Few studies have quantified the repeatability of reproductive decisions by individuals or assessed their relationship with environmental variables over multiple seasons for long-lived iteroparous fish species. Using individual-based data collected for 678 lake sturgeon ( Acipenser fulvescens ) over 8 consecutive years, we evaluated hypotheses regarding spawning periodicity and repeatability of spawning location, spawning time, and environmental cues associated with spawning. At our study site (Upper Black River, northern Michigan, USA), interspawning interval differed between males (2.3 ± 0.08 years) and females (3.7 ± 0.16 years), but was not significantly related to age. Individual spawning behavior was highly repeatable with respect to spawning time (relative day within the spawning season) for both sexes regardless of size or age, but was less repeatable, though still significant, relative to water temperature, river discharge, and lunar phase. Breeding area was also repeatable, with individuals spawning earlier in the season selecting locations further upstream than those spawning later. Repeatability in spawning times and locations suggest that subpopulation differentiation may develop among different spawning groups, even within small and spatially contiguous areas.

The associations were quantified between daily and interannual variation in the timing of a closed population of lake sturgeon Acipenser fulvescens migration and arrival at spawning sites with stream environmental and lunar covariates. Spawning data were gathered from 1262 fish in Black Lake, Michigan 2001 to 2008 and by video monitoring 2000 to 2002. Sex‐specific variation in responses to external cues was also tested. Results showed that a greater number of individuals initiated migration from lake to riverine habitats at dawn and dusk relative to other times of the day. Current and lagged effects of water temperature and river discharge, and periods in the lunar cycle were important variables in models quantifying movements into the river and timing of adult arrival at spawning sites. Different suites of covariates were predictive of A. fulverscens responses during different periods of the spawning season. The timing of initiation of migration and spawning, and the importance of covariates to the timing of these events, did not differ between sexes. Stream flow and temperature covaried with other variables including day length and the lunar cycle. Anthropogenic disruption of relationships among variables may mean that environmental cues may no longer reliably convey information for Acipenseriformes and other migratory fishes.

Quantifying interannual variation in effective adult breeding number (N(b)) and relationships between N(b), effective population size (N(e)), adult census size (N) and population demographic characteristics are important to predict genetic changes in populations of conservation concern. Such relationships are rarely available for long-lived iteroparous species like lake sturgeon (Acipenser fulvescens). We estimated annual N(b) and generational N(e) using genotypes from 12 microsatellite loci for lake sturgeon adults (n = 796) captured during ten spawning seasons and offspring (n = 3925) collected during larval dispersal in a closed population over 8 years. Inbreeding and variance N(b) estimated using mean and variance in individual reproductive success derived from genetically identified parentage and using linkage disequilibrium (LD) were similar within and among years (interannual range of N(b) across estimators: 41-205). Variance in reproductive success and unequal sex ratios reduced N(b) relative to N on average 36.8% and 16.3%, respectively. Interannual variation in N(b)/N ratios (0.27-0.86) resulted from stable N and low standardized variance in reproductive success due to high proportions of adults breeding and the species' polygamous mating system, despite a 40-fold difference in annual larval production across years (437-16 417). Results indicated environmental conditions and features of the species' reproductive ecology interact to affect demographic parameters and N(b)/N. Estimates of N(e) based on three single-sample estimators, including LD, approximate Bayesian computation and sibship assignment, were similar to annual estimates of N(b). Findings have important implications concerning applications of genetic monitoring in conservation planning for lake sturgeon and other species with similar life histories and mating systems.

