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1.
Abstract  – Movements of adult Atlantic salmon were tracked through a series of four fish passes and an impoundment on the River Conon system, Northern Scotland. Proportions of fish passing individual obstructions ranged from 63 to 100%. The cumulative effect was that only 4 of the 54 tagged fish reached the spawning areas. The fish were delayed for 1–41 days at a pool-and-overfall ladder and 1–52 days at a Borland fish lift. The fish swam through a 10 km long reservoir at 0.21–1.16 km·h−1. A total of 13 fish negotiated a 2.5 km long, 3 m diameter diversion tunnel through a mountain to their home river. High levels of electromyogram (EMG) activity were recorded during ascent of a pool-and-overfall fish ladder, indicating that high energy demanding burst swimming was required.  相似文献   

2.
Roscoe DW, Hinch SG, Cooke SJ, Patterson DA. Behaviour and thermal experience of adult sockeye salmon migrating through stratified lakes near spawning grounds: the roles of reproductive and energetic states. Ecology of Freshwater Fish 2010: 19: 51–62. © 2009 John Wiley & Sons A/S
Abstract –  Little is known about physiological factors underlying thermal behaviour in Pacific salmon ( Oncorhynchus spp.). We implanted acoustic transmitters and temperature loggers into migrating adult sockeye salmon ( Oncorhynchus nerka ) and nonlethally assessed their reproductive hormone levels and energetic states immediately prior to their passing through natal lakes en route to spawning grounds. We tested the hypothesis that energetic and reproductive status influence thermoregulatory and other in-lake behaviours. More reproductively advanced females with lower levels of energy transited through cooler temperatures compared to less mature females with high levels of energy, possibly to reduce metabolic energy expenditure and delay final maturation. Transit temperatures of males were not related to physiological variables. Salmon travelled on average 13.6 km·day−1 through two lakes, and often circled or held for more than 1 day before moving upstream, but these behaviours were generally not related to physiological variables.  相似文献   

3.
Abstract – Age and growth of juvenile tilapia, Oreochromis niloticus , from Lakes Zwai, Langeno and Chamo (Ethiopia) were studied from microincrements in otoliths. Growth in length was best described by the Gompertz model. Average growth rate of the fish was most rapid in Lake Chamo (0.39 mm  ·  day−1, 1.14%  ·  day−1), intermediate in Lake Zwai (0.20 mm  ·  day−1, 0.72%  ·  day−1) and slowest in Lake Langeno (0.16 mm  ·  day−1, 0.62%  ·  day−1). Similarly, back-calculation from otolith increment widths gave growth rates of 0.28 to 0.43 mm  ·  day−1, 0.15 to 0.32 mm  ·  day−1 and 0.11 to 0.28 mm  ·  day−1 for Chamo, Zwai and Langeno fish, respectively. In addition, Fulton's condition factor was largest for Chamo tilapia and smallest for Langeno tilapia; the difference between fish from Langeno and Zwai was small. Rapid growth of juvenile O. niloticus in Lake Chamo was attributed to warm temperature and better food quality. Note  相似文献   

4.
Abstract –  Differences in growth and allocation of energy of young-of-the-year (YOY) perch ( Perca fluviatilis ) were studied in relation to both quantity and quality of food. Feeding on fish and Mysidacea, the mean size of YOY perch after the first growing season in Lake Pfeiffer was 152 mm. In contrast, YOY perch grew to 107 mm in Lake Speldrop and 83 mm in Lake Reeser Meer while mainly feeding on zooplankton. In correlation with food uptake and growth, the lipid content of YOY perch was significantly highest in Lake Pfeiffer and lowest in Lake Reeser Meer, assuming that YOY perch from Lake Pfeiffer should be able to survive starvation periods during their first winter better then those from Lake Speldrop and Lake Reeser. While feeding on fish, mean highest growth rates were 1.31 mm·day−1 in the laboratory. Growth in weight started when food uptake exceeded 66 J·g WW−1·day−1, while an increase of lipid content required food input of 175 J·g WW−1·day−1. Increased growth potential associated with the availability of energetically profitable food is assumed as an important factor that could have far-reaching consequences for the fish community.  相似文献   

