Chinook Salmon Parr Research Articles

Evaluation of binding capacity of circulating insulin-like growth factor binding protein-1b in salmonids using a ligand immunofunctional assay

Insulin-like growth factor-binding proteins (IGFBPs) regulate the activity of insulin-like growth factor (IGF)-1. Among the three major circulating IGFBPs in salmonids, IGFBP-1b is an inhibitor of IGF activity induced under catabolic conditions. IGFBP-1b is considered to quickly sequester IGF-1 from the circulation. However, the level of circulating IGFBP-1b present in its unoccupied free form is unknown. Here, we aimed to develop a non-equilibrium ligand immunofunctional assay (LIFA) to evaluate IGF-binding capacity of circulating intact IGFBP-1b. Purified Chinook salmon IGFBP-1b, its antiserum, and europium-labeled salmon IGF-1 were used as the assay components. In the LIFA, IGFBP-1b was first captured by the antiserum, allowed to bind to the labeled IGF-1 for 22 h at 4 °C, and quantified its IGF-binding capacity. Serial dilutions of the standard and serum were prepared simultaneously within a certain concentration range (1.1–12.5 ng/ml). In underyearling masu salmon, IGF-binding capacity of intact IGFBP-1b was higher in fasted fish than in fed fish. Transferring Chinook salmon parr to seawater also increased IGF-binding capacity of IGFBP-1b, most likely due to osmotic stress. In addition, there was a strong relationship between total IGFBP-1b levels and its IGF-binding capacity. These results suggest that IGFBP-1b expressed under stress is mostly present in the free form. On the contrary, during smoltification of masu salmon, IGF-binding capacity of IGFBP-1b in the serum was relatively low and less related to the total IGFBP-1b level, suggesting its functional difference under certain physiological conditions. These results indicate that estimating both total IGFBP-1b level and its IGF-binding capacity is useful for evaluating the catabolic status and unraveling the regulation of IGF-1 activity by IGFBP-1b.

Origin, Postrelease Survival, and Imprinting of Pen‐Acclimated and Direct‐Stocked Chinook Salmon in Lake Ontario

AbstractWe determined the stocking origin of the Chinook Salmon Oncorhynchus tshawytscha harvest and compared the relative survival and tributary returns of pen‐acclimated and direct‐stocked salmon at eight sites in Lake Ontario. Chinook Salmon parr were coded‐wire‐tagged in 2010, 2011, and 2013, and adult salmon were recovered in the lake and tributaries from 2011 to 2017. Lake harvest counts indicated that pen acclimation provided significantly better smolt‐to‐lake harvest survival, with averages of 1.7, 2.3, and 2.3 times greater contribution (SE = 0.15, 0.21, 0.23), respectively, to the lake fishery than direct stocking. After accounting for lake survival, pen acclimation also provided significantly better smolt‐to‐adult return rates to tributary harvest than direct stocking at some sites, with average return ratios of 0.8, 1.1, and 1.6 (SE = 0.2, 0.2, 0.3), respectively, for the three year‐classes. Port‐specific lake harvest from June to August consisted of salmon stocked at sites throughout the lake, indicating a well‐mixed population prior to the prespawn staging period. Of the eight lake ports analyzed, a minority of the Chinook Salmon harvested by anglers in June–August were stocked at each site (mean = 13%, SE = 2%) or at nearby sites (mean = 22%, SE = 4%), with most originating from stocking sites greater than 30 km away. In September, stocked Chinook Salmon became more segregated in the lake, with harvest at each site consisting of a higher percentage (mean = 38%, SE = 4%) of salmon stocked at those sites and nearby sites (mean = 29%, SE = 5%), suggesting that salmon began staging in this period. In contrast, most salmon harvested by tributary anglers in October were stocked at those sites (mean = 67%, SE = 4%), indicating good imprinting of both pen‐acclimated and direct‐stocked Chinook Salmon. Most strays in tributaries were from nearby stocking sites. Increased Chinook Salmon catch rates in the lake fishery coincided with increased use of pen acclimation and a declining prey fish population, underscoring the importance of evaluating outcomes of new stocking policies that may increase predator survival and predation pressure on prey.

