A survey of the spawning of perch (Perca fluviatilis), pike (Esox lucius), and roach (Rutilus rutilus), using artificial spawning substrates in lakes

The development of spawning in perch, pike and roach in Lake Geneva has been studied by means of artificial spawning substrates, laid at different depths, from 1984 to 1993. In Lake Geneva, perch spawned in May. A rise of surface water temperature up to 14 °C stimulated spawning activity while bad weather (surface temperature at 10 °C) induced a spread of the spawning period over more than one month. The spawning period was delayed in years when the mean width of perch egg-ribbons was the largest; this corresponded to the biggest females. At the beginning of the spawning period (early in May), perch preferentially chose a depth of 4 m to spawn. In contrast, at the end of the spawning period, maximum spawning intensity was observed at a depth of 12 m. This phenomenon was more pronounced when water temperature rose above 14 °C in the top 4 m while it remained below 12 °C at a depth of 12 m. Pike spawned at the end of April and at the beginning of May in Lake Geneva. They preferred spruce branches among the different spawning substrates that we tested in Lake Vouglans. When the water temperature increased at the surface of Lake Geneva, pike preferred to lay their eggs on substrates set at 3 m depth where the temperature was cooler than in the surface layer (10.5 °C vs 14 °C). Roach spawned during the last two weeks of May or during the first two weeks of June in Lake Geneva, depending on water temperature. Spawning had generally been spread over a week, but a sudden decrease of water temperature could slow spawning intensity. Roach were able to lay their eggs on natural or synthetic substrates, located 0.5 m below the surface near the shore as well as, at a distance of several hundred metres from the shore. The survival of eggs was always above 90% for perch and roach and generally above 70% for pike.     

Influence of temperature and size of females on the timing of spawning of perch,Perca fluviatilis,in Lake Geneva from 1984 to 1993

Synopsis The influence of temperature and the size of reproducing females on the timing of spawning of perch in Lake Geneva has been studied for 10 consecutive years (1984–1993) by means of artificial spawning substrates. The clutch of perch is an egg ribbon with a width proportional to the size of the reproducing female, so that the size structure distribution of the female population can be estimated from measurements of the width of the egg ribbons. The survey of egg-ribbon size revealed a succession of 3 cycles (period of increasing mean size followed by a sharp decrease) lasting 3, 3 and 4 years which were due to the occurrence of 3 strong year classes born in 1982, 1985 and 1988 respectively. This phenomenon can be explained by the effect of intraspecific predation exerted by strong year classes on the offspring of the 2 following years rather than by fluctuations in the success of reproduction in relation to climatic changes. In Lake Geneva, perch spawn in May. The water temperature exerted only a minor influence on the date of the beginning of the spawning period but had a greater effect on its intensity. A rise in temperature in May stimulated spawning while bad weather decreased spawning intensity. The larger perch had a tendency to spawn later than the small ones. The date of the mid-spawning period was well correlated with the yearly mean width of perch egg ribbons but no correlation could be detected between it and the water temperature.     

Delayed spawning of perch, Perca fluviatilis L., in acidified lakes

The timing of spawning of perch was examined in four acidified lakes (pH 4.4–4.8) and in one circum-neutral lake (pH 6.3) in southern Finland in spring 1987. In three of the lakes, perch started to spawn soon after the ice melt (4–14 degree days > 5° C) and had spawned by the end of May at about 100 degree days > 5° C. In the two most acidified lakes, fish started to spawn later, at 35 and 60 degree days > 5° C, and had spawned in early June, at about 200 degree days > 5° C. The maturing of gonad products was delayed in both males and females.     

