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All (21)
allee-effects (4)
code (7)
environmental-change (12)
invasive-species (4)
statistics (7)
tagging-and-telemetry (10)

Blogs

How many (over-weight) storks are there?

CJS is fast in TMB

A simple Cormack Jolly Seber model is fast in Template Model Builder
statistics
code
A popular way to estimate life-history rates, such as survival, reproduction and movement rates, is using Cormack Jolly…
Mar 10, 2023
Stephen D. Gregory

Tweedie says 'hi'

Meet Tweedie

An exploration of the Tweedie family of distributions
statistics
code
I’m working with some spatio-temporally patchy fisheries count…
Mar 7, 2023
Stephen D. Gregory

A site by species matrix representing co-occurrences

Understanding co-occurrence

A randomisation approach
statistics
code
Here, I simulate a species co-occurrence problem using only base R and R package data.table.
Feb 9, 2023
Stephen D. Gregory

Paper published

New paper: Environmental conditions modify density‐dependent salmonid recruitment: Insights into the 2016 recruitment crash in Wales

Paper published in Freshwater Biology
statistics
code
environmental-change

\(^{0}\) Formerly Salmon & Trout Research Centre, Game and Wildlife Conservation Trust, East Stoke, Wareham, Dorset BH20 6BB, UK \(^{1}\) The Centre for Environment…

Sep 4, 2020
Stephen D. Gregory

Mix that logit!

(Mixed) Logistic regression in JAGS

Fitting fixed and contrasting specifications of mixed effects logistic regression in jags using dclone
environmental-change
tagging-and-telemetry
allee-effects
invasive-species
Here is a quick post showing how to do a fixed effect logistic regression in jags, extend it to a mixed effects logistic regression and show how it can be…
May 16, 2017
Stephen D. Gregory

Paper published

New paper: Scale-dependent drivers of Atlantic salmon parr lengths

Paper published in Freshwater Biology
environmental-change
tagging-and-telemetry
New paper: scale-dependent drivers of Atlantic salmon parr lengths
Apr 17, 2017
Stephen D. Gregory

Speeding things up a bit...

Running JAGS in parallel

Examples using dclone, foreach, snow and snowfall
environmental-change
tagging-and-telemetry
allee-effects
invasive-species
Sometimes, I run…
Apr 16, 2017
Stephen D. Gregory

The fluvarium - where it all happens!

Get ready… set… go! Frome salmon smolt run 2017

Quantifying the number of migrating juvenile Atlantic salmon smolts leaving the river Frome, Dorset
environmental-change
tagging-and-telemetry
Every year, the GWCT monitors migrating juvenile Atlantic salmon (Salmo salar L.) smolts leaving the river Frome, Dorset, on their way to their…
Apr 1, 2017
Stephen D. Gregory

Ordered factors - they're everywhere!

Ordered factors and their analysis

Understanding an ordered factor and implications for their use in statistical analysis
statistics
code
What is an ordered factor?
Mar 17, 2017
Stephen D. Gregory

Least cost path to the local shop

Calculate distances along a river in R and GRASS

Least cost distances between points on a river
environmental-change
tagging-and-telemetry
invasive-species
allee-effects
Recently, I have been helping Jessica E. Marsh to develop a method of calculating distances along linear features.…
Jan 31, 2017
Stephen D. Gregory

Salmon eggs

New paper: Flow and Atlantic salmon redd distribution

Salmon redds clustered in mid-river when flow is low, with consequences for density-dependent mortality in emerging fry.
environmental-change
Our paper “The effects of flow on Atlantic salmon (Salmo salar) redd distribution in a UK chalk stream between 1980 and 2015” is out today in Ecology of Freshwater Fish!
Jan 17, 2017
Stephen D. Gregory

Time for some Zzzzs

Patterns on a parr: talk

GWCT Tuesday Research Seminar on environmental drivers of salmon parr length changes, January 2017
environmental-change
Here is a link to the Tuesday research seminar I gave to the Game and Wildlife Conservation Trust, at Fordingbridge on 24th January 2017.
Jan 17, 2017
Stephen D. Gregory

British National Grid

Coordinate conversions in R

British National Grid to latitude and longitude conversion
environmental-change
tagging-and-telemetry
allee-effects
invasive-species
Here, I present a short procedure for converting British National Grid coordinates into latitude and longitude coordinates.
Jan 7, 2017
Stephen D. Gregory

Fitting quadratic interactions in jags under Kuo & Mallik variable selection

Quadratic interaction terms fitted by Bayesian Variable Selection

Fitting quadratic interactions in jags under Kuo & Mallik variable selection
statistics
code
I was recently faced with the challenge of testing the importance of non-linear effects in a linear mixed model with fixed effect…
Dec 21, 2016
Stephen D. Gregory

A visit to the Tamar

Tamar visit

Visiting the river Tamar, Devon/Cornwall, with the Environment Agency
tagging-and-telemetry
I, together with my GWCT colleagues, was lucky enough to visit the river Tamar, on the Devon / Cornwall border in Southwest England.
Nov 22, 2016
Stephen D. Gregory

Grayling underwater

Grayling Society 40th Annual Symmposium: talk

A talk given at the Grayling Society 40th Annual Symposium
environmental-change
I recently attended the Grayling Society’s 40th Annual Symposium, held in Winchester in October 2016. I was invited to talk about the Wylye Grayling Study…
Nov 14, 2016
Stephen D. Gregory

Sea trout with tags

Estimating sea trout smolt migration risks: update

A chapter on our River Frome work in the 2nd International Sea Trout Symposium proceedings
tagging-and-telemetry
We wrote a chapter for the 2nd International Sea Trout Symposium proceedings.
Oct 14, 2016
Stephen D. Gregory

Sea trout with tags

Estimating sea trout smolt migration risks: talk

Talk to the Second IFM Tagging and Telemetry Workshop, Edinburgh 2016
tagging-and-telemetry
I gave a talk recently at the Second IFM Tagging and Telemetry Workshop, held in Edinburgh in June 2016.
Oct 14, 2016
Stephen D. Gregory

Salmon eggs

Redds in space

A study by Elinor Parry on the spawning migration of salmon returning to the River Frome
environmental-change
Elinor Parry did her MSc thesis with the GWCT Fisheries Team from February to August 2015 on the effect of flow on the distribution of salmon redds in the Frome.
Sep 1, 2016
Stephen D. Gregory

Flooding at East Stoke

Salmonids in the floods

How do salmonids cope in the floods: discuss
environmental-change
As the rate of climate change accelerates, so too does the rate at which climate-related records are surpassed. The 2015/2016 winter has gone down in history as the second wettest UK winter since…
Mar 10, 2016
Stephen D. Gregory

Sea trout with tags

Estimating sea trout smolt migration risks

Analysis code for a simple state-space model to estimate acoustically tagged sea trout migration risks
tagging-and-telemetry
statistics
code
I’m involved with a project aiming to understand brown trout (Salmo trutta L.) movements in freshwater and estuarine environments.
Jan 28, 2016
Stephen D. Gregory
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2022, Stephen D. Gregory

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