Estimating carrying capacity for juvenile salmon using quantile random forest models

AbstractEstablishing robust methods and metrics to evaluate habitat quality is critical for the recovery of endangered Pacific salmonids (Oncorhynchus spp.). A variety of modeling approaches are used for status and trend monitoring of anadromous species throughout the Pacific Northwest, USA, but current methods may fail to capture the complex relationship between fish and habitat and are often limited in predictive power beyond specific watersheds. Further, the focus on species distribution and abundance is not easily manipulated to predict carrying capacity and traditional stock‐recruitment analyses are reliant on long‐term data which are not always available. In this study, we developed a quantile random forest model to provide estimates of habitat carrying capacity for Chinook salmon (O. tshawytscha) parr during the summer months, at both the site and watershed scale. Quantile random forest models allow for the consideration of noisy data, correlated variables, and non‐linear relationships: common features in fish–habitat datasets. We leveraged Columbia Habitat Monitoring Program data to select habitat co‐variates and predict capacity at those sites. We also identified a set of globally available attributes to extrapolate capacity estimate predictions throughout wadeable streams within the Columbia River basin. Total capacity estimates for watersheds closely matched estimates from alternative fish productivity models. Carrying capacity estimates based on quantile random forest models, like those presented here, provide managers a framework to guide the identification, prioritization, and development of habitat rehabilitation actions to recover salmon populations.

Fall and Winter Movement Dynamics of Naturally Produced Spring Chinook Salmon Parr in Two Neighboring Interior Pacific Northwest Natal Rivers

AbstractOverwintering Pacific salmon Oncorhynchus spp. are vulnerable to mortality. Ecosystem degradation exacerbates salmonid vulnerability to mortality; thus, knowledge of winter movement dynamics is essential for guiding holistic management and restoration to safeguard population viability. In northeast Oregon, long‐term population performance metrics (e.g., survival) exist for parr of two neighboring Chinook Salmon O. tshawytscha populations (Catherine Creek [CC] and Grande Ronde River [GRR]); however, knowledge of their winter ecology is lacking. Our objective was to spatiotemporally characterize the movements and rearing distributions of naturally produced CC and GRR spring Chinook Salmon parr during fall and winter. Using radiotelemetry techniques (October–February), we identified the movement dynamics of CC (2009–2012) and GRR (2014–2016) spring Chinook Salmon fall migrants (i.e., parr overwintering downstream from natal areas). For both populations, median weekly linear range (i.e., movement) was high during fall migration, while sedentary behavior was associated with anchor and surface ice. Fall emigration occurred during declining thermographs, while overwintering parr movement and water temperature peaks were proximate. Fall migrant CC parr predominantly overwintered in the upper Grande Ronde Valley (GRV), while GRR conspecifics primarily reared upstream from the GRV. Extensive portions of CC and the GRR were not included in either population’s 99% kernel density estimate (KDE); however, each population’s 99% KDE extended into the lower GRV. The GRR population’s 50% KDE (i.e., core area) was small and proximate to several North American beaver Castor canadensis impoundments, while the CC population’s core area was relatively large and situated in the upper GRV. Overall, CC and GRR fall migrant populations exhibited divergent rearing and movement patterns; however, each population’s winter core area was proximate to lentic‐like habitats (e.g., beaver ponds). For Chinook Salmon parr, natal‐stream‐specific overwintering ecology knowledge appears critical to guide winter habitat conservation and restoration, while management for lentic‐like habitats may be advisable throughout the Pacific Northwest.

Mechanisms behind interactive effects of temperature and bifenthrin on the predator avoidance behaviors in parr of chinook salmon (Oncorhynchus tshawytscha)

