Daily incuremtns in Otoliths of juvenile Snapper, Pagrus auratus (Sparidae)

1992 ◽  
Vol 43 (5) ◽  
pp. 1015 ◽  
Author(s):  
MP Francis ◽  
MW Williams ◽  
AC Pryce ◽  
S Pollard ◽  
SG Scott
Keyword(s):  
Population Dynamics ◽  
New Zealand ◽  
Light Microscope ◽  
Wild Population ◽  
Larval Period ◽  
Increment Width ◽  
Daily Increment ◽  
Daily Increments ◽  
Pagrus Auratus ◽  
Increment Formation

Sagitta microstructure was investigated in juvenile New Zealand snapper, Pagrus auratus, to provide a basis for daily ageing in population dynamics studies. Transverse sections produced the clearest daily increments and were the easiest to prepare. Daily increment formation was validated up to an age of 100 days by using increment counts from reared juveniles and up to about 160 days by using changes in mean increment counts from juveniles sampled from a wild population at different times. A prominent metamorphic mark was visible in transverse and frontal sections, providing a means for determining the duration of the larval period, and juvenile postmetamorphic ages. Postmetamorphic increment width varied with the age of the snapper and with season. Increment width dropped below 0.5 μm in winter and increments could not be resolved with a light microscope.

New Zealand translocations: theory and practice

1995 ◽  
Vol 2 (1) ◽  
pp. 39 ◽  
Author(s):  
Doug P. Armstong ◽  
Ian G. McLean
Keyword(s):  
Population Dynamics ◽  
New Zealand ◽  
Experimental Tests ◽  
Theory And Practice ◽  
Habitat Requirements ◽  
Metapopulation Dynamics ◽  
Behavioural Adaptation ◽  
New Locations ◽  
History Of ◽  
Tests Of Hypotheses

One of the most common tools in New Zealand conservation is to translocate species to new locations. There have now been over 400 translocations done for conservation reasons, mainly involving terrestrial birds. Most translocations have been done strictly as management exercises, with little or no reference to theory. Nevertheless, translocations always involve some underlying theory, given that people must inevitably choose among a range of potential translocation strategies. We review theory relevant to translocations in the following areas: habitat requirements, susceptibility to predation, behavioural adaptation, population dynamics, genetics, metapopulation dynamics, and community ecology. For each area we review and evaluate the models that seem to underpin translocation strategies used in New Zealand. We report experiments testing some of these models, but note that theory underlying translocation strategies is largely untested despite a long history of translocations. We conclude by suggesting key areas for research, both theoretical and empirical. We particularly recommend that translocations be designed as experimental tests of hypotheses whenever possible.

scholarly journals Separating the effects of climate, bycatch, predation and harvesting on tītī (Ardenna grisea) population dynamics in New Zealand: A model-based assessment

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0243794
Author(s):  
Sam McKechnie ◽  
David Fletcher ◽  
Jamie Newman ◽  
Corey Bragg ◽  
Peter W. Dillingham ◽  
...  
Keyword(s):  
Population Dynamics ◽  
New Zealand ◽  
Southern Oscillation ◽  
Population Decline ◽  
Management Strategies ◽  
Model Averaging ◽  
Adult Survival ◽  
Enso Events ◽  
Introduced Predators ◽  
Best Fitting

A suite of factors may have contributed to declines in the tītī (sooty shearwater; Ardenna grisea) population in the New Zealand region since at least the 1960s. Recent estimation of the magnitude of most sources of non-natural mortality has presented the opportunity to quantitatively assess the relative importance of these factors. We fit a range of population dynamics models to a time-series of relative abundance data from 1976 until 2005, with the various sources of mortality being modelled at the appropriate part of the life-cycle. We present estimates of effects obtained from the best-fitting model and using model averaging. The best-fitting models explained much of the variation in the abundance index when survival and fecundity were linked to the Southern Oscillation Index, with strong decreases in adult survival, juvenile survival and fecundity being related to El Niño-Southern Oscillation (ENSO) events. Predation by introduced animals, harvesting by humans, and bycatch in fisheries also appear to have contributed to the population decline. It is envisioned that the best-fitting models will form the basis for quantitative assessments of competing management strategies. Our analysis suggests that sustainability of the New Zealand tītī population will be most influenced by climate, in particular by how climate change will affect the frequency and intensity of ENSO events in the future. Removal of the effects of both depredation by introduced predators and harvesting by humans is likely to have fewer benefits for the population than alleviating climate effects.

scholarly journals Faecal Microbiota of Forage-Fed Horses in New Zealand and the Population Dynamics of Microbial Communities following Dietary Change

PLoS ONE ◽  
2014 ◽  
Vol 9 (11) ◽  
pp. e112846 ◽  
Author(s):  
Karlette A. Fernandes ◽  
Sandra Kittelmann ◽  
Christopher W. Rogers ◽  
Erica K. Gee ◽  
Charlotte F. Bolwell ◽  
...  
Keyword(s):  
Population Dynamics ◽  
New Zealand ◽  
Microbial Communities ◽  
Dietary Change ◽  
Faecal Microbiota

A simple model for ferret population dynamics and control in semi-arid New Zealand habitats

2001 ◽  
Vol 28 (1) ◽  
pp. 87 ◽  
Author(s):  
N. D. Barlow ◽  
G. L. Norbury
Keyword(s):  
Population Dynamics ◽  
New Zealand ◽  
Current Density ◽  
Average Density ◽  
Intrinsic Rate Of Increase ◽  
Data Sets ◽  
Data Set ◽  
Rate Of Increase ◽  
Semi Arid ◽  
Over Time

Introduced ferrets (Mustela furo) in New Zealand are subject to population control to reduce their threat to native fauna and the incidence of bovine tuberculosis (Tb) in livestock. To help in evaluating control options and to contribute to a multi-species model for Tb dynamics, a simple Ricker model was developed for ferret population dynamics in a semi-arid environment. The model was based on two data sets and suggested an intrinsic rate of increase for ferrets of 1.0–1.3 year–1 and a carrying capacity of 0.5–2.9 km–2. There was evidence for direct density-dependence in both data sets and the effect appeared to act mainly on recruitment. Dependence of the rate of increase of predators on the density of wild rabbits (Oryctolagus cuniculus) was exhibited in one of the two data sets, together with a numerical response relating current density of predators asymptotically to current density of rabbits, their primary prey. Predators in this data set included both cats and ferrets, estimated from spotlight counts, but the other data set demonstrated a direct proportionality between predator (cat and ferret) spotlight counts and minimum ferrets known to be alive by trapping. The model suggested, firstly, that populations are hard to suppress by continuous culling, with at least a 50% removal per year necessary to effect a suppression of 50% in long-term average density. Secondly, if control is episodic rather than continuous, culling in autumn gives a greater degree of suppression over time (280%, accumulated over time) than culling in spring (180%). A differential equation version of the model provides a component for a general Anderson/May bovine Tb/wildlife (possum/deer/ferret) model.

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