme activities related to swimming activity in a teleost fish

Predation is considered one of the main costs to reproduction but is rarely examined from a physiological perspective. In particular, little is known about the influence of brood predation pressure on the physiology of parents engaged in care. Brood defense, even when there is no direct threat to the parent, can be costly as it requires constant vigilance and chasing predators to protect the developing brood and maintain parental investment (i.e., fitness). Our goal was to examine the influence of natural variation in nest predation pressure on the physiology of the teleost smallmouth bass Micropterus dolomieu, an animal that provides sole-paternal care for developing offspring. More specifically, we used indicators of anaerobic (lactate dehydrogenase [LDH]) and aerobic capacity (cytochrome c oxidase [CCO] and citrate synthase [CS]) in axial white muscle and pectoral red muscle to test for differences in antipredator performance of nest guarding males across six lakes with natural variation in nest predation pressure. Pectoral red muscle enzyme activities and protein concentrations were highly conserved among populations, while axial white muscle showed differences in LDH activities, CCO activities and protein concentrations. However, there was no evidence for higher metabolic capacities in fish from lakes with increased brood predation pressure. Clearly, factors other than predation pressure have a greater influence on white muscle metabolic capacities. Additional research is needed to clarify the extent to which biotic and abiotic factors influence the enzyme activity and organismal performance in wild animals, particularly at the level of the individual and population.