Many coastal systems have been experiencing the effects of non-chemical and chemical anthropological stressors through respective increases in surface water temperatures and rainstorm-derived runoff events of pyrethroid pesticide movement into waterways such as the San Francisco Bay-Delta. Salmonid populations in the Bay-Delta have been dramatically declining in recent decades. Therefore, the aim of this study was to investigate the interactive effects of bifenthrin, a pyrethroid insecticide, and increasing water temperatures on targeted neuroendocrine and behavioral responses in Chinook salmon (Oncorhynchus tshawytscha) parr (10- month post-hatch). Parr were reared at 11 °C, 16.4 °C, or 19 °C for 14 days and, in the final 96 h of rearing, exposed to nominal concentrations of 0, 0.15, or 1.5 μg/L bifenthrin. A predatory avoidance Y-Maze behavioral assay was conducted immediately following exposures. Parr were presented a choice of clean or odorant zones, and locomotive behavior was recorded. Thyroid hormones (T3 and T4), estradiol, and testosterone were quantified within plasma using ELISAs, and the expression of brain hormone and dopamine receptor genes were also evaluated by qPCR. Brain dopamine levels were analyzed by LC/MS. No significant changes were observed in brain transcripts or plasma hormone concentrations with bifenthrin or increasing temperature. However, temperature did significantly lower brain dopamine levels in fish reared at 19 °C compared to 11 °C controls, but was unaltered by bifenthrin treatment. In contrast, parr reared at 11 °C and exposed to 1.5 μg/L bifenthrin spent significantly less time avoiding a predatory odorant compared to vehicle controls reared at 11 °C. The 16.4 °C and 1.5 μg/L-treated fish spent significantly more time in the neutral arm compared to the odorant and clean arms, as well as spending significantly less time in the clean arm compared to the 11 °C control fish. These results suggest that the interaction of temperature and bifenthrin may be adversely impacting predator-avoidance behavior, which may not be related to dopaminergic responses.

Estimating the benefits of widespread floodplain reconnection for Columbia River Chinook salmon

In the Pacific Northwest, widespread stream channel simplification has led to a loss of habitat area and diversity for rearing salmon. Subsequent efforts throughout the Columbia River basin (CRB) have attempted to restore habitats altered through land development to recover imperiled salmon populations. However, there is scant evidence for demographic change in salmon populations following restoration. We used a process-based approach to estimate the potential benefit of floodplain reconnection throughout the CRB to Chinook salmon (Oncorhynchus tshawytscha) parr. Using satellite imagery, we measured stream habitats at 2093 CRB stream reaches to construct random forest models of habitat based on geomorphic and regional characteristics. Connected floodplain width was the most important factor for determining side channel presence. We estimated a current CRB-wide decrease in side channel habitat area of 26% from historical conditions. Reconnection of historical floodplains currently used for agriculture could increase side channel habitat by 25% and spring Chinook salmon parr total rearing capacity by 9% over current estimates. Individual watersheds vary greatly in habitat factors that limit salmon recovery, and large-scale estimates of restoration potential like these are needed to make decisions about long-term restoration goals among imperiled populations.

Fall and Winter Microhabitat Use and Suitability for Spring Chinook Salmon Parr in a U.S. Pacific Northwest River

AbstractHabitat degradation has been implicated as a primary threat to Pacific salmon Oncorhynchus spp. Habitat restoration and conservation are key toward stemming population declines; however, winter microhabitat use and suitability knowledge are lacking for small juvenile salmonids. Our objective was to characterize microhabitat use and suitability for spring Chinook Salmon Oncorhynchus tshawytscha parr during fall and winter. Using radiotelemetry techniques during October–February (2009–2011), we identified fall and winter microhabitat use by spring Chinook Salmon parr in Catherine Creek, northeastern Oregon. Tagged fish occupied two distinct gradient reaches (moderate and low). Using a mixed‐effects logistic regression resource selection function (RSF) model, we found evidence that microhabitat use was similar between free‐flowing and surface ice conditions. However, habitat use shifted between seasons; most notably, there was greater use of silt substrate and areas farther from the bank during winter. Between gradients, microhabitat use differed with greater use of large wood (LW) and submerged aquatic vegetation in the low‐gradient reach. Using a Bayesian RSF approach, we developed gradient‐specific habitat suitability criteria. Throughout the study area, deep depths and slow currents were most suitable, with the exception of the low‐gradient reach where moderate depths were optimal. Near‐cover coarse and fine substrates were most suitable in the moderate‐ and low‐gradient reaches, respectively. Near‐bank LW was most suitable throughout the study area. Multivariate principal component analyses (PCA) indicated co‐occurring deep depths supporting slow currents near cover were intensively occupied in the moderate‐gradient reach. In the low‐gradient reach, PCA indicated co‐occurring moderate depths, slow currents, and near‐bank cover were most frequently occupied. Our study identified suitable and interrelated microhabitat combinations that can guide habitat restoration for fall migrant and overwintering Chinook Salmon parr in Catherine Creek and potentially the Pacific Northwest.

