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1.
Prof. Rita Pascolini P. Ceccarelli A. M. Gargiulo S. Lorvik 《Cell and tissue research》1985,239(2):443-445
Summary In the testis of Esox lucius at the time of spermiation, activity of cyclic adenosine 3,5-monophosphate (cAMP) was immunocytochemically localized at the level of the Sertoli cells. In these cells adenylate cyclase activity was also ultracytochemically demonstrated by using adenylyl imidodiphosphate as a substrate. Reaction products of adenylate cyclase were primarily detectable on the basal and adluminal plasma membranes and on the surface of protrusions of the cell body into the lumen. 相似文献
2.
John D. Smith 《Environmental Biology of Fishes》1986,16(4):295-308
Synopsis The seasonal transmission ofRaphidascaris acus was studied in two small lakes on Manitoulin Island, Ontario. Dragonfly nymphs and caddisfly larvae, acting as paratenic hosts, contained second-stage larvae. Several fishes, including percids and cyprinids, were intermediate hosts with second, third, and fourth-stage larvae in the liver. Yellow perch,Perca flavescens, was the most important of these. Intensities were up to 928 and increased with length and age of the perch; prevalence was 100%. Abundance ofR. acus tended to be higher in females but was not related to condition of the perch. Second-stage larvae were acquired from invertebrates in summer and developed to the fourth stage by November. They became surrounded by fibrous capsules during the next summer but remained alive for at least another year. The longevity of larvae in the intermediate host may ensure survival of the parasite through periods of low host abundance after winterkill. Northern pike,Esox lucius, was the definitive host. Abundance ofR. acus tended to be greater in larger pike but was not related to sex or condition of the fish. The parasite was acquired in late fall. Prevalence was 100% and mean intensities were over 200 in winter and spring, declining to 64–100% and less than 15, respectively, in summer. Mature worms were present from early spring through summer. Seasonality of infection in the definitive host is not attributable to seasonal availability of larvae in perch. Instead it may be controlled by timing of predation on perch and rate of development and longevity of the parasite. Transmission to pike apparently continues in summer. Low intensity may result from low recruitment rate and rapid turnover of the parasite population. 相似文献
3.
J. R. Beddington C. A. Mills †† F. Beards ‡ M. J. Minski ‡ J. N. B. Bell ‡ 《Journal of fish biology》1989,35(5):679-686
It proved possible to determine the levels of Sr-90 in the opercular bones of individual pike, Esox Iucius , and in pooled samples of bones from perch, Perca fluviatilis . Results from both species from Windermere demonstrated that Sr-90 levels rose from below the detection limits in the 1940s to a peak in the 1960s, followed by a decline in the subsequent two decades. This decline was slower than would have been expected from the decline in northern hemisphere Sr-90 fallout, indicating the likelihood of recycling within the environment. Sr-90 levels were consistently lower in pike than in perch, their main prey fish. Thus, there is no concentration of Sr-90 up this part of the aquatic food chain. Tracking Sr-90 in bones taken in successive years from ages 3 to 8 for a single cohort of pike showed that the quantity of Sr-90 was closely related to opercular bone (and hence fish) weight. No significant increase in Sr-90 concentration in the bone with increasing age was demonstrated. 相似文献
4.
The morphological response of two 1 year-old prey species, perch Perca fluviatilis and roach Rutilus rutilus to the presence of predatory pike Esox lucius , was tested in a 6 week aquarium experiment. The growth of perch was higher than that of roach but there was no difference in growth of prey between predator and control treatments. The presence of pike caused morphological changes in both perch and roach. Perch showed an increase in body depth during the experiment whereas the morphological response of roach to pike was more related to a displacement of the dorsal and pelvic fins and width of the anal fin. Differences in morphological responses of perch and roach to pike can be interpreted by their overall differences in antipredator strategies. 相似文献
5.
