Environmental factors regulating the recruitment of walleye Sander vitreus and white bass Morone chrysops in irrigation reservoirs

Understanding the environmental factors that regulate fish recruitment is essential for effective management of fisheries. Generally, first‐year survival, and therefore recruitment, is inherently less consistent in systems with high intra‐ and interannual variability. Irrigation reservoirs display sporadic patterns of annual drawdown, which can pose a substantial challenge to recruitment of fishes. We developed species‐specific models using an 18‐year data set compiled from state and federal agencies to investigate variables that regulate the recruitment of walleye Sander vitreus and white bass Morone chrysops in irrigation reservoirs in south‐west Nebraska, USA. The candidate model set for walleye included only abiotic variables (water‐level elevation, minimum daily air temperature during winter prior to hatching, annual precipitation, spring warming rate and May reservoir discharge), and the candidate model set for white bass included primarily biotic variables (catch per unit effort (CPUE) of black crappie Pomoxis nigromaculatus, CPUE of age‐0 walleye, CPUE of bluegill Lepomis macrochirus and CPUE of age‐3 and older white bass), each of which had a greater relative importance than the single abiotic variable (minimum daily air temperature during winter after hatching). Our findings improve the understanding of the recruitment of fishes in irrigation reservoirs and the relative roles of abiotic and biotic factors.     

Temperature,plankton and conspecific density influence dynamics of age‐0 gizzard shad: implications for a gape‐limited piscivore

Age‐0 gizzard shad Dorosoma cepedianum are the main prey fish for white crappies Pomoxis annularis in many US reservoirs. However, these prey fish commonly outgrow their vulnerability to white crappie predation in some, but not all, northern Missouri reservoirs. Potential variables that could influence abundance, growth and mortality of age‐0 gizzard shad were examined in three reservoirs that differed with respect to age‐0 gizzard shad growth rates. Because of thermal effluent from a power plant, gizzard shad spawned earlier in Thomas Hill Lake and initial densities of larvae were greater than in the other reservoirs. Larval and juvenile gizzard shad grew slowest in Thomas Hill Lake, followed by Mark Twain Lake and Long Branch Lake. Growth rate of larvae increased with increasing water temperature and food abundance, but decreased with increasing conspecific density. Similar relationships were found for juvenile growth, except that growth declined with increasing temperature. The slower growth of larvae and juveniles in Thomas Hill Lake was probably a consequence of their greater densities relative to their food abundance and higher water temperatures during the juvenile stage. Conversely, both larvae and juvenile gizzard shad grew more rapidly and juveniles attained large sizes in Long Branch Lake owing to their lower densities relative to their available food. Mortality of larvae and juveniles was mostly similar among the reservoirs. Because of their greater abundance and slower growth, gizzard shad were available as prey for white crappies for a longer period in Thomas Hill Lake than in the other reservoirs.     

Contrasting population demographics and reproductive investment of white crappie in three eutrophic reservoirs

Abstract White crappie, Pomoxis annularis Rafinesque, provides important sport fisheries across North America but sometimes exhibits slow growth and fails to reach sizes acceptable to anglers. Three dissimilar white crappie populations were studied to assess whether differences in growth were associated with size and age at maturity and subsequent larval production. Similar to other species, female white crappie matured at younger ages and smaller sizes and contained larger ovaries in the population with the slowest growth; this population also had the lowest annual mortality. Larval production (number m^?3) in this population was intermediate to that of the other populations. Attempts to improve growth of white crappie in the slow‐growing population will probably be hindered by these individuals’ greater reproductive investment, which reduces the amount of energy available for somatic growth.     

Effects of turbidity on foraging of juvenile black and white crappies

Turbidity can fluctuate rapidly during the early life of fishes, impacting foraging behaviours. For piscivores, turbidity may hinder foraging, whereas planktivores and juvenile fishes may increase foraging activity and decrease antipredator behaviours in moderate levels of turbidity. Black crappie (Pomoxis nigromaculatus) and white crappie (P. annularis) population trends are often related to changes in turbidity. Yet effects of turbidity on juvenile foraging of these species are unknown and may differ between species. To evaluate effects of three turbidity levels (0, 25 and 50 NTU) on juvenile crappie foraging, controlled experiments compared (a) consumption and size selection for a single prey and (b) selection, total consumption and energetic value of diets when offered three distinct prey options. Overall, black crappies exhibited universally greater diet biomass than white crappies. Black crappies displayed higher prey consumption and were more size selective of a single‐prey type, whereas white crappies were less size selective and maintained uniform consumption as turbidity increased. Selection patterns for three prey types were similar among species and turbidity levels, with Chaoborus preferred and Chironomus avoided. However, black crappies also avoided Daphnia, whereas white crappies consumed them neutrally. Overall, turbidity did not impair foraging of juvenile crappies. Turbidity‐driven fluctuations in prey base paired with predator interactions likely also contribute to observed growth and abundance fluctuations in natural systems.     