Life History Observations of Adfluvial Chinook Salmon prior to Reintroduction of Anadromous Salmonids

AbstractPacific salmon Oncorhynchus spp. vary in life history and degree of anadromy, but information on populations inhabiting only freshwater throughout their life cycle is limited. We confirmed the presence of a self‐sustaining population of adfluvial Chinook Salmon O. tshawytscha upstream of century‐old hydroelectric dams in the Skokomish River system, Washington. Snorkel, redd, and juvenile‐trapping surveys revealed their life history attributes prior to planned reintroductions of anadromous salmonids above the dams. Adult Chinook Salmon in Lake Cushman (a reservoir) were large‐bodied fish (mean length = 610 mm; mean weight = 5.4 kg), up to 4 years of age, and migrated into the inlet river to spawn in October and November. Annual peak counts of adult spawners were chronically low (35 or less) based on interannual snorkel surveys since 1994. Chinook Salmon parr (n = 780; mean length = 105 mm) of a single cohort were captured (June–August) at the upper dam and had faded parr marks and bright, silvery coloration typical of smolts. Our study confirmed that Chinook Salmon reared and reproduced exclusively in freshwater and suggested a life history pattern most closely resembling anadromous fall‐run Chinook Salmon. We reviewed annual hatchery release records from 1926 to 2016 and found no evidence of Chinook Salmon being planted above the dams, in contrast to landlocked Chinook Salmon occurring in Oregon and California reservoirs. These adfluvial Chinook Salmon may be descendants of the native Skokomish River anadromous population, including fish from below the dam, and represent adaptations to the reservoir after dam construction. Lake Cushman Chinook Salmon are federally threatened, the only reported landlocked population in Puget Sound and coastal Washington, and may represent a unique evolutionary legacy worthy of protection.Received March 7, 2017; accepted July 5, 2017 Published online October 20, 2017

Can stream and riparian restoration offset climate change impacts to salmon populations?

Understanding how stream temperature responds to restoration of riparian vegetation and channel morphology in context of future climate change is critical for prioritizing restoration actions and recovering imperiled salmon populations. We used a deterministic water temperature model to investigate potential thermal benefits of riparian reforestation and channel narrowing to Chinook Salmon populations in the Upper Grande Ronde River and Catherine Creek basins in Northeast Oregon, USA. A legacy of intensive land use practices in these basins has significantly reduced streamside vegetation and increased channel width across most of the stream network, resulting in water temperatures that far exceed the optimal range for salmon growth and survival. By combining restoration scenarios with climate change projections, we were able to evaluate whether future climate impacts could be offset by restoration actions. A combination of riparian restoration and channel narrowing was predicted to reduce peak summer water temperatures by 6.5 °C on average in the Upper Grande Ronde River and 3.0 °C in Catherine Creek in the absence of other perturbations. These results translated to increases in Chinook Salmon parr abundance of 590% and 67% respectively. Although projected climate change impacts on water temperature for the 2080s time period were substantial (i.e., median increase of 2.7 °C in the Upper Grande Ronde and 1.5 °C in Catherine Creek), we predicted that basin-wide restoration of riparian vegetation and channel width could offset these impacts, reducing peak summer water temperatures by about 3.5 °C in the Upper Grande Ronde and 1.8 °C in Catherine Creek. These results underscore the potential for riparian and stream channel restoration to mitigate climate change impacts to threatened salmon populations in the Pacific Northwest.

Predation on Chinook Salmon Parr by Hatchery Salmonids and Fallfish in the Salmon River, New York

AbstractNaturally reproduced Chinook Salmon Oncorhynchus tshawytscha contribute substantially to the fishery in Lake Ontario. The Salmon River, a Lake Ontario tributary in New York, produces the largest numbers of naturally spawned Chinook Salmon, with parr abundance in the river often exceeding 10 million. In the spring of each year, large numbers of hatchery salmonid yearlings—potential predators of Chinook Salmon parr—are released into the Salmon River by the New York State Department of Environmental Conservation. We sought to examine predation on Chinook Salmon parr in the Salmon River during May and June prior to out‐migration. Over the 4 years examined (2009–2012), annual consumption of Chinook Salmon parr by hatchery‐released yearling steelhead O. mykiss and Coho Salmon O. kisutch ranged from 1.5 to 3.3 million and from 0.4 to 2.1 million, respectively. In 2009, Fallfish Semotilus corporalis were estimated to consume 2.9 million Chinook Salmon parr. Predation was higher in May, when the average TL of Chinook Salmon parr was 44.5 mm, than in June. Fallfish were also important predators of naturally reproduced steelhead subyearlings, consuming an estimated 800,000 steelhead in 2009. Hatchery‐released yearling salmonids consumed 13.8–15.3% of the Chinook Salmon parr that were estimated to be present in the Salmon River during 2010–2012. Earlier releases of hatchery salmonid yearlings could reduce the riverine consumption of Chinook Salmon parr by facilitating the out‐migration of yearlings prior to Chinook Salmon emergence.Received February 23, 2015; September 29, 2015

