Andrew Murdoch - Academia.edu (original) (raw)

Papers by Andrew Murdoch

Canadian Journal of Fisheries and Aquatic Sciences, 2010

Understanding the relative fitness of naturally spawning hatchery fish compared with wild fish ha... more Understanding the relative fitness of naturally spawning hatchery fish compared with wild fish has become an important issue in the management and conservation of salmonids. We used a DNA-based parentage analysis to measure the relative reproductive success of hatchery- and natural-origin spring Chinook salmon ( Oncorhynchus tshawytscha ) in the natural environment. Size and age had a large influence on male fitness, with larger and older males producing more offspring than smaller or younger individuals. Size had a significant effect on female fitness, but the effect was smaller than on male fitness. For both sexes, run time had a smaller but still significant effect on fitness, with earlier returning fish favored. Spawning location within the river had a significant effect on fitness for both sexes. Hatchery-origin fish produced about half the juvenile progeny per parent when spawning naturally than did natural-origin fish. Hatchery fish tended to be younger and return to lower ar...

Conservation Science and Practice

The primary conservation prioritization tool for spring Chinook Salmon (Oncorhynchus tshawytscha)... more The primary conservation prioritization tool for spring Chinook Salmon (Oncorhynchus tshawytscha), population viability analysis, is often conducted with biased spawner abundance data with no associated statistical uncertainty or error. This study estimated observation error of surveyors counting redds in two spring Chinook Salmon populations where hatchery supplementation is implemented as a conservation tool. Habitat complexity, redd density and the amount of observer experience were important in estimating error rates. Increases in both habitat complexity and experience reduced net error rates. Conversely, net error rates increased as redd density increased. Unbiased estimates of redd abundance were generated and converted to spawner abundance using population specific redd expansion factors. The precision (i.e., coefficient of variation [CV]) of spawner abundance estimates were similar in the Wenatchee (natural CV = 5%; hatchery CV = 6%) and Methow (natural CV = 5%; hatchery CV = 2%) watersheds because average net error rates were similar (Wenatchee = −0.1512; Methow = −0.1748). This study addresses a criticism of population viability analysis (i.e., parameter uncertainty) that should result in more scientifically defensible conservation priorities and recommendations that can be implemented with greater certainty.

Canadian Journal of Fisheries and Aquatic Sciences

This study examined how a suite of habitat and environmental variables relate to the ability of a... more This study examined how a suite of habitat and environmental variables relate to the ability of a stream surveyor to identify (observer efficiency) and distinguish (observer accuracy) steelhead (Oncorhynchus mykiss) redds from other stream features. Two existing spawning survey protocols that included one or two redd observers were used to develop models to estimate redd observer error. In most cases, steelhead redd abundances using raw redd counts were underestimated. Mean annual rates of observer efficiency ranged from 0.44 to 0.57, and observer accuracy ranged from 0.67 to 0.83. Regardless of the observer error model used, adjusted annual redd abundance estimates were generally unbiased (range 1.6–0.6 redds). A Gaussian area-under-the-curve methodology that incorporates redd count data and observer error rates was used to generate unbiased estimates of steelhead redd abundance in the Wenatchee (170 redds, coefficient of variation (CV) = 44%) and Methow (106 redds, CV = 41%) river...

Transactions of the American Fisheries Society

PloS one, 2016

We used genetic parentage analysis of 6200 potential parents and 5497 juvenile offspring to evalu... more We used genetic parentage analysis of 6200 potential parents and 5497 juvenile offspring to evaluate the relative reproductive success of hatchery and natural steelhead (Onchorhynchus mykiss) when spawning in the wild between 2008 and 2011 in the Wenatchee River, Washington. Hatchery fish originating from two prior generation hatchery parents had <20% of the reproductive success of natural origin spawners. In contrast, hatchery females originating from a cross between two natural origin parents of the prior generation had equivalent or better reproductive success than natural origin females. Males originating from such a cross had reproductive success of 26-93% that of natural males. The reproductive success of hatchery females and males from crosses consisting of one natural origin fish and one hatchery origin fish was 24-54% that of natural fish. The strong influence of hatchery broodstock origin on reproductive success confirms similar results from a previous study of a differ...

