Northern Pike Populations Research Articles

Population Characteristics and Ecological Role of Northern Pike in Shallow Natural Lakes in Nebraska

Abstract Northern pike Esox lucius were sampled in Nebraska's Sandhill lakes during 1998 and 1999 to determine population characteristics and their influence on the fish community in these shallow, warm lakes at the southwestern edge of this species' natural range. Density-dependent growth, size structure, and condition were not evident in the northern pike populations sampled. Relative abundance of largemouth bass Micropterus salmoides was positively related to size structure of yellow perch Perca flavescens and bluegills Lepomis macrochirus when northen pike were absent. When northern pike and largemouth bass populations were sympatric, these relationships were less evident. Population size structure of yellow perch was lower in lakes with northern pike, but decreased size structure was not evident for bluegills. Northern pike growth decreased with July bottom water temperature, which ranged from 20°C to 25°C. Recruitment patterns of northern pike in the Sandhill lakes appeared to be lake-specific, stro...

Interrelationships among Production, Density, Growth, and Mortality of Northern Pike in Seven North-Central Minnesota Lakes

Abstract Secondary production can be an important indicator of performance for a fish population. In this study we examined how density, growth, and mortality operated together to alter production of northern pike Esox lucius in seven north–central Minnesota lakes. Estimated densities of age-2 and older northern pike were 3–59 fish/ha and estimated production rates were 0.77–8.31 kg·ha−1·year−1 across the seven lakes. The relationship between density and production among the lakes was curvilinear, production being moderated by slow growth rates at high northern pike densities. The negative relationship between indices of individual fish growth and production was counterintuitive and demonstrated the overwhelming influence of density on northern pike population dynamics. Relationships between total mortality and either density or production were not apparent. Recreational fisheries in Minnesota appear to be harvesting much of the annual production of northern pike. Yet many northern pike populations are ma...

Fish Community Responses to the Establishment of a Piscivore, Northern Pike (Esox lucius), in a Nebraska Sandhill Lake

ABSTRACT Northern pike (Esox lucius) was first documented in West Long Lake, Nebraska, in 1998 when two pike <380 mm were collected. In 2002, a Peterson mark-recapture population estimate on northern pike revealed density and standing stock (i.e., biomass) estimates of 35.8 fish/ha (95% CI= ± 8.8) and 22.0 kg/ha (95% CI= ± 5.4), respectively. Consequently, West Long Lake was sampled in 2002 to compare relative abundance, size structure, and growth of bluegill (Lepomis macrochirus), largemouth bass (Micropterus salmoides), and yellow perch (Perca flavescens) prior to and after the establishment of a high-density northern pike population. Bluegill, largemouth bass, and yellow perch relative abundances were significantly lower in 2002 than 1998. Similarly, size structures of all three species were significantly different between years. Size structure declined for both bluegill and yellow perch, and increased for largemouth bass. Growth was significantly higher for bluegill, largemouth bass, and yellow perch in 2002 than 1998. While the fish community changes were expected with the establishment of northern pike, they occurred in a relatively short time period (i.e., four years).

An Overview of Northern Pike Regulations in North America

Abstract Northern pike (Esox lucius) is a popular sport fish in the United States and Canada that is currently managed for multiple angler uses. However, there has been increased concern over lower quality (i.e., smaller fish) northern pike populations. In 1997, the Esocid Technical Committee (ETC) of the North Central Division of the American Fisheries Society surveyed natural resource agencies about their northern pike management. In addition, a round-table discussion on the quality of northern pike management was conducted in 1999. This paper is a summary of the ETC findings. In some cases, northern pike regulations have existed since the late 1800s, but most states and provinces did not use regulations until the 1950s or 1960s. Some agencies currently manage northern pike for angling quality (i.e., more large fish), others have few or no northern pike regulations, and some agencies manage for quality in some water bodies and do not manage northern pike at all in other water bodies. In general, states ...

