Patterns of Timing and Size of Wild Coho Salmon (Oncorhynchus kisutch) Smolts Migrating from the Keogh River Watershed on Northern Vancouver Island

1989 ◽  
Vol 46 (7) ◽  
pp. 1086-1094 ◽  
Author(s):  
J. R. Irvine ◽  
B. R. Ward
Keyword(s):  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Optimal Timing ◽  
River Watershed ◽  
Fast Growing ◽  
Additional Work ◽  
Early Peak ◽  
Mean Size ◽  
The Mean ◽  
Two Peaks

Coho salmon (Oncorhynchus kisutch) smolts leaving the Keogh River and its tributaries demonstrated consistent patterns in their timing and size. An initial early peak in the mean size of migrating smolts occurred several weeks before the peak in their timing, and in several years when smolt migration was monitored until July, a late peak in size occurred near the end of the smolt migration. Changes in the mean size of smolts were not related to their origin within the watershed, and varying age compositions were only partially responsible for the two peaks in mean size. Fish overwintering in tributary lakes grew faster than fish overwintering in tributary streams. A greater proportion of lake-origin smolts migrated to sea after only 1 yr in freshwater than stream-origin smolts. It appears that fish that wait until their second spring to smoltify are among the first to emigrate that spring. These relatively large 2 + smolts, combined with fast growing 1 + smolts that leave early during their first spring, cause the first peak in size. The small numbers of large smolts leaving the Keogh River at the ends of several of the smolt runs apparently left then because of minor flow increases in the river. As has been found with releases of coho smolts from nearby hatcheries, fish that left the Keogh River early in the smolt run generally had a more northerly marine catch distribution than later migrating smolts. A greater proportion of fish migrating to sea late in the smolt run were caught in the fishery than fish migrating early. Additional work examining the marine survival of early and late migrating wild smolts is recommended to enable detailed comparisons to be made between the optimal timing and size of wild and hatchery smolts.

Reproductive biology of Eledone moschata (Cephalopoda: Octopodidae) in the Aegean Sea (Izmir Bay, Turkey)

2007 ◽  
Vol 87 (4) ◽  
pp. 967-970 ◽  
Author(s):  
Okan Akyol ◽  
Halil Şen ◽  
H. Tuncay Kınacıgil
Keyword(s):  
Gonadosomatic Index ◽  
Aegean Sea ◽  
Monthly Basis ◽  
The North ◽  
Eastern Aegean ◽  
North Eastern ◽  
Winter Peak ◽  
Mean Size ◽  
The Mean ◽  
Two Peaks

Reproductive properties of Eledone moschata from the north-eastern Aegean Sea are reported for the first time. A total of 471 specimens was collected during monthly samplings from December 2004 to November 2005. The mantle lengths of the species were between 4.5 and 15.0 cm with an average of 8.1 cm ±0.15 for 204 males, and between 2.7 and 14.0 cm with an average of 7.8 cm ±0.12 for 267 females. The annual sex ratio (males: females) of the sampled specimens was 1:1.31. Maturity stages were recorded on a monthly basis in both sexes. The highest monthly percentage of mature females (21%) and males (46%) was recorded in January 2005 and June 2005, respectively. The monthly and seasonal gonadosomatic index (GSI) results indicated that E. moschata shows two annual reproduction peaks for each sex. For males, the first spring peak occurs in March–June and the second, autumn peak is in November. For females, the first summer peak occurs in May–June and the second, winter peak is in January, respectively. On the other hand, the reproductive season extends from November to July with two peaks in the Aegean Sea. Total oocyte stock varied from 273 to 2896 with a mean of 836 ±193 oocytes. The mean size of the oocytes was 6.26 ±0.10 mm. The maximum oocyte size found was 10.7 mm. The mean length of spermatophores was of 13.66 ±0.08 mm (range: 7.3–18.3) and their average number was 52 ±6 (range: 6–172).