Reported improvements in the muskellunge angling fishery on Lake of the Woods, Ontario over the last two decades have paralleled
an increase in the practice of catch and release angling, and an increase in minimum size regulations for this species. The
overall status of muskellunge populations in this large, complex lake has proven difficult to monitor using standard assessment
methods. A volunteer muskellunge angler diary program, established in 1988, has provided a cost effective method of gathering
a large amount of information with which to track this fishery and associated populations. Results from angling diaries indicated
increased angling effort, catch and success rates for muskellunge on Lake of the Woods since the early 1990s. Although the
month of July accounted for the majority of angling effort and catch, angling success rates and sizes of fish reported in
diaries improved monthly into the late fall. Angling success rates were consistently higher in angling diaries than from creel
surveys, but both survey types showed similar long-term trends in the fishery. Angler diary data, incorporating both the numbers
of fish caught and/or seen by anglers, were used to calculate catch equality indices which proved to be sensitive to changes
in population abundance. Increased minimum length regulations for muskellunge during 1987–2001 have been largely responsible
for a decline in harvest rates from an estimated 36% in 1986 to 0% since 1999. Although higher size limits have yet to produce
more quality-sized fish in angler catches, diary survey data, supported by recent improvements in catch rates from assessment
gill nets, would indicate that muskellunge recruitment has increased. This article concludes with a brief review of how muskellunge
angler diary data has been used in the past, including recommendations to minimize biases associated with this survey method. 相似文献
6.
The threshold pH for survival of early life stages of pike Esox lucius in post-mining lakes was determined in a laboratory experiment using artificial water characterized by high concentrations of dissolved Ca, Al, Fe, Mn and SO2/4− . At pH 3·50–4·00, high mortality was observed before hatching. At pH 4·00 and 4·25, hatching rates were reduced compared with the controls (pH 7·40), and many embryos died in a partly hatched state. Hatching success of embryos exposed to pH levels of 4·50 or higher was not affected. However, at pH 5·00 many newly hatched embryos were deformed. Furthermore, pike exposed to pH 4·00–5·00 did not start feeding. At pH 4·75 and below, mortality increased to 100%, and at pH 5·00, only few eleutheroembryos which were in extremely poor condition survived to the end of the experiment. At pH 5·50, survival was in the same range as in the control group, but growth was reduced. Therefore, early life stages of pike are expected to survive in Lustian post-mining lakes when a pH of 5·50 and above is reached and maintained. 相似文献
7.
Changes in the fish community and water quality during seven years of stocking piscivorous fish in a shallow lake 总被引:6,自引:0,他引:6
SUMMARY 1. Piscivores (annual stocking of 1000 individuals ha?1 of 0+ pike and a single stocking of 30 kg ha?1 of large 20–30 cm perch) were stocked in seven consecutive years in a shallow eutrophic lake in Denmark. The stocking programme aimed at changing food‐web structure by reducing zooplanktivorous and benthivorous fish, with resultant effects on lower trophic levels and ultimately water quality. 2. The fish community and water quality parameters (Secchi depth, concentrations of total phosphorus, chlorophyll a and suspended solids) were monitored between 1996 and 2000 and relationships were evaluated between predatory fish and potential prey and between zooplanktivorous or benthivorous fish and water quality parameters. In addition, potential consumption of piscivorous fishes was calculated. 3. The density of fish feeding on larger zooplankton or benthos (roach >15 cm, crucian carp >15 cm) declined distinctly during the study period. This effect was attributed to predation by large (>50 cm) pike. Based on scale readings, we cautiously suggest that the stocking of 0+ pike boosted the adult pike population to produce an unexpected impact in later years. Conversely, no direct impact of stocked 0+ pike was detected on 0+ roach. 4. A major decline in the recruitment strength of 0+ roach was observed in 2000. A combination of (i) the indirect effect of large pike preying on adult roach, with negative effect on roach reproduction and (ii) the direct predation effect of 0+ pike and/or 1+ and 2+ perch recruited in the lake, provides the most likely explanation of this phenomenon. 5. A marked increase in Secchi depth in 2000 and declining trends in suspended solids, chlorophyll‐a and total phosphorus concentrations were observed. These changes may also be attributable to changes in the fish community, although the relationships were not straightforward. 6. This 7‐year study indicates that piscivorous fish may be a significant structuring force in shallow eutrophic lakes, suggesting that stocking piscivores can increase predation pressure on cyprinids. However, the general lack of impact of 0+ pike points to the need of refining current stocking practices in several countries across Europe. 相似文献
8.