5.
Abstract –  An individual-based early life history model demonstrated that the timing and distribution of St Lawrence River northern pike ( Esox lucius ) spawning could affect subsequent young-of-year (YOY) production during nursery and influence year-class formation. Three different spawning patterns have emerged from empirical studies, where egg deposition occurred along the entire littoral gradient beginning in seasonally flooded emergent habitats in tributaries, progressing to submerged aquatic vegetation in shallow bays, and ending in deep water littoral habitats (up to 6 m). The spawning period is protracted, and typically lasts 6–8 weeks due to the presence of a strong thermal gradient. The model used temperature as the driving variable to predict egg abundance, stage-specific development, growth, survival, and ultimately relative production of YOY northern pike within 1-ha plots representative of the three habitats. Earlier spawning (mean 21 days) and higher mean daily survival and growth yielded higher YOY net production for tributaries (mean = 3095.4 g ha−1, SD = 2028.6) relative to the shallow bay habitat (202.5 g ha−1, SD = 125.7). In contrast, deep littoral habitat represented an ecological sink with little production (<0.9 g ha−1). The results demonstrate the importance of the linkage between spawning and nursery processes in determining reproductive success.  相似文献   

6.
Abstract – Larvae and juveniles of perch Perca fluviatilis and bream Abramis brama of Lake Speldrop, a highly eutrophicated gravel-pit lake in the floodplain of the Lower Rhine, were used in laboratory experiments to study predation of perch on bream. In the first series of experiments (control), 0+ perch of 30 mm total length (TL) did not prey on 0+ roach of about 24 mm TL. The perch fed only on zooplankton, resulting in low growth rates of 0.17 mm  ·  day−1. In the second series of experiments, perch (30 mm TL) were combined with 0+ bream with an average TL of 14 and 19 mm at different ratios. As in the first series, even a nine-fold higher amount of zooplankton food had no significant influence on the growth rate of perch, regardless of the perch:bream ratio. At a perch: bream ratio of 7:1 and 4:4 all bream were eaten by the perch and restocked twice daily. At the end of the experiment, the TL of perch at a perch:bream ratio of 7:1 was significantly lower compared to a perch:bream ratio of 4:4 (mean growth rates at 7:1 of 0.16 mm  ·  day−1 and at 4:4 of 0.35 mm  ·  day−1). At the perch:bream ratio of 1:7, perch fed on bream in varying amounts, averaging between 3 and 12 bream per day and per individual. After 20 days, the final length of these fish was always significantly higher than the TL of perch at other perch:bream ratios and increased in correlation to number of bream eaten per day (mean growth rate 1.13 mm  ·  day−1). The results are discussed with respect to the piscivore-dominated fish community of the eutrophied Lake Speldrop. Note  相似文献   

7.
The effects of several feeding levels (1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% and 4.5% of body weight per day, BW day−1) on the growth, feed efficiency and body composition of juvenile Lutjanus argentimaculatus (body weight 27.1 g) were examined. Fish were fed a test diet (40% protein, 18.4% lipid and 13.4 kJ g−1) for 75 days in three equal meals. Weight gain and specific growth rate increased with increasing feeding level up to 2.5% BW day−1, after which no significant improvement in growth was observed. The feed efficiency, protein efficiency ratio, retention of protein and digestibility of nutrients did not differ for fish fed 1–2.5% BW day−1, but decreased significantly when feeding levels were increased above 3% BW day−1. The chemical compositions of whole fish or body organs were significantly affected by the feeding level. The condition factor, mesenteric fat, hepato- and viscerosomatic indices were higher in fish fed 2.5–4.5% BW day−1. The cholesterol, triglycerides and haematocrit values were similar among treatments, except that high levels of plasma lipids were recorded in fish fed at 2.5% BW day−1. Taking into consideration the growth, feed efficiency and body composition data attained in this study, a feeding level of 2.5% BW day−1 is recommended for juvenile L. argentimaculatus weighing between 27 and 140 g.  相似文献   

8.
Abstract –  Stable isotopes of carbon and nitrogen ( δ 13C and δ 15N) were examined in wild and aquaculture origin Atlantic salmon, Salmo salar , to evaluate their utility to identify escaped farmed fish. Samples of muscle tissue obtained from wild Conne River, Newfoundland, salmon were significantly more enriched in nitrogen ( δ 15N: mean = 12.75; SD ± 0.38‰) but depleted in lipid corrected carbon ( δ 13C': mean = −20.51; SD ± 0.23‰) by comparison with aquaculture specimens obtained from Bay d'Espoir, Newfoundland ( δ 15N = 10.96 ± 0.19‰;  δ 13C' = −19.25 ± 0.17‰) resulting in a complete separation of the two groups. Aquaculture specimens differed in δ 13C' from analyses of commercial salmon diet by 0.24‰, within the enrichment range associated with trophic transfers, while the δ 15N values in salmon muscle were enriched by 5.01‰. Although differences occurred in direct comparisons of white muscle and adipose tissue ( N  = 49), the average δ 13C' and δ 15N signatures varied in absolute amounts by only 0.5‰, supporting the use of adipose tissue as a nonlethal means to determine isotopic signatures of Atlantic salmon.  相似文献   