Effects of Gravel Size, Egg Depth, and Egg Density on Intragravel Movement and Emergence of Coho Salmon (Oncorhynchus kisutch) Alevins

1970 ◽  
Vol 27 (7) ◽  
pp. 1191-1199 ◽  
Author(s):  
L. M. Dill ◽  
T. G. Northcote
Keyword(s):  
Environmental Variables ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
High Density ◽  
Low Density ◽  
Gravel Size ◽  
Egg Density ◽  
The Mean

In experimental aquaria with large gravel (3.2–6.3 cm), vertical and lateral movements of coho salmon (Oncorhynchus kisutch) alevins were more extensive and area utilized per alevin was greater than in small gravel (1.9–3.2 cm). At low density (50 per aquarium) the alevins moved farther towards the inlet, but the mean area occupied per alevin was the same as that at high density (100 per aquarium). Burial depths tested (20 and 30 cm) had no significant effect on vertical or lateral movements or on area utilized per alevin. Alevin orientation in the gravel, survival to emergence, and timing of emergence were not affected by any of the environmental variables examined.

Survival, Ocean Growth, and Ocean Distribution of Differentially Timed Releases of Hatchery Coho Salmon (Oncorhynchus kisutch)

1989 ◽  
Vol 46 (7) ◽  
pp. 1216-1226 ◽  
Author(s):  
Stephen B. Mathews ◽  
Yukimasa Ishida
Keyword(s):  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Adult Survivors ◽  
Small Fish ◽  
Large Fish ◽  
Release Date ◽  
Marine Life ◽  
Coos Bay ◽  
The Mean ◽  
Marine Survival

Estimates of growth rates in early ocean life and length frequency distributions at time of release for adult survivors were inferred from scale measurements for lots of coho salmon (Oncorhynchus kisutch) released at several dates from a Columbia River hatchery (Big Creek) and a southern Oregon hatchery (Coos Bay). Analysis of these measurements failed to support either of two literature-suggested hypotheses for the variability of marine survival of hatchery coho by date of release: (1) intraseasonal variability of food supply during early marine life; and (2) intraseasonally improving ability of smaller individuals within release lots to convert to salt water. Marine survival improved substantially with date of release at both hatcheries. However, fish released earliest, which survived relatively poorly, grew as fast in early marine life as fish released later, which survived better. Thus, poor survival of the early released fish did not appear related to lack of food at early ocean life. For the Big Creek hatchery, no significant differences were seen between the mean lengths at date of release and the mean release-date lengths of adult survivors back calculated from their scales, for lots released on May 5, June 3, and July 2. Apparently, small and large fish of each lot survived with equal probability. For the Coos Bay hatchery, the mean release-date lengths of adult survivors were significantly larger than the mean lengths of all fish released, for each of six lots released between early June and late July. Thus, large fish apparently survived better than small ones within each of these six lots. But there was no seasonal trend in survivability of small fish relative to large ones, contrary to hypothesis (2)

Electrophoretic Variation, Regional Differences, and Gene Flow in the Coho Salmon (Oncorhynchus kisutch) of Southern British Colombia

1987 ◽  
Vol 44 (4) ◽  
pp. 822-831 ◽  
Author(s):  
C F. Wehrhahn ◽  
R. Powell
Keyword(s):  
British Columbia ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Ice Age ◽  
Enzyme Loci ◽  
Large Populations ◽  
Last Ice Age ◽  
The Mean ◽  
British Colombia ◽  
River Fish

Populations of coho salmon (Oncorhynchus kisutch) in southern British Columbia were assayed for genetic variation at 26 enzyme loci. The mean heterozygosity was only 0.25 ± 0.06%. Previously studied wild Oregon cohos had a mean heterozygosity of 1.36 ± 0.37% compared with 0.30 ± 0.09% in Lower Coastal Mainland and 0.13 ± 0.08% in Upper Fraser River fish for the same enzyme loci. A plausible explanation for the very low mean heterozygosity is that British Columbia coho salmon went through an extreme population bottleneck during or after the last ice age. Lower Coastal Mainland salmon are significantly different from the fish of Vancouver Island and can be easily distinguished from Oregon and Capilano Hatchery (Coastal Mainland, B.C.) fish, it should be feasible to determine the relative proportions of different stocks in large oceanic coho salmon samples. The maximum likelihood estimate of the migration rate between spawning populations is 5.8 ± 1.2 breeding adults per generation. This is enough to prevent adaptation to local habitats by small populations of fewer than 100 breeding adults, but it is not high enough to impede selection in large populations of 1000 or more breeding adults.

