Growth-independent effects of a fluctuating thermal regime on the life-history traits of the Japanese medaka (Oryzias latipes)

Abstract –  Temperature fluctuation has been shown to affect somatic growth rates and metabolic functions of fish, but little is known about the effects of fluctuating temperatures on life-history traits. We examined these effects on female Japanese medaka ( Oryzias latipes ) reared from hatch to maturity at two mean temperatures (27 and 30 °C) with diel temperatures either held constant or allowed to fluctuate ±5 °C. Feeding regimes were manipulated to equilibrate medaka growth rates in all treatments. Age and length at maturity decreased as a result of thermal fluctuation, whereas there was no effect of temperature fluctuation on the proportion of fish attaining maturity or on the number of eggs produced by a mature female. We hypothesise that short-term high temperatures associated with temperature fluctuation decreases development time, whereas reduced energy conversion efficiency at higher temperatures does not allow for increased egg production.     

Determination of the optimal water temperature for the culture of juvenile dusky kob Argyrosomus japonicus Temminck and Schlegel 1843

The effects of temperature on growth, food-conversion ratio (FCR) and feeding intensity of juvenile dusky kob Argyrosomus japonicus (23.7±2.6 g fish⁻¹) were assessed over the temperature range 17.5–28.5 °C in a 42-day growth trial. Growth increased with increasing temperature up to an optimum after which it declined. Specific growth rates were 2.05% and 1.2% day⁻¹ for the fastest (25.3 °C) and the slowest (17.5 °C) treatments respectively. Food-conversion ratio peaked at a lower temperature than growth. Optimal (0.72 kg kg gain⁻¹) and least efficient (1.40 kg kg gain⁻¹) FCR were found at 21.7 and 17.5 °C respectively. Feeding intensity was linearly related to temperature within the range of 17.5–28.5 °C. These results corresponded to the thermal preference (25–26.4 °C) and natural temperature distribution (12–28 °C) of South African dusky kob. Determination of the temperature range that does not limit growth is a prerequisite to assess the relationship between growth and environmental variables such as light intensity, feeding regime and stocking density. Consequently, experiments to determine the effects of these environmental variables on growth and aquaculture potential of dusky kob should be conducted at 24–26 °C.     

Diurnal variation in thermal environment experienced by salmonids in the North Pacific as indicated by data storage tags

Eight temperature-recording data storage tags were recovered from three salmonids in Alaska (pink and coho salmon and steelhead trout) and five chum salmon in Japan after 21–117 days, containing the first long-term records of ambient temperature from Pacific salmonids migrating at sea. Temperature data imply diel patterns of descents to deeper, cooler water and ascents to the surface. Fish were found at higher average temperatures at night, with narrower temperature ranges and fewer descents than during the day. Fish tagged in the Gulf of Alaska were at higher temperatures on average (10–12°C) than chum salmon tagged in the Bering Sea (8–10°C). Chum salmon were also found at a wider range of temperatures (−1–22°C vs 5–15°C). This is probably related both to the different oceanographic regions through which the fish migrated, as well as species differences in thermal range and vertical movements. Proportions of time that individual fish spent at different temperatures seemed to vary among oceanographic regions. Steelhead trout may descend to moderate depths (50 m) and not be limited to the top few metres, as had been believed. Japanese chum salmon may seek deep, cold waters as they encounter warm surface temperatures on their homeward migrations. Temperature data from all fish showed an initial period (4–21 days) of day and night temperatures near those of sea surface temperatures, suggesting a period of recuperation from tagging trauma. A period of tagging recuperation suggests that vertical movement data from short-term ultrasonic telemetry studies may not represent normal behaviour of fish. The considerable diurnal and shorter-term variation in ambient temperatures suggests that offshore ocean distribution may be linked more to prey distribution and foraging than to sea surface temperatures.     

