Characteristics of the spawning migrations of brown trout, Salmo trutta L., and rainbow trout, S. gairdneri Richardson, in Great Lake, Tasmania

Upstream spawning migrations of mature brown trout, S. trutta , and rainbow trout, S. gairdneri , were studied in Liawenee Canal, Great Lake from 1949 to 1985. Brown trout migrations normally occurred from early April to mid-May and rainbow trout from late August to early November. In 1983, 16 425 brown trout and 1338 rainbow trout passed through a fixed upstream diversion trap. Brown trout spawning migrations occurred predominantly over the temperature range 6–10° C, while rainbow trout migrated predominantly over the range 5–11° C. Migrations peaked at water temperatures of 7.6°C (males) and 7.8°C (females) for brown trout, and 8.3°C (males) and 9.6°C (females) for rainbow trout. Rainbow trout migrations occurred at high flow conditions and were positively correlated with canal flow increases, while brown trout migrated under low canal flow. Mean length, weight and condition of rainbow trout of both sexes decreased significantly during migrations. Female brown trout decreased in weight and condition but not in length; male brown trout did not change in condition despite decreases in both length and weight during migrations. Overall sex ratio was 2:1 (female:male) for both species, with the relative proportion of male fish decreasing as migrations progressed. Age composition changed during migrations; dominant age classes were 3 < 4 < 5 + years for both species. Comparison of length, weight, condition and age revealed minor changes during the 37-year period 1949–1985.     

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.     

Intra- and inter-specific variations in egg survival and brood development time for Austrian populations of Gammarus fossarum and G. roeseli (Crustacea: Amphipoda)

SUMMARY. 1. Egg survival (ES, percentage of eggs hatched in vitro ), reproductive success (RS, percentage of live young released from the brood pouch) and brood development lime ( d , days) in four populations of Gammarus fossarum and two populations of Gammarus roeseli were studied, in the laboratory at water temperatures of 2.0–26.1°C. Intraspecific differences between populations were not significant, but interspecific differences were found between the two species.
2. In natural stream populations, the reproductive period of G. fossarum lasted from December to September, that of G. roeseli from March to September.
3. In the experimental temperature range 2–26°C, 73% of the total number (771) of G. fossarum females and 69% of 469 G. roeseli females were ovigerous. Of these, 45% of G. fossarum and 43% of G. roeseli females successfully released live young from their brood pouches.
4. For G. fossarum , the optimum temperatures were 11.4°C for ES, where 76% of the eggs hatched, and 11.8°C for RS, where 77% of the females released live young from their brood pouches. For G. roseli , the optimum temperatures were 13.5°C for ES (51% hatched) and 14.0°C for RS (76% released). Over 50% of eggs hatched at temperatures of 3.6–19.2°C in G. fossarum and at 1 1.9–15.1°C in G. roeseli . Development time increased from 12 days at 21.9°C to 251 days at 2.0°C in G. fossarum , and from 10 days at 24.1°C to 212 days at 4.1°C in G. roeseli .
5. interspecific differences between the effects of water temperature on ES, RS and d are used to explain the different distributional patterns of G. fossarum and G. roeseli in central European running water systems. assuming that other physico-chemical variables are suitable for both species.     

Aspects of the spawning biology of the Brazilian sardine, Sardinella brasiliensis (Steindachner, 1879), (Clupeidae)

Biological data, size frequency distribution of intraovarian oocytes, maturity indices and histological observations of the gonads were used to assess the spawning cycle of S. brasiliensis , sampled September 1981–August 1982 throughout the main fishing area off the Brazilian coast (22°S to 28°S). Post-ovulatory follicles are described and classified, and the incidence of mature females displaying these structures was calculated. The main findings were (a) spawning occurred during the spring and summer with a maximum in December and January; (b) spawning occurred throughout the area studied; (c) spawning was fractional; (d) average batch fecundity was 26 000 oocytes per female, or 393 eggs g⁻¹; (e) spawning frequency reached values of approximately 50% during the spawning peak, but was sensibly lower during the other months of spawning activity.     

