Abstract.-We examined the relationship between bait and lure size and type and body size, injury, and handling time for northern pike Esox lucius, an important recreational fisheries resource in much of North America and Europe. Bait type and size were significantly related to the size of fish captured and hooking location. Hooking in critical locations (i.e., gills, gullet) was more likely to occur with natural bait, soft plastic shads and jigs, and spoons than with spinners and wobblers (i.e., plugs). Small baits (,75 mm) were more likely to hook the fish in the gills and less likely to hook the fish in the upper jaw than larger baits. It took longer to remove hooks from gills than from other hooking locations. Frequency of bleeding was related to depth of hooking but was unrelated to fish size, bait type, bait size, or fishing method. Initial mortality of northern pike was low (mean 6 95% confidence interval ¼ 2.4 6 1.5%), and hooking mortality was significantly related to the level of bleeding as a proxy for severity of injury. Results of this study suggest that using large artificial lures and large natural baits can effectively reduce the incidence of hooking small northern pike (i.e., those that are sublegal in some jurisdictions). However, the use of natural bait can also result in a higher incidence of deep hooking, which in turn increases the likelihood of injury and bleeding. This study revealed the complexity associated with using bait and lure restrictions to complement standard harvest regulations in northern pike recreational fisheries.

Intra-population variation in behaviour unrelated to sex, size or age exists in a variety of species. The mechanisms behind behavioural diversification have only been partly understood, but density-dependent resource availability may play a crucial role. To explore the potential coexistence of different behavioural types within a natural fish population, we conducted a radio telemetry study, measuring habitat use and swimming activity patterns of pike (Esox lucius), a sit-and-wait predatory fish. Three behavioural types co-occurred in the study lake. While two types of fish only selected vegetated littoral habitats, the third type opportunistically used all habitats and increased its pelagic occurrence in response to decreasing resource biomasses. There were no differences in size, age or lifetime growth between the three behavioural types. However, habitat-opportunistic pike were substantially more active than the other two behavioural types, which is energetically costly. The identical growth rates exhibited by all behavioural types indicate that these higher activity costs of opportunistic behaviour were compensated for by increased prey consumption in the less favourable pelagic habitat resulting in approximately equal fitness of all pike groups. We conclude that behavioural diversification in habitat use and activity reduces intraspecific competition in preferred littoral habitats. This may facilitate the emergence of an ideal free distribution of pike along resource gradients.

The objective of this study was to contrast movement rates and habitat choice of pike (Esox lucius Linnaeus) in mid-summer and mid-winter in a 25-ha lake (Kleiner Döllnsee, northeastern Germany) using radio-telemetry. Positional telemetry for consecutive 96-h was conducted by boat in July 2005 and by walking on surface ice in January/February 2006. Positions of pike (N = 11) were recorded with a GPS unit corrected by a reference station. Movement rates, distance to shore and habitat use were compared between summer and winter and relative to daytime and fish length. Pike moved significantly more in summer, and during summer had activity peaks in twilight periods. In winter, pronounced activity peaks at specific daytime periods were missing and pike chose habitats significantly closer to shore. In summer, submerged macrophyte beds were positively and pelagic areas negatively selected. In winter, pike negatively selected shallow open water in the littoral zone, and there was a tendency to avoid the pelagic. Movement rate and distance to shore were significantly and positively related to the size of pike.

Key-words:angling, disturbance, fitness, telemetry, Esox luciusIn a catch-and-release recreational fishery fish populations can be impacted by lethal and sub-lethal effects. In terms of sub-lethal effects anglers may directly (catch-and-release) and/or indirectly (angling-related disturbances, e.g. boating) influence the behaviour, growth and fitness of the fish. We quantified the long-term behavioural response of northern pike Esox lucius to angler-induced direct and indirect disturbances using radio-telemetry techniques. A whole lake experimental approach was conducted by dividing the study lake into an angling-disturbed and an angling-undisturbed lake side with 10 radio-tagged fish on each side, representing~20% of the adult pike population. The impact of anglingcaused disturbances on pike behaviour and growth as a proxy for fitness was assessed in a 7 month study period. Direct disturbances reduced swimming activities of pike and resulted in increased selection for structured (i.e., safer) habitat, whereas indirect disturbances had no significant effect on pike behaviour. Growth rates of caught-and-released fish were significantly smaller than those of uncaught pike (44%). Because, fish that were not captured by angling during the study period showed similar growth rates on both sides of the lake, this indicated that only direct angler-induced disturbances influenced pike growth. Our findings call for minimization of angling-related stressors during the process of catchand-release angling to avoid behavioural and fitness impairments of the released fish because these may ultimately have population-level effects. RÉSUMÉLes conséquences des perturbations non-létales directes et indirectes sur le comportement et la fitness de brochets (Esox lucius) dans une pêcherie avec capture et relâcher Mots-clés :pêche, perturbation, fitness, télémétrie, Esox lucius Dans les pêcheries en capture-relâcher, les populations de poissons peuvent être impactées par des effets létaux et sub-létaux. En termes d'effets sub-létaux, les pêcheurs peuvent directement (capture-relâcher) et/ou indirectement (perturbations à lier à la pêche, la navigation, par exemple) influencer le comportement, la croissance et la forme du poisson. Nous avons quantifié la réponse à long terme du comportement du brochet Esox Lucius aux perturbations directes et indirectes induites par les pêcheurs en utilisant des techniques de radio-télémétrie. Une approche expérimentale globale du lac a été réalisée en divisant le lac étudié en un côté du lac perturbé par la pêche et un autre côté non perturbé avec 10 poissons radio-marqués de chaque côté, ce qui représente environ 20 % de la population des brochets adultes. L'impact des perturbations causées par la pêche sur le comportement des brochets et de leur croissance comme un proxy de la fitness a été évalué sur une période d'étude de 7 mois. Les perturbations directes réduisent les activités de déplacement du brochet et conduisent à la sélection accrue d'habitats structurés (i.e., plus sûrs), alors q...