Can intense predation by bears exert a depensatory effect on recruitment in a Pacific salmon population?

Written by

Can intense predation by bears exert a depensatory effect on recruitment in a Pacific salmon population?

Oecologia. 2014 Aug 26;

Authors: Quinn TP, Cunningham CJ, Randall J, Hilborn R

Abstract
It has long been recognized that, as populations increase in density, ecological processes affecting growth and survival reduce per capita recruitment in the next generation. In contrast to the evidence for such “compensatory” density dependence, the alternative “depensatory” process (reduced per capita recruitment at low density) has proven more difficult to demonstrate in the field. To test for such depensation, we measured the spawner-recruit relationship over five decades for a sockeye salmon (Oncorhynchus nerka) population in Alaska breeding in high-quality, unaltered habitat. Twenty-five years of detailed estimates of predation by brown bears, Ursus arctos, revealed strong density dependence in predation rate; the bears killed ca. 80 % of the salmon in years of low salmon spawning abundance. Nevertheless, the reconstructed spawner-recruit relationship, adjusted to include salmon intercepted in the commercial fishery, provided no evidence of demographic depensation. That is, in years when few salmon returned and the great majority were killed by bears, the few that spawned were successful enough that the population remained highly productive, even when those killed by bears were included as potential spawners. We conclude that the high quality of breeding habitat at this site and the productive nature of semelparous Pacific salmon allowed this population to avoid the hypothesized depressed recruitment from depensatory processes expected at low density. The observed lack of demographic depensation is encouraging from a conservation standpoint because it implies that depleted populations may have the potential to rebound successfully given suitable spawning and rearing habitat, even in the presence of strong predation pressure.

PMID: 25154755 [PubMed – as supplied by publisher]

via pubmed: school of aquatic an… http://ift.tt/1zDlOQX

Resource competition induces heterogeneity and can increase cohort survivorship: selection-event duration matters.

Written by

Related Articles

Resource competition induces heterogeneity and can increase cohort survivorship: selection-event duration matters.

Oecologia. 2013 Dec;173(4):1321-31

Authors: Gosselin JL, Anderson JJ

Abstract
Determining when resource competition increases survivorship can reveal processes underlying population dynamics and reinforce the importance of heterogeneity among individuals in conservation. We ran an experiment mimicking the effects of competition in a growing season on survivorship during a selection event (e.g., overwinter starvation, drought). Using a model fish species (Poecilia reticulata), we studied how food availability and competition affect mass in a treatment stage, and subsequently survivorship in a challenge stage of increased temperature and starvation. The post-treatment mean mass was strongly related to the mean time to mortality and mass at mortality at all levels of competition. However, competition increased variance in mass and extended the right tail of the survivorship curve, resulting in a greater number of individuals alive beyond a critical temporal threshold ([Formula: see text]) than without competition. To realize the benefits from previously experienced competition, the duration of the challenge ([Formula: see text]) following the competition must exceed the critical threshold [Formula: see text] (i.e., competition increases survivorship when [Formula: see text]). Furthermore, this benefit was equivalent to increasing food availability by 20 % in a group without competition in our experiment. The relationship of [Formula: see text] to treatment and challenge conditions was modeled by characterizing mortality through mass loss in terms of the stochastic rate of loss of vitality (individual’s survival capacity). In essence, when the duration of a selection event exceeds [Formula: see text], competition-induced heterogeneity buffers against mortality through overcompensation processes among individuals of a cohort. Overall, our study demonstrates an approach to quantify how early life stage heterogeneity affects survivorship.

PMID: 23912261 [PubMed – indexed for MEDLINE]

via pubmed: school of aquatic an… http://ift.tt/1mp0Lf1

Climate change poised to threaten hydrologic connectivity and endemic fishes in dryland streams.

Written by

Climate change poised to threaten hydrologic connectivity and endemic fishes in dryland streams.