The date of spawning in populations of the Common frog (Rana temporaria) from different altitudes in northern England

A series of ponds in the Wear Valley in northern England, ranging in altitude from 46 to 838 m, were visited regularly over a four-year-period, and a record was kept of the dates on which spawn from the Common frog, Rana temporaria , was first seen in each of the ponds. On average. spawning was delayed by six days for every 100 m increase in altitude. The date of spawning at each of the ponds was fairly consistent from year to year; only in 1974 was the date of spawning noticeably different from other years. A theory was proposed which could account for the variation in the date of spawning with altitude and the annual variation in the date of spawning, observed in the present study. It is proposed that frogs from nothern England become sensitive to environmental temperature in the middle of February and emerge in the spring after experiencing a temperature-sum of 106 degree(C)-days. The onset of temperature sensitivity is probably initiated by a circannual endogenous rhythm. The time at which the rhythm switches on the temperature-sensing mechanism in frogs probably varies in different populations, and may well be locally adapted. For spawning to follow emergence, a certain minimum water temperature may be required. In the present study, most frogs in the wild spawned when the water temperature in the ponds was above 7°C, but frogs could spawn at 3·1°C. Alternative theories for the control of emergence and spawning are also discussed.     

Fecundity and reproduction of perch (Perca fluviatilis L.) in Lake Agios Vasilios, Greece

SUMMARY. In Lake Agios Vasilios, male perch become sexually mature during their first year of life whereas females become sexually mature during their second year. The mean absolute fecundity was 8080 eggs; values ranged from 2080 to 28488. The mean relative fecundity was 141 eggs/g body wet weight (ranging from 113 to 201). The absolute increase in weight of gonads is related to the age of the fish. The spawning period is from the middle of March to the beginning of April, at a mean water temperature of 8°C.     

Spatio-temporal distribution pattern of the red band-fish Cepola rubescens Linnaeus at different stages of its life cycle in the northwestern Mediterranean

The larvae of Cepola rubescens Linnaeus, 1766 were collected from May to October with a surface temperature of 17.5°C at the beginning of the spawning. They were widely distributed over the continental shelf and the greatest concentrations were found at stations with depth around 100 m. During all months, most of the larvae were of small size, between 2.0 and 3.0 mm s.l . The juveniles and adults were caught in a wide range of depths, from less than 25 m to about 200 m, and the highest abundance was also found at depths of about 100 m, but no large individuals were found at depths less than 50 m. The catches of the trawling fleet showed a marked seasonality, with maximum values at the end of spring and minimum at the end of autumn and the beginning of winter. This seasonality seems to be related to reproduction since the highest catches were obtained during the spawning period.     

Reproductive ecology of Japanese anchovy off the Pacific coast of eastern Honshu, Japan

Spawning frequency of offshore migrant populations of Japanese anchovy Engraulis japonicus ranged from 0·34 to 0·90, and was higher than that of inshore Japanese anchovy. In addition, spawning frequency of offshore populations varied in response to the sex ratio. They spawned at water temperatures of 5.0, 8.6 and 12.6° C, indicating that the minimum critical water temperature of offshore Japanese anchovy was considerably lower than that of inshore populations. A significant positive relationship was observed between water temperature and relative batch fecundity of offshore Japanese anchovy. Furthermore, water temperature was negatively related to egg size, suggesting a trade-o. between relative batch fecundity and egg size for offshore fish. At the same water temperature, relative batch fecundity of offshore populations was higher than that of inshore ones. The comparison of spawning frequency and relative batch fecundity suggests that offshore Japanese anchovy represent a reproductive ecology by which they spawn more eggs than inshore Japanese anchovy within a certain time period.     