9.
The efficacy of emamectin benzoate as an oral treatment of sea lice, Lepeophtheirus salmonis (KrÒyer), infestations in Atlantic salmon, Salmo salar L., was evaluated in a dose titration study and two dose confirmation studies. Replicated groups of salmon with induced infestations of sea lice were given emamectin benzoate on pelleted feed at doses of 0, 25, 50 and 100 μg kg−1 biomass day−1 for seven consecutive days. Sea lice were counted at 7, 14 and 21 days from the start of treatment, and comparisons made with control fish given the same diet without emamectin benzoate. Total numbers of sea lice were significantly reduced at all doses in all three studies when compared to control fish. There was no significant difference between doses of 50 and 100 μg kg−1, but the 50 μg kg−1 dose resulted in significantly fewer lice than the 25 μg kg−1 dose. Emamectin benzoate was highly effective in reducing numbers of preadult and adult lice and prevented the maturation of chalimus to motile stages. The optimum therapeutic dose was selected as 50 μg kg−1 day−1 for seven days. Treatment reduced the incidence of epidermal damage by sea lice and, in one study, survival of treated fish was 48% higher than in control groups. No fish mortalities or adverse effects were attributed to treatment with emamectin benzoate at any of the doses tested.  相似文献   

10.
Isonitrogenous and isocaloric diets containing 0, 18 or 36% toasted full-fat soybean meal (FFSM) were fed to Atlantic halibut. The diets were fed to five tanks of fish each for 34 days (period 1). Four tanks from each treatment were then retained in the growth experiment for a further 32 days (period 2), while the groups of fish from one tank from each of the 0 and 36% FFSM groups were split and transferred to two metabolism tanks each. The initial weight of the fish in the growth trial was 169 ± 1 g (mean ± SEM, n =12; weight range 89–253 g) and the final weight was 317 ± 5 g. There was no significant effect of dietary treatment on specific growth rate (range, 0.8–1.1% day−1), feed consumption (0.5–0.7% body weight day−1), feed efficiency (1.3–1.6 g wet gain g dry feed−1), protein retention (48–55%) or energy retention (49–57%). The fat, protein and energy concentrations in the fish increased during the trial and were not affected by the diet. The hepatosomatic index in fish fed with 36% FFSM diet was significantly lower (1.7%) than in the other groups (2.2%) ( P  < 0.05). No differences in intestinal morphology were observed between dietary treatments and no pathological reactions were identified in any of the samples. In the metabolism trial, there were no significant differences in oxygen consumption or ammonia excretion between fish fed with 0 and 36% FFSM diets. In conclusion, up to 36% FFSM may be added to diets for Atlantic halibut without negative effects on growth, feed efficiency or intestinal morphology.  相似文献   

11.
The feasibility of obtaining a similar growth response from juvenile pink abalone Haliotis corrugata at a research laboratory and a hatchery, when using natural feeds was evaluated. Four macroalgae, Egregia menziesii , Eisenia arborea , Macrocystis pyrifera , Gracilaria sp., and the surfgrass Phyllospadix torreyi were used as feeds. Response patterns of abalone were very similar at both facilities in terms of final length, weight, and survival, varying from 13.0 to 15.50 mm, 0.31 to 0.52 g, and 60.0% to 78.6%, respectively. Better growth was obtained when E. menziesii , M. pyrifera , and Gracilaria sp. were offered. Poor results were obtained with surfgrass. The feed conversion ratio was determined at the laboratory and did not vary significantly, ranging from 42.3 to 199.0; although a significant inverse correlation was observed with growth rate. Growth in length and weight and survival rates varied within 1.6–20.2 μm day−1, 0.123–1.664 mgday−1, 0.4–0.64%day−1, respectively. Mean growth rate in length (14.7μm day−1) and weight (1.18 mg day−1) at the hatchery were significantly higher than that obtained at the laboratory (9.4 μm day−1 and 0.77 mg day−1), which is most likely a consequence of more suitable water temperature at the hatchery. Mean survival rate was significantly higher at the laboratory (53.1%day−1) than at the hatchery (46.1%day−1).  相似文献   

