Influence of Four Species of Helminth Parasites on Orientation of Seaward Migrating Sockeye Salmon (Oncorhynchus nerka) Smolts

1990 ◽  
Vol 47 (12) ◽  
pp. 2380-2389 ◽  
Author(s):  
E. Garnick ◽  
L. Margolis
Keyword(s):  
Sockeye Salmon ◽  
Random Distribution ◽  
Parasite Species ◽  
Oncorhynchus Nerka ◽  
Parasite Infection ◽  
Lake Area ◽  
Helminth Parasites ◽  
Considerable Variability ◽  
Migratory Behaviour ◽  
Diphyllobothrium Dendriticum

Each of four helminth parasite species, including the cestodes Eubothrium salvelini, Diphyllobothrium dendriticum, and Proteocephalus sp. and the nematode Philonema oncorhynchi, was found to influence the orientation of seaward-migrating sockeye salmon (Oncorhynchus nerka) smolts from the Great Central Lake area, Vancouver Island, British Columbia. Smolts placed in circular tanks were allowed to exit into evenly spaced bucket traps, and fish from five such runs were measured, sexed, and examined for the presence of parasites. Fish were categorized on the basis of infection status ("+" vs. "−") for each of the four parasite species found. The +/− groups did not differ for any of the parasite categories with respect to either bucket distributions or overall orientation directions. However, "−" groups did exhibit consistently greater departure from random distribution than their "+" counterparts. This finding suggests interference of parasites with smolt orientation, which could in turn have important implications for smolt survival. This finding also suggests that parasite infection may account to some extent for the considerable variability observed in the migratory behaviour of smolts.

The distribution of plerocercoids of Diphyllobothrium dendriticum (Nitzsch) in sockeye salmon (Oncorhynchus nerka) smolts from Great Central Lake, British Columbia

1988 ◽  
Vol 66 (4) ◽  
pp. 850-852 ◽  
Author(s):  
Hilda Lei Ching
Keyword(s):  
British Columbia ◽  
Body Length ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Vancouver Island ◽  
Infected Fish ◽  
Mean Intensity ◽  
Diphyllobothrium Dendriticum ◽  
Pyloric Ceca

Sockeye salmon (Oncorhynchus nerka) from Great Central Lake, Vancouver Island, British Columbia, were sampled in May of 1986 and 1987 to study the locations and sizes of plerocercoids of Diphyllobothrium dendriticum. In 1986, 93% of 59 smolts were infected with a total of 222 plerocercoids (mean intensity ± SE, 4.0 ± 3.4; range, 1–15). In 1987, 77% of 168 smolts were infected with a total of 341 plerocercoids (mean ± SE, 2.6 ± 1.8; range, 1–9). More than 75% of the infected fish contained one to three plerocercoids, which were more often found free in the musculature than encysted in the viscera. Plerocercoids occurred most frequently in the midepaxial and midhypaxial musculature and encysted on the stomach and pyloric ceca. Plerocercoids varied in body length: those from the stomach area were <2 mm, and those in the viscera and musculature were 3–10 mm (a few from the musculature were >10 mm).

Downstream and Early Marine Migratory Behaviour of Sockeye Salmon (Oncorhynchus nerka) Smolts Entering Barkley Sound, Vancouver Island

1993 ◽  
Vol 50 (6) ◽  
pp. 1329-1337 ◽  
Author(s):  
Chris C. Wood ◽  
N. Brent Hargreaves ◽  
Dennis T. Rutherford ◽  
Brian T. Emmett
Keyword(s):  
Surface Waters ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Vancouver Island ◽  
Migratory Behaviour ◽  
Merluccius Productus ◽  
Barkley Sound ◽  
Tidal Waters ◽  
Single Night ◽  
Catch Rates

Behaviour of sockeye salmon (Oncorhynchus nerka) smolts was studied during their migration down the Stamp and Somass rivers and through Alberni Inlet and Barkley Sound, Vancouver Island. Emigration from Great Central Lake was typical of other sockeye lakes: smolt abundance peaked in early May and most smolts left the lake at dusk. Migration down the rivers occurred only during twilight or darkness and most smolts made the 25-km journey to tidal waters within a single night. Those that did not held position in tight schools in the surface waters of deep pools during daylight. During downstream migration, ground speed averaged about 2.5 km/h, and smolts did not appear to be especially vulnerable to predation owing to their short residence time, with few smolts remaining in the river during daylight. Catch rates at purse-seine sampling sites throughout Alberni Inlet and Barkley Sound indicated that sockeye smolts migrated more slowly in tidal waters and were sometimes highly vulnerable to predaceous fish (especially Pacific hake, Merluccius productus). Estimated migration speeds through Alberni inlet were 1.9 km/d for smolts entering tidal waters during April and May, and 1.3 km/d for those during June and July; speed through Barkley Sound was 1.6 km/d throughout May–July.