Genetic relationships among populations of northern pike (Esox lucius)

We assessed genetic variation, using microsatellite markers, in 14 populations of northern pike (Esox lucius) in the North Central United States and in six populations from Quebec, Alaska, Siberia, and Finland. Eight of 13 loci examined were polymorphic in at least one population with an average heterozygosity at all loci and across all populations of 0.14. The Rstand Fstvalues indicated differentiation among populations (Rst= 0.61, Fst= 0.42). Although microsatellite variation found in northern pike was much lower than that found in sympatric and other fish species, the polymorphisms differentiated populations of greater geographical proximity than was possible in prior studies using allozymes and mitochondrial DNA. We generated UPGMA-clustering phenograms based on five genetic distance measures with 2000 bootstrap replicates per measure. All measures yielded highly repeatable population structure between continents (supporting values = 92.4-100%) and within Finland (42.3-98%). Four measures differentiated the Alaskan population and Young Lake (Great Lakes drainage) from other North American populations (56.6-87.7%). Relationships among other North Central United States populations were unclear, as indicated by low supporting values. Results support the hypotheses of one refugium in the North Central United States and more than one refugium in Europe during the last glaciation.

Recreational Darkhouse Spearing for Northern Pike in Minnesota: Historical Changes in Effort and Harvest and Comparisons with Angling

Abstract A traditional form of harvest for northern pike Esox lucius during winter is darkhouse spearing through the ice. Using a comprehensive evaluation of creel surveys and license sales in Minnesota, we document a long-term decline in this unique sport fishery. The decline in recreational spear fishing effort cannot be blamed on catch rates because spearing catch rates have not changed perceptibly with time. Catch rates for spearing (mean = 0.175 fish/h) are similar to harvest rates by anglers that are targeting northern pike. Conflicts between spearers and anglers have led to questions about relative harvests by each group and their effects on northern pike populations. Creel survey data since 1980 show that summer and winter angling account for most of the northern pike harvest. Spearing accounted for 15% of the average yield of northern pike by number, but spearing is selective for the larger fish. In comparison with population estimates, spearing removes a small proportion of the total population ...

Genetic relationships among populations of northern pike (&lt;i&gt;Esox lucius&lt;/i&gt;)

Genetic relationships among populations of northern pike (&lt;i&gt;Esox lucius&lt;/i&gt;)

Factors Affecting Growth of Northern Pike in Small Northern Wisconsin Lakes

Abstract Fish assemblages that include northern pike Esox lucius as a dominant predator were sampled in 19 small (<120 ha) northern Wisconsin lakes. The purpose of this sampling was to describe northern pike population characteristics and identify factors affecting growth rates. Fish assemblages in these lakes were dominated by centrarchids, primarily bluegill Lepomis macrochirus, and small fusiform species such as yellow perch Perca flavescens. Northern pike population size structures were typically truncated at around 53 cm. Average density of northern pike (≥35 cm) was 16.1 fish/ha and ranged 2.8–38.0 fish/ha. Growth of northern pike decreased, in comparison with a growth standard, as early as age 4. Most northern pike were less than age 6, and few fish were older than age 8. Diet of northern pike generally indicated opportunistic feeding strategies with some preference for fusiform prey. Multiple factors were identified as potentially limiting northern pike growth and size structure. Northern pike gro...

Density, Size, and Foods of Larval Northern Pike in Natural and Artificial Wetlands

Larval northern pike Esox lucius were sampled in natural and artificial wetlands associated with Conesus Lake, New York, on 25 April, 8 May, and 26 May 1992. Larval northern pike population densities declined significantly between the first (25 April) and second (8 May) sampling periods, indicating mortality or emigration from the wetlands; only two northern pike were captured on 26 May. Larval northern pike population densities were higher in artificial wetlands on 25 April, but on 8 May no difference could be detected. Mean total length of larvae was greater in artificial wetlands on 25 April and 8 May. Larval northern pike began feeding at approximately 15 mm total length. No difference in number of food items eaten was detected between natural and artificial wetlands; however, percentage of copepods, the taxa most commonly eaten, was higher in northern pike stomachs from natural wetlands. Cannibalism was observed in 1 of the 76 stomachs examined and constituted the only vertebrate food item found. Artificial wetlands were comparable or superior to natural wetlands as northern pike spawning and rearing habitat.

