Does mortality select size or growth potential in young sockeye salmon (Oncorhynchus nerka)? A simulation based on otolith - fish size relationships

1998 ◽  
Vol 55 (7) ◽  
pp. 1674-1681 ◽  
Author(s):  
M G Meekan ◽  
DAJ Ryan ◽  
J J Dodson ◽  
S P Good
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Fork Length ◽  
Field Studies ◽  
Growth Potential ◽  
Selective Mortality ◽  
Fish Size ◽  
Conflicting Evidence ◽  
Selection For ◽  
Otolith Size

There is conflicting evidence on the role of size-selective mortality in the demography of populations of young sockeye salmon (Oncorhynchus nerka). A previous field study suggested that increases in mean fork length and otolith size at emergence observed in a cohort of salmon between fry and smolt stages were due to size-selective mortality, such that fry with small fork lengths underwent higher mortality than larger individuals. However, a subsequent study used a simulation to show that such increases could not have been achieved by size-selective mortality without levels of survivorship of the cohort far lower than those that had been observed in the field. To account for field observations, the simulation study proposed that individuals with high metabolic rates had better survivorship, a process that was termed "selection for growth potential." Here, we use a simulation approach to show that size-selective mortality may result in shifts in mean fork length and otolith size at emergence comparable with those observed in the field at total mortalities within the range of estimates of natural values. The contrasting outcomes of earlier simulation work and the present study are probably due to the assumption by the former that otolith and fish size in young salmon were weakly correlated and the use of an inappropriate model of size-selective mortality. We conclude that size-selective mortality can explain the results of previous field studies and that little empirical evidence exists to support the hypothesis of selection for growth potential in cohorts of young salmon.

Migration Timing, Size, and Salinity Tolerance of Sea-Type Sockeye Salmon (Oncorhynchus nerka) in an Alaska Estuary

1989 ◽  
Vol 46 (4) ◽  
pp. 633-637 ◽  
Author(s):  
Jonathan Heifetz ◽  
Scott W. Johnson ◽  
K V. Koski ◽  
Michael L. Murphy
Keyword(s):  
Salinity Tolerance ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
River Estuary ◽  
Fork Length ◽  
Habitat Types ◽  
Southeast Alaska ◽  
Fish Size ◽  
Migration Timing

Migration timing, size, and salinity tolerance were determined for sea-type sockeye salmon (Oncorhynchus nerka), which migrate to sea as underyearlings (age-0), in the Situk River estuary, Southeast Alaska. Ten sites in three habitat types were seined monthly from Sate April through August, 1987, and age-0 sockeye from the estuary were tested for salinity tolerance. Age-0 sockeye were most abundant (up to 13∙m−2) from late April through June, and by late July, most sockeye had left the estuary. Mean fork length (FL) was 31 mm in April and increased 0.4 mm∙d−1 to 70 mm in late July when most (72%) remaining sockeye had grown to about the same size as age-1 smolts (69–95 mm) emigrating in May and June. Mean FL of age-0 sockeye in the estuary in July was 23 mm greater than in freshwater areas of the river. Salinity tolerance was directly related to fish size, and a size of at least 50 mm was required for 100% survival in seawater. Because salinity in the estuary ranged 0–30‰, sockeye of all sizes could survive in the estuary. Thus, in 3–4 mo, sea-type sockeye attained a size large enough to adapt to seawater and migrate to sea.

Evidence for Size-Selective Mortality of Juvenile Sockeye Salmon (Oncorhynchus nerka) in Babine Lake, British Columbia

1987 ◽  
Vol 44 (4) ◽  
pp. 712-721 ◽  
Author(s):  
Cameron J. West ◽  
P. A. Larkin
Keyword(s):  
British Columbia ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Length Distribution ◽  
Fork Length ◽  
Late Summer ◽  
Selective Mortality ◽  
Daily Growth ◽  
Back Calculation ◽  
Spawning Tributaries