Settlement and habitat use by juvenile pike in early winter 总被引:2,自引:0,他引:2
The spatial distribution and social behaviour of young-of-the-year pike Esox lucius was investigated in early winter. Reed beds were selected in the early exploration phase but thereafter, pike congregated in the pool habitat. A significant increase in pool occupancy combined with a decrease in reed bed occupancy and movement indicated settlement within 3 days. There was no evidence of territoriality, which has been reported previously in adult pike: indeed, inter-individual spacing was consistent with social grouping rather than territory defence. The strong preference for reed cover among juveniles reported in other studies that were undertaken during summer was not observed here. Among-individual variation in exploratory behaviour was observed but this was not related to activity levels or habitat use. 相似文献
9.
Predator inspection behaviour at different levels of attack motivation (attack status of the predator) was investigated in European minnows Phoxinus phoxinus from a population sympatric with pike Esox lucius , during controlled laboratory experiments. Shoals of minnows performed more predator inspections and formed larger inspection group sizes shortly after an attack by a pike. After inspection, minnows returned to the safety of the main shoal, regardless of predator motivation. Minnows which inspected last-before and first-after a strike by a pike modified their behaviour after inspection; they reduced feeding, increased shoaling, flicked their dorsal and pectoral fins and skittered. This behaviour signified alarm and appeared to reflect the severity of the threat posed by the predator at the time of inspection. Fish that had inspected when the pike displayed low attack motivation did not modify their behaviour after inspection to reflect alarm. Information concerning the attack motivation of the predator is probably transferred passively throughout the shoal by changed inspector behaviour and by inspection rate. These data demonstrate that: (1) minnows modified their behaviour after inspection to reflect a predator's attack motivation; and (2) minnows which inspected immediately before a strike appeared to anticipate the future attack and modified their behaviour accordingly. 相似文献
10.
A brief review is provided in some advances in understanding the ecology of pike Esox
lucius Linnaeus over the last 10 years. Based on long-term studies and manipulative, often short-term experiments (laboratory, field
and mesocosms) several established theories have been supported, as well as new concepts developed. Despite their wide distribution
pike show low levels of polymorphism and divergence indicative of a recent common ancestral population. Recent genetic studies,
however, indicate a single refugium in North America compared to several refugia in Europe. Pike are found in rivers, lakes
and weakly saline waters. Variables such as growth and mortality are mainly affected by factors such as temperature, water
transparency, productivity, availability of prey and density of pike and other predators. In choice of habitat pike have been
shown to support the ideal free-distribution theory. The importance of macrophyte habitat in the life history of pike has
been reconfirmed and pike have been shown to be flexible in response to water clarity. Pike are extremely ‘plastic’ in choice
of prey types, prey size and in response to prey behaviour (e.g. they are unaffected by shoal size). Predation by pike not
only affects abundance and biomass of prey (including younger and smaller pike through cannibalism which plays a major role
in population dynamics, other fishes and invertebrates) but also evolution and adaptation of their morphology (in particular
body shape) and behaviours. There appears to be no relationship between stock and recruitment. Recruitment is influenced by
several abiotic factors in lakes and rivers. Pike play a major role in structuring freshwater communities and have been used
in stocking programmes to improve water quality (biomanipulation). Many new concepts have been developed in pike behaviour
in maximizing these stocking programmes both in biomanipulation and fisheries management. Despite many recent advances in
understanding the ecology of pike, particularly at the individual level, developments in quantifying and modelling the role
of pike as a top predator in large ecosystems have been limited, probably due to the difficulties of sampling natural populations.
Guest editors: J. M. Farrell, C. Skov, M. Mingelbier, T. Margenau & J. E. Cooper
International Pike Symposium: Merging Knowledge of Ecology, Biology, and Management for a Circumpolar Species 相似文献