Hooking mortality of white crappie, Pomoxis annularis Rafinesque, and spotted bass, Micropterus punctulatus (Rafinesque), in Texas reservoirs

Abstract. This study was conducted to estimate spring hooking mortality of white crappie, Pomoxis annularis Rafinesque, in Buchanan Reservoir, Texas, USA and summer hooking mortality of spotted bass, Micropterus punctulatus (Rafinesque), in Eagle Mountain Reservoir, Texas, USA. Reservoir surface water temperatures averaged 19 and 31°C, during white crappie and spotted bass experiments, respectively. White crappie (mean total length (TL) 267mm, range TL 190–340mm, standard error (SE) TL 6mm) were caught with size 5 single hooks baited with golden shiner, Notemigonus crysoleucas (Mitchill), and spotted bass (mean TL 220mm, range TL 143–326mm, SE TL 7mm) were caught with artificial lures (spinners) fitted with size 4 or 5 treble hooks. Fish were held in cages for 72 h to observe delayed mortality. Four of 43 white crappie (9·3%, 95% one-tail, upper confidence limit (UCL) = 13·7%) died and four of 47 spotted bass (8·5%, UCL = 15·2%) died. One of the white crappie that died was a sublegal-length fish. The relevance of these findings to the management of white crappie and spotted bass sport fisheries is discussed. It is concluded that under any management strategy necessitating release of some portion of the catch of white crappie and spotted bass, high survival of that portion could be expected.     

Growth rates of rainbow smelt in Lake Champlain: effects of density and diet

Stritzel Thomson JL, Parrish DL, Parker‐Stetter SL, Rudstam LG, Sullivan PJ. Growth rates of rainbow smelt in Lake Champlain: effects of density and diet. Ecology of Freshwater Fish 2010. © 2010 John Wiley & Sons A/S Abstract – We estimated the densities of rainbow smelt (Osmerus mordax) using hydroacoustics and obtained specimens for diet analysis and groundtruthed acoustics data from mid‐water trawl sampling in four areas of Lake Champlain, USA–Canada. Densities of rainbow smelt cohorts alternated during the 2‐year study; age‐0 rainbow smelt were very abundant in 2001 (up to 6 fish per m²) and age‐1 and older were abundant (up to 1.2 fish per m²) in 2002. Growth rates and densities varied among areas and years. We used model selection on eight area–year‐specific variables to investigate biologically plausible predictors of rainbow smelt growth rates. The best supported model of growth rates of age‐0 smelt indicated a negative relationship with age‐0 density, likely associated with intraspecific competition for zooplankton. The next best‐fit model had age‐1 density as a predictor of age‐0 growth. The best supported models (N = 4) of growth rates of age‐1 fish indicated a positive relationship with availability of age‐0 smelt and resulting levels of cannibalism. Other plausible models were contained variants of these parameters. Cannibalistic rainbow smelt consumed younger conspecifics that were up to 53% of their length. Prediction of population dynamics for rainbow smelt requires an understanding of the relationship between density and growth as age‐0 fish outgrow their main predators (adult smelt) by autumn in years with fast growth rates, but not in years with slow growth rates.     

