scholarly journals Quantifying the Net Benefits of Suppression: Truncated Size Structure and Consumption of Native Salmonids by Invasive Northern Pike in an Alaska Lake

2018 ◽  
Vol 38 (6) ◽  
pp. 1306-1315 ◽  
Author(s):  
Michael B. Courtney ◽  
Erik R. Schoen ◽  
Andy Wizik ◽  
Peter A. H. Westley
Keyword(s):  
Size Structure ◽  
Northern Pike ◽  
Net Benefits ◽  
Native Salmonids

Do Higher Size and Reduced Bag Limits Improve Northern Pike Size Structure in Wisconsin Lakes?

2016 ◽  
Vol 36 (5) ◽  
pp. 982-994 ◽  
Author(s):  
Daniel L. Oele ◽  
Andrew L. Rypel ◽  
John Lyons ◽  
Paul Cunningham ◽  
Tim Simonson
Keyword(s):  
Size Structure ◽  
Northern Pike

scholarly journals Warmer water increases early body growth of northern pike (Esox lucius) but mortality has larger impact on decreasing body sizes

2021 ◽  
Author(s):  
Terese Berggren ◽  
Ulf Bergström ◽  
Göran Sundblad ◽  
Örjan Östman
Keyword(s):  
Size Structure ◽  
Northern Pike ◽  
Body Growth ◽  
Size Distributions ◽  
Age Classes ◽  
The Baltic Sea ◽  
Mortality Pattern ◽  
Body Sizes ◽  
The Baltic ◽  
Slow Growing

Large fish species often display truncated size distributions related to harvest. In addition, temperature, food availability and density-dependence affect body growth, and together with natural mortality influence population size structure. Here we study changes in body growth, size distributions and mortality in both harvested and non-harvested populations of northern pike over 50 years along the Baltic Sea coast and in Lake Mälaren, Sweden. For coastal pike, body growth has increased coincidentally with increasing water temperatures, yet in the last two decades there has been a decrease of larger individuals. In Lake Mälaren, in contrast, size distributions and body growth were stationary despite similar increases in water temperature. A dominance of slow-growing individuals in older age-classes was evident in all studied populations, also in the no-take zone, suggesting other factors than fishing contribute to the mortality pattern. We propose that increasing temperatures have favoured body growth in coastal areas, but this has been counteracted by increased mortality, causing pike sizes to decline. To regain larger coastal pike, managers need to consider multiple measures that reduce mortality.

Vulnerability to harvest by anglers differs across climate, productivity, and diversity clines

2014 ◽  
Vol 71 (3) ◽  
pp. 416-426 ◽  
Author(s):  
Stephanie Mogensen ◽  
John R. Post ◽  
Michael G. Sullivan
Keyword(s):  
New York ◽  
Size Structure ◽  
Northern Pike ◽  
Community Diversity ◽  
Fish Diversity ◽  
Recreational Fisheries ◽  
Degree Days ◽  
Catch And Release ◽  
Oneida Lake ◽  
Proximate Causes

We contrast catchability of walleye (Sander vitreus) and northern pike (Esox lucius) populations with angling fisheries across regions that differ twofold in growing-degree-days and productivity and sixfold in fish diversity. Populations of both species in Alberta, Wisconsin, Minnesota, and Oneida Lake, New York, had density-dependent catchability with approximately tenfold higher catchability in Alberta than in the other regions when density was controlled for. There is no evidence that the higher catchability estimates for Alberta walleye and northern pike are due to differential spatial distributions, enhanced hook avoidance due to catch and release or to differential size structure of the populations, or to differences in harvest regulations. We argue that the most likely explanation for the tenfold higher catchability is increased hunger resulting in enhanced foraging activity in the region with a substantially shorter growing season, lower prey productivity, and lower prey community diversity. Regardless of the proximate causes, higher catchability of fish harvested in recreational fisheries in Alberta substantially increases their vulnerability to overharvest and collapse if angling effort is unabated.

Structure and composition of metal particles in Pt-Sn/Al2O3 bimetallic catalysts

1990 ◽  
Vol 48 (4) ◽  
pp. 278-279
Author(s):  
A. Sachdev ◽  
J. Schwank
Keyword(s):  
Bimetallic Catalysts ◽  
Bimetallic Catalyst ◽  
Size Structure ◽  
High Surface ◽  
High Surface Area ◽  
Metal Particles ◽  
Alloy Formation ◽  
Particle Size Range ◽  
Oxide Supports ◽  
Petroleum Fractions

Platinum - tin bimetallic catalysts have been primarily utilized in the chemical industry in the catalytic reforming of petroleum fractions. In this process the naphtha feedstock is converted to hydrocarbons with higher octane numbers and high anti-knock qualities. Most of these catalysts contain small metal particles or crystallites supported on high surface area insulating oxide supports. The determination of the structure and composition of these particles is crucial to the understanding of the catalytic behavior. In a bimetallic catalyst it is important to know how the two metals are distributed within the particle size range and in what way the addition of a second metal affects the size, structure and composition of the metal particles. An added complication in the Pt-Sn system is the possibility of alloy formation between the two elements for all atomic ratios.

