Academic literature on the topic 'Juvenile rainbow trout'

<em>Abstract.</em>—Effective management of salmonid populations in the Great Lakes basin requires understanding how their distribution and density vary spatially. We used a hierarchical approach to evaluate the predictive capabilities of landscape conditions, local habitat features, and potential effects from coinhabiting salmonids on the distribution and densities of rainbow trout <em>Oncorhynchus mykiss</em>, brook trout <em>Salvelinus fontinalis, </em>brown trout <em>Salmo trutta</em>, and coho salmon <em>O. kisutch </em>within the majority of the Canadian tributaries of Lake Ontario. We collected fish assemblage, instream habitat, and water temperature data from 416 wadeable stream sites. Landscape characteristics were obtained for each site’s catchment and summarized into six key attributes (drainage area, base flow index, percent impervious cover (PIC), reach slope, elevation, and location with respect to permanent fish barriers). Classification trees indicated that PIC in a catchment was a critical predictor of salmonid distribution, in that beyond a threshold of 6.6–9 PIC, all salmonids were predicted to be absent. Base flow index and barriers were also important predictors of the distribution of salmonids. Models generally provided higher classification success at predicting absence (86–98%) than predicting presence (63–87%). Landscape features were the best predictors of densities of rainbow and brook trout (adjusted <em>r</em><sup>2</sup> = 0.49 and 0.30 respectively), although the local habitat features were almost as effective for predicting brook trout (<em>r</em><sup>2</sup> = 0.23). Local habitat features (proportion of riffles and pools, substrate, cover, and stream temperature), and presence of other salmonids produced the best predictive model for brown trout. Coho salmon was only locally distributed in the basin, and the derived model was driven by spatial characteristics rather than ecological processes. Our models estimate 653,000 juvenile rainbow trout and 231,000 brook trout (all age-classes) in our study streams. Finally, we estimate that current brook trout distribution in our study area is only 21% of its historic range.

<i>Abstract</i>.—To track individuals in situ, over 12 million salmon and trout have been marked with passive integrated transponder (PIT) tags in the Columbia River Basin, USA. However, few studies have examined long term tag retention as well as tag effects on juvenile salmon and trout. We marked juvenile coho salmon <i>Oncorhynchus kisutch</I> (<I>N</I> = 207), steelhead (anadromous rainbow trout) <i>O. mykiss</I> (<I>N</I> = 221), cutthroat trout <i>O. clarkii</I> (<I>N</I> = 202) and bull trout <i>Salvelinus</I> <i>confluentus</I> (<I>N</I> = 180) with 12, 19, or 23 mm PIT tags and examined tag retention, survival, growth, and physiological performance over a six month period in a laboratory environment. PIT tag retention rates were high for coho salmon (100%), steelhead (95%), cutthroat trout (97%), and bull trout (99%), regardless of tag size. Survival was also high for coho (99%), steelhead (99%), cutthroat trout (97%), and bull trout (88%) and did not vary among tag sizes. Short term individual growth rates for coho salmon marked with 12 mm tags were significantly higher than those marked with 19 mm and 23 mm PIT tags. Likewise, steelhead trout individual growth rates were lower for fish marked with 23 mm PIT tags followed by 19 and 12 mm tags. Conversely, long-term growth rates were positive and not affected by tag size. There were no significant effects of tag size or marking on coho gill Na+, K+, -ATPase activity (μmol ADP x mg protein<sup>–1</sup> h<sup>–1</sup>) and plasma osmolality (μmol kg<sup>–1</sup>) or bull trout hepatosomatic indices. Our study suggests that marking juvenile salmonids with PIT tags results in high retention with little effect upon their survival, growth, and important physiological indicators regardless of tag size in a laboratory environment.

An experience of integral farming of Oncorhynchus mykiss (rainbow trout) is carried out in Copaquilla, 90 kilometers inland from the city of Arica at 3,000 mamsl. The system used was the Recirculating Aquaculture System (RAS), which had six ponds of 40 mt3 each, two decanters with a capacity of 3.5 mt3 and a biofilter of 3.5 mt3 with substrate for the fixation of ammonium and nitrite transforming bacteria. The three latter ponds were buried below the lowest level of the fattening ponds. Three pumps, two running and one 1.5 hp. backup, plus a 1 hp. blower, were the water and air equipment utilized in the system. Each pump had a flow capacity of 450 lt min−1. This water was sucked from the biofilter and transferred to the accumulator tank with a capacity of 10 mt3. From there it was distributed by gravity to the fattening ponds. In addition, the juvenile system had a particular SAR with a 0.5 hp. pump, a small 0.2 hp. blower and an 80 watt UV lamp. The grow-out SAR received 6,000 trout with an average weight of 15 grams. The group reached approximately 1,200 grams over a year. Thirty fish were selected for reproduction. Eggs were obtained, followed by fry, juveniles and adults. This initiative demonstrated the effectiveness of producing trout in the foothills of the interior city of Arica, Chile.