The annual reproductive cycle of the freshwater mussel Dreissena polymorpha Pallas in lakes

Summary The annual development of the gonads of Dreissena polymorpha was studied at three sampling sites in two lakes over 3 and 1 1/2 years, respectively. A resting stage occurred after the last spawning in summer/autumn. Oogenesis (accompanied by multiplying segmentation of the oogonia and early growth processes of its oocytes) restarted in specimens at least 1 year old at low temperatures (below 10° C) during winter and early spring. At one location (Fühlinger See) the onset of the spawning season was correlated with an increase of water temperatures above 12° C. At 2 m depth, two main spawning periods in May and August were normally recognized, the first at temperatures of 12–16° C, the second at 16–21° C. It was clearly demonstrated for the first time in Dreissena polymorpha that the oocytes became mature in successive cohorts within one gonad. A female mussel may spawn several times during the reproductive season. At 9 m depth, the onset of spawning also started at about 12° C; this occurred in late summer, with two spawning periods within 1 month at a temperature range of 12–16° C. At another location (Heider Bergsee) the size of the gonads and the oocytes was reduced during April of both years studied, when food supply was low simultaneously with rapidly rising water temperatures in this shallow lake. There was no spawning period during spring. The major spawning period was delayed until July (temperatures 19–22°C). This shows (1) the synchronizing influence of low winter temperatures on the annual reproductive cycle and (2) a temperature threshold of at least 12° C for the start of the spawning processes. The results are discussed with regard to the geographical limits of further spread of Dreissena polymorpha.     

Hydrological Status of the spawning ground of Acipenser sinensis underneath the Gezhouba Dam and its relationship with the spawning runs

The spawning runs of Chinese Sturgeon (CS; Acipenser sinensis) were observed 37 times below Gezhouba Dam of Yangtze River between 1983 and 2004. Five hydrological factors (water temperature, water level, flow discharge, silt content and current velocity) were monitored on a daily basis at the spawning ground between October and November for 22 consecutive years (1983–2004). The effect of current velocity on the spawning ground at the bottom layer of the river, where CS was spawning for four years, was measured (1996–1999). The authors of this study analyzed the relationship between the five hydrological factors and the respective spawning runs. Twenty-two years of continuous observations indicated that the daily mean values of all the five hydrological factors fluctuated within a certain range when CS was spawning. It was concluded that the optimal values for the hydrological factors during the spawning runs are 18.0–20.0°C for temperature, 14100 m³/s for discharge volume, 42.0–45.0 m for water level above the sea level, and 0.2–0.3 kg/m³ for silt content in the water, wherein the current velocity above the bottom layer to stimulate the fish to spawn should be between 1.0–1.7 m/s. The optimal water temperature might provide an essential precondition for other factors to trigger spawning. As water temperature reaches the optimal values and most of the other parameters are at the brink of deviation from their optimal range of values (water level, current velocity and silt content in the water), CS would begin to spawn. By 2009, when the Yangtze Three Gorges Project, which is located 45 km upstream of the Gezhouba Dam, is completed and begins to operate normally, changes in the downstream water temperature are expected to occur, which may have a negative effect on the development of gonad and the stimulation of spawning of CS; however, the anticipated decrease of the silt content in the water may be considered favorable for the performance of the spawning site.     

Latitudinal gradients in onset date, onset temperature and duration of spawning of roach

Onset date, onset temperature and duration of spawning of roach Rutilus rutilus were related to latitude (40–66° N) and altitude (−1–825 m) based on data from the literature over the whole geographic distribution of roach. Onset date was positively and duration was negatively correlated with latitude, while no correlation was found between onset temperature and latitude. No significant correlations were found between any of the analysed variables of spawning and altitude, probably because most of the analysed populations were below 300 m altitude.     

Influence of environmental conditions on the ovarian cycle and serum chemistry of Cyprinus carpio in the Dal lake, Kashmir (India)

