Northern Pike Populations Research Articles

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.

Regulation of Biomasses of Small (<41 cm) Northern Pike (Esox Indus L.), with Special Reference to the Contribution of Individuals Stocked as Fingerlings (4–6cm)

The composition and abundance of four northern pike (Esox lucius L.) populations were monitored in the period 1974–82. The biomasses of 0+ pike, pike <35 cm and pike <41 cm were negatively correlated with those of larger individuals following an exponential relationship. It is argued that this density-dependent relation is the result of a regulation in which intraspecific predation may play a major role. The standing stock of pike <54 cm, if related to pike habitat available, was very similar both among sites within years and among years within sites. This stock is tied to a maximum per unit of vegetated area. Within this maximum the biomass of pike <41 cm is determined by the biomass of larger individuals. Therefore stocked pike did not contribute extra biomass to the population.

The evaluation of the stocking of pike fingerlings

In order to evaluate the stocking of artificially propagated northern pike (Esox lucius L.) fingerlings (4–6 cm), of which 1–1,5 million/year are produced by the Organization for the Improvement of Inland Fisheries (O.V.B.), the composition and abundance of northern pike populations in four shallow waters were monitored during a 5–8 year period. The specimens stocked were marked by amputation of a ventral fin. At the end of their first growing season the numbers of these and of those that were naturally reproduced (O+ pike) as well as the abundance of larger specimens were estimated using mark-recapture methods. Sampling was executed by electrofishing, seining and (incidentally) trawling. The O+ pike was caught quantitively by electrofishing.

Evaluation of Minimum Size Limits for St. Lawrence River Northern Pike

Abstract Traditional fisheries management practices assume that increasing a minimum size limit will increase the sustained yield of larger fish by reducing the harvest of younger fish and increasing the recruitment into the older age groups. Simulation modeling of the northern pike (Esox lucius) population in the St. Lawrence River indicates that the yield of older fish actually declines under these conditions. In the absence of density-dependent compensation, the imposition of a 660-mm minimum size limit resulted in a greater decline in total population size than that predicted under a 508-mm limit over a 50-year period. A decrease in yield was caused by an increase in the harvest of older females and a subsequent decrease in egg production. To guard against possible population decline or shift in the age structure that reduces the stability and productivity of an existing fishery, it is suggested that reproductive potential be examined whenever minimum size limits are considered.

The Composition of Northern Pike (Esox lucius L.) Populations in Four Shallow Waters in the Netherlands, with Special Reference to Factors Influencing 0+ Pike Biomass

The composition and abundance of Northern pike (Esox lucius L.) populations in four shallow waters was monitored during a 4–5 year period, using mark-recapture methods. In general, the populations were sampled by using a combination of fishing gear but pike that completed their first growing season (0+ pike) are captured quantitatively by electrofishing (3 kw, DC) exclusively. Within the length range of 0–54 cm fork length, the biomasses of 0+ pike appeared to be negatively correlated with those of larger pike. It is suggested that intraspecific predation is mainly responsible for these relations. The standing stock of <54-cm pike was found to be determined by the amount of aquatic vegetation and more especially so if the different habitat preference of 0+ pike, 0+ < pike < 41 cm and 41 cm ≤ pike < 54 cm was taken into account.