The success of fish stocking programs is dependent on poststocking survival. However, survival can be influenced by size‐selective mortality, where larger individuals are expected to be less vulnerable to predation. Walleye Sander vitreus is a commonly stocked sport fish, but little is known regarding the role of size‐selective predation on age‐0 Walleye (90–290 mm TL) that are stocked in the presence of various piscivores with different foraging strategies and morphological features. Our objective was to evaluate whether the TL of consumed age‐0 Walleye was related to predator TL, predator gape height, or the probability of predation. We also assessed whether length distributions varied among stocked, recaptured, and consumed age‐0 Walleye. Data for the food habits of Largemouth Bass Micropterus salmoides, Smallmouth Bass M. dolomieu, Northern Pike Esox lucius, adult Walleye, and Muskellunge Esox masquinongy were collected from East Okoboji Lake and West Okoboji Lake, Iowa, USA during fall 2015–2017. Over the course of the study, 301 age‐0 Walleye were recovered from 3,514 predator stomachs. Mean, maximum (85th percentile), and minimum (15th percentile) TL of the consumed age‐0 Walleye were not related to the TL or gape height of the predators (P > 0.05), but the probability of predation decreased by 0.02 for every 10‐mm increase in the TL of the age‐0 Walleye. The length distributions indicated that consumed Walleye were generally smaller, whereas recaptured Walleye tended to be larger than stocked fish were. Our approach to evaluating poststocking size‐selective predation on age‐0 Walleye furthers the current understanding of the importance of size at stocking relative to stocking success and suggests that stocking Walleye > 220 mm is economically advantageous for reducing predation risk.

Hatchery propagation techniques, such as pellet‐rearing, can result in altered feeding behaviour. Walleye Sander vitreus (Mitchill) is a commonly propagated sportfish, yet little is known regarding its ability to switch to live prey post‐stocking. The objectives were to evaluate temporal changes in diet composition and condition as well as evaluate the relationship between total length and presence of different prey consumed by stocked walleye fry and fingerlings. Fingerling walleye had higher average proportions of empty stomachs and benthic invertebrates but less fish that stocked walleye fry. The presence of zooplankton, benthic invertebrates or fish was not related to walleye length. Walleye condition was similar between cohorts and did not change over days post‐stocking. Percent similarity index values between cohorts were variable (0.0 to 67.9%). It was concluded that stocked walleye fingerlings consume lower quality prey items than stocked fry counterparts at least up to 49‐day post‐stocking, which may have implications for post‐stocking survival.

Decreasing bag limits is a management mechanism for enhancing size structure of Bluegill Lepomis macrochirus. However, restrictive bag limits can promote culling, where an angler returns a live fish to the water in exchange for another. Little is known about the effect of culling on ice-angled fishes.Our objective was to compare the effects of Bluegill confinement methods (reference, ice well, and bucket) and holding durations (0, 1, 2, or 5 hours) on changes in water quality parameters (dissolved oxygen, pH, carbon dioxide, and water temperature) and Bluegill stress physiology (blood glucose and plasma cortisol), reflex responses (RAMP scores), and mortality while ice-angling. In February 2018, 182 Bluegill were angled through the ice and randomly assigned a confinement method and holding duration. Bluegill blood glucose levels were higher in both confinement methods than reference fish at 2 and 5-hour holding durations. Bluegill had higher blood glucose levels in buckets than ice wells at 1 and 2 hours, but had higher blood glucose levels in ice wells at 5 hours. Water temperature was warmer in buckets than ice wells at all holding durations, while ice wells were cooler than ambient lake temperature. Bucket pH was higher than the lake at 2 hours and ice well pH was higher than the lake at 1 and 2 hours. Bluegill RAMP scores were similar across all holding durations and confinement methods, but were elevated in individuals held for the 24-hour mortality assessment.Two Bluegill mortalities occurred for fish held in ice wells. Our results suggest confinement method and holding duration while ice-angling can result in altered Bluegill blood glucose concentrations, water temperatures, and pH concentrations but that culling while ice-angling might not result in mortality. Consequently, culling practices may be compatible with and not negate the intended benefits of reduced Bluegill bag limits.Catch-and-release angling is a popular recreational activity driven by changes in angler conservation ethics and more restrictive harvest regulations (Cowx 2002;Cooke and Cowx 2004; Bartholmuw and Bohnsack 2005). Benefits of catch-and-release angling include enhanced recreational quality, increased catch rates, and improved size structure (Hubert and Quist 2010). However, success of catch-and-release practices relies on the assumption that released fish will survive after experiencing stressors associated with capture, handing, and confinement (Arlinghaus et al. 2007). The catch-and- Accepted ArticleThis article is protected by copyright. All rights reserved release process can directly influence changes in fish stress physiology (e.g., changes in blood glucose and plasma cortisol concentrations) via handling practices (e.g., Pottinger 1998;Meka and McCormick 2005) and indirectly via changes associated with confinement water quality (e.g., water temperature, ammonia, carbon dioxide, and dissolved oxygen; Caldwell and Hinshaw 1994;Meka and McCormick 2005). Prolonged exposure to stressors associated with catch-and-release anglin...

Fish hatcheries are generally not adjacent to stocking locations. Thus, hatchery fish undergo transportation processes for variable durations that can result in changes in water quality, fish physiology (e.g., whole blood glucose and plasma cortisol), and reduced survival. Walleye Sander virteus are commonly stocked throughout North America with variable stocking success, possibly due to altered physiological responses associated with changes in water quality parameters during transportation. We hypothesized increased transport duration would be associated with increases in water temperature, carbon dioxide, and total ammonia nitrogen and decreases in pH and total alkalinity. We also hypothesized that increases in carbon dioxide, water temperature, unionized ammonia, and total ammonia nitrogen would be positively related with Walleye whole blood glucose and plasma cortisol concentrations. Walleye were transported either 0, 0.5, 3, or 5 hours and whole blood glucose and plasma cortisol concentrations and mortality were evaluated for 48 hours post-transport. Total ammonia nitrogen concentrations, carbon dioxide, pH, and water temperature increased with transportation duration while total alkalinity decreased. Plasma cortisol and whole blood glucose concentrations of Walleye transported longer durations took longer to decline relative to those not transported. Water quality parameters were not associated with changes in Walleye whole blood glucose and plasma cortisol concentrations, but they were negatively related with time since transport (P < 0.05). Despite increases in stress, mortality was low (2.5%). Overall, we found evidence to support our hypotheses regarding reduced water quality associated with increasing transport duration. Finally, whole blood glucose and plasma cortisol concentration of Walleye transported were similar to those not transported, suggesting handling procedures before transportation could play a significant role in physiological responses measured after transportation. Further, evaluation of stocking procedures aimed at decreasing handling during the loading process could enhance stocking protocols..Elevated concentrations of whole blood glucose and plasma cortisol following transport could make recently stocked Walleye more susceptible to the effects of other environmental factors such as starvation, predation, and disease, all of which could result in increased mortality rates after stocking.

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