Biotic and abiotic controls on body size during critical life history stages of a pelagic fish,Pacific herring (Clupea pallasii)

Variation in growth and body size during critical life history stages can have important implications for life history schedules and survivorship. For Pacific herring (Clupea pallasii), there is still debate as to whether juvenile body size is governed by density‐dependent or ‐independent processes and few have evaluated whether the relative importance of either process shifts over the course of early ontogeny. We used a unique data set consisting of seasonal measurements of abundance, body size, and spatial distribution within a semi‐enclosed basin of Puget Sound (Washington State, U.S.A.) to measure the relative importance of temperature and cohort abundance on body size at distinct time periods, and evaluated whether density‐dependent habitat shifts might be responsible for density‐dependent growth. Over the 9 years of sampling (2001–2010) midsummer body size was positively related to temperatures experienced during the egg/yolk sac and larval stages and unrelated to cohort abundance. However, fall body size was negatively correlated with abundance and uncorrelated with both midsummer body size and temperature, indicating a shift from density‐independent to density‐dependent control over the course of the growing season. Thus, density‐dependent effects may supplant density‐independent effects exhibited early in herring life history. Our data on spatial distributions of herring and their zooplankton prey indicate that density‐dependent reductions in growth may be explained by density‐dependent habitat shifts that lead to reduce overlap of herring with zooplankton. Evidence of density‐dependent growth in marine fish populations is often attributed to exploitative competition, but our results suggest that these patterns may partly be mediated by density‐dependent distribution expansions in to prey‐poor habitat.     

Evaluating the relationship between yearling walleye,Sander vitreus,electrofishing catch‐per‐unit‐effort and density in northern Wisconsin lakes

Recruitment declines of walleye, Sander vitreus (Mitchill), observed in some northern Wisconsin lakes have resulted in management actions to evaluate and rehabilitate populations. An effective index for estimating relative abundance of yearling walleye is required. The objectives herein were : (a) to evaluate the relationship between yearling walleye electrofishing CPUE and density in northern Wisconsin lakes; (b) to test for the influence of lake‐specific factors on electrofishing catchability of yearling walleye; and (c) to develop an index whereby electrofishing CPUE can be used to quantify yearling walleye relative abundance. Yearling density was significantly positively related to electrofishing CPUE on a long‐term dataset from Escanaba Lake as well as a dataset including several lakes combined. Electrofishing catchability of yearling walleye was negatively related to lake‐surface area but was not related to other lake‐specific variables. This index can provide an efficient method to continue monitoring natural recruitment and also to evaluate survival of stocked walleye.     

Comparative effects of dietary l‐carnitine supplementation on diploid and triploid rainbow trout (Oncorhynchus mykiss)

This study compared the effects of dietary l ‐carnitine and ploidy on growth performances and fatty acid content in rainbow trout (Oncorhynchus mykiss). Fish [initial body weight (BW) = 30 g] reared under high density (50 kg biomass m^?3) were hand‐fed in triplicate (3 tanks treatment^?1, 34 fish tank^?1) twice a day, with three nutritionally identical diets containing 15, 200 or 530 mg l ‐carnitine kg^?1 of diet. No significant growth differences were observed over a 56‐day grow‐out period, during which BWs increased threefold. Growth performances and survival were not significantly affected by either ploidy or dietary l ‐carnitine content, although daily growth index showed an increasing trend (2.52–2.65% day^?1) with increasing dietary l ‐carnitine. Body l ‐carnitine content increased significantly with dietary l ‐carnitine content. Diploid fish had higher plasma ammonia (716–725 μmol L^?1) and osmolality (297–303 mOsm) levels than triploid trout (523–649 μmol L^?1 and 285–291 mOsm, respectively). l ‐carnitine, ploidy and their interaction showed to affect significantly the concentration of several fatty acids. Palmitoleic (16:1), oleic (18:1) and erucic (22:1) acids showed lower concentrations, while the eicosadienoic (20:2n‐6) and arachidonic (20:4n‐6) acids were elevated in liver of triploid fish. Eicosapentaenoic acid (22:5n‐3) was significantly higher in fish fed 200 mg than in fish fed 15 mg l ‐carnitine.     

Factors influencing growth of individual brown trout in three streams of the upper Midwestern United States

Growth rate variation of three age groups of brown trout, Salmo trutta L. (age‐0, 1 and 2, and 3+), was quantified from recaptured, individually tagged brown trout and related to season, stream reach, relative abundance, initial length and movement to examine factors influencing growth in length in three streams in the Midwestern United States. Total variation in growth was almost five times greater for age‐0 than for age‐3+ trout. Individual trout accounted for about 13% of total variation in age‐0 growth, season about 57%, and trout initial length and relative abundance combined another 2%. The 2006 age‐0 cohort had the fastest growth rates in their second spring and summer (2007) and slowest growth in their first winter (2006–2007). About 53% of total growth variation of age‐1 and age‐2 trout was accounted for by individual trout, season, initial length and stream reach. Predicted growth rates indicated strong effects of season and initial length. A significant interaction between these two factors indicated that, although smaller trout grew faster than larger trout, this length effect was most pronounced in spring and summer. About 35% of total growth variation of age‐3+ trout was accounted for by individual trout and season. Together, season and individual trout characteristics were identified as the most important factors influencing brown trout growth in these streams.     