SUMMARY 1. The study presents adaptive and acclimatory changes observed in Cyprinus carpio communis L with respect to ovarian cycle and serum levels of electrolytes, calcium, total proteins and albumin as a consequence of wide temperature and sunshine variation in the natural environment of Dal lake in Srinagar, Kashmir (India).
2. The atmospheric temperatures in Srinagar show well-defined seasonal and diurnal variations. During the period of study, the mean monthly average temperature in summer (June-August) was 24°C whereas in winter (December-February) it fell to 3.6°C. The total hours of sunshine during the winter months were about half of those found in summer.
3. Under local thermal and photo conditions the fish was found to spawn once a year compared to biannual spawning in tropical chmates.
4. A significant decrease was found in serum sodium, potassium and chloride concentrations during the months of January and February when the mean minimum atmospheric temperatures reached −2.5°C and −l.2°C respectively.
5. The serum calcium levels showed a marked increase during the period corresponding to ovarian maturity and spawning of fish.
6. A significant rise in total serum protein concentration was induced by decreased environmental temperatures. Serum albumin levels were found to exhibit a sharp fall coinciding with the spawning period.     

Spawning population characteristics of pike <Emphasis Type="Italic">Esox lucius</Emphasis> L. in Lake Rubikiai (Lithuania)

The aim of the study was to describe the peculiarities of pike spawning in mesotrophic Lake Rubikiai, to determine the spawning population structure and evaluate the influence of some environmental factors on year-class strength formation. The data were collected in April and May (1994–2011). A total of 1586 individuals were caught. The age of pike ranged from 1 to 12 years; 2–5-yearold males (96.0%) and 3–8-year-old females (89.1%) prevailed. The overall sex ratio of females to males was 1:4.1. One-year-old spawning males (26.5–28.5 cm) and two-year-old spawning females (31.5–35.5 cm) constituted 2.1% and 2.6%, respectively. Water temperature during the spawning period was relatively stable, between 4 and 6°C, during March and increased slightly towards 10°C in the middle of April. No correlation was observed between female length and spawning date. Year-class strength did not correlate with the last day of ice presence and the minimal water level at the end of spawning (WL_min), but statistically significantly negatively correlated with the maximum water level at the beginning of spawning (WL_max) and the difference between WL_max and WL_min. The mean annual survival rate for pike (aged ≥2) was 0.74 and the mean annual instantaneous mortality rate was 0.45.     

Body temperature and foraging behaviour of the Eurasian otter (Lutra lutra), in relation to water temperature

The effects of water temperature (T_w) on core body temperature (T_b) and foraging behaviour were studied in four free-ranging and one captive otter Lutra lutra in NE Scotland. The free-ranging animals were observed in and around two freshwater lochs, and measurements were made of T_w (2–16°C), T_b at the beginning and end of swimming bouts, lengths of swimming bouts, and dive times and intervals. T_b ranged from 35.9 to 40.4°C (mean 38.1°C). At the beginning of a period of activity and of a swimming bout. T_b rose significantly; during swimming it fell at a rate of 2.3°C/h, independent of T_w. Dive intervals were longer in colder waters, but this was probably due to other, seasonal environmental changes (perhaps water level). T_w had no significant effect on length of swimming bouts or on T_b. Although otters entered water with increased T_b, they exited when T_b was not significantly different from the mean resting T_b. The data suggest that otters maintain T_b irrespective of T_w, by increasing it before entering water, then either exiting at a given T_b, or at an earlier time determined by other environmental conditions.     

Spawning of the Australian freshwater fish Murray cod, Maccullochella peeli (Mitchell), in earthen ponds

Murray cod, Maccullochella peeli , spawned naturally in earthen ponds in four consecutive breeding seasons. Spawning was induced by a rise in water temperature up to or above 20°C during spring, however, an associated rise in water level was not required. Response to the temperature rise was more rapid later in the season and increasing daylength may have also been involved. Eggs were deposited on firm substrates at depths between 0·5 and 2·3 m, and hollow pipes, logs or similar structures were not necessary to provide suitable sites for egg deposition. At two spawning sites, mud had been removed from the pond banks by the broodfish and the eggs attached to the exposed clay. At one spawning site, a male cod was observed protecting the eggs during incubation.
It is suggested that high survival of cod larvae will only occur when a significant rise in water level coincides with the breeding season and as a consequence the control of water levels for irrigation and flood mitigation purposes during spring and summer has affected Murray cod to a greater extent than golden perch, Macauaria ambigua , which spawns only after a substantial rise in water level, when conditions are more favourable for larval survival.     

