Angler and environmental influences on walleye Sander vitreus and muskellunge Esox masquinongy angler catch in Escanaba Lake, Wisconsin 2003–2015

Angler trip success and catch rates are dependent upon a fishes’ vulnerability to angling. Angling vulnerability can be influenced by angler-specific attributes (i.e., bait choice, lure size, use of a guide), and individual fish traits (i.e., boldness, aggression, stress responsiveness, and memory retention). The mechanisms that function in a fishes’ angling vulnerability, and contribute to catch rate, are likely correlated with environmental factors however, the influence of environmental factors on angling vulnerability are not well understood. We used the long-term (1946 –present) compulsory creel dataset from Escanaba Lake, WI, USA to test for interactions between angling vulnerability (i.e., angler trip success and catch rates) and environmental factors to better understand these dynamics in recreational fisheries. Our objective was to test for the influence of angler associated variables and environmental factors on open water angler trip success (i.e., catch ≥ one fish) and catch rate of walleye Sander vitreus and muskellunge Esox masquinongy during 2003–2015 using a hurdle model approach. Fishing trip success and catch rates for both species were most strongly influenced by angler-related variables (i.e., guide status, bait type, the proportion of the fish population previously caught). Environmental factors associated with lower light intensity (i.e., diel period, mean daily solar radiation, solar-Julian day interaction) had a positive influence on walleye vulnerability. Lower air temperatures and lunar position (moon overhead or underfoot) and phase (gibbous’ and full moon) also had a positive effect on walleye angling. Muskellunge trip success and catch rate were positively influenced by light metrics (i.e., diel period and mean daily solar radiation) and increased with air temperature. Lunar variables (position and phase), as well as wind speed and direction also influenced muskellunge angling vulnerability. A better understanding of the influence of environmental factors on angling vulnerability is an important component of fisheries management as management goals focus on balancing fish populations and creating satisfactory catch rates to enhance the angling experience. Our results suggest that angler-specific variables, light, temperature, lunar, and weather conditions influenced species-specific angling vulnerability for walleye and muskellunge.

Tide gates form physical and ecological obstacles to river herring (Alosa spp.) spawning migrations

River herring (Alosa spp.) are anadromous fish that enter North American Atlantic coastal rivers and lakes each spring to spawn. Anthropogenic structures such as dams and tide gates serve as physical obstacles that limit river herring access to spawning habitat. This study examined the physical and ecological components affecting herring passage through a tide gate by applying a time-to-event analysis framework to multiple movement behaviors derived from telemetry data. Herring had higher passage success early in the season (78%) than later on (16%). Key behaviors that govern passage varied with diel period, tide, and flow direction through the gates. Furthermore, these behaviors shifted as the season progressed, consistent with the hypothesis that predator avoidance may be driving passage failure late in the spawning season.

Effects of tributary size on the resource supply and physical habitat at tributary junctions along two mainstem rivers

Tributary junctions are regarded as ecologically important due to unique habitat present; however, there is limited understanding of the drivers of habitat attributes at these locations. Using six sites across two mainstem rivers, we tested whether tributary size relative to main stem governs the strength and direction of response of substrate size, stream temperature, and nutrient and coarse particulate organic matter (CPOM) concentration. We found that only phosphorus and CPOM concentration showed a significant relationship with relative tributary size. Small tributaries contributed high concentrations, whereas concentrations in larger tributaries resembled the main stem. Often, tributary exports were enough to increase the resource concentration in the main stem by 40%. Substrate coarsened by ∼60% downstream of tributaries. Temperature asynchrony was observed, where tributaries contributed water between 2.8 °C cooler to 1.9 °C warmer than the main stem within one diel period. Our results highlight the importance of small tributaries for whole network functioning. However, large spatiotemporal variability revealed how habitat attributes are highly context-dependent in these locations and may be difficult to predict in both scientific and management settings.

Seasonal depth and temperature use, and diel movements of lake trout (Salvelinus namaycush) in a subarctic lake

We conducted a multi-year acoustic telemetry study of lake trout (Salvelinus namaycush (Walbaum, 1792)) in a small subarctic lake to investigate depth and temperature occupancy, and vertical activity across seasons (summer, fall, and winter), diel periods (day, twilight, and night), and during summer periods of 24 h light (day and twilight). Analyses using generalized additive mixed models revealed a high degree of individual variation in depth occupancy independent of the factors hour of day, season, and diel period, whereas temperature occupancy and vertical activity were explained using the three combined factors. Habitats occupied were typically 9–20 m and 6–9.5 °C in summer, 1–3 m and 2–15 °C in fall during presumed spawning, and ≤6 m and <3 °C in winter. Lake trout exhibited partial diel migration where individuals displayed a variety of vertical migratory directions within and among seasons or diel period, including during periods of 24 h light. Fish were most vertically active during periods of daylight and in fall. During 24 h light, some lake trout performed crepuscular movements, whereas individual behaviour best explained modelled depth and temperature occupancy and vertical activity. The variety of vertical patterns among individuals and seasons suggests multifactor proximate causes of partial diel migration and crepuscular movements.

Factors Influencing a 24-Hour Time-Budget for Wintering Atlantic Brant

The wintering period is often a limiting time for waterfowl. To understand the behavioral dynamics of Atlantic brant Branta bernicla hrota wintering along coastal New Jersey, USA, we conducted observations across the full 24-h diel period in an effort to construct an accurate time-budget model for the wintering population. In most behavioral studies, it is only possible to collect diurnal and crepuscular behavior data, forcing the assumption that these data are representative of nocturnal behavior in order to model the full 24-h diel period. We collected behavior data in 5,902 instantaneous observational scans across 4 time periods (morning crepuscular, diurnal, evening crepuscular, and nocturnal) from the third week in October to the third week in February 2009–2010 and 2010–2011. Brant primarily allocated time toward swimming (43.5%), feeding (26.4%), resting (15.4%), and flying (7.7%); these proportions differed significantly across times of day. Brant exhibited decreased flight (4.8% vs. 9.3%) and feeding (22.3% vs. 29.6%) and increased resting behavior (24.4% vs. 10.5%) nocturnally compared with diurnal periods. We further modeled explanatory environmental variables, hunting effects (open vs. closed seasons, locations open vs. closed to hunting), and time of day (diurnal and nocturnal only) on wintering behaviors. Feeding, resting, and swimming behavior presence were most influenced by a predictive model of (Hunt Season × Hunt Location × Period) + (Tide × Period). Flight behavior presence were most influenced by a predictive model of (Hunt Season × Hunt Location × Period) + (Tide × Temperature). There is an interactive effect of hunting pressure and period of day on observed activity; therefore, our results demonstrate that not accounting for nocturnal variation in behavior can lead to biases when extrapolating to energy expenditure models. Additionally, hunting areas proved to be nocturnally valuable because these areas contain valuable energy resources that may be unavailable diurnally, and our observations show that brant will shift their activities around hunting pressures to make use of these areas.