Population density,growth and reproduction of arapaima in an Amazonian river‐floodplain

Arantes CC, Castello L, Stewart DJ, Cetra M, Queiroz HL. Population density, growth and reproduction of arapaima in an Amazonian river‐floodplain. Ecology of Freshwater Fish 2010: 19: 455–465. © 2010 John Wiley & Sons A/S Abstract – Compensatory density effects are key features of fish population dynamics that remain poorly understood in tropical river‐floodplains. We investigated possible compensatory growth and reproductive processes for a river‐floodplain population of Arapaima sp., an extinction‐prone fish species of South America. Body growth was studied through analysis of ring patterns on the scales, and size and age at sexual maturity was studied through analysis of female gonads. Growth and maturity were compared for unmanaged conditions with relatively low population density (in 1990s) versus managed conditions with markedly higher density (in 2005–2006); between 1999 and 2005–2006, abundance increased 7.3 fold. Results contradict theoretical expectations for slower growth and delayed reproduction at higher population density. Total lengths of arapaima at low population density were significantly shorter for age classes 1–5 compared with lengths of those age classes at high population density (ancova , P < 0.0001 for both slopes and intercepts). Total length at 50% maturity (L₅₀) only declined about 4% with increasing density (e.g., 164 cm at low density vs. 157 cm at high density). Apparent faster growth at high density and only a slight change in size at maturity resulted in fishes spawning at an earlier age with high density conditions (age 3 vs. age 4–5). We hypothesise that these patterns reflect compliance with minimum size limits of catch during the high density (managed) situation, where there was no harvest of immature fishes. Compliance with minimum size limits, thus, may have led to faster average body growth rate and earlier reproduction, which has greatly promoted population recovery.     

Detection of density‐dependent growth at two spatial scales in marble trout (Salmo marmoratus) populations

Vincenzi S, Crivelli AJ, Jesensek D, De Leo GA. Detection of density‐dependent growth at two spatial scales in marble trout (Salmo marmoratus) populations.
Ecology of Freshwater Fish 2010: 19: 338–347. © 2010 John Wiley & Sons A/S Abstract – Density‐dependent body growth has often been observed in freshwater salmonid populations. Several studies suggest this compensatory pattern as a potential mechanism of population regulation. The choice of the spatial scale is important for the detection of density‐dependent growth, as study areas need to be of the appropriate size to capture the density of conspecifics actually experienced by individuals over the preceding growth period. Here, we used four marble trout (Salmo marmoratus) populations (Gatsnik, Gorska, Huda and Zakojska) living in Slovenian stream to study the relationships between early density of marble trout and subsequent body growth. As streams are divided in sectors delimited by natural barriers that prevent or strongly limit movement of individuals, we tested the relationship between early density and body size through the lifetime at two spatial scales, that is, sector level (for Gatsnik and Zakojska) and whole stream level (the four populations were pooled). Sector length in Gatsnik and Zakojska ranged from 113 to 516 m. At both sector and whole stream level, temporal data were pooled. Growth declined significantly with increasing density both at the sector and whole stream levels, and the density‐dependent relationship was described by negative power curves. However, at the sector level the density‐dependent pattern was stronger in Gatsnik, a stream in which fish could move across sectors, than in Zakojska, where upstream movement across sectors is prevented by waterfalls.     

Early life history and recruitment of black crappie (Pomoxis nigromaculatus) in two South Dakota waters

Abstract— We compared the early life history of black crappie ( Pomoxis nigromaculatus ) in Richmond (an impoundment) and Brant (a natural lake) lakes during 1994-1996. We expected variable recruitment (i. e., missing year classes) in the natural lake and more consistent recruitment in the impoundment. Larval black crappie abundance was always higher in Richmond Lake than Brant Lake. Peak abundance of larval black crappie was highest during 1994 in both waters. However, peak larval abundance did not correspond with fall trap-net catch per unit effort (CPUE) of age-0 black crappie, which was highest during 1995. Thus, recruitment of black crappie was not simply a function of the number of larvae hatched. Similar trends in catches of age-0 black crappie with the ichthyoplankton trawl and trap nets for both water bodies during 1994-1996 suggest that broad environmental factors similarly affected reproduction and recruitment in Richmond and Brant lakes.     

