We conducted in situ testing of strobe lights as a potential fish deterrent by examining avoidance and acclimation behaviors of rainbow smelt Osmerus mordax in Lake Oahe, South Dakota. Split‐beam hydroacoustics were used to assess the effectiveness of the deterrent system by comparing proximal densities of rainbow smelt before and after the device was activated. In summer 2005, strobe lights successfully repelled rainbow smelt to a minimum horizontal distance of 21 m at both 1 h and 4 h postactivation; the model AGL‐FH 920 flashhead produced a light intensity of 6,585 lumens per flash. Similarly in 2004, a model AGL‐FH 901 flashhead, which produced a light intensity of 2,634 lumens per flash, repelled rainbow smelt to a horizontal distance of 15 m. A comparison of strata 10 m above and below the strobe light system showed that rainbow smelt were vertically displaced to approximately 6 m. We conclude that strobe lights elicit behavioral avoidance by rainbow smelt and may provide an effective means for reducing entrainment losses through Oahe Dam.

Long-lived species from marine and freshwater environments have experienced declines linked to anthropogenic effects such as overexploitation, dam construction, and habitat modification. An understanding of the age structure and the associated dynamics determined from these data for long-lived species is critical for both perseverance of at-risk species and maintenance of exploited species. We used pallid sturgeon (Scaphirhynchus albus) to evaluate the efficacy of mark–recapture data from known-age, hatchery-reared fish (ages 1 to 7) to corroborate age and growth estimates obtained from sectioned pectoral fin rays. Accuracy of age estimates from known-age fish was 13%, whereas 72% of estimates were within 2 years of the true age. Annual growth was significantly different between estimated growth (back-calculated) and actual observations of tagged pallid sturgeon. Age for pallid sturgeon of any given size was estimated with parameters derived from mark–recapture data, and the predicted length-at-age relation was similar to observations from known individuals. In instances where age determination for all ages of interest cannot be verified, mark–recapture appears to be a viable solution for examining growth and has shown promise as a tool for estimating ages in long-lived species with calcified structures that are difficult to read.

Capture–recapture methods are commonly used to estimate population parameters when the necessary assumptions are met. One of the broadest assumptions of capture–recapture models is that tags are not lost. Therefore, one must understand tag retention to be able to adjust estimates if tag loss occurs. Our objectives were to (1) determine retention rates of T‐bar anchor tags and passive integrated transponder (PIT) tags injected into the dorsal musculature of shovelnose sturgeon Scaphirhynchus platorynchus and (2) determine whether using an alternative PIT‐tagging location (the operculum) and a new tagging procedure (cyanoacrylate [i.e., superglue] to seal the tag insertion point) provided higher retention. The T‐bar tags had a retention rate of 100%; PIT tag retention, however, was more variable. Injection of PIT tags along the dorsal fin resulted in a retention rate of 73%, and tag loss was observed throughout the 98‐d experiment. The application of cyanoacrylate did not appear to deter PIT tag loss; retention rates before and after cyanoacrylate was applied were 73% and 77%, respectively. Further, we observed a similar trend of continual PIT tag loss throughout the experiment. The operculum location resulted in a 92% PIT tag retention rate and showed no trend in cumulative loss through time. The high retention rate of PIT tags placed in the operculum suggests that this location is a reliable alternative to inserting PIT tags along the dorsal fin of adult Scaphirhynchus species. In addition, the excellent retention of T‐bar tags makes them a viable option for use in Scaphirhynchus studies. Received October 8, 2011; accepted March 1, 2012

Goto, Daisuke; Hamel, Martin J.; Hammen, Jeremy J.; Rugg, Mathew L.; Pegg, Mark A.; and Forbes, Valery E., "Spatiotemporal variation in flow-dependent recruitment of long-lived riverine fish: Model development and evaluation" (2014). Faculty Publications in the Biological Sciences. 369.

We used mark-recapture data from shovelnose sturgeon (Scaphirhynchus platorynchus) to describe range-wide growth characteristics and developed a model to estimate ages. Data were solicited throughout much of the current distribution of shovelnose sturgeon, specifically from the mainstem Missouri and Mississippi rivers and their tributaries. Shovelnose sturgeon exhibited variable growth among locations; however, adult fish exhibited almost no growth after they reached a particular size, presumably the size at sexual maturity. Shovelnose sturgeon from the Mississippi River basin attained greater maximum sizes and ages compared with the Missouri River basin. However, two populations from the Mississippi River that received high exploitation from commercial harvest had truncated age distributions with smaller asymptotic lengths. Lower Missouri River populations were characteristic of exploited populations (i.e., smaller fish and reduced longevity), presumably a result of anthropogenic effects. Wide discrepancies in maximum age and size suggest shovelnose sturgeon are capable of displaying phenotypic plasticity in response to exploitation or environmental influences. Determining metapopulation dynamics is a priority because it is unknown how population connectivity may influence dynamic rate functions and persistence of large-river fishes. Identifying potential source-sink connections in terms of population dynamics may provide a template for direction of future restoration and recovery efforts.Résumé : Nous avons utilisé des données de marquage-recapture d'esturgeons scaphirhynques (Scaphirhynchus platorynchus) pour en décrire les caractéristiques de croissance sur l'ensemble de leur aire de répartition et élaborer un modèle pour estimer les âges. Des données ont été sollicitées dans la majeure partie de l'aire de répartition actuelle de l'espèce, plus précisément des bras principaux de la rivière Missouri et du fleuve Mississippi et leurs affluents. Si la croissance des esturgeons scaphirhynques varie selon la localité, les poissons adultes ne présentent presque aucune croissance après avoir atteint une taille donnée, vraisemblablement leur taille à maturité sexuelle. Les esturgeons scaphirhynques du bassin du Mississippi atteignent des tailles et des âges maximums supérieurs à ceux du bassin de la rivière Missouri. Cependant, deux populations du Mississippi faisant l'objet d'une forte exploitation commerciale présentent des distributions d'âges tronquées et des longueurs asymptotiques plus faibles. Les populations du cours inférieur de la rivière Missouri sont caractéristiques des populations exploitées (c.-à -d. poissons plus petits de longévité réduite), vraisemblablement le résultat d'effets d'origine humaine. De grandes divergences sur le plan de l'âge et de la taille maximums donnent à penser que les esturgeons scaphirhynques peuvent faire preuve de plasticité phénotypique en réaction à l'exploitation ou à des influences environnementales. La détermination de la dynamique des métapopulations constitue une prio...