Fish age, nematode (Philonema oncorhynchi) infection, and development of sexual dimorphism by the adult male sockeye salmon, Oncorhynchus nerka, in western Alaska

1995 ◽  
Vol 73 (11) ◽  
pp. 1999-2004 ◽  
Author(s):  
Ole Kristian Berg ◽  
Chris J. Foote ◽  
Thomas P. Quinn
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Parasite Infection ◽  
Mature Male ◽  
Sexually Dimorphic ◽  
Age Composition ◽  
Body Depth ◽  
Duration Of Residence ◽  
Significant Difference ◽  
Seaward Migration

Of 255 mature male sockeye salmon (Oncorhynchus nerka) from two Alaskan lakes (Aleknagik and Iliamna), 254 (99.6%) were infected with the nematode Philonema oncorhynchi with a mean wet mass of 3.1 g (SD = 3.4 g) of nematodes. Fish that had spent 1 year in the lake prior to seaward migration had significantly lower parasite masses than those that had spent 2 years in the lake (2.7 vs. 4.1 g). However, there was no significant difference in parasite masses between lakes or among spawning populations within the lakes for fish of a given age or of all ages combined, even though the populations differed in age composition. The variation in relative parasite mass (mass of parasite (g)/mass of fish (kg)) was mainly explained by the significant variation in total mass of the parasites and the sea age of the fish. Thus, total parasite mass was correlated with the duration of residence in fresh water, while the relative parasite mass was correlated with fish size, and hence with the duration of residence in the sea. In spite of heavy infections (up to 28 g of nematodes) in many salmon, there were no corresponding reductions in mass/length or in the development of two sexually dimorphic features, body depth and snout length. Thus, parasite infection did not appear to affect traits under sexual selection, as hypothesized by Hamilton and Zuk.

Are parasite richness and abundance linked to prey species richness and individual feeding preferences in fish hosts?

Parasitology ◽  
2015 ◽  
Vol 143 (1) ◽  
pp. 75-86 ◽  
Author(s):  
ALYSSA R. CIRTWILL ◽  
DANIEL B. STOUFFER ◽  
ROBERT POULIN ◽  
CLÉMENT LAGRUE
Keyword(s):  
Parasite Species ◽  
Parasite Infection ◽  
Fish Host ◽  
Fish Diet ◽  
Helminth Parasites ◽  
Parasite Richness ◽  
Host Diet ◽  
Parasite Infections ◽  
The Individual ◽  
Fish Hosts

SUMMARYVariations in levels of parasitism among individuals in a population of hosts underpin the importance of parasites as an evolutionary or ecological force. Factors influencing parasite richness (number of parasite species) and load (abundance and biomass) at the individual host level ultimately form the basis of parasite infection patterns. In fish, diet range (number of prey taxa consumed) and prey selectivity (proportion of a particular prey taxon in the diet) have been shown to influence parasite infection levels. However, fish diet is most often characterized at the species or fish population level, thus ignoring variation among conspecific individuals and its potential effects on infection patterns among individuals. Here, we examined parasite infections and stomach contents of New Zealand freshwater fish at the individual level. We tested for potential links between the richness, abundance and biomass of helminth parasites and the diet range and prey selectivity of individual fish hosts. There was no obvious link between individual fish host diet and helminth infection levels. Our results were consistent across multiple fish host and parasite species and contrast with those of earlier studies in which fish diet and parasite infection were linked, hinting at a true disconnect between host diet and measures of parasite infections in our study systems. This absence of relationship between host diet and infection levels may be due to the relatively low richness of freshwater helminth parasites in New Zealand and high host–parasite specificity.