12.
Abstract –  We studied the migratory behaviour of armado, Pterodoras granulosus , in the Paraná River Basin of Brazil, Paraguay and Argentina, during 1997–2005. This species invaded the Upper Paraná River after upstream dispersal was facilitated when Itaipu Reservoir inundated a natural barrier. Fish were tagged ( N  = 8051) in the mainstems of the Yacyreta and Itaipu reservoirs, bays of major tributaries, the Paraná River floodplain above Itaipu Reservoir, and below dams. In all, 420 fish were recaptured of which 61% moved away from the release area. Fish moved a maximum of 215 km (mean 42), and at a maximum rate of 9.4 km·day−1 (mean 0.6). Of the 256 armados that moved away from the release site, 145 moved upstream towards unimpounded stretches of the Paraná River and 111 moved downstream into the reservoir and bays of its tributaries (maximum 150 km). Based on the observed migratory movements, we suspect that most of the reproductive output originates in tributaries to the reservoirs. The ability of this species to expand its range presents a conundrum by pitting fishery management interests against conservation needs. Maintenance of the important armado fisheries depends on the ability of the species to migrate freely to use spawning and nursery areas in reservoir tributaries and floodplains. However, its ability to migrate long distances can allow this non-native species the opportunity to invade most of the Upper Paraná River.  相似文献   

13.
Factorial determinations of energy and protein requirements in growing Sparus aurata were carried out at 23–24°C. The energy content in the whole fish was dependent on fish weight and ranged from 5 to 11 MJ kg−1 body mass for 1–250 g fish, whereas the protein content remained constant at 179 g kg−1.
During starvation the fish lost 42.5 kJ body weight (BW) (kg)−0.83 day−1 and 0.42 g protein BW (kg)−0.70 day−1. The maintenance requirement for energy was calculated to be 55.8 kJ BW (kg)−0.83 day−1 and for protein 0.86 g BW (kg)−0.70 day−1. Utilization of digestible energy and digestible crude protein below and at maintenance was determined as 0.72 and 0.51, respectively. Utilization of digestible energy and digestible crude protein for growth above maintenance was determined as 0.46 and 0.28, respectively.
These values allow estimation of requirements for growing Sparus aurata .  相似文献   

14.
Four ongrowing cycles of common octopus ( Octopus vulgaris ), each with two stocking densities, were carried out in an offshore area in order to evaluate the effect of the following variables on growth ( G , % body weight day−1) and mortality ( M , % day−1): weight ( W , 0.5–3.0 kg), temperature ( T , 14–26 °C), stocking density (SD, 6–46 kg m−3), size dispersion, expressed as coefficient of variation (CV, 13–42%) and significant wave height (SWH: 0.4–1.2 m). The assays were performed in an 8 m3 stainless-steel floating cage divided into two compartments of 4 m3 each. For the range of temperatures considered (14–26 °C), G depended significantly on T and SWH, with maximum G values being obtained at 18.5 °C and with an important negative effect of SWH. M depended significantly on T, W and CV, mortality being minimal at 18 °C. The two other variables had an antagonistic effect, mortality increasing with greater size dispersion – suggesting that animals should be graded throughout the process – although the effect diminished as the sizes increased. The results point towards two alternatives for the commercial ongrowing of octopus under the particular conditions of the present study: (A) two ongrowing cycles of 3.5 months to reach a final weight of 2.5 kg or (B) one 5-month cycle to reach a final weight of 3.5 kg.  相似文献   

15.
Abstract  Conservation efforts for endangered Snake River sockeye salmon ( Oncorhynchus nerka ) have been hindered by high en route adult mortality during their ∼1450 km freshwater spawning migration. Identifying causal factors for this mortality has been difficult given very small (often <10 fish) annual returns in recent decades. However, several hundred hatchery-bred fish returned in 2000 and we intercepted and radio-tagged 31 in mid-migration to monitor behaviours and survival. All fish initially migrated at similar rates, but later-timed fish eventually slowed migration and were far more likely to be unsuccessful. Late-season mortality was strongly associated with water temperatures near tolerance thresholds (21–24 °C). The data also suggest increased risk for fish in poor initial condition (i.e., with injuries or parasites) and probable recent selection against late-timed salmon. Results parallel temperature- and condition-related adult mortality in Columbia and Fraser River sockeye salmon populations and demonstrate the potential vulnerability of marginal southern populations to regional climate warming.  相似文献   