Proc Natl Acad Sci U S A. 2014 Aug 18;

Authors: Jaeger KL, Olden JD, Pelland NA

Abstract
Protecting hydrologic connectivity of freshwater ecosystems is fundamental to ensuring species persistence, ecosystem integrity, and human well-being. More frequent and severe droughts associated with climate change are poised to significantly alter flow intermittence patterns and hydrologic connectivity in dryland streams of the American Southwest, with deleterious effects on highly endangered fishes. By integrating local-scale hydrologic modeling with emerging approaches in landscape ecology, we quantify fine-resolution, watershed-scale changes in habitat size, spacing, and connectance under forecasted climate change in the Verde River Basin, United States. Model simulations project annual zero-flow day frequency to increase by 27% by midcentury, with differential seasonal consequences on continuity (temporal continuity at discrete locations) and connectivity (spatial continuity within the network). A 17% increase in the frequency of stream drying events is expected throughout the network with associated increases in the duration of these events. Flowing portions of the river network will diminish between 8% and 20% in spring and early summer and become increasingly isolated by more frequent and longer stretches of dry channel fragments, thus limiting the opportunity for native fishes to access spawning habitats and seasonally available refuges. Model predictions suggest that midcentury and late century climate will reduce network-wide hydrologic connectivity for native fishes by 6-9% over the course of a year and up to 12-18% during spring spawning months. Our work quantifies climate-induced shifts in stream drying and connectivity across a large river network and demonstrates their implications for the persistence of a globally endemic fish fauna.

PMID: 25136090 [PubMed – as supplied by publisher]

via pubmed: school of aquatic an… http://ift.tt/1pdoP9o

Differential growth in estuarine and freshwater habitats indicated by plasma IGF1 concentrations and otolith chemistry in Dolly Varden Salvelinus malma.

Written by

Differential growth in estuarine and freshwater habitats indicated by plasma IGF1 concentrations and otolith chemistry in Dolly Varden Salvelinus malma.

J Fish Biol. 2014 Aug 12;

Authors: Bond MH, Beckman BR, Rohrbach L, Quinn TP

Abstract
This study employed a combination of otolith microchemistry to indicate the recent habitat use, and plasma concentrations of the hormone insulin-like growth factor 1 (IGF1) as an index of recent growth rate, to demonstrate differences in growth and habitat use by Dolly Varden Salvelinus malma occupying both freshwater and estuarine habitats in south-west Alaska. Extensive sampling in all habitats revealed that fish had higher IGF1 levels in estuarine compared to lake habitats throughout the summer, and that the growth rates in different habitats within the estuary varied seasonally. In addition, otolith microchemistry indicated differentiation in estuarine habitat use among individual S. malma throughout summer months. Although growth in the estuary was higher than in fresh water in nearly all sites and months, the benefits and use of the estuarine habitats varied on finer spatial scales. Therefore, this study further illustrates the diverse life histories of S. malma and indicates an evaluation of the benefits of marine waters needs to include sub-estuary scale habitat use.

PMID: 25131145 [PubMed – as supplied by publisher]

via pubmed: school of aquatic an… http://ift.tt/1n4SGw3

Comparative genome mapping between Chinook salmon (Oncorhynchus tshawytscha) and rainbow trout (O. mykiss) based on homologous microsatellite loci.

Written by

Related Articles

Comparative genome mapping between Chinook salmon (Oncorhynchus tshawytscha) and rainbow trout (O. mykiss) based on homologous microsatellite loci.

G3 (Bethesda). 2013 Dec;3(12):2281-8

Authors: Naish KA, Phillips RB, Brieuc MS, Newton LR, Elz AE, Park LK

Abstract
Comparative genome mapping can rapidly facilitate the transfer of DNA sequence information from a well-characterized species to one that is less described. Chromosome arm numbers are conserved between members of the teleost family Salmonidae, order Salmoniformes, permitting rapid alignment of large syntenic blocks of DNA between members of the group. However, extensive Robertsonian rearrangements after an ancestral whole-genome duplication event has resulted in different chromosome numbers across Salmonid taxa. In anticipation of the rapid application of genomic data across members of the Pacific salmon genus Oncorhynchus, we mapped the genome of Chinook salmon (O. tshawytscha) by using 361 microsatellite loci and compared linkage groups to those already derived for a well-characterized species rainbow trout (O. mykiss). The Chinook salmon female map length was 1526 cM, the male map 733 cM, and the consensus map between the two sexes was 2206 cM. The average female to male recombination ratio was 5.43 (range 1-42.8 across all pairwise marker comparisons). We detected 34 linkage groups that corresponded with all chromosome arms mapped with homologous loci in rainbow trout and inferred that 16 represented metacentric chromosomes and 18 represented acrocentric chromosomes. Up to 13 chromosomes were conserved between the two species, suggesting that their structure precedes the divergence between Chinook salmon and rainbow trout. However, marker order differed in one of these linkage groups. The remaining linkage group structures reflected independent Robertsonian chromosomal arrangements, possibly after divergence. The putative linkage group homologies presented here are expected to facilitate future DNA sequencing efforts in Chinook salmon.

