Dispersion of common merganser (Mergus merganser) breeding pairs in relation to the availability of juvenile Pacific salmon in Vancouver Island streams

1986 ◽  
Vol 64 (3) ◽  
pp. 756-765 ◽  
Author(s):  
C. C. Wood
Keyword(s):  
Pacific Salmon ◽  
Prey Availability ◽  
Vancouver Island ◽  
Egg Laying ◽  
Breeding Pair ◽  
Juvenile Salmon ◽  
Mergus Merganser ◽  
Juvenile Pacific Salmon ◽  
Stream Size ◽  
Common Merganser

Common merganser (Mergus merganser) breeding pairs and broods were censused on eight coastal streams on Vancouver Island to evaluate the relative importance of the number of potential breeding pairs, stream size, and the availability of juvenile Pacific salmon in limiting merganser breeding density. The number of potential breeding pairs did not limit nesting density on at least one stream where juvenile salmon populations were enhanced by a hatchery and spawning channel. At distances > 1 km above tidal influence, breeding pairs were evenly dispersed along the streams during the peak egg-laying and incubation period at maximum densities of 0.4–1.4 pairs/km. Maximum breeding pair counts were higher and more variable among streams on the lower kilometer of freshwater (1–9 pairs) and on tidal waters near the stream outlets (4–9 pairs). Stream size accounted for only a part of the variation in breeding pair counts. The estimated number of broods produced on each stream was highly correlated (r = 0.95) with both drainage area and juvenile salmon production, including production from hatcheries. Possible mechanisms relating the dispersion of breeding pairs to the availability of juvenile salmon are discussed. A "food assessment" hypothesis, whereby breeding pairs choose a nesting stream on the basis of prey availability during the nesting season, could not be rejected on the basis of predictions about hatching dates and duckling survival. This hypothesis has serious implications for mortality of wild salmonids in hatchery-enhanced streams.

Predation of Juvenile Pacific Salmon by the Common Merganser (Mergus merganser) on Eastern Vancouver Island. II: Predation of Stream-Resident Juvenile Salmon by Merganser Broods

1987 ◽  
Vol 44 (5) ◽  
pp. 950-959 ◽  
Author(s):  
C. C. Wood
Keyword(s):  
Body Weight ◽  
Census Data ◽  
Coho Salmon ◽  
Pacific Salmon ◽  
Vancouver Island ◽  
Juvenile Salmonids ◽  
Mergus Merganser ◽  
The Common ◽  
Tidal Waters ◽  
Common Merganser

Predation of stream-resident juvenile salmonids by broods of the common merganser (Mergus merganser) was investigated in three streams on eastern Vancouver Island from 1980 to 1982. Daily fish consumption by merganser ducklings was estimated to range from 80% of body weight for ducklings at 10 d of age to 40% of body weight for those at 40 d of age. Merganser ducklings were never observed to eat juvenile salmonids on tidal waters, but did eat them on the freshwater reaches of streams studied. Typically, broods inhabited only the freshwater reaches of their natal stream while young, but spent progressively more time foraging on tidal waters as they grew older. The biomass of broods (and hence potential consumption) on fresh water was estimated by reconstructing the history of individual broods from census data. These results suggest that merganser broods consumed on the order of 82 000–131 000 coho salmon (Oncorhynchus kisutch) fry in the Big Qualicum River between June 10 and August 25. This is equivalent to 24–65% of the observed wild smolt production from this system, assuming that these fry would otherwise have survived as well as uneaten fry.

The Ecology of Juvenile Salmon in the Northeast Pacific Ocean: Regional Comparisons

2007 ◽  
Keyword(s):  
Chinook Salmon ◽  
Sockeye Salmon ◽  
Pacific Salmon ◽  
Gulf Of Alaska ◽  
Juvenile Salmon ◽  
Stomach Fullness ◽  
Feeding Intensity ◽  
Percentage Weight ◽  
Juvenile Pacific Salmon ◽  
Survival Patterns