Otolith – body length relations and back-calculation procedures were used to test the hypothesis that mortality of juvenile sockeye salmon (Oncorhynchus nerka) in Babine Lake, British Columbia, is size selective. Samples of the 1978 brood of sockeye were collected as fry from spawning tributaries as juveniles in the main basin, and as smolts at the outlet. Total otolith length was chosen as the most useful otolith dimension for back-calculation of fork length at emergence. Sockeye from the various tributaries show different fork length – otolith length relationships necessitating a weighting procedure for comparisons involving samples of mixed stocks from the lake. Instantaneous daily growth rate and In fork length during the early lake-rearing period were significantly correlated. Smaller juveniles grew more slowly than larger individuals in mid-july, and a hierarchy of sizes was maintained. The distributions of total otolith length at emergence for fry, surviving juveniles, and smolts indicate selective mortality of fish with smaller otoliths, hence of small size at emergence. Survivals from the lower and upper halves of the initial total otolith length distribution were 8.9 and 63.6%, respectively. Comparable estimates for back-calculated fork lengths at emergence were 27.2 and 43.4%. Size-selective mortality is most intense in the late summer and early autumn, and may be associated with predation and parasitism.

Swimming Thrust of Sockeye Salmon (Oncorhynchus nerka) in Relation to Selectivity of Gillnets

1969 ◽  
Vol 26 (5) ◽  
pp. 1383-1385 ◽  
Author(s):  
R. H. Lander
Keyword(s):  
Significant Relationship ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Fork Length

A significant relationship between girth at the mesh mark and fork length indicates that long sockeye salmon (Oncorhynchus nerka) have more swimming thrust than short ones. This tends to confirm a speculation of Regier and Robson (J. Fish. Res. Bd. Canada 23: 423–454, 1966). Preliminary conjecture relates the observation to the theory of mesh selectivity.

The Fate of 14C Labeled Food Ingested by Underyearling Sockeye Salmon, Oncorhynchus nerka, in Relation to Temperature and Ration

1980 ◽  
Vol 37 (7) ◽  
pp. 1184-1192 ◽  
Author(s):  
R. M. Biette ◽  
G. H. Geen
Keyword(s):  
Constant Temperature ◽  
Low Temperatures ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Growth Potential ◽  
Short Term ◽  
Respiration Rates ◽  
Cyclic Temperature ◽  
Temperature Constant ◽  
Ration Size

Underyearling sockeye salmon (Oncorhynchus nerka) provided rations likely available in nature grow more rapidly when held under cyclic than under constant temperature. The basis of this enhancement was investigated by following the short-term fate of labeled food in young sockeye fed low (3.4% dry body wt/d) and moderate (6.4% dry body wt/d) rations and maintained under constant and cyclic temperatures. These experiments, corrected for low 14C measured rates of respiration, indicated that growth potential of young sockeye is greater under cyclic temperatures because of the higher respiration rates at constant high temperatures and the greater rates of defecation and excretion at low temperatures. The difficulties in estimating respiration rates from 14CO2 measurements are emphasized.Key words: sockeye salmon, 14C-labeled feeding, incorporation, respiration, excretion, defecation, diel vertical migration, diel cyclic temperature, constant temperature, ration size

Growth Rate of Young Sockeye Salmon, Oncorhynchus nerka, in Relation to Fish Size and Ration Level

1975 ◽  
Vol 32 (11) ◽  
pp. 2103-2110 ◽  
Author(s):  
J. R. Brett ◽  
J. E. Shelbourn
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Sockeye Salmon ◽  
Specific Growth ◽  
Oncorhynchus Nerka ◽  
Limiting Factor ◽  
Fish Size ◽  
Ration Level ◽  
The Family ◽  
Constant Growth

The specific growth rate of young sockeye salmon (Oncorhynchus nerka) was studied for a period of 7 mo to determine the effect of body weight when on restricted and unrestricted rations. It was hypothesized that a restricted ration would result in a fixed growth rate until size became a limiting factor reducing food demand below the prescribed level and thereby reducing growth rate. The results support the hypothesis, with the possible exception that growth rate may increase slightly during the period of fixed ration. On excess ration the specific growth rate fell from 3.6% weight per day (2.4 g mean weight) to 1.0% weight per day (37 g mean weight); intermediate constant growth rates accompanied the periods of fixed ration, inflecting to lower rates subsequently. The general equation log G = a + b log W (where G = specific growth rate, and W = weight in grams) was found to apply to a number of salmonids. The slope value of b = −0.4 ±.04 appears to characterize the family, with the intercept a taking on different values according to the varying capacity for rapid growth.