North American Journal of Fisheries Management, Oct 10, 2013

ABSTRACT We classified juvenile hatchery summer steelhead Oncorhynchus mykiss released from Wells... more ABSTRACT We classified juvenile hatchery summer steelhead Oncorhynchus mykiss released from Wells Hatchery, Washington, from three brood years (2002–2004) as those that migrated volitionally (VM) from rearing ponds or as those that were forced out of rearing ponds after volitional migration concluded (NM). Fish were implanted with PIT tags prior to release and we used recreational angling equipment to recapture tagged fish to estimate the relative contribution rates of VM and NM release groups to the stream-resident population of juvenile hatchery summer steelhead in the Twisp River. We also evaluated the survival for each group from release to McNary Dam, and from release to adult return (SAR) at Bonneville and Wells dams on the Columbia River. Overall, we estimated that 82% of stream-resident hatchery juvenile summer steelhead originated from releases of NM fish. The probability of survival from release to McNary Dam was significantly greater for VM groups (mean, 0.4817; SE, 0.023) than for NM groups (mean, 0.2182; SE, 0.021) within each year. The mean SAR to Bonneville and Wells dams was 1.54% and 1.26%, respectively, for VM fish and 0.37% and 0.32%, respectively, for NM fish; the differences were significant between groups within each year. As an index of release strategy performance, VM releases resulted in one stream-resident fish recaptured for every 7.8 adults returned, while NM releases produced one stream-resident fish recaptured for every 0.48 adults returned. These results suggest that managers employ a volitional release strategy to significantly reduce the abundance of stream-resident juvenile hatchery steelhead by not releasing NM fish into waters inhabited by anadromous fishes, thereby reducing negative ecological interactions between hatchery residual steelhead and wild salmonids at little cost to adult returns.Received February 25, 2013; accepted July 8, 2013

North American Journal of Aquaculture, 2015

Transactions of the American Fisheries Society, Apr 22, 2015

ABSTRACT Hatchery propagation of spring Chinook Salmon Oncorhynchus tshawytscha has been shown to... more ABSTRACT Hatchery propagation of spring Chinook Salmon Oncorhynchus tshawytscha has been shown to increase the proportion of males maturing as minijacks (age 2) or microjacks (age 1) relative to those proportions in wild populations. However, little is known about the success of early maturing males when they spawn in the wild. A captive broodstock program for spring Chinook Salmon in the White River (a tributary of the Wenatchee River, Washington) has a high rate of early male maturity. We used genetic parentage analysis to evaluate the spawning success of anadromous males in comparison with inferred early maturing resident, hatchery-origin males that spawned naturally. Based on samples of juvenile offspring (n = 1,007-1,368 fish/year) and a nearly complete sample of the potential anadromous parents, we found that during 2006-2009, 26-45% of the progeny did not have a male parent in the anadromous sample. In contrast, 0-23% of the progeny did not have a female parent represented in the sample. Using grandparentage analysis, we eliminated wild resident fish as a likely source of the unsampled male parents; thus, we concluded that those male parents were most likely early maturing resident fish that had been released from the captive broodstock program. The inferred spawning success of the unsampled resident males was significantly lower than that of the anadromous males. The typical mating pattern was for an anadromous female to produce about two-thirds of her offspring with one or two anadromous males and the remaining one-third with as many as 12 or more apparently resident males. To our knowledge, this is the first study to present evidence of successful reproduction by early maturing resident, hatchery-origin Chinook Salmon in the wild. The conservation implications of this finding are complex and will depend upon the genetic basis of early maturity and its causes in hatchery settings.

North American Journal of Fisheries Management, 2015

Hatchery propagation can lead to marked changes in the age at maturity of propagated species, typ... more Hatchery propagation can lead to marked changes in the age at maturity of propagated species, typically with a shift toward maturity at younger ages. Understanding the mechanisms and consequences of a shift toward earlier maturity is important for evaluating the effects of hatchery supplementation on wild salmon populations. Whole population pedigree analysis is a powerful tool for evaluating the genetic basis of variation in age-at-maturity and its micro-evolutionary consequences. Here, we report on the effect of male spawning age on male fitness in Wenatchee River spring Chinook salmon in both wild and hatchery environments. By using a 2+ generation pedigree, we can evaluate both the relative fitness of hatchery produced fish that return to spawn in the wild environment at a variety of ages and the heritability of variation in male age at maturity in both hatchery and wild environments.

Spring Chinook salmon Oncorhynchus tshawytscha typically spawn in smaller tributaries within a wa... more Spring Chinook salmon Oncorhynchus tshawytscha typically spawn in smaller tributaries within a watershed compared to other races of Chinook. Spring Chinook are considered “stream type” Chinook that reside in freshwater for a period of up to 15 months before migrating to the ocean. After emergence from the gravel, juvenile spring Chinook may emigrate from their natal stream to a larger river at any time during their 15 months in freshwater. Annual variation in the magnitude of these migrations confound comparisons of abundance across years because fish may emigrate from their natal stream at various life stages. Hence, an estimate of abundance at the smolt stage is not possible. The Chiwawa River is the single largest spring Chinook spawning tributary in the Wenatchee Basin. Juvenile abundance monitoring by means of rotary smolt trapping and snorkel surveys and adult monitoring via census redd counts have been ongoing since 1993 and 1990, respectively. Abundance estimates produced fr...