PMID: 24170738 [PubMed – indexed for MEDLINE]

via pubmed: school of aquatic an… http://ift.tt/1uWxMoa

Effects of Seawalls and Piers on Fish Assemblages and Juvenile Salmon Feeding Behavior

Written by

Effects of Seawalls and Piers on Fish Assemblages and Juvenile Salmon Feeding Behavior

View full textDownload full text

Full access
DOI: 10.1080/02755947.2014.910579

Stuart H. Munscha*, Jeffery R. Cordella, Jason D. Tofta & Erin E. Morgana

pages 814-827

Publishing models and article dates explained
  • Received: 27 Dec 2013
  • Accepted: 27 Mar 2014
  • Published online: 10 Jul 2014

Abstract

Shoreline modifications, such as seawall armoring and piers, are ubiquitous along developed waterfronts worldwide, and recent research suggests that their ecological effects are primarily negative. We utilized snorkel surveys to quantify the effects of seawalls and piers on fish in nearshore habitats of an urbanized estuary in Puget Sound, Washington. We observed 17 species of fish and 4 species of crab during April–August 2012 at sites modified by seawalls and piers and at reference beach sites with minimal anthropogenic structures. Species assemblages at modified sites were significantly different from those at reference beaches. At modified sites, fish distribution and assemblage structure varied with proximity to the shade cast by piers; overall fish abundances were reduced under piers, and the greatest abundances were observed at high tides in areas directly adjacent to piers. Juvenile Pacific salmon Oncorhynchus spp. were the dominant fish species, and piers reduced their presence and feeding, indicating that areas under piers provide less-valuable habitat to salmon species. Piers may interrupt movements of juvenile salmon when they use shallow waters along shorelines to migrate from freshwater to marine habitats, as juvenile salmon tend to avoid shade under piers, especially at high tides. Our results show that shoreline modifications can alter species assemblage structure, thus potentially creating novel combinations and abundances of species, and can reduce habitat function for species that utilize these and similar habitats elsewhere.

Received December 27, 2013; accepted March 27, 2014

Evolutionary rescue in a changing world.

Written by

Evolutionary rescue in a changing world.

Trends Ecol Evol. 2014 Jul 15;

Authors: Carlson SM, Cunningham CJ, Westley PA

Abstract
Evolutionary rescue occurs when adaptive evolutionary change restores positive growth to declining populations and prevents extinction. Here we outline the diagnostic features of evolutionary rescue and distinguish this phenomenon from demographic and genetic rescue. We then synthesize the rapidly accumulating theoretical and experimental studies of evolutionary rescue, highlighting the demographic, genetic, and extrinsic factors that affect the probability of rescue. By doing so, we clarify the factors to target through management and conservation. Additionally, we identify several putative cases of evolutionary rescue in nature, but conclude that compelling evidence remains elusive. We conclude with a horizon scan of where the field might develop, highlighting areas of potential application, and suggest areas where experimental evaluation will help to evaluate theoretical predictions.

PMID: 25038023 [PubMed – as supplied by publisher]

via pubmed: school of aquatic an… http://ift.tt/1li6na6

Histopathologic alterations associated with global gene expression due to chronic dietary TCDD exposure in juvenile zebrafish.

Written by

Related Articles

Histopathologic alterations associated with global gene expression due to chronic dietary TCDD exposure in juvenile zebrafish.

PLoS One. 2014;9(7):e100910

Authors: Liu Q, Spitsbergen JM, Cariou R, Huang CY, Jiang N, Goetz G, Hutz RJ, Tonellato PJ, Carvan MJ

