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Effects of introduced trout predation on non-diadromous galaxiid fish populations across invaded riverscapes
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We assessed the landscape-scale effect of predation pressure from trout on the population integrity and distributions of non-diadromous galaxiids in high-country streams of the South Island, New Zealand. The effects of trout (brown trout, Salmo trutta, and rainbow trout, Oncorhynchus mykiss) on two widespread species, the Canterbury galaxias (Galaxias vulgaris Stokell) and the alpine galaxias (G. paucispondylus Stokell) were assessed. Experiments confirmed that both species were vulnerable to trout predation and that habitat (size and disturbance regime) may be a factor in local co-occurrence. Quantitative electrofishing surveys indicated that G. paucispondylus distributions were less affected by trout than G. vulgaris distributions and that the species’ range was limited by temperature. Trout created demographic sinks for G. vulgaris across most invaded reaches, while refuge populations in streams above barriers to trout acted as demographic sources for this species. G. vulgaris was consistently absent from small, stable stream reaches far from sources, indicating that trout predation pressure and propagule pressure (driven by immigration from sources) interact to drive local G. vulgaris persistence in trout-invaded reaches. Predation pressure is likely to be highest in areas where infrequent flooding allows high densities of large trout (> 150 mm FL) to occur and where there are few refugia for galaxiids. A spatial model was developed to predict exclusion of galaxiids by trout across invaded networks. If used appropriately, the model could be used to find new refuge populations of non-diadromous galaxiids and to aid planning of active rehabilitation of trout-invaded river networks
Diet of rainbow trout in Lake Rotoiti: an energetic perspective
No full textWe characterised seasonal and ontogenetic changes in diet and prey energy density of rainbow trout (Oncorhynchus mykiss) in Lake Rotoiti, New Zealand, to better understand the prey requirements of trout in central North Island lakes. Common smelt (Retropinna retropinna) was the dominant prey item of rainbow trout larger than 200 mm (77.8% of diet by weight), followed by kōura (freshwater crayfish Paranephrops planifrons; 6.3%), common bully (Gobiomorphus cotidianus; 5.5%), and kōaro (Galaxias brevipinnis; 3.4%). Juvenile rainbow trout (<200 mm) consumed amphipods, aquatic and terrestrial insects, oligochaetes, tanaid shrimps, and smelt. Trout consumed kōaro only in autumn and winter; consumption of other species did not vary seasonally. The maximum size of smelt consumed increased with increasing trout size, but trout continued to consume small smelt even as large adults. Consumption of larger prey items (kōaro and kōura) also increased with increasing trout size. This study indicates the importance of smelt for sustaining rainbow trout populations, as predation on other species was relatively low. These findings provide a basis for bioenergetic modelling of rainbow trout populations in lakes of the central North Island of New Zealand
Do native brown trout and non-native brook trout interact reproductively?