Bias in hatchery-origin coho salmon survival estimates due to underestimated prerelease mortality

2021 ◽  
pp. 1-4
Author(s):  
James R. Irvine
Keyword(s):  
British Columbia ◽  
Experimental Evidence ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Data Sets ◽  
Wild Salmon ◽  
Natural Origin ◽  
Additional Work ◽  
Seaward Migration ◽  
Over Time

The widely accepted belief that hatchery-origin salmon survive less well than natural-origin or wild salmon can be, at least in part, an artifact of the way hatchery salmon survival is estimated. Hatchery salmon are often marked several months before release, while natural salmon are marked during their seaward migration. Underestimated prerelease mortalities result in biased low survival estimates. In British Columbia, although hatchery rearing practices have been modified to reduce unrecorded mortalities, experimental evidence indicates that coho salmon (Oncorhynchus kisutch) smolt survivals continue to be underestimated by ∼13%. Better reporting and incorporation of survival bias in data sets and analyses as well as additional work to evaluate bias for other regions and species over time is needed.

Overwintering habitats of coho salmon (Oncorhynchus kisutch) and other juvenile salmonids in the Keogh River system, British Columbia

1988 ◽  
Vol 66 (1) ◽  
pp. 254-261 ◽  
Author(s):  
S. Swales ◽  
F. Caron ◽  
J. R. Irvine ◽  
C. D. Levings
Keyword(s):  
Gasterosteus Aculeatus ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Cutthroat Trout ◽  
River System ◽  
Salmo Gairdneri ◽  
Dolly Varden Char ◽  
Main River ◽  
The Mean ◽  
Density And Biomass

Catches of overwintering juvenile coho salmon (Oncorhynchus kisutch) in the Keogh River system, Vancouver Island, were higher in two small (8 and 25 ha), shallow (mean depth 2 – 3 m) lakes and their outlet and inlet streams than in the main river, where steelhead trout (Salmo gairdneri) were predominant. Dolly Varden char (Salvelinus malma), cutthroat trout (Salmo clarki), and threespine stickleback (Gasterosteus aculeatus) were also present in the lakes. The distribution of coho salmon in the lakes was restricted largely to areas close to the bank, with few fish being captured in offshore areas or in mid-water. Apparent differences in the abundance of coho salmon between the two lakes may have been related to differences in fish community composition, with sticklebacks being particularly numerous in Misty Lake, where catches of coho salmon were lower than in Long Lake. The population density and biomass of coho salmon overwintering in Long Lake were estimated to be 176 fish/ha and 1.14 kg ha−1, respectively. The mean length of coho salmon in the lakes was greater than that of coho salmon in the tributary streams and main river, and the mean length of the salmon in the lakes generally increased with distance away from shore.

Study of the first blastomeres in Coho salmon (Oncorhynchus kisutch)

Zygote ◽  
2012 ◽  
Vol 21 (2) ◽  
pp. 151-157 ◽  
Author(s):  
Brian Effer Roldán ◽  
Rubén Sánchez Rueda ◽  
Andrea Ubilla Madrid ◽  
Elías Figueroa Villalobos ◽  
Iván Valdebenito Isler
Keyword(s):  
Embryonic Development ◽  
Diagnostic Tool ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Normal Appearance ◽  
Cell Stage ◽  
Lack Of Information ◽  
The Mean

SummaryThere is a lack of information on the morphology of the first blastomeres that could be used as a diagnostic tool for the first stages of embryonic development for Coho salmon. The purpose of this investigation, therefore, was to characterize morphometrically the first blastomeres of Coho salmon (Oncorhynchus kisutch). In total, 660 embryonic discs from a pool of eggs that had been fertilized and incubated at 5°C and after 19 h of incubation were extracted and photographed. Of these, 20 microphotographs of blastodiscs of normal appearance were analyzed morphologically (control blastodiscs: CB) and 100 random microphotographs from the whole group were classified as either symmetrical or asymmetrical according to their morphology and then compared with the CB. The length and width of each blastomere and the proportions of length and width were measured to determine symmetry in the embryos at the 4-cell stage. Seven categories were created to characterize the blastomeres: 38% normal (G1); 26% unequal (G2); 10% ‘pie-shaped’ (G3); 10% amorphous (G4); 8% with three equal and one unequal blastomere (G5); 6% ‘clover-shaped’ blastomeres (G7), and 3% with inclusions. The mean of the proportions of lengths and widths of the groups of blastomeres that were measured was 0.87 ± 0.08 and 0.85 ± 0.07, respectively. The morphometric results that were obtained in this investigation are compared with the results observed by other authors for teleostei and are discussed.