Abstract
The goal of this project was to investigate the effects and possible developmental disease implication of chronic dietary TCDD exposure on global gene expression anchored to histopathologic analysis in juvenile zebrafish by functional genomic, histopathologic and analytic chemistry methods. Specifically, juvenile zebrafish were fed Biodiet starter with TCDD added at 0, 0.1, 1, 10 and 100 ppb, and fish were sampled following 0, 7, 14, 28 and 42 d after initiation of the exposure. TCDD accumulated in a dose- and time-dependent manner and 100 ppb TCDD caused TCDD accumulation in female (15.49 ppb) and male (18.04 ppb) fish at 28 d post exposure. Dietary TCDD caused multiple lesions in liver, kidney, intestine and ovary of zebrafish and functional dysregulation such as depletion of glycogen in liver, retrobulbar edema, degeneration of nasal neurosensory epithelium, underdevelopment of intestine, and diminution in the fraction of ovarian follicles containing vitellogenic oocytes. Importantly, lesions in nasal epithelium and evidence of endocrine disruption based on alternatively spliced vasa transcripts are two novel and significant results of this study. Microarray gene expression analysis comparing vehicle control to dietary TCDD revealed dysregulated genes involved in pathways associated with cardiac necrosis/cell death, cardiac fibrosis, renal necrosis/cell death and liver necrosis/cell death. These baseline toxicological effects provide evidence for the potential mechanisms of developmental dysfunctions induced by TCDD and vasa as a biomarker for ovarian developmental disruption.

PMID: 24988445 [PubMed – in process]

via pubmed: school of aquatic an… http://ift.tt/1mlPaQK

Genome-wide profiling of DNA methylation and gene expression in Crassostrea gigas male gametes.

Written by

Related Articles

Genome-wide profiling of DNA methylation and gene expression in Crassostrea gigas male gametes.

Front Physiol. 2014;5:224

Authors: Olson CE, Roberts SB

Abstract
DNA methylation patterns and functions are variable across invertebrate taxa. In order to provide a better understanding of DNA methylation in the Pacific oyster (Crassostrea gigas), we characterized the genome-wide DNA methylation profile in male gamete cells using whole-genome bisulfite sequencing. RNA-Seq analysis was performed to examine the relationship between DNA methylation and transcript expression. Methylation status of over 7.6 million CpG dinucleotides was described with a majority of methylated regions occurring among intragenic regions. Overall, 15% of the CpG dinucleotides were determined to be methylated and the mitochondrial genome lacked DNA methylation. Integrative analysis of DNA methylation and RNA-Seq data revealed a positive association between methylation status, both in gene bodies and putative promoter regions, and expression. This study provides a comprehensive characterization of the distribution of DNA methylation in the oyster male gamete tissue and suggests that DNA methylation is involved in gene regulatory activity.

PMID: 24987376 [PubMed]

via pubmed: school of aquatic an… http://ift.tt/1vMZfYb

Estimating Historical Eastern North Pacific Blue Whale Catches Using Spatial Calling Patterns.

Written by

Estimating Historical Eastern North Pacific Blue Whale Catches Using Spatial Calling Patterns.

PLoS One. 2014;9(6):e98974

Authors: Monnahan CC, Branch TA, Stafford KM, Ivashchenko YV, Oleson EM

Abstract
Blue whales (Balaenoptera musculus) were exploited extensively around the world and remain endangered. In the North Pacific their population structure is unclear and current status unknown, with the exception of a well-studied eastern North Pacific (ENP) population. Despite existing abundance estimates for the ENP population, it is difficult to estimate pre-exploitation abundance levels and gauge their recovery because historical catches of the ENP population are difficult to separate from catches of other populations in the North Pacific. We collated previously unreported Soviet catches and combined these with known catches to form the most current estimates of North Pacific blue whale catches. We split these conflated catches using recorded acoustic calls from throughout the North Pacific, the knowledge that the ENP population produces a different call than blue whales in the western North Pacific (WNP). The catches were split by estimating spatiotemporal occurrence of blue whales with generalized additive models fitted to acoustic call patterns, which predict the probability a catch belonged to the ENP population based on the proportion of calls of each population recorded by latitude, longitude, and month. When applied to the conflated historical catches, which totaled 9,773, we estimate that ENP blue whale catches totaled 3,411 (95% range 2,593 to 4,114) from 1905-1971, and amounted to 35% (95% range 27% to 42%) of all catches in the North Pacific. Thus most catches in the North Pacific were for WNP blue whales, totaling 6,362 (95% range 5,659 to 7,180). The uncertainty in the acoustic data influence the results substantially more than uncertainty in catch locations and dates, but the results are fairly insensitive to the ecological assumptions made in the analysis. The results of this study provide information for future studies investigating the recovery of these populations and the impact of continuing and future sources of anthropogenic mortality.

PMID: 24892427 [PubMed – as supplied by publisher]

via pubmed: school of aquatic an… http://ift.tt/1iTDsYD