Get PDFReproductive interactions between native and non-native species of fish have received little attention compared to other types of interactions such as predation or competition for food and habitat. We studied the reproductive interactions between non-native brook trout (Salvelinus fontinalis) and native brown trout (Salmo trutta) in a Pyrenees Mountain stream (SW France). We found evidence of significant interspecific interactions owing to consistent spatial and temporal overlap in redd localizations and spawning periods. We observed mixed spawning groups composed of the two species, interspecific subordinate males, and presence of natural hybrids (tiger trout). These reproductive interactions could be detrimental to the reproduction success of both species. Our study shows that non-native species might have detrimental effects on native species via subtle hybridization behavior
Seasonal changes in abundance of brown trout (Salmo trutta) and rainbow trout (s. gairdnerii) assessed by drift diving in the Rangitikei river, New Zealand
No full textNumbers and approximate sizes of brown trout (Salmo trutta L.) and rainbow trout (5. gairdnerii Richardson) were estimated by snorkel divers at 6 sites in the middle reaches of the Rangitikei River, North Island, New Zealand, over 14 months. The results showed that different species and sizes of trout varied in abundance with time. The species of fingerling trout (6-12 cm FL) could not be identified because of their small size and shoaling behaviour. Rainbow trout abundance varied seasonally and was greatest in January and April (between 18 and 60 fish per kilometre) when fish between 23 and 38 cm FL were the most abundant size class. Brown trout abundance showed much less variation with time (between 5 and 36 fish per kilometre at most sites). Also in contrast to rainbow trout, the majority of brown trout were > 38 cm FL, and in June, when the greatest density was observed (56 fish per kilometre), 70 redds were seen at the same site. Two sites were dived within a 48 h period to test the variability of the method. Comparisons between the 3 dives at each site revealed no significant differences between the numbers offish in different species and size classes
Weight, Length, and Growth in Cutbow Trout (Oncorhynchus mykiss x clarkii)
Get PDFBackground: The cutbow trout (Oncorhynchus mykiss x clarkii) is a fertile hybrid of rainbow and cutthroat trout. Little published length-weight data is available for this hybrid, and a standard weight curve is not established. Eleven Mile Reservoir is a clear mountain reservior in Colorado with a surface area of 13.4 square kilometers, an average depth of 10 m, and a maximum depth of 41 m. 80,000 cutbow trout were stocked through the ice in late winter before samples were taken.
Materials and Methods: Angling provided 171 samples which were weighed and measured (total length and fork length). Dressed weight was also determined with the scales, head, and entrails removed. Estimates of parameters a and b in the model, W(L) = aLb, were obtained by both linear least-squares (LLS) regression (log(W) = log(a) + b log(L)) and non-linear least-squares (NLLS) regression, where W is weight in kg and L is length in cm. Parameter estimates of an improved model, W(L) = (L/L1)b, were also determined by NLLS regression; the parameter L1 is the typical length of a fish weighing 1 kg. The resulting best-fit parameters, parameter standard errors, and covariances are compared between the two models. Average weight and length are considered for each month from June through October to estimate growth rates for fish stocked over the winter. Standard weights (relative to the rainbow trout and cutthroat trout standard weight curves) are also determined, along with the ratio of total length to fork length and typical dressed weight percentage. 
Results: The improved model parameter estimates were b = 2.662 and L1 = 45.32 cm, with correlation coefficient r = 0.969. From June to October, mean relative weight decreased from 101.5% to 93.6% relative to the rainbow trout standard weight and 114.5% to 103.2% relative to the cutthroat trout standard weight as mean total lengths increased from 34.4 cm to 41.9 cm and the mean weights increased from 0.505 kg to 0.830 kg. Typical dressed weight is 71% of the total weight. 
Conclusion: Eleven mile reservoir is an excellent trout fishery, capable of producing large numbers of cutbow trout in good condition. The cutbow trout is well suited to this kind of mountain reservoir and grows fast. As might be expected, the weights of cutbow trout of a given length tend to fall between the standard weights of the rainbow and the cutthroat. For the season, the average relative weight was 97.0% relative to the rainbow trout, and 108.3% relative to cutthroat trout.

