Signal from the noise: model‐based interpretation of variable correspondence between active and passive samplers

Combining information from active and passive sampling of mobile animals is challenging because active‐sampling data are affected by limited detection of rare or sparse taxa, while passive‐sampling data reflect both density and movement. We propose that a model‐based analysis allows information to be combined between these methods to interpret variation in the relationship between active estimates of density and passive measurements of catch per unit effort to yield novel information on activity rates (distance/time). We illustrate where discrepancies arise between active and passive methods and demonstrate the model‐based approach with seasonal surveys of fish assemblages in the Florida Everglades, where data are derived from concurrent sampling with throw traps, an enclosure‐type sampler producing point estimates of density, and drift fences with unbaited minnow traps that measure catch per unit effort (CPUE). We compared incidence patterns generated by active and passive sampling, used hierarchical Bayesian modeling to quantify the detection ability of each method, characterized interspecific and seasonal variation in the relationship between density and passively measured CPUE, and used a predator encounter‐rate model to convert variable CPUE–density relationships into ecological information on activity rates. Activity rate information was used to compare interspecific responses to seasonal hydrology and to quantify spatial variation in non‐native fish activity. Drift fences had higher detection probabilities for rare and sparse species than throw traps, causing discrepancies in the estimated spatial distribution of non‐native species from passively measured CPUE and actively measured density. Detection probability of the passive sampler, but not the active sampler, varied seasonally with changes in water depth. The relationship between CPUE and density was sensitive to fluctuating depth, with most species not having a proportional relationship between CPUE and density until seasonal declines in depth. Activity rate estimates revealed interspecific differences in response to declining depths and identified locations and species with high rates of activity. We propose that variation in catchability from methods that passively measure CPUE can be sources of ecological information on activity. We also suggest that model‐based combining of data types could be a productive approach for analyzing correspondence of incidence and abundance patterns in other applications

Factors Influencing Largemouth Bass Recruitment: Implications for the Illinois Management and Stocking Program

Annual Progress Report issued August 2002; NOTE: Two different reports numbered 02/06 were issued from the CAE.Report issued on: August 2002INHS Technical Report prepared for Division of Fisheries Illinois Department of Natural Resource

Role of Parental Care and Ontogenetic Diets Shifts in the Recruitment Variation of an Aquatic Predator

118 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008.Recruitment is a highly variable process crucial for the persistence of wild fish populations and the sustainability of fisheries. Based on previous studies, nest success, ontogeny of piscivory, and winter survival are predicted to determine year class strength of largemouth bass Micropterus salmoides . In Chapter Two, family-specific DNA fingerprints were used to quantify parental effects on brood-specific contribution to fall recruitment in environments that differed in the presence of bluegill sunfish Lepomis macrochirus , an important brood predator. Overall, the majority of fall recruits originated from the broods of larger, older males that spawned earliest and had higher mating success than other males. The presence of bluegill sunfish caused size-specific variation in duration of parental care, with parental protection that extended to the free-swimming life stages of offspring needed for any brood-specific contribution to recruitment. Chapter Three examined the relative importance of zooplankton prey versus fish prey to recruitment to age 1 in wild populations of largemouth bass. Variation in ontogenetic diet shift to piscivory and availability of bluegill sunfish as prey for age 0 largemouth bass had a stronger relationship with inter-lake variation in recruitment to age 1 than variable abundance of zooplankton. In Chapter Four, the relative importance of early reproductive success, prey availability, and winter survival to recruitment to age 1 was assessed simultaneously in a multiple-lake and ---year data set. Both among and within lakes, production of age 0 largemouth bass from the parental care stage and availability of prey fish were found to be important to recruitment. Inter-system differences in recruitment strength were set prior to winter. Annual fluctuations in prey fish abundance only influenced recruitment in lakes where reproductive output of bluegill sunfish was generally low. These studies further our understanding of recruitment variation, by quantifying the influence of multiple processes operating during early life stages.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Factors Influencing Largemouth Bass Recruitment: Implications for the Illinois Management and Stocking Program

Report issued on: August 2001INHS Technical Report prepared for Division of Fisheries Illinois Department of Natural Resource

Factors Influencing Largemouth Bass Recruitment: Implications for the Illinois Management and Stocking Program, Annual Progress Report

issued August 1, 2004; Federal Aid Project F-135-R, July 1, 2003 to June 30, 2004Report issued on: August 1, 2004INHS Technical Report submitted to Division of Fisheries, Illinois Department of Natural Resource

Factors Influencing Largemouth Bass Recruitment: Implications for the Illinois Management and Stocking Program

Report issued on: August 2000INHS Technical Report prepared for Division of Fisheries, Illinois Department of Natural Resource

Factors Influencing Largemouth Bass Recruitment: Implications for the Illinois Management and Stocking Program

Federal Aid Project F-135-R issued August 1, 2003INHS Technical Report prepared for Division of Fisheries, Illinois Department of Natural Resource

Disturbance regime and limits on benefits of refuge use for fishes in a fluctuating hydroscape

Refuge habitats increase survival rate and recovery time of populations experiencing environmental disturbance, but limits on the ability of refuges to buffer communities are poorly understood. We hypothesized that importance of refuges in preventing population declines and alteration in community structure has a non-linear relationship with severity of disturbance. In the Florida Everglades, alligator ponds are used as refuge habitat by fishes during seasonal drying of marsh habitats. Using an 11-year record of hydrological conditions and fish abundance in 10 marshes and 34 alligator ponds from two regions of the Everglades, we sought to characterize patterns of refuge use and temporal dynamics of fish abundance and community structure across changing intensity, duration, and frequency of drought disturbance. Abundance in alligator ponds was positively related to refuge size, distance from alternative refugia (e.g. canals), and abundance in surrounding marsh prior to hydrologic disturbance. Variables negatively related to abundance in alligator ponds included water level in surrounding marsh and abundance of disturbance-tolerant species. Refuge community structure did not differ between regions because the same subset of species in both regions used alligator ponds during droughts. When time between disturbances was short, fish abundance declined in marshes, and in the region with the most spatially extensive pattern of disturbance, community structure was altered in both marshes and alligator ponds because of an increased proportion of species more resistant to disturbance. These changes in community structure were associated with increases in both duration and frequency of hydrologic disturbance. Use of refuge habitat had a modal relationship with severity of disturbance regime. Spatial patterns of response suggest that decline in refuge use was because of decreased effectiveness of refuge habitat in reducing mortality and providing sufficient time for recovery for fish communities experiencing reduced time between disturbance events

Factors Influencing Largemouth Bass Recruitment: Implications for the Illinois Management and Stocking Program

Annual Progress Report, Federal Aid Project F-135-R, July 1, 2005 - June 30, 2006Report issued on: August 2006INHS Technical Report submitted to the Illinois Department of Natural Resources, Division of Fisherie

Factors Influencing Largemouth Bass Recruitment: Implications for the Illinois Management and Stocking Program

ID: 9040; issued August 1, 2005INHS Technical Report prepared for Division of Fisheries, Illinois Department of Natural Resource