Challenge studies of European stocks of redfin perch, Perca fluviatilis L., and rainbow trout, Oncorhynchus mykiss (Walbaum), with epizootic haematopoietic necrosis virus

A challenge model for comparison of the virulence of epizootic haematopoietic necrosis virus (EHNV) to European stocks of redfin perch, Perca fluviatilis L., and rainbow trout, Oncorhynchus mykiss (Walbaum), was tested. The model investigated intraperitoneal (IP), bath and cohabitation routes at 10, 15 and 20 °C for 5–6 g fish and 15 °C for 20 g perch. In the IP challenges of perch, significant mortality occurred at 15 °C and 20 °C. In challenge trials for rainbow trout, significant mortalities were observed in IP and bath challenges at 20 °C. The mortality observed in IP challenged 20 g perch was not significantly different from that recorded for 6 g fish challenged IP. No significant mortality was observed in any other treatment groups. Re-isolation of ranavirus was confirmed by IFAT and was consistently associated with dead or moribund fish in the trial groups challenged with EHNV. The findings indicate that EHNV does not pose a high risk for wild perch and trout populations in Europe by natural exposure. Mortality appears to be primarily a function of environmental factors, with temperature playing an important role, and not just the presence of the virus in the fish.     

Temperature and salinity tolerances of yellowfin sea bream, Acanthopagrus latus, at different salinity and temperature levels

Abstract Yellowfin sea bream Acanthopagrus latus (Houttuyn) (0.98 ± 0.27 g) were examined for temperature and salinity tolerances at nine different environmental regimes (0.3, 15 and 33 ppt combined with 10, 25 and 32 °C), in which the fish were subjected to gradual and sudden changes in temperature and salinity respectively. The 50% CTMax (critical thermal maximum) and the UILT (upper incipient lethal temperature) were in the range of 34.8–38.2 °C and 32.8–36.4 °C respectively. The 50% CTMin (critical thermal minimum) and the LILT (lower incipient lethal temperature) were in the ranges of 4.9–9.4 °C and 7.1–17.6 °C respectively. The 50% CSMax (critical salinity maximum) and the UILS (upper incipient lethal salinity) were in the ranges of 54–69‰ and 9–44‰, respectively. The fish at lower temperature (10 °C) and salinity of 33‰ tolerated temperature as low as 6 °C when the temperature was decreased gradually. The fish at 33 and 15‰ and lower temperature (10 °C) tolerated salinity as high as 66–67‰, whereas those at freshwater salinity level (0.3‰) and 32 °C tolerated salinity to 50‰ when salinity was increased gradually. The relationships among UILT, LILT, 50% CTMax, 50% CTMin, UILS, 50% CSMax, salinity and temperature are given.     

Temperature and feed rate effects on Chinese catfish, Clarias fuscus (Lacepède), growth

Abstract. Chinese catfish, Clarias fuscus (Lacepède), within three size ranges were evaluated for growth, survival and feed conversion ratios (FCR). A 4 × 3 factorial design was used during year-long trials which included four temperatures (20,25,30 and 35 °C) and three feeding rates with commercially formulated salmon/trout feed. Specific growth rates of juvenile fish (1–60g) were highest, ranging from 1–64% body weight/day at 20°C (2%/day feed rate), to 4–94%/day at 25°C (6%/day feed rate). Specific growth rates of sub-adult fish (60–150g) averaged 0–65%/day, with no significant difference between temperature-feed rate treatments. Specific growth rates of adult fish (>150g) were lowest, averaging 0–30%/day for grouped feed rate treatments at 25°C, and 0–16%/day at 30°C. Most mortalities occurred during the juvenile stage, with survival ranging from 0% at 35°C(2% feed rate) to 96% at 30°C(6% feed rate). Survival was 95–100% with sub-adults and adults. FCR were 1 to 4 with juveniles, 2 to 12 with sub-adults, and 3 to 22 with adults. These trials suggest that optimal growth and FCRs were obtained at 25°C; with feed rates of 6%/day with juveniles, 2%/day with sub-adults, and 1%/day with adult fish. Final yields at 25 and 30°C indicate that even though growth and FCR are optimal at 25°C, survival was greater at 30°C, which compensated for reduced growth performance at this temperature. Yields at 25 and 30°C were almost double those at 20°C.     