TROUT STEAKS: CONSUMER PERCEPTIONS OF A NEW FOOD ITEM
Get PDFWater quality standards and a limited water supply have dramatically restricted the expansion of the U.S. trout industry. Faced with production restrictions, producers have turned to value-added products to strengthen the economic growth of the industry. In the near future, trout steaks could surface in retail outlets as a new revenue source for the mature trout industry. A telephone survey of consumers in Chicago and Los Angeles was conducted by the University of Idaho in the spring of 1997 to determine consumer preferences for trout steaks and, ultimately, to determine the viability of this product form. Using a probit analysis, fresh trout steaks were found to be more popular than frozen trout steaks. Consumers that exhibited significantly higher preference for fresh trout steaks were Hispanic, had high school education (or less), and/or believed that trout was less expensive than other meats. Chicago respondents and individuals with an urban background tended to display a higher preference toward frozen trout steaks.Consumer/Household Economics,
Market Integration of Farmed Trout in Germany
Get PDFPrice formation and integration of markets supplied by both farmed and captured fish is studied. Markets for trout and potential substitutes imported to Germany are analysed, and market delineation and market leaders identified. It is found that markets for small portion-sized farmed trout with white meat are related to, rather than completely separate from, other fish markets, and that markets for these trout are more closely linked to markets for captured fish than to farmed salmon. The implications are that although the part of the trout business operating with small freshwater ponds remains relatively unaffected by developments in other fish markets, careful attention should be paid to markets for and management of capture fisheries like cod, halibut, redfish, and mackerel, than to markets for farmed salmon.Price formation, market integration, captured-farmed fish, Production Economics, F15, Q21, Q22,
Abundance and Function of Multiple Haemoglobin Isomorphs from Rainbow Trout (Oncorhynchus mykiss)
No full textHaemoglobins perform the vital physiological function of transporting oxygen from the external environment to the tissues. Poikilothermic rainbow trout (Oncorhynchus mykiss = Salmo gairdneri = S. irideus) produce multiple forms of haemoglobin that respond differently to varying environmental and physiological conditions. However, the timescale and physiology of these changes are not known. Changes in isomorph abundance may potentially originate from the production of new isomorphs in already circulating erythrocytes. Alternatively, new isomorphs may be produced through the reassembly of extant haemoglobin subunits. The final hypothesis is that changes in isomorph abundance occur through the production of new erythrocytes with red blood cells ‘pre-programmed’ to produce a particular set of haemoglobins. Changes originating from production of new erythrocytes would require longer periods of time before being detectable; weeks to months depending on the temperature regime. To test this, paired groups of rainbow trout were subjected to either 10ºC or 20ºC for 5, 7, 14, 21 and 28 days. A total of 14 isomorphs were observed after the haemolysate was separated using cellulose acetate electrophoresis. However, no detectable differences in isomorph abundance were found between treatment groups. In a follow-up experiment, anaemia was induced in rainbow trout to stimulate the production of new erythrocytes. The trout were then held at either 10ºC or 20ºC for 21 days. This resulted in relative increases in the abundance of anodal haemoglobin isomorphs in the 20ºC acclimated group and a corresponding decrease in cathodal haemoglobin isomorphs. To further confirm that changes in abundance were occurring through the production of new erythrocytes, separation of erythrocytes into age classes was undertaken to compare the isomorphs present in mature erythrocytes with those from erythrocytes produced under amended temperature regimes. Using Percoll density gradients, red blood cells from anaemia-induced trout acclimated to either 10ºC or 20ºC were enriched into mature and young erythrocyte fractions. Further significant differences in abundance were found between both anodal and cathodal isomorphs when compared between treatment groups. From these results it was concluded that changes in haemoglobin isomorph abundance originated from the production of new erythrocytes. Cellulose acetate gel electrophoresis was carried out on seven haemoglobin fractions that had undergone prior separation from whole haemolysate by Fast Protein Liquid Chromatography. Each haemoglobin fraction was found to be composed of two isomorphs for a total of 14 haemoglobin isomorphs. The oxygen binding properties of each fraction was examined under varying conditions of temperature, pH, ATP and chloride concentrations. Cathodal functional groups HbI to HbIII were found to be insensitive to temperature, pH, chloride and the organic phosphate ATP. In contrast, the anodal fractions (HbIV to HbVII) all responded to pH and temperature changes, while HbVI and HbVII responded to ATP. However, no fraction responded to increased chloride concentrations. These results suggest that different varieties