Circulating salmon 28- and 22-kDa insulin-like growth factor binding proteins (IGFBPs) are co-orthologs of IGFBP-1

Circulating insulin-like growth factor binding proteins (IGFBPs) play pivotal roles in stabilizing IGFs and regulating their availability to target tissues. In the teleost circulation, three major IGFBPs are typically detected by ligand blotting with molecular masses around 20–25, 28–32 and 40–45 kDa. However, their identity is poorly established and often confused. We previously identified salmon 22- and 41-kDa forms as IGFBP-1 and -2b, respectively. In the present study, we cloned the cDNA of 28-kDa IGFBP from Chinook salmon ( Oncorhynchus tshawytscha) as well as rainbow trout ( Oncorhynchus mykiss) based on the partial N-terminal amino acid sequence of purified protein and identified it as an ortholog of IGFBP-1. Structural and phylogenetic analyses revealed that the 28-kDa IGFBP is more closely related to human IGFBP-1 and zebrafish IGFBP-1a than the previously identified salmon IGFBP-1 (i.e. 22-kDa IGFBP). We thus named salmon 28- and 22-kDa forms as IGFBP-1a and -1b, respectively. Salmon IGFBP-1a contains a potential PEST region involved in rapid protein turnover and phosphorylation sites typically found in mammalian IGFBP-1, although the PEST and phosphorylation scores are not as high as those of human IGFBP-1. There was a striking difference in tissue distribution patterns between subtypes; Salmon igfbp-1a was expressed in a variety of tissues while igfbp-1b was almost exclusively expressed in the liver, suggesting that IGFBP-1a has more local actions. Direct seawater exposure (osmotic stress) of Chinook salmon parr caused increases in both IGFBP-1s in plasma, while IGFBP-1b appeared to be more sensitive. The presence of two co-orthologs of IGFBP-1 in the circulation in salmon, and most likely in other teleosts, provides a good opportunity to investigate subfunction partitioning of duplicated IGFBP-1 during postnatal growth.

Influence of Predation Mortality on Survival of Chinook Salmon Parr in a Lake Michigan Tributary

AbstractPredation mortality among Chinook salmon Oncorhynchus tshawytscha parr can act at small spatiotemporal scales and cause variability in parr survival and potential recruitment. We analyzed predator diets and multiplied per capita consumption rates by predator population estimates to evaluate the relative effect of predation by stocked sport fishes on the variability in survival of Chinook salmon parr in the Muskegon River, Michigan, from 2004 to 2007. Brown trout Salmo trutta were a major predator of Chinook salmon parr, consuming from 15% to 34% of the total number available, while walleyes Sander vitreus consumed from 0.2% to 15%. Walleyes also consumed large quantities of brown trout and rainbow trout O. mykiss. Brown trout predation on Chinook salmon parr was largely dependent on parr size, while walleye predation was buffered by the availability of rainbow trout and brown trout. Predation mortality appeared to be responsible for a more than three‐fold difference in the survival of Chinook salmon parr in the Muskegon River. The vulnerability of Chinook salmon parr to predation appeared to be controlled by parr growth rates, brown trout stocking dates, and the number of brown trout stocked. Fishery regulations to manipulate piscivore abundance may lead to higher survival and lower variability in the survival of Chinook salmon parr.