For migratory fish like lake sturgeon (Acipenser fulvescens), the period from egg deposition through embryonic and larval development until dispersal (ELDTUD) contributes substantially to variation in survival at the individual level and to population levels of recruitment. Using genetically determined parentage, we examined the relative importance of environmental variables in a stream environment (e.g., temperature and discharge) and maternal effects (including individual female body size, spawning time, and location) to ELDTUD on an individual basis. Adult lake sturgeon (n = 208) spawning in the Upper Black River (Michigan, USA), and larvae (n = 1444) dispersing downstream were captured during the 2007 spawning season. We used generalized mixed models and multimodel inference based on Kullback-Leibler informationtheoretic criteria to demonstrate that environmental variables and the maternal effects of individual female and spawning time were both important predictors of ELDTUD. Decreasing ELDTUD during the season resulted from linearly increasing temperature and nonlinearly decreasing river discharge. Spawning time and individual female explained a large proportion of variation in ELDTUD. The individual-based approach used in this study provided precise estimates of ELDTUD and also facilitated the partitioning of variation in ELDTUD of larvae produced by the same female and among females spawning at different times and different environmental conditions. Résumé : Chez les poissons migrateurs comme l'esturgeon jaune (Acipenser fulvescens), la période qui commence à la ponte des oeufs, comprend les développements embryonnaire et larvaire et s'étend jusqu'à la dispersion (ELDTUD) contribue considérablement à la variation de la survie pendant toute la vie au niveau individuel et au recrutement au niveau de la population. Nous examinons l'importance relative des variables environnementales des cours d'eau (par ex., température et dé-bit) et des effets maternels, en particulier la taille corporelle, le moment de la fraie et la position dans le milieu, sur l'ELDTUD chez des individus dont l'ascendance a été déterminée par des méthodes génétiques. Pendant la saison de reproduction de 2007, nous avons capturé des esturgeons jaunes adultes (n = 208) frayant dans l'Upper Black River (Michigan, É.-U.), ainsi que des larves (n = 1444) qui se dispersaient vers l'aval. Des modèles mixtes généralisés et l'inférence multimodèle basée sur les critères de Kullback-Leibler fondés sur la théorie de l'information nous ont permis de démontrer que tant les variables du milieu que les effets maternels reliés à la femelle et le moment de la fraie sont de bonnes variables pré-dictives d'ELDTUD. La diminution de l'ELDTUD au cours de la saison s'explique par un accroissement linéaire de la température et d'une réduction non linéaire du débit de la rivière. Le moment de la fraie et les femelles individuelles expliquent une forte proportion de la variation de l'ELDTUD. L'approche basée sur l'individu utilisée dans notre étude fournit des es...

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Considerable uncertainty exists over the relative merits of alternative supplementation strategies for lake sturgeon, Acipenser fulvescens Rafinesque. Numerous supplementation prescriptions have been advocated, largely in the absence of data, focusing on perceived impacts of levels of genetic diversity of progeny collected using different collection methods, and probabilities of survival relative to the size or age of fish released. The hypothesis that collection method, hatchery rearing environment and size/age at the time of release do not influence survival and movements was tested. Acipenser fulvescens gametes and juveniles were collected using three methods and reared in a stream-side hatchery along the natal stream and in a traditional non-natal hatchery environment. Acipenser fulvescens were released into the Upper Black River, Michigan at 8, 13, and 17 weeks of age. Higher rates of recapture were found for juvenile sturgeon reared in the stream-side hatchery than the traditional hatchery for the releases at 8 and 13 weeks. Recapture rates and dispersal distances were significantly greater for fish stocked at 17 weeks than for fish released at earlier ages. Large body size was negatively correlated with timing of movements across all ages indicating that survival may be enhanced by releasing individuals at night. Results indicate that supplementation protocols for A. fulvescens should be developed on a system specific basis and demonstrate the importance of hatchery-rearing environment when fish of younger ages are released. K E Y W O R D S :Acipenser fulvescens, collection methods, dispersal, supplementation.

The majority of large North American rivers are fragmented by dams that interrupt migrations of wide‐ranging fishes like sturgeons. Reconnecting habitat is viewed as an important means of protecting sturgeon species in U.S. rivers because these species have lost between 5% and 60% of their historical ranges. Unfortunately, facilities designed to pass other fishes have rarely worked well for sturgeons. The most successful passage facilities were sized appropriately for sturgeons and accommodated bottom‐oriented species. For upstream passage, facilities with large entrances, full‐depth guidance systems, large lifts, or wide fishways without obstructions or tight turns worked well. However, facilitating upstream migration is only half the battle. Broader recovery for linked sturgeon populations requires safe “round‐trip” passage involving multiple dams. The most successful downstream passage facilities included nature‐like fishways, large canal bypasses, and bottom‐draw sluice gates. We outline an adaptive approach to implementing passage that begins with temporary programs and structures and monitors success both at the scale of individual fish at individual dams and the scale of metapopulations in a river basin. The challenge will be to learn from past efforts and reconnect North American sturgeon populations in a way that promotes range expansion and facilitates population recovery.

Homosexual pairing between males occurs under natural conditions in a wide variety of taxa, including many insect species, but few studies have investigated