Host–Parasite Relationships Between Sockeye Salmon, Oncorhynchus nerka, and Salmincola californiensis (Copepoda: Lernaeopodidae)

1977 ◽  
Vol 34 (2) ◽  
pp. 191-202 ◽  
Author(s):  
Z. Kabata ◽  
B. Cousens
Keyword(s):  
Sockeye Salmon ◽  
Body Wall ◽  
Oncorhynchus Nerka ◽  
Mechanical Damage ◽  
Fork Length ◽  
Parasitic Copepod ◽  
Size Groups ◽  
Branchial Cavity ◽  
Host Parasite ◽  
First Time

The distribution of the parasitic copepod, Salmincola californiensis, on two size-groups (fry, fork length 3.2–5.8 cm; juveniles, fork length 10.2–27.0) of the sockeye salmon, Oncorhynchus nerka, is described. The existence of preferred sites for both groups is established. The distribution on the smaller fish differs from that on the larger in that on the former the copepods are most abundant in the region of pectoral and pelvic fins, whereas on the latter they are by far most common in the branchial cavity. Macroscopic and microscopic mechanical damage to the fish tissues, resulting from the presence and activity of the copepod, comprises injuries to gills, skin, muscle, and even bone. The "burrowing phenomenon" (failure on the part of the copepod to cease excavation of a completed cavity of implantation, resulting in perforation of body wall and penetration of the viscera) is reported upon for the first time.

Sex-specific differences in physiological recovery and short-term behaviour following fisheries capture in adult sockeye salmon (Oncorhynchus nerka)

2020 ◽  
Vol 77 (11) ◽  
pp. 1749-1757 ◽  
Author(s):  
Erika J. Eliason ◽  
Melissa Dick ◽  
David A. Patterson ◽  
Kendra A. Robinson ◽  
Jeremy Lotto ◽  
...  
Keyword(s):  
Plasma Cortisol ◽  
Sockeye Salmon ◽  
Pacific Salmon ◽  
Oncorhynchus Nerka ◽  
Field Studies ◽  
Proximate Cause ◽  
Anaerobic Energy ◽  
Lower Plasma Glucose ◽  
Prolonged Recovery ◽  
Lactate Levels

Numerous laboratory and field studies have found that female Pacific salmon have higher mortality than males during their once-in-a-lifetime upriver spawning migration. However, the proximate cause(s) of this increased mortality are poorly understood. This study exposed sockeye salmon (Oncorhynchus nerka) to a mild capture and tagging stressor and evaluated physiological recovery and movement behaviour at 1 and 4 h postrelease. Female sockeye salmon did not expend more anaerobic energy in response to the stressor but did have higher plasma lactate levels 4 h after the stressor, indicating that females took longer to physiologically recover compared with males. In addition, female salmon had lower plasma glucose but higher plasma cortisol, plasma K+, and cardiac lactate levels compared with males. Male and female salmon had markedly different postrelease behaviours within the first hour of release; males were more likely to hold position within the staging area. Two potential mechanisms leading to increased mortality in female salmon were identified in this study: (a) prolonged recovery duration (possibly mediated by elevated plasma cortisol levels) and (b) insufficient oxygen delivery to the heart.

Selection for Growth Potential among Migratory Brown Trout (Salmo trutta) Fry Competing for Territories: Evidence from Otoliths

1991 ◽  
Vol 48 (1) ◽  
pp. 19-27 ◽  
Author(s):  
Robert G. Titus ◽  
Henrik Mosegaard
Keyword(s):  
Brown Trout ◽  
Behavioral Ecology ◽  
Salmo Trutta ◽  
Growth Potential ◽  
Otolith Microstructure ◽  
Territorial Aggression ◽  
Clear Cut ◽  
Brown Trout Salmo Trutta ◽  
Selection For ◽  
Otolith Size