Abstract.—Upon entering marine waters, juvenile Pacific salmon <em>Oncorhynchus </em>spp. depend on feeding at high and sustained levels to achieve growth necessary for survival. In the last decade, several concurrent studies have been examining the food habits and feeding intensity of juvenile Pacific salmon in the shelf regions from California to the northern Gulf of Alaska. In this paper, we compared results from feeding studies for all five species of juvenile salmon (Chinook salmon <em>O. tshawytscha</em>, coho salmon <em>O. kisutch</em>, chum salmon <em>O. keta, </em>sockeye salmon <em>O. nerka</em>, and pink salmon <em>O. gorbuscha</em>) between 2000 and 2002, years when these regions were sampled extensively. Within these years, we temporally stratified our samples to include early (May–July) and late (August–October) periods of ocean migration. Coho and Chinook salmon diets were most similar due to a high consumption of fish prey, whereas pink, chum, and sockeye salmon diets were more variable with no consistently dominant prey taxa. Salmon diets varied more spatially (by oceanographic and regional factors) than temporally (by season or year) in terms of percentage weight or volume of major prey categories. We also examined regional variations in feeding intensity based on stomach fullness (expressed as percent body weight) and percent of empty or overly full stomachs. Stomach fullness tended to be greater off Alaska than off the west coast of the United States, but the data were highly variable. Results from these comparisons provide a large-scale picture of juvenile salmon feeding in coastal waters throughout much of their range, allowing for comparison with available prey resources, growth, and survival patterns associated with the different regions.

scholarly journals Vertical Distribution of Juvenile Salmon in a Large Turbid River

2019 ◽  
Vol 10 (2) ◽  
pp. 575-581
Author(s):  
Stephanie Jump ◽  
Michael B. Courtney ◽  
Andrew C. Seitz
Keyword(s):  
Vertical Distribution ◽  
Water Column ◽  
Coho Salmon ◽  
Pacific Salmon ◽  
Fish Distribution ◽  
Oncorhynchus Keta ◽  
Juvenile Salmon ◽  
Catch Per Unit Effort ◽  
Juvenile Pacific Salmon ◽  
The Vertical Distribution

Abstract We know very little about the vertical distribution of downstream-migrating juvenile Pacific salmon Oncorhynchus spp. in large rivers. It is important for project engineers and fisheries managers to understand the potential interactions of fishes with in-river hydrokinetic devices, which harness a river's energy by spinning a turbine to produce electrical current without damming or impounding water. Currently, several rural Alaskan communities are considering development projects for hydrokinetic devices, including projects in the Tanana River, near Nenana, Alaska. Therefore, the goal of this study was to determine the vertical distribution of juvenile Chinook Salmon Oncorhynchus tshawytscha, Coho Salmon Oncorhynchus kisutch, and Chum Salmon Oncorhynchus keta, in the Tanana River, at a site (bottom depth ∼ 8, channel width ∼ 150 m) where communities may deploy future hydrokinetic turbines. Using a suspended wingless fyke net system during diurnal periods (0800–1800 hours), we found juveniles of all three species at all depths of the water column and no significant differences in catch-per-unit-effort among four depth categories (surface, midwater, deep water, bottom water). The occurrence of juvenile salmon throughout the water column indicates that they may interact with hydrokinetic devices, regardless of their depth. Future research to more comprehensively characterize fish distribution patterns and describe the outcomes of fish–turbine interactions may inform practices aimed at reducing potentially deleterious impacts of hydrokinetic devices on juvenile Pacific salmon.

Predation of Juvenile Pacific Salmon by the Common Merganser (Mergus merganser) on Eastern Vancouver Island. I: Predation during the Seaward Migration

1987 ◽  
Vol 44 (5) ◽  
pp. 941-949 ◽  
Author(s):  
C. C. Wood
Keyword(s):  
Mortality Rate ◽  
Prey Size ◽  
Pacific Salmon ◽  
Size Selection ◽  
Juvenile Salmonids ◽  
Seaward Migration ◽  
Mergus Merganser ◽  
The Common ◽  
Tidal Waters ◽  
Common Merganser

Predation of juvenile salmonids by the common merganser (Mergus merganser) was investigated during the period of seaward migration in two streams where fish populations are enhanced by spawning channels and hatcheries. Observation of foraging behaviour and crop-gullet contents indicated that, during this period, mergansers foraging on freshwater reaches of the streams ate juvenile salmonids almost exclusively whereas those foraging on tidal waters rarely ate salmonids. Maximum rates of salmonid mortality were estimated by assessing merganser abundance and the pattern of foraging activity on fresh versus tidal waters. Maximum mortality rate declined as fish abundance increased (i.e. mortality was depensatory) in all cases where the effects of prey size-selection could be ignored owing to an overwhelming abundance of one prey species. Bounds on maximum mortality rate by species for the entire migration period were computed under different hypotheses about the prey size-selection habits of mergansers; maximum mortality rate did not exceed 10% for any salmonid species over the entire seaward migration.

