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Danielle M. Frechette

Bio: Danielle M. Frechette is an academic researcher from Institut national de la recherche scientifique. The author has contributed to research in topics: Predation & Population. The author has an hindex of 7, co-authored 12 publications receiving 222 citations. Previous affiliations of Danielle M. Frechette include National Marine Fisheries Service & National Oceanic and Atmospheric Administration.
Topics: Predation, Population, Fish migration, Salmo, Seabird

Papers
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Journal ArticleDOI
TL;DR: For example, adult Atlantic salmon (Salmo salar) return to natal rivers several months before spawning and during summer can be subjected to temperatures that exceed their upper temperature tolerance limits.
Abstract: Adult Atlantic salmon (Salmo salar) return to natal rivers several months before spawning and during summer can be subjected to temperatures that exceed their upper temperature tolerance limits. Sa...

53 citations

Journal ArticleDOI
TL;DR: Overall predation rates on threatened wild juvenile steelhead by generalist adult Western Gulls in six central California (USA) watersheds are estimated.
Abstract: Generalist predators can contribute to extinction risk of imperiled prey populations even through incidental predation. Quantifying predation on small populations is important to manage their recovery, however predation is often challenging to observe directly. Recovery of prey tags at predator colonies can indirectly provide minimum estimates of predation, however overall predation rates often remain unquantifiable because an unknown proportion of tags are deposited off-colony. Here, we estimated overall predation rates on threatened wild juvenile steelhead (Oncorhynchus mykiss) by generalist adult Western Gulls (Larus occidentalis) in six central California (USA) watersheds. We estimated predation rates by gulls from the recapture of PIT (passive integrated transponder) tags that were originally inserted into steelhead and were subsequently deposited at a Western Gull breeding colony, Ano Nuevo Island (ANI). We combined three independent datasets to isolate different processes: (1) the probability a tag...

50 citations

Journal ArticleDOI
TL;DR: Although steelhead contribute relatively less to overall modern gull diet, increasing gull populations and simultaneous steelhead population decline likely results in increased per capita predation risk to modern steelhead populations—the best estimate is that modern predationrisk is ~ 2.4 times higher than historically, but this estimate depends on parameter values and overlaps with zero.

35 citations

01 Jan 2011
TL;DR: In this paper, the authors developed a broadly applicable model of state-dependent movements among multiple habitats, which was parameterized based on a case study of steelhead Oncorhynchus mykiss in a California coastal watershed with a seasonally closed lagoonal estuary.
Abstract: Abstract Anadromous salmonids vary considerably in their age at ocean entry, their timing of ocean entry within a year, and the extent to which they use multiple habitat types within freshwater. To better understand habitat use and movement timing, we developed a broadly applicable model of state-dependent movements among multiple habitats, which was parameterized based on a case study of steelhead Oncorhynchus mykiss in a California coastal watershed with a seasonally closed lagoonal estuary. The model correctly predicted population-level patterns, including predominance of anadromy and a dominant smolt age of 2 years. In addition, the new model predicted the occurrence of small, lagoon-rearing fish (displaying smoltlike migratory behavior) that returned upstream and did not enter the ocean until the next year, whereas large fish emigrated from the lagoon into the ocean. The new model predicted all-or-nothing habitat use for fish of a given size, but we observed a mix of strategies for fish of the same s...

34 citations

Journal ArticleDOI
TL;DR: A broadly applicable model of state-dependent movements among multiple habitats, which was parameterized based on a case study of steelhead Oncorhynchus mykiss in a California coastal watershed with a seasonally closed lagoonal estuary, correctly predicted population-level patterns and predicted predominance of anadromy and a dominant smolt age of 2 years.
Abstract: Anadromous salmonids vary considerably in their age at ocean entry, their timing of ocean entry within a year, and the extent to which they use multiple habitat types within freshwater. To better understand habitat use and movement timing, we developed a broadly applicable model of state-dependent movements among multiple habitats, which was parameterized based on a case study of steelhead Oncorhynchus mykiss in a California coastal watershed with a seasonally closed lagoonal estuary. The model correctly predicted population-level patterns, including predominance of anadromy and a dominant smolt age of 2 years. In addition, the new model predicted the occurrence of small, lagoon-rearing fish (displaying smoltlike migratory behavior) that returned upstream and did not enter the ocean until the next year, whereas large fish emigrated from the lagoon into the ocean. The new model predicted all-or-nothing habitat use for fish of a given size, but we observed a mix of strategies for fish of the same s...

32 citations


Cited by
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Journal ArticleDOI
TL;DR: Information is synthesized to better understand genetic and environmental influences on O. mykiss life histories, identify critical knowledge gaps, and suggest next steps in anadromy and residency.
Abstract: Oncorhynchus mykiss form partially migratory populations with anadromous fish that undergo marine migrations and residents that complete their life cycle in fresh water. Many populations’ anadromou...