A fish selective obstacle to prevent dispersion of an unwanted fish species, based on leaping capabilities

Abstract  The European minnow, Phoxinus phoxinus (L.), constitutes a serious threat to natural brown trout, Salmo trutta L., stocks in Norway following its introduction and translocation. In the present study, the leaping capabilities of the European minnow (50–110 mm total length) and brown trout (64–255 mm total length) were investigated with the aim of constructing suitable waterfall barriers to prevent further unwanted dispersal of the minnow, but still allow passage of larger brown trout. No successful leap of minnows was recorded at 4.9–6.5 °C, even at height intervals as low as 3 cm. At 14.0–16.5 °C, minnows were able to force waterfall barriers up to 27 cm high. At 4.9–6.5 °C brown trout forced waterfall barriers up to 40 cm. Thus, building of such barriers in brooks and rivers can help prevent the dispersal of minnows, and still allow larger brown trout to pass during feeding and spawning migrations.     

Effect of feeding regime and temperature on ongrowing results of pikeperch (Sander lucioperca L.)

This study aimed to determine the effect of feeding rates and water temperatures on the growth, feed utilization and size heterogeneity changes in subadult pikeperch. Fish with an average weight of 84±19 g were fed with a commercial trout diet for 18 weeks at a water temperature of 20 °C and 25 °C. Four feeding rates (PSFR) were predicted at both temperatures, which corresponded to 1.0%, 1.25%, 1.50% and 2.0% of body weight per day (bw day⁻¹) for the first, and to 0.8%, 1.0%, 1.2% and 1.4% of bw day⁻¹ for the second 9 weeks respectively. At the end of the experiment, the individual weight averaged 273±82 g. Pikeperch showed a better growth rate [specific growth rate (SGR)] and apparent feed conversion rates (AFCR) at the higher temperature. Thermal-unit growth coefficient (TGC) was better at the lower temperature. The values of SGR, TGC and AFCR significantly increased with increasing PSFR at both temperatures. The values of TGC plotted against the computed feeding rates allowed estimation of the maximum feeding rates (1.25% and 1.15% of bw day⁻¹ for pikeperch of 150–180 g at 25 and 20 °C respectively). Size heterogeneity changes were affected neither by the feeding rate nor by temperature.     

Effect of catch-and-release angling on growth and survival of rainbow trout, Oncorhynchus mykiss

Abstract Catch-and-release angling is popular in many parts of the world and plays an increasingly important role in fish conservation efforts. Although survival rates associated with catch-and-release angling are well documented for many species, sublethal effects have been less studied. An experiment was conducted to directly assess the effects of catch-and-release angling on growth and survival of rainbow trout, Oncorhynchus mykiss (Walbaum). Catch-and-release events were simulated in laboratory tanks maintained at 15–16 °C with hooks manually placed in pre-designated locations in the mouths of the fish. There were no differences in standard length ( P  = 0.59) or wet weight ( P  = 0.81) gained between caught and uncaught fish over a 1-month angling and recovery period. Survival was 96.99 ± 0.06% for rainbow trout caught and released, and did not vary with number (one, two or four) of captures. Thus, catch-and-release angling appears to have little effect on growth and mortality of rainbow trout hooked in the mouth.     

Validation of daily increment formation and the effects of different temperatures and feeding regimes on short-term otolith growth in Australian smelt Retropinna semoni

Abstract –  To aid otolith interpretation of wild fish, we conducted a laboratory study using metalarval Australian smelt ( Retropinna semoni ) collected from the Murray River, to examine daily increment deposition and the effects of different temperatures and feeding regimes on otolith growth. Daily increment deposition was confirmed by comparing the number of increments from an oxytetracycline mark with the known number of days from marking. After holding fish at two temperature levels and three feeding rates, both food density and temperature were found to have a significant effect on otolith growth, with food density having the greatest influence. Overall trends in final lengths and condition of fish were well represented by recent otolith growth. The results of the experiment have implications for estimating growth histories and its relationship to various environmental conditions.     