Seasonal Variation in Gill-Net Sample Indexes for Northern Pike Collected from a Glacial Prairie Lake

We captured 702 northern pike Esox lucius in 416 gill-net sets on 17 monthly occasions from July 1991 to June 1993 to examine seasonal variation in sampling data in Lake Thompson, South Dakota. Mean catch per effort (CPE) of northern pike 35 cm or longer differed significantly among months during both years. Mean CPE was lowest in winter and peaked in spring of both years. Size structure estimates were lowest during early spring and summer when males dominated samples and were highest during winter when females dominated samples. Northern pike 86 cm or longer were caught primarily in winter during ice cover. Relative weight (Wr) of male and female northern pike increased during fall, peaked in late winter, and declined during the spawning period. A similar pattern was found for the gonadosomatic index of female northern pike but not for males. Increases in the gonadosomatic index for males occurred entirely during fall. Gonadosomatic index and Wr were positively correlated for female northern pike, but the correlation was lower for males. We suspect our findings will be most applicable for interpreting northern pike population surveys made during narrow time periods near the southern portion of the speciesˈ range and for populations found in shallow, warmer water bodies.

Exploitation of Northern Pike in Seven Small North-Central Minnesota Lakes

Exploitation of native northern pike Esox lucius was studied in seven small (<300 ha) north-central Minnesota lakes in view of historical declines in northern pike sizes and heightened interest in experimental length limit regulations. Northern pike in the seven lakes had different population densities, size distributions, and exploitation rates. Creel surveys showed that anglers released 75% of the northern pike that they caught. Annual exploitation rates based on tag returns observed during a stratified creel survey ranged from 0.04 to 0.22 among the seven lakes. Good agreement was found between two methods for estimating annual exploitation in all but one lake. The size-selective nature of the recreational fishery was evident in annual exploitation rates. Annual exploitation rates for the larger northern pike (>500 mm total length) were approximately 2 to 9 times greater than for smaller fish (≤500 mm). Relatively high total annual mortality rates (mean = 0.48) compared to annual exploitation rates (mean = 0.10) indicated that natural mortality was an important aspect of northern pike population dynamics. Demands by anglers interested in catching larger fish and the high rates of catch-and-release observed in this study imply that success of experimental length limit regulations for northern pike should not be judged only by yields.

Indirect and Direct Estimates of Gill-Net Size Selectivity for Northern Pike

Size biases in gill-net sampling of populations of northern pike Esox lucius were described with indirect and direct estimates of gill-net selectivity. In deriving indirect estimates of selectivity, length distributions of northern pike retained in gill nets of five different mesh sizes were compared, and swimming performance relative to body length was used as a measure of the rate at which northern pike encounter gill nets. Selectivity was estimated directly by trapping and marking fish, and then recapturing the fish by gill netting. Indirect estimates showed that gill nets were most effective for retaining northern pike when fish length/mesh perimeter ratio was between 3.5 and 3.7. A generalized gamma function was used to model retention in the gill nets. The length structure of the northern pike population in a small lake was closely predicted when our indirect measure of selectivity was used to correct gill-net catches. Direct estimates of selectivity for all five meshes combined showed increasing selectivity with increasing fish length. Both direct and indirect methods projected increases in efficiency for catching northern pike up to 500 mm in total length. However, the indirect method tended to project higher efficiencies for catching small fish. Results from this study should be useful for interpreting northern pike catches in relation to size selection by gill nets.

Effectiveness of Liberalized Bag Limits as Management Tools for Altering Northern Pike Population Size Structure

Abstract Management efforts to restructure populations of northern pike Esox lucius consisting of small (<60 cm total length), abundant individuals in small (<200 hectares) Minnesota lakes has focused on removal by trap-netting and promoting angler harvest through liberalized bag limits. Removal by intensive trap-netting was demonstrated to be ineffective in altering northern pike population size structure, and anglers harvested substantially fewer fish than were removed by trap-netting. Unless more anglers begin harvesting more small northern pike, liberalized bag limits hold little promise as a management tool for altering northern pike population size structure in small Minnesota lakes.