Assessing estuaries as stopover habitats for juvenile Pacific salmon

2016 ◽  
Vol 559 ◽  
pp. 201-215 ◽  
Author(s):  
JW Moore ◽  
J Gordon ◽  
C Carr-Harris ◽  
AS Gottesfeld ◽  
SM Wilson ◽  
...  
Keyword(s):  
Pacific Salmon ◽  
Juvenile Pacific Salmon

A Climate-Mediated Shift in the Estuarine Habitat Mosaic Limits Prey Availability and Reduces Nursery Quality for Juvenile Salmon

2021 ◽  
Author(s):  
Melanie J. Davis ◽  
Isa Woo ◽  
Christopher S. Ellings ◽  
Sayre Hodgson ◽  
David A. Beauchamp ◽  
...  
Keyword(s):  
Prey Availability ◽  
Juvenile Salmon ◽  
Estuarine Habitat ◽  
Habitat Mosaic ◽  
Nursery Quality

The Ecology of Juvenile Salmon in the Northeast Pacific Ocean: Regional Comparisons

2007 ◽  
Keyword(s):  
Fish Assemblages ◽  
Pacific Salmon ◽  
California Current ◽  
Minor Component ◽  
Species Group ◽  
Juvenile Salmon ◽  
Species Assemblages ◽  
Coastal Species ◽  
Night And Day ◽  
Associated Species

Abstract.—We compared epipelagic fish assemblages associated with juvenile (ocean-age 0) Pacific salmon <em>Oncorhynchus </em>spp. from neritic waters of the California Current and Alaska Current regions in the spring–summer and summer–fall periods of 2000–2004. Catches originated from rope trawl surveys conducted between latitudes 37°N and 60°N and spanned more than 1,100 km in the coastal and inshore habitats of each region. Catch data were used from the epipelagic sampling of waters from near surface to depths of about 18 m, primarily over the continental shelf. Catch composition, frequency of occurrence, and density were evaluated between regions and habitats for day sampling. Diel (night and day) catch comparisons were also made at a few localities in each region. In day catches from both regions, a total of 1.69 million fish and squid representing 52 fish families and 118 fish species were sampled from 2,390 trawl hauls. Ninety-seven percent of the daytime catch was composed of 11 fish families and squid in coastal and inshore habitats of each region: clupeids dominated catches in the California Current (72% and 76% of catch, respectively), and salmonids dominated catches in the Alaska Current (46% and 62% of catch, respectively). Juveniles comprised 81–99% of salmon sampled in both coastal and inshore habitats of each region. Frequencies of occurrence were highest for juvenile salmon in both regions, but average densities were highest for Pacific herring <em>Clupea pallasii </em>and Pacific sardine <em>Sardinops sagax </em>in the California Current region. Cluster analyses revealed distinct geographic breakpoints in coastal species assemblages off central Vancouver Island and in inshore species assemblages in southeastern Alaska. Species were found to cluster into six groups from coastal localities and four groups from inshore localities. Indicator species analysis and nonmetric multidimensional scaling revealed that most species of juvenile salmonids were located in northern localities. Although juvenile salmon had the most uniform distribution of any species group, their densities relative to associated species were dramatically lower in the California Current, suggesting a higher degree of interactions between juvenile salmon and other species in this region. Diel comparisons in both regions indicated substantially higher catches at night, particularly of clupeids, osmerids, and gadids. Salmonids were a relatively minor component of the night catch in both regions due to dramatic diel shifts in community structure. Additional study of diel interactions of juvenile salmon and associated species is needed to quantify habitat utilization dynamics in marine ecosystems.

Managing Centrarchid Fisheries in Rivers and Streams

2019 ◽  
Keyword(s):  
Community Structure ◽  
Stable Isotope ◽  
Prey Availability ◽  
Prey Selection ◽  
Trophic Position ◽  
Trophic Niche ◽  
Smallmouth Bass ◽  
Spatial Differences ◽  
Stream Size ◽  
Diet Analyses

<em>Abstract.</em>—Prey selection and diet are highly plastic and can vary with temporal and spatial differences in competition or prey availability. This study investigated the possibility that the trophic position of Smallmouth Bass <em> Micropterus dolomieu </em>might change in response to systematic, hierarchical variation in community structure in stream networks. We hypothesized that a shift toward increased insectivory and decreased piscivory would be observed in smaller streams, resulting in a lower trophic position of Smallmouth Bass and reflecting differences in community structure and prey availability. We applied a combination of diet analyses and stable isotope methods to compare prey selection and trophic position of Smallmouth Bass across a range of stream sizes. Stable isotope analyses indicated that Smallmouth Bass trophic position was slightly elevated in smaller watersheds, contradicting our initial hypothesis. However, differences in average trophic position in watershed size categories were small (ranging from 3.6 to 3.8) and of limited ecological significance. Isotopic niche width did not vary among stream size categories, and gut content analyses revealed no differences in frequency of occurrence of fish, crayfish, or insects (larvae and adults). Collectively these results indicate that trophic position, and perhaps trophic niche, of Smallmouth Bass are consistent across hierarchical variation in stream size and habitat.

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