Knowledge of environments used during early life history and movement patterns of Bighead Carp (Hypophthalmichthys nobilis) and Silver Carp (H. molitrix), collectively termed bigheaded carps, in the Upper Mississippi River (UMR) would be valuable for informing control measures to limit further population expansion and impacts of these species. Lock and Dam 19 (LD19) is a high-head dam on the UMR that delineates downriver areas where bigheaded carps are well established from upriver pools where these species are less abundant and evidence of reproduction and recruitment are limited. Principal natal environments supporting recruitment of emerging bigheaded carp populations in the UMR are unknown. The objectives of this study were to (1) infer environments occupied during early-life stages by bigheaded carps collected in UMR Pools 19-21 during 2013-2014 using otolith microchemistry and stable isotope analyses, and (2) use early-life environment assignments and capture location to identify individuals that passed through LD19. Differences in multivariate water chemistry signatures (Sr:Ca, Ba:Ca and δ18O) among the UMR, its tributaries, and the Missouri and Middle Mississippi rivers enabled development of a classification model for inferring early-life environment of bigheaded carps. Multiple sources of recruits, including from tributaries, have contributed to upriver expansion of bigheaded carps in the UMR. Sustainable control of bigheaded carps upstream of LD19 will likely require efforts to control local recruitment and immigration from downriver. The frequency of bigheaded carps collected in Pool 19 that were downstream of LD19 during early life suggests that bigheaded carps upstream of LD19 still predominantly consisted of immigrants from downriver during 2013-2014. Otolith chemistry provides an approach for assessing the extent to which changes in abundance of bigheaded carps upstream of LD19 are associated with local recruitment or immigration from downriver.

Shovelnose sturgeon Scaphirhynchus platorynchus in the middle Mississippi River provide one of the last commercially viable sturgeon fisheries in the world, yet their maturation and reproduction have not been linked. During 2005 and 2006, we sampled adult and age‐0 shovelnose sturgeon to link age at maturation, the timing and periodicity of spawning, age‐0 sturgeon production, and the resulting age‐0 growth rates. Age at maturity was later than previous estimates, the minimum age of first maturation being 8 years for males and 9 years for females. Total egg count was slightly lower than previously reported (mean = 29,573 per female; SE = 2,472). Males and females typically spawned every 2 and 3 years, respectively. Peaks in mature fish coincided with rising river stages and water temperatures at which shovelnose sturgeon probably spawn. Peaks in spent adults followed. Age‐0 shovelnose sturgeon occurred during June and July 2005 and May and June 2006, confirming successful spawning. Age‐0 sturgeon grew between 0.69 and 1.69 mm total length/d; four distinct weekly cohorts occurred each year. During fall 2006, females contained ripe eggs, males were milting, and a single age‐0 sturgeon (total length = 55 mm) was captured, suggesting that shovelnose sturgeon spawn during fall as well as spring. Management must consider the protracted nature of spawning within seasons as well as differences in spawning activity between seasons.

Climatic variation and dispersal are two primary factors thought to induce recruitment synchrony in fish populations. We hypothesized that climate factors correlated across a broad geographical scale (i.e., the Moran effect) would induce synchrony in recruitment for common carp Cyprinus carpio among 18 glacial lakes across a 175‐km2 area in eastern South Dakota. Cross‐correlation analysis indicated that common carp population fluctuations were highly synchronous among lakes. To evaluate the influence of the Moran effect on recruitment, we examined several candidate models using an information‐theoretic approach. The model with the most support included the interaction of temperature, precipitation, and wind during the open‐water period. This model indicated that the effects of any one of these climate variables on recruitment strength depended on the level of each of the other variables in any given year. Our results suggest that common carp populations in the Midwestern United States exhibit synchronous recruitment across regionwide geographic areas as a result of climatic variability.

