Kokanee Oncorhynchus nerka provide valued recreational fisheries and also serve as a prey resource for economically, socially, and ecologically important fishes. As such, management of kokanee is a major focus of natural resource agencies. Kokanee are typically monitored using midwater trawls, but the interpretation of data collected using midwater trawls is difficult due to the unknown size selectivity of the gear. We sought to assess the length selectivity of midwater trawls by comparing estimates obtained from midwater trawls with estimates obtained from gill nets adjusted for size selectivity. Experimental curtain gill nets and midwater trawls were used in conjunction to sample kokanee in seven lentic systems in Idaho. The size selectivity of gill nets was estimated by accounting for the probability of encounter and the probability of retention. Estimates of size selectivity were then used to adjust the length distribution of fish sampled in gill nets. The adjusted length distribution of fish sampled in gill nets was compared with estimates obtained from midwater trawls to identify potential size selectivity of midwater trawls. A pattern of size selectivity was apparent for both sampling techniques. The average length of kokanee sampled with midwater trawls was 111 mm; whereas, kokanee sampled with gill nets had a mean length of 235 mm. Our results suggest experimental gill nets are useful for common sampling of kokanee (e.g., trend monitoring) because the gear is less size selective than midwater trawls and is adjustable for size selectivity. However, midwater trawls are likely the best gear for addressing questions associated with early life history. Overall, our results provide a better understanding of gill-net and midwater trawl selectivity and ultimately improve the ability to sample and manage the species.

Burbot Lota lota were illegally introduced into the Green River, Wyoming, drainage and have since proliferated throughout the system. Burbot in the Green River pose a threat to native species and to socially, economically, and ecologically important recreational fisheries. Therefore, managers of the Green River are interested in implementing a suppression program for Burbot. We collected demographic data on Burbot in the Green River (summer and autumn 2013) and used the information to construct an age‐based population model (female‐based Leslie matrix) to simulate the population‐level response of Burbot to the selective removal of different age‐classes. Burbot in the Green River grew faster, matured at relatively young ages, and were highly fecund compared with other Burbot populations within the species’ native distribution. The age‐structured population model, in conjunction with demographic information, indicated that the Burbot population in the Green River could be expected to increase under current conditions. The model also indicated that the Burbot population in the Green River would decline once total annual mortality reached 58%. The population growth of Burbot in the Green River was most sensitive to age‐0 and age‐1 mortality. The age‐structured population model indicated that an increase in mortality, particularly for younger age‐classes, would result in the effective suppression of the Burbot population in the Green River. Received May 27, 2015; accepted March 20, 2016 Published online August 24, 2016

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Commercial harvest is often considered as a primary cause of fish population declines in marine and inland systems throughout the world. However, much of the data supporting the negative attributes of commercial harvest are derived from marine fisheries and may not be directly applicable to inland fisheries. In this study, over 60 years of commercial fishery data from the Upper Mississippi River (UMR) was synthesized to better understand how inland commercial fisheries function and to address concerns associated with the exploitation of aquatic resources in freshwater systems. Overall, total commercial harvest in the UMR remained relatively stable over the study period and did not negatively influence fish populations or recreational fisheries. Our results address concerns associated with inland fisheries and highlight how proper management and interagency partnerships result in consistent and productive fisheries over large spatial and temporal scales.