Fishes can exhibit many forms of plasticity to maximize fitness. However, limited information exists on the ability of freshwater fish to adjust spawning behavior and characteristics (e.g., timing, duration, magnitude of spawning events) to minimize mortality of recruits and ultimately maximize fitness. We wanted to test the life history hypothesis for bluegill (Lepomis macrochirus) (i.e., opportunistic strategy) utilizing existing literature and results from our study to further evaluate the potential for spawning plasticity in this species. Our objective was to identify bluegill recruitment bottlenecks (i.e., periods of high mortality) and factors associated with these events in a single lake during 7 consecutive years. Bluegills exhibited shorter spawning durations and fewer spawning pulses (i.e., peaks in larval production) compared with bluegill in previous studies. Late-hatched (compared with early-hatched) bluegills consistently contributed the most to the fall juvenile population; these recruitment patterns were primarily attributed to biotic drivers. Our study suggests that bluegill could exhibit spawning plasticity and extends our current understanding of adaptations that are potentially capable of increasing fitness for a freshwater fish species under a wide range of environmental conditions and uncertainty.
Creel surveys are the most common angler use survey used by fisheries managers but can be time intensive and expensive to conduct. Time‐lapse cameras have been evaluated as a cost‐efficient alternative to creel surveys on small lakes, streams, and nearshore marine systems but have yet to be evaluated on a reservoir. The objectives of this study were to evaluate the feasibility of using time‐lapse cameras to assess angling use on a high‐use reservoir and provide methodology for use by fisheries managers. One time‐lapse trail camera was installed at a heavily used boat ramp at Lake Pleasant, a large reservoir located near Phoenix, Arizona, from December 2015 to May 2016. A single observer counted fishing and recreational boats and tracked individual fishing boat trips using a randomized schedule. Camera data were first validated against creel counts conducted in person, and subsequent corrected counts were used to estimate both angling and boating use for the study period. Camera counts were easily corrected using the validation approach and were more cost effective than traditional creel survey methods. Overall, we found that time‐lapse cameras can efficiently and accurately collect angler use data on a high‐use reservoir and thus provide a useful alternative to stand‐alone creel surveys. Creel surveys are the most common angler use survey used by fisheries managers but can be time intensive and expensive to conduct. Time‐lapse cameras have been evaluated as a cost‐efficient alternative to creel surveys on small lakes, streams, and nearshore marine systems but have yet to be evaluated on a reservoir. The objectives of this study were to evaluate the feasibility of using time‐lapse cameras to assess angling use on a high‐use reservoir and provide methodology for use by fisheries managers. One time‐lapse trail camera was installed at a heavily used boat ramp at Lake Pleasant, a large reservoir located near Phoenix, Arizona, from December 2015 to May 2016. A single observer counted fishing and recreational boats and tracked individual fishing boat trips using a randomized schedule. Camera data were first validated against creel counts conducted in person, and subsequent corrected counts were used to estimate both angling and boating use for the study period. Camera counts were easily corrected using the validation approach and were more cost effective than traditional creel survey methods. Overall, we found that time‐lapse cameras can efficiently and accurately collect angler use data on a high‐use reservoir and thus provide a useful alternative to stand‐alone creel surveys.
State and federal agencies typically introduce aquatic vegetation to increase the recruitment of sport fishes, particularly Largemouth Bass Micropterus salmoides. However, due to frequent turbidity and water-level fluctuations, managers in the southern United States are often left to introduce emergent macrophytes instead of submersed macrophytes. Emergent macrophytes have less underwater structural complexity than most submersed macrophytes and therefore may not be as effective in reducing the predation risk of Largemouth Bass. Therefore, the objective of this study was to determine if American water willow Justicia americana, a common emergent macrophyte species introduced in reservoirs, increases the survival of juvenile Largemouth Bass when exposed to predation. Predator-prey interactions between 10 juvenile and 1 adult Largemouth Bass were observed in tanks with natural densities of American water willow and compared with similar trials in vegetation-free control tanks. Each adult Largemouth Bass was tested once in each treatment (vegetation present or absent). Water willow significantly reduced the capture-to-attack ratio of adult Largemouth Bass and decreased the amount of time spent searching and the number of captures, resulting in significantly higher juvenile survival in the vegetated trials. Although water willow provided a similar increase in survival compared with previous studies using submersed macrophytes, the mechanism underlying this change differed, likely resulting from the more rigid stem design of water willow. We conclude water willow is an excellent candidate for establishment in reservoirs because it is easier to establish than many other macrophyte species yet still reduces predation risk on juvenile Largemouth Bass.
Aquatic vegetation can impact juvenile fishes through multiple pathways. Previous studies have found that dense macrophytes can cause a trade‐off of survival for Bluegills Lepomis macrochirus, with decreased foraging efficiency in macrophytes but also decreased predation risk. For juvenile Largemouth Bass Micropterus salmoides, this phenomenon has been proposed but never experimentally tested. In addition, little information exists on the effects of vegetation on juvenile Largemouth Bass prior to the shift to piscivory, a critical period in the recruitment process. Therefore, the objective of this study was to determine if aquatic vegetation reduces the foraging ability of invertivorous (prepiscivorous) juvenile Largemouth Bass. Twenty‐four invertivorous juvenile Largemouth Bass were tested individually at each of five stem densities (0, 125, 250, 500, and 1,000 stems/m2) of artificial macrophytes within 20.8‐liter aquaria. Five treatments of a simple stem architecture (at all stem densities) and three complex stem architecture treatments (125, 250, and 500 stems/m2) were used within this experiment. Complex stem density treatments were created using a branched design which doubled the string abundance (number of strings) within the water relative to corresponding stem densities in simple vegetation treatments. Thirty chironomid larvae were used as prey during each 15‐minute foraging bout. Foraging return (number of chironomid larvae consumed/15‐minute foraging bout) was not significantly different among all stem treatments. Therefore, our results suggest the predator avoidance advantage aquatic macrophytes provide to juvenile Largemouth Bass does not come with a trade‐off in foraging efficiency (up to 1,000 stems/m2 vegetation density), at least when Largemouth Bass are prepiscivorous. Received December 15, 2015; accepted March 23, 2016 Published online July 7, 2016
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