Effect of temperature on the hatching time of eggs of Ephemerella ignita (Poda) (Ephemeroptera:Ephemerellidae)

SUMMARY. Eggs of Ephemerella ignita (Poda) were kept at eight constant temperatures (range 5.9–19.8°C) in the laboratory. Over 85% of the eggs hatched in the temperature range 10.0–14.2°C but the percentage decreased markedly to 39% at 5.9°C and 42% at 19.8°C. Hatching time (days after oviposition) decreased with increasing water temperature over the range 5.9–14.2°C and the relationship between the two variables was well described by a hyperbola. Therefore, the time taken for development was expressed in units of degree-days above a threshold temperature. Mean values (with 95%CL) were 552 (534–573) degree-days above 4.25°C for 10% of the eggs hatched, 862 (725–1064) degree-days above 3.57°C for 50% hatched and 1383 (1294–1486) degree-days above 3.14°C for 90% hatched. These values can be used to predict hatching times at temperatures below 14.68°C for 10% hatched, 14.54°C for 50% hatched and 14.45°C for 90% hatched. At higher temperatures, the hatching time and the number of degree-days required for development both increased with increasing temperature. Equations were developed to estimate the number of degree-days required for development at these higher temperatures.
Eggs were also placed in the Wilfin Beck, a small stony stream in the English Lake District. Maximum and minimum water temperatures were recorded in each week and the summation of degree-days was used to predict the dates on which 10%, 50% and 90% of the eggs should have hatched. There was good agreement between these estimates and the actual hatching times. Only 10–15% of the eggs hatched between October and late February with most of the eggs hatching in March, April and May. Nymphs hatching in October and November probably did not survive the winter.     

Reproductive biology of the threatened golden galaxias Galaxias auratus Johnston and the influence of lake hydrology

Golden galaxias Galaxias auratus (31–235 mm fork length, L _F) were collected monthly from littoral habitats in Lakes Crescent and Sorell, Tasmania, Australia, between July 2000 and December 2002. Spawning habitats were identified and monitored in both lakes, and surveyed in Lake Crescent. Trends in gonado-somatic indices and reproductive stages of development indicated that gonad development in both sexes begins in midsummer and peaks in late autumn to early winter. Males mature at smaller sizes (50% at 52 mm L _F) than females (50% at 76 mm L _F), larger individuals are predominately females (95% of fish ≥138 mm L _F), and overall male to female ratios are female biased ( c . 1:2). Spawning occurs late autumn to early spring (water temperatures = 1·4–9·7° C) with peaks in spawning activity in winter (mean water temperatures <5° C). Demersal adhesive eggs ( c. 1·5 mm diameter) were found on cobble substrata ( c. 20–250 mm diameter) in littoral areas ( c. 0·2–0·6 m deep) and fecundity of fish 71–181 mm L _F ranged from 619 to 14 478 eggs. The rate of change in water level over the 20 days prior to monthly sampling was important in explaining the occurrence of spent fish and this accounted for temporal differences in spawning between the populations. Lake hydrology influences the reproductive cycle of G. auratus by possibly providing a stimulus for spawning and it controls the availability of spawning habitat in Lake Crescent. Seasonal hydrological cycles ( i.e. rises during late autumn to winter) and a minimum water level of 802·20 m Australian Height Datum in Lake Crescent during autumn (above which littoral areas of cobble substratum are inundated) are critical to G. auratus populations.     

Effect of salinity and temperature on the growth of yearling Arctic cisco (Coregonus autumnalis) of the Alaskan Beaufort Sea

The growth of 1-year-old Arctic cisco ( Coregonus autumnalis ) was monitored under laboratory conditions for fish acclimated to one of two temperatures (5 and 10° C) and one of five salinities (6, 12, 18,24, 30‰). Fish were maintained for 43 days at rations of 3% wet body weight per day at 5° C and 5% wet body weight per day at 10° C, with rations adjusted for weight gain every 7–12 days. Fish increased 9–11% in length and 55–71% in weight at 5° C, and 23–27% in length and 141–161% in weight at 10° C. Length and weight increased linearly over 43 days. There was a statistically significant effect of temperature on growth but no statistically significant effect of salinity. Higher growth rates at 10° C were partially attributable to significantly greater gross conversion efficiency at the higher temperature. Over the course of the experiment, the condition (weight per unit length) of all fish increased by 3·2 to 63·6% at 5° C and by 5·6 to 46·0% at 10° C. There was no discernible effect of salinity on condition at either temperature. These results demonstrate that, with salinity acclimation and high food ration, 1-year-old Arctic cisco can grow at equivalent rates across salinities ranging from 6 to 30‰. The ecological implications of the results are discussed.     