Transactions of the American Fisheries Society, 2015

Molecular ecology, 2015

We used parentage analysis based on microsatellite genotypes to measure rates of homing and stray... more We used parentage analysis based on microsatellite genotypes to measure rates of homing and straying of Chinook salmon (Oncorhynchus tshawytscha) among five major spawning tributaries within the Wenatchee River, Washington. On the basis of analysis of 2248 natural-origin and 11594 hatchery-origin fish, we estimated that the rate of homing to natal tributaries by natural-origin fish ranged from 0% to 99% depending on the tributary. Hatchery-origin fish released in one of the five tributaries homed to that tributary at a far lower rate than the natural-origin fish (71% compared to 96%). For hatchery-released fish, stray rates based on parentage analysis were consistent with rates estimated using physical tag recoveries. Stray rates among major spawning tributaries were generally higher than stray rates of tagged fish to areas outside of the Wenatchee River watershed. Within the Wenatchee watershed, rates of straying by natural-origin fish were significantly affected by spawning tribut...

North American Journal of Fisheries Management, 2009

ABSTRACT Artificial propagation of sockeye salmon Oncorhynchus nerka interrupts the early phases ... more ABSTRACT Artificial propagation of sockeye salmon Oncorhynchus nerka interrupts the early phases of their life history cycle, typically between the egg and smolt stages. Sockeye salmon reared initially in a hatchery and subsequently released as parr from freshwater net-pens suspended in a lake cannot imprint on a specific tributary water source. As a result, the spawning distribution of returning adults may differ from that of naturally produced fish. We used radio tags and carcass surveys to determine whether the spawning distribution and location of adult hatchery sockeye salmon reared and released from net-pens in Lake Wenatchee, Washington, were similar to the spawning distribution and location of their naturally produced counterparts. Over 2 years, 100 hatchery sockeye salmon were radio-tagged and tracked to their spawning location. No radio-tagged sockeye salmon were found spawning in Lake Wenatchee, the lake outlet, or other nearby rivers. All radio-tagged sockeye salmon that were tracked into tributaries of Lake Wenatchee spawned in locations (i.e., river reaches) similar to those of naturally produced fish. Based on carcass surveys, the spawning distribution of hatchery sockeye salmon among spawning tributaries was different from that of naturally produced fish; this difference was attributed to the inability of hatchery fish to imprint on a natal stream during their early life history. Although the spawning distribution among tributaries differed between hatchery and naturally produced fish, the mean difference was small (10.8%) and ranged between 0% and 29%.

North American Journal of Fisheries Management, 2013

Conservation Letters, 2012

ABSTRACT Adaptation of plants or animals to captivity is a risk associated with any captive breed... more ABSTRACT Adaptation of plants or animals to captivity is a risk associated with any captive breeding program that has the intent of returning organisms to the wild. The risk is particularly acute for species that are captively bred and released on a large scale, as is the case for many species of fish. Several studies, particularly in salmonids, have reported rapid adaptation of populations to captivity, but the mechanisms of such adaptations are not always clear. We evaluated a large three-generation pedigree of an artificially supplemented salmon population, and found that the fish with the highest reproductive success in captivity produce early maturing male offspring that have lower than average reproductive success in the wild. In contrast to an earlier study of steelhead trout, we found little evidence that parental origin of the captive spawners influenced the subsequent reproductive success of their naturally spawning progeny.

Ecological risks of Pacific salmon (spring, summer, and fall run Chinook, coho, and sockeye salmo... more Ecological risks of Pacific salmon (spring, summer, and fall run Chinook, coho, and sockeye salmon) and steelhead trout hatchery programs operated between 2013 and 2023 in the Upper Columbia Watershed will be assessed using Delphi and modeling approaches. Committees composed of resource managers and public utility districts identified non-target taxa of concern (i.e., taxa that are not the target of supplementation), and acceptable hatchery impacts (i.e., change in population status) to those taxa. Biologists assembled information about hatchery programs, non-target taxa, and ecological interactions and this information will be provided to expert panelists in the Delphi process to facilitate assessment of risks and also used to populate the Predation, Competition, and Disease (PCD) Risk 1 model. Delphi panelists will independently estimate the proportion of a non-target taxa population that will be affected by each individual hatchery program. Estimates from each of the two approaches will be independently averaged, a measure of dispersion calculated (e.g., standard deviation), and subsequently compared to the acceptable hatchery impact levels that were determined previously by committees of resource managers and public utility districts. Measures of dispersion will be used to estimate the scientific uncertainty associated with risk estimates. Delphi