Long-term changes in parasites of sockeye salmon (Oncorhynchus nerka) smolts

1998 ◽  
Vol 55 (4) ◽  
pp. 977-986 ◽  
Author(s):  
Shannon N Bennett ◽  
Martin L Adamson ◽  
Leo Margolis
Keyword(s):  
Sockeye Salmon ◽  
Parasite Species ◽  
Oncorhynchus Nerka ◽  
Parasite Community ◽  
Similar Species ◽  
Cestode Species ◽  
Parasitic Helminths ◽  
Parasite Communities ◽  
Species Pairs

Parasites were examined in 41 annual samples of sockeye salmon (Oncorhynchus nerka) juveniles originating from lakes in British Columbia: Chilko and Shuswap. Nine species of parasitic helminths and two species of parasitic Crustacea were recovered from various organs. The number of species ranged from three to nine per year. Most (94%) parasites belonged to three tapeworm species, identified as core to the parasite community because they also infected the most hosts. Two of these cestode species are probably maintained by resident freshwater hosts in the lakes. Positive numerical associations were observed between four parasite species pairs. Parasite communities in both lakes were composed of similar species, with the exception of three rare Chilko Lake species that were never recovered from Shuswap Lake. Parasites were often as variable within stock (temporally) as between stocks (geographically), except for the prevalence of Eubothrium sp. and Neoechinorhynchus sp. and mean annual intensity of Proteocephalus sp. and encysted digenetic metacercariae, which were greater at Chilko Lake than at Shuswap Lake. Discrimination between the two lakes based on their parasite community is possible only in extreme cases of infection and thus is of limited use to fisheries officers attempting to distinguish between these stocks.

On the Distribution of Young Sockeye Salmon (Oncorhynchus nerka) in Babine and Nilkitkwa Lakes, B.C.

1956 ◽  
Vol 13 (5) ◽  
pp. 695-708 ◽  
Author(s):  
W. E. Johnson
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Fishing Effort ◽  
Lake Area ◽  
Parent Population ◽  
Unequal Distribution ◽  
The North ◽  
Limited Dispersal ◽  
Mean Size ◽  
Skeena River

Babine Lake and connected Nilkitkwa Lake, a total lake area of 174 square miles, provide nursery facilities for progeny of the largest sockeye salmon run to the Skeena River in northern British Columbia.Based on catch per unit of fishing effort, tow-net collections in August and October, 1955, indicate that at least 67%, and possibly as much as 88%, of the total age 0 sockeye population of these lakes (estimated as 50 to 60 million) was concentrated in Nilkitkwa Lake and the North Arm of Babine Lake: that is, in 11.4% of the total lake area. Mean size of young sockeye in these areas of concentration was much smaller than in the sparsely populated remainder of Babine Lake.This unequal distribution of young sockeye, and resulting inefficient utilization of the lake nursery facilities, is apparently a result of the distribution of the spawning parent population and a limited dispersal of young sockeye from their points of entrance into the lake as fry.

Resumption of anadromy or straying? Origins of Sockeye Salmon Oncorhynchus nerka in the Elwha River

2021 ◽  
Author(s):  
Thomas P. Quinn ◽  
George R. Pess ◽  
Ben J.G. Sutherland ◽  
Samuel J. Brenkman ◽  
Ruth E. Withler ◽  
...  
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Elwha River

Alternative Recruitment Models of Adams River Sockeye Salmon, Oncorhynchus nerka

1987 ◽  
Vol 44 (9) ◽  
pp. 1551-1561 ◽  
Author(s):  
Jeremy S. Collie ◽  
Carl J. Walters
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Status Quo ◽  
Management Policy ◽  
Best Management ◽  
Interaction Terms ◽  
Ricker Model ◽  
The Status ◽  
Stock Recruitment ◽  
High Yields

Despite evidence of depensatory interactions among year-classes of Adams River sockeye salmon (Oncorhynchus nerka), the best management policy is one of equal escapement for all year-classes. We fit alternative models (Ricker model and Larkin model) to 32 yr of stock–recruitment data and checked, using simulation tests, that the significant interaction terms in the Larkin model are not caused by biases in estimating the parameters. We identified a parameter set (Rationalizer model) for which the status quo cyclic escapement policy is optimal, but this set fits the observed data very poorly. Thus it is quite unlikely that the Rationalizer model is correct or that the status quo escapement policy is optimal. Using the fitted stock–recruitment parameters, we simulated the sockeye population under several management policies. The escapement policy optimal under the Ricker model is best overall because of the high yields if it should be correct. If the three stock–recruitment models are equally likely to be correct, the simulations predict that adopting a constant-escapement policy would increase long-term yield 30% over the current policy and that an additional 15% increase in yield could be obtained if the policy were actively adaptive.

Reduced growth in wild juvenile sockeye salmon Oncorhynchus nerka infected with sea lice

2017 ◽  
Vol 91 (1) ◽  
pp. 41-57 ◽  
Author(s):  
S. C. Godwin ◽  
L. M. Dill ◽  
M. Krkošek ◽  
M. H. H. Price ◽  
J. D. Reynolds
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Sea Lice
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