Detecting all species in a given survey is challenging, regardless of sampling effort. This issue, more commonly known as imperfect detection, can have negative impacts on data quality and interpretation, most notably leading to false absences for rare or difficult‐to‐detect species. It is important that this issue be addressed, as estimates of species richness are critical to many areas of ecological research and management. In this study, we set out to determine the impacts of imperfect detection, and decisions about thresholds for inclusion in occupancy, on estimates of species richness and community structure. We collected data from a stream fish assemblage in Algonquin Provincial Park to be used as a representation of ecological communities. We then used multispecies occupancy modeling to estimate species‐specific occurrence probabilities while accounting for imperfect detection, thus creating a more informed dataset. This dataset was then compared to the original to see where differences occurred. In our analyses, we demonstrated that imperfect detection can lead to large changes in estimates of species richness at the site level and summarized differences in the community structure and sampling locations, represented through correspondence analyses.

A major strength of the guild approach is its ability to simplify community analysis by aggregating species with similar roles or functions into groups. These groups can be used to study a number of important ecological concepts, including functional diversity, community response to disturbance, and food-web dynamics. Despite increased use, guild membership can be based on subjective criteria that are arbitrarily chosen, leading to inconsistencies across studies. Additionally, studies using the guild approach generally ignore ontogenetic changes in diet and habitat use and therefore, do not fully capture the complexity of aquatic communities. Although these issues have been discussed in the literature, much has changed since the last review was published a decade ago. In our examination, we discuss data requirements and consequences of data availability and reliability on guild formation. We identify bootstrapping and permutation techniques developed to address limitations through cluster validation and the identification of ontogenetic shifts prior to guild delineation. Lastly, we provide a step-by-step guide to guild analysis, accompanied by a decision tree, to facilitate objective and informed guild creation.

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Inland fisheries have a significant cultural and economic value around the globe, providing dietary protein, income, and recreation. Consequently, methods for monitoring and managing these important fisheries are continually being refined. In marine systems, multispecies size spectrum models have been increasingly used to explore management scenarios of important fish stocks within an ecosystem‐based fisheries management framework; however, these models have not been applied as extensively in freshwater systems. In this study, we developed a multispecies size spectrum model for the fish community of Lake Nipissing, a large, productive lake in Ontario, Canada. To the best of our knowledge, this is the first fully calibrated multispecies size spectrum model for an inland fishery. Using this model, we explored the impacts of potential fishing regimes and management scenarios on fish community dynamics while taking species interactions into account. Specifically, we examined how changes in fishing mortality affect (1) species biomass, (2) community size structure, and (3) stock recovery times. We found that community dynamics following changes in fishing mortality were driven by complex interactions among species, including competition and predation. The greatest changes in biomass and community size structure were observed following changes in fishing mortality of top predators, with community size structure most strongly influenced by changes in the mortality of the largest species. Counter to predictions based on generation time, the smallest species in our model exhibited the longest time to recovery due to strong competition and predation. Our results demonstrate the importance of considering species interactions in the management of inland fisheries and highlight the potential of size spectrum model use in freshwater systems.

For ectotherms such as fishes, survival and fitness are strongly dependent on the temperature of their environment (Fry, 1947;Magnuson et al., 1979). Like any other resource, habitats with suitable temperature can be the subject of competition as organisms seek to maximize time spent near their thermal optima (Magnuson et al., 1979). As a result, the distribution of ectothermic organisms is often strongly driven by thermal characteristics of their environments (Attrill & Power, 2004;Hughes & Grand, 2000). A prime example of this phenomenon can be seen in stratified lakes. In the summer months, many temperate lakes undergo thermal stratification, with warmer waters found in the epilimnion and colder waters remaining below the metalimnion, or thermocline (Wetzel, 2001).