Differences in self-feeding activity between thermally selected and normal strains of rainbow trout Oncorhynchus mykiss at high temperatures

ABSTRACT:   Feeding activity was examined at high temperatures by using a demand feeder for thermally selected and normal rainbow trout Oncorhynchus mykiss strains. When the water temperature was raised in experiment 1 from 17.5 to 25.7°C at 0.3°C/day in 21 days, the average daily food consumption rate in the thermally selected strain rose to 7.1%, which was significantly higher than that of the normal strain (4.1%, P  < 0.05). The corresponding rate was also significantly higher in the thermally selected (0.8%) than in the normal strain (0.2%, P  < 0.05) of fish in experiment 2 where water temperature was raised to 24.1°C in 0.5°C/day increments. When water temperature was raised rapidly in experiment 3 from 16.7 to 21.7°C in one day and gradually to 24.4°C in 28 days at 0.1°C/day, the average daily food consumption rates were 1.0 and 0.1% for the thermally selected and normal strains, respectively, with significant difference ( P  < 0.01). These results suggest that the thermally selected strain has acquired thermal tolerance as a result of artificial selection.     

Do summer temperatures trigger spring maturation in Pacific lamprey,Entosphenus tridentatus?

Abstract –  Pacific lamprey, Entosphenus tridentatus , return to streams and use somatic energy to fuel maturation. Body size decreases, the lamprey mature, spawn, and then die. We predicted that warm, summer temperatures (>20 °C) would accentuate shrinkage in body size, and expedite sexual maturation and subsequent death. We compared fish reared in the laboratory at diel fluctuating temperatures of 20–24 °C (mean = 21.8 °C) with fish reared at cooler temperatures (13.6 °C). The results confirmed our predictions. Lamprey from the warm water group showed significantly greater proportional decreases in body weight following the summer temperature treatments than fish from the cool water group. A greater proportion of warm water fish sexually matured (100%) and died (97%) the following spring than cool water fish (53% sexually mature, 61% died). Females tended to mature and die earlier than males, most obviously in the warm water group.     

Effects of temperature on the fast-start swimming performance of an Australian freshwater fish

Abstract –  The fast-start swimming performance of juveniles of an Australian freshwater (warm-water) fish, golden perch, was examined in the laboratory at six water temperatures ranging between 10 and 25 °C. Fast-start swimming performance of fish was considerably reduced at temperatures less than 15.5 °C. Temperatures of less than 15 °C are typical of the thermal regime downstream of large dams in south-eastern Australia, where conditions are more suited to introduced cold-water fish species. We conclude that the swimming performance of native warm-water fish such as golden perch is likely to be negatively affected by cold-water releases from deep outlets in thermally stratified dams.     

Thermal tolerance of a rainbow trout <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis> strain selected by high-temperature breeding

ABSTRACT:   Thermal tolerance was studied in a rainbow trout strain successively selected through high temperature breeding at 20–27°C since 1966 in Miyazaki Prefecture, Japan. The hatching rate and fry mortality at high temperatures were examined in the selected strain along with normal strains cultured at water temperature of 9–17°C. The hatching rate of embryos fertilized at either 10 or 14°C and subsequently subjected to high temperatures in the blastula or neurula stage of the selected strain, was marginally higher than that of the normal strain counterparts. The upper 50% lethal temperatures (LT₅₀) for embryos in the early segmentation, blastula and neurula stages of the selected strain were also higher than those of the normal strain counterparts. Death temperatures and LT₅₀ of fries acclimated to 20°C of the selected strain were significantly higher than those of the normal strains. However, no difference in the critical thermal maximum was detected between the different strains. These results suggest that the selected strain of rainbow trout established by selecting successively for many generations at high temperatures acquired a degree of thermal tolerance.     