<EM>ABSTRACT. </EM>The potential for <em>Myxobolus cerebralis</em>, the cause of salmonid whirling disease, to affect resident populations of spring chinook salmon <em>Oncorhynchus tshawytscha </em>in the Lostine River, Oregon, was investigated in this study. Spring chinook salmon and rainbow trout <em>O. mykiss </em>fry were held in the Lostine River for 14 d in late March 1999, when resident chinook salmon alevins naturally emerge. After exposure, fry were held in pathogen-free water in the laboratory. The prevalence of infection at 5 months postexposure, as determined by PCR, was equivalent in both species (37.5% and 41%, respectively). Only rainbow trout developed cranial lesions (average lesion severity 0.4 on a 5-point scale; 4 of 10 fish examined were positive), and no spores were detected in homogenates of cartilage from fish of either species. Comparison of data on chinook salmon spawning sites (1996–2000) with known distribution of <em>M. cerebralis </em>in the Lostine River demonstrated that the majority of chinook salmon spawn in the middle section of the river, where levels of <em>M. cerebralis </em>exposure were reduced. Results of this study indicate that juvenile chinook salmon may become infected with <em>M. cerebralis</em>, when naturally exposed to the parasite, but suggest that the timing and location of their emergence may mitigate the negative impacts of <em>M. cerebralis </em>infection in this river.

<i>Abstract</i>.—We deployed archival temperature loggers on juvenile and adult coho salmon <i>Oncorhynchus kisutch </i>and steelhead (anadromous rainbow trout) <i>O. mykiss </i>over both the freshwater and marine portions of their lifecycle in order to study their movements and thermal preferences. Beginning in 2003, loggers were deployed on juvenile coho salmon and juvenile and adult steelhead in a small central California coastal stream. A tag recovery from a coho salmon indicates the fish experienced variable temperatures on a daily to weekly basis in the marine environment (mean 13.3°C, range 10–18°C). Tags recovered from steelhead indicate use of a cooler, more stable, thermal habitat window in the marine environment (mean 11.0°C, range 8–14°C), often with little fluctuation over a period of weeks to months, and most thermal changes occurring at the seasonal time scale. Comparisons of steelhead data with sea surface temperature data suggest a northern migration out of the California Current to a narrow band of habitat that fluctuates between the southern boundary of the Bering Sea and north of the 40th parallel. In the shallow freshwater environment, steelhead appeared to be at the mercy of stream temperatures. However, in the estuary, where thermally variable habitats were available, steelhead used a surprisingly broad temperature range, including entering water thought to challenge their thermal tolerances (>20°C) even when cooler waters were available. Temperature loggers recovered on a local beach and island indicate tagged fish were consumed in the estuary by warm-blooded predators. All of these data coupled with a larger number of passive integrated transponder (PIT) tags, are helping to identify discrete habitats fish are using, exact dates of ocean entry and return, and enhance our understanding of marine survival and predation. Finally, archival tags may be useful in understanding habitat use of pelagic long-migrating species like steelhead, by tracking individuals in areas where other tagging technologies are poorly suited.

<em>Abstract.</em>—Stream carrying capacity for anadromous salmonids that rear to the smolting stage in freshwater can be predicted from a sequence of cause-response functions that describe fish preferences for macro-habitat features. The channel unit (e.g., pool, glide, riffle) is a useful stratum for quantifying rearing capacity for salmonids, and is a hydrologically meaningful unit for predicting the response of stream morphology to watershed processes. Thus, channel units are the natural link between habitat-forming processes and habitat requirements of salmonids. Maximum densities of juvenile salmonids that can be supported in a channel unit are related to availability of preferred habitat features including velocity, depth, cover, and substrate. Within channel unit types, maximum densities of salmonid parr will shift predictably as availability of cover from wood and boulders increases. Within stream reaches, additional variation in maximum rearing densities can be accounted for by light penetration and nutrient load. As salmonids grow, their habitat preferences change and the preferred habitat associated with their increasing size becomes less and less available. Further, territory size of salmonids increases exponentially with fish length, such that the demand for territory to support surviving members of a cohort increases at least through their first year of life. Changing habitat preferences and space demands, juxtaposed against shrinking habitat availability with the onset of summer low flows often results in a bottleneck to rearing capacity for age >1 salmonids in wadable streams. Habitat measurements in Oregon streams indicate that depths preferred by steelhead (anadromous rainbow trout) <em>Oncorhynchus mykiss </em>become scarce as parr exceed 15 cm in length, which coincides with the approximate threshold length for steelhead smolts. We present a generalized framework, called the Unit Characteristic Method, for accumulating effects of these habitat factors at the channel unit and reach-level scales to estimate carrying capacity for rearing salmonids in a basin. Our subsequent chapter in this book presents a demonstration of how this method can be applied to predicting salmonid production in streams.