Regional and interannual variations in spawning activity of Pacific saury Cololabis saira during northward migration in spring in the north-western Pacific

Regional and interannual variations in spawning activity of Pacific saury Cololabis saira during the northward migration in spring were investigated for 1995–1997 in the north-western Pacific. Only females with a large body size (≥270–290 mm knob length) appeared to spawn. Almost all females in this cohort were actively spawning in a region of sea surface temperature ( T _SS) >18° C, the proportion of active spawners appeared positively related to T _SS in a region of 13° C < T _SS≤ 18° C, and no females were spawning in the region of T _SS≤13° C. Although this relationship between spawning activity and T _SS was common in all years, the distribution of females in the large-size cohort among the regions varied interannually. Consequently, the proportion of active spawners among adult females showed considerable interannual variations.     

Spatial aspects of reproduction in buffalo sculpin,Enophrys hison

Synopsis The spatial distribution and parental care of demersal egg masses of buffalo sculpin (Enophrys bison) were studied at 11 areas in Puget Sound, Washington, during 1972–1973. Adult buffalo sculpin inhabited rock and rock-sand habitats at depths from the intertidal to minus 20 m throughout the year, but 84% of all spawn clusters were found at depths between –1 m and +1 m within localized rocky areas. Areas used for spawning were exposed to strong tidal currents and other water movements. A single male fish guarded and fanned spawn, but eggs were temporarily deserted when less than about 1 m of water covered the spawning site. The cyclical nature of male desertion, behavior of spawn predators, and spawn mortality due to physical factors while emergent suggest several possible advantages to low intertidal spawning. These advantages include spatial and temporal escape from marine predators by embryos, time for the tending parent to forage, and optimal physical conditions for embryonic development.     

Preliminary observations on the spawning conditions of the European amphioxus (Branchiostoma lanceolatum) in captivity

Members of the subphylum Cephalochordata, which include the genus Branchiostoma (i.e. amphioxus), represent the closest living invertebrate relatives of the vertebrates. To date, developmental studies have been carried out on three amphioxus species (the European Branchiostoma lanceolatum, the East Asian B. belcheri, and Floridian-Caribbean B. floridae). In most instances, adult animals have been collected from the field during their ripe season and allowed (or stimulated) to spawn in the laboratory. In any given year, dates of laboratory pawning have been limited by two factors. First, natural populations of these three most studied species of amphioxus are ripe, at most, for only a couple of months each year and, second, even when apparently ripe, animals spawn only at unpredictable intervals of every several days. This limited supply of living material hinders the development of amphioxus as a model system because this limitation makes it more difficult to work out protocols for new laboratory techniques. Therefore we are developing laboratory methods for increasing the number of amphioxus spawning dates per year. The present study found that a Mediterranean population of B. lanceolatum living near the Franco-Spanish border spawned naturally at the end of May and again at the end of June in 2003. Re-feeding experiments in the laboratory demonstrated that the gonads emptied at the end of May refilled with gametes by the end of June. We also found that animals with large gonads (both, obtained from the field and kept and fed at the laboratory during several weeks) could be induced to spawn in the laboratory out of phase with the field population if they were temperature shocked (spawning occurred 36 hours after a sustained increase in water temperature from 19 degrees C to 25 degrees C).     