Effects of dietary protein and lipid level, and water temperature, on the post-feeding oxygen consumption of Atlantic cod and haddock

Tank respirometry was used to study the interactive effects of protein:lipid level (55%:11% vs. 42%:16%; both diets isoenergetic) and temperature (11, 6 and 2 °C) on the magnitude and duration of specific dynamic action (SDA) in juvenile Atlantic cod and haddock. The protein:lipid level did not affect any measured variable. However, numerous temperature and species effects were observed. For example, although the maximum post-feeding oxygen consumption (30–50% above routine metabolic rate; RMR) and SDA duration (∼55–85 h; SDA_DUR) were not affected by temperature, SDA_DUR g⁻¹ of food increased from 11 to 2 °C (from ∼3 to 12 h g food⁻¹). While absolute SDA (mg O₂) decreased by ∼60–65% in cod and ∼75% in haddock from 11 to 2 °C, due to a concomitant decrease in food consumption from ∼2.0% to 0.6% body mass, SDA comprised between 3.3% and 5.2% of the dietary energy content at all temperatures. Finally, RMR at 11 and 2 °C and SDA_DUR at 2 °C were 25–35% and 25% greater in cod, respectively, as compared with haddock. These results suggest that feeding reduced protein diets at low water temperatures is unlikely to improve the growth of these species.     

Response of Israeli carp, Cyprinus carpio L., to lysine supplementation of a practical ration at varying conditions of fish size, temperature, density and ration size

Abstract. Four feeding trials with Israeli carp, Cyprinus carpio L., were performed in cages or in ponds in order to investigate responses to lysine supplementation of low protein carp feeds under different practical conditions. In each of the trials one of the basic conditions was different: fish size—small (80–125g) or large (560g); temperature—22°C or 26°C; density—cages or ponds. In each trial 2–3 ration sizes × 2–3 lysine levels were tested. A basal diet of 25% protein and 1·35% lysine served for all the trials.
At low feeding levels, no responses to lysine supplements were found either at 22 ± 2°C or at 26 ± 2°C (0600 h) for all fish sizes. At higher feeding levels, at both temperatures, 0·5% lysine-HCl supplements to 1·7% total lysine yielded significant growth increases. Further supplements to 2·1% lysine (=8·4% of the protein) brought an additional response only from small fish of 90g in cages at the highest ration and temperature. In ponds at 26°C, the effects on small fish of 80g were smaller, probably due to available natural food. The reduction in lysine retention suggested that 1·7% lysine might have been adequate even at optimal conditions in ponds.     

Nocturnal and diurnal feeding by Galaxias auratus, a lentic galaxiid fish

Abstract –  We examined the diel feeding pattern, gastric evacuation and daily ration of a lentic, endemic Tasmanian galaxiid fish, Galaxias auratus . Analysis of stomach contents and consumption estimates based on collections of fish every 3 h over three 24-h periods in summer 2002/2003 revealed that feeding always occurred during both day and night, with no obvious peaks. We also estimated the gastric evacuation rate of G. auratus in a laboratory experiment using the two prey species found to be dominant in stomachs of field-sampled fish. The relationship was best described by an exponential model, with rate parameters ( R ) of 0.104 and 0.081 for the evacuation of the amphipod, Austrochiltonia australis , and the cladoceran, Daphnia carinata , at water temperatures of 11.5 and 16.5 °C, respectively. Daily ration of G. auratus in summer was estimated to be approximately 3% (dry body weight) using the models of Elliot & Persson and Eggers. Galaxias auratus appears to be unusual in that its feeding pattern cannot be classified as nocturnal, diurnal or crepuscular, but its gastric evacuation and daily ration estimates are still similar to other comparable Northern Hemisphere freshwater fishes.     