The effect of dietary fish oil and poultry fat replacement with canola oil on swimming performance and metabolic response to hypoxia in stream type spring Chinook salmon parr

Swimming performance, metabolic rate, and the metabolic response to hypoxia were measured in stream-type spring Chinook salmon parr ( Oncorhynchus tshawytscha) that had been reared for up to 40 weeks on diets where varying levels of refined canola oil (CO) replaced anchovy oil and poultry fat as the source of supplemental dietary lipids. Thus, CO comprised either 0% (dAPF), 25% (CO25), 49% (CO49), or 72% (CO72) of total dietary lipid. Aerobic swimming performance (repeat U crit test) was unaffected by diet in freshwater or following 24 h exposure to 75% seawater. Resting oxygen consumption (MO 2) and metabolic response to hypoxia (as indicated by the critical oxygen tension, P crit) were also unaffected by diet. Although dietary fatty acid (FA) composition clearly affected the FA composition of whole body total lipids in Chinook salmon parr, it had little effect on the FA composition and unsaturation index of whole body polar lipids. Chinook salmon parr maintained their polar lipid composition and unsaturation index, possibly through bioconversion of 18:3n−3 (linolenic acid; LNA) and 18:2n−6 (linoleic acid; LA) to their more highly unsaturated derivatives and/or by selective incorporation and retention of omega-3 FAs into the polar lipids. Because the polar lipids are largely found in membranes, this may indicate that membrane lipid composition was relatively constant across dietary groups and this, in turn, may largely explain the lack of physiological effects observed in this study. Taken together with a companion study on this same group of fish (Huang et al., 2008) where dietary treatment was not observed to adversely affect fish growth, feed intake and utilization, survival, and ionoregulatory development, there appears to be great potential for inclusion of CO in the diets of farmed pre-smolt Chinook salmon.

Changes to Rainbow Trout Abundance and Salmonid Biomass in a Washington Watershed as Related to Hatchery Salmon Supplementation

AbstractWe evaluated the changes in (1) the abundance, size, and biomass of rainbow trout Oncorhynchus mykiss, (2) the abundance of spring Chinook salmon O. tshawytscha parr, and (3) the combined biomass of rainbow trout and Chinook salmon parr after nine annual releases of approximately 250,000 Chinook salmon and coho salmon O. kisutch smolts into the North Fork of the Teanaway River, Washington. The trout and salmon were sampled in two treatment locations consisting of five sites and three control locations consisting of seven sites before (1990–1998) and during hatchery releases (1999–2007). We detected statistically significant decreases of rainbow trout abundance and biomass in both treatment streams relative to two of the three control streams. Furthermore, all of the differences in abundance between treatment and control streams were in the negative direction. All but one of the differences in biomass was negative. The only statistically significant change in the combined biomass of spring Chinook salmon parr and rainbow trout before and during supplementation was negative, and five of the six differences in combined biomass were negative. Only one of the four comparisons of the ratio of the log‐transformed weight to length of rainbow trout was statistically significant, and it decreased during supplementation; one‐half of the comparisons were positive and the other half negative. The changes to rainbow trout abundance and biomass were probably the result of the cumulative impacts from hatchery‐released Chinook salmon smolts and an increase in naturally produced Chinook salmon parr.

Effects of dietary canola oil level on growth, fatty acid composition and osmoregulatory ability of juvenile fall chinook salmon ( Oncorhynchus tshawytscha)

This study assessed refined canola oil (CO) as a supplemental dietary lipid source for juvenile fall chinook salmon, Oncorhynchus tshawytscha, parr with respect to possible effects on their growth and osmoregulatory performance and body composition. Diets with equal protein (∼ 57%) and lipid (∼ 19%) content (dry weight basis) were supplemented with lipid from either anchovy oil (AO) or CO with AO so that CO comprised 0 (0CO), 11% (11CO), 22% (22CO), 33% (33CO), 43% (43CO) or 54% (54CO) of the dietary lipid content. Triplicate groups of juvenile chinook salmon were fed their prescribed diets for 104 days in freshwater (FW) and 31 days in seawater (SW) after a 4-day transition period. Dietary fatty acid compositions reflected the different proportions of AO and CO in the supplemental lipid. Diet treatment had no effect on fish growth, feed intake, feed efficiency, protein utilization, fish mortality or terminal whole body water and ash percentages. Whole body lipid percentages were higher in 11CO and 43CO fish than in 33CO fish and in 11CO fish versus 22CO fish. Whole body protein percentages were highest in 33CO, 43CO and 54CO fish and lowest in 0CO and 22CO fish. Terminal whole body fatty acid compositions were influenced strongly by the dietary fatty acid compositions. Haematocrit and muscle water percentages were not affected consistently and plasma Na + and Cl − concentrations were unaffected by diet treatment in FW or 24-h seawater challenges during FW residency. Also, diet treatment had no effect on the physiological parameters after SW residency. We conclude that dietary treatment had no effect on fish growth performance under our experimental conditions. Also, the dietary inclusion of CO neither facilitated nor impaired the transfer of chinook salmon parr to seawater. Thus, CO was found to be an excellent and cost-effective source of supplemental dietary lipid for culture of juvenile fall chinook salmon during freshwater residency.