Seasonal movement,growth and survival of brook trout in sympatry with brown trout in Midwestern US streams

Seasonal patterns in growth, survival and movement of brook trout Salvelinus fontinalis were monitored in two southeastern Minnesota streams divided into study reaches based on brown trout Salmo trutta abundance. We estimated survival and movement while testing for effects of stream reach and time using a multistrata Cormack–Jolly–Seber model in Program MARK. Multistrata models were analysed for three age groups (age‐0, age‐1 and age‐2+) to estimate apparent survival, capture probability and movement. Survival varied by time period, but not brown trout abundance and was lower during flood events. Age‐0 brook trout emigrated from reaches with low brown trout abundance, whereas adult brook trout emigrated from downstream brown trout‐dominated reaches. Growth was highest in spring and summer and did not differ across streams or reaches for the youngest age classes. For age‐2+ brook trout, however, growth was lower in reaches where brown trout were abundant. Interspecific interactions can be age or size dependent; our results show evidence for adult interactions, but not for age‐0. Our results suggest that brook trout can be limited by both environmental and brown trout interactions that can vary by season and life stage.     

Total population density during the first year of life as a major determinant of lifetime body‐length trajectory in marble trout

Abstract – The conditions experienced early in life can strongly influence life‐history trajectories in a variety of animal species. Here, we use data from four isolated populations of the endangered stream‐dwelling salmonid marble trout (Salmo marmoratus Cuvier 1817) living in the Soca and Idrijca river basins (Slovenia) to explore the influence of the total density experienced during and after the first year of life by marble trout year‐classes on body length of marble trout through the lifetime. Analyses were performed by pooling together the stream‐specific datasets to cover a wider range of densities. Mean body length of marble trout year‐classes through the lifetime (from age 1+ to 5+) was negatively related to total density of marble trout during the first year of life. The relationship between density during the first growth period and body length through the lifetime was well described by negative power curves. Total population density after the first year of life was not correlated with body length, thus suggesting that body growth trajectories are heavily determined early in life. Given size‐dependent sexual maturity and egg production in marble trout, the relationship between density early in life and lifetime individual growth may have strong implications in terms of population dynamics and regulation of population size.     

Variation in characteristics among gizzard shad populations: The role of impoundment size and productivity

Population characteristics of gizzard shad, Dorosoma cepedianum (Lesueur), an ecologically important fish species in Midwestern and southern USA impoundments, vary widely among water bodies. Impoundment productivity is known to influence population variables (e.g., recruitment, growth, mortality, size and age composition), but the role of impoundment morphometry (e.g., surface area, depth) is unknown. Differences in population characteristics of gizzard shad were compared between large and small impoundments across an impoundment–productivity gradient (indexed by total phosphorus [TP] concentration). Populations shifted from those comprised mostly of low abundances (indexed by catch per unit effort [CPUE], fish/hr of electric fishing) of long‐lived, large adults to those comprised of high abundances of short‐lived, small adults as TP increased. However, the trends in population variables across the TP gradient were less apparent in small impoundments than in large impoundments owing to considerable variation at a given TP level. Further analysis revealed that CPUE of gizzard shad was lowest in the smallest impoundments (<33 ha surface area) regardless of TP concentrations, probably because of more frequent winter kills. Overall, population characteristics were influenced by both density‐dependent effects and impoundment characteristics. Characteristics of gizzard shad were highly variable among populations, which have important consequences for ecosystem structure and function.     

