- Humboldt University
- University of Hohenheim
- Carleton University
Summary
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 ± 95% confidence interval = 2.4 ± 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.
Methodology
The study was carried out in Germany and Canada within two mesotrophic lakes with naturally reproducing northern pike populations. The German component of the study was conducted at Lake Kleiner Döllnsee, about 80 km northeast of Berlin in the northeastern lowlands of Germany (52º59'32.1"N, 13º34'46.5"E). This natural lake (surface area ¼ 25 ha) has a mean depth of 4.1 m (maximum depth ¼ 7.8 m), is mesotrophic to slightly eutrophic, and is dimictic. Dense reed belts (bulrushes Typha spp., common reeds Phragmites spp.) are characteristic habitats in this lake together with several areas where submerged macrophytes flourish (see Klefoth 2007 and Kobler 2007 for details). Eckmann (1995) reported 10 different fish species in this lake; Klefoth (2007) and Kobler (2007) reported two additional species. Among the top predators, northern pike and Eurasian perch Perca fluviatilis are abundant and European eel Anguilla anguilla and European catfish Silurus glanis are also present. However, abundance of the latter two species is low (Eckmann 1995) and both species have been introduced through stocking for scientific purposes (Klefoth 2007; Kobler 2007). Experimental angling took place from June to September 2005.
The Canadian part of the study was conducted at Lake Opinicon, a shallow (mean depth ¼ 4.5 m), mesotrophic natural lake in eastern Ontario (44º33'56.0"N, 76º19'23.6"W). Compared with Lake Kleiner Döllnsee, this lake is large (787 ha) and dimictic. Emerged macrophytes are sparse, but submerged macrophytes are very abundant in all parts except the deepest areas of the lake. The fish species community is characterized by abundant populations of northern pike, largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, rock bass Ambloplites rupestris, bluegill Lepomis macrochirus, pumpkinseeds L. gibbosus, and small cyprinids (Keast et al. 1978). Lake Opinicon was angled experimentally in May 2006.
Northern pike populations in both study lakes are moderately exploited by hook-and-line fishing. Whereas public fishing pressure seems to be moderate for northern pike in Lake Opinicon, public fishing is prohibited in Lake Kleiner Döllnsee. However, in Lake Kleiner Döllnsee during recent years, there has been some sampling by fyke nets, gillnetting, and angling conducted for scientific inquiry by members of the Leibniz-Institute of Freshwater Ecology and Inland Fisheries. Lake Opinicon has no size limit for northern pike but does have a bag limit, and there is a seasonal closure between mid-November and mid-May. Both lakes contained self-sustaining populations of northern pike.