16.
Juvenile Haliotis rufescens were reared in the laboratory in order to investigate the extent to which fresh kelp and formulated feeds with 250 g kg−1 (25P) and 380 g kg−1 protein content (38P) affected their growth rate, gut residence time (GRT), food consumption ( C ), food conversion ratio (FCR) and digestibility. Abalone from 38P attained the highest growth rate (70.5 ± 4.2 μm day−1; 98.3 ± 6.95 μg day−1), followed by 25P (47.9 ± 2.79 μm day−1; 67.4 ± 2.82 μg day−1) and kelp (23.6 ± 3.36 μm day−1; 28.2 ± 4.11 μg day−1). No significant differences were observed in consumption rate among treatments (0.61–0.68% body weight per day), yet kelp-fed abalone exhibited higher FCR (2.44), protein efficiency ratio (4.42), and apparent digestibility of dry matter (69.5%), protein (69.8%) and gross energy (79.2%) than 38P organisms (59.8, 62.4 and 62.2%, respectively). They also showed longer GRT (23.1 ± 0.93 h). This study demonstrated that formulated diets with 250 g kg−1 and 380 g kg−1 protein inclusion can sustain higher growth rates of juvenile H. rufescens than fresh algae. These differences seem to be due to the amount of dietary protein. Kelp meal appears to improve the consumption and digestibility of balanced diets, and its inclusion in formulated diets is recommended.  相似文献   

17.
Abstract –  We compared timing of smolt migration for two populations of naturally spawned Atlantic salmon, Salmo salar , originating from an upper catchment (River Tummel) and a lower catchment (River Almond) tributary of the River Tay, Scotland. Smolts from the upper tributary began migration earlier than those from the lower tributary. On both occasions when fry derived from River Isla (lower tributary) stock were transferred to a location in the upper catchment, smolt migration was later than for native fish. Similarly, when fry from Tummel and Isla stocks were stocked in a common, upper catchment location, Isla origin fish migrated at a later date, in both of the two following smolt years. These differences are indicative of a genetic basis for the timing of smolt migration and suggestive of local adaptation. Mounting evidence points towards local genetic adaptation for the timing of expression of behaviours associated with migration. These aspects of variation should be accommodated in management theory and practices.  相似文献   

18.
Abstract  Hatchery-reared age-0 red snapper, Lutjanus campechanus (Poey), were released onto artificial habitats in the Gulf of Mexico. Fish showed 12.7% survival after 7 months on small habitats (0.86 m3) and 3.1% survival after 8 months on large habitats (3.9 m3). Emigration was estimated by the movement of fish to unstocked habitats and accounted for 76.8% of the total decline in abundance at release sites after 26 days. Fish showed higher survival and growth rates on small habitats (27.6% at 26 days; 0.33 mm day−1) compared with large habitats (13.2% at 34 days; 0.26 mm day−1), which may have been due to increased predation and competition on large habitats. Fish became evenly distributed among adjacent habitats 26 days after release, indicating that stocking densities at release habitats were above carrying capacities. These observations suggested that providing additional habitat around red snapper release sites would increase survival.  相似文献   

19.
Embryonic mortality, egg production and the spawning stock biomass of Pacific anchovy, Engraulis japonicus , off Southern Korea during 1983–1994, and their biological response to oceanographic features in spring and summer, were analysed. The instantaneous mortality rate (IMR) of embryonic stages decreased in spring and increased in summer, with a range of 0.33–1.23 day–1 in spring and 0.78–1.69 day–1 in summer. Egg production in summer was three times that during spring and production was low in the late 1980s. Mean lengths of yolk-sac larvae and adult females were greater in spring than in summer, whereas spawning fraction and spawning stock ratio (spawning biomass:adult biomass) were lower in spring than summer. Estimated mean spawning stock biomass ranged from 141 × 103 to 380 × 103 MT in spring and from 221 × 103 to 557 × 103 MT in summer. Statistically, the seasonal and long-term trends of embryonic mortality, egg production and spawning stock biomass of Pacific anchovy can be explained largely by spring warming, summer cooling and by less abundant zooplankton in the late 1980s.  相似文献   

20.
Biwa salmon Oncorhynchus sp. is endemic to Lake Biwa, Japan, where it is an important commercial and recreational fisheries species. However, no information is currently available on its population structure and migration ecology. Therefore, here we evaluated whether otolith Sr/Ca, Ba/Ca and 87Sr/86Sr ratios can be used as natural signatures in Biwa salmon and then used these to determine the natal origins of lake-migration-phase individuals and spawning adults, and the homing ability of spawning adults in the Lake Biwa water system. Quadratic discriminant function analysis demonstrated that the lake-migration school comprised individuals with multiple origins, including rivers to the east, west and north of Lake Biwa, and that the homing rate of spawning adults was low (18 out of 80 individuals), with ca. 78% of fish straying into non-natal rivers. However, this straying behaviour was not spatially random, with fish tending to migrate upstream in rivers neighbouring their natal rivers. The high rate of straying in spawning adults is considered important for establishing and maintaining this species, which is highly adapted to life in the Lake Biwa water system where environmental disturbances often occur.  相似文献   

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