190 citations

Journal ArticleDOI
TL;DR: This study provides evidence that life-history diversity can dampen fluctuations in population abundances and biomass via portfolio effects, and examines steelhead in two large watersheds in north-western British Columbia, Canada.
Abstract: Summary 1. Life-history strategies can buffer individuals and populations from environmental variability. For instance, it is possible that asynchronous dynamics among different life histories can stabilize populations through portfolio effects. 2. Here, we examine life-history diversity and its importance to stability for an iconic migratory fish species. In particular, we examined steelhead (Oncorhynchus mykiss), an anadromous and iteroparous salmonid, in two large, relatively pristine, watersheds, the Skeena and Nass, in north-western British Columbia, Canada. We synthesized life-history information derived from scales collected from adult steelhead (N = 7227) in these watersheds across a decade. 3. These migratory fishes expressed 36 different manifestations of the anadromous life-history strategy, with 16 different combinations of freshwater and marine ages, 7! 6% of fish performing multiple spawning migrations, and up to a maximum of four spawning migrations per lifetime. Furthermore, in the Nass watershed, various life histories were differently prevalent through time ‐ three different life histories were the most prevalent in a given year, and no life history ever represented more than 45% of the population. 4. These asynchronous dynamics among life histories decreased the variability of numerical abundance and biomass of the aggregated population so that it was > 20% more stable than the stability of the weighted average of specific life histories: evidence of a substantial portfolio effect. Year of ocean entry was a key driver of dynamics; the median correlation coefficient of abundance of life histories that entered the ocean the same year was 2! 5 times higher than the median pairwise coefficient of life histories that entered the ocean at different times. Simulations illustrated how different elements of life-history diversity contribute to stability and persistence of populations. 5. This study provides evidence that life-history diversity can dampen fluctuations in population abundances and biomass via portfolio effects. Conserving genetic integrity and habitat diversity in these and other large watersheds can enable a diversity of life histories that increases population and biomass stability in the face of environmental variability.

149 citations

Journal ArticleDOI
TL;DR: Evidence is presented that changes in gene expression may be predictive of some of the freshwater migration mortality in wild salmonid smolts, the first evidence to link physiological responses and pathogen presence with subsequent fate during migration of wild salmonids.
Abstract: We present the first data to link physiological responses and pathogen presence with subsequent fate during migration of wild salmonid smolts. We tagged and non-lethally sampled gill tissue from sockeye salmon (Oncorhynchus nerka) smolts as they left their nursery lake (Chilko Lake, BC, Canada) to compare gene expression profiles and freshwater pathogen loads with migration success over the first ~1150 km of their migration to the North Pacific Ocean using acoustic telemetry. Fifteen per cent of smolts were never detected again after release, and these fish had gene expression profiles consistent with an immune response to one or more viral pathogens compared with fish that survived their freshwater migration. Among the significantly upregulated genes of the fish that were never detected postrelease were MX (interferon-induced GTP-binding protein Mx) and STAT1 (signal transducer and activator of transcription 1-alpha/beta), which are characteristic of a type I interferon response to viral pathogens. The most commonly detected pathogen in the smolts leaving the nursery lake was infectious haematopoietic necrosis virus (IHNV). Collectively, these data show that some of the fish assumed to have died after leaving the nursery lake appeared to be responding to one or more viral pathogens and had elevated stress levels that could have contributed to some of the mortality shortly after release. We present the first evidence that changes in gene expression may be predictive of some of the freshwater migration mortality in wild salmonid smolts.

91 citations

Journal ArticleDOI
TL;DR: This work uses acoustic telemetry to track migration behaviour and survival of juvenile sockeye salmon smolts released over a wide range of conspecific outmigration densities in a river associated with poor survival and demonstrates thatsmolts largely employ swamping of predators to reduce predation risk.
Abstract: Animal migrations are costly and are often characterized by high predation risk for individuals. Three of the most oft-assumed mechanisms for reducing risk for migrants are swamping predators with high densities, specific timing of migrations and increased body size. Assessing the relative importance of these mechanisms in reducing predation risk particularly for migrants is generally lacking due to the difficulties in tracking the fate of individuals and population-level characteristics simultaneously. We used acoustic telemetry to track migration behaviour and survival of juvenile sockeye salmon (Oncorhynchus nerka) smolts released over a wide range of conspecific outmigration densities in a river associated with poor survival. The landscape was indeed high risk; smolt survival was poor (˜68%) over 13·5 km of river examined even though migration was rapid (generally <48 h). Our results demonstrate that smolts largely employ swamping of predators to reduce predation risk. Increased densities of co-migrant conspecifics dramatically improved survival of smolts. The strong propensity for nocturnal migration resulted in smolts pausing downstream movements until the next nightfall, greatly increasing relative migration durations for smolts that could not traverse the study area in a single night. Smolt size did not appear to impact predation risk, potentially due to unique characteristics of the system or our inability to tag the entire size range of outmigrants. Movement behaviours were important in traversing this high-risk landscape and provide rare evidence for swamping to effectively reduce individual predation risk.

86 citations