Relationship between stream temperature, thermal refugia and rainbow trout Oncorhynchus mykiss abundance in arid-land streams in the northwestern United States

Abstract – Warm stream temperatures may effectively limit the distribution and abundance of Pacific salmon Oncorhynchus spp. in streams. The role of cold thermal refugia created by upwelling groundwater in mediating this effect has been hypothesized but not quantitatively described. Between June 21 and September 15, 1994, rainbow trout O. mykiss abundance within 12 northeast Oregon (USA) stream reaches was inversely correlated with mean ambient maximum stream temperatures ( r =−0.7, P <0.05). Some rainbow trout used thermal refugia (1–10 m² surface area) that were on average 3–8°C colder than ambient stream temperatures. Within the warmest reaches, high ambient stream temperatures (>22°C) persisted from mid-June through August, and on average 10–40% of rainbow trout were observed within thermal refugia during periods of midday maximum stream temperatures. Frequency of cold-water patches within reaches was not significantly associated with rainbow trout density after accounting for the influence of ambient stream temperature ( P =0.06; extra sum of squares F -test). Given prolonged high ambient stream temperatures in some reaches, the thermal refugia available in the streams we examined may be too small and too infrequent to sustain high densities of rainbow trout. However, these refugia could allow some rainbow trout to persist, although at low densities, in warm stream reaches.     

Growth of the fourspine sculpin <Emphasis Type="Italic">Cottus kazika</Emphasis> in the Gonokawa River,Japan, and effects of water temperature on growth

ABSTRACT:   The fourspine sculpin Cottus kazika is indigenous to Japan and found in Honshu except for the waters facing the Seto Inland Sea, and was also found in southern Shikoku and eastern Kyushu. This species has a catadromous lifestyle and migrates as juveniles from the sea to the middle reaches of rivers to grow. The growth pattern of this fish was investigated by a mark-and-recapture method from July 1994 to December 1996, in the Nigorikawa River, a tributary of the Gonokawa River system, Shimane Prefecture. 0-year-old fish of 50–70 mm total length ( TL ) occurred in the study area from June to July, grew to 90–140 mm  TL by the following April, and attained 160–210 mm  TL by December. This fish grew rapidly in September–November and April–July, almost ceasing to grow in July–September. It seems that this stagnant growth phase in summer is a characteristic of the seasonal growth pattern of C. kazika . A rearing experiment indicated that the growth rate of C. kazika was higher at 16–22°C than at 12–14 and 24–26°C. This result supports the field evidence of a stagnant growth phase in summer in the Nigorikawa River.     

Induced breeding and larval rearing of the endangered Australian freshwater fish trout cod, Maccullochella macquariensis (Cuvier) (Percichthyidae)

Abstract. The endangered Australian freshwater fish trout cod, Maccullochella macquariensis (Cuvier), was the subject of a captive breeding programme to produce fry for reintroduction into the wild. Trout cod broodfish were maintained in earthen ponds for up to 5 years and underwent gonadal maturation each spring but did not spawn in the ponds. Infestations of the protozoan parasite Chilodonella hexasticha caused the death of at least 21 broodfish. Mature fish, removed from ponds when water temperatures had reached or exceeded 16°C, had a higher proportion of atretic oocytes and fewer fish spawned successfully compared to fish removed at lower temperatures. Ovulation was induced by a single injection of 1000–3000 iu/kg HCG. Between 1188 and 11338 eggs ranging from 2·5 to 3·6 mm in diameter were stripped from individual fish. Hatching commenced on days 5–9 and continued for up to 10 days (at 15·5–23°C). Larvae commenced feeding on days 21–25. Trout cod larvae were grown out to fry (363.3–48.6mm total length [TL]) in fertilized fry rearing ponds then released. Between 1986 and 1989, 8420 trout cod fry were released into several sites in the upper Murray River and upper Murrumbidgee River, and reports indicate that released fish are surviving.