A toxicological examination of whitefish (Coregonus clupeaformis) and northern pike (Esox lucius) exposed to uranium mine tailings

Operation of the Gunnar uranium mine, in nothern Saskatchewan, Canada, from 1955 to 1964, resulted in the deposition of radioactive tailings in Langley Bay, a small bay connected to Lake Athabasca. Previous publications have described the contamination of the sediments, water, macrophytes and fish of this area. The present study compares the parasite infestations, blood hematocrit, histopathology and condition factor (K) of the Langley Bay whitefish and northern pike populations with these factors measured for control populations from Lake Athabasca. No significant differences could be found, in any of the physiological parameters measured, between the contaminated and control populations.

Relations between Proportional Stock Density and Growth and Condition of Northern Pike Populations

Abstract Proportional stock density (PSD) is an index used to quantify length-frequency data. The PSD of populations of northern pike Esox lucius in eight states was positively correlated with growth and condition. Fish condition was positively correlated with PSD, which indicated that populations dominated by larger individuals had higher condition factors than did populations dominated by smaller fish. The PSD was also positively correlated with growth of northern pike. These relationships indicate that PSD is one method that can be used to assess northern pike populations.

Simulation of Mechanisms Causing Stunting in Northern Pike Populations

Abstract Some mechanisms hypothesized to cause stunting of northern pike Esox lucius include overpopulation and competition, lack of appropriately sized prey, and lack of thermal refuges in midsummer. The objective of this work was to use an energetics model of northern pike growth over 3 years to test the effects of these mechanisms on stunting. Simulations for females indicated the following: (1) competition-based stunting could occur when food resources were reduced by only 5–10% per individual, such that size at age 3 would be reduced by up to 51%; (2) lack of appropriately sized prey could result in stunting (up to 35% of a northern pike's annual ration often comes from large and rare prey), such that size at age 3 could be reduced 80%; (3) inappropriate thermal regimes could reduce northern pike growth up to 58%, but only under extremely warm conditions.

Genetic Variation and Postglacial Dispersal of Populations of Northern Pike (Esox lucius) in North America

We studied the genetic relationships and postglacial dispersal of northern pike (Esox lucius) populations in North America using allozyme data. Allelic products of up to 65 protein coding loci were examined in eight populations: five from drainages in western Canada, flowing into Hudson Bay and the Beaufort Sea; two from the Missouri River drainage, flowing into the Mississippi River; and one from the upper Mississippi River drainage, flowing into the Gulf of Mexico. Only two polymorphic loci were identified, Est-1 and Ck-1, and the average observed heterozygosity was only 0.001, much lower than that observed in most teleosts. All of the populations from the drainages in western Canada and the Missouri River were genetically identical. The Mississippi River population was unique, expressing Ck-1 (140), an allele nearly absent in all other populations, at a frequency of 0.99. Our data suggest that the Missouri River drainage, during the period when it was isolated from the Mississippi River, was the southern refugium from which northern pike radiated during deglaciation.

Walleye, Stizostedion vitreum, and northern pike, Esox lucius, populations in three Alberta lakes