Influence of temperature on the spatial distribution of first spawning dates of the common frog (Rana temporaria) in the UK

Between 1998 and 2007, the UK Phenology Network collected nearly 70 000 records of the first spawn dates of the common frog Rana temporaria . Annual national mean dates varied by more than 2 weeks and were closely related to January–March temperatures. A 1 °C increase in Central England Temperature advanced national mean spawning by 5.1 days. The temporal pattern of spawning records varied between years; sometimes unimodal in form, sometimes multimodal, seemingly associated with steady or erratic rises in spring temperatures, respectively. Spatial patterns of frogspawn were similar in different years, the earliest records occurring in the southwest with records progressively later in the north and east. On average, 100 km of eastwards progression took 7.4 days and 100 km of northwards progression took 4.7 days. A composite map for the 1998–2007 period is constructed and compared with an earlier published map based on data 60 years previously. The similarity and dissimilarity of these two maps is discussed; the general progression pattern of frogspawn phenology is similar but an advance of a 10-day contour category is apparent. We anticipate further advances of frog spawning dates in the future and an increase in the numbers of pre-January 1 records of frog breeding.     

Seasonal changes in energy and the energy cost of spawning in Gulf of Alaska Pacific cod

In the Gulf of Alaska, adult Pacific cod exhibited an annual cycle of condition, gonad index and liver index in which maximum values occurred in ripe fish in March and minima in July. About 30–31 % of prespawning stored energy was expended during the spawning effort. The energy associated with spawning derived from liver (24% and 18%), somatic tissue (22% and 33%) and gonad (53% and 48%) for females and males, respectively. Liver index and gonad index at the time of sampling were directly related in females, but in males gonad index was best related to liver index 1–3 months earlier.
The Pacific cod is very similar to the Atlantic cod in terms of energy cycling, maximum gonad sizes, energy expended during spawning and gonadal contribution to energy expenditure. However, in Pacific cod, somatic tissue contributes markedly to energy expended during reproduction. The Pacific cod cod differs from the walleye pollock with respect to gonad index (13% and 20%ν. 20% and 8% for females and males, respectively), spawning weight loss (25%ν. 38%), liver energy loss during spawning (71%ν. 55%) and energy cost of spawning.     

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.     

Behavioural thermoregulation by subyearling fall (autumn) Chinook salmon Oncorhynchus tshawytscha in a reservoir

This study investigated behavioural thermoregulation by subyearling fall (autumn) Chinook salmon Oncorhynchus tshawytscha in a reservoir on the Snake River, Washington, U.S.A. During the summer, temperatures in the reservoir varied from 23° C on the surface to 11° C at 14 m depth. Subyearlings implanted with temperature-sensing radio transmitters were released at the surface at temperatures >20° C during three blocks of time in summer 2004. Vertical profiles were taken to measure temperature and depth use as the fish moved downstream over an average of 5·6–7·2 h and 6·0–13·8 km. The majority of the subyearlings maintained average body temperatures that differed from average vertical profile temperatures during most of the time they were tracked. The mean proportion of the time subyearlings tracked within the 16–20° C temperature range was larger than the proportion of time this range was available, which confirmed temperature selection opposed to random use. The subyearlings selected a depth and temperature combination that allowed them to increase their exposure to temperatures of 16–20° C when temperatures <16 and >20° C were available at lower and higher positions in the water column. A portion of the subyearlings that selected a temperature c. 17·0° C during the day, moved into warmer water at night coincident with an increase in downstream movement rate. Though subyearlings used temperatures outside of the 16–20° C range part of the time, behavioural thermoregulation probably reduced the effects of intermittent exposure to suboptimal temperatures. By doing so, it might enhance growth opportunity and life-history diversity in the population of subyearlings studied.     

The reproductive biology of Common frog (Rana temporaria) populations from different altitudes in northern England

The study investigated the ecophysiological differences between populations of the Common frog( Rana temporaria L.) from different altitudes in northern England. Frog embryos in upland northern ponds experience very low temperatures during the period of embryonic development. These embryos were found to have a lower lethal limit for 50% normal development of2–8 °C, compared with3–8 °C for lowland embryos. These values are below most of the lower limiting temperature estimates previously obtained for R. temporaria . Embryos from upland ponds developed faster at low temperatures than embryos from lowland ponds. This may be an adaptation to the shorter growing season and lower temperatures at higher altitudes. Upland female frogs were found to be shorter and produced fewer eggs than lowland females. The differences found between lowland and upland frogs are discussed in terms of their potential adaptive significance.     