Otolith microstructure analysis was employed to determine differential size and growth characteristics between newly emerged migratory brown trout (Salmo trutta) fry which establish feeding territories and those which are forced to move downstream from the redd. Fry size at emergence was poorly predicted by otolith size, which precluded reliable back-calculation of fry size to investigate a possible size-selection mechanism. However, there was a clear-cut selection for individuals with significantly larger otoliths at emergence among fry which established territories in artificial stream sections. This selection pattern commenced with the onset of territorial aggression between fry. Fry which established territories to the end of the experiment had significantly higher initial otolith growth rates than emigrating fry, and their dry weights at the end of the experiment were well predicted by both otolith size at emergence and otolith size at the end of the experiment. Transparent zones in otoliths from downstream migrants suggested that these fry were starved; this was also supported by their declining dry weights over time. These results were explained as selection for greater growth potential as based on a proposed coupling between otolith microstructure formation and fish metabolism and on the behavioral ecology of migratory brown trout fry.

Egg retention in relation to arrival timing and reproductive longevity in female sockeye salmon (Oncorhynchus nerka)

2011 ◽  
Vol 68 (2) ◽  
pp. 250-259 ◽  
Author(s):  
Kimberly A. Hruska ◽  
Scott G. Hinch ◽  
David A. Patterson ◽  
Michael C. Healey
Keyword(s):  
Sockeye Salmon ◽  
Pacific Salmon ◽  
Oncorhynchus Nerka ◽  
Fork Length ◽  
Sufficient Time ◽  
Spawning Grounds ◽  
Egg Retention ◽  
Arrival Timing ◽  
Spawning Success

Some female Pacific salmon ( Oncorhynchus spp.) arrive at spawning grounds but fail to complete spawning prior to death. One hypothesis regarding egg retention is that some individuals do not have sufficient time on spawning grounds for successful completion of spawning. We investigated this hypothesis by quantifying the relationships among arrival timing, reproductive longevity, and egg retention in female sockeye salmon ( Oncorhynchus nerka ) from Weaver Creek Spawning Channel (British Columbia, Canada) in 2006. 250 females were tagged over three sampling periods and followed until death. Earlier-arriving females lived longer than later-arriving females (p < 0.001), but patterns of egg retention were not different across sampling dates (p > 0.40). Complete spawners tended to establish a redd sooner after arrival than incomplete spawners (p = 0.001); there was no relationship between spawning completion and reproductive maturity or fork length (p > 0.30). Consistent with the time limitation hypothesis, females retained a lower proportion of eggs with increasing reproductive longevity. Several long-lived females (>7 days) failed to spawn completely before death, indicating that time limitation was not a factor for spawning success in all females. Further research examining the role of individual-specific behavioural physiology on egg retention in sockeye salmon is needed.

Effect of Smolt Size on Smolt-to-Adult Survival for Chilko Lake Sockeye Salmon (Oncorhynchus nerka)

1991 ◽  
Vol 48 (6) ◽  
pp. 988-994 ◽  
Author(s):  
M. A. Henderson ◽  
A. J. Cass
Keyword(s):  
Sockeye Salmon ◽  
Interannual Variation ◽  
Oncorhynchus Nerka ◽  
Fork Length ◽  
Adult Survival ◽  
Threefold Increase ◽  
Limited Variation ◽  
Back Calculation ◽  
The Mean ◽  
Calculation Procedures

Three approaches were used to test the hypothesis that smolt-to-adult survival is independent of smolt size for Chilko Lake sockeye salmon (Oncorhynchus nerka). The mean distance between the focus of the scale and the first annulus, a reliable indicator of smolt size, was greater for adult scales than for smolt scales from the same brood year in two of the three years we examined. This indicated a higher smolt-to-adult survival for larger smolts in these brood years. The abundance of smolts of different fork lengths, based on back-calculation procedures from adult scales, was compared with the abundance of smolts of different fork lengths at the time of outmigration within brood years. In all three years studied, there was a two- to threefold increase in smolt-to-adult survival as smolt length increased. However, there was no significant relationship between smolt-to-adult survival and mean annual smolt fork length based on a 34-yr time series; this lack of relationship was probably caused by limited variation in mean annual smolt fork length over the 34-yr period and other variables, independent of smolt size, that affect survival and exhibit considerable interannual variation.

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