Effects of dietary canola oil level on growth performance, fatty acid composition and ionoregulatory development of spring chinook salmon parr, Oncorhynchus tshawytscha

This study assessed the potential of refined canola oil (CO) as a source of supplemental dietary lipid for pre-smolt spring chinook salmon (Oncorhynchus tshawytscha) over a period of 30 weeks. Triplicate groups of 320 fry (∼0.80 g), reared in flow-through well water (8–11.5 °C), were fed one of four steam-pelleted dry diets with equivalent gross energy (24.3 MJ/kg), protein (∼51.3%) and lipid (∼21.6%) content on a dry-weight basis. CO furnished either 0%, 33%, 67%, or 100% of the supplemental dietary lipid, with the remainder from a commercial blend of 1:1 anchovy oil and poultry fat (APF). Thus, CO comprised either 0% (dAPF), 25% (CO25), 49% (CO49), or 72% (CO72) of total dietary lipid content. Overall fish growth rate, feed intake, feed efficiency, protein utilization, percent survival, and terminal whole body proximate constituents were unaffected by diet treatment. Dietary lipid compositions reflected the ratios of CO and APF in the supplemental lipid and their respective fatty acid compositions. Whole body fatty acid compositions mirrored those of diet treatments. However, some essential fatty acids, namely, arachidonic acid (20:4n-6; AA), and docosahexaenoic acid (22:6n-3; DHA) were conserved in fish regardless of dietary CO level. Direct relationships were found between dietary and whole body concentrations of: 18:2n-6 (R2=0.94; slope=0.72), 18:3n-3 (R2=0.99; slope=0.58), 20:4n-6 (R2=0.84; slope=0.42), 20:5n-3 (R2=0.99; slope=0.43) and 22:6n-3 (R2=0.82; slope=1.25). High dietary levels of 18:3n-3, 18:2n-6, and 20:5n-3 may have been utilized for energy or converted to more unsaturated derivatives. Overall development of ionoregulatory ability, as assessed by 24-h seawater challenge tests, was unaffected by diet. However, whole body chloride content was generally inversely related to dietary CO level during early development. Our findings suggest that there is excellent potential for long-term replacement of fish oil with canola oil in the diet of pre-smolt spring chinook salmon, provided that some marine oil is present to ensure that the essential fatty acid needs of the fish are met.

The effect of chronic chromium exposure on the health of Chinook salmon ( Oncorhynchus tshawytscha)

This study was designed to determine fish health impairment of Chinook salmon ( Oncorhynchus tshawytscha) exposed to chromium. Juvenile Chinook salmon were exposed to aqueous chromium concentrations (0–266 μg l −1) that have been documented in porewater from bottom sediments and in well waters near salmon spawning areas in the Columbia River in the northwestern United States. After Chinook salmon parr were exposed to 24 and 54 μg Cr l −1 for 105 days, neither growth nor survival of parr was affected. On day 105, concentrations were increased from 24 to 120 μg Cr l −1 and from 54 to 266 μg Cr l −1 until the end of the experiment on day 134. Weight of parr was decreased in the 24/120 μg Cr l −1 treatment, and survival was decreased in the 54/266 μg Cr l −1 treatment. Fish health was significantly impaired in both the 24/120 and 54/266 μg Cr l −1 treatments. The kidney is the target organ during chromium exposures through the water column. The kidneys of fish exposed to the greatest concentrations of chromium had gross and microscopic lesions (e.g. necrosis of cells lining kidney tububules) and products of lipid peroxidation were elevated. These changes were associated with elevated concentrations of chromium in the kidney, and reduced growth and survival. Also, variations in DNA in the blood were associated with pathological changes in the kidney and spleen. These changes suggest that chromium accumulates and enters the lipid peroxidation pathway where fatty acid damage and DNA damage (expressed as chromosome changes) occur to cause cell death and tissue damage. While most of the physiological malfunctions occurred following parr exposures to concentrations ≥120 μg Cr l −1, nuclear DNA damage followed exposures to 24 μg Cr l −1, which was the smallest concentration tested. The abnormalities measured during this study are particularly important because they are associated with impaired growth and reduced survival at concentrations ≥120 μg Cr l −1. Therefore, these changes can be used to investigate the health of resident fish in natural waters with high chromium concentrations as well as provide insight into the mechanisms of chromium toxicity.