Seasonal changes in the common dab, Limanda limanda (L.) in Isle of Man Waters

Otolith accretion was greatest in summer when opaque bands were laid down and slowest in winter when hyaline rings were formed. Food intake was minimal in winter and maximal in summer. Liver weight was high in summer and winter and low in spring after spawning. Growth in length was higher in summer than winter. Gonad weight was greatest in winter for both sexes. Spawning occurred from February to April. After spawning males recovered earlier than females and testes ripened earlier than the ovaries. From winter to summer, the sea temperature increased from 7.5–13.0°C; the day length from 7–17h; and the salinity varied from 34.07−34.36%.     

Effect of temperature on the biology of Creontiades dilutus (Stål) (Heteroptera: Miridae)

The egg and nymphal development, fecundity and survival of the green mirid, Creontiades dilutus were examined at a range of temperatures and a modified day-degree model fitted to the data. Day degree (DD) requirements for egg and nymphal development, and threshold temperatures were calculated from the fitted lines. Female fecundity and longevity, egg and nymphal development, and survival of C. dilutus were significantly influenced by temperature. Eggs and nymphs failed to complete development at temperatures below 17 and at 38°C. Females also failed to produce any eggs at 11 and 38°C. The optimum temperature range for female fecundity was found to be 26–32°C. The optimum temperature for the development of eggs was calculated from the model as 30.5°C and for nymphs as 31.5°C. The threshold temperature for development was 15.8°C for egg and 15.1°C for nymph; 69.4 and 156.7 DD were required for completing the egg and the nymphal development, respectively. At the optimum temperature, it was estimated that development from egg to adult took 15 days. Survival was highest at 26°C for eggs and at 30–32°C for nymphs.     

Laboratory studies of egg development and diapause in Isoperla obscura (Plecoptera) from a mountain stream in Norway

SUMMARY 1. A laboratory study of egg development of the stonefly Isoperla obscura (Zetterstedt) collected from the stream Flybekken (southern Norway, 61°25'N, 8°48'E, 1373 m a.s.l.) showed a short diapause followed by a prolonged period of postdiapause quiescence.
2. Diapause occurred over a wide range of temperatures (−20°C to +8°C), but 0–1°C was the most favourable for fast diapause development and successful hatching. Diapause development required temperatures below 12°C, but sub-zero diapause temperatures increased mortality during the postdiapause phase, as well as reducing hatching success.
3. The threshold for initiation of postdiapausal development was about 1–2°C. Development rate increased and variation in development time decreased at higher water temperatures. These may be important characteristics to ensure seasonal and geographical synchrony of development in individual populations. Low postdiapausal temperatures were unfavourable, despite a subsequent increase in water temperature. No response to postdiapausal photoperiod was detected.
4. The results agreed well with conditions noted in the natural environment, and with the abundance of this species at high altitudes and latitudes in Fennoscandia. Nevertheless, Isoperla obscura also occurs in streams in the maritime parts of western Norway. The results of the present study suggest that egg development in these populations will prove to be different.     

Thermoregulatory behaviour, diel activity and the relationship of spontaneous locomotor activity to temperature in the sea raven, Hemitripterus americanus (Gmelin)

Twelve sea ravens, Hemitripterus americanus , were tested individually for three day periods in electronic shuttleboxes to measure their preferred and avoided temperatures, diel activity pattern and relationship of activity to temperature. The fish avoided temperatures below 9°C or above 25°C, preferring temperatures with a central tendency of 15–17°C. The fish were primarily nocturnal, being more active at night than by day. Locomotor activity increased eightfold between 10 and 20°C, but exhibited an anomalous decrease between 14 and 18°C, corresponding to the preferred-temperature zone, characteristic of maximal summer temperatures in the natural habitat.     

Thermal ecology of the mudskippers, Periophthalmus koelreuteri (Pallas) and Boleophthalmus boddarti (Pallas) of Kuwait Bay

The annual range of body temperatures (14–35°C) of emergent mudskippers are substantially less than that of air temperatures (10–42°C) as a result of behavioural thermoregulation. In winter, low surface temperatures are avoided by remaining in burrows. Newly emerged mudskippers then bask until body temperatures rise above 14°C before they move onto the mud. In summer, body temperatures are kept lower than ambient by selecting areas where evaporative cooling is high. Body temperatures generally match those of wet mud, which can be 7°C lower than air shade temperatures. The smaller, more terrestrial, Periophthalmus koelreuteri have body temperatures which are mainly lower in summer and higher in winter than Boleophthalmus boddarti .     