of rainbow trout may produce different forms of haemoglobin as part of an adaptive response to local environmental conditions, leading to variation in the functional properties of some of the less abundant functional groups such as HbIII. Despite the theory that cathodal haemoglobins function as emergency back-up supplies of oxygen being proposed more than thirty years ago, no published information can be found for it being tested in the laboratory. Two groups of anaemia-induced rainbow trout were placed in a divided annular flume for 24 days. The high activity group was subjected to a forced swimming speed of 2.5 body lengths (B.L.) s-1 for 6 h d-1. When not undergoing forced exercise the treatment group were maintained at the same speed as the low activity group of 0.5 B.L. s-1. Significant differences in haemoglobin isomorph abundance were present between the initial samples taken at the time of anaemia induction and high and low activity groups. However, only the C4 isomorph demonstrated a significant difference between high and low activity groups. When total anodal and cathodal isomorphs were compared between initial state, high activity and low activity groups, no differences were present. These data suggest that the induction of anaemia had an effect on the composition of the isomorphs but no physiological effect on oxygen delivery. In addition, the swimming velocity of 2.5 B.L. s-1 employed for the high activity group may have been an insufficient stimulus to induce changes in isomorph abundance. It is concluded that changes in haemoglobin isomorph abundance occur in response to chronic changes in the environment. Increases in the abundance of anodal isoforms in response to increasing temperature allows for increased delivery of oxygen to tissues undergoing increases in metabolic activity associated with higher temperatures. The multiple haemoglobin isomorphs of rainbow trout provide an increased efficiency in delivery of oxygen to tissues under varying metabolic conditions of pH, temperature and oxygen saturation. The cathodal and anodal haemoglobin functional groups of rainbow trout exhibit different oxygen affinities in response to temperature, pH and ATP concentration but not to physiologically realistic chloride concentrations. The oxygen binding properties of the isomorphs within the cathodal and anodal functional groups are broadly similar. However, differences in responses by the anodal functional groups to NTPs may exist. An examination of the hypothesis that cathodal haemoglobins act as reserve oxygen delivery sources under prolonged activity produced no significant results. However, this hypothesis still remains viable and needs to be tested under different experimental conditions. This work provides a basis for further research into the adaptive abilities of rainbow trout. The selection of rainbow trout which better adapt to wide ranges of environmental conditions would allow for targeted introduction by fisheries managers to aquatic systems previously not considered optimal for trout growth thereby expanding the fishery
Community of Trout River municipal plan 1985-1995
No full textThe Community of Trout River Municipal Plan 1985-1995Adoption and approval. Council resolution -- Seal and signature -- Clerk's certification -- Minister's approval -- Introduction. Foreword. Municipal planning in Newfoundland and Labrador -- Municipal planning area -- Summary and conclusions of the background study. Population, employment and housing -- Other community problems opportunities and needs -- Policy assumptions. Economic factors -- Political policies -- The municipal plan. The future community -- Goals and objectives. Community structure -- Housing -- Employment -- Environment and natural resources -- Education -- Recreation -- Health -- Other community services -- Transportation -- Municipal finance -- Policies. Community structure -- Residential areas -- Commercial areas -- Industrial areas -- Public and community use areas -- Recreation areas -- Other open space areas -- Environmental protection areas -- Rural and resource areas and mineral workings -- Public works and utility areas -- Mixed areas -- Transportation -- Specific provisions. Community park -- Comprehensive development areas -- Implementation. Programme of development -- Public works -- Administration. Introduction -- Development regulations -- Development control -- Capital works programme -- Plan maps. Explanation. Proposed land use map A -- Proposed land use map
CONSUMER PERCEPTIONS OF TROUT AS A FOOD ITEM
Get PDFThe impacts of socioeconomic/demographic characteristics, experiences and preferences of consumers on trout purchasing decisions were estimated using Probit and Ordered Probit regression techniques. Data from a survey of consumer purchasing behavior and personal attributes were used to deduce factors that led to either a high or low likelihood of purchasing trout products. Analysis of data pertaining to whole trout and value-added products yielded consistently different characteristics of consumers who show a high affinity toward purchasing one or more of such products. Results from these analyses were used to suggest techniques for marketing whole trout and value-added trout products to specific segments of the consumer population.Food Consumption/Nutrition/Food Safety,
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