Results are presented from a survey of walleye and northern pike in Ethel, Marie and Wolf Lakes, Alberta conducted May‐September, 1983. Three types of experimental gill net were fished, mainly inshore. Northern pike were abundant in all three lakes but white sucker and yellow perch also were common. Walleye were caught in largest numbers in Wolf Lake. Age and growth of both walleye and northern pike were determined from examination of the opercular bones. The walleye in the three lakes were represented by a few strong year classes but there was no synchronism between the lakes. The strong 1975 year class in Ethel and Wolf Lakes may have been correlated with high spring precipitation and heavy run‐off. Although there were dominant year classes in the northern pike populations (especially the 1979 year class) the variability was not so marked as in the walleye. There were no significant differences between length‐at‐age for year classes of walleye in Ethel and Marie or northern pike in all three lakes. In Wolf Lake the 1978 and 1979 year classes grew faster than in previous years. Walleye and northern pike growth was well described by the von Bertalanffy growth model. Females of both species grew to a greater ultimate length and had a longer lifespan than the males. Fecundity data are presented for walleye from Wolf Lake (log10 absolute fecundity = 0.856 + 2.441 log10 length) and northern pike from Marie Lake (log10 absolute fecundity =−2.671+4.052 log10 length). The stomach contents of both species were examined during May and June. The majority of walleye had empty stomachs. Walleye and northern pike in Ethel and Wolf Lakes fed on a variety of fish and invertebrate species but both fed mainly on fish (in particular whitefish) in Marie Lake. The similarity of diet suggests competition for prey species. A walleye yield to commercial fishermen of c. 0.69 kg ha−1 year−1 in Wolf Lake has made up 8% of the total catch. Since 1970/71 when mesh size of nets was increased, the yield has been reduced to c. 0.30 kg ha−1 year−1. Anglers remove an additional c. 0.48 kg ha−1 year−1 walleye from Wolf Lake. Northern pike yields to commercial fishermen have been c. 2.00 kg ha−1 year−1 in Wolf Lake. Ethel and Marie Lakes have yielded only poor catches of walleye and northern pike. A yield model was used to illustrate that faster‐growing northern pike have higher potential yields than walleye. Walleye produce higher yields in Wolf Lake than in Marie Lake, the reverse being true for northern pike. It is suggested that northern pike could be cropped at a higher rate in Marie and Wolf Lakes with a possible improvement in walleye stocks.

Characteristics of a Crappie Population in an Unfished Small Impoundment Containing Northern Pike

Abstract Desirable black crappie (Pomoxis nigromaculatus) and white crappie (Pomoxis annularis) populations were documented in a small impoundment in Colorado. Individuals 250 mm long and longer comprised 21% of the black crappies and 44% of the white crappies 130 mm long and longer. Mean relative weight (Wr) information indicated that crappie were in good condition and growth rates were average. Northern pike (Esox lucius) population estimates for 550-mm long and longer individuals varied from 119 to 217 fish during the 1973-1980 sampling period. Biomass of northern pike 550 mm long and longer was estimated to be 18.4 kg/hectare in 1980. Northern pike predation may help maintain desirable crappie populations in small impoundments.

Response of a Boreal Northern Pike (Esox lucius) Population to Lake Impoundment: Wupaw Bay, Southern Indian Lake, Manitoba

A population of northern pike (Esox lucius) in Wupaw Bay, Southern Indian Lake, Manitoba, was monitored for 1 yr prior to impoundment of the lake and for 5 yr after impoundment. Impoundment had a pronounced but transient effect on pike reproductive success. The abundance of young-of-the-year pike in 1977, the 1st yr following impoundment, was 4–10 times higher than in the following 3 yr. Flooded terrestrial vegetation was apparently conducive to pike reproductive success only in the 1st yr after inundation. A strong 1977 year-class was evident in gillnet catches 4 yr later. This year-class was slower growing and in poorer condition than other year-classes. The impoundment of Wupaw Bay had no discernible effect on the growth, condition, or mortality of the adult pike population, with the exception of changes ascribed to the presence of the large 1977 year-class. The growth of the adult pike population appeared to be limited by forage fish abundance, but variations in feeding on fish were largely unexplained and were probably due to natural variation. The year-to-year pattern of forage fish reproductive success could not be related to the timing of lake impoundment, but may have been related to summer water temperatures. Variations in feeding on invertebrates appeared to be due to postimpoundment increases in productivity, but these changes were insufficient to affect population parameters. Wupaw Bay surface area increased by only 9% as a result of lake impoundment, the smallest areal increase in the Southern Indian Lake reservoir. The influx of nutrients and flooded terrestrial vegetation was therefore much smaller than in other temperate reservoirs where increases in pike production have been observed.