Effects of nonrandom mating schemes to delay the inbreeding accumulation in cultured populations of coho salmon (Oncorhynchus kisutch)

2004 ◽  
Vol 61 (4) ◽  
pp. 547-553 ◽  
Author(s):  
José A Gallardo ◽  
Jean Paul Lhorente ◽  
Ximena García ◽  
Roberto Neira
Keyword(s):  
Coho Salmon ◽  
Random Mating ◽  
Oncorhynchus Kisutch ◽  
Linear Unbiased Prediction ◽  
Breeding Values ◽  
Nonrandom Mating ◽  
The Family ◽  
Best Linear Unbiased ◽  
The Mean ◽  
High Degree

Chilean salmon culture is based on a high degree of artificial selection, which has had the tendency to increase the inbreeding (F). Three types of nonrandom mating were evaluated to control the inbreeding in two best linear unbiased prediction selected coho salmon (Oncorhynchus kisutch) populations (even and odd). These included compensatory mating on the basis of breeding values (C), modified compensatory mating (C1) based on the family mean of breeding values, and mating that minimized the mean co-ancestry of the group selected (MC scheme). In the odd population, the MC scheme (F = 2.0%) reduced the increase in inbreeding of the next generation by 50% and 46% when compared with random mating of selected individuals with sib mating restricted (F = 3.9%) and with C (F = 3.7%), respectively. In the even population, the MC scheme reduced the increase in inbreeding by 14% compared with C1 (9.7 versus 11.2). In both populations, the MC scheme also reduced variance in inbreeding (even, 59%; odd, 39%). Thus, the MC scheme was more efficient in reducing the increase and variance of inbreeding, thus limiting the expression of inbreeding depression. Although the MC scheme was more time consuming, we recommend this scheme to carry out crosses in each generation.

Plasma Testosterone Concentration Predicts the Ovulatory Response of Coho Salmon (Oncorhynchus kisutch) to Gonadotropin-Releasing Hormone Analog

1987 ◽  
Vol 44 (7) ◽  
pp. 1351-1357 ◽  
Author(s):  
Martin S. Fitzpatrick ◽  
J. Michael Redding ◽  
Frank D. Ratti ◽  
Carl B. Schreck
Keyword(s):  
Coho Salmon ◽  
Plasma Concentrations ◽  
Oncorhynchus Kisutch ◽  
Gonadotropin Releasing Hormone ◽  
Plasma Testosterone ◽  
Releasing Hormone ◽  
Hormone Analog ◽  
Before And After ◽  
The Mean ◽  
Estradiol 17Β

Plasma concentrations of testosterone, 17α-hydroxy-20β-dihydroprogesterone (DHP), and estradiol-17β were determined in hatchery populations of adult female coho salmon (Oncorhynchus kisutch) before and after the fish were injected with gonadotropin-releasing hormone analog (GnRHa) to accelerate ovulation. Treatment with GnRHa significantly accelerated maturation over that observed in saline-injected controls; however, a number of females that received GnRHa did not ovulate for as long as 8 wk after treatment. Before treatment, the mean plasma levels of DHP did not differ between early- and late-ovulating females; estradiol differed sometimes, but not always; and testosterone was always higher in the early-ovulating fish. Thus, plasma concentrations of testosterone appear to be useful for predicting the sensitivity of coho salmon to GnRHa treatment for induced ovulation.

Batch Precipitation of Lead Iodide

1994 ◽  
Vol 59 (6) ◽  
pp. 1301-1304
Author(s):  
Jaroslav Nývlt ◽  
Stanislav Žáček
Keyword(s):  
Aqueous Solution ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Crystal Size ◽  
Lead Nitrate ◽  
Lead Iodide ◽  
Constant Rate ◽  
Mean Size ◽  
The Mean

Lead iodide was precipitated by a procedure in which an aqueous solution of potassium iodide at a concentration of 0.03, 0.10 or 0.20 mol l-1 was stirred while an aqueous solution of lead nitrate at one-half concentration was added at a constant rate. The mean size of the PbI2 crystals was determined by evaluating the particle size distribution, which was measured sedimentometrically. The dependence of the mean crystal size on the duration of the experiment exhibited a minimum for any of the concentrations applied. The reason for this is discussed.

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