Habitat use by wild age‐0 shovelnose sturgeon Scaphirhynchus platorynchus and pallid sturgeon S. albus was quantified by trawling macrohabitats (i.e., main channel, main‐channel border, island, and artificial structures [e.g., wing dams]) in the middle Mississippi River during 1998–2007 (1,702 trawls; n = 1,507 age‐0 sturgeon captured). Age‐0 sturgeon catch rates were highest around artificial structures and island areas, while main‐channel habitat provided the lowest catch rates. Moreover, size‐selective macrohabitat analyses indicated that small age‐0 sturgeon (i.e., majority < 50 mm total length) were located in channel‐border dike and island side‐channel macrohabitats, while all other macrohabitats were occupied by small and large age‐0 sturgeon. Furthermore, our analyses indicated that age‐0 sturgeon mesohabitat use within macrohabitats was influenced by depth, substrate, and bottom velocity. Low velocity (i.e., ∼0.1 m/s), moderate depths (i.e., 2–5 m), and sand substrate were positively related to age‐0 sturgeon relative abundance. As such, instream habitat modifications that provide the correct combination of macrohabitats with suitable mesohabitats may hold high densities of age‐0 shovelnose sturgeon and pallid sturgeon and may improve recruitment success.

Otoliths (asteriscus) have been validated as an accurate structure for estimating age of common carp Cyprinus carpio. However, extraction and processing of common carp otoliths are time consuming and require sacrifice of fish. Therefore, we analyzed age estimation precision of four alternative structures relative to otolith age for 139 common carp collected from five eastern South Dakota lakes. All common carp were collected using daytime electrofishing. Each fish was assigned an identification number and measured to the nearest millimeter total length, after which aging structures were removed. Age was estimated from scales, vertebrae, opercles, pectoral fin rays, and asteriscus otoliths by methods similar to those recommended by previous researchers. Relative to otolith age, average percent error was 6.8% for scales, 15.4% for vertebrae, 9.9% for opercles, and 1.2% for pectoral fin rays. Compared with all other structures, ages from pectoral fin ray sections were nearly as precise as otoliths through age 13 (lowest average percent error); however, fin rays consistently underestimated the ages of fish older than 13 years. In most cases, pectoral fin ray ages matched otolith ages, thereby providing similar age estimates. We conclude that pectoral fin rays provide a precise, economical, and nonlethal alternative for estimating common carp age structure. Accuracy of common carp ages estimated from pectoral fin rays still requires evaluation.

Natural resource professionals have frequently criticized universities for poorly preparing graduates to succeed in their jobs. We surveyed members of the American Fisheries Society to determine which job skills and knowledge of academic topics employers, students, and university faculty members deemed most important to early‐career success of fisheries professionals. Respondents also rated proficiency of recently hired, entry‐level professionals (employers) on how well their programs prepared them for career success (students and faculty) in those same job skills and academic topics. Critical thinking and written and oral communication skills topped the list of important skills and academic topics. Employers perceived recent entry‐level hires to be less well‐prepared to succeed in their careers than either university faculty or students. Entry‐level hires with post‐graduate degrees rated higher in proficiency for highly important skills and knowledge than those with bachelor's degrees. We conclude that although universities have the primary responsibility for developing critical thinking and basic communication skills of students, employers have equal or greater responsibility for enhancing skills of employees in teamwork, field techniques, and communicating with stakeholders. The American Fisheries Society can significantly contribute to the preparation of young fisheries professionals by providing opportunities for continuing education and networking with peers at professional conferences.

No abstract

The main stems of large rivers throughout the world have been highly modified with little consideration for effects on fishes that rely on these areas to complete their life histories. Particularly important is the ability of riverine habitats to provide foraging opportunities for young fish. We explored how temperature, flow, and food availability influenced diet content, prey selection (Strauss's linear selectivity index), and energy condition of age-0 shovelnose sturgeon Scaphirhynchus platorynchus and pallid sturgeon S. albus in major habitat areas (e.g., islands, channel borders, wing dikes, and side channels) of the middle Mississippi River during spring (March-May) and summer (June-August) 2008. Standardized diet mass (dry mass standardized for fish body mass) of the age-0 sturgeon peaked at about 19 • C and at a flow velocity of 0.5 m/s. Although potential prey taxa were diverse, the diets for age-0 sturgeon of all sizes were dominated by mayflies (Ephemeroptera) and midge larvae (Chironomidae) across all habitats. As age-0 sturgeon grew, the relative energy return per habitat appeared to diverge; island tips upstream of the main channel and channel border areas behind wing dikes provided higher gains in standardized diet mass than other habitats. No differences in energy condition (kJ/g) occurred among habitats, although large (51-200 mm total length [TL]) age-0 sturgeon had higher energy densities than their small (≤50 mm TL) counterparts. Enhancement of areas with flow and substrates that facilitate the production and availability of midges and mayflies (e.g., instream island complexes) is critical for the recruitment of age-0 Scaphirhynchus sturgeon in large rivers.