THE EFFECT OF TEMPERATURE ON EGGS AND IMMATURE STAGES OF CULEX ANNULIROSTRIS SKUSE (DIPTERA: CULICIDAE)

Abstract
No immature stages of Culex annulirostris were found during field sampling in 1979–1980 when the average water temperature was < 17 °C; they reappeared when the average water temperature was 19 °C and reached the peak density (mean 107 immatures/cylinder) at 26.5 °C.
The effect of 6 temperatures (15–40°C) on egg hatching, development and survival of the immature stages of Cx annulirostris in the laboratory showed that at 15 and 40°C, eggs failed to hatch and larvae died in the first instars. The optimum temperatures for egg hatching and the survival of immature stages were 25 and 30°C. At these temperatures, 85 and 82% respectively of egg rafts hatched, the mean number of larvae per raft was 258 ± 9.8 and 260 ± 11.4 with immature survival of 83.5 and 79.0% respectively. Mean time to hatch at 20–35°C ranged from 1.2 d (35°C) to 2.9 d (20 °C). Developmental times from first instar to adult ranged from 7.1 d (35 °C) to 25.2 d (20 °C). The threshold for development of the immatures was 15.6 ± 2.5°C and the thermal constant was 142.9 ± 26.5 day—degrees (incubation temperatures 20–35°C). At less suitable temperatures of 20 and 35 °C, hatching (57.5 and 45%), number larvae per raft (mean 139.8 ± 9.8 and 102.6 ± 14.2) and survival were low.     

Termination and reinduction of reproductive diapause by photo-period and temperature in males of the grasshopper, Oedipoda miniata

ABSTRACT. Previous publications have demonstrated that O.miniata adults exhibit an aestival reproductive diapause during the dry summer in Israel; females do not lay and males show only little mating behaviour. It was also reported previously that photoperiod and temperatures corresponding to autumn in Jerusalem terminate diapause and induce intense male mating behaviour, whereas continuous illumination and high temperatures maintain diapause. In the present study we used mating behaviour as an indicator for investigating the effects of several photoperiod—temperature combinations on reproductive diapause in O.miniata males. Mating behaviour was induced and diapause terminated under the following conditions: LD 10.5:13.5, T = 38-27°C (the temperatures during the photophase and scotophase, respectively); LD 12:12, T=38–27°C; LD 12:12, T=26–13°C; LD 14:10, T = 26–13°C. In contrast, diapause was maintained under LD 14:10, T = 38–27°C and under LL with high but variable temperatures. In further experiments males that were already sexually active, and which had been kept under LD 12:12, T = 38–27°C, were transferred to LL with high variable temperatures. Similarly, postdiapause males which had been kept under LD 14:10 and T=26–13°C were transferred to T = 38–27°C without changing the photoperiod. In both instances mating behaviour declined, then disappeared, thus reinduction of the diapause occurred under such conditions which previously were found to maintain diapause. O.miniata is therefore a 'short day' and/or 'low temperature' insect. This is the first report on complete control of photoperiod—temperature over aestival reproductive diapause and its reversibility in a male insect.     

Growth in the crayfish Austropotamobius pallipes (Crustacea: Astacidae)

SUMMARY. The growth of Austropotamobius pallipes was studied in the River Ouse during 1976–78. Growth of mature crayfish (>2.5 cm carapace length) was followed by determining the relationship between the growth increment at moult and premoult carapace length, together with the frequency of moulting of different categories of crayfish. These data are supplemented by the recapture of marked individuals and the measurement of crayfish held in corves in the river. Growth was limited to the period May–October when water temperatures exceeded 10°C. Growth rates of male and female crayfish are similar until maturity is reached, thereafter males moult twice per year and the majority of females moult once. No crayfish in excess of 3.7 cm carapace length has been observed to moult more than once per year. Growth of juveniles (<2.5 cm carapace length) was estimated from size frequency distributions constructed from regularly taken samples. Growth rates of juveniles showed great variation both between and within year classes. In the hot dry summer of 1976, juveniles exhibited faster growth rates (instantaneous growth rates (G) for 0+ and 1 + crayfish were 0.029 and 0.013 mg mg⁻¹ day⁻¹. respectively) than in other years. Laboratory experiments on the effect of temperature on the growth rate of 0 + crayfish were undertaken; for crayfish at 15°C. G = 0.0138 (0–53 days) and at 10°C, G = 0.0003 (0–90 days). Crayfish held at 10°C failed to undergo a single successful moult. At 20°C crayfish exhibited exponential growth over the first 40 days, with G = 0.0189. declining thereafter to G = 0.012 (40–90 days).