Gustatory responses in Pacific bluefin tuna Thunnus orientalis (Temminck and Schlegel)

Gustatory neural responses of the Pacific bluefin tuna Thunnus orientalis (Temminck and Schlegel) to extracted compounds of prey organisms, such as amino acids, nucleotide‐related substances, organic acids and organic bases, were electrophysiologically recorded from the facial nerve supplying the anterior palate. Of the 17 amino acids tested, l ‐proline was the most potent amino acid at 10^?2 M, and its threshold was the lowest at around 10^?6 M. l ‐leucine, l ‐methionine, l ‐alanine, l ‐valine and l ‐isoleucine were also highly stimulatory at 10^?2 M; however, the other 11 amino acids examined were not as effective or were ineffective. Thus, the gustatory receptors for amino acids of the Pacific bluefin tuna show a narrowly tuned response profile. Among the seven nucleotide‐related substances tested, uridine‐5′‐monophosphate, inosine‐5′‐monophosphate and adenosine‐5′‐diphosphate were highly stimulatory, and their thresholds were 10^?4–10^?5 M. Inosine elicited a positive response at 10^?2 M but its response magnitude was not so high. Organic acids l ‐lactic and pyruvic acids were effective at 10^?2 M, but no response was elicited at 10^?3 M. Among organic bases, betaine was highly stimulatory, and its response magnitude at 10^?2 M is almost equal to that of l ‐proline at the same concentration. The threshold for betaine was determined to be at around 10^?5 M. Trimethylamine oxide and ammonium chloride were ineffective.     

Voluntary angler logbooks reveal long‐term changes in a lentic pike,Esox lucius,population

Sixty‐two years of voluntarily collected angling logbook data from a large natural Danish lake were used to study variation in pike, Esox lucius L., CPUE (catch per unit effort), expressed as no. of captured pike per boat trip, as an index of stock size. Pike CPUE was positively related to pike release rate by anglers and negatively affected by certain commercial fishers. The stocking of young‐of‐the‐year pike and a fishery‐dependent index of perch, Perca fluviatilis L., abundance (which may be pike prey or predator depending on size) did not correlate with pike CPUE. Analyses of the size distribution of pike, based on sizes of annual record trophy pike captured by anglers, confirmed the negative impact of commercial pike fishing and revealed a positive influence of air temperature. It is concluded that high‐quality angler logbooks that record effort and catch can be a cost‐effective tool to inform lake fisheries management by revealing long‐term population trends. Further, state space modelling, a statistical technique not yet seen in recreational fisheries science, is recommended as a tool to model proxies for population dynamics from angler logbook data.     

Long‐term growth patterns in a pond‐dwelling population of crucian carp,Carassius carassius: environmental and density‐related factors

Abstract Scale samples from crucian carp, Carassius carassius (L.), collected over a 10‐year period from a population in an ornamental pond were used to examine patterns in growth as a function of environmental factors, including water temperatures. Back‐calculated standard lengths (SL) at age differed between year classes in most cases. Annual SL increments were related to temperature and age using a non‐linear growth model. Growth declined with increasing age, whereas annual SL increments increased with increasing water temperature. The best‐fit model was with the total number of summer days when air temperature exceeded 20 °C (using water temperature equivalents of air temperature). A growth model including water temperature, age, year class, relative condition and rainfall was a better fit than other models. Year‐class strength was positively correlated with water degree‐days, and year‐class strength negatively affected annual SL increments. The results indicate that within a strong year class of crucian carp, the growth of individual fish is reduced compared with weak year classes, suggesting that density negatively affects growth in ponds where resources are limited.     

Biotic and abiotic regulation of a low‐density stream‐dwelling brown trout (Salmo trutta L.) population: effects on juvenile survival and growth

The effects of biotic (density‐dependent) and environmental (flow and temperature) factors on the apparent survival, mean length and size variation of a low‐density brown trout population in the juvenile stage, that is, from their first summer (0+) to the end of the second year (1+), were determined. Apparent survival was negatively related to the age class density during the three periods (first summer, first winter and second summer). A significant interaction between the mean flow and 0+ density highlighted a gradient towards strong density dependence acting on fish loss (i.e., mortality or migration) with decreasing summer flow. Conversely, no density dependence was reported at higher mean flows. The mean length was determined by density‐dependent and density‐independent (temperature and flow) factors throughout the study period. The negative relationship between fish length and intracohort density was highly significant during the three periods. The yearling (1+) density was negatively related to 0+ fish length measured after the first summer, suggesting intercohort effects. A positive effect of temperature on fish length was observed. Mean length after the summer seasons (0+ and 1+ fish) was also positively related to mean flow. Fish size variation around the mean measured with the coefficient of variation (CV) increased with increasing 0+ densities, both at the end of the first summer and the first winter. Results suggested that density‐dependent and density‐independent factors acted jointly on apparent survival and growth with a predominance of biotic processes. We discussed the potential implications of density‐dependent regulations on growth and survival for population resilience after catastrophic events.