Complete sequences of 4 viral hemorrhagic septicemia virus IVb isolates and their virulence in northern pike fry

2017 ◽  
Vol 126 (3) ◽  
pp. 211-227 ◽  
Author(s):  
RG Getchell ◽  
ER Cornwell ◽  
S Bogdanowicz ◽  
J Andrés ◽  
WN Batts ◽  
...  
Keyword(s):  
Northern Pike ◽  
Viral Hemorrhagic Septicemia Virus ◽  
Viral Hemorrhagic Septicemia ◽  
Complete Sequences

Effects of marine reserves on predator-prey interactions in central California kelp forests

2020 ◽  
Vol 655 ◽  
pp. 139-155
Author(s):  
DC Yates ◽  
SI Lonhart ◽  
SL Hamilton
Keyword(s):  
Species Interactions ◽  
Size Structure ◽  
Marine Reserves ◽  
Mortality Rates ◽  
Kelp Forests ◽  
Negative Effects ◽  
Central California ◽  
Invertebrate Predators ◽  
Predatory Fishes ◽  
Density And Biomass

Marine reserves are often designed to increase density, biomass, size structure, and biodiversity by prohibiting extractive activities. However, the recovery of predators following the establishment of marine reserves and the consequent cessation of fishing may have indirect negative effects on prey populations by increasing prey mortality. We coupled field surveys with empirical predation assays (i.e. tethering experiments) inside and outside of 3 no-take marine reserves in kelp forests along the central California coast to quantify the strength of interactions between predatory fishes and their crustacean prey. Results indicated elevated densities and biomass of invertebrate predators inside marine reserves compared to nearby fished sites, but no significant differences in prey densities. The increased abundance of predators inside marine reserves translated to a significant increase in mortality of 2 species of decapod crustaceans, the dock shrimp Pandalus danae and the cryptic kelp crab Pugettia richii, in tethering experiments. Shrimp mortality rates were 4.6 times greater, while crab mortality rates were 7 times greater inside reserves. For both prey species, the time to 50% mortality was negatively associated with the density and biomass of invertebrate predators (i.e. higher mortality rates where predators were more abundant). Video analyses indicated that macro-invertivore fishes arrived 2 times faster to tethering arrays at sites inside marine reserves and began attacking tethered prey more rapidly. The results indicate that marine reserves can have direct and indirect effects on predators and their prey, respectively, and highlight the importance of considering species interactions in making management decisions.

Persistence of giants: population dynamics of the limpet Scutellastra laticostata on rocky shores in Western Australia

2020 ◽  
Vol 646 ◽  
pp. 79-92
Author(s):  
RE Scheibling ◽  
R Black
Keyword(s):  
Population Dynamics ◽  
Western Australia ◽  
Size Structure ◽  
Survival Rates ◽  
Maximum Size ◽  
High Rate ◽  
Adult Survival ◽  
Rocky Shores ◽  
Adult Size ◽  
Decadal Time Scale

Population dynamics and life history traits of the ‘giant’ limpet Scutellastra laticostata on intertidal limestone platforms at Rottnest Island, Western Australia, were recorded by interannual (January/February) monitoring of limpet density and size structure, and relocation of marked individuals, at 3 locations over periods of 13-16 yr between 1993 and 2020. Limpet densities ranged from 4 to 9 ind. m-2 on wave-swept seaward margins of platforms at 2 locations and on a rocky notch at the landward margin of the platform at a third. Juvenile recruits (25-55 mm shell length) were present each year, usually at low densities (<1 m-2), but localized pulses of recruitment occurred in some years. Annual survival rates of marked limpets varied among sites and cohorts, ranging from 0.42 yr-1 at the notch to 0.79 and 0.87 yr-1 on the platforms. A mass mortality of limpets on the platforms occurred in 2003, likely mediated by thermal stress during daytime low tides, coincident with high air temperatures and calm seas. Juveniles grew rapidly to adult size within 2 yr. Asymptotic size (L∞, von Bertalanffy growth model) ranged from 89 to 97 mm, and maximum size from 100 to 113 mm, on platforms. Growth rate and maximum size were lower on the notch. Our empirical observations and simulation models suggest that these populations are relatively stable on a decadal time scale. The frequency and magnitude of recruitment pulses and high rate of adult survival provide considerable inertia, enabling persistence of these populations in the face of sporadic climatic extremes.

On Measuring the Social Opportunity Cost of Labour in the Presence of Tariffs and an Informal Sector (The Distinguishedl Lecture)

1992 ◽  
Vol 31 (4I) ◽  
pp. 535-564 ◽  
Author(s):  
M. Ali Khan
Keyword(s):  
Informal Sector ◽  
Opportunity Cost ◽  
Costs And Benefits ◽  
Open Letter ◽  
Review Of The Literature ◽  
The Social ◽  
Action Project ◽  
Relevant Group ◽  
Net Benefits ◽  
The Individual

Harberger introduced his influential 1971 essay with the following words. This paper is intended not as a scientific study, nor as a review of the literature, but rather as a tract - an open letter to the profession, as it were - pleading that three basic postulates be accepted as providing a conventional framework for applied welfare economics. The postulates are: (a) The competitive demand price for a given unit measures the value of that unit to the demander; (b) The competitive supply price for a given unit measures the value of that unit to the supplier; and (c) When evaluating the net benefits or costs of a given action (project, programme, or policy), the costs and benefits accruing to each member of the relevant group (e.g., a nation) should normally be added without regard to the individual(s) to whom they accrue.

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