Adaptive and evolutionary significance of a reproductive thermal threshold in Barbus barbus

From 1989 to 1996, barbel in the River Ourthe started spawning under variable environmental conditions, except for water temperature. Each year, spawning was initiated when water daily minimum temperature reached or exceeded 13·5° C. Any decrease of temperature below this value later in the spawning period caused spawning to be suspended. Analyses of offspring growth provided evidence that 13·5° C was the value below which 0+ barbel stop growing. It was hypothesized that barbel trade off the lower initial probability of survival against a larger size at the onset of winter. To test empirically for this hypothesis, the adequacy of alternative—theoretical—strategies associated with other thermal thresholds (12, 15·0, 17·1 and 20·2° C) was modelled with respect to: (1) the feasibility of spawning (inhibition of sexual maturation by a decreasing photoperiod); (2) the impact of the temperature on embryonic development; (3) the effect of water level variations on the integrity of spawning grounds until the emergence of larvae; (4) the size of the offspring at the onset of winter. On an 8-year (1989–1996) average, the present spawning strategy would have produced a higher recruitment than alternative strategies (relative adequacy of 33·23, 85·64, 93·17 and 17·62%, respectively). However, alternative strategies would have produced better annual scores on five of eight occasions in the River Ourthe environment, and a better overall score in environments 1·5 or 3·5° C warmer than now. The consistency of the thermal threshold over years, despite a low selection pressure by the environment, was interpreted as the expression of a phenotypic mechanism (thermal homing) promoting the selection of the lowest efficient thermal threshold, and enabling breeders to relay to the next generation some form of thermal stability in a variable environment.     

Behavioural studies on the lesser sandeel Ammodytes marinus (Raitt) III. The effect of temperature on activity and the environmental control of the annual cycle of activity

The behaviour of the lesser sandeel, Ammodytes marinus (Raitt), has been investigated at 5, 10 and 15° C, using a photographic method of recording activity. The activity patterns at 10 and 15° C were very similar, there being a high level of swimming activity during the light period, which fell to a low level at 5° C. It was also lower at 10° C at the end of the experiment than at the beginning and it is suggested that this might have been due to an increase in the fat contents of the fish. The feeding rate of the fish was measured and showed a Q ₁₀ of 2.08 for the temperature range 5–15° C. The annual cycle of activity of A. marinus is discussed in relation to seasonal changes in food availability, light and temperature, and in the fat content of the fish. It is concluded that after spawning in the December–January period the fish remain buried in the sand until April, because of the limiting effect on swimming and feeding activity of the environmental factors in the intervening period. The proportion of fish available for capture at the start of the fishery in April is related mainly to temperature, but food (as measured by numbers of copepods) light intensity and photoperiod are by then increasing rapidly. After July the fishery ceases and it is thought that this is because the fish have entered an overwintering stage, during which they remain buried in the sand. This phase is also thought to be associated with the maturation of the gonads in readiness for the winter spawning. The factors causing the fish to enter this stage are as yet undetermined but may be related to the attainment of a certain level of fat content.     

The effect of ambient temperature on body temperature and on ultrasonic behaviour in litters of albino laboratory mice deprived of their mothers

Litters of mouse pups of various ages when deprived of their mother and kept for one hour at ambient temperatures of 3°C, 12°C and 22°C lose heat less rapidly than pups isolated individually at similar temperatures. The litters are able to maintain constant body temperatures of 35–37°C by day 8 at 22°C, by day 19 at 12°C and by day 21 at 3°C. Very little ultrasound is detected from litters of any age up to 21 days at 22°C while at 12°C ultrasound is mainly detected from pups of 4 and 6 days; very few calls are produced by older pups at this temperature. Considerably more calls are emitted at 3°C than at either of the two higher temperatures. At 3°C the total number of calls emitted during the hour-long exposure period varied markedly with age. There were two peaks of calling, one on day 6 and the other on day 16. The temporal pattern of calling throughout the hour-long exposure period at 3°C was similar in pups of 4 and 6 days and in pups of 8, 10, 12, 14 and 16 days, but differed between these two groups. In the younger group of pups the rate of calling rose to a peak and then decreased to zero as the pups became comatose; in the older pups the rate of calling was low initially then either rose throughout the rest of the hour or rose to a high level that was maintained. It is suggested that the various patterns of ultrasonic calling can be associated with the physiological development of mouse litters.