Interactions between natural and hatchery chinook salmon parr in a laboratory stream channel

Pre-smolt (fry and parr) hatchery chinook salmon Oncorhynchus tshawytscha are increasingly being used in supplementation projects to augment natural but diminished salmon populations, but little is known of the behavioral interactions between sympatric hatchery and wild chinook salmon populations and how those interactions may affect success of a supplementation program. We used experiments conducted in a laboratory stream channel to document behavioral interactions that occur when hatchery salmon are stocked to streams containing existing natural chinook salmon juveniles. We found that natural fish aggression was suppressed when hatchery fish were larger than natural fish in the spring and summer, and the aggressiveness of natural fish increased when paired with similar sized hatchery fish during fall. Types of micro-habitat used by natural chinook salmon were mainly affected by hatchery fish during the fall trials when more natural fish were found in open pool areas, and fewer used cobble cover when hatchery fish were present. Observed behavioral shifts by natural chinook salmon parr could increase energy expenditures and exposure to predators when hatchery fish are present, but there were few consistent effects from hatchery salmon on the growth or movement patterns of natural chinook salmon during this study. Relative fish size, increased stream densities, and the behavior of the hatchery salmon appeared to be a major factors influencing observed changes in the behavior of juvenile natural chinook salmon in the stream sections.

Statistical Relationship between Parr-to-Smolt Survival of Snake River Spring–Summer Chinook Salmon and Indices of Land Use

We used simple regression models to demonstrate an association between land use and parr survival of chinook salmon Oncorhynchus tshawytscha from overwintering areas in the Snake River drainage of Idaho and Oregon to the first main-stem dam encountered during emigration to the Pacific Ocean. We used data on tagged (passive integrated transponder tags) releases of naturally produced Snake River spring–summer chinook parr and subsequent tag detections, as well as indices of land use, vegetation, and road density. We spot-checked the land-use and vegetation indices in a field survey of spawning and rearing areas in the summer of 1999, and we believe that they are reliable indicators of land-use patterns. The models also employed month of release, length of parr at release, and a drought index as independent variables. The models were developed and tested using parr tagged from 1992 through 1998. Age-0 parr that reared in wilderness areas (a land-use category; not necessarily federally designated Wilderness Areas) had the highest survival during their last 6–9 months of freshwater residence. In contrast, parr that reared in young, dry forests (typically, intensively managed timber lands) had the lowest survival. Similarly, parr that reared in areas of low road density had substantially higher survival than those in areas of high road density. We concluded that in the area studied there is a close association between land-use indices and survival of chinook salmon parr during their last 6–9 months of freshwater residence. This analysis suggests that road-building and associated land-use activities in the region may have a detrimental effect on the survival of juvenile chinook salmon and that mitigative changes in these activities could be warranted because Snake River spring–summer chinook salmon are listed as threatened under the Endangered Species Act.

Modeling relationships between landscape-level attributes and snorkel counts of chinook salmon and steelhead parr in Idaho

Knowledge of environmental factors impacting anadromous salmonids in their freshwater habitats, particularly at large spatial scales, may be important for restoring them to previously recorded levels in the northwestern United States. Consequently, we used existing data sets and an information-theoretic approach to model landscape-level attributes and snorkel count categories of spring-summer chinook salmon (Oncorhynchus tshawytscha) and steelhead (Oncorhynchus mykiss) parr within index areas in Idaho. Count categories of chinook salmon parr were negatively related to geometric mean road density and positively related to mean annual precipitation, whereas those for steelhead parr were negatively related to percent unconsolidated lithology. Our models predicted that chinook salmon parr would be in low count categories within subwatersheds with >1 km·km-2 geometric mean road densities and (or) <700 mm mean annual precipitation. Similarly, steelhead parr were predicted to be in low count categories in subwatersheds with >30% unconsolidated lithology. These results provide a starting point for fish biologists and managers attempting to map approximate status and quality of rearing habitats for chinook salmon and steelhead at large spatial scales.